12,251 research outputs found
New Limits on Local Lorentz Invariance in Mercury and Cesium
We report new bounds on Local Lorentz Invariance (LLI) violation in Cs and
Hg. The limits are obtained through the observation of the the spin- precession
frequencies of 199Hg and 133Cs atoms in their ground states as a function of
the orientation of an applied magnetic field with respect to the fixed stars.
We measure the amplitudes of the dipole couplings to a preferred direction in
the equatorial plane to be 19(11) nHz for Hg and 9(5) microHz for Cs. The upper
bounds established here improve upon previous bounds by about a factor of four.
The improvement is primarily due to mounting the apparatus on a rotating table.
New bounds are established on several terms in the standard model extension
including the first bounds on the spin-couplings of the neutron and proton to
the z direction, <7e-30 GeV and <7e-29 GeV, respectively.Comment: 17 pages, 6 figure
Deep Radio Continuum Imaging of the Dwarf Irregular Galaxy IC10: Tracing Star Formation and Magnetic Fields
We exploit the vastly increased sensitivity of the Expanded Very Large Array
(EVLA) to study the radio continuum and polarization properties of the
post-starburst, dwarf irregular galaxy IC10 at 6 cm, at a linear resolution of
~50 pc. We find close agreement between radio continuum and Halpha emission,
from the brightest HII regions to the weaker emission in the disk. A
quantitative analysis shows a strictly linear correlation, where the thermal
component contributes 50% to the total radio emission, the remainder being due
to a non-thermal component with a surprisingly steep radio spectral index of
between -0.7 and -1.0 suggesting substantial radiation losses of the cosmic-ray
electrons. We confirm and clearly resolve polarized emission at the 10-20%
level associated with a non-thermal superbubble, where the ordered magnetic
field is possibly enhanced due to the compression of the expanding bubble. A
fraction of the cosmic-ray electrons has likely escaped because the measured
radio emission is a factor of 3 lower than what is suggested by the Halpha
inferred SFR.Comment: 15 pages, 5 figures, accepted for publication in the EVLA Special
Issue of ApJ Letter
Effects of Sex and Gender on Adaptation to Space: Musculoskeletal Health
There is considerable variability among individuals in musculoskeletal response to long-duration spaceflight. The specific origin of the individual variability is unknown but is almost certainly influenced by the details of other mission conditions such as individual differences in exercise countermeasures, particularly intensity of exercise, dietary intake, medication use, stress, sleep, psychological profiles, and actual mission task demands. In addition to variations in mission conditions, genetic differences may account for some aspect of individual variability. Generally, this individual variability exceeds the variability between sexes that adds to the complexity of understanding sex differences alone. Research specifically related to sex differences of the musculoskeletal system during unloading is presented and discussed
Mandatory Disclosure and Peer Firm Managers’ Learning from Stock Prices
Research suggests that mandatory disclosure hinders managers’ ability to learn from their own stock prices in making investment decisions. We build on this research by examining how mandatory disclosure impacts the learning of managers of peer firms. Using the introduction of mandatory segment disclosure under SFAS 131, we document a significant decrease in investment-q sensitivity for peer firms, suggesting decreased investment efficiency. We also find that the decrease in sensitivity is concentrated among peers with lower financial constraints and higher informed trading, as well as those with greater economic links to disclosing firms. Collectively, our findings suggest that mandatory disclosure interferes with peer firm managers’ learning from their own stock prices. We provide novel evidence that mandatory disclosure has negative externalities to peer firms’ investment
Type I Superconductivity in YbSb2 Single Crystals
We present evidence of type I superconductivity in YbSb2 single crystals,
from DC and AC magnetization, heat capacity and resistivity measurements. The
critical temperature and critical field are determined to be 1.3 K
and 55 Oe. A small Ginzburg-Landau parameter \kappa = 0.05,
together with typical magnetization isotherms of type I superconductors, small
critical field values, a strong Differential Paramagnetic Effect (DPE) signal,
and a field-induced change from second to first order phase transition, confirm
the type I nature of the superconductivity in YbSb2. A possible second
superconducting state is observed in the radiofrequency (RF) susceptibility
measurements, with 0.41 K and 430 Oe.Comment: 6 pages, 10 figure
An Overview of AUV Algorithms Research and Testbed at the University of Michigan
