Thermally-Assisted Current-Driven Domain Wall Motion

Starting from the stochastic Landau-Lifschitz-Gilbert equation, we derive Langevin equations that describe the nonzero-temperature dynamics of a rigid domain wall. We derive an expression for the average drift velocity of the domain wall as a function of the applied current, and find qualitative agreement with recent magnetic semiconductor experiments. Our model implies that at any nonzero temperature the average domain-wall velocity initially varies linearly with current, even in the absence of non-adiabatic spin torques.Comment: 4 pages, 2 figure

Mapping and functional characterization of the murine Smoothelin-like 1 promoter

BACKGROUND: Smoothelin-like 1 (SMTNL1, also known as CHASM) plays a role in promoting relaxation as well as adaptive responses to exercise, pregnancy and sexual development in smooth and skeletal muscle. Investigations of Smtnl1 transcriptional regulation are still lacking. Thus, in this study, we identify and characterize key regulatory elements of the mouse Smtnl1 gene. RESULTS: We mapped the key regulatory elements of the Smtnl1 promoter region: the transcriptional start site (TSS) lays -44 bp from the translational start codon and a TATA-box motif at -75 bp was conserved amongst all mammalian Smtnl1 promoters investigated. The Smtnl1 proximal promoter enhances expression up to 8-fold in smooth muscle cells and a second activating region lays 500 bp further upstream. Two repressing motifs were present (-118 to -218 bp and -1637 to -1869 bp). The proximal promoter is highly conserved in mammals and contains a mirror repeat sequence. In silico analysis suggests many transcription factors (notably MyoD) could potentially bind within the Smtnl1 proximal promoter sequence. CONCLUSION: Smtnl1 transcript was identified in all smooth muscle tissues examined to date, albeit at much lower levels than found in skeletal muscle. It is unlikely that multiple SMTNL1 isoforms exist since a single Smtnl1 transcription start site was identified in both skeletal and intestinal smooth muscle. Promoter studies suggest restrictive control of Smtnl1 expression in non-muscle cells

Phosphorylation of telokin by cyclic nucleotide kinases and the identification of in vivo phosphorylation sites in smooth muscle

AbstractThe Ca2+-independent acceleration of dephosphorylation of the regulatory light chain of smooth muscle myosin and relaxation of smooth muscle by telokin are enhanced by cyclic nucleotide-activated protein kinase(s) [Wu et al. (1998) J. Biol. Chem. 273, 11362–11369]. The purpose of this study was to determine the in vivo site(s) and in vitro rates of telokin phosphorylation and to evaluate the possible effects of sequential phosphorylation by different kinases. The in vivo site(s) of phosphorylation of telokin were determined in rabbit smooth muscles of longitudinal ileum and portal vein. Following stimulation of ileum with forskolin (20 μM) the serine at position 13 was the only amino acid to exhibit increased phosphorylation. Rabbit portal vein telokin was phosphorylated on both Ser-13 and -19 as a result of forskolin and GTPγS stimulation in vivo. Point mutation of Ser-13 (to Ala or Asp) abolished in vitro phosphorylation by cyclic nucleotide-dependent protein kinases

Early Neoproterozoic Basin Formation in Yukon, Canada: Implications for the make-up and break-up of Rodinia

