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In the constrained Cosserat theory of a rod with a rigid cross-section, the balance of angular momentum is satisfied by a restriction on the constitutive equations that requires a second order tensor to be symmetric. The kinematics of the rod are determined by satisfying the balances of linear and director momentum and kinematic constraints. In contrast, the Antman model for a special Cosserat theory of rods proposes constitutive equations directly for the force and mechanical moment applied to the rod and the kinematics are determined by the balances of linear and angular momentum. These two models differ by their treatment of angular momentum. This note poses and answers the question: Are the solutions of these two models identical for the same strain energy? [ABSTRACT FROM AUTHOR]

This paper develops an approximate stress distribution in a conical heap of jammed dry granular material loaded by gravity. An Eulerian formulation of elastic-inelastic response is used to explain why the residual stresses in the heap can be approximated by the current state of stress in the material. The proposed normalized stress components are functions of the normalized radial and vertical coordinates and are parameterized by only the angle of repose. It is shown that the vertical stress distribution applied to the base of the heap compares well with experiments using a rain procedure for sand deposition. [ABSTRACT FROM AUTHOR]

An analytical expression for the strain energy of a constrained extensible Cosserat elastica is developed for general planar shapes and deformations of the rod. This strain energy function naturally couples tangential stretch and reference and current curvatures of the centroidal curve. The model considers a rigid rectangular cross-section of the rod which remains normal to the centroidal curve. The constitutive equations for the tangential force, shear force and bending moment are consistent with a restriction based on the balance of angular momentum that requires a stress-like tensor to be symmetric in a similar manner to the symmetry of the Cauchy stress in a three-dimensional continuum. Examples show that coupling of tangential stretch and reference and current curvatures of the centroidal curve in the new strain energy function can significantly influence predictions of tangential force, shear force and bending moments. [ABSTRACT FROM AUTHOR]

The objective of this classroom note is to propose a generalized model for a compressible elastically isotropic material with elastic-inelastic response. The model is generalized for an exponential Fung-type strain energy with a sum of new higher order elastic distortional deformation invariants that can model elastic-inelastic distortional deformation. In contrast with an Ogden-type model, the coefficients of the proposed higher order invariants do not affect the small deformation response. Moreover, there is no need to determine eigenvalues and eigenvectors of the elastic distortional deformation tensor. Examples show that the equations can model preconditioning of biological tissues as well as elastic instability. [ABSTRACT FROM AUTHOR]

A thermomechanical large deformation Eulerian formulation of a multi-phase soft tissue model with homeostasis and phase transformation has been developed. The model has been simplified by considering a single velocity field and a single temperature field with evolution equations for volume fractions of the phases which are not driven by diffusion. Specific constitutive equations are developed for an exponential form of the Helmholtz free energy. An example of spherical expansion of a three-phase material is considered in the absence of thermal effects. This example considers phase transformations from healthy tissue to a composite of healthy, diseased and necrotic tissues. Although much work is needed to model the mechanobiological aspects of the disease progress, this simplified model indicates that the state of the tissue at the onset of its non-zero volume fraction (i.e. when it begins to influence stress) can significantly effect the resulting stress distribution. [ABSTRACT FROM AUTHOR]

27156207 15 Lampl C. Lamotrigine reduces migraine aura and migraine attacks in patients with migraine with aura. HM and the I CACNA1A i disease spectrum in general, establish a tight link between the pathophysiology behind migraine and epilepsy, underlining the predominant role of presynaptic calcium-mediated neurotransmitters exocytosis burst in causing the neuronal desynchronization responsible for the HM typical hyperexcitability and neurovascular damage [[1]]. Dear Sirs, Hemiplegic migraine (HM) is a rare form of genetic channelopathy presenting as migraine attacks with unilateral motor aura, often accompanied by heterogeneous symptoms i.e., aphasia, sensitive, visual, cerebellar or trigeminal symptoms, according to the International Headache Society [[1]]. [Extracted from the article]

