866 research outputs found

    Production and stability of al and cu ultrafine particles in nanofluids

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    In this paper, a two step approach of synthesis of Al and Cu ultrafine particles by mechanical alloying and then dispersing them in base fluid to prepare nanofluid has been reported. Ultrafine powders were prepared by milling elemental Al and Cu powders for 50 h in a planetary mill. After 50 h of milling, particles size has been reduced to 500nm for Al and 400 nm for Cu. It is also found from transmission electron microscopy (TEM) that each particles consists of large number of crystallites of size around 10-15 nm. Aiming at the dispersion of nano-Al and Cu is regarded as the guide of heat transfer enhancement, the stability of Al and Cu particles in water were studied under different pH values. It has been found from Nanozeta meter that Al suspension is stable at pH 2.5 and 9.5, whereas Cu suspension is stable at pH 2.3 and 9.8

    Exploring Foundations of Time-Independent Density Functional Theory for Excited-States

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    Based on the work of Gorling and that of Levy and Nagy, density-functional formalism for many Fermionic excited-states is explored through a careful and rigorous analysis of the excited-state density to external potential mapping. It is shown that the knowledge of the ground-state density is a must to fix the mapping from an excited-state density to the external potential. This is the excited-state counterpart of the Hohenberg-Kohn theorem, where instead of the ground-state density the density of the excited-state gives the true many-body wavefunctions of the system. Further, the excited-state Kohn-Sham system is defined by comparing it's non-interacting kinetic energy with the true kinetic energy. The theory is demonstrated by studying a large number of atomic systems.Comment: submitted to J. Chem. Phy

    Tridimensional Regression for Comparing and Mapping 3D Anatomical Structures

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    Shape analysis is useful for a wide variety of disciplines and has many applications. There are many approaches to shape analysis, one of which focuses on the analysis of shapes that are represented by the coordinates of predefined landmarks on the object. This paper discusses Tridimensional Regression, a technique that can be used for mapping images and shapes that are represented by sets of three-dimensional landmark coordinates, for comparing and mapping 3D anatomical structures. The degree of similarity between shapes can be quantified using the tridimensional coefficient of determination (R2). An experiment was conducted to evaluate the effectiveness of this technique to correctly match the image of a face with another image of the same face. These results were compared to the R2 values obtained when only two dimensions are used and show that using three dimensions increases the ability to correctly match and discriminate between faces

    Deep GeMS/GSAOI near-infrared observations of N159W in the Large Magellanic Cloud

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    Aims. The formation and properties of star clusters at the edge of H II regions are poorly known, partly due to limitations in angular resolution and sensitivity, which become particularly critical when dealing with extragalactic clusters. In this paper we study the stellar content and star-formation processes in the young N159W region in the Large Magellanic Cloud. Methods. We investigate the star-forming sites in N159W at unprecedented spatial resolution using JHKs-band images obtained with the GeMS/GSAOI instrument on the Gemini South telescope. The typical angular resolution of the images is of 100 mas, with a limiting magnitude in H of 22 mag (90 percent completeness). Photometry from our images is used to identify candidate young stellar objects (YSOs) in N159W. We also determine the H-band luminosity function of the star cluster at the centre of the H II region and use this to estimate its initial mass function (IMF). Results. We estimate an age of 2 + or - 1 Myr for the central cluster, with its IMF described by a power-law with an index of gamma = - 1.05 + or - 0.2 , and with a total estimated mass of 1300 solar mass. We also identify 104 candidate YSOs, which are concentrated in clumps and subclusters of stars, principally at the edges of the H II region. These clusters display signs of recent and active star-formation such as ultra-compact H II regions, and molecular outflows. This suggests that the YSOs are typically younger than the central cluster, pointing to sequential star-formation in N159W, which has probably been influenced by interactions with the expanding H II bubble

    Correction of distortion for optimal image stacking in Wide Field Adaptive Optics: Application to GeMS data

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    The advent of Wide Field Adaptive Optics (WFAO) systems marks the beginning of a new era in high spatial resolution imaging. The newly commissioned Gemini South Multi-Conjugate Adaptive Optics System (GeMS) combined with the infrared camera Gemini South Adaptive Optics Imager (GSAOI), delivers quasi diffraction-limited images over a field of 2 arc-minutes across. However, despite this excellent performance, some variable residues still limit the quality of the analyses. In particular, distortions severely affect GSAOI and become a critical issue for high-precision astrometry and photometry. In this paper, we investigate an optimal way to correct for the distortion following an inverse problem approach. Formalism as well as applications on GeMS data are presented.Comment: 10 pages, 6 figure

