Elasticity Research Articles

Final Irrigant Temoporfin, Femtosecond Laser, and Chitosan Nanoparticles on Extrusion Bond Strength of Glass Fiber Post, Microhardness, and Modulus of Elasticity of Canal Dentin

Final root canal disinfectants Temoporfin, Femtosecond (FS) laser, and Chitosan nanoparticles (NPs) on marten hardness (MH), modulus of elasticity (EIT), and push-out bond strength (PBS) of glass fiber reinforced post (GFRP) to the root dentin. Sixty caries-free single-rooted human premolars were decoronated and a root canal was performed followed by post space. The specimens were then arbitrarily allocated into groups according to the final disinfectant used. Group 1: 17% EDTA, Group 2: Temoporfin, Group 3: FS laser and Group 4: Chitosan NPs. Evaluation of mechanical properties (MH and EIT) was performed on five samples from each group. Ten samples from each group were bonded with GFRP and sectioned. A universal testing machine and stereomicroscope were used to analyze the PBS and failure mode. Means and standard deviations (SD) of MH, EiT, and PBS were assessed using ANOVA and post hoc Tukey. The highest values of MH and EiT were revealed by 5.25% NaOCl+Chitosan NP samples. The lowest scores of MH and EiT were presented by samples irrigated with 5.25% NaOCl+17% EDTA. The coronal section of samples treated with 5.25% NaOCl+Chitosan NPs showed the highest EBS. Chitosan NPs and FS laser have proved to be valuable alternatives to EDTA as both improved PBS without deteriorating the MH and EiT.

Static and cyclic compressive behaviours of ultra-high performance concrete in cold regions

The stress–strain behaviours of ultra-high performance concrete (UHPC) at varying temperatures are fundamental information for the design and numerical analysis of cold-region structures using UHPC. To obtain the stress–strain relationship and damage evolution of UHPC at low temperatures, a series of low-temperature compression tests were conducted. A total of 21 UHPC cubes and 26 prisms were tested under compression to evaluate the influences of temperatures (T = 20, −30, −60, and − 80 °C), height-to-width ratios (H/B = 1 and 3), and loading conditions (monotonic and cyclic). The test results revealed that the cubic/prism ultimate compressive strength (fcuT or fcT), modulus of elasticity (EcT), and peak strain (ε0T) under monotonic and cyclic compression increased with the decreasing T within 20∼ −80 °C. As T decreased from 20 to −80 °C, the fcuT, fcT, EcT, and ε0T of UHPC under monotonic loading increased by 30.8%, 56.7%, 16.5%, and 15.8%, respectively. The low-temperature increasing rate on EcT and ε0T were very close, but significantly lower than that of compressive strength. In addition, the decreasing T did not affect the plastic strain, stress deterioration ratio, endpoint strain, and stiffness degradation ratio of UHPC under cyclic loading. Through the regression analysis of experimental results, the low-temperature monotonic and cyclic stress–strain constitutive models were developed and validated. The validations against test results showed that the proposed models provided reasonable predictions on monotonic and cyclic σ-ε behaviours of UHPC at low temperatures.

Static compressive stress–strain behaviours of normal weight concrete at Arctic low temperatures

This study experimentally investigated the compressive stress–strain (σ-ε) response of normal weight concrete (NWC) at low temperatures. 72 NWC cubes and 35 NWC prisms in three grades (C25, C45, and C55) were tested under axial compression at four temperature levels (T) of −80, −60, −30, and 20 °C. The failure modes, cubic and prism compressive strength (fcuT and fcT), modulus of elasticity (EcT), and peak strain (ε0T) were studied in detail. In addition, the low-temperature effects of specimen shapes on the compressive strength of NWC were studied. These experimental results reflected that dropping T from ambient temperature to −80 °C did not influence the peak strain of NWC, but significantly increased the fcuT, fcT, and EcT of C55 NWC by 47.3 %, 69.0 %, and 45.3 %, respectively. Finally, prediction equations were established to describe the low-temperature σ-ε constitutive model of NWC. The validations confirmed that the proposed low-temperature compressive constitutive models provided reasonable predictions on the σ-ε behaviours of NWC at a T range of −80 ∼ 20 °C.

