2,521 research outputs found
Diffuse Atomic and Molecular Gas near IC443
We present an analysis of results on absorption from Ca II, Ca I, K I, and
the molecules CH+, CH, C2, and CN that probes gas interacting with the
supernova remnant IC443. The eleven directions sample material across the
visible nebula and beyond its eastern edge. Most of the neutral material,
including the diatomic molecules, is associated with the ambient cloud detected
via H I and CO emission. Analysis of excitation and chemistry yields gas
densities that are typical of diffuse molecular gas. The low density gas probed
by Ca II extends over a large range in velocities, from -120 to +80 km/s in the
most extreme cases. This gas is distributed among several velocity components,
unlike the situation for the shocked molecular clumps, whose emission occurs
over much the same range but as very broad features. The extent of the
high-velocity absorption suggests a shock velocity of 100 km/s for the
expanding nebula.Comment: To be published in Ap
Acute response and chronic stimulus for cardiac structural and functional adaptation in a professional boxer.
The individual response to acute and chronic changes in cardiac structure and function to intense exercise training is not fully understood and therefore evidence in this setting may help to improve the timing and interpretation of pre-participation cardiac screening. The following case report highlights an acute increase in right ventricular (RV) size and a reduction in left ventricular (LV) basal radial function with concomitant increase at the mid-level in response to a week's increase in training volume in a professional boxer. These adaptations settle by the second week; however, chronic physiological adaptation occurs over a 12-week period. Electrocardiographic findings demonstrate an acute lateral T-wave inversion at 1 week, which revert to baseline for the duration of training. It appears that a change in training intensity and volume generates an acute response within the RV that acts as a stimulus for chronic adaptation in this professional boxer
Electrical activation and electron spin resonance measurements of implanted bismuth in isotopically enriched silicon-28
We have performed continuous wave and pulsed electron spin resonance
measurements of implanted bismuth donors in isotopically enriched silicon-28.
Donors are electrically activated via thermal annealing with minimal diffusion.
Damage from bismuth ion implantation is repaired during thermal annealing as
evidenced by narrow spin resonance linewidths (B_pp=12uT and long spin
coherence times T_2=0.7ms, at temperature T=8K). The results qualify ion
implanted bismuth as a promising candidate for spin qubit integration in
silicon.Comment: 4 pages, 4 figure
Opening up the Quantum Three-Box Problem with Undetectable Measurements
One of the most striking features of quantum mechanics is the profound effect
exerted by measurements alone. Sophisticated quantum control is now available
in several experimental systems, exposing discrepancies between quantum and
classical mechanics whenever measurement induces disturbance of the
interrogated system. In practice, such discrepancies may frequently be
explained as the back-action required by quantum mechanics adding quantum noise
to a classical signal. Here we implement the 'three-box' quantum game of
Aharonov and Vaidman in which quantum measurements add no detectable noise to a
classical signal, by utilising state-of-the-art control and measurement of the
nitrogen vacancy centre in diamond.
