A multi-scale, multi-wavelength source extraction method: getsources

We present a multi-scale, multi-wavelength source extraction algorithm called getsources. Although it has been designed primarily for use in the far-infrared surveys of Galactic star-forming regions with Herschel, the method can be applied to many other astronomical images. Instead of the traditional approach of extracting sources in the observed images, the new method analyzes fine spatial decompositions of original images across a wide range of scales and across all wavebands. It cleans those single-scale images of noise and background, and constructs wavelength-independent single-scale detection images that preserve information in both spatial and wavelength dimensions. Sources are detected in the combined detection images by following the evolution of their segmentation masks across all spatial scales. Measurements of the source properties are done in the original background-subtracted images at each wavelength; the background is estimated by interpolation under the source footprints and overlapping sources are deblended in an iterative procedure. In addition to the main catalog of sources, various catalogs and images are produced that aid scientific exploitation of the extraction results. We illustrate the performance of getsources on Herschel images by extracting sources in sub-fields of the Aquila and Rosette star-forming regions. The source extraction code and validation images with a reference extraction catalog are freely available.Comment: 31 pages, 27 figures, to be published in Astronomy & Astrophysic

Plastic shrinkage cracking of concrete - Roles of osmotic suction

Plastic shrinkage cracking of concrete occurs when the stresses arising in the concrete, due to a combination of suction and restraints of deformation such as reinforcement or formwork, equal its strength. However, three different types of suctions should be distinguished, namely total, matric and osmotic suctions. Although the total suction comprises matric and osmotic suctions, it is often used interchangeably with matric suction, with the underlying unconfirmed assumption that either the osmotic suction or its effect is negligible. In this paper, after a discussion of the pore moisture suctions and strength of unsaturated early-age concrete, experimental investigations of the suctions arising in, and the tensile strength and shear strength of, fly ash mixed with solutions of different osmotic suctions are described. It was found that osmotic suction has negligible effect on the shear and tensile strength, and hence, by inference, the inter-particle stresses in the fly ash mixture and early-age concrete. This strongly suggests that the role played by osmotic suction in the plastic shrinkage cracking of concrete is minimal and, accordingly, justifies the focus of earlier researchers on matric suction only

Varying Fine Structure Constant and Black Hole Physics

Recent astrophysical observations suggest that the value of fine structure constant $\alpha=e^2/\hbar c$ may be slowly increasing with time. This may be due to an increase of $e$ or a decrease of $c$, or both. In this article, we argue from model independent considerations that this variation should be considered adiabatic. Then, we examine in detail the consequences of such an adiabatic variation in the context of a specific model of quantized charged black holes. We find that the second law of black hole thermodynamics is obeyed, regardless of the origin of the variation, and that interesting constraints arise on the charge and mass of black holes. Finally, we estimate the work done on a black hole of mass $M$ due to the proposed $\alpha$ variation.Comment: 7 Pages, Revtex. Reference added, minor changes. Version to appear in Class. Quant. Gra

New Models for Wolf-Rayet and O Star Populations in Young Starbursts

Using the latest stellar evolution models, theoretical stellar spectra, and a compilation of observed emission line strengths from Wolf-Rayet (WR) stars, we construct evolutionary synthesis models for young starbursts. We explicitly distinguish between the various WR subtypes (WN, WC, WO), and we treat O and Of stars separately. We provide detailed predictions of UV and optical emission line strengths for both the WR stellar lines and the major nebular hydrogen and helium emission lines, as a function of several input parameters related to the starburst episode. We also derive the theoretical frequency of WR-rich starbursts. We then discuss: nebular HeII 4686 emission, the contribution of WR stars to broad Balmer line emission, techniques used to derive the WR and O star content from integrated spectra, and explore the implications of the formation of WR stars through mass transfer in close binary systems in instantaneous bursts. The observational features predicted by our models allow a detailed quantitative determination of the massive star population in a starburst region (particularly in so-called "WR galaxies") from its integrated spectrum and provide a means of deriving the burst properties (e.g., duration, age) and the parameters of the initial mass function of young starbursts. (Abridged abstract)Comment: Accepted by ApJ Supplements. LaTeX using aasmp4, psfigs macros. 49 pages including 23 figures. Paper (full, or text/figures separated) and detailed model results available at http://www.stsci.edu/ftp/science/starburst/sv97.htm

