Universality in chaotic quantum transport: The concordance between random matrix and semiclassical theories

Electronic transport through chaotic quantum dots exhibits universal, system independent, properties, consistent with random matrix theory. The quantum transport can also be rooted, via the semiclassical approximation, in sums over the classical scattering trajectories. Correlations between such trajectories can be organized diagrammatically and have been shown to yield universal answers for some observables. Here, we develop the general combinatorial treatment of the semiclassical diagrams, through a connection to factorizations of permutations. We show agreement between the semiclassical and random matrix approaches to the moments of the transmission eigenvalues. The result is valid for all moments to all orders of the expansion in inverse channel number for all three main symmetry classes (with and without time reversal symmetry and spin-orbit interaction) and extends to nonlinear statistics. This finally explains the applicability of random matrix theory to chaotic quantum transport in terms of the underlying dynamics as well as providing semiclassical access to the probability density of the transmission eigenvalues.Comment: Refereed version. 5 pages, 4 figure

The Far-Ultraviolet Spectra of TW Hya. II. Models of H2 Fluorescence in a Disk

We measure the temperature of warm gas at planet-forming radii in the disk around the classical T Tauri star (CTTS) TW Hya by modelling the H2 fluorescence observed in HST/STIS and FUSE spectra. Strong Ly-alpha emission irradiates a warm disk surface within 2 AU of the central star and pumps certain excited levels of H2. We simulate a 1D plane-parallel atmosphere to estimate fluxes for the 140 observed H2 emission lines and to reconstruct the Ly-alpha emission profile incident upon the warm H2. The excitation of H2 can be determined from relative line strengths by measuring self-absorption in lines with low-energy lower levels, or by reconstructing the Ly-alpha profile incident upon the warm H2 using the total flux from a single upper level and the opacity in the pumping transition. Based on those diagnostics, we estimate that the warm disk surface has a column density of log N(H2)=18.5^{+1.2}_{-0.8}, a temperature T=2500^{+700}_{-500} K, and a filling factor of H2, as seen by the source of Ly-alpha emission, of 0.25\pm0.08 (all 2-sigma error bars). TW Hya produces approximately 10^{-3} L_\odot in the FUV, about 85% of which is in the Ly-alpha emission line. From the H I absorption observed in the Ly-alpha emission, we infer that dust extinction in our line of sight to TW Hya is negligible.Comment: Accepted by ApJ. 26 pages, 17 figures, 6 table

The FUV spectrum of TW Hya. I. Observations of H2_2 Fluorescence

We observed the classical T Tauri star TW Hya with \textit{HST}/STIS using the E140M grating, from 1150--1700 \AA, with the E230M grating, from 2200--2900 \AA, and with \FUSE from 900--1180 \AA. Emission in 143 Lyman-band H$_2$ lines representing 19 progressions dominates the spectral region from 1250--1650 \AA. The total H$_2$ emission line flux is $1.94 \times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$, which corresponds to $1.90\times10^{-4}$ $L_\odot$ at TW Hya's distance of 56 pc. A broad stellar \Lya line photoexcites the H$_2$ from excited rovibrational levels of the ground electronic state to excited electronic states. The \ion{C}{2} 1335 \AA doublet, \ion{C}{3} 1175 \AA\ multiplet, and \ion{C}{4} 1550 \AA doublet also electronically excite H$_2$. The velocity shift of the H$_2$ lines is consistent with the photospheric radial velocity of TW Hya, and the emission is not spatially extended beyond the 0\farcs05 resolution of \textit{HST}. The H$_2$ lines have an intrinsic FWHM of $11.91\pm0.16$ \kms. One H$_2$ line is significantly weaker than predicted by this model because of \ion{C}{2} wind absorption. We also do not observe any H$_2$ absorption against the stellar \Lya profile. From these results, we conclude that the H$_2$ emission is more consistent with an origin in a disk rather than in an outflow or circumstellar shell. We also analyze the hot accretion-region lines (e.g., \ion{C}{4}, \ion{Si}{4}, \ion{O}{6}) of TW Hya, which are formed at the accretion shock, and discuss some reasons why Si lines appear significantly weaker than other TR region lines.Comment: accepted by ApJ, 42 pages -- 20 text, 11 figure

Characteristics of tropospheric ozone depletion events in the Arctic spring: analysis of the ARCTAS, ARCPAC, and ARCIONS measurements and satellite BrO observations

