957 research outputs found
No nearby counterparts to the moving objects in the Hubble Deep Field
Ibata et al (1999) have recently discovered faint, moving objects in the
Hubble Deep Field. The quantity, magnitudes and proper motions of these objects
are consistent with old white dwarfs making up the Galactic dark halo. We
review a number of ground-based proper motion surveys in which nearby dark halo
white dwarfs might be present, if they have the colours and absolute magnitudes
proposed. No such objects have been found, whereas we argue here that several
times more would be expected than in the Hubble Deep Field. We conclude it is
unlikely that hydrogen atmosphere white dwarfs make up a significant fraction
of the halo dark matter. No limits can be placed yet on helium atmosphere
dwarfs from optical searches.Comment: 7 pages, 4 figures, MNRAS LaTeX forma
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In-situ Washing by Sedimentation Method for Contaminated Sandy Soil
We propose a new method of in situ soil remediation called in situ washing by sedimentation (IWS), accomplished by injecting a high air-pressure into a mixture of saturated water-sandy soil at a certain depth (D) and hydraulically separating the soil particles based on their particle size and density. This physical segregation exploits the distribution of contaminant in the soil by physically separating a selected contaminant-rich fraction. For the in situ application, the physical segregation by sedimentation and on-site water wash treatment happen as an integrated process. The advantage of IWS that the washing and segregation processes take place simultaneously during the remediation process, quick, effective and cheap since there are no costs for excavation of contaminated soil from the site. The effect of soil-water ratio and diameter geometry of the column on the effectiveness of segregation by IWS was investigated. A series of laboratory test were conducted to optimize the soil water ratio for the best segregation process. Soil-water ratio 1:2 (v/v) was found to be optimum for particle segregation produced by IWS . The suitability of IWS for Polycyclic Aromatic Hydrocarbon (PAH) remediation, such as Napthalene, Phenantrene and Pyrene, were examined by batch sedimentation column experiment. The laboratory experiment was effective to produce a distinct size segregation of the contaminated soil into the coarse and fine fractions, as well as the wash water, indicating that a significant reduction in Napthalene, Phenantrene and Pyrene level (90%) may be achieved. The experimental results show that the removal efficiencies depend on the initial concentration of PAH in the soil sample, the duration of washing and the addition of biosurfactant in the washing solution
PERENCANAAN STRUKTUR ATAS GEDUNG MEDIC CENTER RUMAH SAKIT MATA UNDAAN KOTA SURABAYA
Studi Perencanaan Struktur Atas Gedung Medic Center Rumah Sakit Mata Undaan Surabaya dalam penelitian ini menggunakan system rangka pemikul momen menengah (SRPMM) beton bertulang. Perhitungan – perhitungan yang dilakukan dalam penelitian ini disesuaikan dengan peraturan yang ada pada SNI 2847 - 2013, SNI 1726 - 2012 dan PPIUG 1983. Perencanaan yang dilakukan pada penelitian ini meliputi perhitungan komponen struktur yang ada pada bangunan tersebut yaitu antara lain pelat, balok dan kolom. Beban gempa pada struktur dihitung dengan metode respon spektra dan analisa beban static ekivalen sedangkan untuk analisa perhitungan gaya – gaya dalam pada komponen bangunan baik struktur primer maupun sekunder menggunakan bantuan program komputer SAP 2000 sebagai acuan perhitungan dan perencanaan. Material yang digunakan yaitu mutu beton sebesar 25 MPa, sedangkan untuk besi tulangan utama menggunakan mutu baja dengan tegangan leleh 320 Mpa dan 240 Mpa untuk besi tulangan geser
M Dwarfs from Hubble Space Telescope Star Counts. IV
We study a sample of about 1400 disk M dwarfs that are found in 148 fields
observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope and
162 fields observed with pre-repair Planetary Camera 1 (PC1), of which 95 of
the WFC2 fields are newly analyzed. The method of maximum likelihood is applied
to derive the luminosity function and the Galactic disk parameters. At first,
we use a local color-magnitude relation and a locally determined
mass-luminosity relation in our analysis. The results are consistent with those
of previous work but with considerably reduced statistical errors. These small
statistical errors motivate us to investigate the systematic uncertainties.
