A Model for the Analysis of Caries Occurrence in Primary Molar Tooth Surfaces

Recently methods of caries quantification in the primary dentition have moved away from summary ‘whole mouth’ measures at the individual level to methods based on generalised linear modelling (GLM) approaches or survival analysis approaches. However, GLM approaches based on logistic transformation fail to take into account the time-dependent process of tooth/surface survival to caries. There may also be practical difficulties associated with casting parametric survival-based approaches in a complex multilevel hierarchy and the selection of an optimal survival distribution, while non-parametric survival methods are not generally suitable for the assessment of supplementary information recorded on study participants. In the current investigation, a hybrid semi-parametric approach comprising elements of survival-based and GLM methodologies suitable for modelling of caries occurrence within fixed time periods is assessed, using an illustrative multilevel data set of caries occurrence in primary molars from a cohort study, with clustering of data assumed to occur at surface and tooth levels. Inferences of parameter significance were found to be consistent with previous parametric survival-based analyses of the same data set, with gender, socio-economic status, fluoridation status, tooth location, surface type and fluoridation status-surface type interaction significantly associated with caries occurrence. The appropriateness of the hierarchical structure facilitated by the hybrid approach was also confirmed. Hence the hybrid approach is proposed as a more appropriate alternative to primary caries modelling than non-parametric survival methods or other GLM-based models, and as a practical alternative to more rigorous survival-based methods unlikely to be fully accessible to most researchers

Spectacular X-ray tails, intracluster star formation and ULXs in A3627

We present the discovery of spectacular double X-ray tails associated with ESO137-001 and a possibly heated X-ray tail associated with ESO137-002, both late-type galaxies in the closest rich cluster Abell 3627. A deep Chandra observation of ESO137-001 allows us for the first time to examine the spatial and spectral properties of such X-ray tails in detail. Besides the known bright tail that extends to ~ 80 kpc from ESO137-001, a fainter and narrower secondary tail with a similar length was surprisingly revealed. There is little temperature variation along both tails. We also identified six X-ray point sources as candidates of intracluster ULXs with L(0.3-10 keV) of up to 2.5x10^40 erg s^-1. Gemini spectra of intracluster HII regions downstream of ESO137-001 are also presented, as well as the velocity map of these HII regions that shows the imprint of ESO137-001's disk rotation. For the first time, we unambiguously know that active star formation can happen in the cold ISM stripped by ICM ram pressure and it may contribute a significant amount of the intracluster light. We also report the discovery of a 40 kpc X-ray tail of another late-type galaxy in A3627, ESO137-002. Its X-ray tail seems hot, ~ 2 keV (compared to ~ 0.8 keV for ESO137-001's tails). We conclude that the high pressure environment around these two galaxies is important for their bright X-ray tails and the intracluster star formation.Comment: ApJ in press, January 2010, v708, only several minor word changes, emulateapj5.sty, 24 pages, 11 color + 5 B/W figures (figure quality degraded) and 4 tables. The abstract has been abbreviated. A high-resolution PDF is available at: http://www.astro.virginia.edu/~ms4ar/eso137_p3.pd

A formally verified compiler back-end

This article describes the development and formal verification (proof of semantic preservation) of a compiler back-end from Cminor (a simple imperative intermediate language) to PowerPC assembly code, using the Coq proof assistant both for programming the compiler and for proving its correctness. Such a verified compiler is useful in the context of formal methods applied to the certification of critical software: the verification of the compiler guarantees that the safety properties proved on the source code hold for the executable compiled code as well

Calculations of collisions between cold alkaline earth atoms in a weak laser field

We calculate the light-induced collisional loss of laser-cooled and trapped magnesium atoms for detunings up to 50 atomic linewidths to the red of the ^1S_0-^1P_1 cooling transition. We evaluate loss rate coefficients due to both radiative and nonradiative state-changing mechanisms for temperatures at and below the Doppler cooling temperature. We solve the Schrodinger equation with a complex potential to represent spontaneous decay, but also give analytic models for various limits. Vibrational structure due to molecular photoassociation is present in the trap loss spectrum. Relatively broad structure due to absorption to the Mg_2 ^1Sigma_u state occurs for detunings larger than about 10 atomic linewidths. Much sharper structure, especially evident at low temperature, occurs even at smaller detunings due to of Mg_2 ^1Pi_g absorption, which is weakly allowed due to relativistic retardation corrections to the forbidden dipole transition strength. We also perform model studies for the other alkaline earth species Ca, Sr, and Ba and for Yb, and find similar qualitative behavior as for Mg.Comment: 20 pages, RevTex, 13 eps figures embedde

A Compiled Implementation of Strong Reduction

International audienceMotivated by applications to proof assistants based on dependent types, we develop and prove correct a strong reducer and β-equivalence checker for the λ-calculus with products, sums, and guarded fixpoints. Our approach is based on compilation to the bytecode of an abstract machine performing weak reductions on non-closed terms, derived with minimal modifications from the ZAM machine used in the Objective Caml bytecode interpreter, and complemented by a recursive "read back" procedure. An implementation in the Coq proof assistant demonstrates important speed-ups compared with the original interpreter-based implementation of strong reduction in Coq

