48 research outputs found
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
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
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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
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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
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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