7,469 research outputs found
Field study on adaptive thermal comfort in typical air conditioned classrooms
This study investigates adaptive thermal comfort in air conditioned classrooms in Hong Kong. A field survey was conducted in several typical classrooms at the City University of Hong Kong. This survey covered objective measurement of thermal environment parameters and subjective human thermal responses. A total of 982 student volunteers participated in the investigation. The results indicate that students in light clothing (0.42 clo) have adapted to the cooler classroom environments. The neutral temperature is very close to the preferred temperature of approximately 24 °C. Based on the MTSV ranging between −0.5 and + 0.5, the comfort range is between 21.56 °C and 26.75 °C. The lower limit is below that of the ASHRAE standard. Of the predicted mean vote (PMV) and the University of California, Berkeley (UCB) model, the UCB model predictions agree better with the mean thermal sensation vote (MTSV). Also, the respective fit regression models of the MTSV versus each of the following: operative temperature (Top), PMV, and UCB were obtained. This study provides a better understanding of acceptable classroom temperatures
Quantum Impurities and the Neutron Resonance Peak in : Ni versus Zn
The influence of magnetic (S=1) and nonmagnetic (S=0) impurities on the spin
dynamics of an optimally doped high temperature superconductor is compared in
two samples with almost identical superconducting transition temperatures:
YBa(CuNi)O (T=80 K) and
YBa(CuZn)O (T=78 K). In the Ni-substituted
system, the magnetic resonance peak (which is observed at E40 meV in
the pure system) shifts to lower energy with a preserved E/T ratio
while the shift is much smaller upon Zn substitution. By contrast Zn, but not
Ni, restores significant spin fluctuations around 40 meV in the normal state.
These observations are discussed in the light of models proposed for the
magnetic resonance peak.Comment: 3 figures, submitted to PR
The scaling properties of exchange and correlation holes of the valence shell of second row atoms
We study the exchange and correlation hole of the valence shell of second row
atoms using variational Monte Carlo techniques, especially correlated
estimates, and norm-conserving pseudopotentials. The well-known scaling of the
valence shell provides a tool to probe the behavior of exchange and correlation
as a functional of the density and thus test models of density functional
theory. The exchange hole shows an interesting competition between two scaling
forms -- one caused by self-interaction and another that is approximately
invariant under particle number, related to the known invariance of exchange
under uniform scaling to high density and constant particle number. The
correlation hole shows a scaling trend that is marked by the finite size of the
atom relative to the radius of the hole. Both trends are well captured in the
main by the Perdew-Burke-Ernzerhof generalized-gradient approximation model for
the exchange-correlation hole and energy.Comment: 18 pages, 8 figure
Risk for development of active tuberculosis in patients with chronic airway disease-a systematic review of evidence.
Reports suggest an increased risk of tuberculosis (TB) in people with chronic airway diseases (CADs) such as chronic obstructive pulmonary disease (COPD), but evidence has not been systematically reviewed. We performed a systematic review by searching MEDLINE and Embase for studies published from 1 January 1993 to 15 January 2021 reporting the association between the incident risk of TB in people with CADs (asthma, COPD and bronchiectasis). Two reviewers independently assessed the quality of individual studies. We included nine studies, with two from low-income high TB burden countries. Three cohort studies reported a statistically significant independent association between COPD and the risk of TB in high-income countries (n=711 389). Hazard ratios for incident TB ranged from 1.44 to 3.14 adjusted for multiple confounders including age, sex and comorbidity. There was large between-study heterogeneity (I2=97.0%) across studies. The direction of effect on the TB risk from asthma was inconsistent. Chronic bronchitis or bronchiectasis studies were limited. The small number of available studies demonstrated an increased risk of TB in people with COPD; however, the magnitude of the increase varies by setting and population. Data in high TB burden countries and for other CADs are limited
Leptogenesis from Soft Supersymmetry Breaking (Soft Leptogenesis)
Soft leptogenesis is a scenario in which the cosmic baryon asymmetry is
produced from a lepton asymmetry generated in the decays of heavy sneutrinos
(the partners of the singlet neutrinos of the seesaw) and where the relevant
sources of CP violation are the complex phases of soft supersymmetry-breaking
terms. We explain the motivations for soft leptogenesis, and review its basic
ingredients: the different CP-violating contributions, the crucial role played
by thermal corrections, and the enhancement of the efficiency from lepton
flavour effects. We also discuss the high temperature regime GeV in
which the cosmic baryon asymmetry originates from an initial asymmetry of an
anomalous -charge, and soft leptogenesis reembodies in -genesis.Comment: References updated. Some minor corrections to match the published
versio
Magnetic Collective Mode Dispersion in High Temperature Superconductors
Recent neutron scattering experiments in the superconducting state of YBCO
have been interpreted in terms of a magnetic collective mode whose dispersion
relative to the commensurate wavevector has a curvature opposite in sign to a
conventional magnon dispersion. The purpose of this article is to demonstrate
that simple linear response calculations are in support of a collective mode
interpretation, and to explain why the dispersion has the curvature it does.Comment: 3 pages, revtex, 4 encapsulated postscript figure
