By employing coarse-grained molecular dynamics simulation, we simulate the spatial organization of the polymer-grafted nanoparticles (NPs) in homopolymer matrix and the resulting mechanical performance, by particularly regulating the grafted chain length and flexibility. The morphologies ranging from the agglomerate, cylinder, sheet, and string to full dispersion are observed, by gradually increasing the grafted chain length. The radial distribution function and the total interaction energy between NPs are calculated. Meanwhile, the stress–strain behavior of each morphology and the morphological evolution during the uniaxial tension are simulated. In particular, the sheet structure exhibits the best mechanical reinforcement compared to other morphologies. In addition, the change of the grafted chain flexibility to semi-flexibility leads to the variation of the morphology. We also find that at long grafted chain length, the stress–strain behavior of the system with the semi-flexible grafted chain begins to exceed that of the system with the flexible grafted chain, attributed to the physical inter-locking interaction between the matrix and grafted polymer chains. A similar transition trend is as well found in the presence of the interfacial chemical couplings between grafted and matrix polymer chains. In general, this work is expected to help to design and fabricate high performance polymer nanocomposites filled with grafted NPs with excellent and controllable mechanical properties. Polymer nanocomposites (PNCs) filled with various kinds of nanoparticles (NPs) have been a hot topic in academia and industry because of the promising mechanical, electrical, and thermal properties;gas permeability; and so on ,2,3. ThiOne effective approach is to uniformly graft the NPs with short polymer chains ,7,8. ForHowever, althoughplenty of previous studies have been carried out to study the effects of the structural parameters on the spatial distribution and organization of the end-grafted NPs in the polymer matrices, little efforts have been devoted to establish the relation between the morphology and the resulting mechanical properties. Through the rheology analysis of polymer-grafted NPs filled polymer nanocomposites, Moll et al.  found thIn this work, we fix the loading of the NPs and the number of the grafted polymer chains, and we aim to simulate all the possible morphologies formed by the grafted NPs in the same homopolymer matrix and the resulting mechanical properties by particularly varying the grafted chain length and flexibility, in hopes of providing scientific guidance for the fabrication of PNCs with excellent and tunable mechanical properties with significant practical applications.Lg from 2 to 36 beads.In this work, we adopt a coarse-grained model to model the polymer chains such as the bead-spring model, in which each bead corresponds to 3–6 bonds of a realistic polymer chain. The surface of the modeled NPs is grafted evenly with six short polymer oligomers, which are chemically identical with the polymer matrix. Each matrix polymer chain contains 100 beads, and the number of matrix polymer chains is 300. It is noted that the grafting density is fixed, while we vary the grafted chain length Lg = 8, as is seen in To graft the short polymer oligomers onto the surface of each NP, we follow our previous approach  as follor is the distance between two interaction sites, while σ is the distance unit, and Δ is the effect of excluded volume of different interaction sites in the LJ function. Hence, the actual cutoff distance is the sum of rcutoff and Δ. For polymer-nanoparticle interactions Unp and nanoparticle-nanoparticle interactions Unn, Δ is C is a constant that guarantees the condition that when The non-bonded interactions are modeled by the expanded truncated and shifted Lennard–Jones (LJ) interaction, which include the polymer–polymer, polymer–nanoparticle, and nanoparticle–nanoparticle interactions, given byThe bonded interaction between the neighbor beads along a polymer chain is modeled as the harmonic potential:6 runs for each tensile test.To study the tensile deformation, we increase the length of the simulation box in the y direction at a fixed engineering strain, while the box lengths in the x and z directions are reduced simultaneously to maintain the volume of the simulation box during the deformation process. The tensile strain rate is defined as follows: All MD runs are carried out through the large scale atomic/molecular massively parallel simulator (LAMMPS), which is developed by Sandia National Laboratories. For all cases, we make sure that each chain has transported at least hed work ,21,22. TWe firstly examined the self-assembly structures, potentially formed by NPs uniformly grafted with the same chains as the matrix polymer chains. Note that we fix the grafting density equal to 0.18, given by:a et al. . When thr chains . The undr chains  pointed In To better characterize the self-assembled structures, we use the radial distribution function (RDF), as shown in We then investigate the tensile process of various self-assembled structures, expecting to find the most optimal structure that exhibits the best mechanical performance. We simulate all the systems by stretching the simulation box along the y direction while keeping the box volume constant. To analyze the possible reason of why the sheet structure endows the best mechanical performance, we probe the snapshots during the tensile process as shown in To better identify that the microscopic origin of the stress is from the breakage of clusters, we calculated the shape deformation and cluster size of nanoparticles during the extension. The variation of the number of clusters and the number of nanoparticles per cluster are listed in To better quantify the deformation process, we calculate the total interaction energy between NPs during tensile process, as shown in In fact, we have observed that the strongest mechanical reinforcement is obtained when the grafted NPs self-assemble into the sheet structure. Based on the research work carried out by Moll et al. , a maximFinally, in order to eliminate the effect of the periodic boundary, we demonstrated the finite size effects of the simulation box on the obtained structures and the corresponding mechanical response. We multiplied the whole system by both twice and four times the initial system. After equilibrium of the same conditions, we obtained the self-assembly structure of nanoparticles, as is seen in In this part, we shift our attention to vary the grafted chain flexibility, which receives little attention about its influence on the relation between the morphology and the mechanical properties. By choosing the grafted chain length The self-assembled equilibrium structure for various grafted chain length is shown in In addition, we calculate the radial distribution function of the NPs in We then characterize the mechanical properties of these five simulated systems with the NPs grafted with semi-flexible polymer chains. It should be noted that our system with semi-flexible grafted chains is still under melting state with temperature We hereby demonstrate the situation where the matrix polymer chains are semi-flexible and the grafted chains are flexible merely as a reference. We concentrated on the grafted chain length of Finally, by introducing interfacial chemical cross-linking between grafted and matrix polymer chains, we compare the stress–strain behavior between the flexible and semi-flexible grafted chains systems like In this work, by varying the grafted chain length, we have observed various self-assembled structures formed by grafted NPs in the homopolymer matrix. By comparing the stress–strain behavior of each morphology, we find that the sheet structure possesses the best mechanical reinforcing efficiency, as well validated by the occurrence of the stress overshoot at large strain. Meanwhile, we also simulate the effect of the grafted chain flexibility on the self-assembled morphology and the resulting mechanical properties. Compared to the flexible grafted polymer chain, we observe that the stress–strain behavior of the semi-flexible grafted polymer chains is enhanced greatly at long grafted chain length, attributed to the physical inter-locking and wetting between matrix polymer chains and grafted polymer chains, which has the same trend in the presence of the interfacial chemical bonding between grafted and matrix polymer chains. In general, it is anticipated that this work could provide some guidance on tailoring the mechanical performance of grafted NPs filled polymer nanocomposites, by taking advantage of varying the grafted chain length and flexibility.