Considering the metallicity gradient above the Galactic plane, we introduce a
modified color-magnitude relation that is a function of Galactic height. The
resultant M dwarf luminosity function has a shape similar to that derived using
the local color-magnitude relation but with a higher peak value. The peak
occurs at and the luminosity function drops sharply toward . We then apply a height-dependent mass-luminosity function
interpolated from theoretical models with different metallicities to calculate
the mass function. Unlike the mass function obtained using local relations,
which has a power-law index , the one derived from the
height-dependent relations tends to be flat (). The resultant
local surface density of disk M dwarfs (12.2 +/- 1.6 M_sun pc^{-2}) is somewhat
smaller than the one obtained using local relations (14.3 +/- 1.3 M_sun
pc^{-2}). Our measurement favors a short disk scale length, H = 2.75 +/- 0.16
(statistical) +/- 0.25 (systematic) kpc.Comment: 20 pages, 10 ps figures, accepted for publication in Ap
Modeling of Charge Transfer Inefficiency in a CCD with High Speed Column Parallel Readout
Charge Coupled Devices (CCDs) have been successfully used in several high
energy physics experiments over the past two decades. Their high spatial
resolution and thin sensitive layers make them an excellent tool for studying
short-lived particles. The Linear Collider Flavour Identification (LCFI)
collaboration is developing Column-Parallel CCDs (CPCCDs) for the vertex
detector of a future Linear Collider. The CPCCDs can be read out many times
faster than standard CCDs, significantly increasing their operating speed. An
Analytic Model has been developed for the determination of the charge transfer
inefficiency (CTI) of a CPCCD. The CTI values determined with the Analytic
Model agree largely with those from a full TCAD simulation. The Analytic Model
allows efficient study of the variation of the CTI on parameters like readout
frequency, operating temperature and occupancy.Comment: 5 pages, 13 figures, presented on behalf of the LCFI Collaboration,
proceedings IEEE 2008 Nuclear Science Symposium, Dresden, Germany, and 11th
Topical Seminar on Innovative Particle and Radiation Detectors (IPRD08) 2008,
Siena, Ital
M Dwarfs from Hubble Space Telescope Star Counts. V. The I-band Luminosity Function
We derive the disk I-band luminosity function from the Zheng et al. sample of
\~1400 disk M dwarfs observed with the Hubble Space Telescope. We adopt a
Galactic-height-dependent color-magnitude relation to account for the
metallicity gradient above the Galactic plane. The resultant I-band luminosity
function peaks at M_I~9.5 and drops sharply toward M_I~10.5.Comment: 2 pages, 1 eps figure, submitted to Ap
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Context, governance, associational trust and HRM: diversity and commonalities
This study explores how HRM and trust are inter-related, and what this means for how we understand HRM under different varieties of capitalism. We explore the direct impact of different indicators of societal trust on intra-organizational HRM practice, using a large-scale
internationally comparative survey evidence. We find that countries with high levels of associational trust, such as the Nordic social democracies, are generally associated with better communication and co-determination over the setting of the employment contract. The converse was true for countries with lower levels of associational trust, such as the liberal market economies. We failed to encounter any significant effects of multinationality or
country of origin in the case of MNCs; they did not differ significantly from their domestic peers when it came to the relationship between country of domicile levels of associational trust and HRM practice. We draw out the implications for theory and practice
Optimal timing of primaquine to reduce Plasmodium falciparum gametocyte carriage when co-administered with artemether-lumefantrine.