Analysis of Stability, Rheological and Structural Properties of Oleogels Obtained from Peanut Oil Structured with Yellow Beeswax.

The aim of this study was to evaluate the macro- and microscopic properties of oleogels with yellow beeswax using different methods, especially modern optical techniques. Microrheological properties, physical stability and morphology of oleogel crystals obtained by structuring of peanut oil with yellow beeswax was analyzed. It was observed that oleogels, even with the smallest concentration of beeswax (2%), were resistant to centrifugal force. Increase in yellow beeswax concentration (from 2, 4, 6 to 8 %) resulted in significant differences in the characteristics of oleogels: increased elasticity (EI), macroscopic viscosity (MVI) and the firmness values of oleogels. It was concluded that non-invasive optical techniques (multi-speckle diffusing wave spectroscopy—Rheolaser Master) are useful in obtaining a quick evaluation of physical properties of oleogels at the microstructural level, and the received information allows for quality assessment.

Nonlinear Conformal Electromagnetism

In 1909 the brothers E. and F. Cosserat discovered a new nonlinear group theoretical approach to elasticity (EL), with the only experimental need to measure the EL constants. In a modern language, their idea has been to use the nonlinear Spencer sequence instead of the nonlinear Janet sequence for the Lie groupoid defining the group of rigid motions of space. Following H. Weyl, our purpose is to compute for the first time the nonlinear Spencer sequence for the Lie groupoid defining the conformal group of space-time in order to provide the mathematical foundations of electromagnetism (EM), with the only experimental need to measure the EM constant in vacuum. With a manifold of dimension n, the difficulty is to deal with the n nonlinear transformations that have been called “elations” by E. Cartan in 1922. Using the fact that dimension n=4 has very specific properties for the computation of the Spencer cohomology, we prove that there is thus no conceptual difference between the Cosserat EL field or induction equations and the Maxwell EM field or induction equations. As a byproduct, the well known field/matter couplings (piezzoelectricity, photoelasticity, streaming birefringence, …) can be described abstractly, with the only experimental need to measure the corresponding coupling constants. The main consequence of this paper is the need to revisit the mathematical foundations of gauge theory (GT) because we have proved that EM was depending on the conformal group and not on U(1), with a shift by one step to the left in the physical interpretation of the differential sequence involved.

Deformation index (GDI) in grain as a criterion for wheat gluten quality

The nutritional benefits of wheat bread largely depend on quality and content of the most valuable part of the grain, its protein complex, namely elastic, and quite extensible gluten. In recent years, there has been a tendency for deterioration of grain quality indicators, namely the indicator ‘gluten quality’ regulated by GOST. There are often the circumstances, when gluten acquires properties of increased viscosity and bran particles are firmly held by gluten proteins. In this case, it is practically impossible to extract it and it is characterized by the term ‘non-extractable’. At the same time, gluten extracted from flour (in the absence of bran) of the same grain sample corresponds to the 1-st and 2-nd classes of quality. Thus, in the first variant, the producers face losses as the grain of the 5th class is non-food, and in the other, we get good grain when gluten is extracted out of flour. The breeders of the research institutions face the similar dilemma when selecting breeding material according to gluten quality. Both different ways of extracting gluten often give opposite effect for the same genotype. The purpose of the current study was to assess the conformity degree of GDI, identified according to GOST according to such indicators as GDI in flour, sedimentation, rheological properties on a mixograph. In order to estimate if wheat is strong, valuable and weak, there is not enough only elastic ity, which is identified using the GDI device (gluten deformation index). The deformation index after extracting gluten is not always an objective result of its quality, therefore, there is a need in additional study, e.g. determination of the gluten deformation index (GDI) in flour, SDS sedimentation, rheological properties of the dough on a mixograph, which characterize gluten ‘strength’ (elasticity, strength, etc.). These methods will allow researchers to estimate the quality of breeding material more efficiently, and agricultural producers will have a comprehensive description of gluten quality of grown grain.