Arctic ozone depletion events (ODEs) are caused by halogen catalyzed ozone loss. In situ chemistry, advection of ozone-poor air mass, and vertical mixing in the lower troposphere are important factors affecting ODEs. To better characterize the ODEs, we analyze the combined set of surface, ozonesonde, and aircraft in situ measurements of ozone and bromine compounds during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS), the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC), and the Arctic Intensive Ozonesonde Network Study (ARCIONS) experiments (April 2008). Tropospheric BrO columns retrieved from satellite measurements and back trajectory calculations are also used to investigate the characteristics of observed ODEs. In situ observations from these field experiments are inadequate to validate tropospheric BrO columns derived from satellite measurements. In view of this difficulty, we construct an ensemble of tropospheric column BrO estimates from two satellite (OMI and GOME-2) measurements and with three independent methods of calculating stratospheric BrO columns. Furthermore, we select analysis methods that do not depend on the absolute magnitude of column BrO, such as time-lagged correlation analysis of ozone and tropospheric column BrO, to understand characteristics of ODEs. Time-lagged correlation analysis between in situ (surface and ozonesonde) measurements of ozone and satellite derived tropospheric BrO columns indicates that the ODEs are due to either local halogen-driven ozone loss or short-range (∼1 day) transport from nearby regions with ozone depletion. The effect of in situ ozone loss is also evident in the diurnal variation difference between low (10th and 25th percentiles) and higher percentiles of surface ozone concentrations at Alert, Canada. Aircraft observations indicate low-ozone air mass transported from adjacent high-BrO regions. Correlation analyses of ozone with potential temperature and time-lagged tropospheric BrO column show that the vertical extent of local ozone loss is surprisingly deep (1–2 km) at Resolute and Churchill, Canada. The unstable boundary layer during ODEs at Churchill could potentially provide a source of free-tropospheric BrO through convective transport and explain the significant negative correlation between free-tropospheric ozone and tropospheric BrO column at this site

Analysis of satellite-derived Arctic tropospheric BrO columns in conjunction with aircraft measurements during ARCTAS and ARCPAC

We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative transfer model and stratospheric column BrO from a photochemical simulation. We conduct a comprehensive comparison of satellite-derived tropospheric BrO column to aircraft in-situ observations of BrO and related species. The aircraft profiles reveal that tropospheric BrO, when present during April 2008, was distributed over a broad range of altitudes rather than being confined to the planetary boundary layer (PBL). Perturbations to the total column resulting from tropospheric BrO are the same magnitude as perturbations due to longitudinal variations in the stratospheric component, so proper accounting of the stratospheric signal is essential for accurate determination of satellite-derived tropospheric BrO. We find reasonably good agreement between satellite-derived tropospheric BrO and columns found using aircraft in-situ BrO profiles, particularly when satellite radiances were obtained over bright surfaces (albedo \u3e0.7), for solar zenith angl

An analysis of fast photochemistry over high northern latitudes during spring and summer using in-situ observations from ARCTAS and TOPSE

Observations of chemical constituents and meteorological quantities obtained during the two Arctic phases of the airborne campaign ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) are analyzed using an observationally constrained steady state box model. Measurements of OH and HO2 from the Penn State ATHOS instrument are compared to model predictions. Forty percent of OH measurements below 2 km are at the limit of detection during the spring phase (ARCTAS-A). While the median observed-to-calculated ratio is near one, both the scatter of observations and the model uncertainty for OH are at the magnitude of ambient values. During the summer phase (ARCTAS-B), model predictions of OH are biased low relative to observations and demonstrate a high sensitivity to the level of uncertainty in NO observations. Predictions of HO2 using observed CH2O and H2O2 as model constraints are up to a factor of two larger than observed. A temperature-dependent terminal loss rate of HO2 to aerosol recently proposed in the literature is shown to be insufficient to reconcile these differences. A comparison of ARCTAS-A to the high latitude springtime portion of the 2000 TOPSE campaign (Tropospheric Ozone Production about the Spring Equinox) shows similar meteorological and chemical environments with the exception of peroxides; observations of H2O2 during ARCTAS-A were 2.5 to 3 times larger than those during TOPSE. The cause of this difference in peroxides remains unresolved and has important implications for the Arctic HOx budget. Unconstrained model predictions for both phases indicate photochemistry alone is unable to simultaneously sustain observed levels of CH2O and H2O2; however when the model is constrained with observed CH2O, H2O2 predictions from a range of rainout parameterizations bracket its observations. A mechanism suitable to explain observed concentrations of CH2O is uncertain. Free tropospheric observations of acetaldehyde (CH3CHO) are 2–3 times larger than its predictions, though constraint of the model to those observations is sufficient to account for less than half of the deficit in predicted CH2O. The box model calculates gross O3 formation during spring to maximize from 1–4 km at 0.8 ppbv d−1, in agreement with estimates from TOPSE, and a gross production of 2–4 ppbv d−1 in the boundary layer and upper troposphere during summer. Use of the lower observed levels of HO2 in place of model predictions decreases the gross production by 25–50%. Net O3 production is near zero throughout the ARCTAS-A troposphere, and is 1–2 ppbv in the boundary layer and upper altitudes during ARCTAS-B

