Pleurodeles waltl adult newts’ eyes were used as a model biological target. It was shown that a statistically reliable protective effect on the state of the sclera, vascular membrane and retinal pigment epithelium, as well as on the viability of fibroblasts, was inherent in the proteinaceous cryogels loaded with the peptide bioregulator (Viophtan-5™) isolated from the bovine eye sclera.Wide-pore proteinaceous freeze–thaw spongy gels were synthesized via the cryotropic gelation technique using the bovine blood serum or its diluted solutions as the protein-containing precursors. The feed systems also included the denaturant (urea) and the thiol-reductant (cysteine). The gel-fraction yield decreased and the swelling degree of the walls of macropores in such heterophase matrices increased with decreasing the initial protein concentration. The optimum freezing temperature was found to be within a rather narrow range from −15 to −20 °C. In this case, the average size of the macropores in the resultant cryogels was 90–110 μm. The suitability of such soft wide-pore gel materials for the application as the carriers of peptide bioregulators was demonstrated in the in vitro experiments, when the posterior segments of the  A large number of various gel materials based on substances of a protein nature were used for a long time and are currently employed for biomedical purposes ,5,6,7,8.(i) by the 3D coupling of the protein macromolecules with the aid of auxiliary cross-linking reagents added to the precursor solution directly prior to its cryogenic processing ,30,31,34(ii) by inducing the unfolding of the protein globules with simultaneous interchain cross-linking through the thiol–disulfide exchange reactions, the process also caused by the denaturants introduced into the feed system before its freeze–thaw treatment ,33,36,38In the latter case, no foreign inclusions are inserted into the chemical structure of the resultant cryogels that consist only of the amino acid monomeric units, and the covalent nodes within the 3D network are disulfide bridges, i.e., cystine-belonging structures . TherefoThe possibility to implement similar cryogels as the implantable delivery carriers of special biologically-active proteins and peptides is of independent significance since the latter compounds are used for the treatment of various diseases, among which are cancer, diabetes, bone fracture, orthopedic problems, etc. ,41. Of tTherefore, it was of interest and of importance to also reveal the possibilities of other types of blood-protein-derived cryogels to serve as carriers for various peptide bioregulators with respect not only to bone tissue repair, but also for the induction of the regeneration of other biological tissues. The elucidation of this problem was the general goal of the present study.To this end, sponge-like proteinaceous cryogels were prepared, originating from the total proteins of bovine blood serum; then, some physico–chemical characteristics of such materials and their macroporous morphology were evaluated followed by loading of the cryogels with the bioregulators isolated either from the serum of bovine blood  or from Y) were used as the indicators of the gelation efficiency. The values of the swelling extent (Sw/w) were measured as indicators of the cross-linking “level” of the 3D network within the polymeric phase  for these heterophase gel matrices, since the lower is such swelling, the higher is the specific amount of the cross-links inside this phase [The wide-pore cryogels based on the blood serum proteins were prepared by a procedure similar to the method we applied earlier for the synthesis of the individual protein-derived  cryogels ,38. As wis phase .Y values were very small, especially for the systems with the protein concentration of 50.0 and 32.5 mg/mL. The diagrams in The choice of the cryogenic processing temperature interval was stipulated by the following reasons. At the negative temperatures as high as −15 °C, the feed solutions did very frequently not freeze at all because of the supercooling effects. In turn, when the process was carried out at the temperatures as low as −25 °C, the Y values. Over the concentration ranges of the protein precursors used in this study, i.e., 37.5–75.0 mg/mL, and 30–50 mg/mL for the individual serum albumin , the diSw/w values of the equi-concentrated samples formed at −15 and −20 °C were very close, whereas the pore walls in the spongy samples prepared at −25 °C swelled considerably stronger in comparison with the former ones , 101.4 ± 13.2 μm (b) and 95.0 ± 11.4 μm (c), i.e., it was a normal trend: at a lower freezing temperature somewhat smaller pores were formed inside the cryogel’s bulk. Taking into account the data on the gel-fraction yield  that contain the relevant precursors ,52,53,54on yield  and swelon yield  in combion yield , one canSince the character of these dependences is virtually the same as for the cryogels based on individual serum albumin , which iHowever, what about the other protein components of the initial blood serum?In order to clarify this problem, we analyzed, via the gel-electrophoresis technique, the composition of the respective cryogels after their dissolution in the sodium dodecyl sulfate/dithiotreitol medium see . The resLarge amounts of different proteins are well-known to constitute in the blood serum composition, the major fraction being albumins; in several times smaller amounts various globulins are present; other proteinaceous components are present in minor fractions ,57,58. DIt was found that not only albumin polypeptide chains, but also those belonging to certain other proteins of the blood serum  were built in the spatial network of the proteinaceous cryogels formed in frozen systems containing a sum of serum proteins, denaturant (urea) and thiol reductant (cysteine). Of course, In the Introduction, it was indicated that the wide-pore proteinaceous cryogels could be of applied biomedical interest as biocompatible delivery carriers for various peptide/protein bioregulators. Therefore, in order to confirm this statement we carried our certain biotesting experiments, in which the blood-serum-proteins-derived cryogels were used as such carriers, while the commercial biological products Viophtan-1™ and Viophtan-5™ were employed as the peptide bioregulators see , and theThe following changes in the state of tissues and cells of the posterior segment of the newt’s eye were observed in the course of culturing of these systems that were subdivided in to six experimental groups indicated in (i) Reference samples from Group 1 a:r) from the retinal pigment epithelium (pe) layer and the detachment of this layer from the vascular membrane occurred. In the layer of the retinal pigment epithelium itself, the pigment shifted to the apical side thus indicating the cells’ instability within this layer and their de-differentiation. The degradation and damage of neurons in the retina were also observed. The signs of the beginning of tissue degradation in the sclera were detected. The latter changes were expressed in the stratification of collagen fibers with the formation of large cavities (c) between them, as well as in a decrease in the number of fibroblasts (f) per a square unit of the microscopy image (1 in When the newt eye segments were incubated into the serum-free culture medium without any foreign additives and enclosures (spongy cryogels), both the detachment of the retina (age 1 in . These d(ii) Reference samples from Group 2 b:r) from the retinal pigment epithelium (pe) layer also occurred, the outer segments of photoreceptor cells and other retinal neurons were less damaged than those in the samples of Group 1. The pigment in the retinal pigment epithelium layer also tended to shift to the apical side, but not so pronouncedly as for the Group 1 samples. The vascular shell was dense. In the sclera, there were also the elements of tissue degradation that were exhibited in the stratification of the collagen fibers and the formation of cavities (c), as well as in a decrease in the number  pattern was observed in comparison to the samples of Group 1. Although the detachment of the retina (ber 2 in  of fibro(iii) Reference samples from Group 3 c:r) from the retinal pigment epithelium (pe) was observed as well, and the pigment shifted in the retinal pigment epithelium (pe) layer to the apical side. The vascular shell was dense without any signs of damage. The exhibition of the tissue degradation was detected in the sclera to a lesser extent than for the samples from Groups 1 and 2. This effect was expressed in a smaller size of the cavities (c) between the collagen fibers (f), as well as in a larger number of fibroblasts  Experimental samples from Group 4 d:r) from the retinal pigment epithelium (pe) was also observed, and the pigment in the retinal pigment epithelium layer was also shifted to the apical side. The vascular shell was in a good condition, dense, without signs of degradation. In the sclera, the elements of tissue degradation were observed being expressed in the stratification of collagen fibers and in the formation of cavities (c). The number of fibroblasts (f) turned out to be higher (by about 1.5-fold) compared to the reference samples from Groups 1–3  Reference samples from Group 5 e:r) from the retinal pigment epithelium (pe) layer was practically not observed throughout the posterior part of the eye; only minor detachments were visible in some areas. The pigment in the layer of the retinal pigment epithelium did not shift to the apical side of the cells and was distributed evenly and compactly in the cells of the retinal pigment epithelium. Such a result indicates a stable state of the cellular differentiation of these cells. The vascular shell was preserved and dense, without signs of degradation. In the sclera, there were no pronounced changes in tissue degradation, as was detected for the samples in Groups 1–4. The collagen fibers were compactly located with no formation of large cavities (c). The number of fibroblasts  Experimental samples from the Group 6 f:r) from the retinal pigment epithelium (pe) layer was registered, while the retinal pigment epithelium layer itself was not detached from the vascular membrane. Pigment displacement in the retinal pigment epithelium layer was not virtually observed, thus indicating the stabilization of the differentiated state of cells in this layer. The sclera contained minor degradation elements, namely, minor cavities (c) and stratification of collagen fibers. These effects were