Numerical derivative analysis of load-displacement curves in depth-sensing indentation

Materials Research Society Symposium Proceedings, 791: pp. 191-202. Retrieved September 19, 2006 from http://nano.materials.drexel.edu/Papers/NumericalDerivativeAnal.pdf.We have investigated strain fields around GaN nanoindentations. Stress relaxation around the edges of the nanoindentation was evident in atomic force microscopy images. More detailed information on the strain fields was obtained from Raman scattering, which has been used to analyze the shape of the strain field around the indentation. We find that the Berkovich tip giving a triangular imprint on the sample generates a strain field, which represents a hexagonal pattern. Negative values of the strain indicate that the residual stress is compressive. Strain is larger in the center of the indentation than outside. Analysis of the ratio of the frequency shift of the E2 and A1sLOd modes suggests that the residual strains are close to biaxial state outside the indentation contact zone, and mostly hydrostatic within the indentation center

Making the Connection Between Microstructure and Mechanics

The purpose of microstructural control is to optimize materials properties. To that end, they have developed sophisticated and successful computational models of both microstructural evolution and mechanical response. However, coupling these models to quantitatively predict the properties of a given microstructure poses a challenge. This problem arises because most continuum response models, such as finite element, finite volume, or material point methods, do not incorporate a real length scale. Thus, two self-similar polycrystals have identical mechanical properties regardless of grain size, in conflict with theory and observations. In this project, they took a tiered risk approach to incorporate microstructure and its resultant length scales in mechanical response simulations. Techniques considered include low-risk, low-benefit methods, as well as higher-payoff, higher-risk methods. Methods studied include a constitutive response model with a local length-scale parameter, a power-law hardening rate gradient near grain boundaries, a local Voce hardening law, and strain-gradient polycrystal plasticity. These techniques were validated on a variety of systems for which theoretical analyses and/or experimental data exist. The results may be used to generate improved constitutive models that explicitly depend upon microstructure and to provide insight into microstructural deformation and failure processes. Furthermore, because mechanical state drives microstructural evolution, a strain-enhanced grain growth model was coupled with the mechanical response simulations. The coupled model predicts both properties as a function of microstructure and microstructural development as a function of processing conditions

The number of directional changes alters the physiological, perceptual and neuromuscular responses of netball players during intermittent shuttle running

This is a non-final version of an article published in final form in Journal of Strength and Conditioning Research, Vol 29, issue 10, October 2015.This study investigated whether an increased number of changes in direction altered the metabolic, cardiovascular, perceptual and neuromuscular responses to intermittent shuttle running. Using a randomized crossover design, ten female netball players completed 30 min of intermittent shuttle running over a 10 m (ISR10) and 20 m (ISR20) linear course. Measures of expired air, heart rate (HR), RPE, blood lactate concentration ([BLa]) and peak torque of knee extensors and flexors were measured. Differences (% ± 90% CL) in VO2 (1.5 ± 5.6%) was unclear between conditions, while HR was possibly higher (1.5 ± 2.5%) and [BLa] very likely lower in ISR20 compared to ISR10 (-32.7 ± 9.9%). RPE was likely lower in the ISR20 compared to the ISR10 condition at 15 (-5.0 ± 5.0%) and mosly likely lower at 30 min (-9.4 ± 2.0%). Sprint times over 20 m were likely slower during ISR20 at mid (3.9 ± 3.2%) but unclear post (2.1 ± 5.4%). Changes in muscle function were not different between ISR10 and ISR20 conditions for knee extension (-0.2 ± 0.9%) but were likely different for knee flexion (-5.7 ± 4.9%). More directional changes during shuttle running increases the physiological and perceptual load on female athletes that also causes a greater reductions in knee extensor torque. These findings have implications for the effective conditioning and injury prevention of female team sport athletes

Title page Glucuronide production by whole-cell biotransformation using genetically engineered fission yeast S. pombe