Glass fiber-reinforced polymers (GFRPs) have received increasing attention in recent years due to their overall performance of light weight, low cost and corrosion resistance, and they are increasingly used as reinforcement in concrete structures. However, GFRP material has low elastic modulus and linear elastic properties compared with steel bars, which introduces different bonding characteristics between bars and concrete. Therefore, a reliable monitoring method is urgently needed to detect the bond slip in GFRP-reinforced concrete structures. In this paper, a piezoceramic-based active sensing approach is proposed and developed to find the debonding between a GFRP bar and the concrete structure. In the proposed method, we utilize PZT (lead zirconate titanate) as two transducers. One acts as an actuator which is buried in the concrete structure, and the other acts as a sensor which is attached to the GFRP bar by taking advantage of machinability of the GRRP material. Both transducers are strategically placed to face each other across from the interface between the GFRP bar and the concrete. The actuator provokes a stress wave that travels through the interface. Meanwhile, the PZT patch that is attached to the GFRP bar is used to detect the propagating stress wave. The bonding condition determines how difficult it is for the stress wave traveling through the interface. The occurrence of a bond slip leads to cracks between the bar and the concrete, which dramatically reduces the energy carried by the stress wave through the interface. In this research, two specimens equipped with the PZT transducers are fabricated, and pull-out tests are conducted. To analyze the active sensing data, we use wavelet packet analysis to compute the energy transferred to the sensing PZT patch throughout the process of debonding. Experimental results illustrate that the proposed method can accurately capture the bond slip between the GFRP bar and the concrete. Corrosion of steel reinforcement embedded in reinforced concrete (RC) is one of the most significant factors limiting the service life of RC structures ,2. It isThere are many nondestructive testing (NDT) and structural health monitoring (SHM) ,18,19 apPiezoceramic material is very versatile and is commonly used in SHM and damage detection ,36,37,38For its effectiveness and simplicity, the piezoceramic-based active sensing method has been proposed and applied for the debonding detection in recent years. Ihn and Chang used active sensing methods for detecting cracks and debonds in metallic and composite structures . MustaphThe piezoceramic-based active sensing method has been used in the detection of the debonding status between concrete and the rebars ,56. HoweThe rest of the paper is organized as follows. Piezoceramic material, as a type of piezoelectric material, has superior properties of low cost, quick response, high reliability, solid-state actuation, wide frequency range and energy harvesting capacity ,58,59. AAn active sensing method ,63,64 usIn this paper, an active sensing technique using piezoceramic transducers is proposed to detect the debonding status of GFRP bars in RC structures. The PZT patch embedded in the GFRP bar is used as a sensor to detect stress waves which are generated from a PZT actuator fixed in the concrete specimen cube. The detecting principle is illustrated in A pull-out test is used to cause the damage between the GFRP bar and the concrete specimen. When a bond slip happens, with the appearance of the internally cracked zone shown in b, which Wavelet packet analysis is an effective method for signal processing which has been widely used in structural health monitoring ,66,67,68j represents the decomposed wavelet packets. With the wavelet packet-based method, the severity of bond slip can be analyzed based on the total energy of the received signal.Wavelet packet analysis is an excellent signal-processing tool which has been widely used to extract damage features. In this paper, we use Wavelet Toolbox provided by MATLAB to compute the total energy of the signal. The energy of each wavelet packet The design of the specimen with the PZT-enabled active sensing approach is shown in 3 in size working as sensor is embedded in the GFRP bar by taking advantage of the machinability of the GFRP. With this special design, a recess that matches the dimension of the PZT patch is processed, and then the PZT patch is placed in the recess with a thin layer of epoxy. In this way, the original shape of the GFRP bar is restored. Both transducers are strategically placed across from the interface to best monitor the interface condition via the active sensing approach. A bond slip between the GFRP bar and the concrete introduces a crack along the interface and adversely impacts the stress wave propagation across the interface.As shown in The length and diameter of the GFRP bar are 560 mm and 20 mm, respectively, and the tensile strength and the modulus of elasticity of the GFRP bar are 83 MPa and 72 GPa, respectively. Each specimen has the dimensions of 200 mm × 200 mm × 200 mm. The strength of the concrete is 35 MPa. Two specimens are fabricated, and As shown in The pull-out test schematic is shown in The instrument system, as shown in Experiment 1.The specimen is the one with the 5D length of GFRP bar. The loading rate is 0.5 mm/min. The experiment lasted 18 min and 30 s.Experiment 2.The specimen is the one with the 4D length of GFRP bar. The loading rate is 0.3 mm/min. The experiment lasted 32 min and 5 s.In this experimental test, the loads and the extensions applied on the specimen are controlled by the universal material test machine. Please note that in this research two experiments that involved two different specimens are conducted via pull-out tests. Both experiments are conducted under the displacement control mode. For both the strain gauge and PZT-enabled active sensing, the data are collected every 5 s. During both experiments, a bond slip is often accompanied by a loud sound. The experiment will be terminated if a sharp drop in the loading time history is observed.The BPE model, which is named after Bertero, Popov and Eligehausen, is generally used to describe the bond slip of a steel bar in concrete . CosenzaWe conduct both experiments by following the procedures described in At the beginning of the loading process, the strain of the GFRP bar (black line) increases with the load until 14.3 min, after which the strain starts to decrease as shown in The strain gauge which is bonded on the surface of the GFRP through the epoxy is used to measure the local strain of the GFRP. The bonding condition changes during the loading process, which adds uncertainty to the strain monitoring. In addition, the strain gauge can only measure the strain in a small localized area. Therefore, it is difficult to effectively detect the bond slip between the GFRP bar and the concrete by using the strain value.Also from Similar results are also observed in experiment 2 with the second specimen. In this experiment, only a single major bond slip is observed, which is verified by both the energy reading of the PZT-enabled active sensing and the strain gauge. The failed specimen is shown in In this paper, a PZT-enabled active sensing technique was proposed and implemented to detect the bonding slip between a GFRP bar and RC structure. Two PZT transducers were employed: one in the form of a piezoceramic smart aggregate and the other in the form of a patch. Both transducers were strategically placed to face each other across from the interface between the GFRP bar and the concrete. A piezoceramic smart aggregate working as actuator was buried in the concrete to generate a stress wave that propagated and traveled through the interface. Meanwhile, the PZT patch that was embedded in the GFRP bar worked as sensor to detect the arriving stress wave. The bonding condition determines how the stress wave travels through the interface. The occurrence of a bond slip introduced a crack between the bar and the concrete, and dramatically reduced the energy the stress wave carried through the interface. In this research, two specimens were fabricated and two pull-out tests were conducted. The experimental pull-out test results demonstrated that the PZT-enabled active sensing approach could accurately capture the bond slip between a GFRP bar and concrete. The energy metric based on wavelet packet analysis can indicate the bond slip occurrence as the energy of arriving stress wave significantly drops. This active sensing technique provides a reliable real-time debonding damage monitoring method for GFRP-reinforced concrete structures.


Polymer technology is one of the fastest growing fields of contemporary research due to the possibility of using a wide variety of synthetic chemical routes for obtaining a polymeric network with a well-defined structure, resulting in materials with outstanding macroscopic properties. Surface engineering techniques based on the implementation of polymeric structures can be used as an interesting tool for the design of materials with functional properties. In this sense, the use of fabrication techniques for the design of nanostructured polymeric coatings is showing an important growth due to the intrinsic advantages of controlling the structure at a nanoscale level because physical, chemical, or optical properties can be considerably improved in comparison with the bulk materials. In addition, the presence of these sensitive polymeric coatings on optical fiber is a hot topic in the scientific community for its implementation in different market niches because a wide variety of parameters can be perfectly measured with a high selectivity, sensitivity, and fast response time. In this work, the two main roles that a polymeric sensitive matrix can play on an optical fiber for sensing applications are evaluated. In a first section, the polymers are used as a solid support for the immobilization of specific sensitive element, whereas in the second section the polymeric matrix is used as the chemical transducer itself. Additionally, potential applications of the optical fiber sensors in fields as diverse as biology, chemistry, engineering, environmental, industry or medicine will be presented in concordance with these two main roles of the polymeric sensitive matrices. Polymers are ubiquitous and currently they are present in any aspect of our lives: from the classic utilization as bags to preserve food, stationery material, protective cases, clothes, or paints, to the most recent uses in 3D printing or controlled drug-delivery applications. The fabrication and use of synthetic polymers has