Dust heating sources in galaxies: the case of M33 (HERM33ES)

Dust emission is one of the main windows to the physics of galaxies and to star formation as the radiation from young, hot stars is absorbed by the dust and reemitted at longer wavelengths. The recently launched Herschel satellite now provides a view of dust emission in the far-infrared at an unequaled resolution and quality up to 500 \mu m. In the context of the Herschel HERM33ES open time key project, we are studying the moderately inclined Scd local group galaxy M33 which is located only 840 kpc away. In this article, using Spitzer and Herschel data ranging from 3.6 \mu m to 500 \mu m, along with HI, H\alpha\ maps, and GALEX ultraviolet data we have studied the emission of the dust at the high spatial resolution of 150 pc. Combining Spitzer and Herschel bands, we have provided new, inclination corrected, resolved estimators of the total infrared brightness and of the star formation rate from any combination of these bands. The study of the colors of the warm and cold dust populations shows that the temperature of the former is, at high brightness, dictated by young massive stars but, at lower brightness, heating is taken over by the evolved populations. Conversely, the temperature of the cold dust is tightly driven by the evolved stellar populations.Comment: 29 pages, 12 figures, accepted for publication in A

Photoassociation spectroscopy of cold calcium atoms

Photoassociation spectroscopy experiments on 40Ca atoms close to the dissociation limit 4s4s 1S0 - 4s4p 1P1 are presented. The vibronic spectrum was measured for detunings of the photoassociation laser ranging from 0.6 GHz to 68 GHz with respect to the atomic resonance. In contrast to previous measurements the rotational splitting of the vibrational lines was fully resolved. Full quantum mechanical numerical simulations of the photoassociation spectrum were performed which allowed us to put constraints on the possible range of the calcium scattering length to between 50 a_0 and 300 a_0

Spitzer View of Young Massive Stars in the LMC HII Complexes. II. N159

The HII complex N159 in the Large Magellanic Cloud (LMC) is used to study massive star formation in different environments, as it contains three giant molecular clouds (GMCs) that have similar sizes and masses but exhibit different intensities of star formation. We identify candidate massive young stellar objects (YSOs) using infrared photometry, and model their SEDs to constrain mass and evolutionary state. Good fits are obtained for less evolved Type I, I/II, and II sources. Our analysis suggests that there are massive embedded YSOs in N159B, a maser source, and several ultracompact HII regions. Massive O-type YSOs are found in GMCs N159-E and N159-W, which are associated with ionized gas, i.e., where massive stars formed a few Myr ago. The third GMC, N159-S, has neither O-type YSOs nor evidence of previous massive star formation. This correlation between current and antecedent formation of massive stars suggests that energy feedback is relevant. We present evidence that N159-W is forming YSOs spontaneously, while collapse in N159-E may be triggered. Finally, we compare star formation rates determined from YSO counts with those from integrated H-alpha and 24 micron luminosities and expected from gas surface densities. Detailed dissection of extragalactic GMCs like the one presented here is key to revealing the physics underlying commonly used star formation scaling laws.Comment: 60 pages, 11 figures. Accepted for publication in Astrophysical Journa

ACCESS II: A Complete Census of Star Formation in the Shapley Supercluster - UV and IR Luminosity Functions

We present panoramic Spitzer/MIPS mid- and far-infrared and GALEX ultraviolet imaging of the the most massive and dynamically active system in the local Universe, the Shapley supercluster at z=0.048, covering the 5 clusters which make up the supercluster core. We combine these data with existing spectroscopic data from 814 confirmed supercluster members to produce the first study of a local rich cluster including both ultraviolet and infrared luminosity functions (LFs). This joint analysis allows us to produce a complete census of star-formation (both obscured and unobscured), extending down to SFRs~0.02-0.05Msun/yr, and quantify the level of obscuration of star formation among cluster galaxies, providing a local benchmark for comparison to ongoing and future studies of cluster galaxies at higher redshifts with Spitzer and Herschel. The GALEX NUV and FUV LFs obtained have steeper faint-end slopes than the local field population, due largely to the contribution of massive, quiescent galaxies at M_FUV>-16. The 24um and 70um galaxy LFs for the Shapley supercluster instead have shapes fully consistent with those obtained for the Coma cluster and for the local field galaxy population. This apparent lack of environmental dependence for the shape of the FIR luminosity function suggests that the bulk of the star-forming galaxies that make up the observed cluster infrared LF have been recently accreted from the field and have yet to have their star formation activity significantly affected by the cluster environment. We estimate a global SFR of 327 Msun/yr over the whole supercluster core, of which just ~20% is visible directly in the UV continuum and ~80% is reprocessed by dust and emitted in the infrared. The level of obscuration (L_IR/L_FUV) in star-forming galaxies is seen to increase linearly with L_K over two orders of magnitude in stellar mass.Comment: 19 pages, 17 figures. Accepted for publication in MNRA