This paper provides a general overview of the autonomous underwater vehicle (AUV) research projects being pursued within the Perceptual Robotics Laboratory (PeRL) at the University of Michigan. Founded in 2007, PeRL's research thrust is centered around improving AUV autonomy via algorithmic advancements in sensor-driven perceptual feedback for environmentally-based real-time mapping, navigation, and control. In this paper we discuss our three major research areas of: (1) real-time visual simultaneous localization and mapping (SLAM); (2) cooperative multi-vehicle navigation; and (3) perception-driven control. Pursuant to these research objectives, PeRL has acquired and significantly modified two commercial off-the-shelf (COTS) Ocean-Server Technology, Inc. Iver2 AUV platforms to serve as a real-world engineering testbed for algorithm development and validation. Details of the design modification, and related research enabled by this integration effort, are discussed herein.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86058/1/reustice-15.pd
Farmers that engage in entrepreneurship for the “wrong” reason and the moderating role of cultural intolerance
In the agricultural sector, the Law of Jante—a Scandinavian form of cultural intolerance towards standing out, being different and overachieving (akin to the Tall Poppy Syndrome and The nail that sticks out gets hammered down culture found in other countries)—may play an important role by influencing when entrepreneurship is an acceptable strategic choice to adversity. Based on a three group, between-subjects experiment of 122 Swedish university students studying agricultural and rural management, we tested whether the advice our participants gave to a fictitious farmer to pursue entrepreneurial activity depended on information regarding the farmer's motivation to pursue entrepreneurship (experimental treatments included motivation scenarios based on necessity vs. opportunity driven vs. control). Moreover, we test whether entrepreneurial advice is moderated by the participants own “Jante-ness”. Unexpectedly, we found that our participants did not adapt the entrepreneurship advice they give to the situational context, nor does Jante play a moderating role; instead we found that Jante had a significant and negative main effect on the entrepreneurial advice given. This finding suggests that Jante is still very much alive and may play an important role in explaining relatively low rates of innovation and entrepreneurship in (Swedish) agriculture
CARMIL2 is a novel molecular connection between vimentin and actin essential for cell migration and invadopodia formation
A Methodology to Compensate for Part Compliance During Robotic Machining
Machining thin-walled, compliant parts is a cost-efficient way to manufacture lightweight and structurally sound parts as used extensively in the aerospace industry. Such parts are difficult to machine using traditional CNC machines due to part compliance, increased susceptibility to chatter, and the need for specialized tooling or fixturing devices. These challenges are heightened while machining with a robotic manipulator due to its lower stiffness and easily excited dynamics. However, due to the unique benefits of industrial robotic manipulators such as low cost and a large workspace to footprint ratio, there has been extensive research to maximize the accuracy and path compensation of robotic manipulators. This thesis introduces a methodology to compensate the path of a robotic manipulator to increase the accuracy of peripherally milled compliant parts. The research purpose is to develop an offline path compensation methodology as a solution to the part inaccuracies that occur during machining due to part compliance arising from the forces involved in machining. Two approaches to the compensation methodology are pursued in this thesis. The first approach utilizes experimentally determined dimensional errors to iteratively compensate a nominal path. In the second approach, milling force and part deflection models are used to predict the path compensation needed to compensate the part compliance induced errors. Experiments are performed on a 6-DOF industrial robotic manipulator with a laser-tracker based real-time closed-loop feedback control system. The experiments demonstrate the effectiveness of the iterative robot path compensation strategy in improving part accuracy. The benefits and implications of the compensation strategy are discussed and future improvements to the methodology are recommended.M.S
Striatal neuroinflammation promotes parkinsonism in rats
The specific role of neuroinflammation in the pathogenesis of Parkinson's disease remains to be fully elucidated. By infusing lipopolysaccharide (LPS) into the striatum, we investigated the effect of neuroinflammation on the dopamine nigrostriatal pathway. Here, we report that LPS-induced neuroinflammation in the striatum causes progressive degeneration of the dopamine nigrostriatal system, which is accompanied by motor impairments resembling parkinsonism. Our results indicate that neurodegeneration is associated with defects in the mitochondrial respiratory chain related to extensive S-nitrosylation/nitration of mitochondrial proteins. Mitochondrial injury was prevented by treatment of L-N^6^-(l-iminoethyl)-lysine, an inducible nitric oxide synthase (iNOS) inhibitor, suggesting that iNOS-derived NO is responsible for mitochondrial dysfunction. Furthermore, the nigral dopamine neurons exhibited intracytoplasmic [alpha]-synuclein and ubiquitin accumulation. These results demonstrate that degeneration of nigral dopamine neurons by neuroinflammation is associated with mitochondrial malfunction induced by NO-mediated S-nitrosylation/nitration of mitochondrial proteins
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