been a revolution that has led to the annual production of 300 million tons , which, Regarding this last technology, both plastic optical fiber ,10,11 anAnother aspect related to optical fiber sensing is that depending on the location of the sensitive coating along the optical fiber, many different architectures can be found. For example, reflection or transmission optical setups can be considered as two basic configurations; see These two basic configurations can be used to exploit different optical phenomena such as optical absorbance, fluorescence, or evanescent field. They can also be enriched with additional coatings or elements to arrange different configuration such as the ones based on surface plasmon resonance (SPR) , lossy mAs mentioned, polymers are relevant in the fabrication of optical fiber sensors and this review is focused on the two main functions that a polymeric coating can play in the sensing configuration. In the first one, the polymeric matrix can be used as a solid support for the immobilization of a specific chemical transducer. In the second one, the polymeric matrix can be used as the chemical transducer itself . Based oThe aim of this section is to describe some works in which different chemical transducers such as metallic nanoparticles , metal oxide nanoparticles , and luminescent materials  have been immobilized into a polymeric matrix. Polymer engineering allows an enormous flexibility for the design of innovative sensitive coatings and sensors, which are able to measure a wide variety of analytes of importance in the biomedical field, industrial processes, control of water quality or the monitoring of hazardous environments. Photoluminescence is an optical phenomenon which consists of emission of light by a material as a consequence of its previous absorption at lower wavelengths (excitation). As a function of the lifetime of this emission, luminescence can be classified in two different modalities such as fluorescence (lifetime in the range of ps or ns) or well as phosphorescence (lifetime greater than ms). There are a wide variety of luminescent materials  which are entrapped in a specific matrix to promote an adequate interaction between the analyte and the sensing material, and also an efficient coupling of the emitted light to the optical fiber towards the detector. For the development of an adequate luminescent sensor, a good distribution of the luminescent material in this matrix is necessary to avoid an aggregation, causing self-quenching with a loss in the resultant sensitivity . A good approach for the development of luminescent optical fiber sensors involves the entrapment of a suitable sensing reagent in a specific polymeric matrix, for instance by using Layer-by-Layer nano-assembly (LbL) ,27,28,29In I0/I100 = 154.35) to different oxygen concentrations in comparison with the sensor composed of PEI  or the sensor composed of PDDA , as it can be seen in Other work based on the immobilization of PtTFPP by using Layer-by-Layer is focused on the influence of the polyelectrolytes of the polymeric matrix on the surface morphology . In thisAccording to these previous results, the use of Layer-by-Layer assembly is an alternative for an adequate immobilization of luminescent materials due to the high versatility and capability to adjust the resulting properties of the fabricated matrix in comparison with other deposition techniques. This aspect has been also corroborated in work  where thAs previously mentioned, another aspect regarding the LbL technique is its high versatility to entrap diverse types of luminescent materials such as Ruthenium complexes for oxygen sensing applications ,39. In wIn work  the inflAnother interesting work is presented in  where thA work based on crossed optical fiber sensor arrays for dissolved oxygen (DO) concentration measurements is presented in . In thisw/v) aqueous solution) to the flow-cell containing the fiber-fiber junctions immersed in deionized (DI) water, as it can be seen in w/v) BSA solution was added and allowed to interact with the fiber regions in the aqueous medium for 20 min. After this time, oxygen was introduced to the flow cell with a DO concentration of 1.5 ppm. As expected, the Ru complex intensity was quenched; after ∼75 min the sensor was flushed with nitrogen and the Ru complex intensity recovered to the initial values, indicating that no protein binding on the sensor surface occurred. The same trends have been observed with a higher BSA concentration of 5% (w/v), maintaining its recovery time and sensitivity. The results from the nonspecific protein-binding assay show the importance of encapsulating molecules inside the protective PEG-DA matrix, making this sensing material suitable for biological applications. However, this sensor shows vulnerability to metal ions (Fe3+) or notorious oxidizing species (F−), although the sensor response to these interferences is much smaller than the sensor response to oxygen.An important consideration is that the matrix must protect the entrapped indicator from the environment, preventing interference with other agents. One of the research fields of a DO sensor is biological media  where the contamination of the sensor surface with proteins and cells could affect the diffusion of oxygen into the sensor. According to this, the effects of nonspecific protein binding to the PEG-DA-film surface were investigated by the addition of bovine serum albumin  ,47 whichAnother of the most interesting applications related to the use of HPTS is pH sensing ,51,52,53As was mentioned before, the incorporation of nanoparticles can have a high impact on the sensing properties of the polymeric coatings and, in a complementary way, polymers also offer excellent approaches to deposit and immobilize nanoparticles. More specifically, metallic nanoparticles such as gold nanoparticles (AuNPs), silver nanoparticles (AgNPs), are of importance for sensing applications because of the presence of well-located strong absorption bands in both visible or infra-red regions, known as Localized Surface Plasmon Resonance (LSPR). LSPR is the result of the confinement of a surface plasmon in a nanoparticle smaller in comparable in size than the wavelength of the excitation light. This phenomenon can be also seen as a resonant coupling between the incident electromagnetic wave and the surface of the thin-film composed of the metallic nanoparticles. Part of the optical energy is transferred to the free electrons of the metal nanoparticles, resulting in an electromagnetic wave at the metal-dielectric interface and the apparition of sharp absorption peaks at a determined wavelength in the transmitted spectrum ,55. MultOne of the main benefits of using a polymeric protective agent such as Poly (PAA) for the synthesis of metallic nanoparticles is that this weak polyelectrolyte can be used to fabricate a multilayer buildup by using the LbL nano-assembly ,62. OnceDue to the high versatility of the LbL technique it has been also used for the immobilization of other types of metallic nanoparticles such as gold nanoparticles (AuNPs), even using different types of polyelectrolytes as protective agents. The presence of these AuNPs presents additional advantages such as biocompatibility, non-reactivity, good chemical stability, and easiness for a further functionalization ,71. The Another interesting work based on an optical fiber LSPR biosensor by gold nanoparticle assembly in a transmission setup architecture is presented in . In thisA work is presented  which codp) of the biosensor have been evaluated. In addition, secondly, the size of the gold nanoparticles (GNP) in the resultant penetration depth is evaluated. These results are of interest because the LSPR biosensor can be tailored to the biological analyte of interest such as small proteins as well as larger analytes (virus). Another interesting work can be found in [Another aspect to note is that, among the fiber optic geometries in transmission architecture, U-shaped fiber optic probes have shown an important potential due to their high sensitivity, showing an enhancement in comparison with straight probes. According to this, the possibility of combining surface density of the metallic nanoparticles bound to U-bent probes makes possible the design of LSPR optical fiber sensors ,77,78,792. In [It is important to note that the design of LSPR optical fiber sensors based on reflection architecture ,81,82,83In another work, gold nanospheres have been immobilized onto the tip of an optical fiber with the aim to design a LSPR DNA biosensor . A wavelAnother work that combines the sol-gel technique for the immobilization of a specific type of nanoparticles such as palladium nanoparticles and a template of Triton X-100 is presented in  for the Work  presentsAnother different approach for the immobilization of the gold nanoparticles is using a stimuli-responsive hydrogel material which can be employed for measuring volumetric changes or well the binding to receptors on the nanoparticles surface ,90,91. A2) [2) [2-nanospheres film by LbL nanoassembly. The experimental results indicate an exponential dependence of the resonance wavelength shift with humidity not dependent on the temperature, as it can be observed in As it was advanced, not only metal nanoparticles but also metal oxide nanoparticles such silica (SiO2) ,93,94 or2) [2) ,96,97 ca2) [2)  presents2 nanoparticles into a polymeric thin film for humidity sensing on wounds are presented in [2 mesoporous nanoparticles. The sensor shows a decrease in light transmission as relativity humidity increases because of refractive index changes of the coating. In addition, these experimental results provide a faster response to changes in the humidity of the skin microenvironments than a commercial sensor. Other interesting works based on the incorporation of SiOented in ,94. This2 nanoparticles into a polymeric thin film can be found in [Other works that also used the LbL technique for the incorporation of other different types of metal oxide nanoparticles such as TiOfound in ,96,97 fofound in , which p2 coating is presented in 2 nanoparticles onto the multimode optical fiber core [Finally, according to this specific optical phenomenon, an optical fiber refractometer based on LMR supported by a TiOber core . This deIn this section, polymers play an active role in the sensing mechanism, rather than acting as simple support matrix for the active elements. There are many different approaches in which polymers can interact with light and be used as sensitive element in optical fiber sensors. For example, the variation of the effective refractive index of the polymeric