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This study investigated the extraction of polysaccharide from okra pulp (POP), its chemical components, and rheological properties. The results showed that the optimal extraction temperature, time, and the ration of water to material were 20–30 °C, 30 mins, and 150, respectively, giving a maximum yield of 29.4%. The POP extracted under the mild condition showed different properties. The molecular weight of POP varied from 6436 kDa to 7432 kDa. The GalA/Rha and Gal/Rha in POP suggests the domain of rhamnogalacturonan I with long galactose side chains. The POP presented pseudoplastic shear-thinning behavior, which can be described by the Ostward-DeWaele model. The apparent viscosity of POP decreased with temperature rising from 25 °C to 80 °C. In addition, sucrose, CaCl2, and NaCl led to the reduction of its apparent viscosity which was more sensitive to Ca2+ than to Na+ and sucrose. A closed hysteresis loop was obtained when the POP concentration reached to 6 g/L. The POP showed an elastic behavior (G′ > G″) at concentration of 6 g/L, while it showed predominantly viscous response (G′

Litchi polysaccharide (LP) was extracted from litchi pulp. Its chemical composition, microstructure, zeta potential, flow and viscoelastic behavior were investigated. LP contained uronic acid (41.18%), neutral sugar (42.23%), and protein (2.72%). The monosaccharide composition was mostly arabinose, galactose, and a small amount of mannose, rhamnose and glucose. Scanning electron microscopy (SEM) showed LP was porous network structure. LP concentration had no effect on its zeta potential value while salts reduced them. LP showed shear-thinning behavior during the tested shear rate range. The power-law model was used to evaluate the flow behavior of LP; both its flow behavior index and consistency index changed with different concentrations. The viscosity of LP increased under acidic conditions (pH 2–4), but was stable with heat treatment. The LP dispersion displayed as a liquid viscoelastic behavior in 1% and 2% concentrations and behaved as an elastic gel at 3% concentration as well as the addition of NaCl and CaCl2.

About 0.5 ton of coffee pulp is generated for each ton of coffee cherry processed. In the present study, this waste was investigated as a source of pectin. Coffea arabica L. pulp was dried, treated with ethanol and the pectin extracted with 0.1 M HNO3 (14.6 % yield). Chromatographic, colorimetric and spectroscopic methods were used for pectin characterization. It had 79.5 % galacturonic acid, high methoxyl content (63.2 %), low levels of acetylation, protein and phenolics and Mw of 3.921 × 105 g/mol. The pectin from coffee pulp was able to form gels with high concentration of sucrose or xylitol and low pH. The effect of pH (1.5-3.0), concentrations of pectin (0.5-2.5 %), sucrose (55-65 %) and xylitol (55-60 %) on the viscoelastic properties was investigated. Gels prepared with xylitol diplayed similar viscoelastic behavior to the gels prepared with sucrose. The results demonstrated that coffee pulp is a potential source of commercial pectin with gelling properties.

In this study the effect of residual coagulation medium (water) on cellulose dissolution in an ionic liquid is discussed. Solubility of dissolving grade pulp; HWP and SWP, and microcrystalline cellulose in binary solvents, mixtures of 1-ethyl-3-methyl-imidazolium acetate and water, was investigated by turbidity measurements, light microscopy, rheometry, and CP/MAS (13)C-NMR spectroscopy. The viscoelastic properties of the cellulose solutions imply that residual water affect the cellulose dissolution. However, it is not obvious that this always necessarily poses serious drawbacks for the solution properties or that the effects are as severe as previously believed. Turbidity measurements, viscosity data and crystallinity of the regenerated cellulose correlated well and an increased conversion to cellulose II was found at low water and cellulose contents with an apparent maximum of conversion at 2-5 wt% water. At high water content, above 10 wt%, dissolution and conversion was largely inhibited.

In this study, the application of different dosages of low and high molecular weights (MW) of chitosan (Ch), cationic starch (CS) and poly vinyl alcohol (PVA) were systematically investigated using old corrugated carton (OCC) furnishes. Various sequences of above-mentioned polymeric additives were also examined to find out the optimal combination for improving both wet and dry tensile strength. For each treatment, 4 handsheets, each having basis weight of 100 g/m2, were made. In general, the tensile strength of handsheets was significantly affected by the addition of polymeric agents. The enhancing effect of additives on dry tensile property was much higher than wet condition. The results also showed that the tensile strength of the samples made from OCC furnishes were improved upon the addition of high molecular weight chitosan (ChI) compared to the untreated ones (control). The low MW chitosan did not change the properties of handsheets dramatically. Application of polymeric agents moderately decreased the stretch to rupture, however with increasing dosage the stretch was improved. Sequential addition of used polymers showed that triple application of polymers was beneficial to both dry and wet tensile strength, although the effect was larger for dry. The best results in wet and dry tensile strengths were achieved using sequential of PVA-ChI-CS. Sequential addition of oppositely charged polymers forms a macromolecular layered structure of polyelectrolytes.

Mineralized turkey leg tendon (MTLT) is an attractive model of mineralized collagen fibers, which are also present in bone. Its longitudinal structure is advantageous for the relative simplicity in modeling, yet its anisotropic elastic properties remain unknown. The aim of this study was to quantify the extent of elastic anisotropy of mineralized collagen fibers by using nano- and microindentation to probe a number on MTLT samples in two orthogonal directions. The large dataset allowed the quantification of the extent of anisotropy, depending on the final indentation depth and on the hydration state of the sample. Anisotropy was observed to increase with the sample re-hydration process. Artifacts of indentation in a transverse direction to the main axis of the mineralized tendons in re-hydrated condition were observed. The indentation size effect, that is, the increase of the measured elastic properties with decreasing sampling volume, reported previously on variety of materials, was also observed in MTLT. Indentation work was quantified for both directions of indentation in dried and re-hydrated conditions. As hypothesized, MTLT showed a higher extent of anisotropy compared to cortical and trabecular bone, presumably due to the alignment of mineralized collagen fibers in this tissue., Graphical abstract Highlights ► Assessment of the elastic anisotropy extent in mineralized collagen fibers. ► Two-directional nano- and microindentation of mineralized tissue. ► Effects of hydration state and indentation depth on the stiffness measured with two-directional indentation.

