Thomas-Fermi-Dirac-von Weizsacker hydrodynamics in laterally modulated electronic systems

We have studied the collective plasma excitations of a two-dimensional electron gas with an arbitrary lateral charge-density modulation. The dynamics is formulated using a previously developed hydrodynamic theory based on the Thomas-Fermi-Dirac-von Weizsacker approximation. In this approach, both the equilibrium and dynamical properties of the periodically modulated electron gas are treated in a consistent fashion. We pay particular attention to the evolution of the collective excitations as the system undergoes the transition from the ideal two-dimensional limit to the highly-localized one-dimensional limit. We also calculate the power absorption in the long-wavelength limit to illustrate the effect of the modulation on the modes probed by far-infrared (FIR) transmission spectroscopy.Comment: 27 page Revtex file, 15 Postscript figure

Tolerance to bronchodilating effects of salmeterol in COPD

AbstractLoss of bronchodilator effectiveness or tolerance has been observed with inhaled beta-agonists but not with inhaled anticholinergic medications. Initially, tolerance is reflected in loss of bronchial protection against stimuli followed by loss of bronchodilator properties. However, generally such observations have been reported in asthma. A 6-month randomized, double-dummy placebo-controlled trial comparing tiotropium to salmeterol provided the opportunity to examine spirometric tolerance to long-acting beta-agonists in patients with COPD. Spirometry was measured over 12h at baseline and at days 15, 57, 116 and 169. Changes over time from baseline were compared relative to changes observed with placebo. A total of 623 patients participated (tiotropium=209, salmeterol=213, placebo=201). The groups were similar in age (mean=65 years), gender (75% men), and baseline FEV1 (mean=1.08±0.37l [40±12% predicted]). Relative to placebo, both active drugs improved morning pre-drug, peak and average FEV1 and FVC throughout the trial. However, from day 1 to 169, salmeterol was associated with a higher decline in average FEV1 and FVC (0–12h) (difference from placebo: −36 and −115ml, PPP1 (−12ml) were observed with salmeterol. Tiotropium was associated with further improvements in spirometry from days 1 to 15 and no evidence of tolerance from day 15 to the end of the trial. In conclusion, tolerance to pharmacologic bronchodilation occurs with long-acting beta-agonists such as salmeterol and not with inhaled anticholinergics

Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV

We report the results of a study of color coherence effects in ppbar collisions based on data collected by the D0 detector during the 1994-1995 run of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8 TeV. Initial-to-final state color interference effects are studied by examining particle distribution patterns in events with a W boson and at least one jet. The data are compared to Monte Carlo simulations with different color coherence implementations and to an analytic modified-leading-logarithm perturbative calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters

Educational attainment of same-sex and opposite-sex dizygotic twins : An individual-level pooled study of 19 twin cohorts

Comparing twins from same- and opposite-sex pairs can provide information on potential sex differences in a variety of outcomes, including socioeconomic-related outcomes such as educational attainment. It has been suggested that this design can be applied to examine the putative role of intrauterine exposure to testosterone for educational attainment, but the evidence is still disputed. Thus, we established an international database of twin data from 11 countries with 88,290 individual dizygotic twins born over 100 years and tested for differences between twins from same- and opposite-sex dizygotic pairs in educational attainment. Effect sizes with 95% confidence intervals (CI) were estimated by linear regression models after adjusting for birth year and twin study cohort. In contrast to the hypothesis, no difference was found in women (β = −0.05 educational years, 95% CI −0.11, 0.02). However, men with a same-sex co-twin were slightly more educated than men having an opposite-sex co-twin (β = 0.14 educational years, 95% CI 0.07, 0.21). No consistent differences in effect sizes were found between individual twin study cohorts representing Europe, the USA, and Australia or over the cohorts born during the 20th century, during which period the sex differences in education reversed favoring women in the latest birth cohorts. Further, no interaction was found with maternal or paternal education. Our results contradict the hypothesis that there would be differences in the intrauterine testosterone levels between same-sex and opposite-sex female twins affecting education. Our findings in men may point to social dynamics within same-sex twin pairs that may benefit men in their educational careers.Peer reviewe

Consensus parameter: research methodologies to evaluate neurodevelopmental effects of pubertal suppression in transgender youth

An international interdisciplinary team of experts achieved consensus around primary methods and domains for assessing neurodevelopmental effects (i.e., benefits and/or difficulties) of pubertal suppression treatment in transgender youth.Pathways through Adolescenc

Search for electroweak production of single top quarks in ppˉp\bar{p} collisions.

We present a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector between 1992 and 1995. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb. (arXiv