Local and Remote Controls on Arctic Mixed-Layer Evolution

In this study Lagrangian large-eddy simulation of cloudy mixed layers in evolving warm air masses in the Arctic is constrained by in situ observations from the recent PASCAL field campaign. A key novelty is that time dependence is maintained in the large-scale forcings. An iterative procedure featuring large-eddy simulation on microgrids is explored to calibrate the case setup, inspired by and making use of the typically long memory of Arctic air masses for upstream conditions. The simulated mixed-phase clouds are part of a turbulent mixed layer that is weakly coupled to the surface and is occasionally capped by a shallow humidity layer. All eight simulated mixed layers exhibit a strong time evolution across a range of time scales, including diurnal but also synoptic fingerprints. A few cases experience rapid cloud collapse, coinciding with a rapid decrease in mixed-layer depth. To gain insight, composite budget analyses are performed. In the mixed-layer interior the heat and moisture budgets are dominated by turbulent transport, radiative cooling, and precipitation. However, near the thermal inversion the large-scale vertical advection also contributes significantly, showing a distinct difference between subsidence and upsidence conditions. A bulk mass budget analysis reveals that entrainment deepening behaves almost time-constantly, as long as clouds are present. In contrast, large-scale subsidence fluctuates much more strongly and can both counteract and boost boundary-layer deepening resulting from entrainment. Strong and sudden subsidence events following prolonged deepening periods are found to cause the cloud collapses, associated with a substantial reduction in the surface downward longwave radiative flux. ©2019. The Authors

An X-ray and Optical Investigation of the Environments Around Nearby Radio Galaxies

Investigations of the cluster environment of radio sources have not shown a correlation between radio power and degree of clustering. However, it has been demonstrated that extended X-ray luminosity and galaxy clustering do exhibit a positive correlation. This study investigates a complete sample of 25 nearby (z less than 0.06) radio galaxies which are not cataloged members of Abell clusters. The environment of these radio galaxies is studied in both the X-ray and the optical by means of the ROSAT All-Sky Survey (RASS), ROSAT pointed observations, and the Palomar optical Digitized Sky Survey (DSS). X-ray luminosities and extents are determined from the RASS, and the DSS is used to quantify the degree of clustering via the spatial two-point correlation coefficient, Bgg. Of the 25 sources, 20 are greater than sigma detections in the X-ray and 11 possessed Bgg's significantly in excess of that expected for an isolated galaxy. Adding the criterion that the X-ray emission be resolved, 10 of the radio galaxies do appear to reside in poor clusters with extended X-ray emission suggestive of the presence of an intracluster medium. Eight of these galaxies also possess high spatial correlation coefficients. Taken together, these data suggest that the radio galaxies reside in a low richness extension of the Abell clusters. The unresolved X-ray emission from the other galaxies is most likely associated with AGN phenomena. Furthermore, although the sample size is small, it appears that the environments of FR I and FR II sources differ. FR I's tend to be more frequently associated with extended X-ray emission (10 of 18), whereas FR II's are typically point sources or non-detections in the X-ray (none of the 7 sources exhibit extended X-ray emission).Comment: 28 page postscript file including figures and tables, plus one landscape table and 5 GIF figure

Gauge copies in the Landau-DeWitt gauge: a background invariant restriction

The Landau background gauge, also known as the Landau-DeWitt gauge, has found renewed interest during the past decade given its usefulness in accessing the confinement-deconfinement transition via the vacuum expectation value of the Polyakov loop, describable via an appropriate background. In this Letter, we revisit this gauge from the viewpoint of it displaying gauge (Gribov) copies. We generalize the Gribov-Zwanziger effective action in a BRST and background invariant way; this action leads to a restriction on the allowed gauge fluctuations, thereby eliminating the infinitesimal background gauge copies. The explicit background invariance of our action is in contrast with earlier attempts to write down and use an effective Gribov-Zwanziger action. It allows to address certain subtleties arising in these earlier works, such as a spontaneous and thus spurious Lorentz symmetry breaking, something which is now averted.Comment: 14 pages. v2: version to appear in Phys.Lett.B, with minor modifications and extra reference

Survey for small cetaceans over the Dogger Bank and adjacent areas in summer 2011

Review of New Information on Population Size, Distribution, Structure and Causes of Any Changes. The distribution of small cetaceans in the offshore areas of the North Sea has been in the interest of researchers for many years. Information on abundance and distribution is essential to assess the impact of bycatch and other anthropogenic threats, and as basis for management plans to ensure the favourable conservation status of these species. In 2011 we conducted a dedicated aerial line transect survey of the Dogger Bank and adjacent areas (UK, NL, DK, GE waters) in order to investigate the importance of this marine feature as summer habitat for marine mammals

Tracking molecular wave packets in cesium dimers by coherent Raman scattering

We explore wave-packet dynamics in the ground X 1Σ+g and excited B 1Πu states of cesium dimers (Cs2). In particular, we study the dependence of the wave- packet dynamics on the relative timing between femtosecond pump, Stokes, and probe pulses in a nondegenerate BOXCARS beam geometry, which are commonly used for coherent anti-Stokes Raman scattering (CARS) spectroscopy. The experimental results are elucidated by theoretical calculations, which are based on the Liouville equations for the density matrix for the molecular states. We observe oscillations in CARS signals as functions of both Stokes and probe pulse delays with respect to the pump pulse. The oscillation period relates to the wave-packet motion cycle in either the ground or excited state of Cs2 molecules, depending on the sequence of the input laser pulses in time. The performed analysis can be applied to study and/or manipulate wave-packet dynamics in a variety of molecules. It also provides an excellent test platform for theoretical models of molecular systems