film can affect to the evanescent losses of the optical fiber, or create optical interferences, or even can affect to some optical resonances. The active polymer element can modify its morphology , or its optical properties due to different phenomena such as swelling, piezoelectric behavior, or even selective adsorption of small molecules. Therefore, it is very common that a family of polymers, which have a sensitivity to a certain physical, chemical, or biological magnitude, can be used in several optical arrangements and devices, making possible different optical fiber sensors.For example, hydrogels have been very used to create humidity and pH optical fiber sensors. Hydrogels are formed by networks of crosslinked hydrophilic polymer chains that form a tridimensional structure with a high flexibility, and the ability to absorb a high amount of water. This highly hydrophilic characteristic has been used to create evanescent wave optical fiber sensors . In thisOther authors have used the same principle with different optical structures, such as optical fiber gratings, more specifically, Long-Period Gratings (LPGs). These LPG are optical fibers in which a periodic perturbation of the refractive index of the core has been created, with a long period (hundreds of microns) with respect to the standard Fiber Bragg Gratings. This periodical perturbation creates an optical resonance with certain propagating wavelengths that are guided through the cladding of the LPG. This resonance condition is intrinsically sensitive to temperature and strain, as far as both parameters may cause modifications on the grating period, but it is also sensitive to the effective refractive index of the cladding surrounding medium. As the external hydrogel coating modifies its optical properties induced by relative humidity, the resonance wavelength of the LPG cladding modes is also modified . Other aNevertheless, it is not just classic hydrogels that are suitable for this kind of application. Layer-by-Layer (LbL) polymeric assemblies can be used for humidity and pH sensing. Such LbL coatings offer additional advantages since it is possible to keep a very good control of the composition and morphological characteristics of the films independently from the geometry of the substrate. The good control of the LbL sensitive films can be used to create ultra-thin interferometric cavities directly at the end face of perpendicularly cleaved optical fibers . Figure 2O3, is firstly created onto the optical fiber core, and on top of that an external overlay is fabricated using a sensitive polymer [Under certain conditions the polymeric overlays can modify substantially the guiding conditions of the optical fibers, creating interesting optical resonances. As has been previously mentioned in  polymer . The LMR polymer . In some polymer .Other works have used polymeric micro and nano-fibers fabricated by electrospinning. With this technique it is possible to create fibrous membranes for many applications such as filtering, wound dressing, etc. The high specific surface of such nano-webs is very attractive for the sensor field since it could lead to faster and more sensitive devices. For example, there are works in which electrospun nanofibers of polypyrrole and polyethylene oxide (PPy/PEO) are projected over the surface of a 600 µm core optical fiber and then they are exposed to Volatile Organic Compounds (VOCs) such as ammonia, trimethylamine, ethanol, and methanol in the ppm concentration range . The resOther polymers can be found in electrospinning applications for sensors, for example the hydrophilic polymer Poly(acrylic acid) has been used as a relative humidity sensitive overlay , showingAdditionally, there are other optical arrangements in which polymeric thin films can be used to create optical fiber sensors. For example, the Surface Plasmon Resonance (SPR) phenomenon, typically studied using the Kretschmann configuration, can be also implemented into optical fiber setups to reproduce the SPR phenomenon ,114,115.Nevertheless, Molecular Imprinted Polymers (MIPs) are a clear example of polymer engineering success to achieve an innovative non-biological material that can selectively adsorb small molecules. The combination of classical optical fiber SPR sensors with MIPs is a hot topic in the scientific community since it makes possible to obtain highly sensitive and selective sensors. There are many examples of SPR-based optical sensors that uses MIP technology to create their sensitive polymeric layers ,120,121.The possibility of using optical fibers functionalized with chemically sensitive polymeric layers can be employed as an interesting platform for the development of sensing or biosensing applications. A clear example is the use of optical fiber sensors to improve the functionality of medical devices for biomarker detection or drug monitoring because sensitive materials can exhibit changes in their optical properties upon the exposure to an analyte of interest, showing a very fast response with a high degree of sensitivity and selectivity. Finally, due to the high versatility of the optical fiber combined with polymeric layers making possible their implementation in other fields for the detection of chemical as well as physical parameters , it is necessary to have a good control over these parameters in industrial processes. This review is focused on the utilization of polymeric coatings on optical fibers for sensing or biosensing applications. It is well known that optical fiber technology presents several advantages such as the absence of electromagnetic interferences, high degree of miniaturization or capability of remote sensing and multiplexing that other technologies are unable to offer, being an ideal candidate for a wide variety of sensing purposes. The combination of the intrinsic properties related to optical fibers with polymeric sensitive coatings makes possible the fabrication of optical fiber devices with an important enhancement in key factors for sensing applications such as selectivity, sensitivity, response time or even cross-reference measurements. In this work, two different roles which polymers can play for potential sensing applications are evaluated. In the first one, the polymeric matrix is used as a solid support for the immobilization of a specific chemical transducer . In the second one, the polymeric matrix is used directly as a chemical transducer . Finally, in both cases, as a solid support for active polymers, potential applications of the resultant optical fiber sensors in fields as diverse as biology, chemistry, engineering, industry, or medicine are presented.


Examples of the use of the elastic model are presented for the alkali halides, pyroxene, garnet, and bridgmanite solid solutions. Elastic theory provides insights into the microscopic origins of non-ideality in a range of solutions, and can make accurate predictions of excess enthalpies, entropies, and volumes as a function of volume and temperature. In solutions where experimental data are sparse or contradictory, the Helmholtz free energy approach can be used to assess the magnitude of excess properties and their variation as a function of pressure and temperature. The formulation is expected to be useful for geochemical and geophysical studies of the Earth and other planetary bodies.Non-ideality in mineral solid solutions affects their elastic and thermodynamic properties, their thermobaric stability, and the equilibrium phase relations in multiphase assemblages. At a given composition and state of order, non-ideality in minerals is typically modelled via excesses in Gibbs free energy which are either constant or linear with respect to pressure and temperature. This approach has been extremely successful when modelling near-ideal solutions. However, when the lattice parameters of the solution endmembers differ significantly, extrapolations of thermodynamic properties to high pressures using these models may result in significant errors. In this paper, I investigate the effect of parameterising solution models in terms of the Helmholtz free energy, treating volume (or lattice parameters) rather than pressure as an independent variable. This approach has been previously applied to models of order–disorder, but the implications for the thermodynamics and elasticity of solid solutions have not been fully explored. Solid solution models based on the Helmholtz free energy are intuitive at a microscopic level, as they automatically include the energetic contribution from elastic deformation of the endmember lattices. A chemical contribution must also be included in such models, which arises from atomic exchange within the solution. Derivations are provided for the thermodynamic properties of  Thermodynamic and thermoelastic models of minerals and melts underpin our knowledge of the structure and dynamics of the Earth, its evolution through time, and the causes of seismic velocity variations in the deep interior. The physical properties of mineral endmembers are usually well constrained by a significant body of experimental and theoretical work to high pressure and temperature. However, most geologically interesting phases span a compositional range, which can be described as a solid solution of distinct endmembers. The variation of physical properties across these solid solutions is often less well constrained than the properties of the bounding endmembers, and must be approximated  are equal to the sum of endmember potentials multiplied by the molar fractions of each endmember. Unfortunately, for many geologically interesting minerals, mixing is non-ideal, and excess enthalpies In the Earth Sciences, thermodynamic models of solid solutions have typically been formulated as explicit functions of the Gibbs free energy. This is true both of disordered models appropriate at high temperatures  at fixed pressure (P) and temperature (T). Any non-ideality in volume is incorporated via an excess term:In an ideal solution composed of multiple endmembers with molar proportions entclass1pt{minimaQ). In the geological sciences, H allows for non-convergent ordering , a solution of A and B at a given volume will have an elastic energy equal to the molar weighted sum of the endmember elastic energies:V. The resulting entropy S of the solution is then equal to the molar weighted sum of the endmember entropies  Eq.  is attriA, B ...) are dominated by short-range bonding within clusters of n atoms which sit on a distinct exchange site in the lattice  is given by the multinomial distribution:In a solid solution with a completely disordered site with elemental proportions O  the equilibrium relations for the independent set of endmember reactions:The endmembers of the B1-structured alkali halides  have volumes from Interaction enthalpies and volume differences  should inhibit changes in tilting of adjacent mentclass2pt{minimIt has been suggested that elastic energies dominate non-ideality in garnet solid solutions . The agreement between the model and experimental excess entropies within the pyrope–grossular binary is particularly striking. The magnitude of the excesses suggests that the non-configurational Gibbs free energy decreases by almost 50% between room-temperature and typical mantle potential temperatures.In this study, I show that the elastic model formulation behaves well at both high temperatures and high pressures. The inclusion of short-range bonding contributions to the free energy can provide good predictions of excess energies in simple and more complex cubic systems (Sects. “Room-condition excess enthalpies in the alkali halides” and “High The elastic model also places stringent constraints on the variation of material properties within solid solutions which differ from those normally imposed in Gibbs formulations. For example, it has sometimes been assumed that the ratios There are limitations to the elastic model. The model requires that the elastic strain fields due to individual atomic exchanges overlap; this assumption breaks down in dilute alloys (Wood and Blundy


