Mercury in the environs of the north slope of Alaska

The analysis of Greenland ice suggests that the flux of mercury from the continents to the atmosphere has increased in recent times, perhaps partly as a result of the many of man’s activities that effect an alteration of terrestrial surfaces. Upon the exposure of fresh crustal matter, the natural outgassing of mercury vapor from the earth’s surface could be enhanced. Accordingly, mercury was measured in a variety of environmental materials gathered from the North Slope of Alaska to provide background data prior to the anticipated increase of activity in this environment. The materials were collected during the U. S. Coast Guard WEBSEC 72-73 cruises as well as through the facilities provided by Naval Arctic Research Laboratory in the spring of 1973. The method of measurement depended upon radioactivation of mercury with neutrons and the subsequent quantification of characteristic gamma radiations after radiochemical purification. Mercury concentrations in seawater at several locations in the vicinity of 151°W, 71°N averaged 20 parts per trillion. The waters from all stations east of this location showed a significantly smaller concentration. This difference may relate to penetration o f Bering- Chukchi Sea water into the southern Beaufort Sea to 151°W. Marine sediments on the shelf and slope between 143°W and 153°W contained about 100 parts per billion mercury, except for those on the continental shelf between Barter Island and the Canning River, where the concentration was less than half this value. These results are consistent with sediment input from the respective rivers when their mercury content and mineralogy are considered. The mercury content of river waters was 18 ppt and in reasonable agreement with the average of snow samples (13 ppt). The burden of mercury in plankton was 37 ppb.This work was supported by the office of Naval Research under grant N R 083-290

Systèmes et modèles : quelques repères bibliographiques

L'étude bibliographique comparée fait apparaître la diversité des conceptions relatives aux systèmes et la polysémie du terme de modèle. De ce fait les deux concepts ne peuvent constituer la matrice commune des disciplines au cours de la transposition didactique. Mais les points de convergence des analyses sont importants pour le didacticien. La référence au système permet de situer la dissection analytique dont l'emploi exclusif tend à donner une idée caricaturale de la démarche expérimentale. La modélisation comporte des opérations intellectuelles communes dont l'explication est à la fois une exigence de rigueur disciplinaire et un facteur du développement cogniti

Combinations of scleroderma hallmark autoantibodies associate with distinct clinical phenotypes

Systemic sclerosis (SSc) is characterized by the presence of SSc-specific or SSc-associated antibodies (SSc-Abs): anti-topoisomerase I (ATA), anti-centromere (ACA), anti-RNA polymerase III (ARA), anti-U3RNP (U3RNP), anti-U1RNP (U1RNP), anti-PmScl (PmScl), anti-Ku (Ku) and anti-Th/To (Th/To), each being associated with specific clinical features and prognosis. The detection of more than one SSc-Abs in SSc patients is rare and only few data about these patients' clinical phenotype is available. The aim of our study was to evaluate the frequency and the disease's features associated with the presence of > 1 SSc-Abs positivity in a large cohort of SSc patients. The autoantibody profiles of 2799 SSc patients from February 2001 to June 2017 were retrospectively reviewed. Patients with > 1 SSc-Abs were identified. Clinical features were collected and compared to a large historical cohort of SSc patients with single SSc-Ab positivity. SSc patients were excluded if previously treated with rituximab, intravenous immunoglobulins or stem cell transplantation. Non-parametric tests were used for statistical analysis. Nearly 5% of SSc patients from our cohort had ≥ 2 autoantibody positivity, and 2.3% (n = 72) had ≥ 2 SSc-Abs positivity. Th e most common combination was U1RNP and ATA (35%). These patients were younger than patients with single autoantibody positivity and showed more commonly a diffuse cutaneous SSc form. They also had higher rates of overlap features compared to ATA patients. Other combinations included U1RNP and ACA (13%), ATA and ACA (7%) and U1RNP and PmScl (5%). In our study we observed that, while infrequently, SSc patients can present with a combination of two SSc-Abs and that the double positivity can influence their clinical phenotype compared to patients with single SSc-Ab positivity. The importance of re-testing SSc-Abs in patients with changing clinical phenotypes was also highlighted, as this may confer a differing risk stratification

What it takes to measure a fundamental difference between dark matter and baryons: the halo velocity anisotropy

Numerous ongoing experiments aim at detecting WIMP dark matter particles from the galactic halo directly through WIMP-nucleon interactions. Once such a detection is established a confirmation of the galactic origin of the signal is needed. This requires a direction-sensitive detector. We show that such a detector can measure the velocity anisotropy beta of the galactic halo. Cosmological N-body simulations predict the dark matter anisotropy to be nonzero, beta~0.2. Baryonic matter has beta=0 and therefore a detection of a nonzero beta would be strong proof of the fundamental difference between dark and baryonic matter. We estimate the sensitivity for various detector configurations using Monte Carlo methods and we show that the strongest signal is found in the relatively few high recoil energy events. Measuring beta to the precision of ~0.03 will require detecting more than 10^4 WIMP events with nuclear recoil energies greater than 100 keV for a WIMP mass of 100 GeV and a 32S target. This number corresponds to ~10^6 events at all energies. We discuss variations with respect to input parameters and we show that our method is robust to the presence of backgrounds and discuss the possible improved sensitivity for an energy-sensitive detector.Comment: 15 pages, 8 figures, accepted by JCAP. Matches accepted versio

