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We implemented a cleaning process for mobile patient equipment (MPE) and determined its success using adenosine trisphosphate (ATP) monitoring and data feedback. Following education for staff and ATP data feedback, the data suggest that the MPE cleaning program we implemented was successful.
We present the first time-resolved spectroscopic observations, made with the SALT HRS instrument, of a rapidly oscillating Ap star. We used the instrument in the High Stability mode, with the fastest readout settings – a setup never previously used. Over a 2.5-hr track length, we obtained 280 spectra at 8-second integration times and a cadence of 30 seconds. The target, α Circini, is the brightest of the roAp stars, and thus provides an excellent opportunity to test the instrument. Previous time-resolved spectroscopic studies of this star have been conducted by Kurtz, Elkin & Mathys† with the VLT/UVES instrument, and by Mkrtichian & Hatzes‡ with the HARPS instrument on the ESO 3.6-m telescope. Those two studies provide us with benchmarks to compare the performance of SALT/HRS for this type of project. With the upcoming TESS mission, the ability to perform high-precision, time-resolved spectroscopy of pulsating stars will be key for the scientific output of SALT.
We present observations of massive star-forming regions selected from the IRAS Point Source Catalog. The observations were made with the Very Large Array and the Large Millimeter Telescope to search for Class I methanol masers. We made interferometric observations of 125 massive star-forming regions in the 44 GHz methanol maser transition; 53 of the 125 fields showed emission. The data allow us to demonstrate associations, at arcsecond precision, of the Class I maser emission with outflows, HII regions and shocks traced by 4.5 μm emission. We made single-dish observations toward 38 of the 53 regions with 44 GHz masers detected to search for the methanol transitions at 84.5, 95.1, 96.7, 107.0, and 108.8 GHz. We find detection rates of 74, 55, 100, 3, and 45%, respectively. We used a wide-band receiver which revealed many other spectral lines that are common in star-forming regions.
The final stages of low-mass stellar evolution are characterized by significant mass loss due to stellar pulsations during the AGB phase, which lead to the development of planetary nebulae. Molecular masers of H2O, SiO, and ground state OH transitions are commonly detected in oxygen-rich late-type stars (OH/IR objects). In contrast, excited OH maser transitions are rare. We discuss our study of the carbon-rich pre-planetary nebula CRL618 (a prototypical post-AGB star). Observations conducted in May 2008 with the 305m Arecibo Telescope resulted in the first detection of a 4765MHz OH maser line in a late-type stellar object; the detection was confirmed a few months later also with Arecibo. Subsequent observations in 2015 and 2017 resulted in non-detection of the 4765MHz OH line. Our observations indicate that the 4765MHz OH maser in CRL 618 is highly variable, possibly tracing a short-lived phenomenon during the development of a pre-planetary nebula.
It has largely been accepted that pre-participation screening for student athletes is necessary, but there is still no consensus on the most effective and efficient ways to accomplish this. Most clinical strategies are based on retrospective case series. By applying the European Society of Cardiology and Seattle criteria, electrocardiography appears to afford the lowest false-positive rate for identifying potentially dangerous cardiac abnormalities in athletes. Prospective, randomised trials may help determine the most effective primary prevention. Normative data for age, gender, and ethnicity for screening tools need to be formulated to further reduce false-positive results. Targeted advanced screening aimed at the highest risk groups may be the most beneficial and cost-effective application of primary prevention.