Measuring Polarization with DASI

We describe an experiment to measure the polarization of the Cosmic Microwave Background (CMB) with the Degree Angular Scale Interferometer (DASI), a compact microwave interferometer optimized to detect CMB anisotropy at multipoles 140 to 900. The telescope has operated at the Amundsen-Scott South Pole research station since 2000 January. The telescope was retrofit as a polarimeter during the 2000--2001 austral summer, and throughout the 2001 and 2002 austral winters has made observations of the CMB with sensitivity to all four Stokes parameters. The telescope performance has been extensively characterized through observations of artificial sources, the Moon, and polarized and unpolarized Galactic sources. In 271 days of observation, DASI has differenced the CMB fluctuations in two fields to an rms noise level of 2.8 uK.Comment: 12 pages, 9 figures, submitted to the Astrophysical Journa

Evolution of the Scale Factor with a Variable Cosmological Term

Evolution of the scale factor a(t) in Friedmann models (those with zero pressure and a constant cosmological term Lambda) is well understood, and elegantly summarized in the review of Felten and Isaacman [Rev. Mod. Phys. 58, 689 (1986)]. Developments in particle physics and inflationary theory, however, increasingly indicate that Lambda ought to be treated as a dynamical quantity. We revisit the evolution of the scale factor with a variable Lambda-term, and also generalize the treatment to include nonzero pressure. New solutions are obtained and evaluated using a variety of observational criteria. Existing arguments for the inevitability of a big bang (ie., an initial state with a=0) are substantially weakened, and can be evaded in some cases with Lambda_0 (the present value of Lambda) well below current experimental limits.Comment: 29 pages, 12 figures (not included), LaTeX, uses Phys Rev D style files (revtex.cls, revtex.sty, aps.sty, aps10.sty, prabib.sty). To appear in Phys Rev

Predictors of loss to follow up among patients with type 2 diabetes mellitus attending a private not for profit urban diabetes clinic in Uganda : a descriptive retrospective study

BACKGROUND: Although the prevalence of type 2 diabetes mellitus is increasing in Uganda, data on loss to follow up (LTFU) of patients in care is scanty. We aimed to estimate proportions of patients LTFU and document associated factors among patients attending a private not for profit urban diabetes clinic in Uganda. METHODS: We conducted a descriptive retrospective study between March and May 2017. We reviewed 1818 out-patient medical records of adults diagnosed with type 2 diabetes mellitus registered between July 2003 and September 2016 at St. Francis Hospital - Nsambya Diabetes clinic in Uganda. Data was extracted on: patients' registration dates, demographics, socioeconomic status, smoking, glycaemic control, type of treatment, diabetes mellitus complications and last follow-up clinic visit. LTFU was defined as missing collecting medication for six months or more from the date of last clinic visit, excluding situations of death or referral to another clinic. We used Kaplan-Meier technique to estimate time to defaulting medical care after initial registration, log-rank test to test the significance of observed differences between groups. Cox proportional hazards regression model was used to determine predictors of patients' LTFU rates in hazard ratios (HRs). RESULTS: Between July 2003 and September 2016, one thousand eight hundred eighteen patients with type 2 diabetes mellitus were followed for 4847.1 person-years. Majority of patients were female 1066/1818 (59%) and 1317/1818 (72%) had poor glycaemic control. Over the 13 years, 1690/1818 (93%) patients were LTFU, giving a LTFU rate of 34.9 patients per 100 person-years (95%CI: 33.2-36.6). LTFU was significantly higher among males, younger patients (< 45 years), smokers, patients on dual therapy, lower socioeconomic status, and those with diabetes complications like neuropathy and nephropathy. CONCLUSION: We found high proportions of patients LTFU in this diabetes clinic which warrants intervention studies targeting the identified risk factors and strengthening follow up of patients