Charge amplification concepts for direction-sensitive dark matter detectors

Direction measurement of weakly interacting massive particles in time-projection chambers can provide definite evidence of their existence and help to determine their properties. This article demonstrates several concepts for charge amplification in time-projection chambers that can be used in direction-sensitive dark matter search experiments. We demonstrate reconstruction of the 'head-tail' effect for nuclear recoils above 100keV, and discuss the detector performance in the context of dark matter detection and scaling to large detector volumes.Comment: 15 pages, 9 figure

The Src Homology and Collagen A (ShcA) adaptor protein is required for the spatial organization of the costamere/Z-disk network during heart development

ShcA (Src Homology and Collagen A) is an adaptor protein that binds to tyrosine kinase receptors. Its germ line deletion is embryonic lethal with abnormal cardiovascular system formation, and its role in cardiovascular development is unknown. To investigate its functional role in cardiovascular development in mice, ShcA was deleted in cardiomyocytes and vascular smooth muscle cells by crossing ShcA flox mice with SM22a-Cre transgenic mice. Conditional mutant mice developed signs of severe dilated cardiomyopathy, myocardial infarctions, and premature death. No evidence of a vascular contribution to the phenotype was observed. Histological analysis of the heart revealed aberrant sarcomeric Z-disk and M-band structures, and misalignments of T-tubules with Z-disks. We find that not only the ErbB3/Neuregulin signaling pathway but also the baroreceptor reflex response, which have been functionally associated, are altered in the mutant mice. We further demonstrate that ShcA interacts with Caveolin-1 and the costameric protein plasma membrane Ca2+/calmodulin-dependent ATPase (PMCA), and that its deletion leads to abnormal dystrophin signaling. Collectively, these results demonstrate that ShcA interacts with crucial proteins and pathways that link Z-disk and costamere

Constraining New Physics with a Positive or Negative Signal of Neutrino-less Double Beta Decay

We investigate numerically how accurately one could constrain the strengths of different short-range contributions to neutrino-less double beta decay in effective field theory. Depending on the outcome of near-future experiments yielding information on the neutrino masses, the corresponding bounds or estimates can be stronger or weaker. A particularly interesting case, resulting in strong bounds, would be a positive signal of neutrino-less double beta decay that is consistent with complementary information from neutrino oscillation experiments, kinematical determinations of the neutrino mass, and measurements of the sum of light neutrino masses from cosmological observations. The keys to more robust bounds are improvements of the knowledge of the nuclear physics involved and a better experimental accuracy.Comment: 23 pages, 3 figures. Minor changes. Matches version published in JHE

Some Aspects of Multifractal analysis

The aim of this survey is to present some aspects of multifractal analysis around the recently developed subject of multiple ergodic averages. Related topics include dimensions of measures, oriented walks, Riesz products etc

Non--power law behavior of the radial profile of phase--space density of halos

We study the pseudo phase-space density, $\rho(r)/\sigma^3(r)$, of $\Lambda$CDM dark matter halos with and without baryons (baryons+DM, and pure DM), by using the model introduced in Del Popolo (2009), which takes into account the effect of dynamical friction, ordered and random angular momentum, baryons adiabatic contraction and dark matter baryons interplay. We examine the radial dependence of $\rho(r)/\sigma^3(r)$ over 9 orders of magnitude in radius for structures on galactic and cluster of galaxies scales. We find that $\rho(r)/\sigma^3(r)$ is approximately a power-law only in the range of halo radius resolved by current simulations (down to 0.1% of the virial radius) while it has a non-power law behavior below the quoted scale, with inner profiles changing with mass. The non-power-law behavior is more evident for halos constituted both of dark matter and baryons while halos constituted just of dark matter and with angular momentum chosen to reproduce a Navarro-Frenk-White (NFW) density profile, are characterized by an approximately power-law behavior. The results of the present paper lead to conclude that density profiles of the NFW type are compatible with a power-law behavior of $\rho(r)/\sigma^3(r)$, while those flattening to the halo center, like those found in Del Popolo (2009) or the Einasto profile, or the Burkert profile, cannot produce radial profile of the pseudo-phase-space density that are power-laws at all radii. The results argue against universality of the pseudo phase-space density and as a consequence argue against universality of density profiles constituted by dark matter and baryons as also discussed in Del Popolo (2009).Comment: 20 pages; 7 figs. arXiv admin note: substantial text overlap with arXiv:0906.4447 and arXiv:1012.432