Wireless rechargeable sensor nodes can collect additional data, which leads to an increase in the precision of data analysis, when enough harvested energy is acquired. However, because such nodes increase the amount of sensory data, some nodes  may blackout because more transmitted data can make relaying nodes expend more energy. In this paper, we propose an energy-aware control scheme of data compression and sensing rate to maximize the amount of data collected at the sink, while minimizing the blackout time. In this scheme, each dominant node determines the data quota that all its descendant nodes can transmit during the next period, which operates with an efficient energy allocation scheme. Then, the node receiving the quota selects an appropriate data compression algorithm and sensing rate according to both its quota and allocated energy during the next period, so as not to exhaust the energy of nodes near the sink. Experimental results verify that the proposed scheme collects more data than other schemes, while suppressing the blackout of nodes. We also found that it adapts better to changes in node density and harvesting environments. Wireless sensor networks (WSNs) have been used to collect environmental information in less accessible areas such as hazardous areas, battlefields, or deep water. A wireless sensor network consists of a large number of tiny wireless sensor nodes, which typically have a finite lifetime because they are battery-operated and often discarded when their batteries are exhausted. In WSN, therefore, studies have been actively carried out to extend the lifetime of nodes by reducing their energy consumption ,2.This has motivated the introduction of techniques for prolonging network lifetime using rechargeable nodes that obtain energy from various sources such as the sun, vibration, wind, and temperature differences ,4,5,6. ATo solve this problem, energy prediction ,8,9,10 aKansal et al.  and PiorAnother problem of WSNs is a hot-spot problem ,16, whicThe wireless sensor nodes are implemented as a tiny embedded system, resulting in slower processing speed and less available memory. Existing compression schemes are not suitable for these low-performance devices; therefore, lightweight compression schemes are required for the wireless sensor nodes ,19. SadlIn this paper, we propose a data compression and sensing rate control scheme for wireless rechargeable sensor networks (WRSN) to address the above-mentioned problems and increase the precision of sensory data by increasing the amount of data acquisition. In the proposed scheme, nodes allocate the energy harvested to each time slot. Then, it determines the amount of data to be transmitted, the data compression algorithm, and the sensing period within the allocated energy. The nodes around the sink calculate and announce the transmission data quotas to their descendant nodes, and the descendant nodes collect more data than the quota, compress it to fit the quota, and transmit it. This increases the amount of data acquired in the sink without giving an overhead to the relay nodes on the transmission route.The proposed scheme is appropriate for smart farm , wildfirThe rest of this paper is organized as follows. In We propose a sensing rate control and compression algorithm selection scheme to increase the amount of data gathered within the allocated energy in a WRSN application, which periodically gathers environmental information. In the proposed scheme, sensor nodes divide time into periodic time slots  and allocate energy to the slots. Subsequently, they determine the data quota that can be transmitted within the allocated energy. To prevent the hot-spot problem, 1-hop distance node from the sink (henceforth referred to as the dominant node) limits the amount of relay data by announcing the quota to other nodes, thereby preventing the dominant node from consuming more energy than available. In addition, the nodes selectively compress and transmit data to increase the amount of sensing data within the quota. c and halt when the remaining energy It is assumed that rechargeable nodes have an energy buffer with capacity d is the transmission distance in meters, and α)) is determined by the design of the node.First, the consumed energy a et al. :(2)etx=To obtain the minimum amount of transmission data that prevents the energy buffer from overcharging, the amount of remaining energy at the next slot should be determined. The amount of remaining energy in the battery quations  and 2)  er′ is rIf Equation  is met, l as follows:However, follows:fpacket  lmax thaIf Equation  is satisThe maximum amount of sensing data size excluding the overhead bits In the proposed scheme, each node performs the following operations every slot as shown in Each node determines The sink node periodically broadcasts routing information, and dominant nodes receive it. Then, they relay it including N mode: When the allocated energy is not enough to collect and compress additional data, the node operates in N mode of transferring gathered data without compression. Dominant nodes usually operate only in N mode because they consume more energy than other nodes and cannot save the energy of relay nodes even though they compress the data.L mode: If the allocated energy is sufficient to compress and transmit the data, the node operates in L mode. The node in L mode gathers additional data so that the compressed data is in size of he S-LZW  algorithH mode: In cases where it is expected that a large amount of energy will remain after compressing and transmitting the data, the node gathers more data than the L mode and compresses the data using the energy-intensive compression algorithm. As a result, it gathers more data and consumes more energy for compression than L mode. In this mode nodes compress the data using the S-LZW-BWT  algorithS mode: A dominant node selects S mode to save energy if the determined The nodes that received Nodes periodically collect data, compress, and transmit the data according to the determined mode and the compression algorithm.When a node far from the sink senses and transmits more data using extra energy, all nodes on the path from the node to the sink node consume more energy to deliver the data, resulting in a faster depletion of the energy of the nodes near the sink node. Therefore, we use a method such that dominant nodes limit the amount of traffic by determining and announcing their available transmission data amount to their descendant nodes.n, the amount of data that each descendant node can send n is obtained from historic information so far. The dominant node announces Because a dominant node can transmit up to On the other hand, if Since a node that receives First, the node receiving i cannot transfer all of the data using the allocated energy. Therefore, the node chooses the S mode if the following condition is met:If x bits data in the H mode and L mode, respectively, the consumed energy in the H mode, If a node compresses the sensing data such that the amount of compressed data is If Otherwise, if the following condition is met,quations  and 18)(18)ecL≤eAfter determining the mode, the node must determine the appropriate sensing period to transmit A node in the S mode collects only the minimum amount of data Equation  because Equation  as folloIn this way, each node can gather the amount of data according to the requirements of the dominant node by determining the appropriate sensing period depending on its mode.Algorithm 1: The operation of a dominant node Algorithm 2: The operation of a normal node In the proposed scheme, a node can increase the amount of gathered data within the allocated energy by transmitting only the data of the amount that does not burden the relay nodes as aforementioned in this Section. Algorithms 1 and 2 represent the entire operations of the dominant and normal nodes.We have compared the performance of our scheme with others: (1) no compression (Naive); (2) simply compressing data (S-LZW); (3) advanced compressing data (S-LZW-BWT); (4) selective compressing scheme   instead of the solar energy, the proposed scheme is expected to show good performance by applying the accurate harvested energy prediction and allocation model of the energy source.We proposed a new compression and sensing rate selection scheme for WRSN. In this scheme, a node periodically selects compression algorithm and sensing rate according to its allocated and consumed energy, in order to increase the amount of data arriving at the sink node. Dominant nodes announce data quota to their descendant nodes to prevent excessive traffic. Among the nodes that have received the quota, nodes with sufficient energy gather more data than the quota, compress it and transmit it. As a result, this scheme reduces the number of nodes that blackout and thus allows more data to be obtained. However, the amount of data gathered at the dominant node drastically changes depending on the number of descendants. We plan to consider a routing that distributes the descendant nodes evenly. In addition, this scheme is designed for a flat topology and cannot be used for hierarchical topology such as clustered or layered topology. In the future, we will devise it to apply it to various structures.


