3,446 research outputs found
Temperature constraints on the coldest brown dwarf known WISE 0855-0714
Context. Nearby isolated planetary mass objects are beginning to be
discovered, but their individual properties are poorly constrained because
their low surface temperatures and strong molecular self-absorption make them
extremely faint.
Aims. We aimed to detect the near infrared emission of the coldest brown
dwarf (BD) found so far, WISE08550714, located 2.2 pc away, and to
improve its temperature estimate (T= 225-260 K) from a comparison
with state-of-the-art models of BD atmospheres.
Methods. We observed the field containing WISE0855-0714 with HAWK-I at the
VLT in the band. For BDs with T500\,K theoretical models
predict strong signal (or rather less molecular absorption) in this band.
Results. WISE0855-0714 was not detected in our Y-band images, thus placing an
upper limit on its brightness to Y>24.4 mag at 3- level, leading to
Y-[4.5]>10.5. Combining this limit with previous detections and upper limits at
other wavelengths, WISE08550714 is confirmed as the reddest BD detected,
further supporting its status as the coldest known brown dwarf. We applied
spectral energy distribution fitting with collections of models from two
independent groups for extremely cool BD atmospheres leading to an effective
temperature of T250\,K,.Comment: 4 pages, 4 figures. A&A letter Accepte
Semi-Inclusive Deep Inelastic Scattering processes from small to large P_T
We consider the azimuthal and dependence of hadrons produced in
unpolarized Semi-Inclusive Deep Inelastic Scattering (SIDIS) processes, within
the factorized QCD parton model. It is shown that at small values, P_T
\lsim 1 GeV/c, lowest order contributions, coupled to unintegrated (Transverse
Momentum Dependent) quark distribution and fragmentation functions, describe
all data. At larger values, P_T \gsim 1 GeV/c, the usual pQCD higher
order collinear contributions dominate. Having explained the full range
of available data, we give new detailed predictions concerning the azimuthal
and dependence of hadrons which could be measured in ongoing or planned
experiments by HERMES, COMPASS and JLab collaborations.Comment: 14 pages, 17 figures, uses revtex
Radiative Transfer in a Clumpy Universe: III. The Nature of Cosmological Ionizing Sources
The history of the transition from a neutral intergalactic medium (IGM) to
one that is almost fully ionized can reveal the character of cosmological
ionizing sources. We study the evolution of the volume filling factor of HII
and HeIII regions in a clumpy IGM, and discuss the implications for rival
reionization scenarios of the rapid decline in the space density of radio-loud
quasars and of the large population of star-forming galaxies recently observed
at z>3. The hydrogen component in a highly inhomogeneous universe is completely
reionized when the number of photons emitted above 1 ryd in one recombination
time equals the mean number of hydrogen atoms. If stellar sources are
responsible for keeping the IGM ionized at z=5, the rate of star formation at
this epoch must be comparable or greater than the one inferred from optical
observations of galaxies at z=3, and the mean metallicity per baryon in the
universe of order 1/500 solar. An early generation of stars in dark matter
halos with circular velocities v_circ=50 km/s, possibly one of the main source
of UV photons at high-z, could be detectable with the Next Generation Space
Telescope. Models in which the quasar emissivity declines rapidly at z>3
predict a late HeII reionization epoch, a feature that could explain the recent
detection of patchy HeII Lyman-alpha at z=2.9 by Reimers et al. (1997) and the
abrupt change observed by Songaila (1998) at about the same epoch of the
SiIV/CIV ratio, but appear unable to provide the required number of
hydrogen-ionizing photons at z=5.Comment: LaTeX, 29 pages, 5 figures, submitted to the Ap
Rifampicin: biotransformation study using the fungus Cunninghamella elegans and monitoring through UHPLC-MS
Drug biotransformation studies appear as an alternative to pharmacological investigations of metabolites, development of new drug candidates with reduced investment and most efficient production. The objective of this study was to evaluate the capacity of biotransformation of Rifampicin (RIF) by the filamentous fungus Cunninghamella elegans as a microbial model of mammalian metabolism. In 120 h, C. elegans transformed the drug into the following two metabolites: rifampicin quinone and novel metabolite. The products of rifampicin formed in vitro were monitored by HPLC-PDA, being identified through UHPLC–QTOF/MS. Metabolites were characterized according to their chromatographic profile, mass fragments and UV spectral data. The major metabolic pathways of rifampicin transformed by the fungus were oxidation, demethylation and mono-oxidation. The microbial transformation of RIF showed the potential of Cunninghamella species to produce RIF metabolites. This process can be used for a cost effective method for both known and unknown metabolite production
Kinematics of Interstellar Gas in Nearby UV-Selected Galaxies Measured with HST/STIS Spectroscopy
