Studies of the structure and growth mode of dotriacontane films by synchrotron x-ray scattering and molecular dynamics simulations

doi: 10.1088/0953-8984/16/29/005We report on synchrotron x-ray scattering experiments and molecular dynamics simulations of the structure and growth mode of dotriacontane (n-C32H66 or C32) films adsorbed on Ag(111) and SiO2-coated Si(100) substrates. On the SiO2 surface, the x-ray measurements confirm a structural model of the solid film inferred from high-resolution ellipsometry measurements in which one or two layers of C32 adsorb with the long axis of the molecule oriented parallel to the interface followed by a monolayer in which the molecules have a perpendicular orientation. At higher C32 coverages, preferentially oriented bulk particles nucleate, consistent with a Stranski-Krastanov growth mode. On the Ag(111) surface, we again observe one or two layers of the 'parallel' film but no evidence of the perpendicular monolayer before nucleation of the preferentially oriented bulk particles. We compare the experimentally observed structures with molecular dynamics simulations of a multilayer film of the homologous C24 molecule.This work was support by US National Science Foundation under Grant Nos. DMR-9802476 and DMR-0109057. The Midwest Universities Collaborative Access Team (MUCAT) sector at the Advanced Photon Source (APS) is supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), through Ames Laboratory under ContractNo.W-7405-Eng-82. Use of the APS was supported by the DOE BES under Contract No. W-31-109-ENG-38

Extension of internationalisation models: drivers and processes for the globalisation of product development – a comparison of Danish and Chinese engineering firms

This paper develops an extension to established production- and supply chain management focused internationalisation models. It applies explorative case studies in Danish and Chinese engineering firms to discover how the globalisation process of product development differs from Danish and Chinese perspectives. The paper uses internationalisation and global product development theory to explain similarities and differences in the approaches. Grounded in case study results, a new model for internationalisation is proposed. The new model expands the internationalisation process model to include steps of product development and collaborative distributed development beyond sourcing, sales and production elements. The paper then provides propositions for how to further develop the suggested model, and how western companies can learn from the Chinese approaches, and globalise their product development activities from the front end of the value chain rather than from the back-end

The violent past of Cygnus X-2

Cygnus X-2 appears to be the descendant of an intermediate-mass X-ray binary (IMXB). Using Mazzitelli's (1989) stellar code we compute detailed evolutionary sequences for the system and find that its prehistory is sensitive to stellar input parameters, in particular the amount of core overshooting during the main-sequence phase. With standard assumptions for convective overshooting a case B mass transfer starting with a 3.5 M_sun donor star is the most likely evolutionary solution for Cygnus X-2. This makes the currently observed state rather short-lived, of order 3 Myr, and requires a formation rate > 1e-7 - 1e-6 per yr of such systems in the Galaxy. Our calculations show that neutron star IMXBs with initially more massive donors (> 4 M_sun) encounter a delayed dynamical instability; they are unlikely to survive this rapid mass transfer phase. We determine limits for the age and initial parameters of Cygnus X-2 and calculate possible dynamical orbits of the system in a realistic Galactic potential, given its observed radial velocity. We find trajectories which are consistent with a progenitor binary on a circular orbit in the Galactic plane inside the solar circle that received a kick velocity < 200 km/s at the birth of the neutron star. The simulations suggests that about 7% of IMXBs receiving an arbitrary kick velocity from a standard kick velocity spectrum would end up in an orbit similar to Cygnus X-2, while about 10% of them reach yet larger Galactocentric distances.Comment: 9 pages, 12 figures, accepted for publication in MNRA

Early Results from APOKASC

Asteroseismology and spectroscopy provide complementary constraints on the fundamental and chemical properties of stars. I describe the first results from APOKASC, a collaboration between the Kepler asteroseismic science consortium (KASC) and the SDSS-III APOGEE survey. These include (1) the first test of asteroseismic scaling relationships in the metal-poor regime using halo and thick disk stars identified in the APOKASC sample; and (2) the calibration of spectroscopic parameters using precise asteroseismic measurements of surface gravity. I also highlight future research avenues that are made possible by this unique sample of thousands of well-characterized red giant stars.Comment: Proc. of the workshop "Asteroseismology of stellar populations in the Milky Way" (Sesto, 22-26 July 2013), Astrophysics and Space Science Proceedings, (eds. A. Miglio, L. Girardi, P. Eggenberger, J. Montalban

Structural insight into SUMO chain recognition and manipulation by the ubiquitin ligase RNF4

The small ubiquitin-like modifier (SUMO) can form polymeric chains that are important signals in cellular processes such as meiosis, genome maintenance and stress response. The SUMO-targeted ubiquitin ligase RNF4 engages with SUMO chains on linked substrates and catalyses their ubiquitination, which targets substrates for proteasomal degradation. Here we use a segmental labelling approach combined with solution nuclear magnetic resonance (NMR) spectroscopy and biochemical characterization to reveal how RNF4 manipulates the conformation of the SUMO chain, thereby facilitating optimal delivery of the distal SUMO domain for ubiquitin transfer

A review of gene-drug interactions for nonsteroidal anti-inflammatory drug use in preventing colorectal neoplasia.

