Given the enormous social and health impact of the pandemic triggered by severe acute respiratory syndrome 2 (SARS-CoV-2), the scientific community made a huge effort to provide an immediate response to the challenges posed by Coronavirus disease 2019 (COVID-19). One of the most important proteins of the virus is an enzyme, called 3CLpro or main protease, already identified as an important pharmacological target also in SARS and Middle East respiratory syndrome virus (MERS) viruses. This protein triggers the production of a whole series of enzymes necessary for the virus to carry out its replicating and infectious activities. Therefore, it is crucial to gain a deeper understanding of 3CLpro structure and function in order to effectively target this enzyme. All-atoms molecular dynamics (MD) simulations were performed to examine the different conformational behaviors of the monomeric and dimeric form of SARS-CoV-2 3CLpro apo structure, as revealed by microsecond time scale MD simulations. Our results also shed light on the conformational dynamics of the loop regions at the entry of the catalytic site. Studying, at atomic level, the characteristics of the active site and obtaining information on how the protein can interact with its substrates will allow the design of molecules able to block the enzymatic function crucial for the virus. A novel coronavirus  has been identified as the pathogen responsible for the outbreak of a severe, rapidly developing pneumonia , which has broken out in Wuhan, China, in 2019. Since then, SARS-CoV-2 has circulated globally, because of its characteristics of strong contagion and high concealment . BecauseThe active 3CLpro is a homodimer, containing two protomers. Each protomer is formed by three domains: six antiparallel β-barrels form domains I and II  and host the substrate-binding site, while domain III (residues 201–303) is a globular cluster of five helices that regulates protein dimerization. The 3CLpro possesses a Cys-His dyad, located in the cleft between domains I and II, in which the cysteine thiol functions as the nucleophile in the proteolytic process. The active site is composed of four sites .In the dimer, there exist a number of intermolecular interactions between the two protomers. Specifically, the hydrogen bonds between the N-terminus of a protomer and the domain II of another protomer that helps shaping the S1 pocket of the substrate-binding site; hence, the dimer is the catalytically active form, while the monomer is mostly inactive ,8. The dThe amino acids in substrates from the N terminus to C terminus are numbered as P1–P4 and P1’–P3’; the cleavage site resides between the P1 and P1’, with a Gln residue required in the P1 position of the substrates. The substrate recognition pockets in 3CLpro are named as S1–4, accordingly. The 3CLpro has been the target of extensive efforts in the search for potential drug leads; in this regard, structural biology plays a crucial role, considering the growing number of three-dimensional structures for 3CLpro released so far ,9,10,11.Although the available crystal structures of the 3CLpro provide important insights about atomistic protein–inhibitor interactions, they represent a portion of the possible conformations explored by the enzyme. Therefore, to shed some light on the structural-dynamical behavior of this enzyme, we performed extended all-atoms molecular dynamics (MD) simulations in the microsecond time scale. Such an extended sampling is needed when large amplitude conformational rearrangements have to be addressed ,15,16,17Herein, we investigate the conformational dynamics of SARS-CoV-2 3CLpro in its monomeric and dimeric forms. Starting from the structure of SARS-CoV-2 3CLpro, we analyze the role played by global and local chain flexibility in the catalytic mechanism. Our results highlight the role played by key residues in the enzyme catalytic pocket, which can be useful for the subsequent phases of drug discovery. In addition, we also find out that the conformational dynamics of loops in the binding pocket entrance are different in the monomeric and dimeric form of the 3CLpro, thus suggesting the importance of the inter-subunits interactions for the catalysis.Simulations were started from the X-ray coordinates deposited in the Protein Data Bank (PDB ID: 6LU7) and modified as described in the Methods section. α atoms. To this end, the root mean square deviation (RMSD) was calculated and is plotted in To sample the structural stability of the 3CLpro during the simulations, we measured the deviation of each structure from the starting crystallographic coordinates after a superposition on the protein CThe residue-based root mean square fluctuation (RMSF) in the trajectory was calculated to measure the flexibility of the residues . Higher To verify that the computed differences in the RMSF of the two protomers in dimeric 3CLPro were typical, we repeated the calculation on two additional trajectories obtained from different initial velocities starting from the same initial structures (see Methods for the details). The results see C,D show All the three MD trajectories of dimeric 3CLpro were analyzed using essential dynamics (see Methods for details) and, in particular, sampled conformational space was analyzed to look for populated conformational sub-states relevant to catalysis. Projection of all trajectories onto a principal plane defined by eigenvectors of the trajectory resulting by concatenating the two chains of the dimer in a single chain trajectory.In the first simulation, at global level, the conformational dynamics of the dimeric 3CLpro shows that the single chains have different conformational behavior, as evidenced by the projections of Cα coordinated onto the plane defined by the first two eigenvectors  of the combined trajectory  are similar.In order to quantitatively compare the similarity between different principal modes, the inner product of the first eigenvector  of the corresponding protomers has been calculated. The inner product between chain A and B is 0.21 and the corresponding value for chain A and the monomer is 0.17, suggesting that the first essential mode in these two cases is different. The inner product between the first eigenvectors of chain B and the monomer is 0.82, thus indicating a high similarity of this essential mode. This quantitative analysis suggests that chain B in dimeric 3CLpro is more similar to monomeric protease as compared with chain A.We also calculated the principal components defined by the concatenated trajectories of all the chains of 3CLpro of the three independent simulations, resulting in a total of 10 µs. The rationale was to define a common principal plane able to discriminate globally and locally among the dynamics of individual chains. It is worth noting see  that theThe essential dynamics analysis of the dimeric 3CLpro trajectory was also performed. The residue components of these eigenvectors provide useful information on the contribution of specific residues to the overall global dynamics. To this end, the positional fluctuations components of the first and second eigenvectors in dimeric 3CLpro are shown in We compared the residue components of all dimeric 3CLpro trajectories and found see  that, alThis section reports the analysis of the binding pocket regions of 3CLpro. We determined the structural stability of the pocket region by measuring the distance between the catalytic dyad residues, that is, His-41 and Cys-145 see . The figThis also indicates that, in chain A, the two catalytic residues remain at a short distance throughout the simulation, while they fluctuate in chain B. This is also evident analyzing the corresponding histograms of the distance  discriminate the behavior of the two sampled spaces, thus suggesting that, in the apo state, the two pockets are different from a dynamical viewpoint.In particular, we reported the eigenvector components of the binding pocket residues of the first and the second eigenvectors in The figure shows that the fluctuation of the backbone atoms of residues of the two loops, residue range 45–49 and 187–192, are correlated and contribute to a high extent to the main dominant motions.3 and 120.2 ± 93.6 A3, respectively). For comparison, the average volume for the monomeric pocket is 49.6 ± 61.4 A3. On the contrary, in both runs #2 and #3, we observed a larger accessible volume in chain B than in chain A . In particular, we measured the volume as a function of time for chain A and B in dimeric 3CLpro and for the monomeric protease. The data are reported in  chain A . In partThe large differences observed among the pocket volumes are mainly ascribable to the conformational rearrangements of the two loops that regulate the accessibility to the catalytic site. This is clearly evident in run #2, where the loop 187–192 moves backward, opening up a significant volume . On the The computational study presented here reports the analysis of 2 µs trajectories of the monomeric and the dimeric form of the SARS-CoV-2 3CLpro. It is worth noting that the starting structure of dimeric 3CLpro of our simulation was taken from the holo 3CLpro where the ligand was removed. This could potentially affect the conformational space accessible to our simulated protein throughout the simulation. Notwithstanding, our data provide evidence that the conformational dynamics of the protein chain is different in the dimeric 3CLpro as compared with the monomeric form. In particular, the flexibility of the protein chain is higher in the monomeric 3CLpro than in the dimer and the long loops connecting domain II and III account for most of the flexibility of the protease. The loops regions provide access to the binding site and the catalytic dyad and, therefore, play an important role in the catalytic activity. This is evidenced when the minimum inter-residues distance between Met-49 and Arg-188, which increases during the simulation, is computed. Interestingly, in run #1, the distance increase is more evident in chain A than in chain B, even though such a difference is less obvious at the end of the simulation see . These dOne can also speculate that the dynamical behaviour of dimeric 3CLpro may reflect an overall mechanism of catalysis according to an induced fit model (as was determined for SARS-CoV) . The priFurther evidence that the two chains are dynamically different and become active according to an induced fit mechanism is provided by comparing the volumes of the binding pocket as a function of simulation time . The oveA further conclusion that can be drawn is that the intermolecular interactions between the two chains in the dimer, in particular the interactions between the N-terminus and domain III of one monomer, are in turn critical to stabilize the residues of the catalytic pocket in the active form, thus ensuring the successful proceeding of the catalytic cycle in the dimer. This further supports that dimerization is important for the enzyme activity. Our findings are in agreement with previous studies regarding the 3CLpro of SARS-CoV, showing that the right conformation for catalysis in one protomer can be induced upon dimer formation and that the enzyme may follow the association, activation, catalysis, and dissociation mechanism for activity control .Our analysis, carried out on a microsecond time scale, highlighted the higher level of complexity of the dimeric form dynamics. Indeed, it is also possible that, in the dimer, one protomer is active while the other one is basically inactive, or even that the two protomers may exchange conformation. Overall, this study provides useful molecular insights into the dynamics and mechanism of the functional conformation changes of SARS-CoV-2 3CLpro, which may be of great interest in the search for more effective inhibitors.The initial structure for monomeric 3CLpro and its dimeric form  was taken from the PDB web site . Both proteases were simulated in the apo form and, therefore, covalently bound ligand in the initial PDB structure was removed and the cysteine residue was set in its reduced state. Tautomeric and protonation states for all titratable residues were set at their default state at pH = 7.The total number of atoms (protein + solvent + counterions) in the monomer and dimeric 3CLpro was 62,775 and 69,570, respectively.www.gromacs.org) with the AMBER99 force field [Briefly, the covariance matrix of the atomic positions is built from the MD simulations on a selected group of atoms . From the diagonalization of such a matrix, a set of eigenvectors and associated eigenvalues is obtained. The eigenvectors represent the principal motion directions of the system and, therefore, they are used to describe the “essential” protein modes, which often represent the functional ones. In this way, the fastest motions present in the simulations, which describe biologically not relevant motions , are excluded, making it possible to represent the protein dynamics in a reduced space, as defined by the eigenvectors, which approximates well the overall molecular motions. The covariance matrices, using the GROMACS g_covar tool, were constructed from the Cα atoms of proteins of the MD trajectory of the 3CLpro both in dimeric form and on concatenated trajectory of individual protease chains to compare the different simulations . The GROMACS gmx anaeig tool was used to calculate the 2D projections with respect to the first two eigenvectors and eigenvector components to the selected eigenvectors.MD simulations were performed with GROMACS 2020.2  [Detection and evolution of the active pocket volume during the molecular dynamics simulations were carried out with MDpocket software (rge.net) . Pocket www.exscalate4cov.network.As a part of our study, all the trajectories of the 3CLpro monomer and dimer are made publicly available at the following url:


Purpose: Wound-healing dipyridamole- and papaverine-based aerosols (D1/D2) as activators of the accumulation of cyclic adenosine monophosphate are promising drugs that can accelerate wound healing in wound processes of various origins. Methods: 128 rats were used in the study, including 38 in a pharmacological experiment on a model of stencil wounds and 90 in an experiment that studied the effect of spray on the number of CD34 cells in the blood of rats with chemically induced immunodeficiency. Immunodeficiency was caused by the fivefold administration of cyclophosphamide and prednisone. The expression level of CD34 was determined using flow cytofluorimeter. Results: Dipyridamole- and papaverine-based aerosols of two compositions (with and without ascorbic acid) have pronounced reparative properties, significantly accelerating epithelialization and healing of stencil wounds in rats. In terms of this type of action, they are somewhat superior to dexpanthenol. Dipyridamole- and papaverine-based aerosols have the ability to produce beneficial effect on the entire body’s immune system by stimulating the division of pluripotent CD34 cells. The combined effect of papaverine and dipyridamole on tissues leads to selective stimulation of the division of pluripotent cells in the wound, and contributes to a six-fold acceleration of restoration of the animal’s immune system after induced immunodeficiency. Conclusion: Topical application of D1/D2 aerosol samples on the skin of rats contributed to a statistically significant acceleration of regeneration processes. In terms of the appearance of granulations and epithelialization of wounds, D1/D2 aerosols were superior to dexpanthenol ointment. Experiments proved the ability of endogenous stem cells to significantly accelerate the wound healing process, particularly in diabetic patients (rat model).2 Another study has demonstrated that an excessive amount of cAMP in a wound can stimulate the migration of stem cells to the wound area and their rapid differentiation.4One of the main problems in the effective treatment of severe complications of type 2 diabetes mellitus is diabetic foot syndrome. Over time, the loss of sensitivity of the lower limbs at the late stages of diabetic neuropathy leads to a foot injury and the appearance of diabetic ulcers. These ulcers do not heal for a very long time; they become contaminated by bacteria, and in the end, would require surgical intervention.7 and inducers of cAMP accumulation. Ascorbic acid represents an indirect adenylate cyclase activator, and also, an inducer of cAMP accumulation and an important component of the tissue regeneration process in wounds.8 Using an animal model of Charcot-Marie-Tooth human disorder, was showed that ascorbic acid represses PMP22 gene expression by acting on intracellular cAMP concentrations. In this work, authors present kinetics data on the inhibitory effect of ascorbic acid upon adenylate cyclase activity.9As an agent for the treatment of trophic ulcers, we have developed a pharmaceutical composition in the form of an aerosol based on a combination of dipyridamole, papaverine and ascorbic acid. Papaverine and dipyridamole are universal phosphodiesterase inhibitors11cAMP and cGMP are intracellular second messengers involved in the transduction of various physiologic stimuli and regulation of multiple physiological processes, including vascular resistance, cardiac output, visceral motility, immune response, inflammation, neuroplasticity, vision, and reproduction. Intracellular levels of these cyclic nucleotide second messengers are regulated predominantly by the complex superfamily of cyclic nucleotide phosphodiesterase (PDE) enzymes. Cyclic nucleotide PDEs comprise a superfamily of metallophospho hydrolases that specifically cleave the 3′, 5′-cyclic phosphate moiety of cAMP and/or cGMP to produce the corresponding 5′-nucleotide. PDEs are critical determinants for modulation of cellular levels of cAMP and/or cGMP by many stimuli. Thus, the ubiquitously present PDEs play a pivotal role in regulating cell signalling via the breakdown of cAMP and cGMP. PDE inhibitors are therapeutic agents which target PDE isoenzymes and inhibit the metabolism of the secondary messengers  thus, prolonging the biological effect determined by the type of cell involved.12 Dipyridamole effectively stimulates capillary growth in the myocardium of rats.13 Dipyridamole has been found to be able to potentiate the action of acyclic nucleotides in the treatment of herpes viruses, probably through its immunomodulating interferonogenic effect.16It has also been shown that dipyridamole is able to stimulate the division of stem cells, which are the precursors of neurons.19Papaverine also has a number of additional immunotropic properties that have not been previously used in pharmacological practice. For example, papaverine has antiviral properties against a broad spectrum of viruses, due to both its direct antiviral effect and its ability to stimulate the production of endogenous interferons.The goal of this study is to determine the ability of the combination of two phosphodiesterase inhibitors, papaverine and dipyridamole in combination with ascorbic acid, to accelerate the healing of uninfected wounds in an experiment.The compositions were prepared on the basis of dipyridamole  and papaverine  in two compositions:D1 (without ascorbic acid): 1% dipyridamole, 1% papaverine hydrochloride; 0.05% chlorhexidine; 10% polyethylene oxide-400 ; distilled water up to 100%.D2 (with ascorbic acid): 1% dipyridamole, 1% papaverine hydrochloride; 0.05% chlorhexidine ; 5 % ascorbic acid ; 10% polyethylene oxide-400; distilled water up to 100%.Both aerosol variants are equivalent in terms of the ratio of active ingredients , and for the second version of the aerosol (D2) it is 0.25% sodium ascorbate).In experiments also were used Cyclophosphan  and prednisolone 20 Similar solutions were also prepared for intraperitoneal administration, but without chlorhexidine and polyethylene oxide-400. The concentration of ascorbic acid in the D2 variant was reduced to 0.25%.Aerosol solutions were injected into a mechanical nebulizer, and pressurized balloons were not used. To enhance the penetration of active substances into the affected tissues, 10% polyethylene oxide-400 was used as an excipient in both versions of the aerosolThe wound healing action was studied on the basis of a model of stencil wounds in rats. Their effect on the number of animals’ own stem cells, CD34, was also evaluated.The study of the wound healing properties of experimental aerosols D1/D2 was conducted on 38 Wistar male rats.The experiments involved Wistar male rats weighing 160–200 g. The animals were obtained from the Biomodelservice  and kept in vivarium in Mechnikov Institute of microbiology and immunology.22The animals were divided into four groups: (1) wounds treated with D1 aerosol (n = 10); (2) wounds treated with D2 (n = 10); (3) wounds treated with the reference drug dexpanthenol  (n = 10); (4) control group (n = 8). Dexpanthenol is a vitamin B5 - well-known substance in the world for tissues regeneration stimulating.23 of the back were simulated in animals under anesthesia with diethyl ether. The initial wound size was 4 ± 1.0 cm2. The application of drugs was initiated from the first day after the alteration. The average amount of aerosol was 0.5 mL/animal. Applications were performed twice a day to make sure that the drug covers the entire surface of the wound and approximately 0.5 cm of depilated skin around it. Then, the animals were fixed for 30 minutes to ensure the absorption of the solution and to prevent them from licking wounds. A planimetric study23 was conducted on the 3rd, 7th, 10th, 14th and 18th day from the beginning of the experiment. The obtained parameters of the wound surface area were statistically processed using the analysis of variance.Stencil woundsThe drugs were studied in an experiment on a model of cytostatic hemoimmunosuppression.The experiments were conducted on 90 male Wistar rats weighing 160–200 g. The animals were kept under conditions of free access to food and water. Two experimental and one reference groups consisted of 30 animals each. In both groups, hemoimmunosuppression was caused by a five-fold intraperitoneal administration, at 24-hour intervals, of cyclophosphan  in a dose of 10 mg/kg, and prednisolone  2 mg/kg in 3 ml of normal saline. On the next day after the completion of the administration of hemoimmunosuppressive drugs, the animals were intraperitoneally injected with a D1/D2 composition in form of IV injection:D1 (without ascorbic acid): 1% dipyridamole, 1% papaverine hydrochloride; distilled water up to 100%.D2 (with ascorbic acid): 1% dipyridamole, 1% papaverine hydrochloride; 5% ascorbic acid; distilled water up to 100%.ex vivo research.D1/D2 used in the quantity of 0.1 ml/animal (2.5 mg/kg) for next 25 kit for cytofluorimetry via a FACS Calibur flow cytofluorometer. The digital material was processed using the analysis of variance, Student’s/ Bonferroni modification , although statistically significantly.27Dipyridamole, on the contrary, inhibits wound healing by 25% against control.28The preservative 0.05% chlorhexidine has no effect on uninfected wounds, although it slightly accelerates the healing the infected wounds due to antiseptic properties.The aerosol of the two compositions had a significant impact on the dynamics of the wound process in rats. On day 3 (48 hours after the simulation of stencil wounds), the maximum intensity of the inflammatory process was noted in the pathology control group; there were no statistical differences between the experimental and the reference groups. Oedema and hyperemia affected the surrounding tissues as well. During this period, the area of the wound surface even slightly exceeded the initial parameters . The genSubsequently, the experimental groups showed a fast positive dynamics in the clinical condition of rats. On day 7, hyperemia and oedema in the experimental groups were insignificant, and granulation tissue was formed in the center of the wound. The onset of reparative processes was noted: marginal occlusion of the defect, which changed the wound area. During this period, a significant decrease in the area of the wound surface was observed vis-à-vis the parameters of day 3. At the same time, this parameter did not change in the pathology control group.On the 10th day of the experiment, marginal epithelialization of wounds, a significant decrease in the area of the wound surface in comparison to the baseline data and untreated control, complete cleansing of the wound surface, the presence of granulations, and the absence of inflammation were noted in both experimental groups.The subsequent periods saw a rapid healing of the wound defect in rats treated with D1/D2 aerosols. On the 14th day, the wounds were dry and their area was 0.72 and 0.78 in groups 1 and 2, respectively, which meant that most of the wound surface was epithelialized. At the same time, although a number of animals in the pathology control group showed positive dynamics, four out of eight rats still had an inflammatory process, and the area of the wound surface was large. Statistically significant differences between the experimental groups (including dexpanthenol group) and the reference group were noted as early as on day 7. During the same period, as well as on days 10 and 14, significant advantages of the experimental sprays vis-à-vis the action of dexpanthenol were observed. By day 18, wounds were completely healed in all rats of the experimental groups, while in the reference group, three animals did not complete wound epithelialization and one of them had pus discharge.There were no statistically significant differences between the D1 and D2 groups. Therefore, ascorbic acid had no pronounced influence on the wound healing effect produced by the spray with dipyridamole and papaverine.Dexpanthenol ointment also helped reduce the wound healing time. However, its effect was somewhat less pronounced than the effect from the use of aerosols.The administration