Haversian systems or ‘osteons’ are cylindrical structures, formed by bone lamellae, that make up the major part of human cortical bone. Despite their discovery centuries ago in 1691 by Clopton Havers, their mechanical properties are still poorly understood. The objective of this study is a detailed identification of the anisotropic elastic properties of the secondary osteon in the lamella plane. Additionally, the principal material orientation with respect to the osteon is assessed. Therefore a new nanoindentation method was developed which allows the measurement of indentation data in three distinct planes on a single osteon. All investigated osteons appeared to be anisotropic with a preferred stiffness alignment along the axial direction with a small average helical winding around the osteon axis. The mean degree of anisotropy was 1.75 ± 0.36 and the mean helix angle was 10.3°±0.8°. These findings oppose two well established views of compact bone microstructure: first, the generally clear axial stiffness orientation contradicts a regular ‘twisted plywood’ collagen fibril orientation pattern in lamellar bone that would lead to a more isotropic behavior. Second, the class of transverse osteons were not observed from the mechanical point of view., Graphical abstract Highlights ► Stiffness anisotropy of human osteons. ► Nanoindentation in multiple directions in the lamella plane. ► Strong anisotropy with mainly axial alignment is found. ► Helical winding of principal stiffness orientation is plausible.

The influence of a backmixing operation on the convective belt drying of two wastewater sludges was studied. The expansion of the sludge extrudates bed due to increasing additions of dry product was quantified by using X-ray tomography. This non-invasive technique was used to determine the bed porosity and the total exchange area available for heat and mass transfers, for increasing levels of backmixing. For a same drying flux, the expansion of the drying bed leads to higher drying rates, allowing a reduction of the total drying time. In this context, rheological properties of the sludges are key properties.

The technical properties of three layered cement-bonded boards (CBBs) made from wastepaper and sawdust were investigated. The CBBs were produced at three density levels of 1000, 1200 and 1300 kg/m3 and at four cement/particle ratios of 2.0:1, 2.5:1, 3.0:1 and 3.5:1 on a weight to weight basis. The technical properties evaluated were modulus of rupture (MOR), modulus of elasticity (MOE), water absorption (WA) and thickness swelling (TS). The MOR values ranged from 4.85 to 11.69 MPa and MOE values ranged from 2.80 to 5.57 GPa. The mean values of WA and TS after 24 h of water soaking of the CBBs ranged from 18.18% to 40.49% and 3.55% to 12.13%, respectively. MOR and MOE of the CBBs increased with increase in board density, but MOR decreased with the increase in cement/particle ratio. On the other hand, WA and TS decreased with increase in board density and cement/particle ratio. CBBs produced from wastepaper and sawdust at cement/particle ratios of 3.0:1 and 3.5:1 are suitable for building construction such as paneling, ceiling and partitioning.

This study evaluates whether the mechanical properties of modulus of rupture (MOR) and modulus of elasticity (MOE) of wood-fiber cement (WFC) sheets are correlated with the nondestructive parameters of stress wave velocity and density of the material. Longitudinal stress wave technique was used to evaluate WFC nondestructively using a total of 117 specimens (measuring each 241 x 51 mm) obtained from 39 WFC sheets. The aim was to establish the correlation between dynamic versus static MOE of the material for predicting the actual mechanical property. Even though short dimension specimens were used, results obtained were encouraging. A correlation coefficient (R) of 0.828 was found when the static MOE of the material was used as a function of nondestructive parameters. A multivariate linear regression analysis using the specimen's density, wave velocity, and dynamic MOE provided the strongest correlation to the static MOE. The correlation observed for MOR as a function of static MOE is within the normal range obtained for wood composites. A nondestructive evaluation (NDE) using full size WFC sheets is recommended and can probably improve the relationship between the static and the predicted MOE.

International audience; Background. Constitutive models of the mechanical response of soft tissues have been established and are widely accepted, but models of soft tissues remodeling are more controversial. Specifically for growth, one important question arises pertaining to residual stresses: existing growth models inevitably introduce residual stresses, but it is not entirely clear if this is physiological or merely an artifact of the modeling framework. As a consequence, in simulating growth, some authors have chosen to keep growth-induced residual stresses, and others have chosen to remove them.Methods. In this paper, we introduce a novel “relaxed growth” framework allowing for a fine control of the amount of residual stresses generated during tissue growth. It is a direct extension of the classical framework of the multiplicative decomposition of the transformation gradient, to which an additional sub-transformation is introduced in order to let the original unloaded configuration evolve, hence relieving some residual stresses. We provide multiple illustrations of the framework mechanical response, on time-driven constrained growth as well as the strain-driven growth problem of the artery under internal pressure, including the opening angle experiment.Findings. The novel relaxed growth modeling framework introduced in this paper allows for a better control of growth-induced residual stresses compared to standard growth models based on the multiplicative decomposition of the transformation gradient.Interpretation. Growth-induced residual stresses should 1 be better handled in soft tissues biomechanical models, especially in patient-specific models of diseased organs that are aimed at augmented diagnosis and treatment optimization.

Understanding the mechanical response of the brain to external loadings is of critical importance in investigating the pathological conditions of this tissue during injurious conditions. Such injurious loadings may occur at high rates, for example among others, during road traffic or sport accidents, falls, or due to explosions. Hence, investigating the injury mechanism and design of protective devices for the brain requires constitutive modeling of this tissue at such rates. Accordingly, this paper is aimed at critically investigating the physical background for viscohyperelastic modeling of the brain tissue with scrutinizing the elastic fields pertinent to large, time dependent deformations, and developing a fully nonlinear multimode Maxwell model that can mathematically explain such deformations. The proposed model can be calibrated using the simple monotonic uniaxial deformation of the sample extracted from the tissue, and does not require additional information from relaxation or creep experiments. The performance of the proposed model is examined using the experimental results of two different studies, which reveals a desirable agreement. The usefulness, limitations, and future developments of the proposed model are discussed in this paper.