A thermomechanical generalized Cosserat membrane has no resistance to bending but it allows for deformations through the membrane's thickness. This theory is generalized to allow for growth due to mass supply and is constrained to eliminate shear deformations but retain thickness changes. An Eulerian formulation of isothermal elastic-viscoplastic constitutive equations is developed using evolution equations for elastic dilatation and elastic distortional deformations. These evolution equations include time-dependent inelastic effects of homeostasis which cause a tendency for the elastic deformation measures to approach their homeostatic values. An important feature of the Eulerian evolution equations is that they depend only on the current state of the membrane and therefore are appropriate for modeling growth. Examples of zero-stress growth and constrained growth are considered. [ABSTRACT FROM AUTHOR]

The relative attitude change determined from the beginning of each time step to its end defines a relative quaternion. This relative attitude is characterized by only three independent quaterion parameters, with a closed form expression for a fourth dependent parameter as a function of the independent parameters. This procedure ensures that each estimate of attitude is automatically based on a unit quaternion without the need for re-normalization. An example of a complicated three-dimensional motion is used to show that there is no loss in accuracy relative to standard unit and non-unit formulations. Also, an example of Euler integration is used to demonstrate distortion of the rotation matrix due to re-normalization. [ABSTRACT FROM AUTHOR]

The objective of this paper is to generalize an Ogden-type model for elastically isotropic response to include elastic-viscoplastic response. The proposed model uses a strain energy function that depends on the total dilatation and the maximum and minimum elastic distortional stretches. A novel feature of the model is that these elastic distortional stretches are expressed in terms of two independent invariants of an elastic distortional deformation tensor that is determined by an evolution equation. The Cauchy stress is determined by derivatives of the strain energy function, the dilatation and the elastic distortional deformation tensor without the need for determining its principal directions. Examples demonstrate the response of the model for hyperelastic response but the proposed formulation can also model a smooth elastic-plastic transition with rate-independent or rate-dependent response with hardening. [ABSTRACT FROM AUTHOR]

In-situ study of comet 1P/Halley during its 1986 apparition revealed a surprising abundance of organic coma species. It remained unclear, whether or not these species originated from polymeric matter. Now, high-resolution mass-spectrometric data collected at comet 67P/Churyumov-Gerasimenko by ESA's Rosetta mission unveil the chemical structure of complex cometary organics. Here, we identify an ensemble of individual molecules with masses up to 140 Da while demonstrating inconsistency of the data with relevant amounts of polymeric matter. The ensemble has an average composition of C1H1.56O0.134N0.046S0.017, identical to meteoritic soluble organic matter, and includes a plethora of chain-based, cyclic, and aromatic hydrocarbons at an approximate ratio of 6:3:1. Its compositional and structural properties, except for the H/C ratio, resemble those of other Solar System reservoirs of organics—from organic material in the Saturnian ring rain to meteoritic soluble and insoluble organic matter –, which is compatible with a shared prestellar history. A new analysis of Rosetta mass spectra reveals an ensemble of complex organic molecules with striking similarities to other organic reservoirs in the Solar System, including Saturn's ring rain material, pointing at a likely joint prestellar history. [ABSTRACT FROM AUTHOR]

A nonlinear viscoelastic contact interphase is modeled using a Cosserat rod-like string. This Cosserat model is a rod with a deformable cross-section, but with no constitutive resistance to bending. The model allows for axial extension, tangential shear deformation and normal extension of the cross-section which are determined by finite deformations of the interphase. Moreover, the constitutive response of this string model can be determined directly by three-dimensional constitutive equations for a hyperelastic component and a Maxwell elastic-viscoplastic component that together produce viscoelastic response of the interphase. The example of vibrations of a rigid outer ring connected to a fixed inner disk by a nonlinear viscoelastic interphase is used to show that the Cosserat string model of the interface predicts torque and force applied to the outer ring which include nonlinear coupling that is not present in simple uncoupled models of Maxwell components for torque and force applied to the outer ring by the interphase. [ABSTRACT FROM AUTHOR]