of cytostatic drugs led to a three- to fourfold decrease in the level of CD34 by the time of the start of therapy comparing to the baseline level. Dipyridamole with papaverine in both compositions had a stimulating effect on the processes of bone marrow regeneration and restoration of peripheral blood parameters, increasing the level of CD34 to normal values. By day 30, its level increased more than twofold thanks to the effect from D1 and D2 samples, while in the animals from the reference group, it returned to normal values only on the 60th day. Therefore, dipyridamole with papaverine caused about a twofold acceleration of these processes.The maximum effect from the use of the compositions was observed on the 60th day, and the restoration of the physiological level of pluripotent cells was observed even on the 10th day after the start of their use. The increase in the number of pluripotent cells coincided in time with the stimulation of reparative processes (on the model of stencil wounds in rats), which apparently indicates the predominant stimulation of stem cell division at the periphery rather than the enhancement of bone marrow functions.The presence of ascorbic acid in the compositions had no bearing upon their effect on stimulation of the production of CD34 cells.Dipyridamole- and papaverine-based aerosols of two compositions (with and without ascorbic acid) have pronounced reparative properties, significantly accelerating epithelialization and healing of stencil wounds in rats. In terms of this type of action, they are somewhat superior to dexpanthenol.Dipyridamole- and papaverine-based aerosols have the ability to produce beneficial effect on the entire body’s immune system by stimulating the division of pluripotent CD34 cells.The combined effect of papaverine and dipyridamole on tissues leads to selective stimulation of the division of pluripotent cells in the wound, and contributes to a six-fold acceleration of restoration of the animal’s immune system after induced immunodeficiency.The absence of a statistically significant difference between the groups of D1 and D2 compositions indicates an insignificant role played in wound regeneration by ascorbic acid in the aforementioned dosage.The animals were cared for according to the international guidelines GOST 33647-2015 , the international recommendations of the European Convention for the Protection of Vertebrate Animals used for Experimental and Other Scientific Purposes . The protocol of the experimental study was approved by the Ethics Committee of Mechnikov Institute of Microbiology and Immunology of National Academy of Medical Sciences (protocol № 3-2018 of 14.12.2018).Authors declare no conflict of interest in this study.We are grateful to the staff of the Institute of Cryobiology and Cryomedicine of the National Academy of Sciences of Ukraine for their help in studies using a flow cytometer.


CFRP (carbon fiber reinforced polymer) strips are currently often used to strengthen reinforced concrete structures in flexure. In order to ensure effective strengthening, proper connection between FRP material and concrete structure is needed. CFRP strips can be applied passively (only by bonding to the concrete surface) or actively (by prestressing before bonding). In the case of passive strengthening, CFRP strips connecting by bonding to the surface along the strengthened element are usually sufficient. However, active (prestressing) CFRP strips should be additionally anchored at their ends. Anchoring of unidirectional CFRP strips to the reinforced concrete is difficult because of their weak properties in transverse directions. The paper presents a development of mechanical steel anchorages used in an active CFRP flexural strengthening system for reinforced concrete structures. The anchorages were made of steel plates connected to CFRP strips with steel rivets and epoxy adhesive. They were developed within series of tests on specimens from small-scale to full-scale tested in an axial tensile scheme. The paper describes successive modifications of the anchorages as well as the results of full-scale tests. The final version of the anchorage developed during the research had a tensile failure force of 185 kN, which is sufficient value for CFRP strengthening purposes. The carbon fiber reinforced polymer (CFRP) materials are a viable alternative to structural strengthening and offer several advantages such as high strength-to-weight ratio, ease of transport and installation, excellent fatigue characteristics, and are noncorrosive thus highly durable. A few different approaches were investigated to assess the effectiveness of the CFRP materials for strengthening of civil structures. Since the beginning of the new millennium, hundreds of research papers on flexural strengthening of reinforced concrete (RC) structures with the CFRP materials have been published in scientific journals and conference proceedings. The most important research findings were reviewed and summarized in the following books ,2,3,4 anBy prestressing the CFRP strip, which combines benefits of passive bonded CFRP strips with the advantages due to external prestressing, the ultra-high tensile strength of carbon fiber composites can be utilized and much higher effectiveness of the strengthening technique is achieved. A greater CFRP tensile capacity was employed and it contributed to the load-carrying capacity of the strengthened structure under both service and ultimate conditions ,12,13,14Over a dozen anchor systems have been developed for gripping and prestressing CFRP strips in recent years. The existing CFRP strip anchors can be divided into two major categories: Epoxy-based anchors and mechanical anchors (bolt-based or friction-based) ,17,18,19The new domestic approach in this field has been developed within R&D project at the Rzeszow University of Technology (RUT) . The maiThe novel CFRP strengthening system (NPS II) consists of two main elements: Mechanical steel anchorages mounted on both ends of a single CFRP strip and a relevant tensioning device. Epoxy adhesive is used to bond a section of CFRP strip between anchorages to the concrete surface. The strips with determined length are delivered on site as ready-to-install, i.e., with two prefabricated steel anchorages mounted on both strip ends. There are two kinds of anchorages: An active anchorage combined with a tensioning device and a passive one, mounted on the second end of the CFRP strip. The anchorage has two functional areas: External and internal a. The stThe strengthening system uses ultra-high-strength UHS 614 strips with cross-section of 1.4 mm × 60 mm with the ultimate tensile strength of 3200 MPa, modulus of elasticity of 160 GPa and the strain at failure of about 2% . Larger-width strips can be applied as well, however, it would affect the results. The relevant comment is featured in Conclusions.Steel plates of the anchorages are made of S355 steel grade with minimum tensile strength of 510 MPa, modulus of elasticity of 210 GPa, yield point of 355 MPa, and elongation of about 16%. CFRP strips are joined with steel plates by an epoxy-based adhesive as well as by 4-mm-diameter rivets made of S215 steel grade with minimum tensile strength of 375 MPa, modulus of elasticity of 210 GPa, yield point of 215 MPa, and elongation of about 25% (according to the steel grades).Two types of the adhesives are used in the system. A standard epoxy-based adhesive is used for the final bonding of the strip to the concrete substrate between anchorages. The standard adhesive is characterized by flexural strength of 53.3 MPa, compressive strength of 107 MPa, flexural modulus of elasticity of 10.3 GPa, adhesion to dry concrete of 4.6 MPa, and glass transition temperature of 120 °C. It serves as a protective layer covering the strip between the anchorages. This type of adhesive is also used to bond CFRP strips with steel plates inside anchorages in the NPS I system (tested in S1N and S2N series). In the NPS II strengthening system, standard adhesive is used only to bond CFRP strips to a concrete surface while a modified epoxy adhesive with the addition of activated corundum sand is used in the anchorages. The modified adhesive is characterized by tensile strength of 32.5 MPa, tensile modulus of elasticity of 15 GPa, shear strength of 12 MPa, and glass transition temperature of 105 °C. The mechanical characteristics of the adhesives were obtained from the material tests.The anchorages were developed within a series of tests on specimens from small scale to full scale. In the first step of the research, experiments on small-scale specimens were done in search of the most efficient steel/composite surface treatment method as well as optimal composition of epoxy adhesive. In the next step, the effectiveness of several types of steel-composite joints in medium-scale (1:2) were compared. These studies are described in details elsewhere . Only thBased on the tests on small-scale specimens treated by various methods, the most efficient ones were determined to achieve efficient treatment of steel plates and CFRP strips before bonding them together. For steel plates the most effective method is sand blasting followed by cleaning with acetone, whereas, for CFRP strips, chemical cleaning using acetone-based solvent was found the best.Medium-scale tests concerned several various types of steel-composite joints: Bonded, riveted, bolted, and hybrid bonded/bolted as well as bonded/riveted. The aim of this part of the research was to determine the most effective type of joint as well as to preliminarily define the characteristic parameters of the final full-scale specimens. The number and layout of the mechanical fasteners (bolts or rivets), the torque moment of the bolts, or clamping force of the rivets, as well as the joint length, were considered in medium-scale tests .In the final step of the research, the two most efficient joining methods (bonded/bolted and bonded/riveted) were selected to test them finally on full-scale (1:1) specimens, i.e., actual anchorages. In this paper, the tests of full-scale specimens of bonded/riveted anchorages are described.The single hybrid bonded/riveted (N-type) anchorage was made of three S355 steel plates: Two external with the dimensions of 550 mm × 128 mm and thickness of 2 mm or 3 mm, and one internal (spacer) with the dimensions of 249 mm × 126 mm and a thickness of 2 mm (comprising a 1.4-mm-thick composite strip and two layers of epoxy adhesive 2 × 0.3 mm). Steel plates were welded together along the edges to create a pocket, in which the CFRP strip end is fixed. The end of the strip was attached in the steel anchorage pocket along the section of approximately 300 mm . The fThe tests of the N-type anchorages on full-scale specimens were carried out within five test series, S1N–S5N (three specimens in each series). In the first two series , the anchorages used in the first version of strengthening system (NPS I) were investigated for comparison with newly developed anchorages. The anchorages tested in S1N and S2N series were made of the 2-mm-thick external plates. A standard epoxy adhesive mix  was used to bond the steel plates to the CFRP strip. The steel plate and CFRP strip surfaces were not subjected to any special mechanical or chemical treatment prior to joining. The arrangement of rivets applied in these series is presented in In the next three series (S3N–S5N), the anchorage specimens, made according to the modified technology (NPS II), were tested. The main modifications of the technology for anchorage specimen development consisted of increasing the thickness of the external plates to 3 mm, changing the number and arrangement of the rivets , using aThe results obtained in the subsequent test series (S3N–S5N) and the observations of the anchorage specimens’ behavior under static load allowed successively introducing further technological modifications. The technology for anchorage development was, therefore, improved from test to test of subsequent series. A detailed description of the technology for specimen development in the subsequent test series is presented in the subsections below.In the first series, the anchorage specimens, made according to the technology used in the NPS I system, were tested. In this series, exceptionally high-modulus HM 614 strips with the ultimate tensile strength of 2730 MPa, the modulus of elasticity of 268 GPa, and the strain at failure of 1% were used . The spIn the second series of tests, the anchorage specimens, made according to the same technology as the S1N series, were tested. The only difference was to use the ultra-high-strength UHS 614 strips with parameters described in the In the third series, the tests were conducted on the anchorage specimens, made according to the modified technology of bonding steel plates with the composite, developed on the basis of the results of adhesive tests carried out in the preliminary phase . The extThe anchorage