COMT and MAO-A Polymorphisms and Obsessive-Compulsive Disorder: A Family-Based Association Study

ObjectiveObsessive-compulsive disorder (OCD) is a common and debilitating psychiatric illness. Although a genetic component contributes to its etiology, no single gene or mechanism has been identified to the OCD susceptibility. the catechol-O-methyltransferase (COMT) and monoamine oxidase A (MAO-A) genes have been investigated in previous OCD studies, but the results are still unclear. More recently, Taylor (2013) in a comprehensive meta-analysis of genetic association studies has identified COMT and MAO-A polymorphisms involved with OCD. in an effort to clarify the role of these two genes in OCD vulnerability, a family-based association investigation was performed as an alternative strategy to the classical case-control design.MethodsTransmission disequilibrium analyses were performed after genotyping 13 single-nucleotide polymorphisms (eight in COMT and five in MAO-A) in 783 OCD trios (probands and their parents). Four different OCD phenotypes (from narrow to broad OCD definitions) and a SNP x SNP epistasis were also analyzed.ResultsOCD, broad and narrow phenotypes, were not associated with any of the investigated COMT and MAO-A polymorphisms. in addition, the analyses of gene-gene interaction did not show significant epistatic influences on phenotype between COMT and MAO-A.ConclusionsThe findings do not support an association between DSM-IV OCD and the variants of COMT or MAO-A. However, results from this study cannot exclude the contribution of these genes in the manifestation of OCD. the evaluation of broader spectrum phenotypes could help to understand the role of these and other genes in the pathophysiology of OCD and its spectrum disorders.Brazilian governmental agenciesConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundo de Aprimoramento Academico (FUAA-Grant for Academic Improvement)Department of Psychiatry University of São Paulo School of MedicineUniv São Paulo, Fac Med, Dept & Inst Psychiat, São Paulo, SP, BrazilUniv Fed Bahia, Serv Med Univ, Salvador, BA, BrazilUniv Pernambuco, Fac Ciencias Med, Recife, PE, BrazilUniversidade Federal de São Paulo, São Paulo, SP, BrazilBritish Columbia Mental Hlth & Addict Res Inst, Vancouver, BC, CanadaMassachusetts Gen Hosp, PNGU, Boston, MA 02114 USAMassachusetts Gen Hosp, Ctr Human Genet Res, Boston, MA 02114 USAUniv Calif San Francisco, Dept Psychiat, San Francisco, CA USAHosp Sick Children, Program Genet & Genome Biol, Toronto, ON M5G 1X8, CanadaUniv Michigan, Dept Psychiat, Ann Arbor, MI 48109 USASunnybrook Hlth Sci Ctr, Frederick W Thompson Anxiety Disorders Ctr, Toronto, ON M4N 3M5, CanadaUniv Toronto, Ctr Addict & Mental Hlth, Toronto, ON, CanadaUniv Fed Rio de Janeiro, Inst Psiquiatria, IPUB, Programa Ansiedade & Depressao, Rio de Janeiro, BrazilUniv São Paulo, Inst Math & Stat, Dept Stat, São Paulo, SP, BrazilUniversidade Federal de São Paulo, São Paulo, SP, BrazilCNPq: 573974/2008-0FAPESP: 2005/55628-08FAPESP: 2008/57896-8Web of Scienc

Bullets over ballots: Islamist groups, the state and electoral violence in Egypt and Morocco