Abstract Drug metabolites generated by UDP glycosyltransferases (UGTs) are needed for drug development and toxicity studies, especially in the context of safety testing of metabolites during drug development. Since chemical metabolite synthesis can be arduous, various biological approaches have been developed; however, no whole-cell biotransformation with recombinant microbes that express human UGTs was yet achieved. In this study we expressed human UDP glucose-6-dehydrogenase (UGDH) together with several human or rat UGT isoforms in the fission yeast Schizosaccharomyces pombe and generated strains that catalyze the whole-cell glucuronidation of standard substrates. Moreover, we established two methods to obtain stable isotope-labeled glucuronide metabolites: The first uses a labeled aglycon, while the second employs 13 C 6 -glucose as a metabolic precursor of isotope-labeled UDPglucuronic acid (UDP-GA) and yields a sixfold labeled glucuronide. The system described here should lead to a significant facilitation in the production of both labeled and unlabeled drug glucuronides for industry and academia. DMD 30965

Investigation of the effects of intense pulsed particle beams on the durability of metal-to-plastic interfaces.

We have investigated the potential for intense particle beam surface modification to improve the mechanical properties of materials commonly used in the human body for contact surfaces in, for example, hip and knee implants. The materials studied include Ultra-High Molecular Weight Polyethylene (UHMWPE), Ti-6Al-4Al (titanium alloy), and Co-Cr-Mo alloy. Samples in flat form were exposed to both ion and electron beams (UHMWPE), and to ion beam treatment (metals). Post-analysis indicated a degradation in bulk properties of the UHMWPE, except in the case of the lightest ion fluence tested. A surface-alloyed Hf/Ti layer on the Ti-6Al-4V is found to improve surface wear durability, and have favorable biocompatibility. A promising nanolaminate ceramic coating is applied to the Co-Cr-Mo to improve surface hardness

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field

<title>Strength of polysilicon for MEMS devices</title>

The safe, secure and reliable application of Microelectromechanical Systems (MEMS) devices requires knowledge about the distribution in material and mechanical properties of the small-scale structures. A new testing program at Sandia is quantifying the strength distribution using polysilicon samples that reflect the dimensions of critical MEMS components. The strength of polysilicon fabricated at Sandia's Microelectronic Development Laboratory was successfully measured using samples 2.5 microns thick, 1.7 microns wide with lengths between 15 and 25 microns. These tensile specimens have a freely moving hub on one end that anchors the sample to the silicon die and allows free rotation. Each sample is loaded in uniaxial tension by pulling laterally with a flat tipped diamond in a computer-controlled Nanoindenter. The stress-strain curve is calculated using the specimen cross section and gage length dimensions verified by measuring against a standard in the SEM

Testing of Critical Features of Polysilicon MEMS

The behavior of MEMS devices is limited by the strength of critical features such as thin ligaments, oxide cuts joining layers, pin joints and hinges. Devices fabricated at Sandia's Microelectronic Development Laboratory have been successfully tested to investigate these features. A series of measurements were performed on samples with gage lengths of 15 to 1000 microns, using conventional and tungsten coated samples as well as samples that include the critical features of standard components in the test section. Specimens have a freely moving pin joint on one end that anchors the sample to the silicon die to allow rotation to reduce effects of bending. Each sample is loaded in uniaxial tension by pulling laterally with a flat tipped diamond in a computer-controlled Nanoindenter. Load is calculated by resolving the measured lateral and normal forces into the applied tensile force and frictional losses. The specimen cross section and gage length dimensions were verified by measuring against a standard in the SEM. Multiple tests can be programmed at one time and performed without operator assistance allowing the collection of significant populations of data

Strength of Polysilicon for MEMS Devices

The safe, secure and reliable application of Microelectromechanical Systems (MEMS) devices requires knowledge about the distribution in material and mechanical properties of the small-scale structures. A new testing program at Sandia is quantifying the strength distribution using polysilicon samples that reflect the dimensions of critical MEMS components. The strength of polysilicon fabricated at Sandia's Microelectronic Development Laboratory was successfully measured using samples 2.5 microns thick, 1.7 microns wide with lengths between 15 and 25 microns. These tensile specimens have a freely moving hub on one end that anchors the sample to the silicon die and allows free rotation. Each sample is loaded in uniaxial tension by pulling laterally with a flat tipped diamond in a computer-controlled Nanoindenter. The stress-strain curve is calculated using the specimen cross section and gage length dimensions verified by measuring against a standard in the SEM