Tendon-to-bone insertion tissues may be considered as functionally-graded connective tissues, providing a gradual transition from soft tendon to hard bone tissue, and functioning to alleviate stress concentrations at the junction of these tissues. The tendon-to-bone insertion tissues demonstrate pronounced viscoelastic behavior, like many other biological tissues, and are designed by the nature to alleviate stress at physiological load rates and strains states. In this paper we present experimental data showing that under biaxial tension tendon-to-bone insertion demonstrates rate-dependent behavior and that stress-strain curves for the in-plane components of stress and strain become less steep when strain rate is increased, contrary to a typical viscoelastic behavior, where the opposite trend is observed. Such behavior may indicate the existence of a protective viscoelastic mechanism reducing stress and strain during a sudden increase in mechanical loading, known to exist in some biological tissues. The main purpose of the paper is to show that such viscoelastic stress reduction indeed possible and is thermodynamically consistent. We, therefore, propose an anisotropic viscoelasticity model for finite strain. We identify the range of parameters for this model which yield negative viscoelastic contribution into in-plane stress under biaxial state of strain and simultaneously satisfy requirements of thermodynamics. We also find optimal parameters maximizing the observed protective viscoelastic effect for this particular state of strain. This model will be useful for testing and describing viscoelastic materials and for developing interfaces for dissimilar materials, considering rate effect and multiaxial loadings.

This article analyses the effect of different entry regulations on company conduct and traveller behaviour. The paper presents a comprehensive case study of three railway markets with significantly different entry policies using data on prices and frequencies together with a survey conducted to obtain revealed preferences. The study employs data from the three main lines in the Czech Republic. The two open access markets tended to provide significantly higher connection frequencies than the line with regulated entry did. Surprisingly, low price variation across the rail and bus markets suggests low monopoly power for the monopolised incumbent and its uniform price strategy across markets with different entry regulations. On the other hand, high price sensitivity among travellers confirms the importance of intramodal competition. This article analyses the effect of different entry regulations on company conduct and traveller behaviour. The paper presents a comprehensive case study of three railway markets with significantly different entry policies using data on prices and frequencies together with a survey conducted to obtain revealed preferences. The study employs data from the three main lines in the Czech Republic. The two open access markets tended to provide significantly higher connection frequencies than the line with regulated entry did. Surprisingly, low price variation across the rail and bus markets suggests low monopoly power for the monopolised incumbent and its uniform price strategy across markets with different entry regulations. On the other hand, high price sensitivity among travellers confirms the importance of intramodal competition.

The paper presents a set of freight demand elasticities for road, inland waterways and rail transport with respect to a change of total cost of transport, transit time and speed. They can be used in the context of transport policy decisions for estimating the impacts of changes in the cost of transport or the impacts of new infrastructure on traffic or on the modal split for instance. The calculations are based on origin-destination matrixes and networks made available by ETISPlus, a European transport policy information system. The transportation costs and transit times are computed, for each origin-destination relation, each group of commodities and each transportation mode of interest using a transportation network model. A Box-Cox approach transform the explanatory variables for an aggregated conditional logit analysis. If the estimation and validation steps of the models receive a special attention, the most important added value of this paper is probably the in-depth analysis and interpretation of the estimated parameters, and more specifically the optimal λ values used for the Box-Cox transformations. Own and cross elasticities are calculated for costs and transit time changes. All these values are computed at the trans-European level, but also for a large region around the Benelux countries, where there is more competition between the three modes. For this region, the impact of the geographical aggregation level of the O-D matrix (NUTS-2 vs NUTS-3) is also examined. Beside these classical analytical computations, the network model makes it also possible to compute arc elasticities. The obtained values are quasi-identical to the former, but this method allows the computation of ‘composite’ elasticities, which estimate the impact of a variation of a component present in more than one explanatory variables, such as travel speed, that influences both costs and transit times.

The paper is concerned with the development of efficient and accurate solution procedures for the isogeometric boundary element method (BEM) when applied to problems that contain inclusions that have elastic properties different to the computed domain. This topic has been addressed in previous papers but the approach presented here is a considerable improvement in terms of efficiency and accuracy. One innovation is that initial stresses instead of body forces are used, resulting in discretised equations that can be written using matrix–vector multiplications. This allowed a one step solution to be implemented for elastic inclusions. In addition, a novel approach is used for the computation of strains, that avoids the use of highly singular fundamental solutions. Finally, a new type of inclusion is presented that can be used to model reinforcement bars or rock bolts and where analytical integration can be used. Test examples, where results are compared with Finite Element simulations, show that the proposed approach is sound.

The HOLACloud initial 2016 roadmap has been generated by a process similar to that for 2015 using the input to the CLOUD Forward Conference 2016. The analysis of the position papers, and ideas from the scientific papers, provided the synopsis of future R&I (Research and Innovation) topics. These are: advanced systems development method(s) based on model-driven technology; placement and locality of data, software, resources and users; autonomic SLA management pervasively through the software stack including trust, security and privacy; interoperability both across hybrid CLOUD platforms and across heterogeneity of data and software. Business models for CLOUD Computing and beyond featured less prominently than in 2015.

Three-fringe photoelasticity (TFP) is a single isochromatic color image based technique to obtain full-field fringe order data, by comparing RGB intensities of a pixel in the image with the calibration table. Fringe order resolving methods based on neighboring resolved pixels, like refined TFP (RTFP) or window search method, are used to ensure spatial continuity of the fringe order. It is shown in this paper that simple image scanning schemes used to implement such resolving methods result in some unresolved zones for complex shaped specimens that are frequently encountered in industrial applications. A new scanning method termed as advancing front scanning proposed in this paper progresses by resolving a pixel having maximum number of resolved neighboring pixels, starting from a seed point or multiple seed points. Advantages of the advancing front scanning method in conjunction with two-point color adaptation are demonstrated through two examples of specimens of which one is obtained by reflection photoelasticity and the other is a complex simply connected stress frozen slice. � 2013 Elsevier Ltd. All rights reserved.

Characterising soft biological tissues outside the linear viscoelastic regime is challenging due to their complex behaviour. In addition, the viscoelastic properties of tissues have been shown to be sensitive to sample preparation and loading regime resulting in inconsistent data varying by orders magnitude in the literature. This paper presents a novel technique to characterise the non-linear behaviour of tissues which uses Fourier Transformation to decompose the stress output waveform under large amplitude oscillatory shear (LAOS) into harmonic contributions. The effect of varying preload, the compressive strain exerted on a liver tissue specimen prior to shear testing to minimise slip, was also investigated. Results showed that in the linear regime, preload affects the viscoelastic response of liver. Histological analysis indicated that there were structural changes as a result of the preload that may be linked to the differences in observed behaviour. Fourier analysis was used to extract the first and third harmonic components of the shear moduli at large strain. At 50% shear strain, a change in the third harmonic component of the shear moduli was accompanied by a marked change in the micro-structural arrangement of the sinusoids. This paper demonstrates a method of efficiently characterising soft biological tissues under large amplitude oscillatory shear under combined loading.