Aspectos biomecânicos e fisiológicos influenciadores no desempenho de judocas

Objetivo: Identificar o efeito de variáveis mecânicas e fisiológicas sobre o nível de desempenho no judô, sendo elas: controle do equilíbrio; força de preensão palmar; altura de salto; potência mecânica muscular dos membros inferiores; índices de elasticidade (IE) e de fadiga (IF). Métodos: Amostra composta por 17 atletas de judô, de ambos os sexos, recrutados de forma intencional e não probabilística. Cada voluntário participou de uma bateria de testes realizada em um único encontro. Foi aplicado o teste de desempenho específico de judô Special Judo Fitness Test – SJFT. Na sequência realizou-se medidas de equilíbrio, preensão palmar e os testes de salto para: avaliação da potência mecânica muscular dos membros inferiores; IE e IF. Utilizou-se o Generalized Linear Model (GLzM). Resultados: Apenas a altura no Squat Jump (A_SJ), que apresentou efeito positivo, e o IE, que apresentou negativo, afetaram o desempenho no SJFT. Conclusão: A A_SJ e o IE afetaram o desempenho no SJFT, sendo que maiores alturas de salto SJ predizem um desempenho aprimorado; e maior contribuição da energia elástica, com valores mais altos de IE, prediz um desempenho piorado. As demais variáveis (potência muscular, altura no Counter-Movement Jump, preensão palmar, equilíbrio e IF) não afetaram o desempenho no SJFT.

Performance Characterization and Pressure Prediction of Compression Socks

Objective of the current research is to develop the mathematical model for the prediction of compression pressure by incorporating some of new but missing variables; circumferential aspect of leg (Lc) and socks (Sc), true stress (σT), true/logarithm strain (eT), true modulus of elasticity (ET), deformed width (Wf) at b ankle position. Socks samples were purchased, hand washed, donned, marked, sliced to loops and then cut to rectangular strips to obtain force-elongation curve at different extensions context to practical elongation. Additionally, all samples were evaluated to analyze the influnce of multiple-machine washes as well as for identification of most influential fabric parameter on compresson pressure, statistically. Standard sized wooden leg (S9=24 cm) attached with pneumatic based sensors (Salzmann MST MK IV) to medial side was used. Force-extension diagram was obtained using Testometric tensile tester. Mathematical models were developed on the basis of principle of Laplace’s law. Developed two models were analyzed and comapred with two existing recently developed models statitistically using MINTAB 17 software.

Energy Absorption, Secant Modulus and Compressive Strength of Fiber Reinforced High Fly Ash Content Cement Treated Soil

This paper presents the results of an experimental investigation that was conducted to study the behavior of fiber-reinforced, high fly ash content and cement treated soil specimens under unconfined compression tests. The effect of fiber inclusions, curing time and fly ash-cement (FA/C) ratio on unconfined compressive strength (UCS), energy absorption (EA), secant modulus of elasticity (ES) and brittleness index (IB) have been studied. Fly ash of 50% and 70%, and cement content of 1.5% and 2% by weight of soil were used in this study. The fly ash and cement as a cementing agent played a significant role in increasing the compressive strength. The unreinforced mix specimens showed a significant improvement in UCS. The fiber inclusions further increased the compressive strength and improved the ductility of the mix specimens. The increase in fiber inclusion was observed to have an increasing effect on UCS, energy absorption, and secant modulus. The increase in curing period (0, 7, 14 and 28 days) also had similar effect on UCS, EA, and ES. However, the increase in fiber content decreased the brittleness index whereas the increase in FA/C ratio increased the brittleness index of the mix specimens. The study suggests a viable method for improving UCS and reduce brittleness of the soil media which may be beneficial for subgrade stabilization.

