1,713 research outputs found

    The Integer Valued SU(3) Casson Invariant for Brieskorn spheres

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    We develop techniques for computing the integer valued SU(3) Casson invariant. Our method involves resolving the singularities in the flat moduli space using a twisting perturbation and analyzing its effect on the topology of the perturbed flat moduli space. These techniques, together with Bott-Morse theory and the splitting principle for spectral flow, are applied to calculate the invariant for all Brieskorn homology spheres.Comment: 50 pages, 3 figure

    Gauge Theoretic Invariants of, Dehn Surgeries on Knots

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    New methods for computing a variety of gauge theoretic invariants for homology 3-spheres are developed. These invariants include the Chern-Simons invariants, the spectral flow of the odd signature operator, and the rho invariants of irreducible SU(2) representations. These quantities are calculated for flat SU(2) connections on homology 3-spheres obtained by 1/k Dehn surgery on (2,q) torus knots. The methods are then applied to compute the SU(3) gauge theoretic Casson invariant (introduced in [H U Boden and C M Herald, The SU(3) Casson invariant for integral homology 3--spheres, J. Diff. Geom. 50 (1998) 147-206]) for Dehn surgeries on (2,q) torus knots for q=3,5,7 and 9.Comment: Version 3: minor corrections from version 2. Published by Geometry and Topology at http://www.maths.warwick.ac.uk/gt/GTVol5/paper6.abs.htm

    Intraoperative detection of blood vessels with an imaging needle during neurosurgery in humans

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    Intracranial hemorrhage can be a devastating complication associated with needle biopsies of the brain. Hemorrhage can occur to vessels located adjacent to the biopsy needle as tissue is aspirated into the needle and removed. No intraoperative technology exists to reliably identify blood vessels that are at risk of damage. To address this problem, we developed an “imaging needle” that can visualize nearby blood vessels in real time. The imaging needle contains a miniaturized optical coherence tomography probe that allows differentiation of blood flow and tissue. In 11 patients, we were able to intraoperatively detect blood vessels (diameter, \u3e500 μm) with a sensitivity of 91.2% and a specificity of 97.7%. This is the first reported use of an optical coherence tomography needle probe in human brain in vivo. These results suggest that imaging needles may serve as a valuable tool in a range of neurosurgical needle interventions

    Electromyographic Analysis of Abdominal and Low Back Musculature during Use of an Experimental Stationary Bicycle

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    Background and Purpose. Currently, stationary bicycles do not incorporate exercise for the abdominal and low back musculature. An experimental stationary bicycle, the Magnus Cycle, has been developed to increase trunk muscle activation and, at the same time, provide aerobic conditioning. The purpose of this study is to assess the activity of the rectus abdominus, external oblique, erector spinae, rectus femoris and biceps femoris muscles during a stationary cycling setting and during a tilt-in-space setting of the Magnus Cycle. Subjects. Sixteen subjects, both men and women, between the ages of 18 and 30 participated in this study. Methods. Surface electromyography (EMG) was used to assess muscle activity from the rectus abdominus, external oblique, erector spinae, rectus femoris, and biceps femoris muscles during each phase of stationary and oscillating exercise. The raw EMG signal was rectified, smoothed and normalized to the respective muscle maximal voluntary contraction prior to data analysis. A repeated measures t-test was utilized to assess differences in EMG activity between minutes one and three of stationary cycling. DIfferences in the oscillating condition for forward and backward tilt was assessed using a repeated measures ANOVA, alpha = 0.05. For trials without differences between oscillations, one way ANOV A was performed to determine differences between stationary, foot forward, and foot backward tilt conditions. Results. In the feet forward position, the rectus abdominis, external obliques, and rectus femoris demonstrated significantly higher EMG activation compared to both the stationary and feet backward conditions (p\u3c.05). Activity of the erector spinae and biceps femoris muscles were not affected by the feet forward position. However, in the feet backward position, the erector spinae and biceps femoris muscles demonstrated significantly higher EMG activity compared to the stationary position and feet forward positions (p\u3c.05). The rectus abdominis, external obliques, and rectus femoris muscles were not affected by the feet backward condition. Discussion and Conclusion. The tilting Magnus Cycle significantly enhances activation of the rectus abdominis, external oblique, erector spinae, rectus femoris, and biceps femoris muscles compared to stationary cycling. The enhanced trunk muscle activity may make the Magnus Cycle a better option for a quicker, more beneficial workout than standard stationary bicycles

    Binding of Human Immunodeficiency Virus Type 1 Nucleocapsid Protein to Ψ-RNA-SL3

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    The interaction of the nucleocapsid protein NCp7, from the pNL4-3 isolate of HIV-1, with Ψ-RNA-SL3, with the sequence 5’-GGACUAGCGGAGGCUAGUCC, was studied using non-denaturing gel electrophoresis. Two kinds of experiments were performed, using buffered solutions of radiolabeled RNA and unlabeled protein. In the ‘dilution’ experiments, the total RNA concentration, RT, was varied for a series of solutions, but kept equal to the total protein concentration, PT. In the ‘titration’ experiments, solutions having RT constant but with varying PT were analyzed. The solutions were electrophoresed and the autoradiographic spot intensities, proportional to the amounts of the different species present, were measured. The intensities were fit to a number of equilibrium models, differing in species stoichiometries, by finding the best values of the binding constants. It was shown that NCp7 protein and SL3 RNA combine to form at least two complexes. When PT is below approximately 10 μM, a complex that contains two RNAs and one protein forms. Increasing PT to approximately 100 μM causes the 2:1 complex to oligomerize, forming a species having eight RNAs and four proteins. For the dilution experiments, run at 5 ̊C at an ionic strength of 31 mM, we found K1 for the 2:1 complex is ̴ 1011 M-2 and K2 for the 8:4 complex is ̴ 1016 M-3. The titration experiments returned K1 ̴ 107 M-2 (poorly determined) and K1 ̴ 1019 M-3. The analysis was complicated by the loss of RNA at higher protein concentrations, due to formation of an insoluble species containing both RNA and protein, which does not enter the gel. Correcting for this changes the calculated values of equilibrium constants, but not the molecularities determined by our analysis. The observation that a small complex can oligomerize to form a larger species is consistent with the fact that NCp7 organizes and condenses the genome in the virus particle