specimens tested in the S4N series were made in the same way as the S3N series specimens. The only difference was to make a longitudinal cut in the composite strip where the middle row of rivets was arranged .The specimens in the S5N series were prepared in the same way as for the S3N series  with the following changes. The curing time for the adhesive bonding was increased to 12 h. The rivets were tightened using a hydraulic press , by meanAll the anchorage specimens in each series were subjected to the axial tensile tests in the Instron J1D 1200 kN testing machine . The anchorages were installed in the machine by means of specially designed jaws allowing hinged attachment .The tests were carried out with a displacement-controlled rate of 2 mm/min. During the tests, the increment of load and displacement between the jaws of the testing machine (displacement of the actuator piston) was measured. The measurement of these values was provided by the set of sensors built in the testing machine. Due to direct measurement through the sensors of the machine, presented displacements include slipping in the machine jaws, elongation of the CFRP strip, and displacements occurring in the joint itself. The specimens were tested until failure. The anchorage failure occurs by the rupture of the strip or failure of joint between CFRP strip and the steel plates. The failure mode of the anchorage specimens was recorded with the speed video camera Vision Research Phantom v640, which allowed recording over 2000 images per second .The load-displacement plots for the subsequent specimens tested in the S1N series are presented in During the first test series, the mean value of the failure load of the anchorage specimen was 110 kN. The standard deviation for the first series was 19.4 kN. The observed result dispersion exceeding 17% was quite significant. This may have been due to the high rigidity of the composite steel adhesive bonding and the associated high vulnerability to the heterogeneity of the steel-adhesive and adhesive-composite bonding.On the load-displacement plots presented in During the first series of tests, the failure mode of all three specimens was the same. The failure took place by the strips slipping out from the steel plates . MoreoveThe load-displacement plots for the subsequent specimens from the S2N series are presented in In the second test series, the mean failure load of the specimen was 109 kN. The standard deviation value for the second series was 9.6 kN. The result dispersion was much lower than in the case of the first test series and did not exceed 9%. From both test series, it can be, therefore, concluded that the anchorages with the UHS 614 strips were less vulnerable to the heterogeneity of the steel-adhesive and adhesive-composite bonding. This may be due to the difference in the elasticity modules of the used CFRP strips.During the tests of all the specimens, clear partial slips were observed at approx. 40–50% of the anchorage failure load, as well as several smaller slips occurring during the whole test. They were characterized by the strip partially sliding out from the steel anchorage. The partial slips are clearly visible in the load-displacement plots . The sumDuring the second test series, the failure mode of all three specimens was the same as in the S1N series. The failure took place by the strips slipping out from the steel plates .The load-displacement plots for the subsequent specimens from the S3N series are presented in During the third test series, in which the anchorages were made by means of the new technology (NPS II), the mean failure load was equal to 145 kN. The standard deviation for the third series was 16.7 kN. The observed result dispersion equaled 11.5%.In the third test series, no apparent partial slips were observed. Only during the second specimen tests, two characteristic load decreases occurred in the plot : The firIn this series, the failure mode took place by the strip slipping out from the steel plates accompanied by longitudinal cracks of the strip outside the anchorage along the middle row of the rivets and chipping of the overlay, used for strengthening the strips, next to the steel plate edge .The tests in the third series were recorded with the speed video camera. Thanks to that, it was possible to record the tests at the frame rate of 2300 frames per second, which allowed analyzing in detail the failure mode of the anchorages. The sequence of failure of exemplary specimen P3/S3N is presented in The failure was initiated by longitudinal shear cracking of the strip along the middle row of the rivets and by the half of the strip sliding out from the anchorage b. This cThe load-displacement plots for the specimens tested in S4N series are presented in During the fourth series of tests, the mean failure load value of the anchorage was 155 kN. The standard deviation for the fourth series was 11.4 kN and the variability coefficient equaled 7.3%.In the S4N series, the failure occurred similarly to that of the third series. The strips were slipping out from the steel plates and the longitudinal shear cracking was observed. In the case of the P2/S4N and P3/S4N specimens, there was one crack along the middle row of the rivets, which split the strip into two parts b,c, wherThe load-displacement plots for the specimens tested in S5N series are presented in During the fifth series of tests, the mean failure load value of the anchorage specimen amounted 185 kN. The mean anchorage efficiency equaled 67%, i.e., 11 percentage points more than in the fourth series. The resulting dispersion was also higher, mainly due to the P3/S5N specimen, in which a very high failure load of 217 kN was obtained. The standard deviation for the fifth series of tests was 29.2 kN and the variability coefficient equaled 15.8%.In the fifth series of tests, the failure mode also took place by the strip slipping out from the steel plates. As in the previous test series, longitudinal shear cracking of the strips occurred along the middle rivet row. In addition, there were cracks on both sides in approx. one-fourth and three-fourths of the strip width . In the A resulting summary of the N-type anchorage tests is presented in In Both the maximum, minimum, and mean failure loads increased in the subsequent test series. Due to introducing further modifications in the anchorage development technology from series to series, increasingly higher load-carrying capacity of anchorages was achieved. This progress is illustrated in the plot in Already in the third test series, in which the first modifications were introduced in the anchorage manufacturing technology, an increase of 33% in the mean failure load was obtained. The load-carrying capacity of the anchorages was improved largely due to using a new, modified adhesive composition and a special surface treatment of both connected materials. Changing the steel plate thickness and the rivet arrangement also influenced the increase of the anchorage load-carrying capacity. In the S4N series, due to the longitudinal cut in the composite strip where the middle row of rivets was arranged, there was an even greater increase of the mean failure load, by 42% compared to the S2N series. In addition, the highest homogeneity of the results was obtained in this test series. However, eventually, the idea of carrying out the cuts was abandoned due to the technological difficulties of such an operation. Instead, in the S5N series, the curing time of the adhesive bonding was extended from 3 to 12 h and rivet upsetting was controlled in the hydraulic press. This allowed to achieve a mean failure load of 185 kN, which indicated an increase of 70% compared to the original version of the anchorages (tested in S2N series). Moreover, in the P3/S5N specimen, an extremely high value of the failure load, i.e., 217 kN, was obtained. Thus, the composite material utility reached 80%. This indicated the great potential of this type of anchorages. In the last test series, however, a significant dispersion of results was noted (variability coefficient exceeding 15%). Therefore, the developed bonded/riveted anchorages require further studies on their improvement, especially in order to obtain better homogeneity of the results.The failure load was reflected in the anchorage efficiency, defined as the ratio of the failure load of the anchorage specimen to the ultimate tensile strength (force) of the CFRP strip . The applied modifications allowed to achieve an average anchorage efficiency of 67% in the last test series. This value was sufficient for a post-tensioning system for strengthening concrete structures because optimal strengthening effects are obtained with a strip prestressing level amounting to about 60% of CFRP tensile strength . Figure Regardless of the test series, the failure always had a similar mode: The strips slipping out from the anchorage (steel plates) with simultaneous longitudinal shear cracking of the strips along the rivet row and the likelihood of an additional delamination in approx. one-quarter and three-quarters of the strip width. In the case of the S1N and S2N series (NPS I), the failure took place in two stages. At approximately 50% of the failure load, the sharp decreases of the load connected with the partial slips of the strip from the steel plates were observed. Thanks to introduced modifications, in the case of most specimens in the S3N–S5N series (NPS II), the partial slips were eliminated. The strip was gradually slipping out from the anchorage steel plates until failure.Increased value of the N-type anchorage efficiency compared to the NPS I technology indicated the effectiveness of the proposed modifications.Rivets crossing the composite strip in the anchorage weakened its cross-section. A better solution is, therefore, to arrange the rivets in one row crossing the strip, which reduces the number of damaged fibers.Using the external steel plate with the thickness of 3 mm allowed for a more homogeneous distribution of stress after rivet upsetting. The 2-mm-thick steel plate used in the S1N and S2N series was too thin; strains occurring during rivet upsetting negatively affected the possibility to achieve a homogeneous compressive stress distribution in the strip.Lowering the temperature in the process of epoxy adhesive curing from 110 °C for the S1N and S2N series down to 80 °C in the S3N–S5N series increased the anchorage load-carrying capacity.Extending the adhesive bonding curing time to 12 h had a positive effect on the load-carrying capacity of the anchorages.Increasing the rivet arrangement density in the last two rows at the anchorage end of the strip and introducing the additional rivets on the edge perpendicular to the anchorage axis gave a positive result. The compensation occurred by pressing the nonlinear tensile stresses in the adhesive bonding, present in the internal part of the anchorage.The ultra-high-strength UHS 614 strip anchorages were less vulnerable to the heterogeneity of steel-adhesive and adhesive-composite joints compared to the high-modulus HM 614 strip anchorages.Further research should be carried out to increase the homogeneity of the obtained results and to increase the load-carrying capacity of the anchorage by fully incorporating the strip cross-section. The hybrid bonded/riveted anchorages have very high potential. The maximum failure load achieved so far amounted to 217 kN (79% of the CFRP tensile strength).The development of a novel anchorage for CFRP strengthening of RC beams was described. The anchorages were subjected to many tests in order to develop an optimum solution. Finally, anchorages for CFRP strips with cross-section of 60 mm × 1.4 mm with a tensile load-bearing capacity of 185 kN were developed and verified. Based on the test results of the N-type anchorages, the following conclusions can be drawn:The system was developed particularly for strips of 60 mm in width because only these strips have been manufactured by the industry partner in the R&D project. Moreover, in domestic circumstances the 60-mm-wide CFRP strips are the most popular option for flexural strengthening. Larger width of the strips surely would affect the results ,26. The Flexural strengthening of RC structures with prestressed CFRP strips is relatively new technology , so there are no proven life-cycle experiences with it. A few fatigue and accelerated long-term tests revealed that there is no danger to use this technology in the life-cycle term ,29,30,31The novel strengthening system has been examined on the RC beams in the laboratory  as well Patent No. 216773: “CFRP strip for strengthening building elements and device for tensioning CFRP strip before bonding it to a flat surface of a building element”, Polish Patent Office, Warsaw, Poland, 2014.Patent Application No. P.417440: “Device for mounting CFRP strip to building elements and the method of mounting the strip to building elements”, Polish Patent Office, Warsaw, Poland, 2016.


