Electronic spectroscopy of FUV-irradiated diamondoids: A combined experimental and theoretical study

Irradiation with high energy photons (10.2 - 11.8 eV) was applied to small diamondoids isolated in solid rare gas matrices at low temperature. The photoproducts were traced via UV absorption spectroscopy. We found that upon ionization the smallest of these species lose a peripheral H atom to form a stable closed-shell cation. This process is also likely to occur under astrophysical conditions for gas phase diamondoids and it opens the possibility to detect diamond-like molecules using their rotational spectrum since the dehydrogenated cations possess strong permanent dipole moments. The lowest-energy electronic features of these species in the UV were found to be rather broad, shifting to longer wavelengths with increasing molecular size. Calculations using time-dependent density functional theory support our experimental findings and extend the absorption curves further into the vacuum ultraviolet. The complete sigma - sigma* spectrum displays surprisingly strong similarities to meteoritic nanodiamonds containing 50 times more C atoms.Comment: 11 pages, 9 figures; published in The Astrophysical Journal; corrected minor mistakes compared to the published pape

Suppression of d-wave superconductivity in the checkerboard Hubbard model

Using a dynamical cluster quantum Monte Carlo approximation we investigate the d-wave superconducting transition temperature $T_c$ in the doped 2D repulsive Hubbard model with a weak inhomogeneity. The inhomogeneity is introduced in the hoppings \tp and $t$ in the form of a checkerboard pattern where $t$ is the hopping within a $2\times2$ plaquette and \tp is the hopping between the plaquettes. We find inhomogeneity suppresses $T_c$. The characteristic spin excitation energy and the strength of d-wave pairing interaction decrease with decreasing $T_c$ suggesting a strong correlation between these quantities.Comment: Five pages, four figures. Accepted for Phys. Rev. B (Rapid Com.

The Spatial Distribution of Dust and Stellar Emission of the Magellanic Clouds

We study the emission by dust and stars in the Large and Small Magellanic Clouds, a pair of low-metallicity nearby galaxies, as traced by their spatially resolved spectral energy distributions (SEDs). This project combines Herschel Space Observatory PACS and SPIRE far-infrared photometry with other data at infrared and optical wavelengths. We build maps of dust and stellar luminosity and mass of both Magellanic Clouds, and analyze the spatial distribution of dust/stellar luminosity and mass ratios. These ratios vary considerably throughout the galaxies, generally between the range $0.01\leq L_{\rm dust}/L_\ast\leq 0.6$ and $10^{-4}\leq M_{\rm dust}/M_\ast\leq 4\times10^{-3}$. We observe that the dust/stellar ratios depend on the interstellar medium (ISM) environment, such as the distance from currently or previously star-forming regions, and on the intensity of the interstellar radiation field (ISRF). In addition, we construct star formation rate (SFR) maps, and find that the SFR is correlated with the dust/stellar luminosity and dust temperature in both galaxies, demonstrating the relation between star formation, dust emission and heating, though these correlations exhibit substantial scatter.Comment: 15 pages, 18 figures; ApJ, in press; version published in the journal will have higher-resolution figure

Soft-core hyperon-nucleon potentials

A new Nijmegen soft-core OBE potential model is presented for the low-energy YN interactions. Besides the results for the fit to the scattering data, which largely defines the model, we also present some applications to hypernuclear systems using the G-matrix method. An important innovation with respect to the original soft-core potential is the assignment of the cut-off masses for the baryon-baryon-meson (BBM) vertices in accordance with broken SU(3)$_F$, which serves to connect the NN and the YN channels. As a novel feature, we allow for medium strong breaking of the coupling constants, using the $^3P_0$ model with a Gell-Mann--Okubo hypercharge breaking for the BBM coupling. We present six hyperon-nucleon potentials which describe the available YN cross section data equally well, but which exhibit some differences on a more detailed level. The differences are constructed such that the models encompass a range of scattering lengths in the $\Sigma N$ and $\Lambda N$ channels. For the scalar-meson mixing angle we obtained values $\theta_S=37$ to 40 degrees, which points to almost ideal mixing angles for the scalar $q\bar{q}$ states. The G-matrix results indicate that the remarkably different spin-spin terms of the six potentials appear specifically in the energy spectra of $\Lambda$ hypernuclei.Comment: 37 pages, 4 figure

Equivalence of Nonstatic Two-Pion-Exchange Nucleon-Nucleon Potentials

Off-shell aspects of the one-pion-exchange potential and their relationship to different forms of the nonstatic (subleading-order) chiral two-pion-exchange nucleon-nucleon potential are discussed. Various types of off-shell behavior are categorized and numerous examples are given. Recently derived potentials based on chiral approaches are supplemented by a rather general form of the two-pion-exchange potential derived using old-fashioned methods. The latter is closely related to a general form of one-pion-exchange relativistic corrections and nonstatic two-pion-exchange three-nucleon forces developed long ago.Comment: 16 pages, latex -- Phys. Rev. C (to appear) -- Published versio