We measure Doppler shifts of interstellar absorption lines in HST/STIS
spectra of individual star clusters in nearby UV-selected galaxies. Values for
systemic velocities, which are needed to quantify outflow speeds, are taken
from the literature, and verified with stellar lines. We detect outflowing gas
in eight of 17 galaxies via low-ionization lines (e.g., CII, SiII, AlII), which
trace cold and/or warm gas. The starbursts in our sample are intermediate in
luminosity (and mass) to dwarf galaxies and luminous infrared galaxies (LIRGs),
and we confirm that their outflow speeds (ranging from -100 km/s to nearly -520
km/s with an accuracy of ~80 km/s) are intermediate to those previously
measured in dwarf starbursts and LIRGs. We do not detect the outflow in
high-ionization lines (such as CIV or SiIV); higher quality data will be needed
to empirically establish how velocities vary with the ionization state of the
outflow. We do verify that the low-ionization UV lines and optical NaI doublet
give roughly consistent outflow velocities solidifying an important link
between studies of galactic winds at low and high redshift. To obtain higher
signal-to-noise, we create a local average composite spectrum, and compare it
to the high-z Lyman Break composite spectrum. Surprisingly, the low-ionization
lines show similar outflow velocities in the two samples. We attribute this to
a combination of weighting towards higher luminosities in the local composite,
as well as both samples being on average brighter than the ``turnover''
luminosity in the v-SFR relation.Comment: 41 pages, 14 figures, accepted for publication in The Astrophysical
Journa
kHz Quasi-Periodic Oscillations in the low-mass X-ray binary 4U 0614+09
We report on a comprehensive analysis of the kilohertz (above 300 Hz)
quasi-periodic oscillations (kHz QPOs) detected from the neutron star low-mass
X-ray binary 4U0614+09 with the Rossi X-ray Timing Explorer (RXTE). With a much
larger data set than previously analyzed (all archival data from February 1996
up to October 2007), we first investigate the reality of the 1330 Hz QPO
reported by van Straaten et al. (2000). This QPO would be of particular
interest since it has the highest frequency reported for any source. A thorough
analysis of the same observation fails to confirm the detection. On the other
hand, over our extended data set, the highest QPO frequency we measure for the
upper kHz QPO is at about 1224 Hz; a value which is fully consistent with the
maximum values observed in similar systems. Second, we demonstrate that the
frequency dependence of the quality factor and amplitude of the lower and upper
kHz QPOs follow the systematic trends seen in similar systems (Barret et al.,
2006). In particular, 4U0614+09 shows a drop of the quality factor of the lower
kHz QPO above 700 Hz. If this is due to an approach to the innermost stable
circular orbit, it implies a neutron star mass of about 1.9 solar masses.
Finally, when analyzing the data over fixed durations, we have found a gap in
the frequency distribution of the upper QPO, associated with a local minimum of
its amplitude. A similar gap is not present in the distribution of the lower
QPO frequencies, suggesting some cautions when interpreting frequency ratio
distributions, based on the occurrence of the lower QPO only.Comment: 10 pages, 6 color figures, 2 tables, Accepted for publication in
MNRA
Community-Driven Methods for Open and Reproducible Software Tools for Analyzing Datasets from Atom Probe Microscopy
Atom probe tomography, and related methods, probe the composition and the three-dimensional architecture of materials. The software tools which microscopists use, and how these tools are connected into workflows, make a substantial contribution to the accuracy and precision of such material characterization experiments. Typically, we adapt methods from other communities like mathematics, data science, computational geometry, artificial intelligence, or scientific computing. We also realize that improving on research data management is a challenge when it comes to align with the FAIR data stewardship principles. Faced with this global challenge, we are convinced it is useful to join forces. Here, we report the results and challenges with an inter-laboratory call for developing test cases for several types of atom probe microscopy software tools. The results support why defining detailed recipes of software workflows and sharing these recipes is necessary and rewarding: Open source tools and (meta)data exchange can help to make our day-to-day data processing tasks become more efficient, the training of new users and knowledge transfer become easier, and assist us with automated quantification of uncertainties to gain access to substantiated results
Studying the galactic outflow in NGC 1569
We present deep WIYN H-alpha imaging of the dwarf irregular starburst galaxy
NGC 1569, together with WIYN SparsePak spatially-resolved optical spectroscopy
of the galactic outflow. This leads on from our previous detailed analyses of
the state of the ISM in the central regions of this galaxy. Our deep imaging