This article is concerned with state-sponsored electoral violence in liberalized autocracies. The first section of the paper identifies a number of variables that can help explain the decision calculus of authoritarian incumbents to deploy force against strong electoral challengers. The second section then examines these propositions with reference to Egypt and Morocco. Drawing on recent parliamentary elections in both countries the article questions why, despite facing the challenge of political Islam, the two regimes differed so markedly in their willingness to manipulate the polls by recourse to violence. Whilst the Egyptian authorities decided to abrogate all pretence of peaceful elections in favour of violent repression against the Muslim Brotherhood candidates and sympathizers, no such tactics were deployed by the ruling elite in Morocco. We suggest that three principal factors influenced the regimes' response to this electoral challenge: (1) the centrality of the elected institution to authoritarian survival; (2) the availability of alternative electioneering tools; and (3) the anticipated response of the international community. The article concludes by suggesting that in order to understand better when and how states deploy violence in elections, we need to focus on a more complex set of factors rather than simply on the electoral potency of key opposition challengers or the authoritarian nature of the state

phot1 inhibition of ABCB19 primes lateral auxin fluxes in the shoot apex required for phototropism

It is well accepted that lateral redistribution of the phytohormone auxin underlies the bending of plant organs towards light. In monocots, photoreception occurs at the shoot tip above the region of differential growth. Despite more than a century of research, it is still unresolved how light regulates auxin distribution and where this occurs in dicots. Here, we establish a system in Arabidopsis thaliana to study hypocotyl phototropism in the absence of developmental events associated with seedling photomorphogenesis. We show that auxin redistribution to the epidermal sites of action occurs at and above the hypocotyl apex, not at the elongation zone. Within this region, we identify the auxin efflux transporter ATP-BINDING CASSETTE B19 (ABCB19) as a substrate target for the photoreceptor kinase PHOTOTROPIN 1 (phot1). Heterologous expression and physiological analyses indicate that phosphorylation of ABCB19 by phot1 inhibits its efflux activity, thereby increasing auxin levels in and above the hypocotyl apex to halt vertical growth and prime lateral fluxes that are subsequently channeled to the elongation zone by PIN-FORMED 3 (PIN3). Together, these results provide new insights into the roles of ABCB19 and PIN3 in establishing phototropic curvatures and demonstrate that the proximity of light perception and differential phototropic growth is conserved in angiosperm

Global surveillance of oral tobacco products : total nicotine, unionised nicotine and tobacco-specific N-nitrosamines

OBJECTIVE: Oral tobacco products contain nicotine and carcinogenic tobacco-specific N-nitrosamines (TSNAs) that can be absorbed through the oral mucosa. The aim of this study was to determine typical pH ranges and concentrations of total nicotine, unionised nicotine (the most readily absorbed form) and five TSNAs in selected oral tobacco products distributed globally. METHODS: A total of 53 oral tobacco products from 5 World Health Organisation (WHO) regions were analysed for total nicotine and TSNAs, including 4-(methylnitrosamino)- 1-(3-pyridyl)-1-butanol (NNAL), using gas chromatography or liquid chromatography with mass spectrometric detection. Unionised nicotine concentrations were calculated using product pH and total nicotine concentrations. Fourier transform infrared spectroscopy was used to help categorise or characterise some products. RESULTS: Total nicotine content varied from 0.16 to 34.1 mg/g product, whereas, the calculated unionised nicotine ranged from 0.05 to 31.0 mg/g product; a 620-fold range of variation. Products ranged from pH 5.2 to 10.1, which translates to 0.2% to 99.1% of nicotine being in the unionised form. Some products have very high pH and correspondingly high unionised nicotine (eg, gul powder, chimo´, toombak) and/or high TSNA (eg, toombak, zarda, khaini) concentrations. The concentrations of TSNAs spanned five orders of magnitude with concentrations of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) ranging from 4.5 to 516 000 ng/g product. CONCLUSIONS: These data have important implications for risk assessment because they show that very different exposure risks may be posed through the use of these chemically diverse oral tobacco products. Because of the wide chemical variation, oral tobacco products should not be categorised together when considering the public health implications of their use.This work was funded by the U.S. Government, Department of Health and Human Services. This study was also funded internally at the Centers for Disease Control and Prevention, with funds directly provided by the U.S. federal government.http://tobaccocontrol.bmj.com