When a crack or sharp notch is subjected to anti-plane shear loading the boundary conditions negate the transverse shear stress components at the free surfaces and generate a coupled in-plane shear stress field, which can be singular. For sharp V-notches with zero notch opening angle (or cracks) this 3D phenomenon was known for a long period of time. However this mode was largely ignored in stress analysis of notched components. Till now it is still unclear how significant this mode is and whether it has to be taken into consideration in integrity and failure analysis of engineering structures. The present paper is aimed to investigate this singular mode by means of the 3D Finite Element method, which is applied to notched plates with different notch opening angles and plate thicknesses. The stress state associated with the coupled mode is localised and quickly decays with the distance from the notch tip. Therefore, the obtained theoretical results can be applied to a wide range of notched components provided that the boundaries are sufficiently far from the notch tip. Among these results is the effect of the plate thickness on the intensity of the coupled mode; the latter increases with the decrease of the plate thickness. Significance of these new results to failure and integrity assessments of plate and shell components with sharp notches, including through-the-thickness cracks, is discussed in the final section of the paper.

Cell viscoelastic properties are affected by the cell cycle, differentiation, and pathological processes such as malignant transformation. Therefore, evaluation of the mechanical properties of the cells proved to be an approach to obtaining information on the functional state of the cells. Most of the currently used methods for cell mechanophenotyping are limited by low robustness or the need for highly expert operation. In this paper, the system and method for viscoelasticity measurement using shear stress induction by fluid flow is described and tested. Quantitative phase imaging (QPI) is used for image acquisition because this technique enables one to quantify optical path length delays introduced by the sample, thus providing a label-free objective measure of morphology and dynamics. Viscosity and elasticity determination were refined using a new approach based on the linear system model and parametric deconvolution. The proposed method allows high-throughput measurements during live-cell experiments and even through a time lapse, whereby we demonstrated the possibility of simultaneous extraction of shear modulus, viscosity, cell morphology, and QPI-derived cell parameters such as circularity or cell mass. Additionally, the proposed method provides a simple approach to measure cell refractive index with the same setup, which is required for reliable cell height measurement with QPI, an essential parameter for viscoelasticity calculation. Reliability of the proposed viscoelasticity measurement system was tested in several experiments including cell types of different Young/shear modulus and treatment with cytochalasin D or docetaxel, and an agreement with atomic force microscopy was observed. The applicability of the proposed approach was also confirmed by a time-lapse experiment with cytochalasin D washout, whereby an increase of stiffness corresponded to actin repolymerization in time.

Electricity consumption forecast has fundamental importance in the energy planning of a country. In this paper, we present an analysis and two forecast models for nonresidential electricity consumption in Romania. A first part of the paper is dedicated to the estimation of GDP and price elasticities of consumption. Nonresidential short run GDP and price elasticities are found to be approximately 0.136 and −0.0752, respectively, whereas long run GDP and price elasticities are equal to 0.496 and −0.274 respectively. The second part of the study is dedicated to the forecasting of nonresidential electricity consumption up to year 2020. A Holt–Winters exponential smoothing method and a trigonometric grey model with rolling mechanism (TGMRM) are employed for the consumption prediction. The two models lead to similar results, with an average deviation less than 5%. This deviation is to be considered acceptable in relation to the time horizon considered in the present study.

Numerical modeling of localization phenomena shows that constitutive equations with internal length scale are necessary to properly model the post-localization behavior. Moreover, these models allow an accurate description of the scale effects observed in some phenomena like micro-indentation. This paper proposes some analytical results concerning a boundary value problem in a medium with microstructure. In addition to their own usefulness, such analytical solutions can be used in benchmark exercises for the validation of numerical codes. The paper focuses on the thick-walled cylinder problem, using a general small strain isotropic elastic second gradient model. The most general isotropic elastic model involving seven different constants is used and the expression of the analytical solutions is explicitly given. The influence of the microstructure is controlled by the internal length scale parameter. The classical macrostress is no more in equilibrium with the classical forces at the boundary. Double stresses are indeed also generated by the classical boundary conditions and, as far as the microstructure effects become predominant (i.e. the internal length scale is much larger than the thickness of the cylinder), the macrostresses become negligible. This leads to solutions completely different from classical elastic ones.

The influence of economic and demographic variables on the annual electricity consumption in Italy has been investigated with the intention to develop a long-term consumption forecasting model. The time period considered for the historical data is from 1970 to 2007. Different regression models were developed, using historical electricity consumption, gross domestic product (GDP), gross domestic product per capita (GDP per capita) and population. A first part of the paper considers the estimation of GDP, price and GDP per capita elasticities of domestic and non-domestic electricity consumption. The domestic and non-domestic short run price elasticities are found to be both approximately equal to −0.06, while long run elasticities are equal to −0.24 and −0.09, respectively. On the contrary, the elasticities of GDP and GDP per capita present higher values. In the second part of the paper, different regression models, based on co-integrated or stationary data, are presented. Different statistical tests are employed to check the validity of the proposed models. A comparison with national forecasts, based on complex econometric models, such as Markal-Time, was performed, showing that the developed regressions are congruent with the official projections, with deviations of ±1% for the best case and ±11% for the worst. These deviations are to be considered acceptable in relation to the time span taken into account.

Summary Background Twisting (spinal rotation) and bending (flexion) are commonly reported as triggers for low back pain. This paper addresses whether the twisting stress on the annulus fibrosus of the lumbar disk is greater or less than the bending stress for the same angle of twist or bending. Methods Stress–strain relation for transversely isotropic material is applied to the transversely isotropic annulus fibrosus of the lumbar disk to analyze the viscoelastic stresses produced due to 6% compression, 10° twist and 10° bending. Findings The bending stress is 450 times greater than the twisting stress for the same angle of twist or bending of the annulus fibrosus. The twisting and bending moments increase two-fold in quick maneuvers lasting 0.1s (as in high velocity manipulations), compared to slow maneuvers lasting 60s. Interpretation From biomechanical perspective, in situations where both flexion and spinal rotation occur, the stress on the intervertebral disk is markedly higher with flexion compared to rotation. In patients with low back pain that has a disk mediated (discogenic) component, manipulation and mobilization therapies should avoid flexion to minimize stress on the disks. This is particularly relevant for high velocity manipulations where the stress on the disk is doubled for both flexion and rotation. The results in this paper can help guide manual therapists to adjust their treatments to minimize stress on the intervertebral disk.