Quantum and classical mechanics then make contradictory predictions for the
same experimental procedure, however classical observers cannot invoke
measurement-induced disturbance to explain this discrepancy. We quantify the
residual disturbance of our measurements and obtain data that rule out any
classical model by > 7.8 standard deviations, allowing us for the first time to
exclude the property of macroscopic state-definiteness from our system. Our
experiment is then equivalent to a Kochen-Spekker test of quantum
non-contextuality that successfully addresses the measurement detectability
loophole
The Evolution of Ga and as Core Levels in the Formation of Fe/GaAs (001): A High Resolution Soft X-Ray Photoelectron Spectroscopic Study
A high resolution soft x-ray photoelectron spectroscopic study of Ga and as 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness. This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer—a quantitative analysis of the acquired spectra indicates significantly differing behavior of Ga and as during Fe growth, and our observations have been compared with existing theoretical models. Our results demonstrate that the outdiffusing Ga and as remain largely confined to the interface region, forming a thin intermixed layer. Whereas at low coverages Fe has little influence on the underlying GaAs substrate, the onset of substrate disruption when the Fe thickness reaches 3.5 Å results in major changes in the energy distribution curves (EDCs) of both as and Ga 3d cores. Our quantitative analysis suggests the presence of two additional as environments of metallic character: one bound to the interfacial region and another which, as confirmed by in situ oxidation experiments, surface segregates and persists over a wide range of overlayer thickness. Analysis of the corresponding Ga 3d EDCs found not two, but three additional environments—also metallic in nature. Two of the three are interface resident whereas the third undergoes outdiffusion at low Fe coverages. Based on the variations of the integrated intensities of each component, we present a schematic of the proposed chemical makeup of the Fe/GaAs (001) system
Prospects for precision measurements of atomic helium using direct frequency comb spectroscopy
We analyze several possibilities for precisely measuring electronic
transitions in atomic helium by the direct use of phase-stabilized femtosecond
frequency combs. Because the comb is self-calibrating and can be shifted into
the ultraviolet spectral region via harmonic generation, it offers the prospect
of greatly improved accuracy for UV and far-UV transitions. To take advantage
of this accuracy an ultracold helium sample is needed. For measurements of the
triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap
metastable 2^3S state atoms. We analyze schemes for measuring the two-photon
interval, and for resonant two-photon excitation to high
Rydberg states, . We also analyze experiments on the
singlet-state spectrum. To accomplish this we propose schemes for producing and
trapping ultracold helium in the 1^1S or 2^1S state via intercombination
transitions. A particularly intriguing scenario is the possibility of measuring
the transition with extremely high accuracy by use of
two-photon excitation in a magic wavelength trap that operates identically for
both states. We predict a ``triple magic wavelength'' at 412 nm that could
facilitate numerous experiments on trapped helium atoms, because here the
polarizabilities of the 1^1S, 2^1S and 2^3S states are all similar, small, and
positive.Comment: Shortened slightly and reformatted for Eur. Phys. J.
TESS Discovery of a Transiting Super-Earth in the Mensae System
We report the detection of a transiting planet around Mensae (HD
39091), using data from the Transiting Exoplanet Survey Satellite (TESS). The
solar-type host star is unusually bright (V=5.7) and was already known to host
a Jovian planet on a highly eccentric, 5.7-year orbit. The newly discovered
planet has a size of and an orbital period of 6.27
days. Radial-velocity data from the HARPS and AAT/UCLES archives also displays
a 6.27-day periodicity, confirming the existence of the planet and leading to a
mass determination of . The star's proximity and
brightness will facilitate further investigations, such as atmospheric
spectroscopy, asteroseismology, the Rossiter--McLaughlin effect, astrometry,
and direct imaging.Comment: Accepted for publication ApJ Letters. This letter makes use of the
TESS Alert data, which is currently in a beta test phase. The discovery light
curve is included in a table inside the arxiv submissio
Time-Series Analysis of Mortality Effects of Fine Particulate Matter Components in Detroit and Seattle
Ernst Freund as Precursor of the Rational Study of Corporate Law
Gindis, David, Ernst Freund as Precursor of the Rational Study of Corporate Law (October 27, 2017). Journal of Institutional Economics, Forthcoming. Available at SSRN: https://ssrn.com/abstract=2905547, doi: https://dx.doi.org/10.2139/ssrn.2905547The rise of large business corporations in the late 19th century compelled many American observers to admit that the nature of the corporation had yet to be understood. Published in this context, Ernst Freund's little-known The Legal Nature of Corporations (1897) was an original attempt to come to terms with a new legal and economic reality. But it can also be described, to paraphrase Oliver Wendell Holmes, as the earliest example of the rational study of corporate law. The paper shows that Freund had the intuitions of an institutional economist, and engaged in what today would be called comparative institutional analysis. Remarkably, his argument that the corporate form secures property against insider defection and against outsiders anticipated recent work on entity shielding and capital lock-in, and can be read as an early contribution to what today would be called the theory of the firm.Peer reviewe
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