4,108 research outputs found
Disseminated histoplasmosis in an 'immunocompetent' child
A rare case of severe disseminated histoplasmosis in a 7-year-old boy with apparently normal immune function is described. Current recommendations for diagnostic investigations, monitoring and the treatment of this disease with amphotericin B and itraconazole are reviewed
Recent Decisions
Comments on recent decisions by John W. Beatty, Fernand N. Dutile, Michael D. Sullivan, John A. Hauter, John M. Lamont, and John T. Mulvihill
Superficieibacter electus gen. nov., sp. nov., an extended-spectrum β-lactamase possessing member of the enterobacteriaceae family, isolated from Intensive Care Unit surfaces
<p>Two Gram-negative bacilli strains, designated BP-1(T) and BP-2, were recovered from two different Intensive Care Unit surfaces during a longitudinal survey in Pakistan. Both strains were unidentified using the bioMerieux VITEK MS IVD v2.3.3 and Bruker BioTyper MALDI-TOF mass spectrometry platforms. To more precisely determine the taxonomic identity of BP-1(T) and BP-2, we employed a biochemical and phylogenomic approach. The 16S rRNA gene sequence of strain BP-1(T) had the highest identity to Citrobacter farmeri CDC 2991-81(T) (98.63%) Citrobacter amalonaticus CECT 863(T) (98.56%), Citrobacter sedlakii NBRC 105722(T) (97.74%) and Citrobacter rodentium NBRC 105723(T) (97.74%). The biochemical utilization scheme of BP-1(T) using the Analytic Profile Index for Enterobacteriaceae (API20E) indicated its enzymatic functions are unique within the Enterobacteriaceae but most closely resemble Kluyvera spp., Enterobacter cloacae and Citrobacter koseri/farmeri. Phylogenomic analysis of the shared genes between BP-1(T), BP-2 and type strains from Kluyvera, Citrobacter, Escherichia, Salmonella, Kosakonia, Siccibacter and Shigella indicate that BP-1(T) and BP-2 isolates form a distinct branch from these genera. Average Nucleotide Identity analysis indicates that BP-1(T) and BP-2 are the same species. The biochemical and phylogenomic analysis indicate strains BP-1(T) and BP-2 represent a novel species from a new genus within the Enterobacteriaceae family, for which the name Superficieibacter electus gen. nov., sp. nov., is proposed. The type strain is BP-1(T) (= ATCC BAA-2937, = NBRC 113412).</p
Effects of 1- and 2-MeV electrons on photomultiplier tubes
Various types of photomultiplier tubes useful for space applications were irradiated with 1- and 2-MeV electrons at Van Allen radiation belt fluxes of 100,000 to 10 millions electrons/sq cm-sec. The increase in the dark current due to electron irradiation was observed at various bias voltages under worst-case conditions (no shielding). Results were presented in the form of dark current plotted against electron flux. All the tubes tested showed extremely large increases in dark current. Tube types 541A, 6217, 6199, and 6903 exhibited the largest increases under irradiation, whereas type 1P22 was affected the least. All the damage observed was transient. The luminescence produced in the optical window probably accounts for a large part of the dark-current increases, but there were some effects possibly due to direct irradiation of the photocathode and dynode chain
The ROTSE-III Robotic Telescope System
The observation of a prompt optical flash from GRB990123 convincingly
demonstrated the value of autonomous robotic telescope systems. Pursuing a
program of rapid follow-up observations of gamma-ray bursts, the Robotic
Optical Transient Search Experiment (ROTSE) has developed a next-generation
instrument, ROTSE-III, that will continue the search for fast optical
transients. The entire system was designed as an economical robotic facility to
be installed at remote sites throughout the world. There are seven major system
components: optics, optical tube assembly, CCD camera, telescope mount,
enclosure, environmental sensing & protection and data acquisition. Each is
described in turn in the hope that the techniques developed here will be useful
in similar contexts elsewhere.Comment: 19 pages, including 4 figures. To be published in PASP in January,
2003. PASP Number IP02-11
Status of ANITA and ANITA-lite
We describe a new experiment to search for neutrinos with energies above 3 x
10^18 eV based on the observation of short duration radio pulses that are
emitted from neutrino-initiated cascades. The primary objective of the
ANtarctic Impulse Transient Antenna (ANITA) mission is to measure the flux of
Greisen-Zatsepin-Kuzmin (GZK) neutrinos and search for neutrinos from Active
Galactic Nuclei (AGN). We present first results obtained from the successful
launch of a 2-antenna prototype instrument (called ANITA-lite) that circled
Antarctica for 18 days during the 03/04 Antarctic campaign and show preliminary
results from attenuation length studies of electromagnetic waves at radio
frequencies in Antarctic ice. The ANITA detector is funded by NASA, and the
first flight is scheduled for December 2006.Comment: 9 pages, 8 figures, to be published in Proceedings of International
School of Cosmic Ray Astrophysics, 14th Course: "Neutrinos and Explosive
Events in the Universe", Erice, Italy, 2-13 July 200
Observations of Microwave Continuum Emission from Air Shower Plasmas
We investigate a possible new technique for microwave measurements of
ultra-high energy cosmic ray (UHECR) extensive air showers which relies on
detection of expected continuum radiation in the microwave range, caused by
free-electron collisions with neutrals in the tenuous plasma left after the
passage of the shower. We performed an initial experiment at the AWA (Argonne
Wakefield Accelerator) laboratory in 2003 and measured broadband microwave
emission from air ionized via high energy electrons and photons. A follow-up
experiment at SLAC (Stanford Linear Accelerator Center) in summer of 2004
confirmed the major features of the previous AWA observations with better
precision and made additional measurements relevant to the calorimetric
capabilities of the method. Prompted by these results we built a prototype
detector using satellite television technology, and have made measurements
indicating possible detection of cosmic ray extensive air showers. The method,
if confirmed by experiments now in progress, could provide a high-duty cycle
complement to current nitrogen fluorescence observations of UHECR, which are
limited to dark, clear nights. By contrast, decimeter microwave observations
can be made both night and day, in clear or cloudy weather, or even in the
presence of moderate precipitation.Comment: 15 pages, 13 figure
Ultra-Relativistic Magnetic Monopole Search with the ANITA-II Balloon-borne Radio Interferometer
We have conducted a search for extended energy deposition trails left by
ultra-relativistic magnetic monopoles interacting in Antarctic ice. The
non-observation of any satisfactory candidates in the 31 days of accumulated
ANITA-II flight data results in an upper limit on the diffuse flux of
relativistic monopoles. We obtain a 90% C.L. limit of order
10^{-19}/(cm^2-s-sr) for values of Lorentz boost factor 10^{10}<gamma at the
anticipated energy E=10^{16} GeV. This bound is stronger than all previously
published experimental limits for this kinematic range.Comment: updated to version accepted by Phys. Rev.
New Measurement of the Cosmic-Ray Positron Fraction from 5 to 15 GeV
We present a new measurement of the cosmic-ray positron fraction at energies
between 5 and 15 GeV with the balloon-borne HEAT-pbar instrument in the spring
of 2000. The data presented here are compatible with our previous measurements,
obtained with a different instrument. The combined data from the three HEAT
flights indicate a small positron flux of non-standard origin above 5 GeV. We
compare the new measurement with earlier data obtained with the HEAT-e+-
instrument, during the opposite epoch of the solar cycle, and conclude that our
measurements do not support predictions of charge sign dependent solar
modulation of the positron abundance at 5 GeV.Comment: accepted for publication in PR
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