less pronounced than in the reference samples from the Groups 1–3 and in the experimental samples from the Group 4, which contained a blood serum bioregulator. At the same time, the effects were more pronounced than for the reference samples belonging to the Group 5. The vascular shell was smooth without pronounced elements of tissue degradation. The amount of fibroblasts (f) was higher than in all other groups and approximately twice as large compared to reference Group 1. The positive effect of the Vioftan-5-loaded cryogel should be noted, since the statistically significant number of fibroblasts per unit area was found. The amount of these cells serves as a quantitative indicator, and the condition of tissues at a qualitative level, especially the scleral membrane, did not differ much in Groups 5 and 6, but was significantly better than in all the other groups. The cultivation process is an unfavorable environment in which fibroblasts gradually die over time. The more fibroblasts observed in the sclera during cultivation, the more factors added to the culture medium have the effect of maintaining the viability of fibroblasts. Therefore, we concluded that the combined composition of cryogel and bioregulator has a positive effect based on the quantitative criterion because the fibroblasts in the sclera play a key role in maintaining the metabolism and synthesis of collagen fibers that give strength to the scleral membrane. Hence, these data indicate the ability of the Vioftan-5-loaded spongy proteinaceous cryogel composite systems to prevent the development of degenerative processes in the sclera membrane and to maintain adhesive interactions between the sclera and adjacent tissues.In the case of the newt eye segment incubation onto the spongy cryogel support loaded with the Viophtan-5 bioregulator, the following histological picture was observed. Some minor detachment of retina ; bioregulators Viophtan-1™ (source—bovine blood serum) and Viophtan-5™ (source—sclera of bovine eyes) ; Medium 199 ; urea , cysteine, eosin, hematoxylin ; methylene blue ; sodium dodecyl sulfate (SDS) and Coomassie R250 dye ; 1,4-dithiotreitol (DTT), xylene and acetone ; ethyl alcohol . All aqueous solutions were prepared using Milli-Q quality water.The target proteinaceous cryogels were prepared using either total bovine blood serum with a sum protein concentration of 75.0 mg/mL or the solutions formed after the serum dilution with water up to the following protein concentrations: 62.5, 50.0 and 37.5 mg/mL. Then, the required amount of urea was added to each solution in order to reach a urea concentration of 1.5 mol/L; the solutions were cooled in an ice bath, followed by the dissolution of the required amount of the cysteine to reach a concentration of 0.01 mol/L. The reaction mixture thus prepared was poured in 1.5-mL portions into plastic Petri dishes  that were sealed and placed in the chamber of a programmable cryostat F-32 ME  with a pre-set sub-zero temperature, where the samples were incubated for 24 h. The samples were then removed from the cryostat, thawed for 30 min followed by rinsing from the sol-fraction in pure water (4 × 50 mL per a sample).The gel-fraction yield and the degree of swelling of cryogels based on serum proteins were measured gravimetrically as follows. To do this, a spongy sample swollen in water was placed on a glass filter and the free solvent was removed with a water pump vacuum for 1 min under a load of 170 g, and then the sample was kept for 4 min, also under a vacuum, but without load. The wet sponge pressed in this way was weighed and dried to a constant weight at 105 °C in a SNOL 24/200 oven .mdry is the weight of the dried sample, and mtheor is the weight of the protein under the condition of 100% gelation yield.The yield of the gel fraction (Y) was calculated from the ratio:Sw/w) of the polymeric phase  of the wide-pore samples was calculated by the formula:mwet is the weight of the “pressed-off” wet sample.The degree of swelling by weight  equipped with the digital image recording MMC-50C-M system .w/v) SDS solution containing DTT (0.05 mol/L). Electrophoresis according to Laemmli’s procedure [The component composition of the synthesized proteinaceous cryogels was evaluated with the aid of the electrophoresis in poly(acrylamide) gel (PAAG) after the overnight dissolution of the respective cryogel samples in the 1%  were used in each cultivation experiment. The newts were anesthetized with a 2% solution of ethyl urethane in amphibian saline (0.65% NaCl). After anesthesia, the animals’ heads were rinsed with 70% ethanol, and the eyes were enucleated under standard laboratory lighting. Isolated eyes were rinsed and stored in the sterile 35 mm Petri dishes with amphibian medium (199 medium—70% and distilled water—30%). The medium for culturing eye tissue had the following composition: 350 mL of the 199 medium, 150 mL of bidistilled water, 0.15 mL of 1.0 M HEPES buffer, 1 mL of the 1% gentamicin solution and 0.5 mL of the antibiotic/antimycotic Gibco® solution . Before being introduced into the vials, the medium was cold-sterilized passing through the membrane filters of the FPE-204-030 type , with a pore size of 0.22 μm. The test eye tissues were prepared under a binocular lens in the following sequence of manipulations: the eyes were cut along the circumference, proximal to the limb. The growth region of the retina, along with the iris, cornea, and lens, were discarded. The posterior segment of each eye, which included the retina, pigment epithelium, vasculature, and sclera, was used for the subsequent cultivation.The studies were performed using the eyes of the The following six groups of samples were involved in these experiments:Group 1. The eye-derived segment in the cultivation medium (10 mL) without foreign additives and 0.1 mL of physiological saline; the system did not contain a cryogel sponge and bioregulators (reference samples).Group 2. The eye-derived segment placed onto the non-loaded cryogel sponge in the cultivation medium (10 mL) with 0.1 mL of physiological saline added (reference samples).–8 mg/mL); the system did not contain a cryogel sponge (reference samples).Group 3. The eye-derived segment in the cultivation medium (10 mL) with 0.1 mL solution of a Vioftan-1 bioregulator added (source—the bovine blood serum) .–8 mg/mL); the system did not contain a cryogel sponge (reference samples).Group 5. The eye-derived segment in 10 mL of the cultivation medium with 0.1 mL solution of a Vioftan-5 bioregulator added (source—sclera of bovine eyes) .The experiments were performed in the small vials each containing 10 mL of the serum-free cultivation medium, as well as the respective soluble additives and enclosures .Cultivation was carried out at 20–22 °C for 72 h in the dark, without changing the culture medium. The state of the explants after the cultivation period was studied on a series of paraffin sections. The eye tissue segments were fixed in the 10% formalin aqueous solution for 12 h, rinsed three times with 70% ethanol, then dehydrated by the media of increased ethanol concentration, rinsed with xylene and poured into paraffin in accordance to the standard procedure . ParaffiAfter dewaxing and hydration, these thin sections were stained with hematoxylin and eosin followed being placed under a cover glass with the addition of an adhesive liquid. A Jenaval microscope  was used to the view histological sections. Assessment of the number of viable fibroblasts on histological sections was performed using the ImageJ program, estimating the number of fibroblasts in the sclera tissue relative to the area of the entire section. At least 30 s were examined for each experimental point. The results were processed according to the Mann–Whitney criterion . Pleurodeles waltl newts’ eyes were used as a model biological targets, a statistically reliable protective effect on the state of the sclera, vascular membrane and retinal pigment epithelium as well as on the viability of fibroblasts was found to be inherent in the proteinaceous cryogels loaded with the peptide bioregulator (Viophtan-5™) isolated from the bovine eyes’ sclera. To the best of our knowledge, such studies have not been performed earlier, and the results obtained in the present study are thought to be prospective in view of the applied biomedical potential of similar drug delivery systems consisting of blood-proteins-based cryogel-type carriers and various peptide bioregulators. At present, in vivo biotesting of similar systems is in progress in cooperation with professionals within the biomedical fields.The wide-pore proteinaceous cryogels are of interest as biocompatible materials for biomedical purposes. In this study we synthesized a series of similar spongy cryogels based on the protein mixture being the constituents of the bovine blood serum. The preparation technique was grounded in the known phenomenon that the solutions of such globular proteins in the presence of added denaturants like urea and the thiol-reductants like cysteine are capable of the cryotropic gel-formation. Now, it was shown that the gel-fraction yield decreased and the swelling degree of the walls of macropores in the prepared matrices increased with decreasing the initial concentration of the blood serum proteins. The optimum freezing temperature was found to be within a rather narrow range from −15 to −20 °C. The average size of the macropores in the resultant cryogels was 90–110 μm, and polypeptide chains belonging not only to albumin, but to some other serum proteins  present in the composition of the 3D polymeric network in the cryogels were thus obtained. Subsequent evaluative experiments on the application of such soft wide-pore gel materials as the carriers of peptide bioregulators have demonstrated the promising possibilities of the given approach. When the posterior segments of the


