The Physical Oceanography of the Cape Hatt Region, Eclipse Sound, N.W.T.

In the spring and summer of 1980 and 1981, detailed measurements of water temperature, salinity and depth, currents, tidal height and waves were made in the vicinity of Cape Hatt, at the northern end of Baffin Island, N.W.T., in support of the Baffin Island Oil Spill (BIOS) Project. Currents in the region were generally weak, averaging less than 10 cm/s near the surface and about 2 cm/s in the deeper waters. Deep circulation in Ragged Channel, on the western side of Cape Hatt, was usually counterclockwise. On the western side of Cape Hatt, a strong (up to 30 cm/s) northward flowing coastal current existed. It was occasionally reversed by a flood tide or prolonged south winds. Eddies were observed in bays on the western side of Cape Hatt driven by this coastal current. These eddies were clockwise when the flow offshore was northward and counterclockwise when the flow was southward. Evidence was found for an internal M2 tide in Ragged Channel. Some of the variations in the observed currents and density fields were explained with a simple model of this tide. Under-ice density profiles showed a typical well-mixed layer just above freezing temperature that reached to the bottom in the nearshore regions and to about 35 m depth in mid-channel. In the ice-free season, there was a pronounced shallow mixed layer that ranged from 4 to 10 m in depth. Water properties at the bottom of Ragged Channel were essentially unchanged from winter to summer. In the winter, water properties in Z-Lagoon were similar to those in Ragged Channel. In the summer, they showed the result of being cut off from the main body of Eclipse Sound. In Ragged Channel, wave conditions were very mild, not exceeding 20 cm in significant height, while on the eastern side of Cape Hatt, they were worse, up to 1.4 m, but still not severe.Key words: Eclipse Sound, oceanography, currents, tides, internal tides, water temperature, salinity, wavesMots clés: Eclipse Sound, océanographie, courants, marées, marées internes, température de l’eau, salinité, vague

Polarized emission from hexagonal-silicon-germanium nanowires

We present polarized emission from single hexagonal silicon-germanium (hex-SiGe) nanowires. To understand the nature of the band-to-band emission of hex-SiGe, we have performed photoluminescence spectroscopy to investigate the polarization properties of hex-SiGe core-shell nanowires. We observe a degree of polarization of 0.2 to 0.32 perpendicular to the nanowire c-axis. Finite-difference time-domain simulations were performed to investigate the influence of the dielectric contrast of nanowire structures. We find that the dielectric contrast significantly reduces the observable degree of polarization. Taking into account this reduction, the experimental data are in good agreement with polarized dipole emission perpendicular to the c-axis, as expected for the fundamental band-to-band transition, the lowest energy direct band-to-band transition in the hex-SiGe band structure.</p

On the Hybrid Extension of CTL and CTL+

The paper studies the expressivity, relative succinctness and complexity of satisfiability for hybrid extensions of the branching-time logics CTL and CTL+ by variables. Previous complexity results show that only fragments with one variable do have elementary complexity. It is shown that H1CTL+ and H1CTL, the hybrid extensions with one variable of CTL+ and CTL, respectively, are expressively equivalent but H1CTL+ is exponentially more succinct than H1CTL. On the other hand, HCTL+, the hybrid extension of CTL with arbitrarily many variables does not capture CTL*, as it even cannot express the simple CTL* property EGFp. The satisfiability problem for H1CTL+ is complete for triply exponential time, this remains true for quite weak fragments and quite strong extensions of the logic

Moderate to vigorous physical activity interactions with genetic variants and body mass index in a large US ethnically diverse cohort

Summary What is already known about this subject Genome-Wide Association Studies have successfully identified numerous genetic loci that influence body mass index in European-descent middle-aged adults. Adolescence is a high-risk period for the development of adult obesity and severe obesity. Physical activity is one of the most promising behavioural candidates for preventing and reducing weight gain, particularly among youth. What this study adds An examination of the joint association between 41 of the well-established obesity susceptibility single-nucleotide polymorphisms with <5 vs. ≥5 bouts of moderate to vigorous physical activity (MVPA) per week in relation to body mass index (BMI)-for-age Z-score in a nationally representative sample of European American, African-American and Hispanic American adolescents. Three nominally significant interactions (P < 0.05) varied by race/ethnicity. Overall, the estimated effect of the risk allele on BMI-for-age Z-score was greater in individuals with <5 than those with ≥5 bouts MVPA per week. Background Little is known about the interaction between genetic and behavioural factors during lifecycle risk periods for obesity and how associations vary across race/ethnicity. Objective The objective of this study was to examine joint associations of adiposity-related single-nucleotide polymorphisms (SNPs) and moderate to vigorous physical activity (MVPA) with body mass index (BMI) in a diverse adolescent cohort. Methods Using data from the National Longitudinal Study of Adolescent Health (n = 8113: Wave II 1996; ages 12-21, Wave III; ages 18-27), we assessed interactions of 41 well-established SNPs and MVPA with BMI-for-age Z-scores in European Americans (EA; n = 5077), African-Americans (AA; n = 1736) and Hispanic Americans (HA; n = 1300). Results Of 97 assessed, we found nominally significant SNP-MVPA interactions on BMI-for-age Z-score in EA at GNPDA2 and FTO and in HA at LZTR2/SEC16B. In EA, the estimated effect of the FTO risk allele on BMI-for-age Z-score was lower (β = -0.13; 95% confidence interval [CI]: 0.08, 0.18) in individuals with ≥5 vs. <5 (β = 0.24; CI: 0.16, 0.32) bouts of MVPA per week (P for interaction 0.02). Race/ethnicity-pooled meta-analysis showed nominally significant interactions for SNPs at TFAP2B, POC5 and LYPLAL1. Conclusions High MVPA may attenuate underlying genetic risk for obesity during adolescence, a high-risk period for adult obesity