Due to the sustainable development of agriculture machines with large working widths of 4–6 m or even 9–12 m are increasingly often used for agrotechnical operations. The sowing machinery whose working widths are much bigger than the width of the seed box is equipped with a pneumatic system for transporting seeds from the seed box to coulters. One of the structural elements that affect the sowing accuracy in such seed drills is the distribution head with a diffuser. This article is about research on the influence of the distribution head deviation from the vertical position and constructional variants of the diffuser  on the accuracy of distribution of a stream of rye and oat seeds (a seed-and-air stream), which differ in physical characteristics. The main elements, i.e., the innovative stream distributor in the head and the diffusion rings were made using an original design and the rapid prototyping method. The research proved that a change of 0–10° in the angle of the distribution head deviation from the vertical position significantly affected the sowing quality of oat seeds only. The position (density) of the diffusion rings in the lower section of the diffuser (near the supply elbow) was the most effective for both oat and rye seeds, where the average values of the coefficient of variation were 5.31% and 4.62%, respectively. The research results can be used to redesign the construction of the diffuser of the seed drill distribution head so as to reduce the resistance of transport of the seed-and-air mixture in order to improve seed sowing evenness. CV) ranged from 15% to 27% [CV) decreased to 4–8% [CV) was reduced.Sowing is one of the most important agrotechnical procedures in the cultivation of cereals and other crops. Machines with large working widths (4–6 m or even 9–12 m) are increasingly often used for sowing. These are usually pneumatic seed drills with the main central air system transporting seeds from the seed box to seed ducts ended with coulters , the con% to 27% . In ordeAs it is difficult to evenly distribute the seed stream in pneumatic seed drills, there is a wide range of publications about the causes of unevenness ,13,14,15There are numerous interesting technical solutions concerning distribution heads in the world patent database ,26,27. TCV) and how the value of the coefficient of variation (CV) was affected by the elbow placed in front of the diffuser. Kravtsov et al. [CV).The authors of numerous studies on this subject indicate various causes of the uneven distribution of the seed-and-air mixture in the distribution head of the pneumatic seed drill . The geov et al.  proved tOur review of the designs and tests of components of the sowing system of universal pneumatic seed drills showed that the research results presented in reference publications were not unequivocal and did not exhaust the issue under study. The problem of even distribution of the seed-and-air stream has not been solved, especially when seeds are sown on soils with different terrain. Additionally, reference publications do not provide a clear explanation of how the position of diffusion rings along the length of the diffuser tube affects the seed sowing evenness.In view of the abovementioned facts, the aim of this study was to determine how the deviation of the distribution head from the vertical position and diffuser variants (the number of diffusion rings and the configuration of their position in the diffuser tube: the distance between them) affected the accuracy of distribution of a stream of rye and oat seeds, which differ in physical characteristics. The study was conducted to find the best configuration of distribution heads.There was one stage of laboratory investigations on rye and oat seeds. The mass of seeds distributed in the head of the pneumatic seed drill was measured at the research facility described in The research object was an innovative head distributing the stream of seeds . It consDuring the tests, the distribution head with the diffuser was placed on a tilting stand (9) allowing the head to be tilted from the vertical position within ‒20° to 20°. The seed-and-air stream in the innovative distribution head was supplied through the feeding pipe elbow (8), diffuser (3) with diffusion rings (5) separated by spacer sleeves (4). The seed stream was divided into 16 individual streams in the distribution head. Then, it was directed to the coulters through the downpipes (6) and downpipe elbows (7) with attached pneumatic ducts.Six variants of the diffuser shown in 3/s, powered by a 5.5 kW AC motor (8), seed ducts (18) receiving seeds from the outlets of downpipe elbows (7) to individual chambers (6) of the collecting box (10). Before each measurement cycle, the airflow velocity was monitored with a Testo 440 meter with a hot wire probe . The airstream velocity was constant, i.e., 15.5 m/s. It was measured before the fan and calculated using the flow continuity equation to obtain an airstream velocity of 35.3 m/s at the fan outlet. The test facility was also equipped with a block of an automatic system weighing the seeds sown (4) from 16 individual chambers of the seed collecting box. It also had a computer with dedicated software for data acquisition and calculation of the value of the transverse sowing unevenness index, which was based on the dependence used for the calculation of the coefficient of variation (CV).The research on the innovative distribution head of the pneumatic seed drill was conducted at a facility that was specially designed and constructed for laboratory investigations at the Department of Heavy-Duty Machines, Poznań University of Technology, Poland . The tesSeeds of two cereal species were used in the research: rye  with a thousand kernel weight of 34.1 g ± 0.83 and a moisture content of 8.5% and oats (Spartan cultivar) with a thousand kernel weight of 32.2 g ± 0.62 and a moisture content of 9.3%. These were certified seeds purchased from Poznańska Centrala Nasienna .At the end of each seed sowing test cycle  at the test facility, the 16 chambers of the seed collecting box were opened sequentially and their contents were weighed and returned in a closed circuit to the main tank (1). Therefore, valves opened by means of a cam mechanism were installed at the bottom of the chambers of the collecting box. The valve opening mechanism consisted of a movable cam carriage driven by a BG 65X25 SI Dunkermotoren servomotor (17) by means of a toothed belt (10). Borland Pascal—a specially written program in the RAD Delphi 2010 environment (Embarcadelo) was used to control the servomotor (17). A rectangular collector (11) was mounted under the valves along the 16-chamber collecting box (6). When the valves opened, seeds fell into the collector and then they were sucked into the airstream generated by the suction fan (19). Then, the seeds went through the suction duct (12) to the separating cyclone located above the main tank (1). The conical bottom of the separating cyclone in the lower part was closed by a flap (13), which was not connected to the cylindrical part of the cyclone. It was based on three strain gauges (14) for weighing seeds from each chamber of the collecting box separately with an accuracy of 0.005 kg. During the transport of seeds from the chambers of the collecting box (10) the cyclone flap (13) was closed with a force of about 500 N by the negative pressure in the system. Then, the suction blower drive (19) was switched off and the bottom of the cyclone fell on the strain gauges. When the flap closing (13) the bottom of the cyclone fell, it was electromagnetically locked by the control system. The entire seed weighing cycle was fully automated. After the seeds from all the 16 chambers of the collecting box (10) were weighed, a test report was generated and the results were saved in *. txt files.Measurement parameters were read from the assumed research program: airstream velocity and measurement time;The motor of the main fan was switched on. It was necessary to wait until its rotational speed was constant;The cam carriage was checked to ensure that it was in its extreme position;The rotational speed of the fan shaft was adjusted to achieve the assumed airstream velocity at the inlet of the seed dosing unit;The sowing unit was started and the desired rotational speed of the sowing shaft was adjusted;When the unit reached the assumed efficiency, it was necessary to wait for 5 s to determine the sowing conditions;The seed-and-air stream was directed to the distribution head;Seeds were sown according to the assumed research plan with a measurement time about 10–60 s;The drive of the sowing unit and the main fan were switched off;The recirculation unit motor fan was started;The negative pressure in the cyclone was checked;The valve of another chamber in the box was opened;After 30 s, the recirculation unit motor was turned off;The weight of seeds sown and the weight of the whole seed tank were read from the force sensors;The flap in the lower part of the cyclone was opened and the seeds were released;When the valve cam carriage reached its extreme position, Chamber 1 was the starting point;The carriage moved to the starting position;CV) were calculated).The measurement results were processed and saved in the database , four digital outputs (DO0–DO3), two digital inputs  and four analog inputs AI0–AI4, . Data anThere were four replicates of the experiment for all combinations of variable parameters according to the algorithm shown in The following factors were assumed in laboratory investigations conducted on both seed species (rye and oats):−Theoretical (assumed) sowing speed—2 m/s;−Sowing shaft rotational speed—29 rpm;−Assumed length of the measuring section (sowing pathway)—150 m;−Airflow velocity at the fan inlet 15.5 m/s.(a) Constant:−jα: 0°, 5° and 10°;The angle of the distribution head tilt from the vertical position −ip: p1, p2, p3, p4, p5, p6;Diffuser variant: the position and number of diffusion rings −ng: rye, oats.Seed species (b) Variable:−CV).Coefficient of variation ((c) Resulting factors:CV) from the dependence shown below [S is the standard deviation of the average weight of seeds sown in four replicates and X is the average weight of seeds collected from all coulters.The influence of the angle of the distribution head deviation from the vertical position and the deflector variant on the evenness of distribution of the seed-and-air stream to individual coulters was determined by calculating the coefficient of variation  in the sowing of oat and rye seeds, depending on the angle of the distribution head deviation from the vertical position (iα) and the diffuser variant—the configuration and number of diffusion rings (ip) were analyzed statistically, including analysis of variance (ANOVA). The aim of the analysis was to compare the average values of the coefficient of variation (CV), which was used as a sowing evenness indicator, at different combinations of independent variables (iα) and (ip). If there was a statistically significant difference between the average values of the coefficient of variation, post hoc tests were carried out. The Statistica v. 13 PL software package was used for calculations. The level of significance α = 0.05 was assumed in the analysis and inference.The results of measurements of the coefficient of variation (ip) and the distribution head angle of deviation from the vertical position (iα) it was important to answer the question of whether the seed sowing evenness measured with the coefficient of variation (CV) did not differ significantly depending on the assumed parameters of independent variables, i.e., the