Walk Your Life to Health—Motivating Young Adolescents to Engage in a Brisk Walking Program
Increasing numbers of overweight and obese children resulting from sedentary and abundant lifestyles are a health concern in Hong Kong and other affluent communities around the globe. The importance of physical activity is well documented for health and wellbeing, with sedentary behavior emerging as an independent risk factor for chronic diseases and mortality. In this study, Pender's Health-Promotion Model informed the development of an intervention program aimed to engage junior high school students in increased physical activity, specifically brisk-walking. The model set out to motivate participants to engage in behaviors to enhance their health across the life span, including developing self-efficacy with regard to brisk walking. The intervention featured four stages. First, participants were provided with information about the benefits and in stage two were trained in the technique of brisk walking. Next they engaged in the brisk walking program and in stage four were encouraged to serve as health ambassadors by introducing brisk walking and its associated benefits to others, thereby exercising peer influence to diffuse the practice of brisk walking more widely among members of the community. Motivational strategies were used as incentives in the program, including the involvement of a popular singing band to award certificates at the completion of the program. This 7-week intervention program including a 4-week brisk walking component was conducted in a high school context with 71 participants. Data were collected to enable paired-sample t-tests to be conducted to statistically analyze the data at pre- and post-intervention. Findings indicate significant differences among the mean Body Mass Index (BMI), Waist-to-Hip Ratio (WHR), knowledge and attitudes of the participants at pre- and post-intervention. These findings suggest that the intervention was effective as a strategy to reduce sedentary behavior with the concomitant effect of positive shifts in measurable indicators and attitudes.Full Tex
Synthesis and Cell Adhesive Properties of Linear and Cyclic RGD Functionalized Polynorbornene Thin Films
Described herein is the efficient synthesis and evaluation of bioactive arginine-glycine-aspartic acid (RGD) functionalized polynorbornene-based materials for cell adhesion and spreading. Polynorbornenes containing either linear or cyclic RGD peptides were synthesized by ring-opening metathesis polymerization (ROMP) using the well-defined ruthenium initiator [(H_(2)IMes)(pyr)_(2)(Cl)_(2)Ru═CHPh]. The random copolymerization of three separate norbornene monomers allowed for the incorporation of water-soluble polyethylene glycol (PEG) moieties, RGD cell recognition motifs, and primary amines for postpolymerization cross-linking. Following polymer synthesis, thin-film hydrogels were formed by cross-linking with bis(sulfosuccinimidyl) suberate (BS^3), and the ability of these materials to support human umbilical vein endothelial cell (HUVEC) adhesion and spreading was evaluated and quantified. When compared to control polymers containing either no peptide or a scrambled RDG peptide, polymers with linear or cyclic RGD at varying concentrations displayed excellent cell adhesive properties in both serum-supplemented and serum-free media. Polymers with cyclic RGD side chains maintained cell adhesion and exhibited comparable integrin binding at a 100-fold lower concentration than those carrying linear RGD peptides. The precise control of monomer incorporation enabled by ROMP allows for quantification of the impact of RGD structure and concentration on cell adhesion and spreading. The results presented here will serve to guide future efforts for the design of RGD functionalized materials with applications in surgery, tissue engineering, and regenerative medicine
A decidable policy language for history-based transaction monitoring
Online trading invariably involves dealings between strangers, so it is
important for one party to be able to judge objectively the trustworthiness of
the other. In such a setting, the decision to trust a user may sensibly be
based on that user's past behaviour. We introduce a specification language
based on linear temporal logic for expressing a policy for categorising the
behaviour patterns of a user depending on its transaction history. We also
present an algorithm for checking whether the transaction history obeys the
stated policy. To be useful in a real setting, such a language should allow one
to express realistic policies which may involve parameter quantification and
quantitative or statistical patterns. We introduce several extensions of linear
temporal logic to cater for such needs: a restricted form of universal and
existential quantification; arbitrary computable functions and relations in the
term language; and a "counting" quantifier for counting how many times a
formula holds in the past. We then show that model checking a transaction
history against a policy, which we call the history-based transaction
monitoring problem, is PSPACE-complete in the size of the policy formula and
the length of the history. The problem becomes decidable in polynomial time
when the policies are fixed. We also consider the problem of transaction
monitoring in the case where not all the parameters of actions are observable.
We formulate two such "partial observability" monitoring problems, and show
their decidability under certain restrictions
Spin dynamics in high- superconductors
Key features of antiferromagnetic dynamical correlations in high-
superconductors cuprates are discussed. In underdoped regime, the sharp
resonance peak, occuring exclusively in the SC state, is accompanied by a
broader contribution located around 30 meV which remains above .
Their interplay may induce incommensurate structure in the superconducting
state.Comment: HTS99 Proceedings Miami (January 7-11 1999
- …