Self-rated health in Pakistan: results of a national health survey

BACKGROUND: Self-rated health (SRH) is a robust predictor of mortality. In UK, migrants of South Asian descent, compared to native Caucasian populations, have substantially poorer SRH. Despite its validation among migrant South Asian populations and its popularity in developed countries as a useful public health tool, the SRH scale has not been used at a population level in countries in South Asia. We determined the prevalence of and risk factors for poor/fair SRH among individuals aged ≥15 years in Pakistan (n = 9442). METHODS: The National Health Survey of Pakistan was a cross-sectional population-based survey, conducted between 1990 and 1994, of 18 135 individuals aged 6 months and above; 9442 of them were aged ≥15 years. Our main outcome was SRH which was assessed using the question: "Would you say your health in general is excellent, very good, good, fair, or poor?" SRH was dichotomized into poor/fair, and good (excellent, very good, or good). RESULTS: Overall 65.1% respondents – 51.3 % men vs. 77.2 % women – rated their health as poor/fair. We found a significant interaction between sex and age (p < 0.0001). The interaction was due to the gender differences only in the ages 15–19 years, whereas poor/fair SRH at all older ages was more prevalent among women and increased at the same rate as it did among men. We also found province of dwelling, low or middle SES, literacy, rural dwelling and current tobacco use to be independently associated with poor/fair SRH. CONCLUSION: This is the first study reporting on poor/fair SRH at a population-level in a South Asian country. The prevalence of poor/fair health in Pakistan, especially amongst women, is one of the worst ever reported, warranting immediate attention. Further research is needed to explain why women in Pakistan have, at all ages, poorer SRH than men

Evaluating the accuracy of a functional SNP annotation system

Many common and chronic diseases are influenced at some level by genetic variation. Research done in population genetics, specifically in the area of single nucleotide polymorphisms (SNPs) is critical to understanding human genetic variation. A key element in assessing role of a given SNP is determining if the variation is likely to result in change in function. The SNP Integration Tool (SNPit) is a comprehensive tool that integrates diverse, existing predictors of SNP functionality, providing the user with information for improved association study analysis. To evaluate the SNPit system, we developed an alternative gold standard to measure accuracy using sensitivity and specificity. The results of our evaluation demonstrated that our alternative gold standard produced encouraging results

The youngest massive protostars in the Large Magellanic Cloud

We demonstrate the unique capabilities of Herschel to study very young luminous extragalactic young stellar objects (YSOs) by analyzing a central strip of the Large Magellanic Cloud obtained through the HERITAGE Science Demonstration Program. We combine PACS 100 and 160, and SPIRE 250, 350, and 500 microns photometry with 2MASS (1.25-2.17 microns) and Spitzer IRAC and MIPS (3.6-70 microns) to construct complete spectral energy distributions (SEDs) of compact sources. From these, we identify 207 candidate embedded YSOs in the observed region, ~40% never-before identified. We discuss their position in far-infrared color-magnitude space, comparing with previously studied, spectroscopically confirmed YSOs and maser emission. All have red colors indicating massive cool envelopes and great youth. We analyze four example YSOs, determining their physical properties by fitting their SEDs with radiative transfer models. Fitting full SEDs including the Herschel data requires us to increase the size and mass of envelopes included in the models. This implies higher accretion rates (greater than or equal to 0.0001 M_sun/yr), in agreement with previous outflow studies of high-mass protostars. Our results show that Herschel provides reliable longwave SEDs of large samples of high-mass YSOs; discovers the youngest YSOs whose SEDs peak in Herschel bands; and constrains the physical properties and evolutionary stages of YSOs more precisely than was previously possible.Comment: Main text: 4 pages, 3 figures, 1 table; Online material: 3 figures, 1 table; to appear in the A&A Herschel Special Issu

Finite Temperature Time-Dependent Effective Theory for the Phase Field in two-dimensional d-wave Neutral Superconductor

We derive finite temperature time-dependent effective actions for the phase of the pairing field, which are appropriate for a 2D electron system with both non-retarded d- and s-wave attraction. As for s-wave pairing the d-wave effective action contains terms with Landau damping, but their structure appears to be different from the s-wave case due to the fact that the Landau damping is determined by the quasiparticle group velocity v_{g}, which for d-wave pairing does not have the same direction as the non-interacting Fermi velocity v_{F}. We show that for d-wave pairing the Landau term has a linear low temperature dependence and in contrast to the s-wave case are important for all finite temperatures. A possible experimental observation of the phase excitations is discussed.Comment: 23 pages, RevTeX4, 10 EPS figures; final version to appear in PR

Investigation of the Exclusive 3He(e,e'pp)n Reaction

Cross sections for the 3He(e,e'pp)n reaction were measured over a wide range of energy and three- momentum transfer. At a momentum transfer q=375 MeV/c, data were taken at transferred energies omega ranging from 170 to 290 MeV. At omega=220 MeV, measurements were performed at three q values (305, 375, and 445 MeV/c). The results are presented as a function of the neutron momentum in the final-state, as a function of the energy and momentum transfer, and as a function of the relative momentum of the two-proton system. The data at neutron momenta below 100 MeV/c, obtained for two values of the momentum transfer at omega=220 MeV, are well described by the results of continuum-Faddeev calculations. These calculations indicate that the cross section in this domain is dominated by direct two-proton emission induced by a one-body hadronic current. Cross section distributions determined as a function of the relative momentum of the two protons are fairly well reproduced by continuum-Faddeev calculations based on various realistic nucleon-nucleon potential models. At higher neutron momentum and at higher energy transfer, deviations between data and calculations are observed that may be due to contributions of isobar currents.Comment: 14 pages, 1 table, 17 figure