The paraesthesia, diplopia, enophthalmos and exophthalmos degree were measured in points. Results: In one year, the first and second groups had no differences in level of paraesthesia (p > 0.05). The absence of exophthalmos and differences between first and second groups, and between the third and the fourth groups with positive dynamics inside the groups were proved (p < 0.05). In the first and third groups, enophthalmos was absent, and it increased in the second and fourth groups . Diplopia in the first and third groups was absent, and it increased in the second and fourth groups . Conclusion: The elasticity and biocompatibility of titanium nickelide make the implant insertion and restoration of the lower orbital wall anatomy easier, with good postoperative clinical results.Background: The question of reconstruction of human tissues and organs with the use of medical materials is still open, because of the accurate requirements for their biological and physical features. The aim of this study was to prove the efficiency of titanium nickelide constructors in treatment of isolated orbital floor fractures or combination with zygomatico-orbital complex fractures. Methods: Patients with a fracture of zygomatico-orbital complex and/or low orbital floor (n = 44) carried out different treatments: in the first group, osteosynthesis and endoprosthesis with titanium nickelide structures; in the second group, titan mini-plates osteosynthesis; in the third group (‘blow-out’), endoprosthesis with a titanium nickelide mesh; and in the fourth group (‘blow-out’), conservative treatment and monitoring (archive data) ( Today, metals and alloys are used as the most important functional elements in various fields of medicine ,2,3. SciAmong the injuries of the facial skull zygomatic complex fractures occur in 25–30% of cases ,9. StatiUnique medical technologies were created today based on the discovery of the hysteretic behaviour of biological tissues, and a new generation of biocompatible materials and shape memory implants has been developed . TitaniuAn alternative for titanium plates is the use of fixing structures made of alloys with the shape memory effect. In this regard, the issues in the development of new modalities for reconstructive treatment in zygomatic complex fractures remain extremely actual. Analysis of the properties of metallic materials and alloys shows that alloys based on nickel-titanium alloys are the most compatible materials with body tissues, which is due to the delay of biological systems .We used, in our research material for endoprosthesis of the orbital floor, a system of titanium nickelide filaments with an exact diameter of 60–80 microns. The distance between the threads is 180 microns . ImplantThe positive properties of this material are its elasticity, which makes it easy to insert an implant into the orbit and restore the anatomy of its lower wall. High bio-inertness, the ability to not cause immune reactions and inflammatory processes and the mesh structure of the implant contribute to the ‘germination’ of tissues and its good fixation, preventing displacement .The aim of this study was to prove the efficiency of titanium nickelide constructors in the treatment of isolated orbital floor fractures or a combination with zygomatico-orbital complex fractures.We treated patients with a fracture of the zygomatico-orbital complex with displacement of fragments and a fracture of the lower orbital wall in the Department of Maxillofacial Surgery of Sechenov University for eight years from the year 2011.The stages of the study were approved by the Ethical Committee of the Sechenov First Moscow State Medical University (protocol No. 02-12 dated by 12 November 2012). The written consent of all patients to use the results of research and computed tomograms was obtained.Age of patients 18 years and older.Traumatic zygomatico-orbital fracture with a fracture of the lower orbital wall.Fracture of the lower orbital wall with displacement of fragments, changes in the parameters of the orbit and maxillary sinus.Dysfunction of the eye .The period from the moment of injury to admission to the hospital is not more than 10 days.The absence of severe somatic diseases.Inclusion criteria:Age up to 18 years.Traumatic zygomatico-orbital fracture without a fracture of the lower orbital wall with displacement of fragments.The period from the moment of injury to admission to the hospital is more than 10 days.The presence of severe somatic diseases.Criteria for not including patients in our research:Exclusion criterion: Patient violation of recommendations in the postoperative period.We divided patients into four groups:First group—patients with a zygomatico-orbital fracture and a fracture of the lower orbital wall with displacement of fragments. We performed osteosynthesis and prosthetics of the lower orbital wall with a mesh of titanium nickelide.Second group—archived data of patients with the same diagnosis, osteosynthesis without prosthetics of the orbit walls was made.Third group—patients with an isolated fracture of the lower wall of the orbit (blow-out). We performed endoprosthesis with a titanium nickelide mesh.Fourth group—archived data of patients with an isolated fracture of the lower wall of the orbit (blow-out), conservative treatment and dynamic observation without surgery were performed.p > 0.05).The patients’ age in all 4 groups varied from 18 to 47 years. The mean age in the 1st group was 30.2 ± 9.3 years; in the 2nd group it was 33.3 ± 8.9 years; in the 3rd group it was 31.3 ± 8.4 years; and in the 4th group it was 30.8 ± 9.9 years. The differences in age in all groups of patients were not significant .Based on medical history the cause of trauma was mainly domestic or sport injury. We coded the cause in all four groups alike: 0 point for sport trauma and 1 point for domestic injury. The mean point in the 1st group was 0.8 ± 0.3; in the 2nd group it was 0.9 ± 0.4; in the 3rd group it was 0.55 ± 0.5; and in the 4th group, it was 0.64 ± 0.5. The differences in cause of trauma in all groups of patients were not significant .All patients applied in hospital and the Department of Maxillofacial Surgery not later than 10 days after trauma. This period varied from one to five days in all groups. The average day of patient admission in the 1st group was 2.1 ± 1.2; in the 2nd group it was 2.2 ± 1.1; in the 3rd group it was 1.8 ± 1; and in the 4th group, it was 1.9 ± 1. The differences in days of patient admission in all groups were not significant .Diplopia: from 0 to 1, where 0 is the absence of diplopia and 1 is diplopia during gazing upward. The causes of the injury were coded by us: household—1, sports—0.We performed multispiral computed tomography of the middle zone of the face, with 3D reconstruction for the diagnosis and determination of surgery stages.We evaluated the position of the bone fragments, eyeball and periorbital fibre, eye muscles and optic nerve, the presence and size of the defect of the lower wall of the orbit, the signs of haemorrhage and the condition of the mucous membrane of the maxillary sinuses and ethmoid labyrinth. We paid special attention to the oculomotor muscles, and the prolapse of the contents of the orbit into the maxillary sinus. Analysis of computed tomograms was carried out in three projections: frontal, axial and sagittal. It should be noted that, in some cases, the X-ray picture was different from the clinical situation detected during surgery.When studying control images in the postoperative period, we paid attention to the quality of repair and fixation of bone fragments, the position of the titanium nickelide implant and the quality of restoration of the lower orbital wall. Control computed tomography of the middle zone of the face was performed while the patient was in the hospital and one year after surgery.All patients were consulted by an ophthalmologist and a neurologist, and drug therapy was carried out. Ophthalmological examination consisted in determining the acuity and fields of vision, haemorrhage and diplopia and examination of the fundus. Computed tomography was used to measure exophthalmos and enophthalmos ,20.The material for endoprosthesis of orbital floor is a system of titanium nickelide filaments with a diameter of 60–80 microns. The distance between the threads is 180 microns. Implants in the form of rectangles 3.0 × 4.0 cm in size were prepared from the mesh tissue and sterilised.The positive properties of this material are its elasticity, which makes it easy to insert an implant into the orbit and restore the anatomy of its lower wall, high bio-inertness, the ability to not cause immune reactions and inflammatory processes and the mesh structure of the implant contribute to the ‘germination’ of tissues and its good fixation, preventing displacement . We haveAll patients gave their oral and written consent for surgery, examination, investigations and use of results for research. Before the operation, a stereolithographic model of the middle region of the face was made for all patients of the 1st and 3rd groups.After performing operative approaches and repositioning the zygomatic bone to the correct anatomical position, we fixed the zygomatic bone in the zygomatico-frontal suture, using titanium nickelide fixators with shape memory with compression 7H (Newton) and 14H or titanium microplate . Then, fAfter fixing the zygomatic bone at three points, the lower orbital wall was again examined for bone defects, because the defect after repositioning the zygomatic bone could increase in size. After that, the implant was modelled intraoperatively using surgical scissors from the tissue of super-elastic titanium nickelide. Then, it was introduced into the orbit and installed in the correct anatomical position . The sizThe calculated R sample size was equal to 10. According to the possible dropout, the size of each group in our research was enlarged to 11 patients.Before surgical treatment we assumed Theorem 1.The diagnosis of fractures of the lower orbital wall and timely reconstruction prevents long-term complications associated with changes in the position of the eyeball, such as enophthalmos and diplopia.The null hypothesis µ0 was “there are no differences between group 1, where the nickelide titanium clamps were used for osteosynthesis and nickelide titanium endoprosthesis, and group 2 with the traditional surgical method of treatment”, and “there are no differences between group 3, where the nickelide titanium endoprosthesis was used, and group 2 with the conservative treatment and monitoring”.The alternative hypothesis µ1 was “there are differences between group 1 and group 2 and groups 3 and 4 in the results of different algorithms of treatment in patients with trauma of zygomatico-orbital complex and fracture of low orbital wall required in reconstruction”.We supposed µ0 is not equal to µ1.We counted means, variances, standard error and statistical significance for all groups and their possible connections. We checked groups for normality of distribution; when the differences in means and variances did not allow us to use parametric statistics (one-way ANOVA), we used tests for nonparametric statistics . For comparing the differences