An automated loading and measurement device has been developed for assessment of the mechanical properties of a healing human tibial fracture. The characteristics of the device are presented with assessments of errors. This paper constitutes a small part of a long term research project determining a clinically quantifiable end point for fracture healing in humans, hence a sample of results is presented to demonstrate the potential application of the device. A more detailed analysis of the results will be the basis of further publications. The initial results confirm that the non-linear behaviour of callus cannot be ignored in fracture assessment methodologies. They further reinforce the requirement to measure load-rate when measuring fracture stiffness. Polar plots of stiffness demonstrate that when measuring fracture stiffness not only should load-rate be considered, but also the orientation of measurement. The results from this work support the view that fracture stiffness should be measured in at least two planes. A new material property for the assessment of fracture healing, the gamma ratio gamma, is examined and preliminary results are shown. The paper also demonstrates how creep properties of a healing tibia can be assessed and proposes that this property may form the basis for future fracture assessment investigations.

This paper works on the analytical development of the method of two-scale asymptotic homogenization. The technique is used to determine the effective elastic stiffnesses of hexagonal honeycomb-cored structural sandwich composite shells made of generally orthotropic materials. Orthotropy of the constituent materials leads to much more complex unit-cell problems and is considered in the present paper for the first time. At first, a 3D-to-2D general shell model based on a set of unit-cell problems is derived. This is followed by the exploitation of the model to the derivation of analytical estimate formulae; used to calculate the force and moment resultants present in the sandwich shell structure. The implication of the general shell model is further indicated by calculating similar design characteristics for a three-layered composite sandwich panel reinforced with hexagonal and triangular shaped cellular core made from the generally orthotropic material.

Unlike engineering fibre composite materials which comprise of fibres that are uniform cylindrical in shape, collagen fibrils reinforcing the proteoglycan-rich (PG) gel in the extra-cellular matrices (ECMs) of connective tissues are taper-ended (paraboloidal in shape). In an earlier paper we have discussed how taper of a fibril leads to an axial stress up-take which differs from that of a uniform cylindrical fibre and implications for fibril fracture. The present paper focuses on the influence of fibre aspect ratio, q (slenderness), and Young's modulus (stiffness), relative to that of the gel phase, ER, on the magnitude of the axial tensile stresses generated within a fibril and wider implications on failure at tissue level. Fibre composite models were evaluated using finite element (FE) and mathematical analyses. When the applied force is low, there is elastic stress transfer between the PG gel and a fibril. FE modelling shows that the stress in a fibril increases with ER and q. At higher applied forces, there is plastic stress transfer. Mathematical modelling predicts that the stress in a fibril increases linearly with q. For small q values, fibrils may be regarded as fillers with little ability to provide tensile reinforcement. Large q values lead to high stress in a fibril. Such high stresses are beneficial provided they do not exceed the fracture stress of collagen. Modulus difference regulates the strain energy release density, u, for interfacial rupture; large ER not only leads to high stress in a fibril but also insures against interfacial rupture by raising the value of u.

This paper constructs two finite element models of human crystalline lens and zonules based on published clinical data. Displacement and pressure were applied to study the mechanism of vision accommodation. The simulation results show that, in Model A, under the pull of the zonules, the thickness of the lens decreased linearly, and the lens diameter increased linearly. The optical power of the lens increased as the zonules displacement increased. Furthermore, the pressure had a remarkable influence on the shape of the lens and the optical power. The lens also became thinner and flatter as the pressure increased. The optical power increased when the pressure increased. In Model B, the lens became thicker and optical power increased as the equatorial zonules stretched. It is basically consistent with Schachar's hypothesis. The outcome of this paper proved that the analytical model presented in this paper can be used in the theoretical study of the accommodation mechanism of the lens.

The objective of this paper is to describe strategies for addressing technical aspects of the computational modeling of ligaments with the finite element (FE) method. Strategies for FE modeling of ligament mechanics are described, differentiating between whole-joint models and models of individual ligaments. Common approaches to obtain three-dimensional ligament geometry are reviewed, with an emphasis on techniques that rely on volumetric medical image data. Considerations for the three-dimensional constitutive modeling of ligaments are reviewed in the context of ligament composition and structure. A novel approach to apply in situ strain to FE models of ligaments is described, and test problems are presented that demonstrate the efficacy of the approach. Approaches for the verification and validation of ligament FE models are outlined. The paper concludes with a discussion of future research directions.

When a mechanical load is applied very rapidly to the thoracic wall, part of the internal damage is suspected to be due to a “high-frequency” injury mechanism, that is, a phenomenon in which waves are involved. This paper addresses a specific high-frequency mechanism for lung injury in which a stress wave is generated through rapid acceleration of the body wall. Displacement-related injuries, which are rather “low-frequency” phenomena, are not considered. The present work was done in the context of assessing behind armor blunt trauma (injury to thoracic organs occurring when a bullet is stopped by a body armor) through mathematical modeling. One aspect of the thorax response to high-speed blunt impact and an associated injury mechanism are investigated based on an idealized model of thorax and a set of computations presented in previous papers. The injury mechanism considered elucidates a possible mathematical relationship between the acceleration at the surface of the thoracic wall and the occurrence of lung injury.

The variations in the stiffness or stiffness contrast of lesions resulting from radiofrequency (RF) ablation of canine liver tissue at different temperatures and for different ablation durations at a specified temperature are analyzed. Tissue stiffness, in general, increases with temperature; however, an anomaly exists around 80 ° C, where the stiffness of the lesion is lower than that of the lesion ablated at 70 °C. On the other hand, the stiffness increases monotonically with the duration of ablation. Plots illustrating the ratio of mean strains in normal canine liver tissue to mean strains in ablated thermal lesions demonstrate the variation in the stiffness contrast of the thermal lesions. The contrast-to-noise ratio (CNRe) of the lesions, which serves as an indicator of the detectability of the lesions under the different experimental imaging conditions described above, is also presented. The results presented in this paper show that the elastographic depiction of stiffer thermal lesions is better, in terms of the CNRe parameter. An important criterion in the elastographic depiction of RF-ablated regions of tissue is the trade-off between ablation temperature and duration of ablation. Tissue necrosis can occur either by ablating tissue to high temperatures for short durations or to lower temperatures for longer durations. In this paper, we attempt to characterize the elastographic depiction of thermal lesions under these different experimental conditions. This paper provides results that may be utilized by practitioners of RF ablation to decide the ablation temperature and duration, on the basis of the strain images of normal liver tissue and ablated thermal lesions discussed in this paper. (E-mail: tvarghese@wisc.edu )

