Thermodynamics of relativistic quantum fields confined in cavities

We investigate the quantum thermodynamical properties of localised relativistic quantum fields, and how they can be used as quantum thermal machines. We study the efficiency and power of energy transfer between the classical gravitational degrees of freedom, such as the energy input due to the motion of boundaries or an impinging gravitational wave, and the excitations of a confined quantum field. We find that the efficiency of energy transfer depends dramatically on the input initial state of the system. Furthermore, we investigate the ability of the system to extract energy from a gravitational wave and store it in a battery. This process is inefficient in optical cavities but is significantly enhanced when employing trapped Bose Einstein condensates. We also employ standard fluctuation results to obtain the work probability distribution, which allows us to understand how the efficiency is related to the dissipation of work. Finally, we apply our techniques to a setup where an impinging gravitational wave excites the phononic modes of a Bose Einstein condensate. We find that, in this case, the percentage of energy transferred to the phonons approaches unity after a suitable amount of time. These results give a quantitative insight into the thermodynamic behaviour of relativistic quantum fields confined in cavities.Comment: 35 pages, 3 figures. Manuscript substantially updated. I. Fuentes also published as I. Fuentes-Guridi and I. Fuentes-Schulle

Uniform Silicon Isotope Ratios Across the Milky Way Galaxy

We report the relative abundances of the three stable isotopes of silicon, $^{28}$Si, $^{29}$Si and $^{30}$Si, across the Galaxy using the $v = 0, J = 1 \to 0$ transition of silicon monoxide. The chosen sources represent a range in Galactocentric radii ($R_{\rm GC}$) from 0 to 9.8 kpc. The high spectral resolution and sensitivity afforded by the GBT permit isotope ratios to be corrected for optical depths. The optical-depth-corrected data indicate that the secondary-to-primary silicon isotope ratios $^{29}{\rm Si}/^{28}{\rm Si}$ and $^{30}{\rm Si}/^{28}{\rm Si}$ vary much less than predicted on the basis of other stable isotope ratio gradients across the Galaxy. Indeed, there is no detectable variation in Si isotope ratios with $R_{\rm GC}$. This lack of an isotope ratio gradient stands in stark contrast to the monotonically decreasing trend with $R_{\rm GC}$ exhibited by published secondary-to-primary oxygen isotope ratios. These results, when considered in the context of the expectations for chemical evolution, suggest that the reported oxygen isotope ratio trends, and perhaps that for carbon as well, require further investigation. The methods developed in this study for SiO isotopologue ratio measurements are equally applicable to Galactic oxygen, carbon and nitrogen isotope ratio measurements, and should prove useful for future observations of these isotope systems.Comment: 18 pages, 12 figures, 2 tables. Published in The Astrophysical Journal, Volume 839, Issue

Copernicus Downstream Service Supports Nature-Based Flood Defense: Use of Sentinel Earth Observation Satellites for Coastal Needs

This is a copy of the article published in Sea-Technology Magazine, which the authors have bought the rights to redistribute.With an uncertain future that includes climate change, sea level rise and increasing coastal populations, being able to make informed policy decisions in coastal zones will be critical for ensuring the well-being of citizens, the environment and the sustainability of economic activities. Earth observation (EO) can be used to efficiently and systematically provide the key information needed to make these decisions. However, getting access to the right EO in- formation can be a complicated and costly business, limiting availability. However, the launch in April 2014 of the first Sentinel satellite from Europe’s flagship EO program, Copernicus, represents a major advance in the availability of EO data, which has great potential to benefit numerous sectors involved in marine and coastal activities. We discuss some examples of applications being developed and give an example of a new service which intends to support nature-based flood defense schemes.The research leading to these results has received funding from the European Union Seventh Framework Program (FP7/2007-2013) under grant agreement n° 607131. All views presented are those of the authors. The EU is not liable for any use that may be made of the information contained herein.PDF, 5 pages, 20.4 M

Comparing Distance-Based Vs. Time-Based Exercise Prescriptions Of Walking And Running For Improvement Of Cardiovascular Disease Risk Factors