between the main and control groups in pairs, we used the Mann-Whitney test; for the assessment of the dynamics of any criterion, we used x2 Pearson tables; and for the testing of the connection between different symptoms and the density of this correlation, we counted Pearson and Spearman coefficients (r and rs). For statistics, we used program R ).p < 0.01), exophthalmos  and diplopia  in comparison to pre-operative condition. Additionally, it was shown that there was a decrease in the level of enophthalmos, but without statistical significance .In the first group, in 1 year after surgical treatment there was a statistically significant decreasing of the level of paraesthesia  and exophthalmos , in comparison to pre-operative condition. Additionally, it was shown the increase in the level of enophthalmos and the absence of positive dynamics of diplopia was without statistical significance .In the second group, after 1 year, there was a decrease in the level of paraesthesia  and diplopia  decreased, as did enophthalmos, but that was without statistical significance .In the third group, 1 year after operation, the level of exophthalmos  was registered, and a progression of enophthalmos , as well as an increase in the level of diplopia , but without statistical significance. In the fourth group, after 1 year, a decrease in the level of exophthalmos . In 30 days after operation, the means of paraesthesia test were not changed, in the first group 0.55(0–1) and 0.55 (0–2) . One-year control examination has shown the absence of differences in level of paraesthesia between groups 0.09 (0–1) and 0.09 (0–1)  but positive dynamics inside them (p > 0.05).Before operation, the appearance of paraesthesia in first and second group was approximately equal  . In 30 days after operation, the means of exophthalmos test were equal, in the first group 0.27(0–1) and 0.27 (0–2) . One-year control examination has shown the absence of exophthalmos and differences between groups (0 and 0), but positive dynamics inside groups (p < 0.05).Before operation, the appearance of exophthalmos in first and second groups were approximately equal  . In 30 days after operation, the means of the exophthalmos test were different, but not significantly, in both groups (0.09(0–1) and 0) . One-year control examination has shown the absence of exophthalmos and differences between groups (0 and 0), but positive dynamics inside groups (p < 0.05).Before operation, the appearance of exophthalmos in third and fourth group was approximately equal  . In 30 days after operation, the means of enophthalmos test were less in the first group  . One-year control examination has shown the absence of enophthalmos in the first group, and its increase in the second group  , with negative dynamics (p > 0.05).Before operation, the appearance of enophthalmos in first and second group was approximately equal  . In 30 days after operation, the means of enophthalmos test were less in the third group (0 and 0.36:0–1) . One-year control examination has shown the absence of enophthalmos in the first group, and its increase in the second  , with negative dynamics inside the last (ps. 0.05).Before operation, the appearance of enophthalmos in third and fourth group was approximately equal  . In 30 days after operation, the means of diplopia test were less in the first group  . A one-year control examination has shown the absence of diplopia in the first group and its increase in the second group   with negative dynamics (p > 0.05).Before operation, the presence of diplopia in first and second group was approximately equal  . In 30 days after operation, the means of diplopia test were less in the third group  . One-year control examination has shown the absence of diplopia in the third group, and its increase in the fourth group  , with negative dynamics (p > 0.05).Before operation, the presence of diplopia in third and fourth group was approximately equal  , medium correlation between diplopia and enophthalmos in the first group  and in the third group  and a weak correlation between these criteria in the second group . The density of this connection was different according to groups: in the first and third group, it was almost average ; in the fourth group, it was high ; and in the second group, it was low .Comparing different symptoms for search of correlation, we found a strong positive connection between diplopia and enophthalmos in the fourth group  had a linear fracture occur in the fronto-zygomatic suture area, in combination with linear or comminuted fractures of the infraorbital rim and zygomatico-alveolar buttress. According to Manson et al.’s classification  middle-eOrbital fractures with various degrees of comminution and defect size are almost always seen in patients with zygomatic complex fractures . AccordiDifferent degrees of the eye globe contusions were detected in 38 (86.33%) cases. Diplopia or oculomotor function disorders were diagnosed in 20 (45%) patients. B. Evans and G. Evans (2008) observed diplopia in 60% of the examined patients . At the Sensory disorders in the infraorbital nerve system are common after zygomatic complex and orbital floor fractures. In most cases, the recovery of pain and tactile sensitivity in the II branch of the trigeminal nerve occurred within 3–6 months. Persistent disorders of the infraorbital nerve were noted in two (5%) cases. In the study performed by Homer at al. A total of 20 of 42 patients (47.6%) with zygomatic complex and isolated orbital fractures had some infraorbital hypesthesia. There were 31.8% with isolated orbital floor fractures versus 68.4% zygomaticomaxillary complex fractures. The authors concluded that patients with zygomaticomaxillary complex fractures showed no difference in sensory prognosis between those repaired and observed .In patients with zygomatic complex fractures with a displacement of bony fragments, osteosynthesis was performed at three, two and one point in 57 (47.5%), 56 (46.67%) and seven (5.83%) cases, respectively. The choice of a fixator was carried out in accordance to its biomechanics, fracture localisation and pattern. Gadkari et al. in their systematic review concluded that a 3-point fixation is superior to a 2-point fixation in reducing malar asymmetry in zygomaticomaxillary complex fractures . It shouEndoprosthesis of the lower orbital wall of titanium nickelide mesh was performed in 11 patients with fractures of the zygomatico-orbital complex (group 1) and 11 patients with blow-out fractures (group 2). The use of this material restores the anatomy of the lower wall of the orbit with a good result. The mesh structure allows tissues to penetrate through the implant with good fixation, preventing displacement. The use of super-elastic titanium nickelide implants increases the efficiency of surgical treatment of patients with orbital floor fractures. Shtin et colleagues emanating from their clinical observations claim that the knitted TiNi-based mesh indicates a high level of biocompatibility. It is simply modified intraoperatively, to attach any desired shape/size for implantation, and can also be screw-fixed, providing a good supporting ability. The authors concluded that this method of reconstruction may be an attractive alternative to Ti-based meshes and plates in patients with enophthalmos, hypoglobus or diplopia, with good functional and cosmetic outcomes .According to the literature, titanium mesh is an optimal material to reconstruct defects in the treatment of orbital wall fractures. On the other hand, its stiffness can be a disadvantage in cases of recurrent facial trauma, which may cause mesh distortion and injury to orbital structures .It was found that the use of mini clamps made of titanium nickelide alloy is to minimise surgical trauma by reducing the length of the lateral eyebrow skin incision and decreasing the number of drilled holes in the bone. Other advantages reported by Strackee et al. were that staple fixation has a minimal effect on the periosteal blood supply, and little dissection is necessary to place drill holes. A characteristic of the titanium nickelide alloy is the shape-memory effect: its shape is temperature dependent. The fixation material has less bulk compared to plates, thus reducing the need for its removal in case of dental implants . In caseGreat interest in the creation of metal implants came about in the period of the late nineteenth to early twentieth century. High-grade steel implants have been used in medical clinics. Fixation methods using nickel-plated plates and steel screws have been developed for the treatment of bone fractures. However, the plates were often destroyed, and their effectiveness decreased. High-strength vanadium steel was later used for the manufacture of trauma plates and clamps. Analysis of the properties of metallic materials and alloys shows that alloys based on nickel-titanium ones are the most compatible materials with body tissues, which is due to the delay of biological systems .The hysteretic behaviour of the alloys based on titanium nickelide of the TH-10 type at a temperature of +36 °C corresponds to the hysteretic delayed reaction of tissues. Correction of the hysteresis width and the value of the reversible deformation εcr can be carried out by changing the composition of the TN-10 alloy and thermomechanical processing. Therefore, for the corresponding fabrics with a certain hysteresis width and strain, it is necessary to select an alloy based on TH-10 with the given parameters of the hysteresis width and the reversible strain value. The achievement of such predetermined conditions poses the problem of biomechanical compatibility of implants and tissues to a qualitatively new level. Coordination of new directions in the creation of medical materials, tools and implants of a new generation is carried out at the Research Institute of Medical Materials and Implants with shape memory (Tomsk), together with various medical institutions in Russia .The use of individual titanium nickelide implants increased the effectiveness of surgical treatment of patients with orbital floor fractures. High bio inertness, possibility of intraoperative implant modelling, elasticity, good restoration of the anatomical contour of orbit and the absence of fixation reduce the duration of surgery and the rehabilitation period. Such treatment tactics in the early period after injury prevents post-traumatic deformities and visual impairment.‘Method for restoring the lower wall of the orbit and lower eye region after injury’ RU-2-486-872-C1-10.07.2013.