This review is focused on the synthetic approaches to the eight-membered nitrogen heterocycles, 1,5-diazocin-2-ones, exhibiting promising biological activities. Nomenclature of these compounds is considered and the examples of the natural and pharmacologically important compounds of the 1,5-diazocin-2-one family are given. Synthetic approaches towards these compounds in accordance with groups and classes of reactions, as well as cascade transformations were systematically analyzed. The review contains 63 references, covering the period from 1955 to early 2021. [ABSTRACT FROM AUTHOR]

Background: We previously demonstrated associations between exercise during pancreatic cancer treatment and quality of life and physical fitness prior to pancreatectomy. In this study, we quantified exercise among survivors following pancreatic tumor resection and characterized concordance with established guidelines. Methods: We quantified exercise frequency, duration, and intensity among survivors who underwent pancreatectomy for adenocarcinoma or a neuroendocrine tumor at our center from 2000 to 2017 and compared them with American College of Sports Medicine Guidelines for Cancer Survivors. Additional surveys measured motivation to exercise, barrier self-efficacy, quality of life, and fatigue. Multivariable models were constructed to evaluate associations between clinicodemographic and psychosocial variables and guideline concordance, and between guideline concordance and quality of life and fatigue. Results: Of 504 eligible survivors, 262 (52%) returned surveys. Only 62 participants (24%) reported meeting both aerobic and strengthening guidelines; 103 (39%) reported meeting neither. Adjusted analyses demonstrated that higher autonomous motivation was associated with higher aerobic and strengthening guideline concordance (both p < 0.01). Higher barrier self-efficacy and older age were associated with higher aerobic guideline concordance (p < 0.01). We identified no significant associations between guideline concordance and tumor type, time since surgery, or recent cancer therapy (all p > 0.05). We found favorable associations between aerobic guideline concordance and both quality of life and fatigue (both p < 0.001). Conclusions: Less than one-quarter of participants exercised sufficiently to meet national exercise guidelines following pancreatectomy. To maximize exercise and related benefits, interventions should help survivors increase intrinsic motivation and overcome barriers to exercise. [ABSTRACT FROM AUTHOR]

An Eulerian thermomechanical elastic–viscoplastic model with isotropic and directional hardening is used to analyse the residual mechanical state resulting from the arc welding of a multi-pass weld. Details of the weld test plate, weld filler material, and numerical implementation of the model are provided, including integration algorithms and consistent tangent modulus. For the computational welding mechanics analyses, the austenitic ASME stainless steel grade 316L was considered so that no phase transformations of solid states needed to be considered. The maximum residual stresses were found to be about 500–600 MPa, which is of the order of the yield stress of the base material. Variations in the heat input and the resulting weld cooling time had a significant influence both on the residual stress state and on the resulting geometry of the weld. The predicted stress levels were compared to the experimental results. Overall, the proposed Eulerian framework seems to be a promising tool for analysing melting/solidification processes and residual mechanical states. [ABSTRACT FROM AUTHOR]

This paper attempts to clarify the notions of a state of pure shear stress and pure shearing deformations. Specifically, it is shown that pure shearing deformations and pure distortional deformations are not equivalent. Attention is limited to isotropic, compressible, hyperelastic materials. Differences between the distortional deformations of pure shearing, pure shear caused by tension and compression, and plane strain extension and contraction defined as pure shear by Rivlin and Saunders (Philos. Trans. R. Soc. Lond. Ser. A, Math. Phys. Sci. 243(865):251–288, 1951) are discussed. It is shown that these deformations are physically different and should not be expected to test the same features of a proposed form of the strain energy function. It is also shown that two deformations of pure shearing and two deformations of pure shear caused by tension and compression are nearly universal distortional deformations valid for all strain energy functions. [ABSTRACT FROM AUTHOR]

The notion of invariance under Superposed Rigid Body Motions (SRBM) is enhanced by a restriction that explicitly states in what sense the responses of a material under SRBM are equivalent. This new restriction is used to develop expressions for the superposed values of the strain energy and the Cauchy stress, instead of assuming their forms. Moreover, it clarifies invariance of the constraint response for kinematic constraints. [ABSTRACT FROM AUTHOR]

