19 research outputs found
Evaluation of the accuracy of an impact load cell using lumped parameter modeling and analysis
The objective of the current study is to evaluate the fidelity of load cell reading during impact testing in a drop-weight impactor using lumped parameter modeling. For the most common configuration of a moving impactor-load cell system in which dynamic load is transferred from the impactor head to the load cell, a quantitative assessment is made of the possible discrepancy that can result in load cell response. A 3-DOF (degrees-of-freedom) LPM (lumped parameter model) is considered to represent a given impact testing set-up. In this model, a test specimen in the form of a steel hat section similar to front rails of cars is
represented by a nonlinear spring while the load cell is assumed to behave in a linear manner due to its high
stiffness. Assuming a given load-displacement response obtained in an actual test as the true behavior of the
specimen, the numerical solution of the governing differential equations following an implicit time integration scheme is shown to yield an excellent reproduction of the mechanical behavior of the specimen
thereby confirming the accuracy of the numerical approach. The spring representing the load cell, however,predicts a response that qualitatively matches the assumed load-displacement response of the test specimen with a perceptibly lower magnitude of load
Data in support of the negative influence of divalent cations on (−)-epigallocatechin-3-gallate (EGCG)-mediated inhibition of matrix metalloproteinase-2 (MMP-2)
In this data article we have provided evidence for the negative influence of divalent cations on (−)‐epigallocatechin-3-gallate (EGCG)-mediated inhibition of matrix metalloproteinase-2 (MMP-2) activity in cell-free experiments. Chelating agents, such as EDTA and sodium citrate alone, did not affect MMP-2 activity. While EDTA enhanced, excess of divalent cations interfered with EGCG-mediated inhibition of MMP-2
Evaluation of the accuracy of an accelerometer response generated by axial impact loading
The basic objective in the present study is to show that for the most common configuration of an impactor system, an accelerometer cannot exactly reproduce the dynamic response of a specimen subject to impact loading. Assessment of the accelerometer mounted in a drop-weight impactor setup for an axially loaded specimen is done with the aid of an equivalent lumped parameter model (LPM) of the setup. A steel hat-type specimen under the impact loading is represented as a non-linear spring of varying stiffness, while the accelerometer is assumed to behave in a linear manner due to its high stiffness. A suitable numerical approach has been used to solve the non-linear governing equations for a 3 degrees-of-freedom system in a piece-wise linear manner. The numerical solution following an explicit time integration scheme is used to yield an excellent reproduction of the mechanical behavior of the specimen thereby confirming the accuracy of the numerical approach. The spring representing the accelerometer, however, predicts a response that qualitatively matches the assumed load–displacement response of the test specimen with a perceptibly lower magnitude of load
Epigallocatechin gallate induces the steady state mRNA levels of pS2 and PR genes in MCF-7 breast cancer cells
312-316Investigations using <i style="mso-bidi-font-style:
normal">in vitro and in vivo
models of breast carcinogenesis have demonstrated anti-neoplastic activity of
the green tea polyphenol, epigallocatechin gallate (EGCG). Although a number of
molecular targets of EGCG have been identified, its impact on the expression of
estrogen target genes is not completely understood. Here, we examined the mRNA
expression levels of two estrogen target genes, namely Trefoil Factor 1 (pS2)
and Progesterone Receptor (PR) in MCF-7 cells treated with EGCG. We observed
that treatment with 40 µM EGCG, which caused only 20% decrease in cell
viability, resulted in increased steady state expression levels of pS2 and PR
mRNA. This suggests that EGCG may exert its biological activities, at least in
part, by influencing the expression of estrogen target genes
Expression profiling of genes modulated by estrogen, EGCG or both in MCF-7 breast cancer cells
(−)-Epigallocatechin-3-gallate (EGCG) is one of the most potent and the most studied green tea catechin. Reports on mechanisms of EGCG action and its cellular targets are plenty. Compelling evidences in the literature in favor of ER being one of its targets suggest that EGCG may have a significant impact on estrogen regulated gene expression. Despite the possible implications on breast cancer chemoprevention or therapy, this aspect of EGCG action has not been adequately investigated. In order to address this issue, we have obtained gene expression profiles of MCF-7 breast cancer cells treated with ethanol (vehicle control) and those treated with estrogen, EGCG or both, using microarrays. Here, we have presented in detail the design and execution of the microarray experiment, quality control checks and analysis of microarray data. The utility and importance of the data generated in this work have been discussed in the context of the background literature. Our data is available in the Gene Expression Omnibus (GEO) database with the identifier GSE56245