The many benefits of participation in a regular physical activity program are well-documented (Haskell et al., 2007; Pate et al., 1995). Brisk walking and jogging are commodes of exercise that is easily measured and evaluated by a self-report method that is comin both clinical and research settings. Some research has suggested that walking for distance as opposed to walking for time may be a stronger predictor of overall amount of accumulated exercise or physical activity (Williams, 2012a). To our knowledge, research has not been conducted directly comparing a distance-based versus time-based brisk walking prescription for the improvement of cardiovascular risk factors. The primary purpose of this study was to compare walking/running for distance to walking/running for time as part of a weight loss intervention to assess similarities or differences. Another purpose was to evaluate included the feasibility of a previously published regression equation in predicting energy expenditure for walking or running for a one-mile distance before and after exercise weight loss intervention. This study folloa between-subjects, repeated measures design with each participant reporting for pre-intervention as well as post-intervention testing. Twenty-one overweight, but otherwise healthy participants [10 for distance-based (dist) group, 11 for time-based (time) group] were recruited but only 15 participants completed the study (9 time, 6 dist). Informed consent was obtained from the participants who fit the inclusion criteria based on the physical activity readiness questionnaire and body composition measurements using dxa. Participants were required to complete four testing sessions at the beginning of intervention and three testing sessions at the completion of intervention. Each testing session was separated by 24 hours. The time intervention group walked and ran for self-reported exercise time completed per day, and accumulated per week. The dist intervention group walked and ran for self-reported exercise distance completed per day, and accumulated per week. Each participant was measured for the following postabsorptive variables: lipid panel which included (total cholesterol, low-density lipoprotein, high-density lipoprotein, and triglycerides), glucose, resting metabolic rate (rmr). Body composition, vo2 max, measured kcal/mile and predicted kcal/mile were also measured before and following intervention. A mixed-factor repeated- measures anova (rm-anova) was used to compare all cardiovascular disease risk-related dependent variables before and after intervention (body weight, body composition, blood lipids & glucose, rmr, vo2 max) for within-subjects and between-subjects comparisons. A mixed-factor repeated-measures anova was also used to compare weekly adherence rates to the exercise program. If interactions occurred, they were folloup with a sidak adjustment for multiple pairwise comparisons. Overall, the groups adhered to the exercise programs at similar rates. Significant interactions were shown for mean body weight loss between groups as well as mean blood glucose level (p \u3c 0.05). The dist group lost an average of 4.0 kg while the time group gained an average of 1.1 kg. The dist group exhibited a decline in their blood glucose level by an average of 10.5 mg/dl while the time group shoan increase in their blood glucose level by an average of 4.7 mg/dl. Additionally, running one-mile was significantly more expensive metabolically than walking the mile at both pre- and post-intervention. Also, excess post-exercise oxygen consumption was significantly greater in the five minutes following running compared to walking. To the best of the author\u27s knowledge, the present study is the first to directly compare a distance-based vs. A time-based exercise program for walking and running for improvement of risk factors of cvd. The results of the particular study would suggest that a distance-based exercise prescription of walking or running should provide a clinician or researcher with a closer estimation of overall ee and resultantly weight loss and reduction of particular risk factors for cvd

Cross-Validation Of A Recently Published Equation Predicting Energy Expenditure To Run Or Walk A Mile In Normal Weight And Overweight Adults

An equation recently published by Loftin, et al. (2010) was cross-validated using 30 subjects consisting of 10 normal weight walkers, 10 overweight walkers, and 10 distance runners. Gender was balanced across sub-groups. Participants walked or ran for 5 minutes at their preferred pace. Preferred walking pace was determined by six timed 50-ft trials and preferred running pace by the runner\u27s typical training pace. Energy expenditure (EE) was determined via indirect calorimetry and reported in absolute units (kcal), and corrected to a mile distance. Body composition was assessed via DXA. EE per mile was predicted using the Loftin, et al. (2010) equation. The equation [Kcal = mass (kg) x 0.789 ? gender (men=1, women=2) x 7.634 + 51.109; R2 = 0.632, SEE = 10.9 kcal/mile] yielded a mean of 99.7 ± 10.9 kcal/mile which was significantly different (p \u3c 0.05) than the measured mean of the cross-validation group (107.8 ± 15.5 kcal/mile). However, the mean was within the standard error of the estimate of the original equation. Further analysis included a Chow test which yielded no significant differences between regression coefficients of the original equation and the cross-validation (CV) group [Kcal = mass (kg) x 0.825 ? gender (men=1, women=2) x 1.687 + 47.6; R2 = 0.625, SEE = 9.82 kcal/mile] equation. Also, absolute EE per mile for the CV group was similar across sub-groups. It appears the Loftin, et al. regression equation is useful for exercise prescription in that it allows for the prediction of EE for either walking or running a mile in normal weight and overweight adults