New traveling wave solutions are presented for motion of an inextensible, unshearable, planar Kirchhoff beam endowed with rotary inertia and a generalized strain energy function for bending which models nonlinear stiffening and softening. It is shown that although sonic waves (i.e., wave traveling at the bar speed in the beam) do not exist for constant bending stiffness, nonlinear bending stiffness supports new classes of solutions that admit nonlinear waves traveling with axial tension or compression. In addition, it is shown that waves traveling at the bar wave speed may be compactons (i.e., solitary waves of finite span). Surprisingly, for a large class of constant and nonlinear bending stiffness, initially circular rods do not support traveling waves. [ABSTRACT FROM AUTHOR]

The general nonlinear Cosserat theory of a rod allows for tangential shear deformation, axial extension and a deformable cross-section. Simplified equations are obtained by introducing kinematic constraints and associated constraint responses which force the cross-section to remain rigid. The equations of motion of this constrained Cosserat rod are shown to be equivalent to those of Antman's nonlinear special Cosserat theory of a rod. Strain measures motivated by the general Cosserat rod theory are used to develop explicit hyperelastic constitutive equations for the force and moment applied to the rod's ends. [ABSTRACT FROM AUTHOR]

This paper proposes a new isotropic hyperelastic model for polymer foam, which explicitly models the micromechanical influence of changes in porosity. The foam is treated as a matrix of compressible solid material with evacuated pores that cause soft response for low pressures. In its general form, the strain energy of the foam depends on the strain energy of the solid material and on the porosity, which is taken to be a function of the total dilatation. This function adds only two material constants. One is the stress free porosity and the other controls the magnitude of the low pressure response of the foam. In contrast with other formulations, the proposed model naturally transitions to the response of the solid as the porosity approaches zero in hydrostatic compression. [ABSTRACT FROM AUTHOR]

Altered metabolism in pulmonary artery smooth muscle cells (PASMCs) and endothelial cells (PAECs) contributes to the pathology of pulmonary hypertension (PH), but changes in substrate uptake and how substrates are utilized have not been fully characterized. We hypothesized stable isotope metabolomics would identify increased glucose, glutamine and fatty acid uptake and utilization in human PASMCs and PAECs from PH versus control specimens, and that TGF-β treatment would phenocopy these metabolic changes. We used 13C-labeled glucose, glutamine or a long-chain fatty acid mixture added to cell culture media, and mass spectrometry-based metabolomics to detect and quantify 13C-labeled metabolites. We found PH PASMCs had increased glucose uptake and utilization by glycolysis and the pentose shunt, but no changes in glutamine or fatty acid uptake or utilization. Diseased PAECs had increased proximate glycolysis pathway intermediates, less pentose shunt flux, increased anaplerosis from glutamine, and decreased fatty acid β-oxidation. TGF-β treatment increased glycolysis in PASMCs, but did not recapitulate the PAEC disease phenotype. In TGF-β-treated PASMCs, glucose, glutamine and fatty acids all contributed carbons to the TCA cycle. In conclusion, PASMCs and PAECs collected from PH subjects have significant changes in metabolite uptake and utilization, partially recapitulated by TGF-β treatment. [ABSTRACT FROM AUTHOR]

The rari-constant theory of linear elasticity is based on the assumption that elasticity in solids is caused by only pair potentials with coaxial forces acting between atoms. The strain energy of each pair potential depends on the square of the strain between the atoms in the pair. This strain can be determined by taking the inner product of the strain tensor with a structural tensor that is the tensor product of a unit vector with itself. It is shown that the 15 independent constants in the rari-constant theory can be generated by a complete set of 15 structural tensors. It is also shown that the 6 additional independent constants in the multi-constant theory can be generated by taking the inner product of 6 of these structural tensors with the square of the strain tensor. A generalization of these results for nonlinear elasticity is discussed with reference to recent work which compares the structural and generalized structural tensor approaches to modeling fibrous tissues. [ABSTRACT FROM AUTHOR]