The performance and flaws of welded joints are important features that characteristics of the welding material influence. There is significant research activity on the performance and characteristics of welding joint materials. However, the properties of dissimilar welding materials and the cracking problem have not been thoroughly investigated. This investigation focuses on the evaluation and analysis of fracture mechanics, including fracture toughness, microstructural analysis, and crack initiation of T2 copper-45 steel dissimilar welding materials. Standard tensile and three-point bending experiments were performed to calculate the ultimate strength, yield strength, and elastic modulus for fracture toughness. The macro/micro-fracture morphology for tensile fracture and three-point bending fracture were analysed. Based on these investigations, it was concluded that the fracture types were quasi-cleavage and an intergranular brittle fracture mixed model. The deflection of the crack path was discussed and it was determined that the crack was extended along the weld area and tilted towards the T2 copper. Finally, the crack propagation and deflecting direction after the three-point bending test could provide the basis for improvement in the performance of welded joints based on experimental testing parameters and ABAQUS finite element analysis. The welding of dissimilar metals has been an area of active investigations for many years. This objective reflects an overall industrial need of increasing importance that is predicated on the technical and economic potential of the process . DissimiGenerally, the physical and chemical properties of copper and carbon steel are quite different. The thermal conductivity of copper is 7–11 times that of steel and the melting point is 400–500 degrees Celsius lower than steel. However, at high temperatures, the atomic radius, lattice types, and lattice constants of Fe and Cu are very close. These similarities are beneficial in the welding of copper and steel dissimilar materials . T2 coppMany researchers have investigated the mechanical behavior of dissimilar welding joints; however, most of the studies have focused on the effect of welding defects on the tensile strength of dissimilar welding materials . AnalysiAt present, research on the welding materials of T2 copper and 45 steel mainly focuses on the influence of the welding solder on the interfacial strength. However, correlative research on electron beam welding is limited. As such, it is important to study the joint property and fracture behaviour of the electron beam welding specimens.In this work, a copper/steel dissimilar welding specimen was prepared by electron beam welding (without filler wire) to examine the weld properties of these joints. The microstructure of the copper/steel dissimilar welding materials of the weld area was analysed via the combination of micro-topography and macroscopic appearance. Accordingly, the relationship between crack deflection was demonstrated based on the material properties. Moreover, the fracture mechanics test parameter was examined on the basis of tensile properties and bending experiments.The test materials were prepared while using commercial welding processes and electron beam welding equipment. The model of electron beam welding machine was SEBW and the manufacturer was Guilin Shichuang vacuum CNC Equipment Co., Ltd. . After investigation, −2 torr, and welding speed 300 mm/min. The surface of the welding sample and the HAZ had a visible dividing line with the weld, which is clearly shown in We preferentially adjust the parameters with reference to A 4 × 8 × 10 mm square sample was taken from the welded sample by Electrical Discharge Machining (EDM), as shown in The tensile specimen was obtained by wire cutting according to GB/T228.1-2010   is 2.29; E is the elastic modulus; and, pR0.2 is the specified plastic elongation strength of the material in the vertical crack plane 0.2% at the test temperature.In the preceding Equations (1) and (2), the dimensional coefficient The fatigue crack was prepared while using the constant load method. After this process, the fatigue precracking of the three specimens was: 2.02, 1.96, and 2.04 mm. QF of the three specimens was 3286.569, 2727.193, and 3581.864 N.After the P-V curve of the three-point bending specimen was shifted, the value QF is the maximum force and Fmax is the maximum force that the specimen can withstand.The judgment basis is as follows.Fmax/QF1, FmaxQ/F2, and Fmax/QF3 are greater than 1.1, Kmax  was calculated while using Equation (4).Given that ICK is represented, as follows.QK can be acquired from the three-point bending test, (pR0.2)e is the plastic extension strength corresponding to the bias 0.2% at the test temperature, and (pR0.2)p is the plastic elongation corresponding to the fatigue precracking offset 0.2%.The judgment on plane strain fracture toughness a0 is the initial crack length, W − a0 is the difference between the sample width and the initial crack, and fK is the maximum value of the stress intensity factor in the final stage of the prepared fatigue crack. After the aforementioned judgement, 1/2.According to results from the data that are contained in After tensile testing, the macroscopic fracture area of the specimen is shown in The microscopic topography of the tensile fracture of the T2 copper/45 steel dissimilar welding materials is shown in The macroscopic shape of specimen 1 had obvious gloss and irregular geometry, and the shiny surface of the fracture was almost perpendicular to the normal stress, which is associated with the brittle fracture characteristic; and, significant grain-brittle fracture characteristics at the microscopic level. There was a network structure after fracture due to an external force, which was a relatively obvious network brittle phase, as shown in Brittle fracture also characterized the macroscopic fracture of specimen 2, which appeared as herringbone and radial patterns at the fracture with a shiny surface. There were fluvial, blocky, and spherical structures in the microscopic topography with cleavage steps and tearing ribs, which exhibited the microscopic features of crystal brittleness and cleavage fracture ,48.A few flaky smooth surfaces existed in the macroscopic fracture of specimen 3 and the entire fracture surface was relatively flat. The cleavage characteristics of trapezoidal and river patterns also appeared in the microscopic morphology, with tiny cleavage steps and tearing ribs that are associated with the cleavage fracture. The defects in the weld area and the impurities of the welding material caused this microscopic appearance.The macroscopic fracture surface is shown in The purplish-red hue gradually deepens from the top to the bottom in the crack extension zone and the copper attached to the fracture surface gradually increased. It was known that the crack gradually deflected along the copper thereby tearing copper that was attached to the surface, as shown in The three-point bending fracture was observed at 1000 times magnification while using SEM. As shown in The crack propagation path deflection of the dissimilar metal welding materials always deflects to the low strength material region . The attTherefore, the crack propagation path of T2 copper/45 steel dissimilar welding materials always deflected to the low strength side of the T2 copper because the strength mismatch between three regions was comparatively large and the toughness decreases from the weld area to HAZ and then the base metal.According to the test parameters and conditions, the simulation of crack propagation of the three-point bending test was performed by ABAQUS, and the results are shown in 1/2, which was lower than that of pure copper (approximately 8 MPa·m1/2–10 MPa·m1/2) [For the T2 copper-45 steel dissimilar welding materials that were made by electron beam welding, the joint strength, microstructural analysis, and crack initiation were explored. Based on the standard tensile test, the ultimate strength of T2 copper/45 steel dissimilar welding materials were determined to be 93.73 MPa, the yield strength was 75.37 MPa, and the elastic modulus was 108.86 GPa. It can be seen that the mechanical properties of the weld area are significantly different from those of copper and steel, which causes the strength mismatch between three regions. Through the three-point bending test, the fracture toughness was determined to be 6.027 MPa·mPa·m1/2) . This isThe SEM micro-morphology fracture surface of three-point bending specimen shows that the fracture type was a mixed mode of brittle intergranular and quasi-cleavage fracture. The observation results of macroscopic crack propagation of three-point bending specimen were consistent with the theoretical and ABAQUS analysis, it was concluded that the cracking path was extended along the weld area and biased towards the T2 copper. Moreover, the strength of mismatch and toughness reduction controlled the deflection.