The Mathematical Foundations of Elasticity and Electromagnetism Revisited

The first purpose of this striking but difficult paper is to revisit the mathematical foundations of Elasticity (EL) and Electromagnetism (EM) by comparing the structure of these two theories and examining with details their known couplings, in particular piezoelectricity and photoelasticity. Despite the strange Helmholtz and Mach-Lippmann analogies existing between them, no classical technique may provide a common setting. However, unexpected arguments discovered independently by the brothers E. and F. Cosserat in 1909 for EL and by H. Weyl in 1918 for EM are leading to construct a new differential sequence called Spencer sequence in the framework of the formal theory of Lie pseudo groups and to introduce it for the conformal group of space-time with 15 parameters. Then, all the previous explicit couplings can be deduced abstractly and one must just go to a laboratory in order to know about the coupling constants on which they are depending, like in the Hooke or Minkowski constitutive relations existing respectively and separately in EL or EM. We finally provide a new combined experimental and theoretical proof of the fact that any 1-form with value in the second order jets (elations) of the conformal group of space-time can be uniquely decomposed into the direct sum of the Ricci tensor and the electromagnetic field. This result questions the mathematical foundations of both General Relativity (GR) and Gauge Theory (GT). In particular, the Einstein operator (6 terms) must be thus replaced by the adjoint of the Ricci operator (4 terms only) in the study of gravitational waves.

Using ultrasound image analysis to evaluate the role of elastography imaging in the diagnosis of carotid atherosclerosis.

Valid characterization of carotid atherosclerosis (CA) is a crucial public health issue, which would limit the major risk held by CA for both patient safety and state economies. CA is typically diagnosed and assessed using duplex ultrasonography (US). Elastrography Imaging (EI) is a promising US technique for quantifying tissue elasticity (ES). In this work, we investigated the association between ES of carotid atherosclerotic lesions, derived from EI, and texture indices, calculated from US image analysis. US and EI images of 23 atherosclerotic plaques (16 patients) were analyzed. Texture features derived from US image analysis (Gray-Scale Median (GSM), plaque area (A) and co-occurrence-matrixderived features) were calculated. Statistical analysis revealed associations between US texture features and EI measured indices. This result indicates accordance in US and EI techniques and states the promising role of EI in diagnosis of CA.

용담화 에탄올 추출물의 항노화 작용 연구

Objective : The goal of this study is to identify the effects of extract of Gentianae sino-ornata (GSO) on the anti-oxidative activity of skin. For this purpose, several functions of GSO were analyzed in terms of skin-lightening activity and wrinkle improvement. Methods : Cell viability was measured by neutral red (NR) assay, and GSO showed highly efficacy in DPPH radical scavenging activity. The level of tyrosinase and matrix metalloproteinase-1 (MMP-1) in media was analyzed by ELISA kit, and the expressions of p-JNK and p-ERK was measured by Western blot. To elucidate inhibitory effects of GSO on melanin synthesis, I determined the tyrosinase activity and melanin production in B16F10 cells. Results : MMP-1 production in UVB-stimulated HDF cells was inhibited by G SO treatments, and also GSO inhibited protein expression levels of p-JNK and p-ERK. GSO significantly reduced tyrosinase activity and melanin synthesis in B16F10 cells. Conclusions : From these results, GSO appears to be effective on skin elasti city increase, wrinkle improvement, whitening as anti-aging activity.

