7,835 research outputs found
Quark Mass Ratios in ChPT with the Difference of Quark Condensates Considered
The chiral effective Lagrangian for pseudoscalar nonet is constructed in
consideration of isospin breaking. And the difference of quark condensates is
taken accounted. The SU(3) singlet eta0 is not taken as Goldstone-boson. The
mixing with and without isospin symmetry is considered. The quark mass ratios
are obtained through solving the mass equations of mesons. We estimate the
change of quark mass ratios according to the change of the masses of pion+ and
kaon+ to see how the electromagnetic corrections affect our results. It turn
out that massless up quark is possible. The upper limit for mu/md is around
0.39. 2ms/(mu+md)=24.23~25.12. The values for quark condensate ratios and other
constants are limited in narrow ranges.Comment: 10 page
Role of Particle Interactions in the Feshbach Conversion of Fermion Atoms to Bosonic Molecules
We investigate the Feshbach conversion of fermion atomic pairs to condensed
boson molecules with a microscopic model that accounts the repulsive
interactions among all the particles involved. We find that the conversion
efficiency is enhanced by the interaction between boson molecules while
suppressed by the interactions between fermion atoms and between atom and
molecule. In certain cases, the combined effect of these interactions leads to
a ceiling of less than 100% on the conversion efficiency even in the adiabatic
limit. Our model predicts a non-monotonic dependence of the efficiency on mean
atomic density. Our theory agrees well with recent experiments on Li and
K.Comment: 5 pages, 4 figure
A causational analysis of scholars' years of active academic careers vis-à-vis their academic productivity and academic influence
Taking the scholarly activities of 73 doctoral program mentors working at the Chinese Academy of Medical Sciences & Peking Union Medical College (the CAMS & PUMC) as a sample of our investigative survey, we tried using such statistical methods as the analysis of variance (ANOVA), factor analysis and correlation analysis to compare the different characteristics of scholarship assessment of Chinese medical scholars as exhibited in their published papers in domestic and foreign journals. Our research findings show that citations per paper and A-index are more suitable for assessing the highly accomplished senior Chinese medical professionals (e.g. academicians) for their domestic and international scholarship attainment. In contrast, the m-quotient is not deemed appropriate to assess their academic influence both at home and abroad. Upon our further analysis of 6 evaluative indicators, we noticed that these indicators might be applied in two different aspects: One is from the viewpoint of Chinese scholars' academic influence at home, which has been evaluated mainly from the perspective of "total" amount and "average" amount of both publications and citations. The other is from their academic impact embodied by the means of documents retrieved from the Web of Science, which is mainly assessed from the two viewpoints of publications and citations. It is suggested that the accumulated time-length of a given scholar's active engagement in professional practice in a specific subject area be taken into consideration while assessing a researcher's performance at home and abroad</p
Stem cell factor and granulocyte colony-stimulating factor reduce β-amyloid deposits in the brains of APP/PS1 transgenic mice
2-Amino-4,6-dimethylpyrimidine–benzoic acid (1/1)
The crystal of the title compound, C6H9N3·C7H6O2, contains tetrameric hydrogen-bonded units comprising a central pair of 2-aminopyrimidine molecules linked across a centre of inversion by N—H⋯N hydrogen bonds and two pendant benzoic acid molecules attached through N—H⋯O and O—H⋯N hydrogen bonds. These hydrogen-bonded units are arranged into layers in (002)
Quasinormal modes for asymptotic safe black holes
Under the hypothesis of asymptotic safety of gravity, the static, spherically
symmetric black hole solutions in the infrared limit are corrected by
non-perturbative effects. Specifically, the metric is modified by the running
of gravitational couplings. In this work, we investigate the effects of this
correction to the quasinormal modes (QNMs) of a test scalar field propagating
in this kind of black hole background analytically and numerically. It is found
that although the quasi-period frequencies and the damping of oscillations are
respectively enhanced and weakened by the quantum correction term, the