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to be effective chemopreventive agents for colorectal neoplasia. Polymorphisms in NSAID targets or metabolizing enzymes may affect NSAID efficacy or toxicity. We conducted a literature review to summarize current evidence of gene-drug interactions between NSAID use and polymorphisms in COX1, COX2, ODC, UGT1A6 and CYP2C9 on risk of colorectal neoplasia by searching OVID and PubMed. Of 134 relevant search results, thirteen investigated an interaction. One study reported a significant interaction between NSAID use and the COX1 Pro17Leu polymorphism (P=0.03) whereby the risk reduction associated with NSAID use among homozygous wild-type genotypes was not observed among NSAID users with variant alleles. Recent pharmacodynamic data support the potential for gene-drug interactions for COX1 Pro17Leu. Statistically significant interactions have also been reported for ODC (315G>A), UGT1A6 (Thr181Ala+Arg184Ser or Arg184Ser alone), and CYP2C9 (*2/*3). No statistically significant interactions have been reported for polymorphisms in COX2; however, an interaction with COX2 -765G>C approached significance (P=0.07) in one study. Among seven remaining studies, reported interactions were not statistically significant for COX1, COX2 and ODC gene polymorphisms. Most studies were of limited sample size. Definitions of NSAID use differed substantially between studies. The literature on NSAID-gene interactions to date is limited. Reliable detection of gene-NSAID interactions will require greater sample sizes, consistent definitions of NSAID use and evaluation of clinical trial subjects of chemoprevention studies

Establishing the accuracy of asteroseismic mass and radius estimates of giant stars. I. Three eclipsing systems at [Fe/H]~ -0.3 and the need for a large high-precision sample

We aim to establish and improve the accuracy level of asteroseismic estimates of mass, radius, and age of giant stars. This can be achieved by measuring independent, accurate, and precise masses, radii, effective temperatures and metallicities of long period eclipsing binary stars with a red giant component that displays solar-like oscillations. We measured precise properties of the three eclipsing binary systems KIC 7037405, KIC 9540226, and KIC 9970396 and estimated their ages be $5.3\pm0.5$, $3.1\pm0.6$, and $4.8\pm0.5$ Gyr. The measurements of the giant stars were compared to corresponding measurements of mass, radius, and age using asteroseismic scaling relations and grid modeling. We found that asteroseismic scaling relations without corrections to $\Delta\nu$ systematically overestimate the masses of the three red giants by 11.7%, 13.7%, and 18.9%, respectively. However, by applying theoretical correction factors $f_{\Delta\nu}$ according to Rodrigues et al. (2017), we reached general agreement between dynamical and asteroseismic mass estimates, and no indications of systematic differences at the precision level of the asteroseismic measurements. The larger sample investigated by Gaulme et al. (2016) showed a much more complicated situation, where some stars show agreement between the dynamical and corrected asteroseismic measures while others suggest significant overestimates of the asteroseismic measures. We found no simple explanation for this, but indications of several potential problems, some theoretical, others observational. Therefore, an extension of the present precision study to a larger sample of eclipsing systems is crucial for establishing and improving the accuracy of asteroseismology of giant stars.Comment: Accepted for publication in MNRAS, 17 page

Seismology of the Sun : Inference of Thermal, Dynamic and Magnetic Field Structures of the Interior

Recent overwhelming evidences show that the sun strongly influences the Earth's climate and environment. Moreover existence of life on this Earth mainly depends upon the sun's energy. Hence, understanding of physics of the sun, especially the thermal, dynamic and magnetic field structures of its interior, is very important. Recently, from the ground and space based observations, it is discovered that sun oscillates near 5 min periodicity in millions of modes. This discovery heralded a new era in solar physics and a separate branch called helioseismology or seismology of the sun has started. Before the advent of helioseismology, sun's thermal structure of the interior was understood from the evolutionary solution of stellar structure equations that mimicked the present age, mass and radius of the sun. Whereas solution of MHD equations yielded internal dynamics and magnetic field structure of the sun's interior. In this presentation, I review the thermal, dynamic and magnetic field structures of the sun's interior as inferred by the helioseismology.Comment: To be published in the proceedings of the meeting "3rd International Conference on Current Developments in Atomic, Molecular, Optical and Nano Physics with Applications", December 14-16, 2011, New Delhi, Indi

Highlights from the Pierre Auger Observatory

The Pierre Auger Observatory is the world's largest cosmic ray observatory. Our current exposure reaches nearly 40,000 km$^2$ str and provides us with an unprecedented quality data set. The performance and stability of the detectors and their enhancements are described. Data analyses have led to a number of major breakthroughs. Among these we discuss the energy spectrum and the searches for large-scale anisotropies. We present analyses of our X$_{max}$ data and show how it can be interpreted in terms of mass composition. We also describe some new analyses that extract mass sensitive parameters from the 100% duty cycle SD data. A coherent interpretation of all these recent results opens new directions. The consequences regarding the cosmic ray composition and the properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray Conference, Rio de Janeiro 201