Influence of eNOS gene 4a/b VNTR polymorphism on development of endothelial dysfunction and respiratory system disorders in children – residents of radioactively contaminated areas

Objective is to study the role of еNOS gene polymorphism in the development of endothelial dysfunction and func tional disorders of the respiratory system in children - residents of radioactively contaminated areas. Total of 184 children were examined to determine the possible associative links between еNOS gene intron 4m polymorphism and indices characterizing the functional state of the endothelium and the bronchopulmonary system. Of them the main group of children consisted of 135 children residents of radioactively contaminated areas, the control group - of 49 healthy children who lived in "clean" regions by the radioactive con tamination and were not belonging to victims of the Chernobyl accident contingents. The molecular genetic study determining the еNOS gene intron 4 polymorphism was performed. An examination of lung ventilation capacity was evaluated using the pneumotachography method. The thermographic method was used for registering the endothe lium dependent reaction of the vascular bed to changes in blood supply conditions. The levels of nitrogen com pounds (NO2 and NO3 ) were determined by the standard method using Hriss reagent. The level of body incorporat ed 137Cs was determined using human radiation counter Skrynner 3M (Institute of Human Ecology). Children of the main group did not differ from that of control and literature data by the frequency of geno types 4a/b and еNOS gene allele polymorphism. An increase in the duration of circulation restoration up to the ini tial level after occlusion test was noted in children of the main group with genotype 4a/4b comparing to children with genotype 4b/4b; a decrease in the nitrite content was observed in blood serum. The integral indices of elastic ity and tensility of the lung tissue, respiratory permeability were decreased; the signs of bronchospasm were record ed 1.5 times more often. These adverse effects were associated with the presence of genotype allele 4a, the signs of endothelial dysfunction and the level of the incorporated 137Cs. More pronounced changes in vascular endothelial reaction to occlusion and the significant decrease of serum nitrite level in allele 4a carriers, especially in children who live in adverse ecological conditions, give the right to include them into the risk group for the development of endothelial dysfunction, and to conside pulmonary dysfunction as one of its manifestations.

Effects of Moisture Content on the Mechanical Properties of Moso Bamboo at the Macroscopic and Cellular Levels

To better understand how moisture content (MC) affects the longitudinal compressive mechanical properties of bamboo, mechanical tests on both the macroscopic and cellular levels were performed on Moso bamboo (Phyllostachys pubescens Mazei ex H. de Lebaie) at different MCs. At the macroscopic level, the compressive modulus of elasticity (CMOE) was determined using a common mechanical tester, while the indentation modulus of elasticity (EIT) and the hardness (HIT) of the bamboo fiber cell walls were obtained using nanoindentation. The results showed that CMOE, EIT, and HIT were all negatively correlated with the change in MC below the fiber saturation point (FSP) with strong linear relationships. However, the CMOE was found to be more sensitive to a change in MC than was EIT, which indicated that the bamboo was more sensitive to MC at the macro level than at the cellular level, at least in terms of longitudinal compression stiffness. Moreover, EIT was found to be much less sensitive to a change in MC than was HIT, which may explain why the longitudinal compression strength of bamboo was much more sensitive to changes in MC than was the compression modulus of elasticity on the macro scale.

Dynamic model of a doubly coupled mechatronic system with elasticity and free play

Executive modules in engineering systems may be based on mechatronic principles. A mechatronic module is a functionally and structurally independent component that performs specified motion with the required quality. As applications become more com� plex, interest rises in multiply coupled mechatronic systems. In the present work, we consider a dynamic model of a doubly coupled mechatronic system with elastic� ity and free play in the mechanical transmission, with a view to developing a tool for investigating the pro� cesses in multiply coupled systems. For example, self� oscillation due to the linearity in executive drives has not been sufficiently investigated for systems with mutual influence of the coordinates.

Oscillations of the process described by the telegraph equation for a system consisting of two segments with different densities and elasticities

If the impedances of the two segments of the rod are not equal, then the contact point of these two seg� ments generates a series of reflected and passing waves, which are hard to completely describe. However, the task becomes much easier when the densities, the elas� ticity coefficients, and the lengths of these two seg� ments are chosen so that the segments have equal travel times. In this paper, we present explicit analytic expressions for the solutions of the discontinuous tele� graph equation arising in this case.

