Formulation of continuous/discontinuous Galerkin methods for strain gradient-dependent damage

Continuum damage models are widely used to represent the development of microscopic defects that coalesce into a macroscopic crack. The microscopic defects cause a progressive weakening or softening of the material (damage). Strain gradient-dependent terms have been included in some damage theories to regularize them, and thereby avoid a pathological mesh-dependence in the solution. A strain gradient-dependent damage model is considered here for the simulation of this feature in quasi-brittle materials. In the model considered, the damage parameter depends upon a regularized equivalent strain. The regularization is introduced through a dependency on the Laplacian of an equivalent strain measure. The introduction of the Laplacian of the strain leads to numerical difficulties as the governing differential equations are fourth-order, and additional boundary conditions must be specified. The application of such a model in a standard finite element framework requires $C^1$ continuity of the shape functions. Here, a continuous/discontinuous mixed Galerkin method is presented which avoids the need for high-order continuity. The formulation allows the use of $C^0$ or $C^{-1}$ interpolations for the regularized strain field and a $C^0$ interpolation of the displacement field. Numerical examples are presented to validate the formulation in one and two dimensions. Several interpolations are tested extensively in one dimension in order to provide guidance for the most appropriate formulations in two dimensions. The formulation is applied to crack propagation in a three-point bending test, with the computed result being independent of the discretization

A continuous/discontinuous Galerkin formulation for a strain gradient-dependent damage model: 2D results

The numerical solution of strain gradient-dependent continuum problems has been hindered by continuity demands on the basis functions. The presence of terms in constitutive models which involve gradients of the strain eld means that the $C^0$ continuity of standard nite element shape functions is insu cient. In this work, a continuous/discontinuous Galerkin formulation is developed to solve a strain gradient-dependent damage problem in a rigorous manner. Potential discontinuities in the strain field across element boundaries are incorporated in the weak form of the governing equations. The performance of the formulation is tested in one dimension for various interpolations, which provides guidance for two-dimensional simulations

Control of stochastic and induced switching in biophysical networks

Noise caused by fluctuations at the molecular level is a fundamental part of intracellular processes. While the response of biological systems to noise has been studied extensively, there has been limited understanding of how to exploit it to induce a desired cell state. Here we present a scalable, quantitative method based on the Freidlin-Wentzell action to predict and control noise-induced switching between different states in genetic networks that, conveniently, can also control transitions between stable states in the absence of noise. We apply this methodology to models of cell differentiation and show how predicted manipulations of tunable factors can induce lineage changes, and further utilize it to identify new candidate strategies for cancer therapy in a cell death pathway model. This framework offers a systems approach to identifying the key factors for rationally manipulating biophysical dynamics, and should also find use in controlling other classes of noisy complex networks.Comment: A ready-to-use code package implementing the method described here is available from the authors upon reques

Photon signature analysis using template matching

We describe an approach to detect improvised explosive devices (IEDs) by using a template matching procedure. This approach relies on the signature due to backstreaming ? photons from various targets. In this work we have simulated cylindrical targets of aluminum, iron, copper, water and ammonium nitrate (nitrogen-rich fertilizer). We simulate 3.5 MeV source photons distributed on a plane inside a shielded area using Monte Carlo N-Particle (MCNP TM) code version 5 (V5). The 3.5 MeV source gamma rays yield 511 keV peaks due to pair production and scattered gamma rays. In this work, we simulate capture of those photons that backstream, after impinging on the target element, toward a NaI detector. The captured backstreamed photons are expected to produce a unique spectrum that will become part of a simple signal processing recognition system based on the template matching method. Different elements were simulated using different sets of random numbers in the Monte Carlo simulation. To date, the sum of absolute differences (SAD) method has been used to match the template. In the examples investigated, template matching was found to detect all elements correctly

Epidermal growth factor (EGF)-like repeats of human tenascin-C as ligands for EGF receptor.

