743 research outputs found
Direct and Heterodyne Detection of Microwaves in a Metallic Single Wall Carbon Nanotube
This letter reports measurements of microwave (up to 4.5 GHz) detection in
metallic single-walled carbon nanotubes. The measured voltage responsivity was
found to be 114 V/W at 77K. We also demonstrated heterodyne detection at 1 GHz.
The detection mechanism can be explained based on standard microwave detector
theory and the nonlinearity of the DC IV-curve. We discuss the possible causes
of this nonlinearity. While the frequency response is limited by circuit
parasitics in this measurement, we discuss evidence that indicates that the
effect is much faster and that applications of carbon nanotubes as terahertz
detectors are feasible
Exploring the Use of Numerical Relativity Waveforms in Burst Analysis of Precessing Black Hole Mergers
Recent years have witnessed tremendous progress in numerical relativity and
an ever improving performance of ground-based interferometric gravitational
wave detectors. In preparation for Advanced LIGO and a new era in gravitational
wave astronomy, the numerical relativity and gravitational wave data analysis
communities are collaborating to ascertain the most useful role for numerical
relativity waveforms in the detection and characterization of binary black hole
coalescences. In this paper, we explore the detectability of equal mass,
merging black hole binaries with precessing spins and total mass M_T in
[80,350]Msol, using numerical relativity waveforms and template-less search
algorithms designed for gravitational wave bursts. In particular, we present a
systematic study using waveforms produced by the MAYAKRANC code that are added
to colored, Gaussian noise and analyzed with the Omega burst search algorithm.
Detection efficiency is weighed against the orientation of one of the
black-hole's spin axes. We find a strong correlation between the detection
efficiency and the radiated energy and angular momentum, and that the inclusion
of the l=2, m=+/-1,0 modes, at a minimum, is necessary to account for the full
dynamics of precessing systems.Comment: 9 pages, 15 figure
The Influence of Physical Education on Self-Efficacy in Overweight Schoolgirls: A 12-Week Training Program
The purpose of this randomized controlled study was to investigate the impact of a 12- week physical education (PE) program on the self-efficacy of overweight schoolgirls. We randomly assigned 60 overweight schoolgirls (15–17 years) to either an experimental moderate to vigorous aerobic exercise (∼90 min, three times a week) group (n = 30) or a control group (CG) (n = 30) that received non-specific regular PE lessons with activities chosen by the curricular teacher mainly focused on team games and sports skills that aimed to achieve general psycho-physical wellness (∼90 min, three times a week). To assess the starting level of students and significant changes reached, at baseline and after training, a battery of standardized assessment motor tests and a psychometric scale (generalized self-efficacy scale, GES) were administered. At the end of the intervention, the experimental group reported a considerable decrease in body mass index (BMI) and a large improvement in self-efficacy (p < 0.001). No significant changes were found in the CG. The results suggested that the 12-week moderate to a vigorous aerobic exercise program is an effective weight loss intervention and a vehicle to promote a range of outcomes important to the qualitative growth of adolescents. In fact, it could provide a positive and significant impact on the self-efficacy of overweight schoolgirls
The importance of lipidomic approach for mapping and exploring the molecular networks underlying physical exercise: A systematic review
Maintaining appropriate levels of physical exercise is an optimal way for keeping a good state of health. At the same time, optimal exercise performance necessitates an integrated organ system response. In this respect, physical exercise has numerous repercussions on metabolism and function of different organs and tissues by enhancing whole‐body metabolic homeostasis in response to different exercise‐related adaptations. Specifically, both prolonged and intensive physical exercise produce vast changes in multiple and different lipid‐related metabolites. Lipidomic technologies allow these changes and adaptations to be clarified, by using a biological system approach they provide scientific understanding of the effect of physical exercise on lipid trajectories. Therefore, this systematic review aims to indicate and clarify the identifying