SUMMARY: Geological mapping and stratigraphic anaylsis of the early Neoproterozoic Fifteenmile Group in the western Ogilvie Mountains of Yukon, Canada, has revealed large lateral facies changes in both carbonate and siliciclastic strata.  Syn-sedimentary NNW-side-down normal faulting during deposition of the lower Fifteenmile Group generated local topographic relief and wedge-shaped stratal geometries. These strata were eventually capped by platformal carbonate after the establishment of a NNW-facing stromatolitic reef complex that formed adjacent to the coeval Little Dal Group of the Mackenzie Mountains, Northwest Territories.  Correlations between specific formations within these groups are tested with carbon isotope chemostratigraphy.  As there are no known 830-780 Ma stratigraphic successions south of 62°N, the basin-forming event that accommodated the Fifteenmile and Little Dal Groups of the Ogilvie and Mackenzie Mountains and equivalent strata in the Shaler Supergroup of Victoria Island was restricted to the northwest margin of Laurentia. Therefore, this event does not represent widespread rifting of the entire western margin of Laurentia and instead we propose that these strata were accommodated in a failed rift generated by localized subsidence associated with the emplacement of the coeval Guibei (China) and Gairdner (Australia) large igneous provinces.  The northern margin of Laurentia was reactivated by renewed extension at ca. 720 Ma associated with the emplacement of the Franklin large igneous province.  Significant crustal thinning and generation of a thermally subsiding passive margin on the western margin of Laurentia may not have occurred until the late Ediacaran.RÉSUMÉLe cartographiage géologique et l’analyse stratigraphique du groupe néoprotézoïque Fifteenmile situé à l’ouest des montagnes Ogilvie du Yukon, Canada, ont révélé de grands changements latéraux de faciès à la fois pour les strates carbonatées et silicoclastiques. La mise en place des failles normales syn-sédimentaires inclinées vers le NNW au cours du dépôt du groupe Fifteenmile inférieur, a entrainé la formation locale d’un relief topographique et une prisme des strates. Ces dernières ont finalement été recouvertes de carbonates de plate-forme issus de la mise en place d’un complexe récifal stromatolitique exposé NNW contigu à la formation de même âge du groupe Little Dal des montagnes Ogilvie, en Territoires du Nord-Ouest. Les corrélations existant entre des formations spécifiques de chacun de ces groupes, sont testées grâce à la chimiostratigraphie des isotopes du carbone. Aucunes successions stratigraphiques agées de 830-780 Ma n’étant connues au sud de 62° N, la formation du bassin où sont accumulés les groupes Fifteenmile et Little Dal des massifs Ogilvie et Mackenzie, ainsi que les strates analogues du supergroupe Shaler de l’île Victoria, était restreinte à la bordure nord-ouest de la Laurentie. De ce fait, cet événement ne correspond pas au large rifting s’étendant sur l’entière bordure ouest de la Laurentie et nous proposons à la place, que ces strates ont été localisées au cours d’un rift avorté généré par la mise en place simultanée des larges provinces ignées Guibei (Chine) et Gairdner (Australie). La bordure nord de la Laurentie a été réactivée par une nouvelle phase d’extension à ca. 720 Ma associée à l’emplacement de la province ignée Franklin. L’amincissement crustal et la formation d’une marge passive thermiquement subsidente le long de la bordure ouest de la Laurentie ne se sont certainement pas produits avant l’Édiacarien supérieur

Fermionic construction of partition functions for two-matrix models and perturbative Schur function expansions

A new representation of the 2N fold integrals appearing in various two-matrix models that admit reductions to integrals over their eigenvalues is given in terms of vacuum state expectation values of operator products formed from two-component free fermions. This is used to derive the perturbation series for these integrals under deformations induced by exponential weight factors in the measure, expressed as double and quadruple Schur function expansions, generalizing results obtained earlier for certain two-matrix models. Links with the coupled two-component KP hierarchy and the two-component Toda lattice hierarchy are also derived.Comment: Submitted to: "Random Matrices, Random Processes and Integrable Systems", Special Issue of J. Phys. A, based on the Centre de recherches mathematiques short program, Montreal, June 20-July 8, 200

A Method for Thermal Performance Characterization of Ultra-Thin Vapor Chambers Cooled by Natural Convection

Vapor chamber technologies offer an attractive approach for passive cooling in portable electronic devices. Due to the market trends in device power consumption and thickness, vapor chamber effectiveness must be compared with alternative heat spreading materials at ultra-thin form factors and low heat dissipation rates. A test facility is developed to experimentally characterize performance and analyze the behavior of ultra-thin vapor chambers that must reject heat to the ambient via natural convection. The evaporator-side and ambient temperatures are measured directly; the condenser-side surface temperature distribution, which has critical ergonomics implications, is measured using an infrared camera calibrated pixel-by-pixel over the field of view and operating temperature range. The high thermal resistance imposed by natural convection in the vapor chamber heat dissipation pathway requires accurate prediction of the parasitic heat losses from the test facility using a combined experimental and numerical calibration procedure. Solid Metal heat spreaders of known thermal conductivity are first tested, and the temperature distribution is reproduced using a numerical model for conduction in the heat spreader and thermal insulation by iteratively adjusting the external boundary conditions. A regression expression for the heat loss is developed as a function of measured operating conditions using the numerical model. A sample vapor chamber is tested for heat inputs below 2.5 W. Performance metrics are developed to characterize heat spreader performance in terms of the effective thermal resistance and the condenser-side temperature uniformity. The study offers a rigorous approach for testing and analysis of new vapor chamber designs, with accurate characterization of their performance relative to other heat spreaders

