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The skin is the largest organ in the human body and serves various functions, including mechanical protection and mechanosensation. Yet, even though skin's biomechanics are attributed to two main layers—epidermis and dermis—computational models have often treated this tissue as a thin homogeneous material or, when considering multiple layers, have ignored the most prominent heterogeneities of skin seen at the mesoscale. Here, we create finite element models of representative volume elements (RVEs) of skin, including the three-dimensional variation of the interface between the epidermis and dermis as well as considering the presence of hair follicles. The sinusoidal interface, which approximates the anatomical features known as Rete ridges, does not affect the homogenized mechanical response of the RVE but contributes to stress concentration, particularly at the valleys of the Rete ridges. The stress profile is three-dimensional due to the skin's anisotropy, leading to high-stress bands connecting the valleys of the Rete ridges through one type of saddle point. The peaks of the Rete ridges and the other class of saddle points of the sinusoidal surface form a second set of low-stress bands under equi-biaxial loading. Another prominent feature of the heterogeneous stress pattern is a switch in the stress jump across the interface, which becomes lower with respect to the flat interface at increasing deformations. These features are seen in both tension and shear loading. The RVE with the hair follicle showed strains concentrating at the epidermis adjacent to the hair follicle, the epithelial tissue surrounding the hair right below the epidermis, and the bulb or base region of the hair follicle. The regions of strain concentration near the hair follicle in equi-biaxial and shear loading align with the presence of distinct mechanoreceptors in the skin, except for the bulb or base region. This study highlights the importance of skin heterogeneities, particularly its potential mechanophysiological role in the sense of touch and the prevention of skin delamination. [ABSTRACT FROM AUTHOR]

This work presents for the first time an integrated hydrogen generation system with storage based on aluminum waste from soda cans to supply hydrogen on-demand to a PEM (proton exchange membrane)-type fuel cell for reliable electricity generation. The raw material that feeds the hydrogen generator consists of distilled water, aluminum from soda cans and sodium hydroxide to remove the oxide layer that passivates the aluminum, a technique known as alkaline activation. The design of the generator was done based on the analysis of the mass and energy balance and its experimental verification. The stainless-steel prototype consisted of a vessel with a capacity of 2.1 L batch reactor, which delivers the gas produced to a column of water to scrub the gas. The three components function as a temporary gas storage system while the fuel is delivered at a regulated pressure. The NaOH container has a maximum storage capacity of 0.45 L, enough for 21 g of aluminum to react and produce 25.7 L (at 0 °C and 105 Pa) of hydrogen; the reaction yield in the generator was 97%. Through the evaluation of the electrical performance at a home-made 9 cm2 PEMFC and extrapolation to 45 W, it was calculated that the generator can supply H2 to the cell for 53 min at that power. [ABSTRACT FROM AUTHOR]

The analysis of tissue mechanics in biomedical applications demands nonlinear constitutive models able to capture the energy dissipation mechanisms, such as damage, that occur during tissue deformation. Furthermore, implementation of sophisticated material models in finite element models is essential to improve medical devices and diagnostic tools. Building on previous work toward microstructure-driven models of collagenous tissue, here we show a constitutive model based on fiber orientation and waviness distributions for skin that captures not only the anisotropic strain-stiffening response of this and other collagen-based tissues, but, additionally, accounts for tissue damage directly as a function of changes in the microstructure, in particular changes in the fiber waviness distribution. The implementation of this nonlinear constitutive model as a user subroutine in the popular finite element package Abaqus enables large-scale finite element simulations for biomedical applications. We showcase the performance of the model in fracture simulations during pure shear tests, as well as simulations of needle insertion into skin relevant to auto-injector design. [ABSTRACT FROM AUTHOR]

We consider a one-dimensional continuum Anderson model where the potential decays in average like | x | - α , α > 0 . We show dynamical localization for 0 < α < 1 2 and provide control on the decay of the eigenfunctions. [ABSTRACT FROM AUTHOR]

We study the spectrum and dynamics of a one-dimensional discrete Dirac operator in a random potential obtained by damping an i.i.d. environment with an envelope of type n−α for α > 0. We recover all the spectral regimes previously obtained for the analogue Anderson model in a random decaying potential, namely: absolutely continuous spectrum in the super-critical region α > 1 2 ; a transition from pure point to singular continuous spectrum in the critical region α = 1 2 ; and pure point spectrum in the sub-critical region α < 1 2 . From the dynamical point of view, delocalization in the super-critical region follows from the RAGE theorem. In the critical region, we exhibit a simple argument based on lower bounds on eigenfunctions showing that no dynamical localization can occur even in the presence of point spectrum. Finally, we show dynamical localization in the sub-critical region by means of the fractional moments method and provide control on the eigenfunctions. [ABSTRACT FROM AUTHOR]