stability of the black hole remains.Comment: 11 pages, 1 figures, accepted for publication in CQG. arXiv admin
note: text overlap with arXiv:1007.131
A Note on Self-gravitating Radiation in AdS Spacetime
In this paper we investigate the equilibrium self-gravitating radiation in
higher dimensional, plane symmetric anti-de Sitter space. We find that there
exist essential differences from the spherically symmetric case: In each
dimension (), there are maximal mass (density), maximal entropy
(density) and maximal temperature configurations, they do not appear at the
same central energy density; the oscillation behavior appearing in the
spherically symmetric case, does not happen in this case; and the mass
(density), as a function of the central energy density, increases first and
reaches its maximum at a certain central energy density and then decreases
monotonically in , while in , besides the maximum, the
mass (density) of the equilibrium configuration has a minimum: the mass
(density) first increases and reaches its maximum, then decreases to its
minimum and then increases to its asymptotic value monotonically. The reason
causing the difference is discussed.Comment: Revtex, 13 pages with 8 eps figures, to appear in PRD; v2: typos
corrected and the version in PR
Extremum Seeking Control of Hybrid Ground Source Heat Pump System
The ground source heat pump (GSHP) technology is a renewable alternative for space conditioning by rejecting/absorbing heat to/from the ground, which has demonstrated higher energy efficiency for residential and commercial buildings. As the system capacity is limited by the initial cost of construction of ground-loop heat exchanger (GHE), developing the so-called Hybrid GSHP system by utilizing supplemental heat rejecters such as cooling towers has emerged as a cost-effective alternative. In practice, operational efficiency of Hybrid GSHP system mainly depends on 1) the actual characteristics of heat pump, cooling tower, GHE and other equipment; 2) ambient air and ground conditions. In particular, the GHE heat transfer is heavily affected by the ground thermal characteristics which, however, is difficult and expensive in practice to determine due to the complexity of soil type and distribution. In addition, the actual cooling tower characteristics can vary significantly. Such uncertainties bring forth dramatic difficulty for successful application of model based control or optimization methods. In this study, an extremum seeking control (ESC) strategy is proposed for efficient operation of a hybrid GSHP system with cooling tower, which minimizes the total power (i.e. GHE loop water pump, cooling tower fan and pump, and the heat-pump compressor) consumption by tuning the air-flow rate of the cooling tower fan and the GHE loop water flow rate. To evaluate the proposed control method, a Modelica based model of the Hybrid GSHP system is developed by utilizing the Buildings Library developed by the Lawrence Berkeley National Laboratory, which consists of a 20-borehole GHE, a water-to-water heat pump, a counter-flow cooling tower and a plate heat exchanger. The transient conduction model of vertical GHE in the Buildings Library is adopted, which is based on a finite-volume method inside the borehole and cylindrical source model outside the borehole. A variable-flow water pump model is constructed for the GHE water loop, which gives power consumption under different operating scenarios. A cooling tower model in the Buildings Library is adopted, which is a static polynomial model based on a York cooling tower correlation. The relative air flow rate can be regulated to maintain the leaving water temperature at the setpoint, and then the corresponding fan power consumption is obtained. The heat pump model is based on the evaporator temperature, condenser temperature and Carnot efficiency. An inner-loop proportional-integral (PI) controller is implemented to regulate the evaporator leaving water temperature at 7 deg-C. Under the air wet-bulb temperature of 35 deg-C and dry-bulb temperature 23 deg-C, steady-state simulation of the plant model yields the static map of the total power with respect to the cooling tower relative air flow rate and the GHE water flow rate, which indicates about 25% power variation across the adjustable range of inputs. Simulation was conducted in two conditions: change in evaporator inlet water temperature and change in ambient air condition. The simulation study under way is to validate the effectiveness of the proposed ESC strategy, and the potential for energy saving will also be evaluated
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