Semileptonic B and Lambda_b Decays and Local Duality in QCD

The inclusive and exclusive semileptonic decay distributions for b -> c decay are computed in the Shifman-Voloshin limit. The inclusive decay distributions (computed using an operator product expansion) depend on quark masses, and the exclusive decay distributions depend on hadron masses. Nevertheless, we show explicitly how the first two terms in the 1/m expansion match between the inclusive and exclusive decays. Agreement between the inclusive and exclusive decay rates requires a minimum smearing region of size Lambda_QCD before local duality holds in QCD. The alpha_s corrections to the inclusive and exclusive decay rates are also shown to agree to order (log m)/m^2. The alpha_s/m^2 corrections are used to obtain the alpha_s correction to Bjorken's inequality on the slope of the Isgur-Wise function.Comment: 22 pages, 3 eps figures, uses revtex (Revision: a discussion of radiative corrections to the bound K>0 of Section 7.B has been added; some typos, including labels in fig 2

Final Results From the Circumarctic Lakes Observation Network (CALON) Project

Since 2012, the physical and biogeochemical properties of ~60 lakes in northern Alaska have been investigated under CALON, a project to document landscape-scale variability of Arctic lakes in permafrost terrain. The network has ten nodes along two latitudinal transects extending inland 200 km from the Arctic Ocean. A meteorological station is deployed at each node and six representative lakes instrumented and continuously monitored, with winter and summer visits for synoptic assessment of lake conditions. Over the 4-year period, winter and summer climatology varied to create a rich range of lake responses over a short period. For example, winter 2012-13 was very cold with a thin snowpack producing thick ice across the region. Subsequent years had relatively warm winters, yet regionally variable snow resulted in differing gradients of ice thickness. Ice-out timing was unusually late in 2014 and unusually early in 2015. Lakes are typically well–mixed and largely isothermal, with minor thermal stratification occurring in deeper lakes during calm, sunny periods in summer. Lake water temperature records and morphometric data were used to estimate the ground thermal condition beneath 28 lakes. Application of a thermal equilibrium steady-state model suggests a talik penetrating the permafrost under many larger lakes, but lake geochemical data do not indicate a significant contribution of subpermafrost groundwater. Biogeochemical data reveal distinct spatial and seasonal variability in chlorophyll biomass, chromophoric dissolved organic carbon (CDOM), and major cations/anions. Generally, waters sampled beneath ice in April had distinctly higher concentrations of inorganic solutes and methane compared with August. Chlorophyll concentrations and CDOM absorption were higher in April, suggesting significant biological/biogeochemical activity under lake ice. Lakes are a positive source of methane in summer, and some also emit nitrous oxide and carbon dioxide. As part of the Indigenous Knowledge component,76 Iñupiat elders, hunters and berry pickers have been interviewed and over 75 hours of videotaped interviews produced. The video library and searchable interview logs are archived with the North Slope community. All field data is archived at ACADIS, and further information is at www.arcticlakes.org

Scarred Patterns in Surface Waves

Surface wave patterns are investigated experimentally in a system geometry that has become a paradigm of quantum chaos: the stadium billiard. Linear waves in bounded geometries for which classical ray trajectories are chaotic are known to give rise to scarred patterns. Here, we utilize parametrically forced surface waves (Faraday waves), which become progressively nonlinear beyond the wave instability threshold, to investigate the subtle interplay between boundaries and nonlinearity. Only a subset (three main types) of the computed linear modes of the stadium are observed in a systematic scan. These correspond to modes in which the wave amplitudes are strongly enhanced along paths corresponding to certain periodic ray orbits. Many other modes are found to be suppressed, in general agreement with a prediction by Agam and Altshuler based on boundary dissipation and the Lyapunov exponent of the associated orbit. Spatially asymmetric or disordered (but time-independent) patterns are also found even near onset. As the driving acceleration is increased, the time-independent scarred patterns persist, but in some cases transitions between modes are noted. The onset of spatiotemporal chaos at higher forcing amplitude often involves a nonperiodic oscillation between spatially ordered and disordered states. We characterize this phenomenon using the concept of pattern entropy. The rate of change of the patterns is found to be reduced as the state passes temporarily near the ordered configurations of lower entropy. We also report complex but highly symmetric (time-independent) patterns far above onset in the regime that is normally chaotic.Comment: 9 pages, 10 figures (low resolution gif files). Updated and added references and text. For high resolution images: http://physics.clarku.edu/~akudrolli/stadium.htm

Thallium isotopes reveal protracted anoxia during the Toarcian (Early Jurassic) associated with volcanism, carbon burial, and mass extinction