    Contemplating Mindfulness at Work: An Integrative Review

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    Mindfulness research activity is surging within organizational science. Emerging evidence across multiple fields suggests that mindfulness is fundamentally connected to many aspects of workplace functioning, but this knowledge base has not been systematically integrated to date. This review coalesces the burgeoning body of mindfulness scholarship into a framework to guide mainstream management research investigating a broad range of constructs. The framework identifies how mindfulness influences attention, with downstream effects on functional domains of cognition, emotion, behavior, and physiology. Ultimately, these domains impact key workplace outcomes, including performance, relationships, and well-being. Consideration of the evidence on mindfulness at work stimulates important questions and challenges key assumptions within management science, generating an agenda for future research

    Low Mass Printable Devices for Energy Capture, Storage, and Use for Space Exploration Missions

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    The energy-efficient, environmentally friendly technology that will be presented is the result of a Space Act Agreement between -Technologies Worldwide, Inc., and the National Aeronautics and Space Administration s (NASA s) Marshall Space Flight Center (MSFC). This work combines semiconductor and printing technologies to advance lightweight electronic and photonic devices having excellent potential for commercial and exploration applications, and is an example of industry and government cooperation that leads to novel inventions. Device development involves three energy generation and consumption projects: 1) a low mass efficient (low power, low heat emission) micro light-emitting diode (LED) area lighting device; 2) a low-mass omni-directional efficient photovoltaic (PV) device with significantly improved energy capture; and 3) a new approach to building supercapacitors. These three technologies - energy capture, storage, and usage (e.g., lighting) - represent a systematic approach for building efficient local micro-grids that are commercially feasible; furthermore, these same technologies will be useful for lightweight power generation that enables inner planetary missions using smaller launch vehicles and facilitates surface operations. The PV device model is a two-sphere, light-trapped sheet approximately 2-mm thick. The model suggests a significant improvement over current thin film systems. All three components may be printed in line by printing sequential layers on a standard screen or flexographic direct impact press using the threedimensional printing technique (3DFM) patented by NthDegree. MSFC is testing the robustness of prototype devices in the harsh space and lunar surface environments, and available results will be reported. Unlike many traditional light sources, this device does not contain toxic compounds, and the LED component has passed stringent off-gassing tests required for potential manifesting on spacecraft such as the International Space Station. Future exploration missions will benefit from "green" technology lighting devices such as this, which show great promise for both terrestrial use and space missions

    Kinetics of Cleavage of Intra- and Extracellular Simian Virus 40 DNA with the Enediyne Anticancer Drug C- 1027

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    A kinetic analysis of cleavage of simian virus DNA (SV40 DNA) inside and outside green monkey BSC-I cells by the enediyne-protein antibiotic C-1027 and its free chromophore is described. Information on rate constants was obtained by fitting populations of forms I (closed circular DNA), II (nicked circular DNA) and III (linear DNA) of SV4f.J DNA as a function of drug concentration to a kinetic model which includes: cutting of form I to give form II with rate constant k1. cutting of form I to give form III with rate constant k4, and cutting of form II to give form III with rate constant k2. Theratio of single-strand (ss) to double-strand (ds) cutting for the holoantibiotic and the free chromophore. k1/k4, is approximately 1.8 for extracellular SV40 DNA. For intracellular DNA and extracellular DNA which has been post-treated with putrescine, ds cutting is much more probable, with k4, about four times as large as k1. This observation suggests that amine groups present in the cell are able to convert abasic sites opposite an ss break into a ds break in SV40 chkomatin. The overall rate of cleavage of form-1 DNA inside the cell is much larger than the rate outside, the sum k1 + k4 being about three times as large for intracellular DNA as for extracellular DNA

    Towards a Pseudocapacitive Battery: Benchmarking the Capabilities of Quantized Capacitance for Energy Storage

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    Despite being capable of very fast charging, the pseudocapacitive properties of electrochemical capacitors still require significant research to attain energy densities comparable to that of batteries. Herein we discuss and theoretically benchmark the physics of quantized capacitance as a Faradaic charge storage mechanism, providing near “ideal” pseudocapacitive properties in the context of batterylike energy storage. Through careful electrolyte and reactant engineering, our physical analysis suggests that this less explored “pseudocapacitive battery” mechanism could provide power densities of approximately 10 4 W/L combined with volumetric energy densities in the range of 100 Wh/L (or potentially greater). These benchmarks are arrived at though a comprehensive analysis of two-dimensional (2D) graphitic nanoparticles considering the impact of solvation, electron-electron interactions, and electron transfer processes. In general, our findings indicate that 2D nanomaterials exhibiting quantized capacitance provide a promising and underexplored physical axis within electrochemical capacitors towards realizing very fast charging at energy densities comparable to that of batteries
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