Dentin constitutes the major part of human tooth. It is composed of a large number of tubules with both variational radii and radially parallel pattern. In addition, peritubular dentin surrounds each tubule lumen and has a higher elastic modulus than the matrix of dentin, i.e. intertubular dentin. Considering the above microstructural characteristics, a micromechanics model is used in this paper to evaluate the overall elastic properties of dentin. Five independent effective elastic parameters in transverse isotropic elasticity matrix can be expressed analytically by the material parameters of peri- and intertubular dentin and the volume fraction of tubules. To determine the effectivity of this theoretical model, a finite element (FE) model simulating a longitudinal tooth slice in moire fringe testing of Wang and Weiner (J. Biomech. 31 (1998) 135) was performed. Furthermore, the FE model was developed incorporate modeling of variation of tubule's diameter and softer characteristic of intertubular dentin near the dentin-enamel junction and around the pulp chamber. It turned out that the isoline figure of longitudinal displacement by FE calculation has very similar patterns to the moire fringe results. However, the FE results of displacement by traditional stress-strain models which regard dentin as a homogeneous and isotropic material show an obviously different strain distributions as compared to published moire fringes results. Thus the inhomogeneous and anisotropic model developed in this paper more accurately reflects the true physical nature of human dentin.

In a previous paper [Comput. Methods Appl. Mech. Eng. 191 (2001) 3], the framework for the mechanics of solids, deformable over fractal subsets, was outlined. Anomalous mechanical quantities with fractal dimensions were introduced, i.e. the fractal stress, the fractal strain and the fractal work of deformation. By means of the local fractional operators, the static and kinematic equations were obtained, and the principle of virtual work for fractal media was demonstrated. In this paper, the constitutive equations of fractal elasticity are put forward. From the definition of the fractal elastic potential, the linear elastic constitutive relation is derived. The physical dimensions of the second derivatives of the elastic potential depend on the fractal dimensions of both stress and strain. Thereby, the elastic constants undergo positive or negative scaling, depending on the topological character of deformation patterns and stress flux. The direct formulation of elastic equilibrium is derived in terms of the fractional Lame operators and of the equivalence equations at the boundary. The variational form of the elastic problem is also obtained, through minimization of the total potential energy. Finally, discretization of the fractal medium is proposed, in the spirit of the Ritz–Galerkin approach, and a finite element formulation is obtained by means of devil’s staircase interpolating splines.

Antimicrobial peptides have two binding states in a lipid bilayer, a surface state S and a pore-forming state I. The transition from the S state to the I state has a sigmoidal peptide-concentration dependence indicating cooperativity in the peptide-membrane interactions. In a previous paper, we reported the transition of alamethicin measured in three bilayer conditions. The data were explained by a free energy that took into account the membrane thinning effect induced by the peptides. In this paper, the full implications of the free energy were tested by including another type of peptide, melittin, that forms toroidal pores, instead of barrel-stave pores as in the case of alamethicin. The S-to-I transitions were measured by oriented circular dichroism. The membrane thinning effect was measured by x-ray diffraction. All data were in good agreement with the theory, indicating that the membrane thinning effect is a plausible mechanism for the peptide-induced pore formations.

Acoustic microscopes can be used to measure Rayleigh and longitudinal or P-wave speeds in a specimen at microscopic resolution. The wave speeds are obtained from the interference pattern as a function of the defocus distance or V(z) curve. The received signal voltage amplitude V is generated by two beams––the normally reflected central beam and a non-specularly reflected beam that strikes the fluid–solid interface at critical angle. It is shown in this paper that instead of analyzing the interference pattern between these two beams if we consider two other beams that follow the same path but travel through the coupling fluid multiple times before interfering then the V(z) curve generated by this higher order interference gives more accurate values for the material properties. The spacing distance between two successive dips of the V(z) curve is smaller for the higher order interference. The higher order interference, although weaker, gives more accurate results. Justification for the greater accuracy of the higher order interference is given in the paper. Material properties of silicon and bone are obtained by the new technique. Bones are microscopically heterogeneous and anisotropic. Anisotropic properties of homogeneous specimens can be obtained by the line focus acoustic microscope; however, it does not work when the specimen is microscopically heterogeneous. An attempt has been made here to obtain anisotropic properties of bones using point focus lens.

The free vibration of beams and rods carrying concentrated (lumped) or distributed mass has been extensively investigated in detail for the last three decades. To have an idea about the subject studied in the relevant literature one can refer to the papers listed at the end of this work. Among the vast number of papers, the following can be mentioned. Chen [1] and Goel [2] studied the eigenfrequencies of beams carrying a concentrated mass. Bhat and Wagner [3], and Bhat and Kulkarni [4] obtained the natural frequencies of a cantilevered beam with a slender tip mass. They showed that the gyroscopic elect of the tip mass on the frequencies must be taken into account when its dimensions are considerable compared with those of the carrying beam. Recently, Chan and Zhang [5] studied the free vibration of a cantilever tube partially"filled with liquid, considering it as a beam with distributed mass.Chanet al. [6], and Chan and Wang [7] investigated the free vibration of simply supported and cantilever beams with distributed mass, using Euler}Bernoulli and Timoshenko beam models respectively. Chanet al. [8] treated the free vibration of a beam with two distributed masses in-span. Low [9] derived the frequency equations of a beam with a concentrated mass in-span under classical boundary conditions. Cutchins [10], Batan and Gurgöze [11]dealt with the longitudinal vibrations of rods carrying a concentrated mass. Gürgöze and Inceoglu [12] studied the axial vibration of an elastic rod with external distributed mass. However, it is observed in these works that a system consisting of a mass carried by two different beam segments has not been treated yet. In this paper, a method is presented to obtain the natural frequencies of such a system as shown in Figure 1, due to its practical importance. The general frequency equation derived in the context of this method can also be used to find the eigenfrequencies of the beams either carrying or not carrying a concentrated mass, and non-uniform, two part beams. However, one should remember that the concept of rigidity is an idealization and a theoretical assumption which will not be valid at higher frequencies any more. Therefore, in order to establish a more realistic model for such a system, the intermediate mass must be considered a highly stiff portion of the entire system instead of assuming it ideally rigid.