Validation of a New Biomechanical Model to Measure Muscle Tone in Spastic Muscles

Background. There is no easy and reliable method to measure spasticity, although it is a common and important symptom after a brain injury. Objective. The aim of this study was to develop and validate a new method to measure spasticity that can be easily used in clinical practice. Methods. A biomechanical model was created to estimate the components of the force resisting passive hand extension, namely (a) inertia (IC), (b) elasticity (EC), (c) viscosity (VC), and (d) neural components (NC). The model was validated in chronic stroke patients with varying degree of hand spasticity. Electromyography (EMG) was recorded to measure the muscle activity induced by the passive stretch. Results. The model was validated in 3 ways: (a) NC was reduced after an ischemic nerve block, (b) NC correlated with the integrated EMG across subjects and in the same subject during the ischemic nerve block, and (c) NC was velocity dependent. In addition, the total resisting force and NC correlated with the modified Ashworth score. According to the model, the neural and nonneural components varied between patients. In most of the patients, but not in all, the NC dominated. Conclusions. The results suggest that the model allows valid measurement of spasticity in the upper extremity of chronic stroke patients and that it can be used to separate the neural component induced by the stretch reflex from resistance caused by altered muscle properties.

IMPACTO DO CRESCIMENTO, DA CONCENTRAÇÃO DA RENDA E DAS TRANSFERÊNCIAS GOVERNAMENTAIS SOBRE A POBREZA NOS MUNICÍPIOS BRASILEIROS

Este artigo estima as elasticidades-renda (advinda do trabalho e das transferências governamentais) e a elasticidade-concentração da renda em relação à pobreza nos municípios brasileiros nos anos de 1991 e de 2000. As elasticidades são calculadas a partir dos coeficientes obtidos por regressão quantílica. Observou-se que as maiores elasticidades são da concentração, depois a elasticidade da renda do trabalho e, finalmente, a elasticidade-renda de transferências governamentais, que apresenta valores muito baixos. As elasticidades renda e concentração diminuíram entre os anos de 1991 e 2000. Principalmente, nos quantis com maior incidência de pobres. Por outro lado, a elasticidades-renda das transferências governamentais aumentaram nos municípios com mais pobres, o que implica este tipo de política tornou-se relativamente mais eficiente na redução da pobreza. O artigo conclui que políticas de combate à pobreza devem ser implementadas considerando as diferentes características apresentadas pelas distribuições de renda nos municípios brasileiros

Biodegradable matrices from regenerated silk of Bombix mori

The structure and biological properties of devices obtained from regenerated fibroin of Bombix mori silk in the form of films, threedimensional matrices, and tubes intended for regenerative medicine were studied. It is shown that regenerated fibroin forms a substrate that maintains adhesion and proliferation of eukary� otic cells by forming a structure that enables homoge� neous distribution of proliferating cells both on the cell surface and in deep matrix layers. The obtained devices are characterized by a high strength and elas� ticity. Matrices implanted into experimental animals undergo diodegradation and neovascularization with time. The properties of devices obtained from regener� ated fibroin allow them to be considered as a base in designing artificial biological analogues of tissue struc� tures. The key problem of modern medicine is the devel�

High and Volatile Commodity Prices: What Do They Mean for Food Prices and Consumers: Discussion

To what degree, and how fast, are changes in commodity prices reflected in changes in re tail food prices? The articles in this session revisit this perennial question in agricultural economics utilizing various data sources, dif ferent commodity and food combinations, and different approaches. Two of the articles use similar data sources (scanner), which include a common product (ready-to-eat cereal) but em ploy different analytical approaches. The third article uses price indices from Bureau of Labor Statistics (BLS). Taken together, the three arti cles show that cost pass through depends on the type of the food in question, the price elastic ity of the product, market structure, and pric ing strategy of processing and retailing firms. The results of the articles suggest that: pass through rates tend to be higher for highly pro cessed foods; commodity prices take four to twenty-seven months to pass through to retail prices; and margins tend to widen during pe riods of rising commodity prices. Because the value of farm commodities constitutes a small fraction of retail prices of processed foods, farm commodities have little influence on the