8,342 research outputs found

    Building Booster Separation Aerodynamic Databases for Artemis II

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    NASAs Artemis II mission will mark the return of humans to near-lunar space for the first time since Apollo. Shortly after launch on the Space Launch System (SLS), a critical phase of ascent occurs when 16 small rockets fire to push the boosters away from the core. Minimizing the risk of failure during separation requires the construction of multiple 13-dimensional databases, including perturbations in position, flight conditions, and engine thrust. The SLS Computational Fluid Dynamics team used NASAs FUN3D flow solver on the Pleiades and Electra supercomputers to run 5,780 simulations at nominal conditions and over 8,000 simulations with a core stage engine failure to generate the databases needed to verify the booster separation system for Artemis II

    Deterministic Domain Wall Motion Orthogonal To Current Flow Due To Spin Orbit Torque.

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    Spin-polarized electrons can move a ferromagnetic domain wall through the transfer of spin angular momentum when current flows in a magnetic nanowire. Such current induced control of a domain wall is of significant interest due to its potential application for low power ultra high-density data storage. In previous reports, it has been observed that the motion of the domain wall always happens parallel to the current flow - either in the same or opposite direction depending on the specific nature of the interaction. In contrast, here we demonstrate deterministic control of a ferromagnetic domain wall orthogonal to current flow by exploiting the spin orbit torque in a perpendicularly polarized Ta/CoFeB/MgO heterostructure in presence of an in-plane magnetic field. Reversing the polarity of either the current flow or the in-plane field is found to reverse the direction of the domain wall motion. Notably, such orthogonal motion with respect to current flow is not possible from traditional spin transfer torque driven domain wall propagation even in presence of an external magnetic field. Therefore the domain wall motion happens purely due to spin orbit torque. These results represent a completely new degree of freedom in current induced control of a ferromagnetic domain wall

    Effects of remote limb ischemic conditioning on muscle strength in healthy young adults: A randomized controlled trial

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    Remote limb ischemic conditioning (RLIC) is a clinically feasible method in which brief, sub-lethal bouts of ischemia protects remote organs or tissues from subsequent ischemic injury. A single session of RLIC can improve exercise performance and increase muscle activation. The purpose of this study, therefore, was to assess the effects of a brief, two-week protocol of repeated RLIC combined with strength training on strength gain and neural adaptation in healthy young adults. Participants age 18-40 years were randomized to receive either RLIC plus strength training (n = 15) or sham conditioning plus strength training (n = 15). Participants received RLIC or sham conditioning over 8 visits using a blood pressure cuff on the dominant arm with 5 cycles of 5 minutes each alternating inflation and deflation. Visits 3-8 paired conditioning with wrist extensors strength training on the non-dominant (non-conditioned) arm using standard guidelines. Changes in one repetition maximum (1 RM) and electromyography (EMG) amplitude were compared between groups. Both groups were trained at a similar workload. While both groups gained strength over time (P = 0.001), the RLIC group had greater strength gains (9.38 ± 1.01 lbs) than the sham group (6.3 ± 1.08 lbs, P = 0.035). There was not a significant group x time interaction in EMG amplitude (P = 0.231). The RLIC group had larger percent changes in 1 RM (43.8% vs. 26.1%, P = 0.003) and EMG amplitudes (31.0% vs. 8.6%, P = 0.023) compared to sham conditioning. RLIC holds promise for enhancing muscle strength in healthy young and older adults, as well as clinical populations that could benefit from strength training

    Leading Groups To Create Healthy Culture Through Accomplishing Tasks Aligned To Strategy

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    This study examined the link between the consistency of self-evaluation versus peer-evaluation of managers’ skills and the level of relational stress in an organization and was based on two models: (a) the Competing Values Framework (CVF), which measures different management skills of individuals in an organization, and (b) the Healthy versus Toxic Organization Model, which focuses on the stress level in partnerships.  The researchers hypothesized that the lower the stress in the organization, the more consistent the results will be between self-evaluation and peer-evaluation. In an empirical analysis, the researchers found that the relationship was most visible in the area of managers’ facilitator skills. With strong facilitator skills, managers can lead their organizations effectively and stay focused on maintaining strategic alignment. The study also examined how management skills could be most effective in developing a healthy work culture

    OncoLog Volume 48, Number 09, September 2003

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    Sentinel Lymph Node Biopsy: Detection of Micrometastases Leads to More Precise Staging of Breast and Melanoma Tumors Sentinel Lymph Node Biopsy Shows Promise in Eye and Colon Cancers New Research Promotes a More Dynamic View of Adult Stem Cell Differentiation: Hematopoietic Stem Cells May One Day Be Used to Repair Tissue Damage Caused by Radiation Therapy or Chemotherapy House Call: Understanding the Buzz over Stem Cells DiaLog: Directed Parathyroid Surgery, by Jeffrey E. Lee, MD, Professor, Department of Surgical Oncologyhttps://openworks.mdanderson.org/oncolog/1122/thumbnail.jp