Simulation of the behaviour of elastic objects in real time is one of the present objectives of computer graphics. One of its fields of application lies in virtual reality, mainly in surgery simulation systems. Models used for the construction of objects with deformable behaviour in computer graphics are known as deformable models. These have two conflicting characteristics: interactivity and movement realism. The deformable models developed up till now have promoted one characteristic to the detriment of the other. In this paper, a new approach is proposed based on boundary element methods (BEM). This is characterised by a positive equilibrium between speed and realism and great robustness. These properties along with the experimental results described in this paper permit one to assert that establishing deformable models with BEM is a reliable method to model objects in virtual reality environments for surgery simulation. In addition to that, the required elasticity parameters could be obtained experimentally through the use of a pig's liver.

Weak particle gels have attracted increasing attention in the last decade. These gels have a very short region of deformation over which their viscoelastic parameters are constant. They can be broken easily in response to external forces. Therefore the rheological measurements in these systems must be performed at very small deformations, which may frequently be below the accuracy limits of conventional rheological instruments. In the present paper we discuss the application of the thickness shear mode resonator technique for the measurement of viscoelastic parameters of weak particle gels in the MHz frequency range. The technique provides information on the viscoelasticity of weak gels in the time scale 10(-7)-10(-9) s. The length scale of the measurements, determined by the depth of penetration and the wavelength of the shear wave, falls in the submicron and micron range. The displacements in the shear deformations generated in this technique are extremely small, in the order of Angstroms, and the shear strain, approximately 10(-3), corresponds to the low limits in the classical dynamic rheology measurements. Only small volumes, down to 0.1 ml, of sample are required and this is another advantage of this technique. The measurements of the storage, G', and the loss, G'', moduli can be carried out non-invasively and continuously at various frequencies in the same sample during the whole length of the process of gelation. General and specific aspects of the measurements and interpretation of experimental results are discussed in the present paper.

The practice of elastography is generally limited to small applied compressions (typically 1%), under the assumption of a linear stress-strain relationship in biological tissue. However, the recent reports of larger applied compressions and precompression levels to increase the strain contrast violate the above assumption. The nonlinear stress-strain relationships in different breast tissue types significantly alter the contrast in elastography, especially for large applied compression. The moduli of normal fibrous and glandular breast tissue (along with cancerous lesions) are strain-dependent, with tissue stiffness increasing with applied compression. In this paper, we illustrate that the strain-dependence of the modulus has a significant impact on the elastographic contrast and on the contrast-to-noise ratio, and may even cause a reversal of the contrast in certain situations. This paper also emphasizes the effect of the precompression strain level on the strain contrast.

The accuracy and precision of the strain estimates in elastography depend on a myriad number of factors. A clear understanding of the various factors (noise sources) that plague strain estimation is essential to obtain quality elastograms. The nonstationary variation in the performance of the strain filter due to frequency-dependent attenuation and lateral and elevational signal decorrelation are analyzed in this and the companion paper for the cross-correlation-based strain estimator. In this paper, we focus on the role of frequency-dependent attenuation in the performance of the strain estimator. The reduction in the signal-to-noise ratio (SNRs) in the RF signal, and the center frequency and bandwidth downshift with frequency-dependent attenuation are incorporated into the strain filter formulation. Both linear and nonlinear frequency dependence of attenuation are theoretically analyzed. Monte-Carlo simulations are used to corroborate the theoretically predicted results. Experimental results illustrate the deterioration in the precision of the strain estimates with depth in a uniformly elastic phantom. Theoretical, simulation and experimental results indicate the importance of high SNRs values in the RF signals, because the strain estimation sensitivity, elastographic SNRe and dynamic range deteriorate rapidly with a decrease in the SNRs. In addition, a shift in the strain filter toward higher strains is observed at large depths in tissue due to the center frequency downshift.

Following a federal policy statement in 2010 supporting bicycle and pedestrian accommodation in federal-aid transportation projects, many cities across the US have implemented Complete Streets principles and invested in developing better-planned infrastructure that can be safely accessed by a diversity of modes of transportation by all types of users, in a mix of land uses. However, most of the travel demand forecasting models and planning tools used in practice are not sensitive to changes in demand for non-motorized modes such as walking and cycling in response to road infrastructure improvements. Hence, there is a need for models and tools that are capable of evaluating impacts of infrastructure changes that include Complete Streets implementations on the travel behavior, and estimate shifts in mode choices from motorized to non-motorized modes. This paper proposes a specific data collection plan, a multi-modal choice model, and strategies to update traditional trip-based transportation models to forecast rates of non-motorized trips for evaluating Complete Streets plans at a higher level. Concretely, we estimate elasticities to Level of Traffic Stress, which defines the comfort or discomfort experienced by walkers and bikers, segmented by income levels and trip purposes. We then use them to compute the new non-motorized mode shares that would be achieved by improving CS attributes leading to lower levels of traffic stress. The proposed modeling framework has been successfully applied to the Maryland Statewide Transportation Model, producing reliable non-motorized trip rates, and can be extended to other methodological frameworks used by public agencies, This research was sponsored by the Maryland Department of Transportation State Highway Administration (Project No: MD-21- SHA/UM/5-25, Erdogan et al., 2021), and the Urban Mobility & Equity Center (UMEC), based at Morgan State University

Hydrogel-based wound dressings have been intensively studied as promising materials for wound healing and care. The mixed-mode thiol-acrylate photopolymerization is used in this paper for alginate/poloxamer hydrogels formation. First, the alginate was modified with thiol groups using the esterification reaction with cysteamine, and second, the terminal hydroxyl groups of poloxamer were esterified with acryloyl chloride to introduce polymerizable acrylate groups. Finally, the cross-linking reaction between the two macromers was performed to produce degradable alginate/poloxamer hydrogels. The optimum conditions for the photo-initiated reaction were studied in order to obtain high gel fractions. The resulting hydrogels have high swelling capacity in simulated physiological conditions, good elasticity and strength, and appropriate porosity, some of the physico-chemical properties required for their applications as wound dressings/patches. The biological assays show that the alginate/poloxamer hydrogels induce proliferation of human keratinocyte and have an anti-inflammatory effect on lipopolysaccharides (LPS)-activated keratinocytes by inhibiting the extracellular signal-regulated kinases (ERK)/ nuclear factor (NF)-kB/ tumor necrosis factor (TNF)-α signalling pathway. Taken together, the results showed that the chemical cross-linked alginate/poloxamer hydrogels may function as a dressing/patch applied directly on the skin lesion to heal the wound by reducing the exacerbated inflammation, the main cause of wound healing delay and local infection.

