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Phased VLA observations of the Galactic center magnetar J1745-2900 over 8-12 GHz reveal rich single pulse behavior. The average profile is comprised of several distinct components and is fairly stable over day timescales and GHz frequencies. The average profile is dominated by the jitter of relatively narrow pulses. The pulses in each of the four profile components are uncorrelated in phase and amplitude, although the occurrence of pulse components 1 and 2 appear to be correlated. Using a collection of the brightest individual pulses, we verify that the index of the dispersion law is consistent with the expected cold plasma value of 2. The scattering time is weakly constrained, but consistent with previous measurements, while the dispersion measure DM = 1763+3−10 pc cm−3 is lower than previous measurements, which could be a result of time variability in the line-of-sight column density or changing pulse profile shape over time or frequency.
It is significant that the orbits of the planets in the solar system are very nearly circular, except for Mercury and Pluto where, conceivably, due to their comparatively small sizes, the tidal forces have played a less active role. Most of the suspected planets orbiting pulsars have nearly circular orbits. These systems tend to have minimum energy and are subjected to tidal forces. We find that a planet circularizes its orbit, in an effort to attain orbital stability and the ground state. Details can be found in Magalinsky & Chatterjee, 1997, and Magalinsky and Chatterjee, 2000.
An intriguing trend among it Kepler's multi-planet systems is an overabundance of planet pairs with period ratios just wide of mean motion resonances (MMR) and a dearth of systems just narrow of them. In a recently published paper Chatterjee & Ford (2015; henceforth CF15) has proposed that gas-disk migration traps planets in a MMR. After gas dispersal, orbits of these trapped planets are altered through interaction with a residual planetesimal disk. They found that for massive enough disks planet-planetesimal disk interactions can break resonances and naturally create moderate to large positive offsets from the initial period ratio for large ranges of planetesimal disk and planet properties. Divergence from resonance only happens if the mass of planetesimals that interact with the planets is at least a few percent of the total planet mass. This threshold, above which resonances are broken and the offset from resonances can grow, naturally explains why the asymmetric large offsets were not seen in more massive planet pairs found via past radial velocity surveys. In this article we will highlight some of the key findings of CF15. In addition, we report preliminary results from an extension of this study, that investigates the effects of planet-planetesimal disk interactions on initially non-resonant planet pairs. We find that planetesimal scattering typically increases period ratios of non-resonant planets. If the initial period ratios are below and in proximity of a resonance, under certain conditions, this increment in period ratios can create a deficit of systems with period ratios just below the exact integer corresponding to the MMR and an excess just above. From an initially uniform distribution of period ratios just below a 2:1 MMR, planetesimal interactions can create an asymmetric distribution across this MMR similar to what is observed for the kepler planet pairs.
To determine the source and identify control measures of an outbreak of Tsukamurella species bloodstream infections at an outpatient oncology facility.
Epidemiologic investigation of the outbreak with a case-control study.
A case was an infection in which Tsukamurella species was isolated from a blood or catheter tip culture during the period January 2011 through June 2012 from a patient of the oncology clinic. Laboratory records of area hospitals and patient charts were reviewed. A case-control study was conducted among clinic patients to identify risk factors for Tsukamurella species bloodstream infection. Clinic staff were interviewed, and infection control practices were assessed.
Fifteen cases of Tsukamurella (Tsukamurella pulmonis or Tsukamurella tyrosinosolvens) bloodstream infection were identified, all in patients with underlying malignancy and indwelling central lines. The median age of case patients was 68 years; 47% were male. The only significant risk factor for infection was receipt of saline flush from the clinic during the period September–October 2011 (P = .03), when the clinic had been preparing saline flush from a common-source bag of saline. Other infection control deficiencies that were identified at the clinic included suboptimal procedures for central line access and preparation of chemotherapy.
Although multiple infection control lapses were identified, the outbreak was likely caused by improper preparation of saline flush syringes by the clinic. The outbreak demonstrates that bloodstream infections among oncology patients can result from improper infection control practices and highlights the critical need for increased attention to and oversight of infection control in outpatient oncology settings.
Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the southern hemisphere designed specifically to explore the low-frequency astronomical sky between 80 and 300 MHz with arcminute angular resolution and high survey efficiency. The telescope will enable new advances along four key science themes, including searching for redshifted 21-cm emission from the EoR in the early Universe; Galactic and extragalactic all-sky southern hemisphere surveys; time-domain astrophysics; and solar, heliospheric, and ionospheric science and space weather. The Murchison Widefield Array is located in Western Australia at the site of the planned Square Kilometre Array (SKA) low-band telescope and is the only low-frequency SKA precursor facility. In this paper, we review the performance properties of the Murchison Widefield Array and describe its primary scientific objectives.