The extreme elasticity and reversible deformability of rubber, which is one of the most versatile polymers in modern society, is dependent on several factors, including the processing conditions, curing system, and types of additives used. Since the rubber’s mechanical properties are influenced by the existing structural crosslinks, their correlation with the crosslink characteristics of rubber was investigated using the equilibrium swelling theory of the Flory–Rehner equation and the rubber–filler interaction theory of the Kraus equation. Herein, we examined whether the accelerator and reinforcement agent quantitatively contributed to chemical cross-linkages and rubber–filler interaction. In conclusion, the accelerator content supported the chemically crosslinked structures of the monosulfides and the disulfides in natural rubber (NR). Additionally, these results demonstrated that the mechanical properties and the thermal resistance of NR were dependent on the crosslink characteristics. The findings of this study provide an insight into the development and application of NR products for the mechanical optimization of rubber-based products. Hevea brasiliensis as latex in nature, is one of the oldest polymers in use and consists mainly of a cis-1,4-polyisoprene structure [Natural rubber (NR), which is obtained from tructure ,3,4 as ctructure ,6. The etructure . In othex–, x ≥ 3). Since the mechanical properties of rubber are dependent on the structure and density of the crosslinks within the rubber [Crosslinked rubber generally consists of linkages brought about by sulfur-based chemical reactions between the rubber’s main chains, and are composed of monosulfide (–S–), disulfide (–S–S–), and polysulfide , stearic acid , sulfur , N-isopropyl-N′-phenyl-phenylenediamine , and 2,2,4-trimethyl-1,2-dihydroquinoline  were employed as the reinforcement agent, lubricant, crosslinking agent, and antioxidants, respectively. Commercial grade 2,2′-dithiobis(benzothiazole) (MBTS) and diphenylguanidine (DPG) were used as the accelerators. Tetrahydrofuran (THF) and n-hexane, which were used for sample purification, and toluene, which was used for sample swelling, were all obtained from Sigma-Aldrich . For the structural analysis of the crosslinks, 2-propanethiol (≥98%), 1-dodecanethiol (≥98%), and piperidine (99%) were provided by Sigma-Aldrich.NR was obtained from Karthik Rubbers . Carbon black  for 1 min. Reinforcement agents were added, and the whole was mixed for 3 min, followed by the addition of the lubricant and subsequent mixing for another 3 min. Next, the crosslinking agent was added and mixed at a rotor speed of 30 rpm until the temperature reached 90 °C. In the final step, the compound was mixed with the crosslinking accelerators in an 8-inch open-type roll  for 4 min at 30 °C. The five-step process was designed to prevent early curing and to improve the dispersion of the additives. The formulations and mixing conditions are presented in 90) was determined by investigating the curing characteristics of NR compounds using an RLR-3 moving-die rheometer . This was done to determine the scorch time (ts2), minimum torque (ML), maximum torque (MH), and t90 of the compounds of interest. Here, the NR compounds were shaped into squares with a length of 150 mm and a thickness of 2 mm using a laboratory hydraulic press , and heated at 180 °C under 2000 psi for t90. The crosslinking analysis was conducted on NR samples cut into squares with a length of 10 mm and a thickness of 2 mm.The optimum curing time  and piperidine (0.4 M) in toluene for 2 h under N2 gas. Cleavage of the polysulfide and disulfide was done by reacting the swollen NR samples with a solution composed of 1-dodecanethiol (1.0 M) in piperidine for 24 h under N2 gas [Various organic additives and impurities in the NR samples were removed by alternately soaking in r N2 gas . Once th3/mol for toluene), and 3) is the density of rubber. Additionally, 3) is the density of the solvent.R is the gas constant, T (K) is the absolute temperature (293.15 K), 1/2) is the solubility parameter of the rubber sample (16.7 MPa1/2 for NR), and 1/2) is the solubility parameter of the solvent (18.0 MPa1/2 for toluene) [The equilibrium swelling theory (as defined by the Flory–Rehner equation) and the rubber–filler interaction theory (as described by the Kraus equation) were used to quantitatively determine the crosslink density and structure of the rubber samples, respectively. The crosslink density tion (1) :(1)νcros and (3) ,22:(2)νrtoluene) . The calnt agent ,25.(4)νHere, The curing characteristics were determined using a moving-die rheometer. The change in torque at 180 °C was measured for 12 min. An electronic densimeter  was used to measure the density of the samples via the water displacement method, and the given density values presented in this study were the average of six independent measurements. The mechanical properties were measured according to American Society for Testing and Materials (ASTM) D412-98a using a universal testing machine . All tests were performed at a crosshead speed of 500 mm/min and room temperature. Dumbbell-shaped samples were prepared according to ASTM D2240 and D412, and the average values from three different measurements obtained under the same test conditions were used. The dumbbell-shaped samples were exposed to air at 100 °C for 70 hours in a geer-type oven . The thermal aging properties of the samples were investigated by comparing their mechanical properties before and after thermal aging according to ASTM D573.s2, t90, ML, and MH values associated with these compounds. The ts2 indicates that rubber compound can be mixed at a given temperature before curing begins, and is defined as 5% of the ML at MH. The t90 is the vulcanization time required to facilitate the optimal characteristics of the final products, and is defined as 90% of the ML at MH [s2 and t90, and an increase in the content of the DPG and the MBTS was attributed to the preferential promotion of the curing reaction by DPG rather than by MBTS. Similarly, these values showed a slight decrease when the carbon black content was increased; this was attributed to accelerated crosslinking reactions between rubber and sulfur via the generation of radicals at low temperatures with an increase in the amount of the crosslinking accelerator [The curing characteristics of rubber play an important role in rubber processing and lay the groundwork for the basic analysis of rubber processing systems because the curing behavior is heavily dependent on the type of rubber and additives used, as well as the amount of additives. Additionally, the best-performing rubbers depend on their mechanical and thermal properties, which are determined by measuring the tML at MH ,27,28. Telerator . Additioelerator .H increased at higher amounts of DPG and carbon black, MBTS seemed to exert very little influence. The ML was significantly influenced by the carbon black content, but the DPG content seemed to be irrelevant. Further, the addition of MBTS reduced ML because MBTS acted as a plasticizer before decomposition and during the vulcanization reaction [H and ML, and was indicative of the formation of crosslinks during the curing reaction [The torque values are indicative of the shear force resistance in rubber at a given temperature. Although the Mreaction . The relreaction ,32,33. TAs mentioned earlier, crosslink reactions are important in improving the overall performance of rubber. Analyzing the crosslink density and structure of rubber provides insight that can be used to enhance the polymer’s performance. In a rubber chain, sulfur reacts to form monosulfides, disulfides, and polysulfide structures, and the crosslink density is significantly affected by the type and amount of the fillers, accelerators, and activators used . These fThe fillers in the rubber matrix function as reinforcement agents; reinforcements are caused by generating interaction between the rubber and the filler. Since these interaction led to the immobilization of the rubber chain, it can be difficult to extract the rubber even with a good solvent ,37. TherThe Kraus plots of the NR samples with their corresponding carbon black content are shown in The mechanical properties of the NR samples were evaluated by focusing on how the crosslink densities and structures were influenced by the accelerator and carbon black content of the rubber. Here, variations in the tensile strength, the elongation at break, and the hardness of the NR samples were noted when the carbon black and accelerator contents in the samples increased . The tenAs noted in the results obtained from the chemical crosslink density analysis, the tensile strength slightly increased when the accelerator content was higher. This is due to the formed network structures in rubbers, which arise from the chemical crosslink reaction. A reduced occurrence of elongation at break was observed when the carbon black content was higher. The converse trend was noted at a high crosslinking accelerator content, i.e., the elongation at break was higher when more accelerator was present. This finding was linked with the carbon black content, which reduced the overall softness of the rubber via reinforcement, thereby facilitating the aggregation of carbon black and consequently encouraging the formation of fractures in the rubber. On the other hand, the use of accelerators introduced a higher degree of elasticity into the polymer, which increased the elongation at break effect by increasing the extent of entanglement between the NR chains and the chemical crosslinking. As expected, the hardness of NR increased continuously with the addition of carbon black and the accelerators. In particular, the accelerator has a larger influence on hardness because the chemical crosslinking density of NR was increased by adding the accelerators. In other words, increases in accelerator content cause higher crosslink densities and, therefore, increase the hardness of NR .The influence of crosslink density and structure on the mechanical properties associated with thermal aging was examined by subjecting the NR compounds to the thermal aging process for 70 h at 100 °C. Here, the relative tensile strength and the elongation at break effects were calculated before and after thermal aging. The relative tensile strength and relative elongation at break were calculated before and after aging using the following equation:In this study, the crosslink characterization of NR was examined by varying the carbon black and accelerator content of the polymer. Additionally, the correlations between crosslink characterization and the mechanical properties and the effects of thermal aging were studied. To this end, we performed analyses to determine the crosslink density of NR using the equilibrium swelling theory and thiol–amine analysis. The crosslink densities and their associated structures were calculated using the Flory–Rehner and the Kraus equations, and the crosslink characterizations of NR were analyzed by dividing the chemical crosslink density and the rubber–filler interaction. As a result, a distinct correlation was found between the chemical crosslink structures and the mechanical properties, which, in turn, promoted the formation of the crosslink density of the NR rubber. As noted in the results, the tensile strength slightly increased when the accelerator content was higher. In particular, the relative tensile strength and the elongation at break of NR sharply increased by adding the secondary accelerators such as DPG. In other words, the chemical crosslink characterizations of NR were affected by the accelerator content, and these subsequently influenced the rubber’s mechanical properties and thermal aging resistance. In conclusion, the crosslink characterizations of NR can be adjusted by changing the accelerator rather than the carbon black to improve the thermal aging resistance of NR. These results could advance the future development of NR products with optimized mechanical properties, thereby contributing to NR research in general and the fabrication of improved NR products.