Using in situ data from 2011 and 2013, we evaluate the ability of CryoSat-2 (CS-2) to retrieve sea-ice freeboard over fast ice in McMurdo Sound. This provides the first systematic validation of CS-2 in the coastal Antarctic and offers insight into the assumptions currently used to process CS-2 data. European Space Agency Level 2 (ESAL2) data are compared with results of a Waveform Fitting (WfF) procedure and a Threshold-First-Maximum-Retracker-Algorithm employed at 40% (TFMRA40). A supervised freeboard retrieval procedure is used to reduce errors associated with sea surface height identification and radar velocity in snow. We find ESAL2 freeboards located between the ice and snow freeboard rather than the frequently assumed snow/ice interface. WfF is within 0.04 m of the ice freeboard but is influenced by variable snow conditions causing increased radar backscatter from the air/snow interface. Given such snow conditions and additional uncertainties in sea surface height identification, a positive bias of 0.14 m away from the ice freeboard is observed. TFMRA40 freeboards are within 0.03 m of the snow freeboard. The separation of freeboard estimates is primarily driven by the different assumptions of each retracker, although waveform alteration by variations in snow properties and surface roughness is evident. Techniques are amended where necessary, and automatic freeboard retrieval procedures for ESAL2, WfF and TFMRA40 are presented. CS-2 detects annual fast-ice freeboard trends using all three automatic procedures that are in line with known sea-ice growth rates in the region.
Heartbeat stars are a relatively new class of eccentric ellipsoidal variable first discovered by Kepler. An overview of the current field is given with details of some of the interesting objects identified in our current Kepler sample of 135 heartbeats stars. Three objects that have recently been or are undergoing detailed study are described along with suggestions for further avenues of research. We conclude by discussing why heartbeat stars are an interesting new tool to study tidally induced pulsations and orbital dynamics.
A panel of 10 monoclonal antibodies was used to subgroup 326 strains of Legionella pneumophila serogroup 1. All but two strains could be classified into three major subgroups named after their representative strains Pontiac 1, Olda and Bellingham 1. Of the 50 isolates from patients, 44 representing 32 separate incidents were of the Pontiac subgroup. This subgroup was also found in 16 of 18 buildings epidomiologically associated with Legionnaires' Disease. In contrast, strains of the Olda subgroup predominated in buildings where no infections had occurred. In 9 of the 11 incidents where isolates were available from at least one patient as well as from the suspected environmental source, the monoclonal antibody reaction patterns of strains from patients were identical to those of one or more of their environmental counterparts.
Division V deals with all aspects of stellar variability, either intrinsic or due to eclipses by its companion in a binary system. In the case of intrinsic stellar variability the analysis of pulsating stars, surface inhomogeneities, stellar activity and oscillations are considered. For close binaries, classical detached eclipsing binaries are studied as well as more interacting systems, like contact and semi-detached binaries, or those with compact components, like cataclysmic variables and X-ray binaries, including the physics of accretion processes.
Study of natural microbial ecosystems is hampered by our inability to closely duplicate the development of a community in the laboratory environment. The lack of such systems is particularly acute when endolithic microbes are examined. In this study, we have developed a system that enables laboratory growth of cryptoendolithic microbial communities resembling those found in the porous sandstones making up the Colorado Plateau in southeastern Utah. Microscopic examination of natural and in vitro cryptoendolithic biofilms shows that, on a gross level, the laboratory biofilm is developing in a fashion that is structurally similar to that of the native community. Further confirmation that the laboratory system resembles the native community was obtained by using denaturing gradient gel electrophoresis (DGGE) and DNA sequence analysis to examine the biofilms for the presence of cyanobacteria and the Geobacteriaceae. We found that the molecular profiles for these two groups of bacteria were nearly identical in the native and in vitro biofilms. These data show that our system for growing cryptoendolithic bacteria in the laboratory is suitable for the study of these ecosystems and will allow for experimental manipulations that are not possible in the field.
With the resounding success of Helioseismology in determining the interior structure and rotation of the Sun, and in providing unprecedented studies of the interaction of pulsation and magnetic fields in the solar atmosphere, astronomers have been delighted, after decades of disappointing attempts, with the recent discovery of solar-like oscillations in ξHya, β Hyi, αCen, η Boo and νInd. There is now true seismology of a variety of solar-like stars. Asteroseismology also studies stars with a wide variety of interior and surface conditions. For two decades asteroseismic techniques have been applied to many pulsating stars across the HR Diagram. This review describes for non-specialists pulsation modes in stars and discusses a selection of some of the successes already accomplished in asteroseismology.