This review addresses the comparative effects of skeletal anchored maxillary protraction (MP) versus dental anchored MP. The studies retrieved had to have both test and control groups treated by the use of a facemask with or without the use of skeletal anchorage though either  maxillary or mandibular miniscrews/miniplates, respectively. Nine articles were included. Dentoalveolar changes were seen in all the studies. In particular, a significant proclination of the upper incisors was documented in the group treated with a dental anchorage facial mask, as compared to that treated with skeletal anchorage. Comparing the two methods, almost all the studies indicated a greater maxillary advancement in the group treated with skeletal anchorage. Therapies with skeletal anchorage produce greater maxillary protraction, reducing undesirable dental effects. Skeletal Class III malocclusion is one of the most arduous malocclusions to treat in orthodontics. It can be caused by a retrognathic maxilla, a prognathic mandible, or a combination of both , 2. The The aim of this narrative review is to examine the effectiveness of interceptive treatment of Class III malocclusions using skeletal anchorage and to verify if the treatments with temporary anchored devices (TADs) produce greater maxillary advancement than tooth-anchored maxillary protraction and/or reduce some dental side effects. Since orthopedic treatment of Class III malocclusion often involves maxillary expansion with beneficial effects  or even Articles were identified through a literature survey carried out as a result of the following databases: (1) PubMed, (2) SCOPUS, (3) Latin American and Caribbean Health Sciences (LILACS), (4) Scientific Electronic Library Online (SciELO), and (5) the Cochrane Library. The survey covered the period from inceptions to the last access on 01 November 2017 with no language restrictions. The eligibility assessment was performed independently by two blinded authors. A third author was consulted if necessary.The studies retrieved had to be RCTs or either prospective or retrospective CCTs. They had to include healthy growing subjects treated for skeletal Class III malocclusion by the use of a facemask, with or without maxillary expansion, in the control group, and by the use of skeletal anchorage though either  maxillary or mandibular miniscrews/miniplates in the experimental group. Studies without a control group or with the untreated group were excluded. Publications such as case reports, case series, reviews, and opinion articles were excluded.The following data items were extracted: study design, prospective or retrospective enrolment, sample size, gender distribution, age, Class III description, type of appliance used, indicators of skeletal maturity and distribution of subjects according to growth phase, treatment duration, and when treatment was stopped. Regarding the treatment effects, the following items were also collected: skeletal, dentoalveolar, and soft tissues effects and authors' conclusions on the treatment efficiency. Forms used for data extraction were mostly predefined at the protocol stage by two authors.Low: total score ≤ 7 pointsMedium: total score > 7 and ≤ 10 pointsMedium/high: total score > 10 and ≤ 14 pointsHigh: total score > 14 points.Although this is not a systematic review, a quality analysis of the included studies was performed. As no single approach in assessing methodologic soundness may be appropriate for all reviews , 30, a dA total of 9 studies –28 were Main results in the included studies are summarized in In the study of Aglarci et al. , maxillaCevidanes et al.  found thIn the study of Ge , Co-A shKoh et al.  indicateLee et al.  stated aNgan et al.  declaredSar et al.  describeIn the last study  the meanA clockwise rotation of the mandible with an opening of the mandibular angle was highlighted in the subjects of the group treated with facemask in six studies , 25–28. The analysis of the quality of the studies is shown in Analyzing the data collected by the various studies and the results obtained from the present research, it is possible to make some considerations with the aim of understanding which is the best operative protocol in the orthopedic correction of the skeletal Class III. Maxillary traction using a facemask is the most commonly used method for the resolution of Class III malocclusion . This trThe number of included studies did not allow a full comparison of the effects produced by a maxillary expansion in comparison with MP alone . Similarly, the short term of the available studies and the retrospective nature of several of them  represenConsidering the mixed effects  that characterize the treatments with facemask, these find their best therapeutic usefulness at an early age to make the most of skeletal growth and reduce as far as possible the dental effects. Therapies using skeletal anchorage devices can be considered an effective treatment alternative to achieve maximum skeletal effects and minimal dental effects in patients with severe maxillary retrusion or early loss of deciduous dental elements since the use of the mask alone would cause more proclination of the maxillary incisors and mesialization of the molars with the closure of the spaces. In the subjects near the pubertal peak, it is recommended to use TADs to try to exploit the residual maxillary growth and not to solve the malocclusion with only dental compensations. The presence of skeletal anchors can be exploited at a later time to distalize the upper molars and/or increase the space in the maxillary arch during the fixed therapy phase. The BAMP method is more invasive than the mask, but the use of intraoral elastics is more comfortable and aesthetic and elastic traction can be active 24 hours a day. The clockwise rotation of the mandible is significantly reduced in therapies with TADs. Long-term effects of BAMP, although better than those obtained by MP alone, may still be not enough to treat successfully all the patients. More specifically, it is still not proven that BAMP may successfully treat those unstable patients in the long term.Facemask therapies induce a correction of skeletal Class III malocclusion through a combination of skeletal and dentoalveolar effects.Therapies with skeletal anchorage produce greater maxillary protraction reducing undesirable dental effects.In both groups, the best skeletal effects occur in prepubertal age but in the group with skeletal anchorage, responses are obtained even near the pubertal peak.The results of skeletal anchor devices will need to be verified with more randomized clinical trials and long-term follow-up.


The forces that arise from the actin cortex play a crucial role in determining the membrane deformation. These include protrusive forces due to actin polymerization, pulling forces due to transient attachment of actin filaments to the membrane, retrograde flow powered by contraction of actomyosin network, and adhesion to the extracellular matrix. Here we present a theoretical model for membrane deformation resulting from the feedback between the membrane shape and the forces acting on the membrane. We model the membrane as a series of beads connected by springs and determine the final steady-state shape of the membrane arising from the interplay between pushing/pulling forces of the actin network and the resisting membrane tension. We specifically investigate the effect of the gel dynamics on the spatio-temporal deformation of the membrane until a stable lamellipodium is formed. We show that the retrograde flow and the cross-linking velocity play an essential role in the final elongation of the membrane. Interestingly, in the simulations where motor-induced contractility is switched off, reduced retrograde flow results in an increase in the rate and amplitude of membrane protrusion. These simulations are consistent with experimental observations that report an enhancement in protrusion efficiency as myosin II molecular motors are inhibited. Cell motility is essential for many biological processes including development, immune response, wound healing, phagocytosis and tumor metastasis. In order to crawl, many cells form a wide flat membrane protrusion, known as the lamellipodium, in the direction of movement. The main driving mechanism for lamellipodium formation is the force generated by treadmilling actin network underneath the membrane . Actin tIn the semiflexible region, actin filaments perform thermal fluctuations and exert entropic force on the membrane . These eIn the gel region, the activity is powered by myosin II molecular motors. They bind to the actin filaments and upon ATP hydrolysis create internal stresses that contract the network . These cThe plasma membrane is of central importance in the motility process. It defines the boundary separating the intracellular and extracellular environments, and mediates the interactions between a motile cell and its extracellular matrix. Furthermore, the membrane serves as a dynamic platform for localization of various components which actively participate in all aspects of the motility process, including force generation, adhesion, signaling, and regulation. As actin filaments polymerize and push against the cell membrane from within, membrane tension is build up. Forces on the membrane at any point equilibrate within milliseconds so that, on the time-scales relevant for motility, membrane tension is spatially homogeneous along the leading edge. The net protrusion rate of the membrane is determined by polymerization forces of actin filaments at the leading edge, retrograde flow driven by contraction of the actin gel, cell adhesion to the substrate and the membrane tension that imposes an opposing force on growing actin filaments.A model that accounts for the dynamics of both actin filaments in the semifelxible region and the gel bulk was proposed in , 9 and eThe goal of this study is to start with the simple version of the model introduced in Ref.  and descka, and detach with force dependent rate kd  is the end-to-end distance of the filament, and keff is the effective spring constant of the linker-filament complex. Since the linker and the filament can be considered as two springs placed in series, the effective spring constant of the complex can be written as keff = klkf/(kl + kf). As mentioned above, attached filaments can be compressed or stretched, depending on d and its contour length l. Considering this force, the detachment rate of the filaments from the membrane is given byThe barbed end of each filament is free to fluctuate, polymerize and depolymerize in the SR . In thismembrane . In addifined as kf-1=lp2e length . Attacheribed as fa={-kf(fd and has been discussed extensively in Ref.  pN/nm, with filaments polymerization rate equal to Fe = 12 pN. (a) Non-progressive versus (b) progressive gel boundary with The dynamics of membrane’s middle point versus time for different values of membrane stretching modulus (TIFF)Click here for additional data file.S1 VideoFe = 12 pN and Video of actin polymerization and the membrane response while the gel part is passive. Here the (MOV)Click here for additional data file.S2 VideoFe = 12 pN, Video of actin polymerization and the membrane response in presence of the active gel. Here the (MOV)Click here for additional data file.