In this paper, the influence of graphite (Gr) on the dry sliding tribological properties of phenolic resin (PF) composites was studied under different sliding speeds of 3.1–47.1 m/s. The wear mechanism was investigated by the observation of the morphology of the transfer layer during the dry sliding process. It was found that the addition of Gr could decrease the friction coefficient and wear rate effectively, and the friction coefficient and wear rate decreased with the increase of Gr content in the range of 10–30 vol.%. The dominant wear mechanisms of PF-based friction composites changed from adhesive wear to fatigue wear (in the form of peeling-off) in the high sliding speed condition after the addition of Gr. The addition of Gr effectively reduced the sensitivity of PF-based friction materials to sliding speeds, and thus enhanced the stability of the friction coefficient. When the content of Gr was above 20 vol.%, the stability of the friction coefficient was relatively steady. The development of high-speed trains necessitates higher requirements to the brake system. The tribological properties and compositions of friction materials directly affect safe and comfortable brake performance and the ecological environment ,9,10,11.Among organic materials, phenolic resin (PF) with low density, high bonding strength with fillers, good environmental performance and high reliability under severe conditions, has been widely used in braking materials for 250 km/h trains, heavy-duty vehicles and cars etc., and numerous applications ,17,18,192S3 and Gr improved the friction stability and fade resistance. Zhu et al. [Graphite (Gr), due to its lamellar structure, is an essential solid lubricant component. Gr is found to decrease the friction coefficients and wear rates of resin-based friction materials effectively ,38,39,40u et al.  investig2S3, MoS2 and other components, the study of the transfer layer formation and wear mechanism of Gr in a PF-matrix becomes extremely arduous because of the variation of the transfer layer composition and the interaction between fillers. So far, the effect of Gr on the formation of the transfer layer and wear mechanism is still elusive.Recent investigations mainly focus on the influence of surface morphology variation on the tribological properties of resin-based multi-component friction materials under different pressures and sliding speeds. The tribological properties of friction material are directly affected by the formation process and composition of transfer layers generated during the sliding contact. With the fillers like glass fibers, aramid pulp, SbIn the present study, we carried out an experiment on the pin-on-disc configurations in a wear-testing machine with a H13 disc sliding against the PF composites. The investigation was on the tribological properties and friction morphology of a series of Gr–PF composites with Gr content in the range of 0–30 vol.% under the different sliding speeds of 3.1–47.1 m/s. The study aims to identify the effect of Gr on the formation of a lubricating layer of Gr–PF composite in the dry sliding process, consequently revealing the wear mechanisms.The Gr–PF composites were packed in a mold with Gr granules and PF powders. The PF powders containing hexamethylenetetraminse (a curing agent) were used as the matrix. Gr granules with an average size of 300 μm were added to the PF powders at the volume fractions of 0 vol.%, 10 vol.%, 20 vol.%, 25 vol.% and 30 vol.%  each as shown in avg/μmax × 100 %, where μavg was the mean of dynamic friction coefficient (μd), and μmax was the maximum of μd [3/Nm) and calculated as,3 and P is load in Newton.The tribological properties of the PF-based friction composites were investigated under dry sliding conditions with pin-on-disc configurations in a wear-testing machine. The friction force generated during the friction test was transformed into the pull force of the sensor, which could show the change curve of the friction coefficient with the friction time on the computer, and the average value of the friction coefficient in the test time was also given. The pin (specimen) was Φ25 mm × 15 mm. A steel disc made of H13 steel of 308 HB was used as the counterpart and the turning radius was 150 mm. At the beginning of the test, the cured pin specimen was pre-ground until it achieved a complete contact with the disc on pin-on-disc tribometer. The surface roughness (Ra) of the pin was 3–6 μm. The contact surface of the disc was polished by hand with grand 800- and 2000-grit abrasive papers, respectively, cleaned with acetone to remove the surface contaminants and dried prior to testing. The contact surface roughness (Ra) of the steel disc was <1.5 μm. The ranges of the sliding speeds were 3.1–47.1 m/s with the contact pressure of 0.51 MPa. The testing experiments were carried out for 5 min for each friction . The friction stability was defined as μum of μd . Wear raThe microstructures of the friction surfaces were observed by an optical metallographic microscope (OM), confocal scanning laser microscope and scanning electron microscope (SEM). The parameter statistic of grooves on the worn surface was measured by a confocal scanning laser microscope. The worn surface was investigated with SEM after gold coating and operated at 20 kV.By contrast with unfilled PF, the PF-based composites with the addition of Gr  show a stable friction–rotational speed relationship. The wear rates of specimens with higher Gr content (25Gr and 30Gr) decrease significantly compared to the PF without solid lubricant fillers. In particular, the specimen 10Gr records a stable decreasing friction coefficient and wear rate when the speed reaches 15.7 m/s. With the speed increasing from 15.7 to 47.1 m/s, the friction coefficient demonstrates fluctuation at 23.6 m/s, and then increases smoothly with the speed. Meanwhile, the wear rate increases steadily during the speed from 15.7 to 39.3 m/s, and then increases sharply when the speed rises to 47.1 m/s like PF shows in b. This pavg/μmax × 100%, taking the friction stability of 10Gr at 47.1 m/s for example, the on-line friction curve of 10Gr at 47.1 m/s is shown in The tribological characteristics of PF-based friction composites are further analyzed in terms of the percentage of friction stability against increasing speed. According to the friction stability equation μAccording to Archard’s theory of adhesive wear, it can be inferred that the raw matrix of PF adheres to the friction disc, and the micro lump could be taken away by the counter disc. With the roughness of the friction surface increasing, the actual contact area between the friction surface and the friction disc increased. Due to the discontinuity of the adhesion point, the friction coefficient appears unstable. When graphite is added as lubricant, the graphite-containing transfer layer which is formatted in dynamic balance is formed on the friction surface. Therefore, the adhesive wear between PF and friction disc is reduced, and the friction stability is improved effectively.a) is 3.96 μm), and the compacted debris shows on the actual contact areas. On one hand, under the high sliding speed condition, the temperature of the friction surface is high, accelerating the local aging of PF, consequently reducing surface shear tolerance. On the other hand, the severe fatigue makes it difficult for the friction surface to accumulate continuous compacted transfer films, thereby the fragmentation occurs at the actual contact areas, causing high coefficient and wear rate.It can be seen from The 3-D morphologies of the friction surface of the Gr–PF friction composite 30Gr at two different sliding speeds are shown in The SEM images of the worn surfaces for the samples, as shown in After incorporating 30 vol.% Gr into the friction composite, the SEM image of To express the friction mechanism of PF friction materials with the addition of Gr, comparing it with the Gr-free case, the formation mechanisms of the transfer film and lubricating film are listed below. For PF friction materials, their surfaces undergo a process of serious wear and tear, a small amount pulverized debris accumulates on low-lying place and forms a dense re-transfer film a. The roFor the Gr-free PF material, there are many grooves and spalling pits on the friction surface at the sliding speed of 3.1 m/s, indicating that the main wear mechanism is abrasive wear. Therefore, the friction coefficient and wear rate are relatively high. When the speed exceeds 7.9 m/s, cracks and shallower grooves appear on the friction surface, and the dominant wear mechanisms change to adhesive wear.The addition of Gr can effectively reduce the sensitivity of PF-based friction materials to sliding speeds, and thus enhance the stability of the friction coefficient. When the content of Gr is above 20 vol.%, the stability of the friction coefficient is relatively stable.With the addition of Gr, the friction coefficient and wear rate decrease effectively compared with the raw matrix of PF. The friction coefficient decreases with the increasing Gr content in the range of 10–30 vol.%.The dominant wear mechanism of PF friction material altered to fatigue wear (in the form of peeling-off) after the addition of Gr. A dense and continuous lubricating layer forms in the spalling pits where the flaky debris piles up and is compacted, which decreases the actual contact area between friction material and the steel disc; therefore, the friction coefficient and wear rate decrease and, consequently, the stability of friction coefficient under different sliding speed is enhanced.


Due to the occurrence among musicians of musculoskeletal problems associated with playing a musical instrument, it is necessary to use prophylaxis. The aim of the study was to compare the effectiveness of two physioprophylaxis methods: chair massage and an original set of exercises. The study lasted four weeks and consisted of eight 15-min meetings (chair massage/exercises). The study was conducted on 44 music students assigned to three groups (chair massage/exercise program/control group). The algometric measurements and questionnaire were conducted. Health problems associated with playing an instrument was reported by 86.4% of the participants. The largest changes in pain threshold concerned the trigger points of the muscles with the highest pain sensitivity, i.e., upper part of trapezius ones, and reached 25–34% in relation to the initial values. For the trigger points of the levator scapulae and lower part of trapezius, the increase in the pain threshold was between 20 and 28%. Raising the pain threshold was observed both after each session and meeting by meeting, and these differences were most visible in the massage group. This effect was particularly visible from the fourth treatment. Chair massage and exercise should be used regularly, and significant results can be obtained after two weeks. Artists playing musical instruments, due to loads related to the strain of playing the instrument, suffer from various forms of playing related musculoskeletal disorders (PRMD) ,2,3,4. MThere are many forms of physioprophylaxis of musculoskeletal pain . Specialists and scientists emphasize the need to develop prevention programs for this occupational group and they recommend physical exercises as the most efficient intervention ,16,17,18The music profession hinders regular use of physiotherapy sessions, which is why, according to the authors, a good form of prophylaxis is chair massage, because it can be performed at the place of work/stay of musicians. It is a treatment lasting from 15 to 20 min, in a special chair. During the treatment, the physiotherapist performs massage techniques, acupressure and stretching, focusing mainly on the area around the neck, head, upper limbs and back . Chair mThe aim of the study was to compare the effectiveness of two physioprophylaxis methods: chair massage and exercises in a group of student-musicians.After obtaining the consent of the Senate Ethics Committee for Scientific Research (SKE 01-61/2017), 44 students of The University of Music, comprised of 30 women and 14 men, were included in the study. Each participant was informed about the purpose and procedure of the research, as well as the possibility of resigning from participation at any