position and number of diffusion rings (ip) and the three angles of the distribution head deviation from the vertical position (iα). Therefore, analysis of variance (ANOVA) was applied to consider the null hypotheses H0 that the mean coefficients of variation (CV) were equal and the alternative hypotheses H1 that the mean coefficients of variation were not equal. The significance level of the statistical analysis was α = 0.05.When assessing the configurations of the diffuser  in the vertical distribution head variant were significantly different from the average values in the variant where the head was tilted from the vertical position at an angle of 10°. The analysis showed that when the head deviated from the vertical position at an angle of 10°, the seed sowing evenness (even distribution of the seed-and-air stream in the distribution head) deteriorated and the value of the coefficient of variation (CV) increased by almost 31% from 10.36%  to 13.55% . Yatskul et al. [As far as the oat seeds are concerned, the null hypothesis Hhesis H1 . As a rel et al.  observed0, according to which the value of the coefficient of variation for the first independent variable assumed in the study  was equal , the analysis of variance showed that null hypotheses H0 about equal values of the mean coefficient of variation (CV) must be rejected in favor of alternative hypotheses H1 for both oat and rye seeds. Even when only one diffusion ring was used in the diffuser tube, both the rye and oat seeds were sown more evenly than in the diffuser with a smooth internal surface. The research results were compatible with the results of tests conducted on wheat seeds by Gierz and Kęska [p4–p6 with three diffusion rings in different configurations (p6). This regularity was observed when both rye and oat seeds were sown. The average values of the coefficient of variation were 5.31% and 4.62%, respectively. As was expected, the distribution of the seed-and-air stream in the head with a smooth tube (variant p1) resulted in considerable seed sowing unevenness. The average values of the coefficient of variation (CV) were 16.68% for oat seeds and 15.94% for rye seeds (CV) also showed considerable sowing unevenness, which negatively affects the yield, as was indicated in reference publications [p1-p3 with a smooth inner surface of the diffuser tube and with one or two diffusion rings  differed significantly depending on the seed species. One-way analysis of variance (ANOVA) was applied with null hypothesis H0 that the mean values of the coefficient of variation (CV) were equal and alternative hypothesis H1 that the mean values of the coefficient of variation were not equal. The analysis of variance  for rye seeds (CV = 7.99%) was significantly lower, i.e., by nearly 34%  than the mean value of the coefficient of variation for oat seeds (CV = 12.05%).Further statistical analysis involved answering the question of whether the mean values of the coefficient of variation  on the precision of the distribution of the stream of rye and oat seeds, which have different physical characteristics. The research showed that the angle of the seed drill tilt resulting from the terrain, which was simulated in the tests by changing the angle of the distribution head deviation from the vertical position within 0-10°, significantly affected only the oat seeds sowing quality. When the distribution head deviated from the vertical position by 10°, the seed sowing quality deteriorated. This effect was reflected by the value of the coefficient of variation , regardless of the diffuser variant, i.e., the number and configuration of the diffusion rings. The tests conducted on the rye seeds showed that the difference between the mean values of the coefficient of variation depending on the angle of the distribution head deviation from the vertical position was not significant and the value of the coefficient of variation ranged from 7.32% to 8.49%.p6). This regularity was observed when both oat and rye seeds were sown. The mean values of the coefficient of variation were 5.31% and 4.62%, respectively. As expected, when a smooth pipe (variant p1) was used before the head, the distribution of the seed-and-air stream resulted in high sowing unevenness. The mean values of the coefficient of variation (CV) for the sowing of oat and rye seeds were 16.68% and 15.94%, respectively. As far as the second variable, i.e., the diffuser variant is concerned, the research showed that in comparison with the configuration with the smooth inner surface of the diffuser tube, the installation of one diffusion ring in the tube improved the evenness of sowing both oat and rye seeds. Further analysis of the test results showed that the positioning of the diffusion rings in the lower section of the diffuser (close to the supply elbow) was the most effective configuration (test variant Further research should be conducted to construct a shorter diffuser and thus reduce the dimensions of the distribution head. Rapid prototyping and 3D printing technologies are the best methods for this purpose ,39. Ther


To describe quality control procedures and baseline values of electroretinography (ERG), kinetic and static perimetry, color discrimination, and best-corrected visual acuity from a multicenter ocular safety study.A multicenter prospective longitudinal randomized placebo-controlled study was conducted at 11 ophthalmic centers that had received certification following training, instruction, and monitoring. ERGs were obtained with the Espion E2 Ganzfeld console, perimetry with the Octopus 101 perimeter, color discrimination with the Lanthony desaturated D15 test, and best-corrected visual acuity with the Early Treatment Diabetic Retinopathy Study chart. Ophthalmic eligibility required satisfactory outcomes for ERG and perimetry by the second or third pre-inclusion attempts, respectively. Quality control for the ERG was undertaken by two central readers.The mean (SD) age of the 97 individuals was 63.5 (7.9) range, 44–83 years. The overall coefficients of variation (CVs) for the ERG peak times were less than those of the only comparable single-center study. The CV for the mean defect of standard automated perimetry was approximately one-third that of the Ocular Hypertension Treatment Study. With increasing age, ERG peak times and color discrimination Total Error Score increased while ERG amplitudes and isopter area all decreased.The data illustrate the benefit of identical equipment, stringent on-site instruction and training, quality control, certification, and validation methods. The latter are recommended for planning and conducting multicenter trials using ERG and perimetry to monitor safety and/or efficacy of treatment intervention.Stringent quality control procedures and reliable reference values are indispensable prerequisites for informative clinical trials. The comparison of a given measure of structural or functional integrity to those from a corresponding and representative distribution of age-corrected normal values has become commonplace in ophthalmic practice. Abnormality is defined, statistically, in terms of the given measure lying beyond the range of corresponding normal values. The likelihood of detecting an abnormality is, therefore, dependent upon the magnitude of the variability associated with the measurement itself and upon the between-individual variability in normal individuals. Similarly, the time point at which a worsening of any given measure can be identified  is dependent upon the magnitude of the corresponding within- and between-test variability. The recording conditions for some diagnostic tests  are relatively constant such that a database of normative values can be incorporated into the instrument. However, the outcome for visual electrophysiology is highly influenced by the recording conditions and necessitates a database of normal values for each individual center, acquired using standardized protocols and operating procedures.–Current clinical trials generally recruit participants from multiple centers to minimize the impact of data collection on already overburdened clinics and/or due to the low prevalence of the particular disease. Such a multicenter approach requires standardized acquisition protocols and stringent quality control of the data to obtain the sensitive and specific endpoints required for safety and/or efficacy trials of therapeutic interventions. The quality control for trials in which perimetry is the primary endpoint has long been documented and involves site visits, study manuals, and training programs, accompanied by qualifying assessments and certification procedures for appropriate clinic personnel.The purpose of the current report is twofold: first, to describe procedures to promote the acquisition of high-quality data  and, second, to describe the pre-treatment baseline values derived by each investigative technique. The latter is advantageous in that normal values of visual function for the ages of the individuals in the study have received little attention.f), ivabradine, in patients with chronic stable angina pectoris who were receiving standard background anti-angina therapy (EudraCT No. 2006-005475-17). The primary objective of the trial, which was requested by the European Medicines Agency, was to “document further the long-term ocular safety of ivabradine.” The primary endpoint was to assess by ERG the expected pharmacologic effect of the If inhibitor on the corresponding retinal current, Ih, generated by the hyperpolarization-activated cyclic nucleotide-gated cation channels–The study underlying the pre-treatment baseline values presented here was a multicenter, international, prospective, double-blind, randomized placebo-controlled trial of a selective inhibitor of the cardiac pacemaker current  consisting of two experts in ocular electrophysiology and two experts in perimetry.The local ophthalmologist investigator and the technicians at each of the 11 centers received 2 days of expert face-to-face hands-on instruction in the study protocol and in the uploading of the data into the central database. At a later date and before the enrollment phase, each ophthalmologic center was required to complete a certification procedure for both ERG and perimetry to the satisfaction of the respective experts of the SOSC who were masked to the center. The certification procedure required technically satisfactory outcomes for each of three ERG recordings, assessed by experts in ERG, as well as three peripheral and three central visual field (VF) examinations, assessed by experts in perimetry , together with a successful electronic transmission of the results to the central database see  and 5. IPotential participants initially attended a pre-inclusion visit for cardiovascular examination by the main investigator, the local cardiologist. The principal cardiac eligibility criteria comprised chronic stable angina pectoris treated with standard background antiangina therapy and a heart rate of at least 60 bpm. There was no age limitation. Medical exclusion criteria comprised renal insufficiency, severe hepatic impairment, severe hypotension, and unstable chronic angina.Prior to inclusion in the study, the potential individuals then underwent, at the corresponding ophthalmology center and within 10 days of the cardiovascular examination, an ophthalmologic examination including slit-lamp biomicroscopy of the anterior segment, tonometry, ophthalmoscopy, and fundus photography. They subsequently underwent, at the same visit, ERG recording, static and kinetic perimetry, and color vision testing . Those wThe ophthalmic exclusion criteria