BACKGROUND: Primaquine is an important gametocytocidal drug that is combined with conventional malaria treatment for prevention of Plasmodium falciparum malaria transmission. Primaquine has been administered together on the first or the last day of conventional treatment but the impact of primaquine timing has never been examined. This study aimed to assess safety, efficacy and optimal timing of single full-dose (0.75 mg/kg) primaquine when added to a standard 6-dose regimen of artemether-lumefantrine (AL). METHODS: In an individual-level randomized controlled trial, enrolled participants who were G6PD normal and had uncomplicated P. falciparum malaria were randomly assigned to receive: AL only; AL and a single 0.75 mg/kg primaquine dose on the first day of AL (day 1); or AL and single 0.75 mg//kg primaquine on the last day of AL (day 3). On days 2, 3, 4, 8, 11 and 15, gametocytes were assessed and quantified by microscope and quantitative nuclear acid sequence based quantification (QT-NASBA). RESULTS: Overall, 111 participants aged between 3 and 17 years were randomly allocated to receive AL only (36) or combined with primaquine on day 1 (38), or primaquine on day 3 (37). Day 4 gametocyte prevalence in AL?+?day 1 primaquine was half the level seen in either AL?+?day 3 primaquine or AL only arm (11% [4/35] vs 26% [8/31] and 27% [8/30], respectively) albeit not statistically significant. A similar trend of lower gametocyte in the AL?+?day 1 primaquine verses AL?+?day 3 primaquine or AL only arm was observed in mean gametocyte density. Mean (sd) haemoglobin level in AL?+?day 3 primaquine arm recovered from -0.42(1.2) g/dl on day 2 to 0.35 (1.5) g/dl on day 15 of follow up. This was not the case in AL only and AL?+?day 1 primaquine arms during the same follow-up period, although the difference was not statistically significant (p?=?318). No serious adverse events reported in the study. Across arms, 23% (26/111) of participants reported a total of 31 mild adverse events and the difference was not statistically significant (p?=?0.477). CONCLUSION: Primaquine administration on the first day of AL is well tolerated and as safe as later administration. Whilst the World Health Organization currently recommends a lower dose of primaquine (0.25 mg/kg), the findings are supportive of early primaquine administration when combined with artemisinin-combination therapy. ClinicalTrials.gov Registration NCT01906788
1,3-Di-4-pyridylpropane–4,4′-oxydibenzoic acid (1/1)
The hydrothermal reaction of Cd(NO3)2·4H2O, 1,3-di-4-pyridylpropane (BPP) and 4,4′-oxydibenzoic acid (OBA) led to the formation of the title compound, C13H14N2·C14H10O5. The asymmetric unit consists of one molecule of OBA and one of BPP. In the OBA molecule, one COOH group is nearly planar with its attached benzene ring [dihedral angle = 0.9 (1)°], while the other COOH group is slightly twisted with a dihedral angle of 10.8 (3)°. The carboxyl groups form strong intermolecular O—H⋯N hydrogen bonds with N atoms of the pyridine rings in BPP, linking the molecules into zigzag chains
Broadband UBVRI Photometry of Horizontal-Branch and Metal-Poor Candidates from the HK and Hamburg/ESO Surveys. I
We report broadband UBV and/or BVRI CCD photometry for a total of 1857 stars
in the thick-disk and halo populations of the Galaxy. The majority of our
targets were selected as candidate field horizontal-branch or other A-type
stars (FHB/A, N = 576), or candidate low-metallicity stars (N = 1221), from the
HK and Hamburg/ESO objective-prism surveys. Similar data for a small number of
additional stars from other samples are also reported.
These data are being used for several purposes. In the case of the FHB/A
candidates they are used to accurately separate the lower-gravity FHB stars
from various higher-gravity A-type stars, a subsample that includes the
so-called Blue Metal Poor stars, halo and thick-disk blue stragglers,
main-sequence A-type dwarfs, and Am and Ap stars. These data are also being
used to derive photometric distance estimates to high-velocity hydrogen clouds
in the Galaxy and for improved measurements of the mass of the Galaxy.
Photometric data for the metal-poor candidates are being used to refine
estimates of stellar metallicity for objects with available medium-resolution
spectroscopy, to obtain distance estimates for kinematic analyses, and to
establish initial estimates of effective temperature for analysis of
high-resolution spectroscopy of the stars for which this information now
exists.Comment: 22 pages, including 3 figures, 5 tables, and two ascii files of full
data, accepted for publication in the Astrophysical Journal (Supplements
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