Signaling through growth factor receptors controls such diverse cell functions as proliferation, migration, and differentiation. A critical question has been how the activation of these receptors is regulated. Most, if not all, of the known ligands for these receptors are soluble factors. However, as matrix components are highly tissue-specific and change during development and pathology, it has been suggested that select growth factor receptors might be stimulated by binding to matrix components. Herein, we describe a new class of ligand for the epidermal growth factor (EGF) receptor (EGFR) found within the EGF-like repeats of tenascin-C, an antiadhesive matrix component present during organogenesis, development, and wound repair. Select EGF-like repeats of tenascin-C elicited mitogenesis and EGFR autophosphorylation in an EGFR-dependent manner. Micromolar concentrations of EGF-like repeats induced EGFR autophosphorylation and activated extracellular signal-regulated, mitogen-activated protein kinase to levels comparable to those induced by subsaturating levels of known EGFR ligands. EGFR-dependent adhesion was noted when the ligands were tethered to inert beads, simulating the physiologically relevant presentation of tenascin-C as hexabrachion, and suggesting an increase in avidity similar to that seen for integrin ligands upon surface binding. Specific binding to EGFR was further established by immunofluorescence detection of EGF-like repeats bound to cells and cross-linking of EGFR with the repeats. Both of these interactions were abolished upon competition by EGF and enhanced by dimerization of the EGF-like repeat. Such low affinity behavior would be expected for a matrix-tethered ligand; i.e., a ligand which acts from the matrix, presented continuously to cell surface EGF receptors, because it can neither diffuse away nor be internalized and degraded. These data identify a new class of insoluble growth factor ligands and a novel mode of activation for growth factor receptors

A study of possible sea state information in the sample and hold gate statistics for the GEOS-3 satellite altimeter

The statistical variations in the sample gate outputs of the GEOS-3 satellite altimeter were studied for possible sea state information. After examination of a large number of statistical characteristics of the altimeter waveforms, it was found that the best sea predictor for H-1/3 in the range of 0 to 3 meters was the 75th percentile of sample and hold gate number 11

Assessment of bias in police lineups.

Materials from five extant field studies were analyzed to determine the level of structural bias in police lineups. Depending on the jurisdiction, between 33% and 68% of lineups sampled from 1,548 real police lineups scored as suspect-biased using mock-witness proportion score. The suspect did not draw a fair portion of mock-witness picks in 20% of field lineups (reverse-biased lineups). Lineup fairness measures revealed that a point estimate (mean) for a set of lineups can mask significant problems in lineup construction and that any single lineup should not be assumed to be fair based on an aggregate score. A sample of 190 lineups from the field data of Wells, Steblay, and Dysart (2015) was used to conduct four new studies that examined the relationship between lineup structure and real eyewitness decisions. Our primary hypothesis—that real eyewitness decisions could be predicted by lineup bias measures—was partially supported. Suspect identifications from simultaneous (but not sequential) lineups were disproportionately linked to suspect-biased lineups. Suspect identifications from suspect-biased lineups were almost twice as frequent for simultaneous than for sequential lineups. Additional experimental tests of these field lineups using mock-witness measures demonstrated that detailed descriptions produced higher lineup bias scores than did brief descriptions, indicating that brief descriptions can hide substantial lineup bias. Mock-witnesses were able to find the suspect in some lineups via cues not readily apparent in the description alone. The data support the idea of using a framework of descriptors to improve the fairness of lineups. Study outcomes demonstrate the realities and nuances of field lineup structure that necessitate updated consideration of the use of mock-witness measures and a blended approach to lineup construction. (PsycInfo Database Record (c) 2020 APA, all rights reserved

Alfalfa Response to Varying Rates of Phosphorus and Potassium Fertilization on Deep, Red, Limestone - Derived Soils of the Pennyroyal Area In Kentucky

The Western Pennyroyal area of Kentucky consists largely of deep, well-drained limestone-derived soils occurring on an undulating to rolling landscape. A thin loess mantle overlies the limestone residuum in many areas. Soils on these landscapes are capable of good crop production, providing the basis of the rather intensive grain-hay- tobacco-livestock farming systems common to the Pennyroyal area. Because of the well-suited physical characteristics of these soils, alfalfa is a very important hay crop to this area

Factors Affecting Color of Cured Burley Leaf

Much interest has been shown by tobacco growers during recent months in fertilization and or other management practices that can be used to produce darker and redder cured leaf of burley tobacco. The purpose of this newsletter is to summarize what we know about some of the factors which affect color of cured leaf