comprised a BCVA of worse than 0.5 in either eye; previous intraocular surgery (other than longstanding uncomplicated cataract extraction with posterior chamber lens implantation); spherical ametropia exceeding ±5.00 diopters, respectively, in either eye; astigmatism exceeding 3.00 diopters in either eye; intraocular pressure exceeding 25 mm Hg in either eye, if associated with glaucomatous damage to the optic nerve head and/or a visual field defect characteristic of primary open-angle glaucoma; angle-closure glaucoma; proliferative diabetic retinopathy; macular edema; history of unexplained visual field loss; progressive optic nerve, retinal, or choroidal, disease other than that due to age; and concomitant medical therapy known to have an adverse effect on retinal function.BCVA was measured at 4 m using the Early Treatment Diabetic Retinopathy Study (ETDRS) chart  and was recorded in decimals. The BCVA was entered into the electronic case report form (e-CRF) as a decimal value and automatically converted into logarithm of the minimum angle of resolution (logMAR) value.https://www.torok.info/colorvision/d15.htm, which identifies entry errors and automatically calculates the Total Error Score (TES).Color vision discrimination was measured with the Lanthony D15 desaturated color vision test  performed under a constant illuminance of 270 lux white light (D 65 standard illuminant) within a Standard Light Box . The sequence of the caps was entered into software–1. The blind spot was defined by presentation of the I4e stimulus at 2° s–1 starting from its presumed center along each 30° meridian. The area of the blind spot was automatically calculated by the perimeter. Each isopter was corrected for the reaction time of the given individual, which was calculated from each of three reaction time vectors placed within normal regions of the central fieldPerimetry was undertaken using the Octopus 101 perimeter . The peripheral visual field was examined by semiautomated kinetic perimetry  using the III4e and I3e Goldmann stimuli presented randomly along each 15° meridian at an angular velocity of 3° sThe central field was assessed by standard (static) automated perimetry  using Program G1 and stimulus size III and a 4-2-1 dB threshold strategy, with the appropriate near correction in situ. The sensitivity at each individual stimulus location at the immediately preceding visit was used as the starting value for the staircase of the subsequent visit to reduce the number of stimulus presentations prior to the first reversal and, therefore, mitigate against the perimetric fatigue effect,The peripheral field was assessed before the central field. The right eye was examined before the left eye for each perimetric modality. A 5- to 10-minute rest period was given between the two examinations.The standard printout from each type of perimetry for each individual at each visit was stored in a web-based electronic database specifically designed for the study. In addition, the database separately stored the mean reaction time, the reaction time–corrected area for each of the two isopters and for the blind spot, the number of incorrect responses to the false-negative and false-positive catch trials, the magnitude of the Mean Defect (MD) index, the BCVA, and the refractive correction. The outcomes in each eye for the peripheral and central field examinations comprised the reaction time–corrected areal extent of each isopter and the MD index, respectively.2 Electrophysiology Consoles  and single-use Dawson-Trick-Litzkow (DTL) fiber electrodes−2  rod ERG (DA 0.01), the 3.0 cd·s·m−2  combined rod-cone standard flash ERG (DA 3.0), and the 12 cd·s·m−2  strong flash ERG (DA 12.0). The photopic ERGs comprised the light-adapted (LA) 3.0 cd·s·m−2  standard-flash “cone” ERG (LA 3.0) and the light-adapted 30-Hz flicker ERG (LA 3.0 flicker) and were recorded after a 10-minute software-controlled light adaptation to a background white light of 34 cd·m−2 in the Ganzfeld bowl. The recording technician ensured that the eyes remained open throughout the light adaptation period by observation of the eyes via a camera built into the Ganzfeld bowl  corrected for an individual reaction time of between 200 and 1500 ms, the presence of ellipsoid-shaped isopters of appropriate area and angular extent, and the absence of any crossing of isopters. The area in square degrees was automatically calculated by the perimeter software. For standard automated perimetry, the quality control comprised verification that the incorrect responses to the false-positive and to the false-negative catch trials were each less than 30%.The study design did not involve test-retest variability of each variable. Test-retest variability is a function of the magnitude of the “true” value. The determination of the test-retest variability across the entire range of parameters was beyond the scope of the study. Instead, test precision of each ERG recording was controlled throughout the entire study by central readers, and that for perimetry was assessed in terms of the area of the blind spot, the reaction time, and the response to the false-positive and false-negative catch trials.The e-CRF was uploaded to the study database and backed up by hardcopy. All data modifications were recorded in chronologic order using the audit trail feature of the INFORM and CLINTRIAL software. Monitoring procedures ensured that all data in the e-CRF were complete. A careful masked review of possible data entry errors was performed by double entry of the data, and any issues were resolved prior to the locking of the study database.The analysis for each parameter, at the pre-treatment baseline, was undertaken in terms of measures of central tendency and dispersion for the cohort, as a whole, and then in terms of three age groups: <60 years, 60 to 69 years, and ≥70 years.The study followed the tenets of the Declaration of Helsinki, 1964, and subsequent revisions. The study commenced only after approval had been obtained from the appropriate ethics committee for each participating center. Informed consent was obtained from each individual following an explanation of the purpose of the study and any possible consequences. Protocol amendments to the study protocol were approved by each of the ethics committees.The pre-treatment baseline values, described here, comprised the outcome of the pre-inclusion visit for BCVA and color vision and of the respective visits at which a reliable measure of ERG and each type of perimetry was obtained .Of the 190 individuals evaluated by the local cardiologists, 171 were selected for potential enrollment in the study; of these, 141 performed at least one ERG test and 130 performed at least one type of perimetry. A total of 102 individuals satisfactorily completed the ERG and both types of perimetry.Four of the 102 individuals were subsequently excluded as they were found, prior to enrollment, not to have met either the cardiac or other medical inclusion criteria (three with a heart rate below 60 bpm and one with severe hepatic impairment). In addition, one individual attended for the visual function tests beyond the timeframe specified by the study protocol. The number of individuals undertaking the visual function tests, as well as the number satisfactorily completing the tests, by visit, is given in Most (58.8%) of the 97 individuals were male, and most (88.7%) were Caucasian (4.1% were Asian and 7.2% were of other ethnicity). The mean (SD) age was 63.5  years. Twenty-nine individuals were aged less than 60 years, 47 between 60 and 69 years, and 21 greater than or equal to 70 years of age.All females were of nonchildbearing potential due to menopause, hysterectomy, or sterilization with the exception of one individual who received effective contraception. Thirteen individuals were current smokers with a mean (SD) tobacco consumption of 14.8 (9.9) cigarettes per day; 46 were previous smokers.Nine individuals presented with an age-related cataract, two with age-related macular degeneration, and two with a retinal hemorrhage. One individual reported a history of an unspecified eye injury, the type of which was not documented by the investigator. However, the nature of these disorders was such that each of the individuals met the ophthalmologic eligibility criteria.All but one individual had relevant events in their medical history. The most frequent were disorders of metabolism/nutrition and of the vascular and cardiac systems, which accounted for 85, 83, and 51 individuals, respectively. Of the 85 individuals with metabolic/nutritional disorders, 45.9% had dyslipidemia, 25.9% had diabetes mellitus (either type 1 or type 2), and 10.6% had hyperlipidemia. None of those with diabetes exhibited diabetic retinopathy. Of the 83 with vascular disorders, 97.6% had hypertension, 76.2% had varicose veins, and 6.1% had peripheral arterial occlusive disease. Of the 51 with cardiac disorders, 35.4% had coronary artery disease and 33.3% had myocardial infarction.A history of a surgical or medical procedure was reported by 64 of the 97 individuals. The most frequent procedure was coronary angioplasty (13.4%). Antithrombotics had been prescribed for 94.8% of the individuals, lipid-modifying agents for 84.5%, agents acting on the renin-angiotensin system for 74.2%, beta-blockers for 73.2%, and cardiac therapy for 71.1% .The analysis of the ERG was undertaken on 95 of the 97 individuals. The remaining two individuals were excluded on the basis of unreliable baseline ERGs. Twenty-nine of the 95 individuals were aged less than 60 years, 47 between 60 and 69 years, and 19 greater than or equal to 70 years of age. The male/female ratio of these 95 individuals was 55:40.The summary statistics for the distributions in each eye at baseline of the dark- and light-adapted ERG a- and b-wave amplitudes and peak times for the 95 individuals are given in The summary statistics in each eye for the distributions at baseline of the dark- and light-adapted ERG a- and b-wave amplitudes and peak times, averaged across the two eyes for the 95 individuals as a whole and substratified by age group, are given in The descriptive statistics for the distributions in each eye at baseline of the BCVA, the TES, the areal extents of the III4e and I3e isopters, and the MD index for the 97 individuals are illustrated in There was no obvious difference between the three age groups in either eye for the BCVA or the MD index. The TES and the areal extents of the I3e and III4e isopters each declined with increase in age for each eye. The summary statistics for the 97 individuals in each eye for the distributions at baseline of the BCVA, the TES of the Lanthony desaturated D15 test, the MD index, and the areal extents of the III4e and I3e isopters, for the group as a whole and by age, are given in The summary statistics for the distributions of the ERG, the BCVA, color vision, and perimetry  for the whole group and for the three centers at which more than 15 individuals were enrolled .electroretinography. Of these, 164 are ophthalmologic trials of which 110 use the Ganzfeld ERG, but only 24 are multicenter trials with more than 2 sites. Of these 24 multicenter trials, 14 involve more than 6 sites, and 4 of 14 involve more than 12 sites. The topics and the registration dates suggest an increase of the use of ERGs in multicenter trials involving rare eye diseases.The ERG as an objective marker for changes in retinal function is a mainstay in testing certain drug products,The current standard for the recording of the ERG is mandated by the International Society for Clinical Electrophysiology of Vision (ISCEV) with the aim of ensuring compatibility across centers.The variances, expressed in terms of the CV, associated with the ERG peak times for the group as a whole and for each of the three centers that had enrolled more than 15 individuals  were allIn the current study, the distributions of the ERG amplitude values were wider than those of the ERG peak times. This finding is compatible with that of the single-center study.The global CVs for the amplitudes were compatible with those from a similar multicenter study–The increase in peak time and the reduction in amplitude with increasing age for both the dark- and the light-adapted ERGs are compatible with that of previous studies.The size of the natural pupil and also of that under mydriasis reduces with increasing age.Best-corrected visual acuity testing is highly standardized through the ETDRS proceduresThe distributions of the TES, the MD index, and the III4e isopter area in the majority of individuals  for the equivalent MD index, combined from two eligible baseline fields and taken across the two eyes in the Ocular Hypertension Treatment Study (OHTS).