For this study, we generated thallium (Tl) isotope records from two anoxic basins to track the earliest changes in global bottom water oxygen contents over the Toarcian Oceanic Anoxic Event (TOAE; ∼183 Ma) of the Early Jurassic. The T-OAE, like other Mesozoic OAEs, has been interpreted as an expansion of marine oxygen depletion based on indirect methods such as organic-rich facies, carbon isotope excursions, and biological turnover. Our Tl isotope data, however, reveal explicit evidence for earlier global marine deoxygenation of ocean water, some 600 ka before the classically defined T-OAE. This antecedent deoxygenation occurs at the Pliensbachian/Toarcian boundary and is coeval with the onset of initial large igneous province (LIP) volcanism and the initiation of a marine mass extinction. Thallium isotopes are also perturbed during the T-OAE interval, as defined by carbon isotopes, reflecting a second deoxygenation event that coincides with the acme of elevated marine mass extinctions and the main phase of LIP volcanism. This suggests that the duration of widespread anoxic bottom waters was at least 1 million years in duration and spanned early to middle Toarcian time. Thus, the Tl data reveal a more nuanced record of marine oxygen depletion and its links to biological change during a period of climatic warming in Earth’s past and highlight the role of oxygen depletion on past biological evolution

Synthesis and structure of [CeF4(Me2SO)2]—A rare neutral ligand complex of a lanthanide tetrafluoride

Hydrated cerium(IV) fluoride dissolves in hot dimethylsulfoxide to form yellow [CeF4(Me2SO)2], the X-ray structure of which reveals a chain polymer with eight-coordinate cerium bound to two terminal and four bridging fluorines and two O-bonded Me2SO molecules. The complex was also characterised by IR, 1H and 19F{1H} NMR and UV/visible spectroscopies. Attempts to use [CeF4(Me2SO)2] as a synthon to prepare other complexes with phosphine oxides or 2,2?-bipyridyl were unsuccessful. Thorium(IV) fluoride hydrate does not react with boiling dmso.<br/

Neonatal Glycemia and Neurodevelopmental Outcomes at 2 Years

From McKinlay, C. J. D., Alsweiler, J. M., Ansell, J. M., Anstice, N. S., Chase, J. G., Gamble, G. D., … Harding, J. E. (2015). Neonatal Glycemia and Neurodevelopmental Outcomes at 2 Years. New England Journal of Medicine, 373(16), 1507–1518. https://doi.org/10.1056/NEJMoa1504909 Copyright © 2015 Massachusetts Medical Society. Reprinted with permission.Neonatal hypoglycemia is a common and readily treatable risk factor for neurologic impairment in children. Although associations between prolonged symptomatic neonatal hypoglycemia and brain injury are well established,1 the effect of milder hypoglycemia on neurologic development is uncertain.2 Consequently, large numbers of newborns are screened and treated for low blood glucose concentrations, which involves heel-stick blood tests, substantial costs, and the possibility of iatrogenic harm. Under current guidelines,3 up to 30% of neonates are considered to be at risk for hypoglycemia, 15% receive a diagnosis of hypoglycemia, and approximately 10% require admission to a neonatal intensive care unit,4 costing an estimated $2.1 billion annually in the United States alone.5 Associated formula feeding and possible separation of mother and baby reduce breast-feeding rates,6 with potentially adverse effects on broader infant health and development. In addition, pain-induced stress in neonates, such as repeated heel sticks, may itself impair brain development.7 Thus, to determine appropriate glycemic thresholds for treatment, there have been repeated calls for studies of the effect of neonatal hypoglycemia on long-term development.2,8 We report the results of the Children with Hypoglycaemia and Their Later Development (CHYLD) study, a large prospective cohort study of term and late-preterm neonates born at risk for hypoglycemia. The study investigated the relation between the duration, frequency, and severity of low glucose concentrations in the neonatal period and neuropsychological development at 2 years.Supported by grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01HD069622), the Health Research Council of New Zealand (10-399), and the Auckland Medical Research Foundation (1110009)