reveals previously undetected ionized filaments in the outer halo. Through
combining these results with our spectroscopy we have been able to re-define
the spatial extent of the previously catalogued superbubbles, and derive
estimates for their expansion velocities, which we find to be in the range
50-100 km/s. The implied dynamical ages of <25 Myr are consistent with the
recent star- and cluster-formation histories of the galaxy. Detailed
decomposition of the multi-component H-alpha line has shown that within a
distinct region ~700x500 pc in size, roughly centred on the bright super star
cluster A, the profile is composed of a bright, narrow (FWHM <= 70 km/s)
feature with an underlying, broad component (FWHM ~ 150 km/s). Applying the
conclusions found in our previous work regarding the mechanism through which
the broad component is produced, we associate the faint, broad emission with
the interaction of the hot, fast-flowing winds from the young star clusters
with cool clumps of ISM material. This interaction generates turbulent mixing
layers on the surface of the clouds and the evaporation and/or ablation of
material into the outflow. Under this interpretation, the extent of the broad
component region may indicate an important transition point in the outflow,
where ordered expansion begins to dominate over turbulent motion. In this
context, we present a multi-wavelength discussion of the evolutionary state of
the outflow.Comment: 17 pages, 12 figures, 2 tables, accepted for publication in MNRA
Human Cytomegalovirus: detection of congenital and perinatal infection in Argentina
BACKGROUND: Human cytomegalovirus (CMV) is one of the most commonly found agents of congenital infections. Primary maternal infection is associated with risk of symptomatic congenital diseases, and high morbidity is frequently associated with very low birth weight. Neonates with asymptomatic infection develop various sequelae during infancy. This is the first Argentine study performed in neonates with congenital and postnatal HCMV infection. The purpose of this study was to evaluate the performance of the polymerase chain reaction (PCR) technique with different pairs of primers, to detect cytomegalovirus isolated in tissue cultures and directly in urine and dried blood spot (DBS) specimens. Results were compared with IgM detection. METHODS: The study was performed between 1999 and 2001 on routine samples in the Laboratory. A total of 61 urine and 56 serum samples were selected from 61 newborns/infants, 33 patients whose samples were analyzed during the first two to three weeks of life were considered congenital infections; the remaining 28 patients whose samples were taken later than the third week were grouped as perinatal infections, although only in 4 the perinatal transmission of infection was determined unequivocally Cytomegalovirus diagnosis was made by isolating the virus from urine samples in human foreskin fibroblast cells. Three different primer pairs directed to IE, LA and gB genes were used for the HCMV PCR assay in viral isolates. Subsequently, PCR and nested PCR (nPCR) assays with gB primers were performed directly in urine and in 11 samples of dried blood spot (DBS) on Guthrie Card, these results were then compared with serology. RESULTS: The main clinical manifestations of the 33 patients with congenital infection were purpura, jaundice, hepatomegaly and anaemia. Three patients presented low birth weight as single symptom, 10, intracranial calcifications, and 2, kidney failure. In the 28 patients grouped as with perinatal infection, anaemia, hepatosplenomegaly and enzymatic alteration were predominant, and 4 patients were HIV positive. The primers used to amplify the gB region had a PCR positivity rate of 100%, whereas those that amplified IE and LA regions had a PCR positivity rate of 54% and 61% respectively, in CMV isolates. Amplification by PCR of urine samples (with no previous DNA extraction), using primers for the gB region, detected 34/61 positive samples. Out of the 33 samples from patients with congenital infection, 24 (73%) were positive. When nPCR was used in these samples, all were positive, whereas in the remaining 28 patients, two negative cases were found. Cytomegalovirus DNA detection in 11 samples was also carried out in DBS: 7 DBS samples were positive and 4 were negative. CONCLUSIONS: Primers directed to the gB fragment region were the best choice for the detection of CMV DNA in positive isolates. In congenital infections, direct PCR in urine was positive in a high percentage (73%) of samples; however, in patients grouped as with perinatal infection only 36% of the cases were positive. With n-PCR, total sample positivity reached 97%. PCR technique performed in DBS allowed identifying congenital infection in four patients and to be confirmed in 3. These results show the value of nPCR for the detection of all cases of CMV infection. The assay offers the advantage that it may be performed within the normal working day and provides reliable results in a much shorter time frame than that required for either traditional tissue culture or the shell-viral assay
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