Screen time behaviours may interact with obesity genes, independent of physical activity, to influence adolescent BMI in an ethnically diverse cohort

Background There has been little investigation of gene-by-environment interactions related to sedentary behaviour, a risk factor for obesity defined as leisure screen time (ST; i.e. television, video and computer games). Objective To test the hypothesis that limiting ST use attenuates the genetic predisposition to increased body mass index (BMI), independent of physical activity. Design Using 7642 wave II participants of the National Longitudinal Study of Adolescent Health, (Add Health; mean=16.4 years, 52.6% female), we assessed the interaction of ST (hweek-1) and 41 established obesity single nucleotide polymorphisms (SNPs) with age- and sex-specific BMI Z-scores in 4788 European-American (EA), 1612 African-American (AA) and 1242 Hispanic American (HA) adolescents. Results Nominally significant SNP ST interaction were found for FLJ35779 in EA, GNPDA2 in AA and none in HA (EA: beta [SE]=0.016[0.007]), AA: beta [SE]=0.016[0.011]) per 7hweek-1 ST and one risk allele in relation to BMI Z-score. Conclusions While for two established BMI loci, we find evidence that high levels of ST exacerbate the influence of obesity susceptibility variants on body mass; overall, we do not find strong evidence for interactions between the majority of established obesity loci. However, future studies with larger sample sizes, or that may build on our current study and the growing published literature, are clearly warranted

Evidence for Association between SH2B1 Gene Variants and Glycated Hemoglobin in Nondiabetic European American Young Adults: The Add Health Study

Glycated hemoglobin (HbA1c) is used to classify glycaemia and type 2 diabetes (T2D). Body mass index (BMI) is a predictor of HbA1c levels and T2D. We tested 43 established BMI and obesity loci for association with HbA1c in a nationally representative multiethnic sample of young adults from the National Longitudinal Study of Adolescent to Adult Health [Add Health: age 24–34 years; n = 5641 European Americans (EA); 1740 African Americans (AA); 1444 Hispanic Americans (HA)] without T2D, using two levels of covariate adjustment (Model 1: age, sex, smoking, and geographic region; Model 2: Model 1 covariates plus BMI). Bonferroni adjustment was made for 43 SNPs and we considered P &lt; 0.0011 statistically significant. Means (SD) for HbA1c were 5.4% (0.3) in EA, 5.7% (0.4) in AA, and 5.5% (0.3) in HA. We observed significant evidence for association with HbA1c for two variants near SH2B1 in EA (rs4788102, P = 2.2 × 10−4; rs7359397, P = 9.8 × 10−4) for Model 1. Both results were attenuated after adjustment for BMI (rs4788102, P = 1.7 × 10−3; rs7359397, P = 4.6 × 10−3). No variant reached Bonferroni-corrected significance in AA or HA. These results suggest that SH2B1 polymorphisms are associated with HbA1c, largely independent of BMI, in EA young adults

SN1A data and the CMB of Modified Curvature at short and long distances

The SN1a data, although inconclusive, when combined with other observations makes a strong case that our universe is presently dominated by dark energy. We investigate the possibility that large distance modifications of the curvature of the universe would perhaps offer an alternative explanation of the observation. Our calculations indicate that a universe made up of no dark energy but instead, with a modified curvature at large scales, is not scale-invariant, therefore quite likely it is ruled out by the CMB observations. The sensitivity of the CMB spectrum is checked for the whole range of mode modifications of large or short distance physics. The spectrum is robust against modifications of short-distance physics and the UV cutoff when: the initial state is the adiabatic vacuum, and the inflationary background space is de Sitter.Comment: 13 pages, 2 eps figures, typos corrected, references added; to appear in Phys. Rev.

Modeling oscillatory Microtubule--Polymerization

Polymerization of microtubules is ubiquitous in biological cells and under certain conditions it becomes oscillatory in time. Here simple reaction models are analyzed that capture such oscillations as well as the length distribution of microtubules. We assume reaction conditions that are stationary over many oscillation periods, and it is a Hopf bifurcation that leads to a persistent oscillatory microtubule polymerization in these models. Analytical expressions are derived for the threshold of the bifurcation and the oscillation frequency in terms of reaction rates as well as typical trends of their parameter dependence are presented. Both, a catastrophe rate that depends on the density of {\it guanosine triphosphate} (GTP) liganded tubulin dimers and a delay reaction, such as the depolymerization of shrinking microtubules or the decay of oligomers, support oscillations. For a tubulin dimer concentration below the threshold oscillatory microtubule polymerization occurs transiently on the route to a stationary state, as shown by numerical solutions of the model equations. Close to threshold a so--called amplitude equation is derived and it is shown that the bifurcation to microtubule oscillations is supercritical.Comment: 21 pages and 12 figure