Do early-life effects of investments in public health persist to the oldest-old ages? This article answers this question by using the primary care reform in rural Sweden that between 1890 and 1917 led to the establishment of local health districts, together with openings of hospitals and recruitments of medical personnel, as a natural experiment in early-life environmental conditions. The initiatives undertaken within these districts targeted control of infectious diseases, including various isolation and disinfection measures. This study applies a difference-in-differences method combined with propensity score matching to register-based individual-level data for Sweden from 1968 to 2012 and to multisource, purposely collected data on the reform implementation. Providing pioneering evidence for such a distal relationship (ages 78–95), this study finds that treatment through primary care in the year of birth leads to a significant reduction in all-cause mortality (4 % to 6%) and mortality from cardiovascular diseases (5 % to 6 %) and to an increase in average incomes (2 % to 3 %). The effects are universal and somewhat stronger among individuals from poor socioeconomic backgrounds and at higher baseline levels of disease burden.The online version of this article (10.1007/s13524-018-0758-4) contains supplementary material, which is available to authorized users. A response by Barbi and Vaupel (The oldest-old (80+) represent the fastest growing age group in developed countries and are projected to account for one in five older persons by 2050 globally  long term is challenging because survivors tend to be negatively selected  Bleakley  and the Considerable epidemiological evidence suggests that environmental factors in early life influence morbidity and mortality later in life. Among the first, Barker et al.  and BarkThe current study contributes to the literature in several ways. Studies on the role of public health investments at the turn of the twentieth century in the outcomes at old and oldest-old ages are scarce. In rural Sweden, these investments primarily targeted the establishment of primary care facilities around health districts  was organized around an assigned doctor, midwives, and a hospital. Until the mid-nineteenth century, the number of centrally introduced health districts amounted to 2 per 100,000 inhabitants and disproportionally covered the more urbanized locations , which combines the multiple administrative registers for all individuals residing in Sweden from 1968 until 2012 and having family links after 1930, tracked through unique personal identifiers see . The SIPI obtain data on income from the income and taxation register. In the observation period, all individuals, with the exception of those in several earlier cohorts, were under the pension scheme introduced in 1960 that could be claimed beginning at age 67. The scheme provided a flat basic rate with a supplementary benefit determined as a percentage of the average 15 highest paid years Kruse . Althougland) parishes only. I exclude from the analysis the rural parishes that developed through the period into market cities (köping or stad) in order to avoid the overlap with water purification interventions, and I exclude parishes that experienced several health district reallocations or that had uncertain adoption dates . I stop following the establishment of medical districts in 1917, mainly because of the reorganizational character of the reform afterward.Given the rollout of the health district reform, accurate data for the division of the parishes into health districts and its changes are required see , 1939. BIn the individual administrative data, cohorts from 1890–1917 are not linked to their families of origin. To fill the gap in the individual’s background characteristics, which is highlighted as necessary in early-life studies .The establishment of primary care facilities around new health districts can be considered as an improvement in the individual’s early-life environmental conditions. Following the previous literature and in light of the prime focus of the reform on the reduction of exposure to infectious disease, I merge the year of the reform implementation to the year of birth. Given the gradual implementation of the reform throughout parishes in Sweden in 1890–1917, I apply a DiD approach in the following form:hipb(a) denotes the all-cause or cause-specific hazard of death for individual i born in parish p in the birth year b at age a; and hp(a) denotes a set of baseline hazards separate for each parish-of-birth p (strata) that get absorbed into the unspecified function of age. Equation (Equation  can be eEquation . DuratioImplemented sample). Of 2,133 rural parishes, 492 are included into analysis, and the representatives of 414 are eventually observed in the individual data, with no systematic differences compared with those born in the unobserved parishes . Comparing the treated groups with those beyond childhood is not possible because of data limitations.The parishes that implemented the reform between 1890 and 1917 could be distinguished from those that did not implement the reform in this period, with the latter being either (1) located closer to the medical centers, existing prior to 1880, and having substantially larger public health inputs; or (2) established provincial districts much later, after 1917, until the completion of the reform in the mid-1940s. To avoid comparing such dissimilar groups, I include in the baseline sample parishes that established a provincial doctor district at some point in time between 1890 and 1917 , I assign implementation dates to the matched parishes based on their treated counterparts and estimate the coefficients in Eqs.  and the number of individuals who survived to age 78 (from the SIP), I estimate the impact of the reform on the absolute and relative cohort sizes . As expected, I observe a sharp change in the coefficients beginning from the first year of the reform implementation and afterward, pointing to the benefits for those who were in infancy at the time of the reform implementation. Clearly, there are no policy effects for older child ages (ages 1–7). A slightly pronounced effect for individuals age 1 is likely to emerge because the dates of establishment of districts are defined as years, so individuals who are born in the second half of the year were still in their infancy at the start of the district. Noteworthy, the effects are especially strong one year after the opening of a district, consistent with the employment of midwives who were usually recruited after the doctor began to serve the district. The effects become smaller after age 5, pointing to the additional benefits of the reform among pupils, related to the coincidental increase in the investment into primary schooling or doctor-enforced school closures during epidemic outbreaks. The results indicate no diverging health and income trajectories in the pre-reform years. The pattern looks similar for the matched sample, for which the effects emerge only from the first year of the reform implementation.I further investigate the long-term effects with an event study design Fig. . Using dThese estimates represent the intention-to-treat estimates, and I do not directly observe the probability that the individual received the reform treatment. In the models, all individuals born in the parishes where a new health district was opened are considered as treated, and the effects are therefore larger if any smaller proportion of them was treated. A similar set of public health initiatives has been studied for a small local area in southern Sweden that provided a detailed record of participation rates Lazuka . RegardiTable Given the rise in overall social spending starting from the mid-1880s, one might question whether the effects captured are entirely due to the health care reform and not due to other overlapping societal initiatives. As mentioned earlier, the local governments put in place no other public health measures, such as improvements in water facilities, vaccinations, or food hygiene control, until the 1930s. From the data set, I observe that increases in public health investment associated with the introduction of health districts also implied increases in overall social spending. A more careful look suggests that the overwhelming part of the residual local investment was spent on primary schools, which do not directly affect infants or health for those under age 5. Additional resources were also accumulated for poor relief, although they covered only 1.2 % of children under age 15 with direct support . To calculate the social rate of return to the reform, I compare the difference in the discounted incomes at ages 78–95, adjusted with improvements in both survival probabilities and incomes, with the public health investments. I obtain 1890–1917 cohort survival probabilities for ages 78–95 for Sweden from the Human Mortality Database , cohort-ESM 1(PDF 387 kb)


Cell motility is critical to biological processes from wound healing to cancer metastasis to embryonic development. The involvement of organelles in cell motility is well established, but the role of organelle positional reorganization in cell motility remains poorly understood. Here we present an automated image analysis technique for tracking the shape and motion of Golgi bodies and cell nuclei. We quantify the relationship between nuclear orientation and the orientation of the Golgi body relative to the nucleus before, during, and after exposure of mouse fibroblasts to a controlled change in cell substrate topography, from flat to wrinkles, designed to trigger polarized motility. We find that the cells alter their mean nuclei orientation, in terms of the nuclear major axis, to increasingly align with the wrinkle direction once the wrinkles form on the substrate surface. This change in alignment occurs within 8 hours of completion of the topographical transition. In contrast, the position of the Golgi body relative to the nucleus remains aligned with the pre-programmed wrinkle direction, regardless of whether it has been fully established. These findings indicate that intracellular positioning of the Golgi body precedes nuclear reorientation during mouse fibroblast directed migration on patterned substrates. We further show that both processes are Rho-associated kinase (ROCK) mediated as they are abolished by pharmacologic ROCK inhibition whereas mouse fibroblast motility is unaffected. The automated image analysis technique introduced could be broadly employed in the study of polarization and other cellular processes in diverse cell types and micro-environments. In addition, having found that the nuclei Golgi vector may be a more sensitive indicator of substrate features than the nuclei orientation, we anticipate the nuclei Golgi vector to be a useful metric for researchers studying the dynamics of cell polarity in response to different micro-environments. The organization and reorganization of intracellular structures and organelles is key to the complex biological processes of both cell motility and collective cell behaviors at the tissue scale. For example, fixed slide images of stained nuclei and microtubule-organizing centers (MTOCs) have implicated these organelles in fibroblast wound-edge polarization and cell-cell contact polarity . Indeed,in vivo efforts to understand the forces regulating intracellular reorganization, individual cell motility, and collective cell behaviors . The mean of the distribution was then calculated and the process was repeated until the reference angle reached 180°. The mean distribution with the smallest truncated standard deviation was identified as the mean orientation for the system.A uniform random distribution of σKruskal-Wallis nonparametric testing with post-hoc Bonferroni corrections was used for statistical comparisons. A nonparametric design was chosen due to the potentially