biology of the individual response to different exercise workloads, as well as provide direction for future studies focused on the body’s metabolome exercise‐related adaptations. It was performed using five databases (Medline (PubMed), Google Scholar, Embase, Web of Science, and Cochrane Library). Two author teams reviewed 105 abstracts for inclusion and at the end of the screening process 50 full texts were analyzed. Lastly, 14 research articles specifically focusing on metabolic responses to exercise in healthy subjects were included. The Oxford quality scoring system scale was used as a quality measure of the reviews. Information was extracted using the participants, intervention, comparison, outcomes (PICOS) format. Despite that fact that it is well‐known that lipids are involved in different sport‐related changes, it is unclear what types of lipids are involved. Therefore, we analyzed the characteristic lipid species in blood and skeletal muscle, as well as their alterations in response to chronic and acute exercise. Lipidomics analyses of the studies examined revealed medium‐ and long‐chain fatty acids, fatty acid oxidation products, and phospholipids qualitative changes. The main cumulative evidence indicates that both chronic and acute bouts of exercise determine significant changes in lipidomic profiles, but they manifested in very different ways depending on the type of tissue examined. Therefore, this systematic review may offer the possibility to fully understand the individual lipidomics exercise‐related response and could be especially important to improve athletic performance and human health
The role of parental involvement in youth sport experience: perceived and desired behavior by male soccer players
Parents play a key role in the youth sports educational experience. They are responsible for the introduction of their children to physical or sporting education and their involvement has been associated with sport participation in early stages. The aims of this cross-sectional study were, first, to assess the perceived and desired parental involvement by children and, secondly, to exam-ine their satisfaction or dissatisfaction with any specific behavior. 80 male soccer players filled the Parental Involvement in Sport Questionnaire (PISQ) before or after a training session in presence of a coach. PISQ results revealed excessive active involvement and pressure, insufficient praise and understanding and satisfactory directive behavior from children’s parents. Our findings suggest that excessive parental involvement can cause pressure on children who would prefer parental participation characterized by praise and understanding. A balance between a supporting involvement without putting too much pressure is needed by the parents. To prevent burnout and dropout and to facilitate future practice, parents should be counseled (possibly by a sport educator) on how to positively support their children concerning their sport experience
The graceful exit from the anomaly-induced inflation: Supersymmetry as a key
The stable version of the anomaly-induced inflation does not need a fine
tuning and leads to sufficient expansion of the Universe. The non-stable
version (Starobinsky model) provides the graceful exit to the FRW phase. We
indicate the possibility of the inflation which is stable at the beginning and
unstable at the end. The effect is due to the soft supersymmetry breaking and
the decoupling of the massive sparticles at low energy.Comment: 10 pages, 2 figures using axodraw. Modified version. Discussion
concerning the gravitational scale modified, the effect of massive particles
in the last stage of inflation taken into accoun
Complete phenomenological gravitational waveforms from spinning coalescing binaries
The quest for gravitational waves from coalescing binaries is customarily
performed by the LIGO-Virgo collaboration via matched filtering, which requires
a detailed knowledge of the signal. Complete analytical coalescence waveforms
are currently available only for the non-precessing binary systems. In this
paper we introduce complete phenomenological waveforms for the dominant
quadrupolar mode of generically spinning systems. These waveforms are
constructed by bridging the gap between the analytically known inspiral phase,
described by spin Taylor (T4) approximants in the restricted waveform
approximation, and the ring-down phase through a phenomenological intermediate
phase, calibrated by comparison with specific, numerically generated waveforms,
describing equal mass systems with dimension-less spin magnitudes equal to 0.6.
