5,310 research outputs found
Free-space Excitation of Resonant Cavities formed from Cloaking Metamaterial
We propose a new class of resonant electromagnetic structures, and study
their response to free-space illumination. The structures consist of partial
cylindrical shells that have cloaking material properties proposed by Pendry et
al. These metamaterial shells have apertures that allow the propagation of
incident irradiation into an interior resonant cavity. We use full wave
time-harmonic analysis to study the field distribution inside the cavity, and
show that an analogue of Whispering Gallery Modes (WGMs) can be efficiently
excited via free-space illumination.Comment: to appear J. Modern Optic
Strong Aperiodic X-ray Variability and Quasi-Periodic Oscillation in X-ray Nova XTE J1550-564
We report the discovery of strong aperiodic X-ray variability and
quasi-periodic oscillation (QPO) in the X-ray light curves of a new X-ray Nova,
XTE J1550-564, and the evolution of the observed temporal properties during the
rise of the recent X-ray outburst. The power spectral analysis of the first
observation reveals strong aperiodic X-ray variability of the source (~28%), as
well as the presence of a QPO at ~82 mHz with fractional rms amplitude ~14%
over the 2-60 keV energy range. Also apparent is the first harmonic of the QPO
with the amplitude ~9%. As the X-ray flux increases, the source tends to become
less variable, and the QPO frequency increases rapidly, from 82 mHz to 4 Hz,
over the flux (2-50 keV) range of 1.73-5.75 x 10^{-8} ergs cm^{-2} s^{-1}. The
amplitude of the fundamental component of the QPO varies little, while that of
the harmonic follows a decreasing trend. The fundamental component strengthens
toward high energies, while its harmonic weakens. Initially, the power spectrum
is roughly flat at low frequencies and turns into a power law at high
frequencies, with the QPO harmonic sitting roughly at the break. In later
observations, however, the high-frequency portion of the continuum can actually
be better described by a broken power law (as opposed to a simple power law).
This effect becomes more apparent at higher energies. The overall amplitude of
the continuum shows a similar energy dependence to that of the fundamental
component of the QPO. Strong rapid X-ray variability, as well as hard energy
spectrum, makes XTE J1550-564 a good black hole candidate. We compare its
temporal properties with those of other black hole candidates.Comment: 12 pages, including 5 figures. To appear in ApJ Letters, vol. 512
(1999
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Obesity and abdominal hernia in ambulatory patients, 2018-2023.
PURPOSE: To determine the relationship between abdominal hernia and obesity. Although obesity is frequently cited as a risk factor for abdominal hernia, few studies have confirmed this association (Menzo et al. Surg Obes Relat Dis 14:1221-1232. 10.1016/j.soard.2018.07.005, 2018). METHODS: A cross-sectional study of primary care ambulatory patients aged older than 16 years treated at UCLA Health from 01/01/2018 to 06/06/2023. Abdominal hernia was identified by clinic encounter ICD-10 codes (K40-K46). RESULTS: There were 41,703 hernias identified among 1,362,440 patients (306.1 per10,000) with a mean age of 62.5 ± 16.1 years, and 57.6% were men. Nearly half (44.7%) of all abdominal hernias were diaphragmatic. There was an approximately equal distribution of the ventral (28.7%) and inguinal (24.3%) hernia. Each hernia type had a different relationship with obesity: The odds of having a ventral hernia increased with BMI in both sexes: BMI 25-29.9 kg/m2 odds ratio (OR) = 1.65, (CI 1.56-1.74); BMI 30-39.9 kg/m2 OR = 2.42 (CI 2.29-2.56), BMI 40-49.9 kg/m2 OR = 2.28 (CI 2.05-2.54) and BMI >  = 50 kg/m2 OR = 2.54 (CI 2.03-3.17) all relative to normal BMI. In contrast, the odds of having an inguinal hernia decreased with obesity relative to normal weight [obesity (BMI 30-39.9 kg/m2): OR = 0.60 (CI 0.56-0.65)], morbid obesity (BMI 40-49.9 kg/m2): OR = 0.29 (CI 0.23-0.37). The OR for diaphragmatic hernia peaks with obesity in women and overweight status in men but was found to decrease with morbid obesity [OR = 1.18 (CI 1.07-1.30)]. There was no significant difference between men and women in the prevalence of femoral hernia (men: 0.7/per10,000, women: 0.9/per10,000, p = 0.19). CONCLUSIONS: The relationship between hernia and obesity is complex with some hernias decreasing in prevalence as obesity increases. Further research is needed to better understand this paradoxical relationship
Efficient Photon Coupling from a Diamond Nitrogen Vacancy Centre by Integration with Silica Fibre
A central goal in quantum information science is to efficiently interface
photons with single optical modes for quantum networking and distributed
quantum computing. Here, we introduce and experimentally demonstrate a compact
and efficient method for the low-loss coupling of a solid-state qubit, the
nitrogen vacancy (NV) centre in diamond, with a single-mode optical fibre. In
this approach, single-mode tapered diamond waveguides containing exactly one
high quality NV memory are selected and integrated on tapered silica fibres.
Numerical optimization of an adiabatic coupler indicates that
near-unity-efficiency photon transfer is possible between the two modes.
Experimentally, we find an overall collection efficiency between 18-40 % and
observe a raw single photon count rate above 700 kHz. This integrated system
enables robust, alignment-free, and efficient interfacing of single-mode
optical fibres with single photon emitters and quantum memories in solids
Wren’s Walk-Off Bests No. 23 Clemson to Even the Series
Wren’s Walk-Off Bests No. 23 Clemson to Even the Series Junior right fielder hits a bases loaded single with two outs in the nint
An e-Business Logistic Model in Taiwan
The current article develops a framework for an e-business logistic model in Taiwan. The model includes e-marketplace, logistic, organization, and informational systems factors. Data used for this research come from a survey of business groups, including marine and air carriers, terminal warehousing, custom brokers, shipping centers, and marine information service providers. Our study reveals relationships between essential variables for e-business trading in the logistic industry. These include organizational advantage and information technology, strategy and vision, consumer-directed service and planning, lower cost and high quality customer service, quick merchandise delivery and low inventory, and long-term development plans. Specifically, we found that the logistic industry in Taiwan ignores the details of purchasing procedure in e-marketplace operation, focusing more on actual merchandise delivery, consumer satisfaction, and downstream consumer service. In addition, the logistical industry in Taiwan also involves employee adjustment to the new environment, support from upper management, training and, application of information technology
Rate of false conviction of criminal defendants who are sentenced to death
The rate of erroneous conviction of innocent criminal defendants is often described as not merely unknown but unknowable. There is no systematic method to determine the accuracy of a criminal conviction; if there were, these errors would not occur in the first place. As a result, very few false convictions are ever discovered, and those that are discovered are not representative of the group as a whole. In the United States, however, a high proportion of false convictions that do come to light and produce exonerations are concentrated among the tiny minority of cases in which defendants are sentenced to death. This makes it possible to use data on death row exonerations to estimate the overall rate of false conviction among death sentences. The high rate of exoneration among death-sentenced defendants appears to be driven by the threat of execution, but most death-sentenced defendants are removed from death row and resentenced to life imprisonment, after which the likelihood of exoneration drops sharply. We use survival analysis to model this effect. and estimate that if all death-sentenced defendants remained under sentence of death indefinitely, at least 4.1 % would be exonerated. We conclude that this is a conservative estimate of the proportion of false conviction among death sentences in the United States
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