Viscoplasticity and large-scale chain relaxation in glassy-polymeric strain hardening

A simple theory for glassy polymeric mechanical response which accounts for large scale chain relaxation is presented. It captures the crossover from perfect-plastic response to strong strain hardening as the degree of polymerization $N$ increases, without invoking entanglements. By relating hardening to interactions on the scale of monomers and chain segments, we correctly predict its magnitude. Strain activated relaxation arising from the need to maintain constant chain contour length reduces the $N$ dependence of the characteristic relaxation time by a factor $\sim \dot\epsilon N$ during active deformation at strain rate $\dot\epsilon$. This prediction is consistent with results from recent experiments and simulations, and we suggest how it may be further tested experimentally.Comment: The theoretical treatment of the mechanical response has been significantly revised, and the arguments for coherent relaxation during active deformation made more transparen

Five Facets of Mindfulness and Psychological Health: Evaluating a Psychological Model of the Mechanisms of Mindfulness

There has been an increasing focus on determining the psychological mechanisms underlying the broad effects of mindfulness on psychological health. Mindfulness has been posited to be related to the construct of reperceiving or decentering, defined as a shift in perspective associated with decreased attachment to one\u27s thoughts and emotions. Decentering is proposed to be a meta-mechanism that mobilizes four psychological mechanisms (cognitive flexibility, values clarification, self-regulation, and exposure), which in turn are associated with positive health outcomes. Despite preliminary support for this model, extant studies testing this model have not examined distinct facets of mindfulness. The present study used a multidimensional measure of mindfulness to examine whether this model could account for the associations between five facets of mindfulness and psychological symptoms (depressive symptoms, stress, anxiety symptoms, alcohol-related problems) in a sample of college students (N = 944). Our findings partially support this model. We found significant double-mediated associations in the expected directions for all outcomes (stress, anxiety symptoms, and depressive symptoms) except alcohol-related problems, and for each of the facets of mindfulness except observing. However, decentering and the specific mechanisms did not fully mediate the associations among mindfulness facets and psychological health outcomes. Experimental and ecological momentary assessment designs are needed to understand the psychological processes that account for the beneficial effects of mindfulness

Land Development - Tree 4 Hope

The Land Development Team has partnered with Tree 4 Hope and Hope Academy in Santa Lucía Milpas Altas, Guatemala to improve the outdoor facilities of the school. Jenn and David Hope-Tringali are the client/partner representatives of the school for this project. The goal of the project is to provide design and construction drawings for three main elements of the proposed land development: (1) a parking lot for buses and school vehicles that enter the site, (2) a single sports court that can accommodate basketball and soccer, and (3) a playground that is directed towards themes associated with STEAM (science, technology, engineering, art, and math). The team has completed project drawings to allow construction by local personnel, or by student or church mission teams when travel is allowed to resume post-pandemic.https://mosaic.messiah.edu/engr2021/1007/thumbnail.jp

CFTR gene variant for patients with congenital absence of vas deferens [3]

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New Extracellular Resistance Mechanism for Cisplatin

The HSQC NMR spectrum of 15N-cisplatin in cell growth media shows resonances corresponding to the monocarbonato complex, cis-[Pt(NH3)2(CO3)Cl]-, 4, and the dicarbonato complex, cis-[Pt(NH3)2(CO3)2]-2, 5, in addition to cisplatin itself, cis-[Pt(NH3)2Cl2], 1. The presence of Jurkat cells reduces the amount of detectable carbonato species by (2.8 ± 0.7) fmol per cell and has little effect on species 1. Jurkat cells made resistant to cisplatin reduce the amount of detectable carbonato species by (7.9 ± 5.6) fmol per cell and also reduce the amount of 1 by (3.4 ± 0.9) fmol per cell. The amount of detectable carbonato species is also reduced by addition of the drug to medium that has previously been in contact with normal Jurkat cells (cells removed); the reduction is greater when drug is added to medium previously in contact with resistant Jurkat cells (cells removed). This shows that the platinum species are modified by a cell-produced substance that is released to the medium. Since the modified species have been shown not to enter or bind to cells, and since resistant cells modify more than non-resistant cells, the modification constitutes a new extracellular mechanism for cisplatin resistance which merits further attention

Polar motion and UT1: Comparison of VLBI, lunar laser, satellite laser, satellite Doppler, and conventional astrometric determinations

Very long baseline interferometry observations made with a 3900 km baseline interferometer (Haystack Observatory in Massachusetts to Owens Valley Observation in California) were used to estimate changes in the X-component of the position of the Earth's pole and in UT1. These estimates are compared with corresponding ones from lunar laser ranging, satellite laser ranging, satellite Doppler, and stellar observations

Elasticity Theory Connection Rules for Epitaxial Interfaces

Elasticity theory provides an accurate description of the long-wavelength vibrational dynamics of homogeneous crystalline solids, and with supplemental boundary conditions on the displacement field can also be applied to abrupt heterojunctions and interfaces. The conventional interface boundary conditions, or connection rules, require that the displacement field and its associated stress field be continuous through the interface. We argue, however, that these boundary conditions are generally incorrect for epitaxial interfaces, and we give the general procedure for deriving the correct conditions, which depend essentially on the detailed microscopic structure of the interface. As a simple application of our theory we analyze in detail a one-dimensional model of an inhomogeneous crystal, a chain of harmonic oscillators with an abrupt change in mass and spring stiffness parameters. Our results have implications for phonon dynamics in nanostructures such as superlattices and nanoparticles, as well as for the thermal boundary resistance at epitaxial interfaces.Comment: 7 pages, Revte

FixFit: using parameter-compression to solve the inverse problem in overdetermined models

All fields of science depend on mathematical models. One of the fundamental problems with using complex nonlinear models is that data-driven parameter estimation often fails because interactions between model parameters lead to multiple parameter sets fitting the data equally well. Here, we develop a new method to address this problem, FixFit, which compresses a given mathematical model's parameters into a latent representation unique to model outputs. We acquire this representation by training a neural network with a bottleneck layer on data pairs of model parameters and model outputs. The bottleneck layer nodes correspond to the unique latent parameters, and their dimensionality indicates the information content of the model. The trained neural network can be split at the bottleneck layer into an encoder to characterize the redundancies and a decoder to uniquely infer latent parameters from measurements. We demonstrate FixFit in two use cases drawn from classical physics and neuroscience