time during the study. All participants gave their informed consent to participate in the project. The participants were constituted a convenience sample and were assigned to three groups: group I-massage on a chair-16 people, group II-exercises-14 people, group III (control group)-14 people. The groups did not differ in terms of weight, height, daily time of playing the instrument, duration of play in years, or reported pain, the results are presented in Participants reporting the occurrence of current disorders estimated their intensity at 2.5 ± 2.1 . The participants played different instruments: 18 people played the violin/viola, 6 people played the cello, 4 people played bassoon, 3 played the accordion and trombone respectively, 2 played the French horn, oboe, flute, and harp, respectively, and 1 person played the double bass and percussion, respectively.The qualification criterion for the study was: playing a musical instrument for a minimum of 5 years, while the disqualification criteria were: neurological and oncological diseases, medical contraindication to undertake physical exercise, contraindications to perform massage, and lack of consent for participation in the study.The original set of exercises was developed based on the knowledge and clinical experience of the authors of the study and based on EBP (evidence based practice). The program consisted of 14 strengthening and stretching exercises involving the muscles of the trunk and limbs whose main goal was to mobilize the joints and strengthen the weakened muscles and relax overloaded muscle groups. Exercises were performed in the following position: sitting in a chair (anteversion and retroversion of the pelvis-20 repetitions (reps.), alternating trunk twists right and left-10 reps., retraction of the cervical spine and head-10 reps., lifting and lowering the shoulder girdle-20 reps., backward shoulder girdle rotation-10 reps., alternating pro- and supination of the forearms-10 reps., rotation in the wrist joints-10 reps.), supine position (lifting the trunk and upper limbs with simultaneous retraction of shoulder girdle-30 reps.), prone position (thigh extension in hip joint-20 reps. per side), the bridge exercise-30 reps., the dead bug exercise-30 reps. per side, hamstring stretching-3 reps. (30 s per side), and in a standing position ).Chair massage was performed on the basis of the Work-Site Massage School. Only traditional methods of Swedish massage were used, consisting of stroking , kneading , stretching combined with swaying and passive movements of the upper limbs (to mobilize the joints of the upper limbs), and final stroking combined with slapping and shaking percussion, vibration. All massages, exercises, and measurements were conducted and supervised by the same specialist (physiotherapist with 5 years of experience), and took place in the morning, in a quiet and comfortable room; at the request of the participants, no music was used during the treatments. The study program is presented in The subjective evaluation was based on the Polish-language version of the Musculoskeletal Pain Intensity and Interference Questionnaire for Professional Musicians (MPIIQM-P) questionnaire (unpublished data-publication in progress);  and the author’s original subject log ended with a questionnaire for satisfaction with the proposed treatments. The MPIIQM-P questionnaire consists of 22 questions, divided into three parts: demographic data and information referring to playing the instrument, questions about the intensity of pain/problems, and questions about pain/problems interference.2 made using the Pain Test FPX Algometer (Wagner). Algometric measurement is an effective computational tool for myofascial pain [Algometric measurements were made as an objective assessment of the treatments carried out before and after each therapeutic session. The algometric measurement concerned the assessment of muscle pressure sensitivity-pain threshold in kg/cmial pain ,24,25. Tial pain , they we2) was used. The correlation between quantitative features was assessed using Pearson’s correlation. All analyses were performed using the STATISTICA 13 program . In the assessment of the significance of the effects, the p level was <0.05. Trial registration was on: ClinicalTrials.gov Identifier: NCT04366843, 28.04.2020 r.In the description of the results, basic statistical methods were used: arithmetic means, standard deviations (SD), standard errors (SE), and percentages. The normality assumption was verified using the Shapiro–Wilk test, the assumption of homogeneity of variances in the groups was tested by the Levene test. Both assumptions proved not to be violated, data were thus subjected to parametric procedures. The significance of changes in mean values of pressure sensitivity in the studied groups was assessed using the 3 × 2 (Group × Study) mixed-design (split-plot) analysis of variance (ANOVA), separately for the right and the left side of the body. Additionally, in the massage and exercise group, the assessment of the direct effect of the treatments applied during 8 meetings was performed using the 2 × 8 × 2 mixed-design ANOVA (Group × Study × Before/After). The assumption of sphericity was verified using the Mauchley test, in the case of significant violations, the Greenhouse–Geisser correction was applied. For significant ANOVA effects, detailed comparisons between pairs of means were made post hoc using the Tukey test. As a measure of the size of the effect, partial eta-square (ηn = 38 (86.4%) of the participants, and n = 29 (65.9%) of respondents reported the presence of current PRMD. The participants currently declaring the presence of PRMD did not differ in terms of BMI (p = 0.41), or seniority (p = 0.14), and intensity of playing the instrument (p = 0.08).The occurrence of a lifetime prevalence of PRMD was reported by p = 0.014) a longer period of playing the instrument (13 ± 2.5 vs. 10.6 ± 3.4 years), with no significant differences between women and men in terms of age (p = 0.78). In contrast, men reported statistically significant (p = 0.047) more time per week devoted to playing the instrument at 29.6 ± 10.2 h vs. women 23.3 ± 9.0 h. In the women’s group, the most common location of pain was the cervical spine (36%), and in the men’s group problems were reported within the shoulder girdle and left arm (43%) and the lumbar spine (43%). There were no differences between men and women due to the pain intensity factor which was 12.93 ± 5.79 (p = 0.51) or the pain influence factor was 18.5 ± 11.8 (p = 0.47). None of the participants had PRMD in the head area and lower limbs.Of all participants reporting PRMD, 81.8% were women. Women declared (n = 15) after the completed program assessed its usefulness at 8.8 ± 1.42 , whereas the impact of the program on reported PRMD was estimated at 6.7 ± 1.11 (n = 7). In none of the examined PRMD worsened, and currently complaints are reported by only four participants (two from the exercise group and two from the massage group). Due to the fact that few of the participants completed the follow up questionnaire in a reliable way, too little data was obtained to make statistical calculations.Participants from groups I and II (2 from 0.010 to 0.114). After the program, a reduction in the pressure sensitivity of the tested trigger points was observed in the groups subjected to treatment, the largest differences being in the massage group. Significant interaction was found for the trigger points of the right levator scapulae  and left  and the right lower part of trapezius muscle . It was also observed that in the massage and exercise groups the pressure sensitivity of the muscles decreased, and in the massage group this effect was greater  was observed, while for the right upper part of trapezius and left lower part of trapezius muscle trigger points, no significant differences were observed.For none of the trigger points tested, the main effect of the group was found to be significant; thus, there were no significant differences between the groups of massage, exercise, and control group (η greater . At the 2 from 0.010 to 0.072) interaction or Group × Study (η2 from 0.023 to 0.046) interaction. There were no significant differences between the groups (η2 from 0.001 to 0.136). Nevertheless, the pain threshold of all examined trigger points of the muscles increased (pain sensation decreased) immediately after each treatment (η2 from 0.478 to 0.736), as well as in subsequent treatments (η2 from 0.163 to 0.263). The largest changes concerned the trigger points of the muscles with the highest pain sensitivity, i.e., upper parts of trapezius muscles and reached 25–34% in relation to the initial values, for the trigger points of the levator scapulae and lower parts of trapezius muscles, the pain threshold increased by around 20–28%  and on the left side  in the massage group, a greater increase in the pain threshold was observed immediately after the treatment (reduced pain sensation) as compared to the exercise group (significant interaction Group × Before/After). On the other hand, for the following muscle trigger points: right levator scapulae , left upper part of trapezius , left lower part of trapezius , a significant Study × Before/After interaction was observed demonstrated by an increase in the pain threshold both immediately after the treatment and meeting to meeting. This dependence is particularly visible from the second treatment (third and fourth measurement), where the differences in the threshold of pain before and after the treatment were becoming more pronounced.In addition, for the right side upper part of trapezius and lower part of trapezius trigger points  . Many auThe results of algometric measurements indicate a positive effect of exercises on the level of pain threshold of the participants, but first and foremost, the chair massage should be used. The respondents from groups I and II positively assessed the applied treatments, evaluating the suitability of the program at around nine on a 10-point scale of assessment. Similar results were obtained by other researchers using this form of prophylaxis of musculoskeletal problems among other professional groups ,38,39. SAs an enhancement to the proposed treatments, the authors believe that educational activities should also be incorporated. Because during the study of both massage and exercise students had many questions about the most common injuries, the reasons for their formation and how to cope independently with various types of PRMD, which was also pointed out in research by Arnson et al. .The value of the research conducted is to propose a PRMD prophylaxis program taking into account the specificity of the work/education of musicians. For the first time, a chair massage was introduced as a form of prophylaxis. An important advantage of the study is the personal supervision of the participants during the whole program by a physiotherapist experienced in working with musicians; thus, ensuring the correctness of the program and confirming their execution, the verification of which is often difficult when participants after short instruction are supposed to do the exercises on their own.As a limitation of the study, it should be pointed out that due to the insufficient number of participants it was not possible to carry out the analysis for individual types of instruments. For organizational reasons, randomization was not possible. According to the authors, prophylaxis should have a general form, however it would be advantageous to think about compensatory exercises for individual types of instruments.To obtain the best results in pain reduction in musicians the prevention interventions need to be applied regularly and for a long-lasting time (at least two weeks). Musicians can be subjected to chair massage or do the exercises but simultaneously they need to be supervised by a professional physiotherapist who would check and correct the execution of the exercises.The results of the study indicate the validity of introducing chair massage as one of the forms of preventing musculoskeletal problems among musicians in institutions educating and employing artists. Both chair massage and exercise should be used regularly, and significant results can be obtained after approximately two weeks of use.