Simo (Comput Methods Appl Mech Eng 66:199-219, 1988) proposed an evolution equation for elastic deformation together with a constitutive equation for inelastic deformation rate in plasticity. The numerical algorithm (Simo in Comput Methods Appl Mech Eng 68:1-31, 1988) for determining elastic distortional deformation was simple. However, the proposed inelastic deformation rate caused plastic compaction. The corrected formulation (Simo in Comput Methods Appl Mech Eng 99:61-112, 1992) preserves isochoric plasticity but the numerical integration algorithm is complicated and needs special methods for calculation of the exponential map of a tensor. Alternatively, an evolution equation for elastic distortional deformation can be proposed directly with a simplified constitutive equation for inelastic distortional deformation rate. This has the advantage that the physics of inelastic distortional deformation is separated from that of dilatation. The example of finite deformation $$\hbox {J}_{2}$$ plasticity with linear isotropic hardening is used to demonstrate the simplicity of the numerical algorithm. [ABSTRACT FROM AUTHOR]

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Optoelectronic plethysmography (OEP) is a noninvasive method for assessing lung volume variations and the contributions of different anatomical compartments of the chest wall (CW) through measurements of the motion of markers attached to the CW surface. The present study proposes a new method for analyzing the local CW kinematics from OEP measurements based on the kinematics of triangular Cosserat point elements (TCPEs). 52 reflective markers were placed on the anterior CW to create a mesh of 78 triangles according to an anatomical model. Each triangle was characterized by a TCPE and its kinematics was described using four time-variant scalar TCPE parameters. The total CW volume ( $$V_{\text{TCW}}$$ ) and the contributions of its six compartments were also estimated, using the same markers. The method was evaluated using measurements of ten healthy subjects, nine patients with Pompe disease, and ten patients with Duchenne muscular dystrophy (DMD), during spontaneous breathing (SB) and vital capacity maneuvers (VC) in the supine position. TCPE parameters and compartmental volumes were compared with $$V_{\text{TCW}}$$ by computing the phase angles $$\theta$$ (for SB) and the correlation r (for VC) between them. Analysis of $$\theta$$ and r of the outward translation parameter $$P_{\text{T}}$$ of each TCPE revealed that for healthy subjects it provided similar results to those obtained by compartmental volumes, whereas for the neuromuscular patients the TCPE method was capable of detecting local asynchronous and paradoxical movements also in cases where they were undistinguished by volumes. Therefore, the TCPE approach provides additional information to OEP that may enhance its clinical evaluation capabilities. [ABSTRACT FROM AUTHOR]

A highly efficient synthetic route to 6,7-dihydro-1 H-cyclopenta[ gh]perimidines has been proposed on the basis of a novel reaction of nitroalkanes with 4,5-diaminoacenaphthene in the presence of polyphosphoric acid. The reaction involves phosphorylation of the aci-nitro compound, followed by intramolecular cyclization. [ABSTRACT FROM AUTHOR]

Hypoparathyroidism (HypoPT) is an uncommon endocrine disorder characterized by chronic deficiency or absence of parathyroid hormone (PTH), which leads to a profound reduction in bone remodeling. Subjects with HypoPT typically have bone mineral densities (BMDs) by dual-energy X-ray absorptiometry (DXA) above average at all skeletal sites, with greatest scores observed at the lumbar spine. Trabecular bone score (TBS), an indirect measure of bone microarchitecture, also appears to be normal in HypoPT. By peripheral quantitative computed tomography (pQCT) of the radius, volumetric BMD at cancellous and cortical compartments, as well as cortical area and thickness, are greater in hypoparathyroid subjects than in controls. The use of high-resolution pQCT (HRpQCT) confirmed the increase in cortical volumetric BMD but demonstrated reduced cortical thickness, associated with lower cortical porosity in HypoPT. Trabeculae tend to be more numerous but thinner in hypoparathyroid subjects. It is not clear whether these structural and the dynamic skeletal abnormalities in HypoPT affect bone strength or fracture risk. Treatment of HypoPT with PTH leads to improvement in bone remodeling rate, variable changes in bone density, and a transient increase in estimated bone strength. The effect of PTH therapy on fracture risk remains unknown. This article reviews skeletal involvement and the effect of PTH treatment in patients with HypoPT, as assessed by DXA, TBS, QCT, and HRpQCT. Data on bone strength and fracture risk in HypoPT are also reviewed here. [ABSTRACT FROM AUTHOR]

