Physical properties and behavior of high-performance concrete at high temperatures

The following report gives an overview of the TC program and some preliminary result

Spitzer Power-law AGN Candidates in the Chandra Deep Field-North

We define a sample of 62 galaxies in the Chandra Deep Field-North whose Spitzer IRAC SEDs exhibit the characteristic power-law emission expected of luminous AGN. We study the multiwavelength properties of this sample, and compare the AGN selected in this way to those selected via other Spitzer color-color criteria. Only 55% of the power-law galaxies are detected in the X-ray catalog at exposures of >0.5 Ms, although a search for faint emission results in the detection of 85% of the power-law galaxies at the > 2.5 sigma detection level. Most of the remaining galaxies are likely to host AGN that are heavily obscured in the X-ray. Because the power-law selection requires the AGN to be energetically dominant in the near- and mid-infrared, the power-law galaxies comprise a significant fraction of the Spitzer-detected AGN population at high luminosities and redshifts. The high 24 micron detection fraction also points to a luminous population. The power-law galaxies comprise a subset of color-selected AGN candidates. A comparison with various mid-infrared color selection criteria demonstrates that while the color-selected samples contain a larger fraction of the X-ray luminous AGN, there is evidence that these selection techniques also suffer from a higher degree of contamination by star-forming galaxies in the deepest exposures. Considering only those power-law galaxies detected in the X-ray catalog, we derive an obscured fraction of 68% (2:1). Including all of the power-law galaxies suggests an obscured fraction of < 81% (4:1).Comment: Accepted for publication in the Astrophysical Journal, 27 pages, 20 figures, 5 tables, version with high-resolution figures and online-only tables available at: http://frodo.as.arizona.edu/~jdonley/powerlaw

Keck-Nirspec Infrared OH Lines: Oxygen Abundances in Metal-Poor Stars Down to [Fe/H] = -2.9

Infrared OH lines at 1.5 - 1.7 um in the H band were obtained with the NIRSPEC high-resolution spectrograph at the 10m Keck Telescope for a sample of seven metal-poor stars. Detailed analyses have been carried out, based on optical high-resolution data obtained with the FEROS spectrograph at ESO. Stellar parameters were derived by adopting infrared flux method effective temperatures, trigonometric and/or evolutionary gravities and metallicities from FeII lines. We obtain that the sample stars with metallicities [Fe/H] < -2.2 show a mean oxygen abundance [O/Fe] ~ 0.54, for a solar oxygen abundance of epsilon(O) = 8.87, or [O/Fe] ~ 0.64 if epsilon(O) = 8.77 is assumed.Comment: To be published in ApJ 575 (August 10

Detection and imaging in strongly backscattering randomly layered media

Abstract. Echoes from small reflectors buried in heavy clutter are weak and difficult to distinguish from the medium backscatter. Detection and imaging with sensor arrays in such media requires filtering out the unwanted backscatter and enhancing the echoes from the reflectors that we wish to locate. We consider a filtering and detection approach based on the singular value decomposition of the local cosine transform of the array response matrix. The algorithm is general and can be used for detection and imaging in heavy clutter, but its analysis depends on the model of the cluttered medium. This paper is concerned with the analysis of the algorithm in finely layered random media. We obtain a detailed characterization of the singular values of the transformed array response matrix and justify the systematic approach of the filtering algorithm for detecting and refining the time windows that contain the echoes that are useful in imaging

Carbon-Enhanced Metal-Poor Stars. III. Main-Sequence Turn-Off Stars from the SDSS/SEGUE Sample

The chemical compositions of seven Carbon-Enhanced Metal-Poor (CEMP) turn-off stars are determined from high-resolution spectroscopy. Five of them are selected from the SDSS/SEGUE sample of metal-poor stars. The effective temperatures of these objects are all higher than 6000 K, while their metallicities, parametrized by [Fe/H], are all below -2. Six of our program objects exhibit high abundance ratios of barium ([Ba/H]> +1), suggesting large contributions of the products of former AGB companions via mass transfer across binary systems. Combining our results with previous studies provides a total of 20 CEMP main-sequence turn-off stars for which the abundances of carbon and at least some neutron-capture elements are determined. Inspection of the [C/H] ratios for this sample of CEMP turn-off stars show that they are generally higher than those of CEMP giants; their dispersion in this ratio is also smaller. We take these results to indicate that the carbon-enhanced material provided from the companion AGB star is preserved at the surface of turn-off stars with no significant dilution. In contrast, a large dispersion in the observed [Ba/H] is found for the sample of CEMP turn-off stars, suggesting that the efficiency of the s-process in very metal-poor AGB stars may differ greatly from star to star. Four of the six stars from the SDSS/SEGUE sample exhibit kinematics that are associated with membership in the outer-halo population, a remarkably high fraction.Comment: 45 pages, 10 figures, 10 tables, Astrophysical Journal, in pres