Cloud computing, with its various extensions, is a significant IT evolution aiming to provide on-demand IT services with an efficient resource usage, but still ensuring service availability and Quality of Service (QoS). Resource elasticity is an effective feature to deal with such issues; it provides the ability to adjust rapidly the deployed resource capacity according to the time-varying workload in order to meet the intended QoS requirements. However relying only on service provider strategies as horizontal and vertical elasticity, seems insufficient to ensure the QoS requirements, since resource usage patterns in Elastic Cloud Systems (ECS) are inherently non-deterministic. This causes difficulties while selecting the elasticity strategy to be applied with respect to QoS parameters. In this paper, we supply solutions for the challenging task of managing ECSs by quantifying the non-determinism on the basis of QoS parameters. Therefore, we define a formal model for specifying cloud systems structure and its dynamics in terms of quality driven elasticity strategies. Besides, a quantitative analysis is performed to evaluate the effectiveness of the proposed model with regard to QoS parameters.

When testing soft biological samples using the Atomic Force Microscopy (AFM) nanoindentation method, the force-indentation data is usually fitted to the equations provided by Hertzian mechanics. Nevertheless, a significant question remains up to date; is this a correct approach from a mathematical perspective? Biological materials are heterogeneous, so 'what do we calculate' when using a classic fitting approach? In this paper, conclusive answers to the abovementioned questions are provided. In addition, a new tool for the nanomechanical characterization of biological samples, the depth-dependent mechanical properties maps, is introduced.

This paper investigates the effect of porosity and unit cell size variation in topology optimized (TOP) and selective laser melting (SLM) fabricated Ti6Al4V lattice structure on the mechanical properties including compressive strength, failure mechanism and dynamic elastic modulus. Meanwhile, mathematical relations between mechanical properties and geometric parameters are obtained based on Gibson-Ashby model. The results show that both ultimate compressive strength (σ = 23∼498 MPa) and dynamic elastic modulus (E = 3.5∼55.47 GPa) of TOP lattice structures gradually decrease with the increase in porosity and unit cell size. The analysis combining experimental and numerical results indicates that TOP lattice structures are elastic-brittle porous material and have two failure mechanisms. The numerical predicted stress-strain curves are compared with the experimental ones. The numerical models incorporating the Johnson-Cook damage model could predict the slip direction of 45° failure band and ultimate compressive strength. Classical Gibson-Ashby model was used to predict the relation between relative density and mechanical properties of lattice structures. The exponential factors (n) of fitted models are obviously affected by unit cell size, which are determined by the number of unit cells in compressive test and SLM manufacturability in dynamic elastic modulus test. A 3D Modulus-Density-Unit Cell Size model is innovatively proposed, which can provide theoretical basis of tailoring orthopedic implant filled with functional gradient TOP lattice structures.

International audience; Scaling ACID transactions in a cloud database is hard, and providing elastic scalability even harder. In this paper, we present our solution for elastic scalable transaction processing in LeanXcale, an industrial-strength NewSQL database system. Unlike previous solutions, it does not require any hardware assistance. Yet, it does scales linearly to 100s of servers. LeanXcale supports non-intrusive elasticity and can move data partitions without hurting the quality of service of transaction management. We show the correctness of LeanXcale transaction management. Finally, we provide a thorough performance evaluation of our solution on Amazon Web Services (AWS) shared cloud instances. The results show linear scalability, e.g., 5 million TPC-C NewOrder TPM with 200 nodes, which is greater than the TPC-C throughput obtained by the 9th highest result in all history using dedicated hardware used exclusively (not shared like in our evaluation) for the benchmark. Furthermore, the efficiency in terms of TPM per core is double that of the two top TPC-C results (also the only results in a cloud).

In this paper, a visco-hyperelastic model representing the mechanical behavior of the human mandibular periosteum as an anisotropic and homogeneous material is identified. Different models, extracted from the literature, are tested and associated in order to describe the elastic and visco-elastic contributions of the cellular matrix on one hand and the collagen fibers on the other hand. The parameters of these models are determined using five human mandibular periosteum. Each harvested sample is cut and tested, at two different velocities, either longitudinally or transversely to collagen fibers main direction. The hyperelastic and visco-elastic contributions of the cellular matrix are extracted using tensile tests performed transversely. The hyperelastic and visco-elastic contributions of the collagen fibers are extracted using tensile tests performed longitudinally. In a second time, the identified combination of models is validated using twelve samples only tested longitudinally. The selected combination uses the simplified Rivlin's 2nd order law to model the hyper-elasticity of the cellular matrix, the Kulkarni's law to model its visco-elasticity contribution, and the Kulkarni's laws to model the whole contributions of collagen fibers.

In biomedical fields, image analysis is often necessary for an accurate diagnosis. In order to obtain all the information needed to form an in-depth clinical picture, it may be useful to combine the contents of images taken under different diagnostic modes. Multimodal medical image fusion techniques enable complementary information acquired by different imaging devices to be automatically combined into a unique image.In this paper, multimodal medical images fusion method based on multiresolution analysis (MRA) is proposed, with the aim to combine the high geometric content of magnetic resonance imaging (MRI) and the elasticity information of magnetic resonance elastography (MRE), simultaneously acquired on the same organs of a patient. First, the slices of MRE are volumetrically interpolated to exactly overlap, each with a slice of MRI. Then, the spatial details of MRI are extracted by means of MRA and injected into the corresponding slices of MRE. Due to the intrinsic dissimilarity between corresponding slices of MRE and MRI, the spatial details of MRI are modulated by local or global matching functions.The performance of the proposed method is quantitatively assessed considering radiometric and geometric consistency of the fused images with respect to their originals, in a comparison with two popular methods from the literature. For a qualitative evaluation, a visual inspection is carried out.The results show that the proposed method enables an effective MRI-MRE fusion that allows the elasticity information and geometric details of the examined organs to be evaluated in a single image.