How to screen for non-adherence to antihypertensive therapy

The quality of assessment of non-adherence to treatment in hypertensive is poor. Within this review, we discuss the different methods used to assess adherence to blood-pressure-lowering medications in hypertension patients. Subjective reports such as physicians’ perceptions are inaccurate, and questionnaires completed by patients tend to overreport adherence and show a low diagnostic specificity. Indirect objective methods such as pharmacy database records can be useful, but they are limited by the robustness of the recorded data. Electronic medication monitoring devices are accurate but usually track adherence to only a single medication and can be expensive. Overall, the fundamental issue with indirect objective measures is that they do not fully confirm ingestion of antihypertensive medications. Detection of antihypertensive medications in body fluids using liquid chromatography–tandem mass spectrometry is currently, in our view, the most robust and clinically useful method to assess non-adherence to blood-pressure-lowering treatment. It is particularly helpful in patients presenting with resistant, refractory or uncontrolled hypertension despite the optimal therapy. We recommend using this diagnostic strategy to detect non-adherence alongside a no-blame approach tailoring support to address the perceptions (e.g. beliefs about the illness and treatment) and practicalities (e.g. capability and resources) influencing motivation and ability to adhere

Expression of hypoxia-inducible factor 1 alpha and its downstream targets in fibroepithelial tumors of the breast

INTRODUCTION: Hypoxia-inducible factor 1 (HIF-1) alpha and its downstream targets carbonic anhydrase IX (CAIX) and vascular endothelial growth factor (VEGF) are key factors in the survival of proliferating tumor cells in a hypoxic microenvironment. We studied the expression and prognostic relevance of HIF-1α and its downstream targets in phyllodes tumors and fibroadenomas of the breast. METHODS: The expression of HIF-1α, CAIX, VEGF and p53 was investigated by immunohistochemistry in a group of 37 primary phyllodes tumors and 30 fibroadenomas with known clinical follow-up. The tumor microvasculature was visualized by immunohistochemistry for CD31. Proliferation was assessed by Ki67 immunostaining and mitotic counts. Being biphasic tumors, immunoquantification was performed in the stroma and epithelium. RESULTS: Only two fibroadenomas displayed low-level stromal HIF-1α reactivity in the absence of CAIX expression. Stromal HIF-1α expression was positively correlated with phyllodes tumor grade (P = 0.001), with proliferation as measured by Ki67 expression (P < 0.001) and number of mitoses (P < 0.001), with p53 accumulation (P = 0.003), and with global (P = 0.015) and hot-spot (P = 0.031) microvessel counts, but not with CAIX expression. Interestingly, concerted CAIX and HIF-1α expression was frequently found in morphologically normal epithelium of phyllodes tumors. The distance from the epithelium to the nearest microvessels was higher in phyllodes tumors as compared with in fibroadenomas. Microvessel counts as such did not differ between fibroadenomas and phyllodes tumors, however. High expression of VEGF was regularly found in both tumors, with only a positive relation between stromal VEGF and grade in phyllodes tumors (P = 0.016). Stromal HIF-1α overexpression in phyllodes tumors was predictive of disease-free survival (P = 0.032). CONCLUSION: These results indicate that HIF-1α expression is associated with diminished disease-free survival and may play an important role in stromal progression of breast phyllodes tumors. In view of the absence of stromal CAIX expression in phyllodes tumors, stromal upregulation of HIF-1α most probably arises from hypoxia-independent pathways, with p53 inactivation as one possible cause. In contrast, coexpression of HIF-1α and CAIX in the epithelium in phyllodes tumors points to epithelial hypoxia, most probably caused by relatively distant blood vessels. On the other hand, HIF-1α and CAIX seem to be of minor relevance in breast fibroadenomas