The overlap integral between numerical and phenomenological waveforms ranges
between 0.95 and 0.99.Comment: Proceeding for the GWDAW-14 conference. Added reference in v
Artificial intelligence for renal cancer: From imaging to histology and beyond
Artificial intelligence (AI) has made considerable progress within the last decade and is the subject of contemporary literature. This trend is driven by improved computational abilities and increasing amounts of complex data that allow for new approaches in analysis and interpretation. Renal cell carcinoma (RCC) has a rising incidence since most tumors are now detected at an earlier stage due to improved imaging. This creates considerable challenges as approximately 10%–17% of kidney tumors are designated as benign in histopathological evaluation; however, certain co-morbid populations (the obese and elderly) have an increased peri-interventional risk. AI offers an alternative solution by helping to optimize precision and guidance for diagnostic and therapeutic decisions. The narrative review introduced basic principles and provide a comprehensive overview of current AI techniques for RCC. Currently, AI applications can be found in any aspect of RCC management including diagnostics, perioperative care, pathology, and follow-up. Most commonly applied models include neural networks, random forest, support vector machines, and regression. However, for implementation in daily practice, health care providers need to develop a basic understanding and establish interdisciplinary collaborations in order to standardize datasets, define meaningful endpoints, and unify interpretation
Assessment of Body Composition and Physical Performance of Young Soccer Players: Differences According to the Competitive Level
Simple Summary In recent years, soccer teams require greater physical and technical-tactical capabilities from not to younger players, especially in elite team. Although dribble and kicking skills, strength, endurance, speed, and agility abilities are the most relevant features, it is not clear whether anthropometric and body composition aspects could be considered appropriate talent characteristics in soccer players. In addition, it rests unclear which are the principal differences, when they appear, and what metrics discriminate between elite and non-elite teams. The main aim of this study is to compare anthropometric, body composition and physical performance between and within four juvenile categories of two (elite and non-elite) soccer teams and investigates factors that better discriminate among two teams. Despite the physical performance results as the most relevant factor in discriminating among the two soccer societies, the elite players report better anthropometric and body characteristics, especially in the youngest categories. Soccer is a multifactorial sport, in which players are expected to possess well developed physical, psychological, technical, and tactical skills. Thus, the anthropometric and fitness measures play a determinant role and could vary according to the competitive level. Therefore, the present study aimed to verify differences in body composition and physical performance between two soccer team. 162 young soccer players (from the Under 12 to Under 15 age categories; age: 13.01 +/- 1.15 years) of different competitive levels (elite-n = 98 and non-elite-n = 64) were recruited. Anthropometric characteristics (height, weight, lengths, widths, circumferences, and skinfold thicknesses (SK)), bioelectrical impedance, physical performance test as countermovement jump (CMJ), 15 m straight-line sprints, Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo), and 20 + 20 m repeated-sprint ability (RSA)) were carried out. In addition, Body mass index (BMI), body composition parameters (percentage of fat mass (%F), Fat mass (FM, kg), and Fat-free mass (FFM, kg)) and the areas of the upper arm, calf and thigh were calculated, and the Bioelectric Impedance Vector Analysis (BIVA) procedures were applied. In addition, a linear discriminant analysis was assessed to determine which factors better discriminate between an elite and non-elite football team. Many differences were observed in body composition between and within each football team's category, especially in triceps SK (p < 0.05), %F (p < 0.05), and all performance tests (p < 0.01). The canonical correlation was 0.717 (F-(7,F-128) = 19.37, p < 0.0001), and the coefficients that better discriminated between two teams were 15 m sprint (-2.39), RSA (1-26), suprailiac SK (-0.5) and CMJ (-0.45). Elite soccer team players present a better body composition and greater physical efficiency. In addition, BIVA outcome could be a relevant selection criterion to scout among younger soccer players
Decoherence of electron spin qubits in Si-based quantum computers
Direct phonon spin-lattice relaxation of an electron qubit bound by a donor
impurity or quantum dot in SiGe heterostructures is investigated. The aim is to
evaluate the importance of decoherence from this mechanism in several important
solid-state quantum computer designs operating at low temperatures. We
calculate the relaxation rate as a function of [100] uniaxial strain,
temperature, magnetic field, and silicon/germanium content for Si:P bound
electrons. The quantum dot potential is much smoother, leading to smaller
splittings of the valley degeneracies. We have estimated these splittings in
order to obtain upper bounds for the relaxation rate. In general, we find that
the relaxation rate is strongly decreased by uniaxial compressive strain in a
SiGe-Si-SiGe quantum well, making this strain an important positive design
feature. Ge in high concentrations (particularly over 85%) increases the rate,
making Si-rich materials preferable. We conclude that SiGe bound electron
qubits must meet certain conditions to minimize decoherence but that
spin-phonon relaxation does not rule out the solid-state implementation of
error-tolerant quantum computing.Comment: 8 figures. To appear in PRB-July 2002. Revisions include: some
references added/corrected, several typos fixed, a few things clarified.
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