The Ca and Mg isotope record of the Cryogenian Trezona carbon isotope excursion

This work was supported by a grant from the Simons Foundation (SCOL 611878, ASCA) and the Carlsberg Foundation to ASCA. ASCA and CJB also acknowledge support from the Danish National Research Foundation (Grant No. DNRF53). ACM and CVR acknowledge support from NSF (EAR-0842946) for funding fieldwork on the Trezona Formation in South Australia. JAH acknowledges support from NSF (IES-1410317) and from NSF OCE CAREER Grant (1654571).The Trezona carbon isotope excursion is recorded on five different continents in platform carbonates deposited prior to the end-Cryogenian Marinoan glaciation (>635 Ma) and represents a change in carbon isotope values of 16–18‰. Based on the spatial and temporal reproducibility, the excursion previously has been interpreted as tracking the carbon isotopic composition of dissolved inorganic carbon in the global ocean before the descent into a snowball Earth. However, in modern restricted shallow marine and freshwater settings, carbon isotope values have a similarly large range, which is mostly independent from open ocean chemistry and instead reflects local processes. In this study, we combine calcium, magnesium, and strontium isotope geochemistry with a numerical model of carbonate diagenesis to disentangle the degree to which the Trezona excursion reflects changes in global seawater chemistry versus local shallow-water platform environments. Our analysis demonstrates that the most extreme carbon isotope values (∼-10‰ versus +10‰) are preserved in former platform aragonite that was neomorphosed to calcite during sediment-buffered conditions and record the primary carbon isotope composition of platform-top surface waters. In contrast, the downturn and recovery of the Trezona excursion are recorded in carbonates that were altered during early fluid-buffered diagenesis and commonly are dolomitized. We also find that the nadir of the Trezona excursion is associated with a fractional increase in siliciclastic sediments, whereas the recovery from the excursion correlates with a relative increase in carbonate. This relationship suggests that the extreme negative isotopic shift in platform aragonite occurred in concert with periods of increased input of siliciclastic sediments, changes in water depth, and possibly nutrients to platform environments. Although the process for generating extremely negative carbon isotope values in Neoproterozoic platform carbonates remains enigmatic, we speculate that these excursions reflect kinetic isotope effects associated with CO2 invasion in platform waters during periods of intense primary productivity.Publisher PDFPeer reviewe

Continuity or change in business representation in Britain? An assessment of the Heseltine initiatives of the 1990s

Britain has a fragmented, overlapping, and underresourced system of business representation. Attempts at reform, however, have proved difficult and largely unsuccessful. A coherent and logical system is relevant, in terms of both an effective dialogue between government and business, and the promotion of competitiveness and productivity. Through interviews and archival evidence, I look at how government has attempted to reform business associations. The main focus is the Heseltine initiatives of the 1990s: I outline the various initiatives taken, reveal the extent to which policy represented continuity or change, and consider whether the initiatives were effective. I show that they had a degree of success but that they would have made greater impact if they had been sustained over a longer period of time. A consideration of the historical context, moreover, suggests there may be limits to the role of government intervention in business association reform

Heart failure in young adults is associated with high mortality: a contemporary population-level analysis

Background: Data on young patients with heart failure (HF) are sparse. We examined the characteristics, healthcare utilization and survival of younger versus older patients with HF. Methods: Analysis of linked administrative databases in Alberta, Canada. 34,548 patients with first hospitalization for HF as principal diagnosis were identified from 2002 to 2014. Patients were stratified into four age groups: 20-44, 45-54, 55-64, and ≥65 years. Results: Of the 34548 patients, 496 (1.4%), 1319 (3.8%), 3359 (9.7%) and 29374 (85%) patients were aged 20-44, 45-54, 55-64 and ≥65 years, respectively. Incidence of HF hospitalization decreased over time among patients ≥65 years, and increased among men aged 20 – 64 years. In the year following the index HF hospitalization, younger compared to older patients were less likely to present to the emergency department (ED) (e.g. 67.2% of those aged 20-44 years vs. 74.8% of those aged ≥65 years) or be hospitalized: for any reason (48.5% vs. 61.2%), cardiovascular causes (28.6% vs. 34.4%), or HF (14.8% vs. 23.6%). Mortality rates were lower in younger patients aged 20-44 years, but still substantial: 3.9%, 12.4%, and 27.7% at 30 days, 1 year, and 5 years respectively. Conclusions: Although young patients, especially those <45 years of age, accounted for a small proportion of the total population, adverse events were frequent, with half of the younger patients being readmitted, two thirds presenting to an ED, and over 10% dying within a year