577 research outputs found
Transforming U.S. Particle Physics Education: A Snowmass 2021 Study
The pursuit of knowledge in particle physics requires constant learning. As
new tools become available, new theories are developed, and physicists search
for new answers with ever-evolving methods. However, it is the case that formal
educational systems serve as the primary training grounds for particle
physicists. Graduate school (and undergraduate school to a lesser extent) is
where researchers learn most of the technical skills required for research,
develop scientific problem-solving abilities, learn how to establish themselves
in their field, and begin developing their career. It is unfortunate, then,
that the skills gained by physicists during their formal education are often
mismatched with the skills actually required for a successful career in
physics. We performed a survey of the U.S. particle physics community to
determine the missing elements of graduate and undergraduate education and to
gauge how to bridge these gaps. In this contributed paper, part of the 2021-22
Snowmass Community Planning Exercise, we report the results of this survey. We
also recommend several specific community actions to improve the quality of
particle physics education; the "community" here refers to physics departments,
national labs, professional societies, funding agencies, and individual
physicists.Comment: contribution to Snowmass 202
Correction and verification of x-ray imaging crystal spectrometer analysis on Wendelstein 7-X through x-ray ray tracing
Observation of off-diagonal geometric phase in polarized neutron interferometer experiments
Off-diagonal geometric phases acquired in the evolution of a spin-1/2 system
have been investigated by means of a polarized neutron interferometer. Final
counts with and without polarization analysis enable us to observe
simultaneously the off-diagonal and diagonal geometric phases in two detectors.
We have quantitatively measured the off-diagonal geometric phase for noncyclic
evolutions, confirming the theoretical predictions. We discuss the significance
of our experiment in terms of geometric phases (both diagonal and off-diagonal)
and in terms of the quantum erasing phenomenon.Comment: pdf, 22 pages + 8 figures (included in the pdf). In print on Phys.
Rev.
Taxonomic synopsis and analytical key for the genera of Solanaceae from Rio Grande do Sul, Brazil
Recommended from our members
New Benchmarks from Tokamak Experiments for Theoretical Calculations of the Dielectronic Satellite Spectra of Helium-like Ions
Dielectronic satellite spectra of helium-like argon, recorded with a high-resolution X-ray crystal spectrometer at the National Spherical Torus Experiment, were found to be inconsistent with existing predictions resulting in unacceptable values for the power balance and suggesting the unlikely existence of non-Maxwellian electron energy distributions. These problems were resolved with calculations from a new atomic code. It is now possible to perform reliable electron temperature measurements and to eliminate the uncertainties associated with determinations of non-Maxwellian distributions
A study of the breakdown of the quasi-static approximation at high densities and its effect on the helium-like K ALPHA complex of nickel, iron, and calcium
The General Spectral Modeling (GSM) code employs the quasi-static
approximation, a standard, low-density methodology that assumes the ionization
balance is separable from a determination of the excited-state populations that
give rise to the spectra. GSM also allows for some states to be treated only as
contributions to effective rates. While these two approximations are known to
be valid at low densities, this work investigates using such methods to model
high-density, non-LTE emission spectra and determines at what point the
approximations break down by comparing to spectra produced by the LANL code
ATOMIC which makes no such approximations. As both approximations are used by
other astrophysical and low-density modeling codes, the results should be of
broad interest. He-like K emission spectra are presented for Ni, Fe,
and Ca, in order to gauge the effect of both approximations employed in GSM.
This work confirms that at and above the temperature of maximum abundance of
the He-like ionization stage, the range of validity for both approximations is
sufficient for modeling the low- and moderate-density regimes one typically
finds in astrophysical and magnetically confined fusion plasmas. However, a
breakdown does occur for high densities; we obtain quantitative limits that are
significantly higher than previous works. This work demonstrates that, while
the range of validity for both approximations is sufficient to predict the
density-dependent quenching of the z line, the approximations break down at
higher densities. Thus these approximations should be used with greater care
when modeling high-density plasmas such as those found in inertial confinement
fusion and electromagnetic pinch devices.Comment: Accepted by Physical Review A (http://pra.aps.org/). 11 pages + LANL
cover, 5 figures. Will update citation information as it becomes available.
Abbreviated abstract is listed her
Sleep-disordered breathing-do we have to change gears in heart failure?
The majority of patients with heart failure have sleep-disordered breathing (SDB)-with central (rather than obstructive) sleep apnoea becoming the predominant form in those with more severe disease. Cyclical apnoeas and hypopnoeas are associated with sleep disturbance, hypoxaemia, haemodynamic changes, and sympathetic activation. Such patients have a worse prognosis than those without SDB. Mask-based therapies of positive airway pressure targeted at SDB can improve measures of sleep quality and partially normalise the sleep and respiratory physiology, but recent randomised trials of cardiovascular outcomes in central sleep apnoea have been neutral or suggested the possibility of harm, likely from increased sudden death. Further randomised outcome studies (with cardiovascular mortality and hospitalisation endpoints) are required to determine whether mask-based treatment for SDB is appropriate for patients with chronic systolic heart failure and obstructive sleep apnoea, for those with heart failure with preserved ejection fraction, and for those with decompensated heart failure. New therapies for sleep apnoea-such as implantable phrenic nerve stimulators-also require robust assessment. No longer can the surrogate endpoints of improvement in respiratory and sleep metrics be taken as adequate therapeutic outcome measures in patients with heart failure and sleep apnoea
Adaptive servoventilation improves cardiac function and respiratory stability
Cheyne–Stokes respiration (CSR) in patients with chronic heart failure (CHF) is of major prognostic impact and expresses respiratory instability. Other parameters are daytime pCO2, VE/VCO2-slope during exercise, exertional oscillatory ventilation (EOV), and increased sensitivity of central CO2 receptors. Adaptive servoventilation (ASV) was introduced to specifically treat CSR in CHF. Aim of this study was to investigate ASV effects on CSR, cardiac function, and respiratory stability. A total of 105 patients with CHF (NYHA ≥ II, left ventricular ejection fraction (EF) ≤ 40%) and CSR (apnoea–hypopnoea index ≥ 15/h) met inclusion criteria. According to adherence to ASV treatment (follow-up of 6.7 ± 3.2 months) this group was divided into controls (rejection of ASV treatment or usage <50% of nights possible and/or <4 h/night; n = 59) and ASV (n = 56) adhered patients. In the ASV group, ventilator therapy was able to effectively treat CSR. In contrast to controls, NYHA class, EF, oxygen uptake, 6-min walking distance, and NT-proBNP improved significantly. Moreover, exclusively in these patients pCO2, VE/VCO2-slope during exercise, EOV, and central CO2 receptor sensitivity improved. In CHF patients with CSR, ASV might be able to improve parameters of SDB, cardiac function, and respiratory stability
Evolution of Fe Species During the Synthesis of Over-Exchanged Fe/ZSM5 Obtained by Chemical Vapor Deposition of FeCl3
Abstract The evolution of iron in over-exchanged Fe/ZSM5 prepared via chemical vapor deposition of FeCl 3 was studied at each stage of the synthesis. Different characterization techniques (EXAFS, HR-XANES
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