329 research outputs found
Transition state theory for wave packet dynamics. I. Thermal decay in metastable Schr\"odinger systems
We demonstrate the application of transition state theory to wave packet
dynamics in metastable Schr\"odinger systems which are approached by means of a
variational ansatz for the wave function and whose dynamics is described within
the framework of a time-dependent variational principle. The application of
classical transition state theory, which requires knowledge of a classical
Hamilton function, is made possible by mapping the variational parameters to
classical phase space coordinates and constructing an appropriate Hamiltonian
in action variables. This mapping, which is performed by a normal form
expansion of the equations of motion and an additional adaptation to the energy
functional, as well as the requirements to the variational ansatz are discussed
in detail. The applicability of the procedure is demonstrated for a cubic model
potential for which we calculate thermal decay rates of a frozen Gaussian wave
function. The decay rate obtained with a narrow trial wave function agrees
perfectly with the results using the classical normal form of the corresponding
point particle. The results with a broader trial wave function go even beyond
the classical approach, i.e., they agree with those using the quantum normal
form. The method presented here will be applied to Bose-Einstein condensates in
the following paper [A. Junginger, M. Dorwarth, J. Main, and G. Wunner,
submitted to J. Phys. A].Comment: 21 pages, 3 figures, submitted to J. Phys.
Non-perturbative Interband Response of InSb Driven Off-resonantly by Few-cycle Electromagnetic Transients
Intense multi-THz pulses are used to study the coherent nonlinear response of
bulk InSb by means of field-resolved four-wave mixing spectroscopy. At
amplitudes above 5 MV/cm the signals show a clear temporal substructure which
is unexpected in perturbative nonlinear optics. Simulations based on a
two-level quantum system demonstrate that in spite of the strongly off-resonant
character of the excitation the high-field pulses drive the interband
resonances into a non-perturbative regime of Rabi flopping.Comment: 4 pages, 4 figure
Assessment of Involuntary PFM Contractions in Comparison with Existing Literature and IUGA/ICS Terminology Reports.
INTRODUCTION AND HYPOTHESIS
Involuntary pelvic floor muscle (PFM) contractions are thought to occur during an increase in intra-abdominal pressure (IAP). Although no studies have assessed their presence in women with normal pelvic floor (PF) function, existing literature links the absence of involuntary PFM contractions to various PF dysfunctions. This study rectifies this lacuna by evaluating involuntary PFM contractions during IAP in healthy nulliparous women with no PF dysfunction, using visual observation and vaginal palpation. Results were compared with the literature and the IUGA/ICS Terminology Reports.
METHODS
Nulliparous (n=149) women performed three sets of three maximal coughs. Visual observation and vaginal palpation were conducted in the standing and supine positions. The women were not instructed to contract their PFMs. Occurrence rates were calculated for each assessment method and position; differences between positions were analyzed using the Chi-squared test.
RESULTS
Rates of occurrence of involuntary PFM contraction were low across both assessments and positions (5-17%). Significant differences were found between standing (5%) and supine (15%) positions for visual observation, but not vaginal palpation (15%, 17% respectively). Occurrence rates also differed compared with the literature and terminology reports.
CONCLUSIONS
Contrary to clinical expectations, rates of occurrence of involuntary PFM contraction among our cohort of nulliparous women were extremely low. Digital palpation results showed high agreement with the terminology reports, but only partial agreement was observed for the visual observation results. Our study underscores the need for more research aimed at defining normal involuntary PF functions, a review of our understanding of involuntary PFM contractions, and better standardized guidelines for involuntary PFM assessment methods
Current and future technical, economic and environmental feasibility of maize and wheat residues supply for biomass energy application:Illustrated for South Africa
AbstractThis study assessed the feasibility of mobilising maize and wheat residues for large-scale bioenergy applications in South Africa by establishing sustainable residue removal rates and cost of supply based on different production regions. A key objective was to refine the methodology for estimating crop residue harvesting for bioenergy use, while maintaining soil productivity and avoiding displacement of competing residue uses. At current conditions, the sustainable bioenergy potential from maize and wheat residues was estimated to be about 104 PJ. There is potential to increase the amount of crop residues to 238 PJ through measures such as no till cultivation and adopting improved cropping systems. These estimates were based on minimum residues requirements of 2 t ha−1 for soil erosion control and additional residue amounts to maintain 2% SOC level.At the farm gate, crop residues cost between 0.9 and 1.7 GJ−1. In the improved scenario, up to 85% of the biomass is below 1.3 GJ−1 while in the optimised scenario, about 87% is delivered below 5$ GJ−1. Co-firing residues with coal results in lower cost of electricity compared to other renewables and significant GHG (CO2 eq) emissions reduction (up to 0.72 tons MWh−1). Establishing sustainable crop residue supply systems in South Africa could start by utilising the existing agricultural infrastructure to secure supply and develop a functional market. It would then be necessary to incentivise improvements across the value chain
Devices for SRF material characterization
The surface resistance R s of superconducting materials can be obtained by measuring the quality factor of an elliptical cavity excited in a transverse magnetic mode (TM010). The value obtained has however to be taken as averaged over the whole surface. A more convenient way to obtain R s, especially of materials which are not yet technologically ready for cavity production, is to measure small samples instead. These can be easily manufactured at low cost, duplicated and placed in film deposition and surface analytical tools. A commonly used design for a device to measure R s consists of a cylindrical cavity excited in a transverse electric (TE110) mode with the sample under test serving as one replaceable endplate. Such a cavity has two drawbacks. For reasonably small samples the resonant frequency will be larger than frequencies of interest concerning SRF application and it requires a reference sample of known R s. In this article we review several devices which have been designed to overcome these limitations, reaching sub-nΩ resolution in some cases. Some of these devices also comprise a parameter space in frequency and temperature which is inaccessible to standard cavity tests, making them ideal tools to test theoretical surface resistance models
Coaxial multi-mode cavities for fundamental SRF research in an unprecedented parameter space
Recent developments in superconducting radio-frequency (SRF) research have
focused primarily on high frequency elliptical cavities for electron
accelerators. Advances have been made in both reducing RF surface resistance
and pushing the readily achievable accelerating gradient by using novel SRF
cavity treatments including surface processing, custom heat treatments, and
flux expulsion. Despite the global demand for SRF based hadron accelerators,
the advancement of TEM mode cavities has lagged behind. To address this, two
purpose-built research cavities, one quarter-wave and one half-wave resonator,
have been designed and built to allow characterization of TEM-mode cavities
with standard and novel surface treatments. The cavities are intended as the
TEM mode equivalent to the 1.3GHz single cell cavity, which is the essential
tool for high frequency cavity research. Given their coaxial structure, the
cavities allow testing at the fundamental mode and higher harmonics, giving
unique insight into the role of RF frequency on fundamental loss mechanisms
from intrinsic and extrinsic sources. In this paper, the cavities and testing
infrastructure are described and the first performance measurements of both
cavities are presented
Global energy transfer during a magnetospheric field line resonance
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95367/1/grl28194.pd
Biowaiver monographs for immediate release solid oral dosage forms: prednisolone.
Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of immediate release (IR) solid oral dosage forms containing prednisolone are reviewed. Data on its solubility, oral absorption, and permeability are not totally conclusive, but strongly suggest a BCS Class 1 classification. Prednisolone's therapeutic indications and therapeutic index, pharmacokinetics, and the possibility of excipient interactions were also taken into consideration. Available evidence indicates that a biowaiver for IR solid oral dosage forms formulated with the excipients tabulated in this article would be unlikely to expose patients to undue risks
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