    Vortices and the entrainment transition in the 2D Kuramoto model

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    We study synchronization in the two-dimensional lattice of coupled phase oscillators with random intrinsic frequencies. When the coupling KK is larger than a threshold KEK_E, there is a macroscopic cluster of frequency-synchronized oscillators. We explain why the macroscopic cluster disappears at KEK_E. We view the system in terms of vortices, since cluster boundaries are delineated by the motion of these topological defects. In the entrained phase (K>KEK>K_E), vortices move in fixed paths around clusters, while in the unentrained phase (K<KEK<K_E), vortices sometimes wander off. These deviant vortices are responsible for the disappearance of the macroscopic cluster. The regularity of vortex motion is determined by whether clusters behave as single effective oscillators. The unentrained phase is also characterized by time-dependent cluster structure and the presence of chaos. Thus, the entrainment transition is actually an order-chaos transition. We present an analytical argument for the scaling KEKLK_E\sim K_L for small lattices, where KLK_L is the threshold for phase-locking. By also deriving the scaling KLlogNK_L\sim\log N, we thus show that KElogNK_E\sim\log N for small NN, in agreement with numerics. In addition, we show how to use the linearized model to predict where vortices are generated.Comment: 11 pages, 8 figure

    ICESat-2 Photon Classification: Finding Signal Photons in the ATL03 Geolocated Photon Data Product

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    ICESat-2 carries NASA's next-generation laser altimeter, ATLAS, (Advanced Topographic Laser Altimeter System), designed to measure changes in ice sheet height, sea ice freeboard, and vegetation canopy height. ATLAS contains a photon-counting lidar which transmits green (532-nm) pulses at 10kHz. Each pulse is split into 3 pairs of beams (one strong and one weak). Approximately 1014 photons per pulse travel from ATLAS through the atmosphere to reflect off the Earth's surface. Some return back into the ATLAS telescope where they are recorded. Photons from sunlight and instrument noise at the same wavelength are also recorded. The flight software time tags all photons within a 500m to 6 km range window and generates histograms. Using the histograms, it selects a telemetry window which varies from 20m over flat surfaces to hundreds of meters over rougher terrain. ATL03 contains the time, height (relative to the WGS-84 ellipsoid), latitude and longitude of every photon within the telemetry window. The basic challenge is to determine which of these photons were reflected off the surface. We have developed an algorithm that identifies these signal photons and assigns a confidence level (low, medium, or high) to each signal photon based on the signal to noise ratio. We present an overview of the signal identification algorithm and show the results on actual ICESat-2 data over ice sheet, sea ice, vegetated, and water surfaces. Higher level ATLAS products work with aggregations of the photons in order to determine the ellipsoidal height of the Earth, canopy height and structure, and other quantities of geophysical interest

    Analysis of wave III of brain stem auditory evoked potential waveforms during microvascular decompression of cranial nerve VII for hemifacial spasm

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    INTRODUCTION:: Intraoperative monitoring of brain stem auditory evoked potential during microvascular decompression (MVD) prevent hearing loss (HL). Previous studies have shown that changes in wave III (wIII) are an early and sensitive sign of auditory nerve injury. OBJECTIVE:: To evaluate the changes of amplitude and latency of wIII of brain stem auditory evoked potential during MVD and its association with postoperative HL. Hearing loss was classified by American Academy of Otolaryngology - Head and Neck Surgery (AAO-HNS) criteria, based on changes in pure tone audiometry and speech discrimination score. METHODS:: Retrospective analysis of wIII in patients who underwent intraoperative monitoring with brain stem auditory evoked potential during MVD was performed. A univariate logistic regression analysis was performed on independent variables amplitude of wIII and latency of wIII at change max and On-Skin, or a final recording at the time of skin closure. A further analysis for the same variables was performed adjusting for the loss of wave. RESULTS:: The latency of wIII was not found to be significantly different between groups I and II. The amplitude of wIII was significantly decreased in the group with HL. Regression analysis did not find any increased odds of HL with changes in the amplitude of wIII. CONCLUSIONS:: Changes in wave III did not increase the odds of HL in patients who underwent brain stem auditory evoked potential s during MVD. This information might be valuable to evaluate the value of wIII as an alarm criterion during MVD to prevent HL. © 2014 by the American Clinical Neurophysiology Society
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