–The CVs for the baseline MD index in the current study were 124% in the right eye and 144% in the left eye, and both were better than that of 438%  would have been that of the loss variance (LV) index. This index is corrected for age, removes the loss expressed by the MD index, and is indicative of nonuniform  loss. However, the use of the LV in the current study was considered inappropriate since it would have been insensitive to any possible generalized/uniform retinal dysfunction that was the emphasis of the study.The BCVA did not exhibit the previously reported age-related decline.The age-related decline in the TES was higher for the oldest age group compared to the youngest age group and is compatible with that found previously.The MD index, as would be expected, did not vary with age in either eye since the index represents the mean, across all locations within the central field, of the difference between the age-corrected normal value and the corresponding measured value.The study used Program G1, which has more paracentral stimulus locations compared to the conventional Humphrey Field Analyzer that uses the Central 24-2 or 30-2 threshold tests or even the newly introduced Central 24-C threshold test. Program G1 is, therefore, more sensitive in detecting potential foveal and parafoveal abnormalities occurring in age-related retinal changes.,,The age-related decline in the areal extent of the reaction time–corrected I3e and III4e isopters is consistent with that reported for both manual and semiautomated kinetic perimetry.–The cohort included some individuals with moderate age-related cataract and/or other ophthalmologic conditions common in advanced age to the extent that they were not considered an exclusion criterion. The presence of moderate age-related cataract does not affect either the peak time or the amplitude of the Ganzfeld ERGThe data presented here from an international multicenter study illustrate the benefit of identical equipment, stringent on-site instruction and training, and, for ERG, the quality control and timely feedback to investigators by a centralized procedure involving highly experienced central readers providing consistency of interpretation. The data sets, together with the study protocols for instruction and training, for quality control and validation, and for measurement acquisition, may be useful in planning ophthalmologic multicenter studies in which electrophysiologic and visual function testing are used to monitor safety and/or efficacy.


Lumbar spinal stenosis (LSS) is a common disease in the elderly population; it has been reported that patients with LSS have an abnormal gait pattern due to symptom such as neurogenic intermittent claudication (NIC); however, no detailed reports exist on the plantar pressure distributions in LSS patients with NIC. To analysis the plantar pressure characteristics of LSS patients, the Footscan® pressure system was used to perform dynamic plantar pressure measurements in 20 LSS patients  before and after the occurrence of NIC. The contact time (CT), foot progression angle (FPA), pressure-time integral (PTI), and contact area (CA) were collected and compared between the LSS patients and age-matched healthy subjects in each measurement. The LSS group showed an increase in forefoot CT%, PTI, and CA% in both measurements compared with those in the control group. After the occurrence of NIC in the LSS group, CT%, PTI, and CA% of the forefoot increased further compared with those before the occurrence of NIC. In addition, after the occurrence of NIC, the PTI and CA% of the forefoot shifted from the medial foot to the lateral foot. The results suggested that the plantar pressure distributions of patients with LSS differs from normal subjects due to the posture of waking with lumbar forward flexion, and the forefoot bears a higher relative load. In addition, the occurrence of NIC could affect the plantar pressure distribution of the patients with LSS, predicting the patient's risk of falling to the anterior direction and to the symptomatic side. Lumbar spinal stenosis (LSS) refers to the nerve compression syndrome, in which the spinal canal narrows and compresses the dural sac, spinal cord, or nerve root . The prePatients with LSS usually seek medical treatment because of walking disorders. The poor walking ability indicates severe compression of the spinal cord and nerve. Therefore, assessing the patient's walking function is essential for the diagnosis and treatment of LSS. Many recent studies investigated the gait patterns of patients with LSS. The findings revealed that the walking patterns of patients with LSS were different from those of ordinary subjects, mainly manifested by wide-based gait, increased gait variability, and balance disturbances –11. In aThe changes in gait can probably affect the pressure distribution under the foot . As an iThis observational study is a cross-sectional, uncontrolled intervention. From October 2017 to April 2019, patients with LSS in our institution were routinely analyzed for plantar pressure after admission to improve the database of plantar pressure for patients with LSS. The database was reviewed, and the case group was selected. The inclusion criteria were as follows: (1) L4–L5 level spinal stenosis on imaging examination , 14 and 2, and the sampling frequency was 125 Hz. Before each measurement, the test system was calibrated. The force plate was located at the center of a carpet with the same external dimension to provide a “complete platform,” 4 m in length, to ensure that a minimum of three steps was taken before data collection. The platform was disguised with a thin liner of EVA (ethylene-vinyl acetate copolymer) material to avoid targeting effect [Data were collected using the Footscan® 3D pressure system , which has been proved to have good reliability and repeatability . The sizg effect   of each anatomical structure: (1) initial contact phase (ICP), (2) forefoot contact phase (FFCP), (3) foot flat phase (FFP), and (4) forefoot push-off phase (FFPOP) .The following plantar pressure parameters were collected using the software: CT in each subphase, contact area (CA) in each zone, pressure-time integral (PTI) in each zone, and foot progression angle (FPA). Among these, CA was corrected by the proportion of each area in the total plantar area (CA%), and CT was corrected by the proportion of each subphase in the total standing phase of one foot (CT%). The average of each parameter in the three valid data was used as the analysis data of each participant. The data were divided into four groups: first measurement in the LSS group, second measurement in the LSS group, first measurement in the control group, and second measurement in the control group.n = 3; control group, n = 3). The G∗power software (Version 3.1.9.6) was used to calculate the required sample size affording a significance level of 0.05, a power of 0.95, and an effect size of 0.65 . The required sample size is 28 subjects .The sample size was determined by a pilot study  were included in the experimental group (LSS group), aged 56–73 years, with an average age of (69.5 ± 7.2) years. Five cases of relatively narrow L4–L5 level were found on imaging 15 cases with absolute stenosis [The comparison results of CT% and total CT in the stance phase of each group are shown in The comparison results of the PTI in each region of the plantar with two measurements are summarized in Regarding the proportion of CA in each area, the control group had no statistically significant difference between the two measurements. Compared with the control group, the CA% in the first measurement results of the LSS group in the M1 and M2 areas increased. In the second measurement results, the CA% significantly increased in the T1, T2–T5, and M1–M4 areas and significantly reduced in the MH and LH areas. The comparison of the CA% of the two measurements in the LSS group showed that the results of the second measurement presented a significant increase in the CA% of the T1, T2–T5, and M1–M4 regions and a significant decrease in the CA% of the MH and LH regions .Overall, the LSS group showed an increase in forefoot CT%, PTI, and CA% in both measurements compared with those in the control group. After the occurrence of NIC in the LSS group, CT%, PTI, and CA% of the forefoot increased further compared with those before the occurrence of NIC. In addition, after the occurrence of NIC symptoms, the PTI and CA% of the forefoot shifted from the medial foot to the lateral foot.LSS is a common and disabling disease in the population over the age of 60 . The patIn the gait analysis study of patients with LSS by Garbelotti et al. , patientIn this study, irrespective of the occurrence of NIC, the FPA was larger in the LSS group compared with the control group, and the foot was more externally rotated when walking. FPA referred to the angle between the longitudinal axis of one foot and the walking direction, and its outward rotation indicated that the patient had an “out-toe” gait when walking . PreviouMarte et al.  and Lai Impaired balance in patients with LSS has been demonstrated in multiple studies. Aleksandra et al.  and ElisThis study had some limitations. Only the plantar pressure analysis was performed on patients with L4–L5 level spinal canal stenosis, considering this to be more common in clinic , 2, compIn summary, plantar pressure tests were conducted before and after the occurrence of NIC in patients with LSS, and the results were compared with those in healthy adults in this study. The results revealed the following differences in the distribution of plantar pressure: (1) patients with LSS could present the posture of the lumbar forward flexion when walking. As a result, the center of gravity moved in the anterior direction compared with the healthy subjects, increasing the CT and loading of the forefoot. The forefoot might have a higher risk of strain disease or overuse injury. (2) The occurrence of NIC could affect the plantar pressure distribution of the patients with LSS, predicting the patient's risk of falling to the anterior direction and to the symptomatic side. Future gait analysis studies should focus on investigating the changes in plantar pressure distribution after the occurrence of NIC in patients with LSS and correlate them with patients' walking functions, such as the maximum walking distance or the level of balance function. It is promising to provide a new objectively method for evaluating the walking capabilities of patients with LSS.