The Ogden model for an incompressible isotropic hyperelastic material is versatile enough to match complicated data for rubber-like materials at large deformations. However, the tensorial expression for the Cauchy stress in the Ogden model requires determination of the eigenvalues and eigenvectors of the left Cauchy-Green deformation tensor $\mathbf{B}$ . The objective of this paper is to propose an invariant-based Ogden-type model for isotropic incompressible hyperelastic materials. The strain energy function in this new model depends on classical invariants of $\mathbf{B}$ and the Cauchy stress tensor can be expressed directly in terms of the tensor $\mathbf{B}$ without need for its spectral form. Examples show that this new Ogden-type model retains the versatility of the original Ogden model in characterizing material response. [ABSTRACT FROM AUTHOR]

The HMK model (Hunter et al. in Prog Biophys Mol Biol 69:289-331, ) proposes mechanobiological equations for the influence of intracellular calcium concentration $$\hbox {Ca}_\mathrm{i}$$ on the evolution of bound calcium concentration $$\hbox {Ca}_\mathrm{b}$$ and the tropomyosin kinetics parameter z, which model processes in the active component of the tension in cardiac muscle. The inelastic response due to actin-myosin crossbridge kinetics is modeled in the HMK model with a function Q that depends on the history of the rate of total stretch of the muscle fiber. Here, an alternative model is proposed which models the active component of the muscle fiber as a viscoplastic material. In particular, an evolution equation is proposed for the elastic stretch $$\lambda _\mathrm{a} $$ in the active component. Specific forms of the constitutive equations are proposed and used to match experimental data. The proposed viscoplastic formulation allows for separate modeling of three processes: the high rate deactivation of crossbridges causing rapid reduction in active tension; the high but lower rate reactivation of crossbridges causing recovery of active tension; and the low rate relaxation effects characterizing the Hill model of muscles. [ABSTRACT FROM AUTHOR]

A large deformation thermomechanical model is developed for shock loading of a material that can exhibit elastic and inelastic anisotropy. Use is made of evolution equations for a triad of microstructural vectors $$\mathbf{m}_{\mathrm{i}}\,(\hbox {i}=1,2,3)$$ which model elastic deformations and directions of anisotropy. Specific constitutive equations are presented for a material with orthotropic elastic response. The rate of inelasticity depends on an orthotropic yield function that can be used to model weak fault planes with failure in shear and which exhibits a smooth transition to isotropic response at high compression. Moreover, a robust, strongly objective numerical algorithm is proposed for both rate-independent and rate-dependent response. The predictions of the continuum model are examined by comparison with exact steady-state solutions. Also, the constitutive equations are used to obtain a simplified continuum model of jointed rock which is compared with high fidelity numerical solutions that model a persistent system of joints explicitly in the rock medium. [ABSTRACT FROM AUTHOR]

Accurate estimation of the position and orientation (pose) of a bone from a cluster of skin markers is limited mostly by the relative motion between the bone and the markers, which is known as the soft tissue artifact (STA). This work presents a method, based on continuum mechanics, to describe the kinematics of a cluster affected by STA. The cluster is characterized by triangular cosserat point elements (TCPEs) defined by all combinations of three markers. The effects of the STA on the TCPEs are quantified using three parameters describing the strain in each TCPE and the relative rotation and translation between TCPEs. The method was evaluated using previously collected ex vivo kinematic data. Femur pose was estimated from 12 skin markers on the thigh, while its reference pose was measured using bone pins. Analysis revealed that instantaneous subsets of TCPEs exist which estimate bone position and orientation more accurately than the Procrustes Superimposition applied to the cluster of all markers. It has been shown that some of these parameters correlate well with femur pose errors, which suggests that they can be used to select, at each instant, subsets of TCPEs leading an improved estimation of the underlying bone pose. [ABSTRACT FROM AUTHOR]

