2,498 research outputs found
Electron-phonon heat transfer in monolayer and bilayer graphene
We calculate the heat transfer between electrons to acoustic and optical
phonons in monolayer and bilayer graphene (MLG and BLG) within the
quasiequilibrium approximation. For acoustic phonons, we show how the
temperature-power laws of the electron-phonon heat current for BLG differ from
those previously derived for MLG and note that the high-temperature
(neutral-regime) power laws for MLG and BLG are also different, with a weaker
dependence on the electronic temperature in the latter. In the general case we
evaluate the heat current numerically. We suggest that a measurement of the
heat current could be used for an experimental determination of the
electron-acoustic phonon coupling constants, which are not accurately known.
However, in a typical experiment heat dissipation by electrons at very low
temperatures is dominated by diffusion, and we estimate the crossover
temperature at which acoustic-phonon coupling takes over in a sample with Joule
heating. At even higher temperatures optical phonons begin to dominate. We
study some examples of potentially relevant types of optical modes, including
in particular the intrinsic in-plane modes, and additionally the remote surface
phonons of a possible dielectric substrate.Comment: 13 pages, 8 figures; moved details to appendixes, added discussion of
remote phonon
Delivered With Care. A National Survey of Women's Experience of Maternity Care 2010
As maternity services change and the population of women and families served also
changes, there is a need to document the views of women with recent experience of care.
Maternity services are evolving and the information from this study provides a picture of
current practice and point of comparison for the future. This survey was carried out in 2010
and used similar methods to those employed in 1995 and 2006. A random sample of 10,000
women giving birth in England over a two week period were selected by the Office for
National Statistics from birth registration records. Women whose babies had died and new
mothers less than 16 years of age were excluded. The usable response rate was 54%, with
5,333 women participating. A total of 14% of respondents came from Black and Minority
Ethnic (BME) groups and 21% had been born outside the UK. An online version of the
questionnaire was made available to all survey participants; only 8% of those responding
used this method of return.
Data were analysed and are presented by parity, with some specific univariate analyses in
relation to clinical factors such as mode of delivery and demographic factors, such as
maternal age or geographical region. Some comparisons are made with previous surveys.
Multivariate analyses, with adjustment for potential confounders, were carried out in relation
to 20 selected outcomes contributing to quality of care
Measuring non-Gaussian fluctuations through incoherent Cooper pair current
We study a Josephson junction (JJ) in the regime of incoherent Cooper pair
tunneling, capacitively coupled to a nonequilibrium noise source. The
current-voltage (I-V) characteristics of the JJ are sensitive to the excess
voltage fluctuations in the source, and can thus be used for wide-band noise
detection. Under weak driving, the odd part of the I-V can be related to the
second cumulant of noise, whereas the even part is due to the third cumulant.
After calibration, one can measure the Fano factors for the noise source, and
get information about the frequency dependence of the noise.Comment: 4 pages, 4 figure
Microwave response of an NS ring coupled to a superconducting resonator
A long phase coherent normal (N) wire between superconductors (S) is
characterized by a dense phase dependent Andreev spectrum . We probe this
spectrum in a high frequency phase biased configuration, by coupling an NS ring
to a multimode superconducting resonator. We detect a dc flux and frequency
dependent response whose dissipative and non dissipative components are related
by a simple Debye relaxation law with a characteristic time of the order of the
diffusion time through the N part of the ring. The flux dependence exhibits
periodic oscillations with a large harmonics content at temperatures
where the Josephson current is purely sinusoidal. This is explained considering
that the populations of the Andreev levels are frozen on the time-scale of the
experiments.Comment: 5 pages,4 figure
Storage stability of rapeseed methyl ester stored in a sealed barrel for seven years
Received: March, 31st, 2021 ; Accepted: April, 24th, 2021 ; Published: November 15th, 2021 ; Correspondence: [email protected] stability is one of the main quality parameters related to fatty acid methyl esters
(FAME) biofuels. The deterioration of biofuels´ properties during storage is a more serious issue
than with conventional fuels. In particular, lengthy storage threatens the oxidative stability of
FAME fuels because factors such as the presence of air, elevated temperatures or presence of
metals promote the oxidation process. Consequently, the acceptable storage time for FAME fuels
is generally regarded to be regrettably short, at no more than six to12 months. However, storage
conditions play an important role in determining actual storage stability. This study aimed to
investigate and evaluate any deterioration in the quality of rapeseed methyl ester (RME) fuel that
has been stored for as long as seven years in adequate storage conditions. The fuel was stored in
the dark, contained in a sealed steel barrel in an insulated shipping container outdoors. The
temperature of the container varied with seasonal fluctuation, but the fuel never froze during
storage. The study analysed six key fuel properties of the RME: ester content; water content;
density; kinematic viscosity; oxidation stability index; and acid number. The analyses were
conducted immediately after opening the barrel, and again after two months of storage in a
laboratory. The results were compared to those measured for the fresh fuel, seven years earlier.