Forward-to-reverse bias step-recovery measurements were performed on In.07Ga.93N/GaN and Al.36Ga.64N/Al.46Ga.54N quantum-well (QW) light-emitting diodes grown on sapphire. With the QW sampling the minority-carrier hole density at a single position, distinctive two-phase optical decay curves were observed. Using diffusion equation solutions to self-consistently model both the electrical and optical responses, hole transport parameters τp = 758 ± 44 ns, Lp = 588 ± 45 nm, and μp = 0.18 ± 0.02 cm2/Vs were obtained for GaN. The mobility was thermally activated with an activation energy of 52 meV, suggesting trap-modulated transport. Optical measurements of sub-bandgap peaks exhibited slow responses approaching the bulk lifetime. For Al.46Ga.54N, a longer lifetime of τp = 3.0 μs was observed, and the diffusion length was shorter, Lp ≈ 280 nm. Mobility was an order of magnitude smaller than in GaN, μp ≈ 10−2 cm2/Vs, and was insensitive to temperature, suggesting hole transport through a network of defects.
The effects of thermal annealing on the minority-carrier diffusion lengths and depletion widths of GaInNAs are studied. We find that diffusion lengths in as-grown, Be- and Si-doped GaInNAs are limited to less than about 0.2 μm for samples with low concentrations of nitrogen. For higher concentrations of nitrogen, the diffusion lengths are not measurable. Annealing under a variety of temperatures and atmospheres typically makes the diffusion lengths even shorter. These short diffusion lengths are not yet long enough for GaInNAs to be useful in a next-generation, four-junction structure. Using undoped GaInNAs in a p–i–n structure is a promising approach to increase device performance. Currently, however, the depletion widths are too small at the bandgaps necessary for solar cells, and annealing does not appear to improve them.
A contacted electroreflectance technique was used to characterize the electronic properties of AlGaN/GaN heterostructure field-effect transistors (HFETs). By studying variations in the electroreflectance with applied electric field, spectral features associated with the AlGaN barrier, the 2-dimensional electron gas at the interface, and bulk GaN were observed. Barrier-layer composition and electric field were determined from the AlGaN Franz-Keldysh oscillations. Comparing HFETs grown on SiC and sapphire substrates, the measured AlGaN polarization electric field (0.25±0.05 MV/cm) approached that predicted by a standard model (0.33 MV/cm) for the higher mobility HFET grown on SiC.
Nitrogen vibrational mode spectra, Hall mobilities, and minority carrier diffusion lengths are examined for InGaAsN (≈ 1.1 eV bandgap) grown by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). Independent of growth technique, annealing promotes the formation of In-N bonding, and lateral carrier transport is limited by large scale (Ęmean free path ) material inhomogeneities. Comparing solar cell quantum efficiencies for devices grown by MBE and MOCVD, we find significant electron diffusion in the MBE material (reversed from the hole diffusion occurring in MOCVD material), and minority carrier diffusion in InGaAsN cannot be explained by a “universal”, nitrogen-related defect.
Lithium in cool magnetic CP stars in still poorly studied and estimations of the Li abundance in these stars are scarce. There is some evidence of variability of the LiI 6708 Â line, but this variability has not been studied systematicaly. Even the identification of the 6708 Â line with the LiI resonance doublet is still in doubt. This problem is important in the broader context of the Li abundance in various types of stars, as well as for deeper undersfanding of the magnetic star phonomenon itself. The reason for fhis is that the Li abundance in very sensitive to evolutionary status of the stars and their properties, such as the character and intensity of mixing processes.
We present the first results from multi-site observations of the δ Scuti star XX Pyx (CD–24°7599). The observations were carried out as the 17th run of the Delta Scuti Network. We collected 583 hr of B, V time-series photometry, resulting in a detection level (4σ) in the amplitude spectrum of 0.5 mmag. We detect 6 new pulsation frequencies, bringing the total number of frequencies known in this star up 19.