An Eulerian formulation has been developed for the constitutive response of a group of materials that includes anisotropic elastic and viscoelastic solids and viscous fluids. The material is considered to be a composite of an elastic solid and a viscous fluid. Evolution equations are proposed for a triad of vectors m that represent the stretches and orientations of material line elements in the solid component. Evolution equations for an orthonormal triad of vectors s are also proposed to characterize anisotropy of the fluid component. In particular, for an elastic solid it is shown that the material response is totally characterized by the functional form of the strain energy and by the current values of m, which are measurable in the current state of the material. Moreover, it is shown that the proposed Eulerian formulation removes unphysical arbitrariness of the choice of the reference configuration in the standard formulation of constitutive equations for anisotropic elastic solids. [ABSTRACT FROM AUTHOR]

An isotropic three-dimensional nonlinear viscoelastic model is developed to simulate the time-dependent behavior of passive skeletal muscle. The development of the model is stimulated by experimental data that characterize the response during simple uniaxial stress cyclic loading and unloading. Of particular interest is the rate-dependent response, the recovery of muscle properties from the preconditioned to the unconditioned state and stress relaxation at constant stretch during loading and unloading. The model considers the material to be a composite of a nonlinear hyperelastic component in parallel with a nonlinear dissipative component. The strain energy and the corresponding stress measures are separated additively into hyperelastic and dissipative parts. In contrast to standard nonlinear inelastic models, here the dissipative component is modeled using an evolution equation that combines rate-independent and rate-dependent responses smoothly with no finite elastic range. Large deformation evolution equations for the distortional deformations in the elastic and in the dissipative component are presented. A robust, strongly objective numerical integration algorithm is used to model rate-dependent and rate-independent inelastic responses. The constitutive formulation is specialized to simulate the experimental data. The nonlinear viscoelastic model accurately represents the time-dependent passive response of skeletal muscle. [ABSTRACT FROM AUTHOR]

Direct Simulation Monte Carlo (DSMC) is a powerful numerical method to study rarefied gas flows such as cometary comae and has been used by several authors over the past decade to study cometary outflow. However, the investigation of the parameter space in simulations can be time consuming since 3D DSMC is computationally highly intensive. For the target of ESA's Rosetta mission, comet 67P/Churyumov-Gerasimenko, we have identified to what extent modification of several parameters influence the 3D flow and gas temperature fields and have attempted to establish the reliability of inferences about the initial conditions from in situ and remote sensing measurements. A large number of DSMC runs have been completed with varying input parameters. In this work, we present the simulation results and conclude on the sensitivity of solutions to certain inputs. It is found that among cases of water outgassing, the surface production rate distribution is the most influential variable to the flow field. [ABSTRACT FROM AUTHOR]

Periodic comets move around the Sun on elliptical orbits. As such comet 67P/Churyumov-Gerasimenko (hereafter 67P) spends a portion of time in the inner solar system where it is exposed to increased solar insolation. Therefore given the change in heliocentric distance, in case of 67P from aphelion at 5.68 AU to perihelion at ~1.24 AU, the comet's activity-the production of neutral gas and dust-undergoes significant variations. As a consequence, during the inbound portion, the mass loading of the solar wind increases and extends to larger spatial scales. This paper investigates how this interaction changes the character of the plasma environment of the comet by means of multifluid MHD simulations. The multifluid MHD model is capable of separating the dynamics of the solar wind ions and the pick-up ions created through photoionization and electron impact ionization in the coma of the comet. We show how two of the major boundaries, the bow shock and the diamagnetic cavity, form and develop as the comet moves through the inner solar system. Likewise for 67P, although most likely shifted back in time with respect to perihelion passage, this process is reversed on the outbound portion of the orbit. The presented model herein is able to reproduce some of the key features previously only accessible to particle-based models that take full account of the ions' gyration. The results shown herein are in decent agreement to these hybrid-type kinetic simulations. [ABSTRACT FROM AUTHOR]