non-normal distribution of cell data. Significance was determined at 95% and 99% p-values.G, quantifies the amount of space that a cell explores over time [xx and Ryy, which quantify cell exploration along the x and y directions, respectively. By averaging over all cell trajectories and taking a ratio of these two quantities, we generated a metric for the anisotropy of cell trajectories. Values of Rxx/Ryy below unity indicate that cells have traveled farther perpendicular to the x-axis, while values above unity indicate preferential travel along the x-axis direction.The radius of gyration, Rver time . We const0.We calculate the standard directional velocity auto-correlation function:Optical micrographs of an active SMP substrate in its fixed, flat state pre-activation  and subsIVE showed that cells on non-wrinkled substrates have no preference in how they explore space , which is a standard metric for quantifying the persistence time for cell trajectories . The sloIn order to better understand how cells sense and respond to nanotopographies, we measured internal markers for cell polarization and correlated them with the cell motions measured above. We first examined non-wrinkled and wrinkled static substrates . Using bWe next examined the active substrates to quantify the extent to which cells respond to a changing substrate topography. We found that mouse fibroblasts on active substrates have mean nuclei orientations very close to the wrinkle direction at all times, indicating some amount of substrate-sensing during the gradual shape change that occurs before activation, confirmed by polar histograms in Following our characterization of cell orientation on active substrates, we inhibit ROCK activity to determine that both nuclei shape alignment and Golgi-nuclei organization are ROCK-mediated.We first observe that inhibiting ROCK does not change the persistence time for individual cell motion . The dasNext, to quantify directionality, we calculated the ratio of a cell’s velocity along the wrinkle direction compared to perpendicular to that direction, on both active and wrinkled substrates, as shown in We also compared the intracellular organization of uninhibited and ROCK-inhibited cells on wrinkled and active substrates, including the mean nuclei orientation In the present study, we quantified the relationship between nuclei orientation and the orientation of the Golgi body relative to the nucleus before, during, and after exposure to a change in SMP substrate topography designed to trigger polarized motility, and our findings suggest that the displacement vector between the nucleus and Golgi body (NGV) may be a more sensitive indicator of substrate features than the nuclei orientation. The mean orientation of the nuclei and the NGV both direct toward future or pre-existing wrinkles. Interestingly, the spread in the orientation is different between these two internal metrics: while the nuclei orientation becomes increasingly aligned during the gradual and then rapid formation of wrinkles on active substrates, the Golgi-nuclei remains aligned throughout, indicating that the NGV is more sensitive to environmental cues such as substrate strain.These findings suggest that the two distinct metrics—nuclei orientation and the NGV—are differentially sensitive to or respond differently to substrate topography. Specifically, one possibility is that the Golgi location relative to the nucleus, and thus NGV, becomes polarized more easily than nuclei orientation, with the NGV responding to substrate topographies that do not produce a change in nuclei orientation. A second possibility is that these internal polarizations occur on different timescales. In other words, it is possible that the timescale over which the NGV responds to substrate changes is much faster than that of nuclei orientation. Distinguishing these possibilities and determining what anisotropic features of the substrate are being sensed by the cells, even before observable wrinkles form, may reveal NGV as sensitive to and a metric of strain sensing, stiffness or compliance sensing, or even sensing topographic fluctuations that are too small to be quantified with the optical microscopy used in the present work.In this system, which was optimized to image a large number of cells simultaneously, there are fluctuations in image intensity that make the frame-to-frame displacements of nuclei somewhat noisy, and this prevents us from being able to correlate the NGV and nuclei orientation with displacements on a frame-by-frame basis; we instead focused on average quantities within a given time window. Future work could focus on increased resolution of single cells to facilitate a comparison between these two orientation metrics and overall cell displacement.Providing some insight into the mechanisms involved, our data implicates the Rho signaling pathway, as inhibiting ROCK prevents cells from dynamically responding to topographic features on active substrates. ROCK-inhibited cells retain roughly the same truncated standard deviation at all times . CoupledIVE algorithm has broad applicability in organelle and cell analyses. The ACTIVE system has previously been employed in analyzing single and collective cell (mouse fibroblasts and HT1080) motility behaviors on static, two-dimensional patterned surfaces [IVE system is not limited to mammalian cell analysis; it has been adapted in its full form to track E. Coli orientation patterns [IVE system, allowing for novel dual-organelle tracking that will enable insight into how intracellular dynamics directly impact single or collective cell responses.The ACTsurfaces  and in dsurfaces . The segsurfaces . The ACTpatterns  and motipatterns  for biofThe importance of cell motility in development, homeostasis, disease, and healing has been appreciated for some time, but with the advent of tissue engineering, regenerative medicine, and other cell-based therapies there is increased need not only to understand but also to precisely control cell motility. Here we have presented an automated image analysis technique for tracking the shape and motion of Golgi bodies and cell nuclei and to link the Golgi bodies positionally with their respective cell nuclei. We applied the technique to the study of mouse fibroblast polarization in response to changes in substrate topography, but it is important to note that the utility of the technique is not specific to the cell type (fibroblasts), micro-environment (shape-changing SMP topography), or specific process (polarization) we have studied. Moreover, the automated image analysis technique used for tracking the shape and motion of Golgi bodies in the present work could be applied to tracking of other organelles. In addition, the technique was found to be robust and capable of analyzing even low contrast, noisy images . Thus, iIn the present work, we found that the NGV may be a more sensitive indicator of substrate features than the nuclei orientation. Based on our findings, we suggest that this metric could be a complementary tool to understand and control motility in both the fundamental fields of development, homeostasis, disease, and healing and the more emergent and applied fields of tissue engineering, regenerative medicine, and other cell-based therapies. In particular, the metric is anticipated to be useful for researchers studying the dynamics of cell polarity in response to different micro-environments.IVE) [Although some of us had previously developed a software package dedicated to tracking cell nuclei (ACTIVE) , this imhigh and Nlow which are used to calculate the high_out and low_out input parameters for imadjust, respectively. Alternatively default values are provided which may not result in optimal performance. The software will then process the entire tiff stack and appropriately adjust the brightness and contrast to account for experimental effects and remove background noise to provide the best input for the identification component of the package.The first step in this software package appropriately processes lab images to account for experimental features such as phototoxicity or photobleaching. These images are recorded in a tiff stack and imported to MATLAB for analysis. For each image in a movie, we construct a distribution of pixel intensities and perform a Gaussian fit. Our goal is to adjust the brightness and contrast of each image using the imadjust function in MATLAB in an automated fashion. To that end, we estimate the input parameters for imadjust from the Gaussian distributions of pixel intensities, using values N*σ away from the distribution mean, where σ is the standard deviation and N is a user input parameter. The user must identify a value of NAfter the images are suitably prepared, the Golgi bodies must be correctly identified in each frame. To that end we utilize the MATLAB function clusterData , which tIVE software package to link Golgi bodies correctly across frames, again using a distance-based algorithm where positions corresponded to Golgi body centers-of-mass.Following the correct identification of Golgi bodies in individual frames across the course of a time series, we use the same Kilfoil tracking algorithm as the ACTAfter this was complete, we had an identification list for all of the Golgi bodies in each frame and all of the nuclei in each frame. The next portion of the software package looks at each cell nucleus and calculates the distance from it to all Golgi bodies in each frame. The user then inputs a new cutoff distance in pixels to exclude Golgi bodies which are too far away, and look at which Golgi body is, on average, the best candidate for being paired with the current nucleus. We perform this distance-based analysis for all nuclei and compare between them to make sure that there is no overlap in nuclei-Golgi body pairings and also to ensure the best pairings possible. For example, we have nucleus A which is, on average, 10 microns away from its closest Golgi body A throughout the course of the video. However, nucleus B is only 5 microns away from Golgi body A on average throughout the course of the video . In that case, the code checks and sees that the appropriate pairing is nucleus B and Golgi body A, and nucleus A defers to its second best choice assuming that there are no additional conflicts where other nuclei are closer still. This technique was quite successful in appropriately pairing nuclei and Golgi bodies to generate the nuclei Golgi vector (NGV) which is referenced in the manuscript.S1 Fig3 cells per substrate type across 3 technical replicates and 3 biological replicates.Mean cell orientation  and truncated standard deviation  for nuclei orientation  and the axis between the nuclei and Golgi body centers-of-mass  for control mouse fibroblast cells on non-wrinkled (NW), wrinkled (W), and active (A) substrates. (E) Times series for nuclei truncated standard deviation (TSD), showing a similarity between cells on active and non-wrinkled substrates and an increase in TSD over time for cells on wrinkled substrates. Single asterisks (*) indicate significance levels below 0.05, while double asterisks (**) indicate levels below 0.01. There were approximately 10(TIF)Click here for additional data file.S2 FigIn the present work, the nuclear and Golgi live-cell staining was deliberately captured at low signal intensity to reduce phototoxicity and enable extended imaging to 24 h. A representative example of the nuclear (left), Golgi (middle), and RGB false colored (right) images illustrate the resulting low contrast, noisy images, which were successfully processed by the Golgi tracking code, thereby demonstrating the robustness of the approach and the potential for broad application in the study of diverse cell types, diverse micro-environments, and any cellular process involving motion of organelles and cell nuclei.(TIF)Click here for additional data file.S1 Table(PDF)Click here for additional data file.