Wave nucleation rate in excitable systems in the low noise limit

Motivated by recent experiments on intracellular calcium dynamics, we study the general issue of fluctuation-induced nucleation of waves in excitable media. We utilize a stochastic Fitzhugh-Nagumo model for this study, a spatially-extended non-potential pair of equations driven by thermal (i.e. white) noise. The nucleation rate is determined by finding the most probable escape path via minimization of an action related to the deviation of the fields from their deterministic trajectories. Our results pave the way both for studies of more realistic models of calcium dynamics as well as of nucleation phenomena in other non-equilibrium pattern-forming processes

Data from: Children with type 1 diabetes who experienced a honeymoon phase had significantly lower LDL cholesterol 5 years after diagnosis

Manuscript abstract: Importance: Landmark studies showed that partial clinical remission in new-onset type 1 diabetes is associated with reduced prevalence of long-term complications, but early clinical indicators of this favorable outcome are poorly characterized. Aim: To determine if there were any differences in lipid parameters, especially LDL-cholesterol, between remitters and non-remitters 4 to 5 years after the diagnosis of type 1 diabetes after controlling for hemoglobin A1c, body mass index, and pubertal status. Subjects and Methods: A longitudinal retrospective cohort study of 123 subjects of mean age 11.9 ± 2.9 years, [male 11.7 ± 2.9 years, (n=55); female 12.0 ± 2.9 years, (n=68), p=0.60] with type 1 diabetes of 4-5 years duration. Anthropometric and biochemical data were collected at the 4th or 5th year after diagnosis in line with the American Diabetes Association recommendation to initiate screening for complications in children either at the beginning of puberty or 4-5 years after diagnosis. Puberty was defined by Tanner stages II-V. Partial clinical remission was defined by the gold-standard insulin-dose adjusted hemoglobin A1c (IDAA1c) of ≤9. Results: There were 44 (35.8%) remitters (age 13.0 ± 2.5y; male 52.3%). Both the total cholesterol and LDL-cholesterol were significantly lower in remitters compared to non-remitters: LDL-C: 78.8 ± 28.7 mg/dL vs. 91.6 ± 26.5 mg/dL, p=0.023; and total cholesterol: 151.5 ± 32.6 mg/dL vs. 167.0 ± 29.6 mg/dL, p=0.015. Other lipid fractions were similar between the groups. There were no differences between the groups for glycemic control, body mass index z score, thyroid function, celiac disease occurrence, or vitamin D status. Though a greater number of remitters were in puberty compared to non-remitters (86.4% vs. 60.8%, p=0.006), LDL-C concentration was similar in prepubertal remitters vs. non-remitters (p=0.93), but was significantly lower in remitters in puberty compared to non-remitters in puberty (p=0.018) after adjusting for age and duration of diabetes. Conclusions: Children with type 1 diabetes who underwent a honeymoon phase had significantly lower LDL cholesterol 5 years after diagnosis regardless of their age, glycemic control, adiposity, or pubertal status. This early divergence in lipidemia may explain the dichotomy in the prevalence of long-term complication in type 1 diabetes between remitters and non-remitters. It also offers a pathway for targeted lipid monitoring in type 1 diabetes, by establishing non-remission as a non-modifiable risk factor for vascular complication in type 1 diabetes

Partial clinical remission in type 1 diabetes: a comparison of the accuracy of total daily dose of insulin of \u3c0.3 units/kg/day to the gold standard insulin-dose adjusted hemoglobin A1c of ≤9 for the detection of partial clinical remission

BACKGROUND: It is unclear whether the gold standard test for the detection of partial clinical remission (PCR) in new-onset type 1 diabetes (T1D), the insulin-dose adjusted Hemoglobin A1c (IDAA1c) of ≤9, is superior to a new tool, total daily dose of insulin (TDD) of METHODS: A retrospective analysis of 204 subjects of ages 2-14 years, mean age 7.9±3.2 years, (male 7.8±3.4 years, [n=98]; female 7.9±3.0 years, [n=106], p=0.816) with new-onset T1D. Anthropometric and biochemical data were collected for the first 36 months of disease. PCR was defined by both IDAA1c≤9 and TDD RESULTS: There were 86 (42.2%) (age 9.1±3.0 years; male 57%) remitters by IDAA1c≤9 criterion, and 82 (40.2%) remitters (age 7.3±2.8 years) by TDD of CONCLUSIONS: There were no significant differences in the number of remitters, duration of PCR, or the time of peak remission defined by IDAA1c of ≤9 or TDD o