Olfactory ensheathing cells (OECs) are a type of glia from the mammalian olfactory system, with neuroprotective and regenerative properties. β-Amyloid peptides are a major component of the senile plaques characteristic of the Alzheimer brain. The amyloid beta (Aβ) precursor protein is cleaved to amyloid peptides, and Aβ is regarded to be the functional domain of Aβ, responsible for its neurotoxic properties. It has been reported that Aβ triggers reactive oxygen species (ROS)-mediated oxidative damage, altering the structure and function of mitochondria, leading to the activation of the mitochondrial intrinsic apoptotic pathway. Our goal is to investigate the effects of OECs on the toxicity of aggregated Aβ, in human neuroblastoma SH-SY5Y cells. For such purpose, SH-SY5Y cells were incubated with Aβ and OEC-conditioned medium (OECCM). OECCM promoted the cell viability and reduced the apoptosis, and decreased the intracellular ROS and the lipid peroxidation. In the presence of OECCM, mRNA and protein levels of antioxidant enzymes (SOD1 and SOD2) were upregulated. Concomitantly, OECCM decreased mRNA and the protein expression levels of cytochrome c, caspase-9, caspase-3, and Bax in SH-SY5Y cells, and increased mRNA and the protein expression level of Bcl-2. However, OECCM did not alter intracellular Ca concentration in SH-SY5Y cells. Taken together, our data suggest that OECCM ameliorates Aβ-induced oxidative damage in neuroblastoma SH-SY5Y cells by inhibiting the mitochondrial intrinsic pathway. These data provide new insights into the functional actions of OECCM on oxidative stress-induced cell damage. [ABSTRACT FROM AUTHOR]

Olfactory ensheathing cell (OEC) transplantation emerged some years ago as a promising therapeutic strategy to repair injured spinal cord. However, inhibitory molecules are present for long periods of time in lesioned spinal cord, inhibiting both OEC migration and axonal regrowth. Two families of these molecules, chondroitin sulphate proteoglycans (CSPG) and myelin-derived inhibitors (MAIs), are able to trigger inhibitory responses in lesioned axons. Mounting evidence suggests that OEC migration is inhibited by myelin. Here we demonstrate that OEC migration is largely inhibited by CSPGs and that inhibition can be overcome by the bacterial enzyme Chondroitinase ABC. In parallel, we have generated a stable OEC cell line overexpressing the Nogo receptor (NgR) ectodomain to reduce MAI-associated inhibition in vitro and in vivo. Results indicate that engineered cells migrate longer distances than unmodified OECs over myelin or oligodendrocyte-myelin glycoprotein (OMgp)-coated substrates. In addition, they also show improved migration in lesioned spinal cord. Our results provide new insights toward the improvement of the mechanisms of action and optimization of OEC-based cell therapy for spinal cord lesion. [ABSTRACT FROM AUTHOR]

We give an explicit formula for the joint density of the max and argmax of the Airy process minus a parabola. The argmax has a universal distribution which governs the rescaled endpoint for large time or temperature of directed polymers in 1+1 dimensions. [ABSTRACT FROM AUTHOR]

We study the scaling limit of the spectrum of the β-Jacobi ensemble at the soft edge and hard edge for general values of β. We show that the limiting point processes correspond respectively to the stochastic Airy and Bessel point processes introduced in Ramírez et al. (J. Am. Math. Soc. 24(4):919-944, ) and Ramírez and Rider (Commun. Math. Phys. 288(3):887-906, ). [ABSTRACT FROM AUTHOR]

Newly generated olfactory receptor axons grow from the peripheral to the central nervous system aided by olfactory ensheathing cells (OECs). Thus, OEC transplantation has emerged as a promising therapy for spinal cord injuries and for other neural diseases. However, these cells do not present a uniform population, but instead a functionally heterogeneous population that exhibits a variety of responses including adhesion, repulsion, and crossover during cell-cell and cell-matrix interactions. Some studies report that the migratory properties of OECs are compromised by inhibitory molecules and potentiated by chemical gradients. Here, we demonstrated that rodent OECs express all the components of the Nogo receptor complex and that their migration is blocked by myelin. Next, we used cell tracking and traction force microscopy to analyze OEC migration and its mechanical properties over myelin. Our data relate the decrease of traction force of OEC with lower migratory capacity over myelin, which correlates with changes in the F-actin cytoskeleton and focal adhesion distribution. Lastly, OEC traction force and migratory capacity is enhanced after cell incubation with the Nogo receptor inhibitor NEP1-40. [ABSTRACT FROM AUTHOR]

We report a case of radial metaphyseal osteochondroma secondary to osteomyelitis in a premature baby of 28 weeks. This is the second case with these characteristics that has been described in the literature. A possible pathogenesis is related to trauma during drainage of the abscess or following the associated inflammatory process. [ABSTRACT FROM AUTHOR]