Monte Carlo Methods for Estimating Interfacial Free Energies and Line Tensions

Excess contributions to the free energy due to interfaces occur for many problems encountered in the statistical physics of condensed matter when coexistence between different phases is possible (e.g. wetting phenomena, nucleation, crystal growth, etc.). This article reviews two methods to estimate both interfacial free energies and line tensions by Monte Carlo simulations of simple models, (e.g. the Ising model, a symmetrical binary Lennard-Jones fluid exhibiting a miscibility gap, and a simple Lennard-Jones fluid). One method is based on thermodynamic integration. This method is useful to study flat and inclined interfaces for Ising lattices, allowing also the estimation of line tensions of three-phase contact lines, when the interfaces meet walls (where "surface fields" may act). A generalization to off-lattice systems is described as well. The second method is based on the sampling of the order parameter distribution of the system throughout the two-phase coexistence region of the model. Both the interface free energies of flat interfaces and of (spherical or cylindrical) droplets (or bubbles) can be estimated, including also systems with walls, where sphere-cap shaped wall-attached droplets occur. The curvature-dependence of the interfacial free energy is discussed, and estimates for the line tensions are compared to results from the thermodynamic integration method. Basic limitations of all these methods are critically discussed, and an outlook on other approaches is given

The screen test 1915–1930:how stars were born

This article examines the emergence of the screen test as a cultural phenomenon during the silent era in the US and Europe and its role in the development of the star system. The lore that grew up around the screen test almost from its inception held out the possibility for members of the public to cross a threshold into the rarefied world of celebrity. The screen test itself is situated in the liminal space not only between audience and actor, but also between fiction and non-fiction, Europe and Hollywood, the silent era and the talkies, and the public and private spheres. In order to trace the ways in which the screen test as such was narrativized and conceptualized in its foundational stages, this article will analyse accounts from Hollywood and European fan magazines of the silent era, including articles, short fiction, and early cinema apocrypha. The article culminates in a discussion of the film Prix de Beaut&eacute; / Beauty Prize (Augusto Genina, 1930), which starred Louise Brooks, herself a transnational film icon whose film career spanned the divide between Hollywood and Europe. The film&rsquo;s final scene, in which a beauty queen is shot dead by her jealous husband as she watches a screen test of herself, has been invoked by a number of film scholars as an allegory of the work performed by cinema, which preserves and disseminates the image of the star far beyond the actor&rsquo;s physical presence. Speaking to historical conditions of star-making while also capturing its resonance in cultural mythology, the conclusion of Prix de Beaut&eacute; allows us to consider the origins and functions of screen test discourse itself

Black Hole Evaporation and Compact Extra Dimensions

We study the evaporation of black holes in space-times with extra dimensions of size L. We first obtain a description which interpolates between the expected behaviors of very large and very small black holes and then show that the luminosity is greatly damped when the horizon shrinks towards L from a larger value. Analogously, black holes born with an initial size smaller than L are almost stable. This effect is due to the dependence of both the Hawking temperature and the grey-body factor of a black hole on the dimensionality of space. Although the picture of what happens when the horizon becomes of size L is still incomplete, we argue that there occurs a (first order) phase transition, possibly signaled by an outburst of energy which leaves a quasi-stable remnant.Comment: RevTeX, 13 pages, 6 figures include

Global motion perception is associated with motor function in 2-year-old children

The final publication is available at Elsevier via https://doi.org/10.1016/j.neulet.2017.08.062 © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The dorsal visual processing stream that includes V1, motion sensitive area V5 and the posterior parietal lobe, supports visually guided motor function. Two recent studies have reported associations between global motion perception, a behavioural measure of processing in V5, and motor function in pre-school and school aged children. This indicates a relationship between visual and motor development and also supports the use of global motion perception to assess overall dorsal stream function in studies of human neurodevelopment. We investigated whether associations between vision and motor function were present at 2 years of age, a substantially earlier stage of development. The Bayley III test of Infant and Toddler Development and measures of vision including visual acuity (Cardiff Acuity Cards), stereopsis (Lang stereotest) and global motion perception were attempted in 404 2-year-old children (±4 weeks). Global motion perception (quantified as a motion coherence threshold) was assessed by observing optokinetic nystagmus in response to random dot kinematograms of varying coherence. Linear regression revealed that global motion perception was modestly, but statistically significantly associated with Bayley III composite motor (r2 = 0.06, P < 0.001, n = 375) and gross motor scores (r2 = 0.06, p < 0.001, n = 375). The associations remained significant when language score was included in the regression model. In addition, when language score was included in the model, stereopsis was significantly associated with composite motor and fine motor scores, but unaided visual acuity was not statistically significantly associated with any of the motor scores. These results demonstrate that global motion perception and binocular vision are associated with motor function at an early stage of development. Global motion perception can be used as a partial measure of dorsal stream function from early childhood.Eunice Kennedy Shriver National Institute of Child Health Human Development of the National Institutes of Health || award number R01HD0692201 Auckland Medical Research Foundation