A erradicação do trabalho escravo até 2030 e os desafios da vigilância em saúde do trabalhador

A erradicação das formas contemporâneas de escravidão é uma relevante questão científica, social e institucional. De fato, esforços globais têm sido feitos para compreender, mapear e eliminar a escravidão contemporânea, como um dos objetivos do Desenvolvimento Sustentável das Nações Unidas até 2030. Entretanto, pouca atenção tem sido dada para o lugar da vigilância em saúde do trabalhador (VISAT) nas estratégias e lutas pela erradicação dessas relações de exploração. Para suprir essa lacuna, este artigo discute o trabalho escravo contemporâneo (TEC) e suas especificidades no Brasil, na perspectiva da VISAT. Inicialmente, destacamos as relações entre trabalho escravo, saúde do/a trabalhador/a e a vigilância em saúde e, em seguida, apresentamos três desafios da vigilância para o enfretamento do TEC: (1) o desafio de caracterizar setores econômicos, regiões e populações afetadas; (2) de identificar determinantes, riscos e efeitos à saúde; (3) e de fortalecer práticas e serviços de saúde do trabalhador para desencadear ações de formação, informação e intervenção em regiões de maior presença de TEC. Conclui-se que a vigilância em saúde do trabalhador pode trazer contribuições significativas para emancipação de trabalhadores em contextos de trabalho escravo. Eradicating modern slavery is a relevant scientific, social, and institutional challenge issue. Indeed, efforts are being made at a global scale to understand and eradicate contemporary slavery as a target of the United Nations Sustainable Development Goals by 2030. However, little attention has been given to the Worker Health Surveillance (WHS) in the struggle against contemporary forms of slavery. To fill this gap, the paper discuss contemporary slave labour (CSL) from a workers health surveillance perspective, calling attention to challenges evident in the case of Brazil. Further, we explain the connection of CSL to workers health and to workers health surveillance (WHS). We then identify and discuss three challenges of CSL to WHS: 1. help to characterise and identify economic sectors and populations most affected by slave labour; 2. identify determinants, risks, and health effects related to CSL; and 3. strengthen workers health services to trigger specific actions in terms of formation, information, and intervention in regions of high CSL prevalence. We conclude that Workers Health Surveillance can play an important role towards workers emancipation slavery relations

Cloud microphysical effects of turbulent mixing and entrainment

Turbulent mixing and entrainment at the boundary of a cloud is studied by means of direct numerical simulations that couple the Eulerian description of the turbulent velocity and water vapor fields with a Lagrangian ensemble of cloud water droplets that can grow and shrink by condensation and evaporation, respectively. The focus is on detailed analysis of the relaxation process of the droplet ensemble during the entrainment of subsaturated air, in particular the dependence on turbulence time scales, droplet number density, initial droplet radius and particle inertia. We find that the droplet evolution during the entrainment process is captured best by a phase relaxation time that is based on the droplet number density with respect to the entire simulation domain and the initial droplet radius. Even under conditions favoring homogeneous mixing, the probability density function of supersaturation at droplet locations exhibits initially strong negative skewness, consistent with droplets near the cloud boundary being suddenly mixed into clear air, but rapidly approaches a narrower, symmetric shape. The droplet size distribution, which is initialized as perfectly monodisperse, broadens and also becomes somewhat negatively skewed. Particle inertia and gravitational settling lead to a more rapid initial evaporation, but ultimately only to slight depletion of both tails of the droplet size distribution. The Reynolds number dependence of the mixing process remained weak over the parameter range studied, most probably due to the fact that the inhomogeneous mixing regime could not be fully accessed when phase relaxation times based on global number density are considered.Comment: 17 pages, 10 Postscript figures (figures 3,4,6,7,8 and 10 are in reduced quality), to appear in Theoretical Computational Fluid Dynamic

First Measurement of the Transverse Spin Asymmetries of the Deuteron in Semi-Inclusive Deep Inelastic Scattering

First measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarized 6-LiD target are presented. The data were taken in 2002 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. The Collins asymmetry turns out to be compatible with zero, as does the measured Sivers asymmetry within the present statistical errors.Comment: 6 pages, 2 figure

Gamma-loud quasars: a view with BeppoSAX

We present $Beppo$SAX observations of the $\gamma$-ray emitting quasars 0836+710, 1510-089 and 2230+114. All the objects have been detected in the PDS up to 100 keV and have extremely flat power-law spectra above 2 keV ($\alpha _x$=0.3--0.5). 0836+710 shows absorption higher than the galactic value and marginal evidence for the presence of the redshifted 6.4 keV Iron line. 1510-089 shows a spectral break around 1 keV, with the low energy spectrum steeper ($\alpha_l$=1.6) than the high energy power-law ($\alpha_h$=0.3). The data are discussed in the light of current Inverse Compton models for the high energy emission.Comment: 4 pages, 2 figures, to appear in the proceedings of the conference "X-Ray Astronomy '99", Bologna, Italy, September 199