    EHR-Based Care Coordination Performance Measures in Ambulatory Care

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    Describes electronic health record-based measures for assessing coordination in referrals, including information communicated with referral, communication to patient, and specialist report to primary care physician. Offers preliminary evaluation findings

    Star Formation and Young Population of the HII Complex Sh2-294

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    The Sh2-294 HII region ionized by a single B0V star features several infrared excess sources, a photodissociation region, and also a group of reddened stars at its border. The star formation scenario in the region seems to be quite complex. In this paper, we present follow-up results of Sh2-294 HII region at 3.6, 4.5, 5.8, and 8.0 microns observed with the Spitzer Space Telescope Infrared Array Camera (IRAC), coupled with H2 (2.12 microns) observation, to characterize the young population of the region and to understand its star formation history. We identified 36 young stellar object (YSO, Class I, Class II and Class I/II) candidates using IRAC color-color diagrams. It is found that Class I sources are preferentially located at the outskirts of the HII region and associated with enhanced H2 emission; none of them are located near the central cluster. Combining the optical to mid-infrared (MIR) photometry of the YSO candidates and using the spectral energy distribution fitting models, we constrained stellar parameters and the evolutionary status of 33 YSO candidates. Most of them are interpreted by the model as low-mass (< 4 solar masses) YSOs; however, we also detected a massive YSO (~9 solar masses) of Class I nature, embedded in a cloud of visual extinction of ~24 mag. Present analysis suggests that the Class I sources are indeed younger population of the region relative to Class II sources (age ~ 4.5 x 10^6 yr). We suggest that the majority of the Class I sources, including the massive YSOs, are second-generation stars of the region whose formation is possibly induced by the expansion of the HII region powered by a ~ 4 x 10^6 yr B0 main-sequence star.Comment: 12 pages, 7 figures, 2 tables. Accepted for publication in The Astrophysical Journa

    Young Stellar Population of the Bright-Rimmed Clouds BRC 5, BRC 7 and BRC 39

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    Bright-rimmed clouds (BRCs), illuminated and shaped by nearby OB stars, are potential sites of recent/ongoing star formation. Here we present an optical and infrared photometric study of three BRCs: BRC 5, BRC 7 and BRC 39 to obtain a census of the young stellar population, thereby inferring the star formation scenario, in these regions. In each BRC, the Class I sources are found to be located mostly near the bright rim or inside the cloud, whereas the Class II sources are preferentially outside, with younger sources closer to the rim. This provides strong support to sequential star formation triggered by radiation driven implosion due to the UV radiation. Moreover, each BRC contains a small group of young stars being revealed at its head, as the next-generation stars. In particular, the young stars at the heads of BRC 5 and BRC 7 are found to be intermediate/high mass stars, which, under proper conditions, may themselves trigger further star birth, thereby propagating star formation out to long distances.Comment: 30 pages, 7 Figures, 6 Tables, accepted for publication in Monthly Notices of the Royal Astronomical Societ

    Maternal and perinatal outcome in meconium stained amniotic fluid at term: a case control study

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    Background: Fetal well-being has traditionally been evaluated on the basis of fetal activity, FHR and presence of meconium in liquor in vertex presentation. Passage of meconium is considered physiological sign of fetal maturity on one hand and a sign of fetal distress and response to hypoxic insult on the other hand.Methods: Pregnant women of 37 - 42weeks gestation with singleton pregnancy and cephalic presentation admitted in labour ward of Mahatma Gandhi Medical College and Research Institute with clear or meconium stained amniotic fluid following spontaneous rupture or ARM were included in the study. Outcome measures were fetal heart rate abnormality, mode of delivery, Apgar score, NICU admission and diagnosis of MAS.Results: A total of 678 pregnant women were studied. Of them 226 had meconium stained and taken as study group. Rest 452 served as control group. The average gestational age of study group was 39.26±0.81. Abnormal FHR was observed in 56%.Spontaneous vaginal delivery was observed in 27.9% cases, instrumental delivery in 21.2% and caesarean section was 50.9% cases. Rate of low Apgar score 4.4% and it was two times higher in study group. NICU admission was observed in 46.7% cases of exposed group. Incidence of MAS in our study was 1.3%.Conclusions: In low resource settings where fetal scalp pH, and umbilical card lactate estimation facilities are not available, association of MSL with abnormal FHR can be taken as fetal distress and hence consideration of early operative intervention is necessary
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