The comparison of the results indicate that the fuel quality had suffered no serious deterioration
during the seven-year period
Energy relaxation in graphene and its measurement with supercurrent
We study inelastic energy relaxation in graphene for low energies to find out
how electrons scatter with acoustic phonons and other electrons. By coupling
the graphene to superconductors, we create a strong dependence of the measured
signal, i.e.,\ critical Josephson current, on the electron population on
different energy states. Since the relative population of high- and low-energy
states is determined by the inelastic scattering processes, the critical
current becomes an effective probe for their strength. We argue that the
electron-electron interaction is the dominant relaxation method and, in our
model of two-dimensional electron-electron scattering, we find a scattering
time ps at T=500 mK, 1-2 orders of magnitude smaller than
predicted by theory.Comment: 10 pages, 13 figures submitted to Physical Review
Associations of tissue transglutaminase antibody seropositivity with coronary heart disease: Findings from a prospective cohort study.
Clinical experience and observational studies suggest that individuals with coeliac disease are at increased risk of coronary heart disease (CHD), but the precise mechanism for this is unclear. Laboratory studies suggest that it may relate to tissue transglutaminase antibodies (tTGAs). Our aim was to examine whether seropositivity for tTGA and endomysial antibodies (EMAs) are associated with incident CHD in humans.
We used data from Mini-Finland Health Survey, a prospective cohort study of Finnish men and women aged 35-80 at study baseline 1978-80. TTGA and EMA seropositivities were ascertained from baseline blood samples and incident CHD events were identified from national hospitalisation and death registers. Cox regression was used to examine the associations between antibody seropositivity and incident CHD. Of 6887 men and women, 562 were seropositive for tTGAs and 72 for EMAs. During a median follow-up of 26 years, 2367 individuals experienced a CHD event. We found no clear evidence for an association between tTGA positivity (hazard ratio, HR: 1.04, 95% confidence interval, CI: 0.83, 1.30) or EMA positivity (HR: 1.16, 95% CI: 0.77, 1.74) and incident CHD, once pre-existing CVD and known CHD risk factors had been adjusted for.
We found no clear evidence for an association of tTGA or EMA seropositivity with incident CHD outcomes, suggesting that tTG autoimmunity is unlikely to be the biological link between coeliac disease and CHD
Comparing eye tracking technologies
Abstract. Eye tracking is a technology that monitors eye movements, and by the data, detects gaze directions and target points. The number of potential use cases and capabilities of such technology are huge, and at the time being, there are at least five commercial VR headsets with built-in eye tracking systems. The aim of this study is to compare the performance of eye tracking technologies with two devices. We compare the eye tracking glasses from SeeTrue Technologies against Varjo Aero’s eye tracking system and evaluate, would it be worthwhile to place SeeTrue’s eye tracking technology into university’s headsets, which have no eye tracking capabilities at all, or is it better to use Varjo’s device, whenever eye tracking is needed. Motivated by previous research, we built a physical setup for SeeTrue device and virtual setup for Varjo device, in which the participant is directed to look at a white target dot shown on the black screen. We decided to use a moving target dot and a target dot, which changes its position on the screen, but stays at one place for two seconds. From the scripts that control the target dot position, actual positions of the targets were collected and compared with the gaze target positions that were received by the eye tracking devices. In our study, we used accuracy and precision as measures of performance. According to the results of this study, Varjo performed better, and the results stand for using Varjo’s device when eye tracking is needed, instead of placing SeeTrue’s system into headsets, which have no eye tracking capabilities. However, both devices were easy to use and highly capable of eye tracking. We recorded the results of mean error in visual angle within five degrees on both devices, and even with the moving target. This study, along with the other studies in the field, gives an idea and methodologies to one kind of performance testing of eye tracking devices
Nutrition Knowledge Is Associated with Energy Availability and Carbohydrate Intake in Young Female Cross-Country Skiers
The aim of this study was to provide information on energy availability (EA), macronutrient intake, nutritional periodization practices, and nutrition knowledge in young female cross-country skiers. A total of 19 skiers filled in weighted food and training logs before and during a training camp. Nutrition knowledge was assessed via a validated questionnaire. EA was optimal in 11% of athletes at home (mean 33.7 ± 9.6 kcal·kgFFM−1·d−1) and in 42% at camp (mean 40.3 ± 17.3 kcal·kgFFM−1·d−1). Most athletes (74%) failed to meet recommendations for carbohydrate intake at home (mean 5.0 ± 1.2 g·kg−1·d−1) and 63% failed to do so at camp (mean 7.1 ± 1.6 g·kg−1·d−1). The lower threshold of the pre-exercise carbohydrate recommendations was met by 58% and 89% of athletes while percentages were 26% and 89% within 1 h after exercise, at home and at camp, respectively. None of the athletes met the recommendations within 4 h after exercise. Nutrition knowledge was associated with EA at home (r = 0.52, p = 0.023), and with daily carbohydrate intake at home (r = 0.62, p = 0.005) and at camp (r = 0.52, p = 0.023). Carbohydrate intake within 1 and 4 h post-exercise at home was associated with better nutrition knowledge (r = 0.65, p = 0.003; r = 0.53, p = 0.019, respectively). In conclusion, young female cross-county skiers had difficulties meeting recommendations for optimal EA and carbohydrate intake. Better nutrition knowledge may help young athletes to meet these recommendations
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