A new approach to 1,3-diazapyrenes via peri annelation of perimidines with 1,3-dicarbonyl compounds is developed. It is demonstrated that this method has a number of advantages compared to a previously reported procedure employing chalcones as electrophilic components. The new method can be used for efficient double peri annelation of biperimidines with 1,3-dicarbonyl compounds affording 2,2′-bi-1,3-diazapyrenes. [ABSTRACT FROM AUTHOR]

A letter to the editor about N-phenyl-1,5,7-triazacyclopenta[ cd]-phenalenes is presented.

The androgen receptor (AR) is a transcription factor that employs many diverse interactions with coregulatory proteins in normal physiology and in prostate cancer (PCa). The AR mediates cellular responses in association with chromatin complexes and kinase cascades. Here we report that the nuclear matrix protein, scaffold attachment factor B1 (SAFB1), regulates AR activity and AR levels in a manner that suggests its involvement in PCa. SAFB1 mRNA expression was lower in PCa in comparison with normal prostate tissue in a majority of publicly available RNA expression data sets. SAFB1 protein levels were also reduced with disease progression in a cohort of human PCa that included metastatic tumors. SAFB1 bound to AR and was phosphorylated by the MST1 (Hippo homolog) serine-threonine kinase, previously shown to be an AR repressor, and MST1 localization to AR-dependent promoters was inhibited by SAFB1 depletion. Knockdown of SAFB1 in androgen-dependent LNCaP PCa cells increased AR and prostate-specific antigen (PSA) levels, stimulated growth of cultured cells and subcutaneous xenografts and promoted a more aggressive phenotype, consistent with a repressive AR regulatory function. SAFB1 formed a complex with the histone methyltransferase EZH2 at AR-interacting chromatin sites in association with other polycomb repressive complex 2 (PRC2) proteins. We conclude that SAFB1 acts as a novel AR co-regulator at gene loci where signals from the MST1/Hippo and EZH2 pathways converge. [ABSTRACT FROM AUTHOR]

The industrial copper-zinc catalyst MEGAMAX®-phase synthesis of methanol was tested under the conditions of a liquid-phase process while varying the pressure (0.5-7.0 MPa) and the gas mixture flow rate (40-400 mL/min). The catalyst was shown to have high activity and selectivity in the synthesis of methanol. The best result (730 g(methanol)/kg(cat) h and selectivity 99.2%) was obtained under reaction conditions of 2.0 MPa, 240°C, H: CO: CO: N = 70.5: 17.9: 6.5: 5.1, and reaction time 3 h. The concentration of methane by-product increased at gas mixture pressures over 3.0 MPa, lowering the selectivity of the process with respect to methanol. Trace amounts of ethane and water were found in addition to methane. Dimethyl ether, a typical by-product of methanol synthesis, was missing from the vapor-gas mixture over the range of pressures. The results from this study indicate that the MEGAMAX® can be used in the liquid-phase synthesis of methanol. [ABSTRACT FROM AUTHOR]

Large deformation evolution equations for elastic distortional deformation and isotropic hardening/softening have been developed that model a smooth elastic-inelastic transition for both rate-independent and rate-dependent response with no need for loading-unloading conditions. A novel special case is a rate-independent overstress model. Specific simplified constitutive equations are proposed that capture the main effects of elastic-plastic and elastic-viscoplastic materials with only a few material parameters. Moreover, a robust and strongly objective numerical integrator for these simplified evolution equations has been developed which needs no iteration. Examples show the influence of the various parameters on the predicted material response. The smoothness of the elastic-inelastic transition in the proposed model, with the associated overstress, tends to spread the inelastic region. This side effect prevents severe deformation from being localized in an element region that continues to reduce in size with mesh refinement. However, preliminary calculations indicate the need for additional modeling of a material characteristic length that independently controls the size of a localized severely deformed region. [ABSTRACT FROM AUTHOR]