5,848 research outputs found
Electronic transport coefficients from ab initio simulations and application to dense liquid hydrogen
Using Kubo's linear response theory, we derive expressions for the
frequency-dependent electrical conductivity (Kubo-Greenwood formula),
thermopower, and thermal conductivity in a strongly correlated electron system.
These are evaluated within ab initio molecular dynamics simulations in order to
study the thermoelectric transport coefficients in dense liquid hydrogen,
especially near the nonmetal-to-metal transition region. We also observe
significant deviations from the widely used Wiedemann-Franz law which is
strictly valid only for degenerate systems and give an estimate for its valid
scope of application towards lower densities
Mouse models for studying prostate cancer bone metastasis.
Once tumor cells metastasize to the bone, the prognosis for prostate cancer patients is generally very poor. The mechanisms involved in bone metastasis, however, remain elusive, because of lack of relevant animal models. In this manuscript, we describe step-by-step protocols for the xenograft mouse models that are currently used for studying prostate cancer bone metastasis. The different routes of tumor inoculation (intraosseous, intracardiac, intravenous and orthotopic) presented are useful for exploring the biology of bone metastasis
Hydrodynamic object recognition using pressure sensing
Hydrodynamic sensing is instrumental to fish and some amphibians. It also represents, for underwater vehicles, an alternative way of sensing the fluid environment when visual and acoustic sensing are limited. To assess the effectiveness of hydrodynamic sensing and gain insight into its capabilities and limitations, we investigated the forward and inverse problem of detection and identification, using the hydrodynamic pressure in the neighbourhood, of a stationary obstacle described using a general shape representation. Based on conformal mapping and a general normalization procedure, our obstacle representation accounts for all specific features of progressive perceptual hydrodynamic imaging reported experimentally. Size, location and shape are encoded separately. The shape representation rests upon an asymptotic series which embodies the progressive character of hydrodynamic imaging through pressure sensing. A dynamic filtering method is used to invert noisy nonlinear pressure signals for the shape parameters. The results highlight the dependence of the sensitivity of hydrodynamic sensing not only on the relative distance to the disturbance but also its bearing
Evaluating Preference and Rate of Gambling on Vedio Slot Machines
Casinos increasingly are providing access to five-reel video slot machines and as a result are decreasing the use of traditional three-reel slot machines. Limited research has been conducted on the characteristics of play associated with video slot machines. The present study examined participant’s play on a five-reel video slot machine, comparing the number of trials played while wagering one credit on five lines versus five credits on one line. After participants were exposed to both conditions they were asked to choose their preferred condition. The results found that participants played significantly more trials while playing during the five credits on one line setting. The results also found that 12 out of 16 participants selected to play on the five lines on one credit setting when given the option to choose the settings of the slot machine
Excitonic condensate and quasiparticle transport in electron-hole bilayer systems
Bilayer electron-hole systems undergo excitonic condensation when the
distance d between the layers is smaller than the typical distance between
particles within a layer. All excitons in this condensate have a fixed dipole
moment which points perpendicular to the layers, and therefore this condensate
of dipoles couples to external electromagnetic fields. We study the transport
properties of this dipolar condensate system based on a phenomenological model
which takes into account contributions from the condensate and quasiparticles.
We discuss, in particular, the drag and counterflow transport, in-plane
Josephson effect, and noise in the in-plane currents in the condensate state
which provides a direct measure of the superfluid collective-mode velocity.Comment: 7 pages, 3 figure
Deterministic Partial Differential Equation Model for Dose Calculation in Electron Radiotherapy
Treatment with high energy ionizing radiation is one of the main methods in
modern cancer therapy that is in clinical use. During the last decades, two
main approaches to dose calculation were used, Monte Carlo simulations and
semi-empirical models based on Fermi-Eyges theory. A third way to dose
calculation has only recently attracted attention in the medical physics
community. This approach is based on the deterministic kinetic equations of
radiative transfer. Starting from these, we derive a macroscopic partial
differential equation model for electron transport in tissue. This model
involves an angular closure in the phase space. It is exact for the
free-streaming and the isotropic regime. We solve it numerically by a newly
developed HLLC scheme based on [BerCharDub], that exactly preserves key
properties of the analytical solution on the discrete level. Several numerical
results for test cases from the medical physics literature are presented.Comment: 20 pages, 7 figure
Inertial sensing with quantum gases: a comparative performance study of condensed versus thermal sources for atom interferometry
Abstract: Quantum sensors based on light pulse atom interferometers allow for measurements of inertial and electromagnetic forces such as the accurate determination of fundamental constants as the fine structure constant or testing foundational laws of modern physics as the equivalence principle. These schemes unfold their full performance when large interrogation times and/or large momentum transfer can be implemented. In this article, we demonstrate how interferometry can benefit from the use of Bose–Einstein condensed sources when the state of the art is challenged. We contrast systematic and statistical effects induced by Bose–Einstein condensed sources with thermal sources in three exemplary science cases of Earth- and space-based sensors. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s)
Use of Cell Phone Diaries to Understand Risk Contexts of Sexual Events Among Female Sex Workers
Background Data collection using mobile technologies, such as cell phones, allows more frequent and real-time data collection and is less prone to recall bias. We describe the feasibility of using twice daily cell phone diaries to capture contextual features of STI/HIV-risk that could impact disease acquisition among female sex workers (FSW).
Methods Women engaging in transactional sex in the prior 90 days were recruited utilising incentivized snowball sampling. Participants completed STI testing and baseline/exit surveys. Over 4-weeks, they completed twice-daily electronic diaries assessing event-level sexual behaviour, condom use, and drug use. Weekly in-person interviews used open-ended questions to explore geographical characteristics of sexual encounter locations as well as acceptability of event-level monitoring.
Results 25/26 participants (median age 43.5 years) completed the 4-week study. At baseline, 27% tested positive for a STI. Participants completed 84.5% of 1,518 expected surveys and 95% of 106 expected interviews. Patterns of diary compliance were stable over time. Partnered sexual activity was captured in 21.4% of diaries. At the participant-level, most reported giving oral sex (84.7%) or vaginal sex (96.1%); fewer (19.2%) reported engaging in anal sex. Among women reporting partnered sexual behaviour with any partner type (i.e., new/regular customers, romantic partners), using condoms was reported 39.2%, 45.5% and 83.3% of the time for giving oral sex, vaginal sex, and anal sex respectively. At the event-level, the frequency of giving oral sex, vaginal sex or anal sex did not significantly change over time.
Conclusions It is feasible to engage and retain FSW in a technologically-advanced study to characterise risk contexts of sexual events. Adherence to study protocol was high indicating event-level monitoring using cell phone based diaries is acceptable. These data can be utilised to improve our understanding of the individual, relational and environmental factors that influence STI/HIV acquisition among FSW
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