The future of centimetre and metre-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by a consortium of 17 countries that will be 50 times more sensitive than any existing radio facility. Most of the key science for the SKA will be addressed through large-area imaging of the Universe at frequencies from a few hundred MHz to a few GHz. The Australian SKA Pathfinder (ASKAP) is a technology demonstrator aimed in the mid-frequency range, and achieves instantaneous wide-area imaging through the development and deployment of phased-array feed systems on parabolic reflectors. The large field-of-view makes ASKAP an unprecedented synoptic telescope that will make substantial advances in SKA key science. ASKAP will be located at the Murchison Radio Observatory in inland Western Australia, one of the most radio-quiet locations on the Earth and one of two sites selected by the international community as a potential location for the SKA. In this paper, we outline an ambitious science program for ASKAP, examining key science such as understanding the evolution, formation and population of galaxies including our own, understanding the magnetic Universe, revealing the transient radio sky and searching for gravitational waves.
We present a new joint analysis of pulsar dispersion measures and diffuse Hα emission in the Milky Way, which we use to derive the density, pressure and filling factor of the thick disk component of the warm ionised medium (WIM) as a function of height above the Galactic disk. By excluding sightlines at low Galactic latitude that are contaminated by Hii regions and spiral arms, we find that the exponential scale-height of free electrons in the diffuse WIM is 1830–250+120 pc, a factor of two larger than has been derived in previous studies. The corresponding inconsistent scale heights for dispersion measure and emission measure imply that the vertical profiles of mass and pressure in the WIM are decoupled, and that the filling factor of WIM clouds is a geometric response to the competing environmental influences of thermal and non-thermal processes. Extrapolating the properties of the thick-disk WIM to mid-plane, we infer a volume-averaged electron density 0.014 ± 0.001 cm−3, produced by clouds of typical electron density 0.34 ± 0.06 cm−3 with a volume filling factor 0.04 ± 0.01. As one moves off the plane, the filling factor increases to a maximum of ∼30% at a height of ≈1–1.5 kpc, before then declining to accommodate the increasing presence of hot, coronal gas. Since models for the WIM with a ≈1 kpc scale-height have been widely used to estimate distances to radio pulsars, our revised parameters suggest that the distances to many high-latitude pulsars have been substantially underestimated.
The Australian Square Kilometre Array Pathfinder (ASKAP) will give us an unprecedented opportunity to investigate the transient sky at radio wavelengths. In this paper we present VAST, an ASKAP survey for Variables and Slow Transients. VAST will exploit the wide-field survey capabilities of ASKAP to enable the discovery and investigation of variable and transient phenomena from the local to the cosmological, including flare stars, intermittent pulsars, X-ray binaries, magnetars, extreme scattering events, interstellar scintillation, radio supernovae, and orphan afterglows of gamma-ray bursts. In addition, it will allow us to probe unexplored regions of parameter space where new classes of transient sources may be detected. In this paper we review the known radio transient and variable populations and the current results from blind radio surveys. We outline a comprehensive program based on a multi-tiered survey strategy to characterise the radio transient sky through detection and monitoring of transient and variable sources on the ASKAP imaging timescales of 5 s and greater. We also present an analysis of the expected source populations that we will be able to detect with VAST.
We are developing a purely commensal survey experiment for fast (<5 s) transient radio sources. Short-timescale transients are associated with the most energetic and brightest single events in the Universe. Our objective is to cover the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view. Fast timescale transients open new vistas on the physics of high brightness temperature emission, extreme states of matter and the physics of strong gravitational fields. In addition, the detection of extragalactic objects affords us an entirely new and extremely sensitive probe on the huge reservoir of baryons present in the IGM. We outline here our approach to the considerable challenge involved in detecting fast transients, particularly the development of hardware fast enough to dedisperse and search the ASKAP data stream at or near real-time rates. Through CRAFT, ASKAP will provide the testbed of many of the key technologies and survey modes proposed for high time resolution science with the SKA.
Members of the family Gastrothylacidae (Trematoda: Digenea: Paramphistomata) are parasitic in ruminants throughout Africa and Asia. In north-east India, five species of pouched amphistomes, namely Fischoederius cobboldi, F. elongatus, Gastrothylax crumenifer, Carmyerius spatiosus and Velasquezotrema tripurensis, belonging to this family have been reported so far. In the present study, the molecular phylogeny of these five gastrothylacid species is derived using the second internal transcribed spacer (ITS2) sequence and secondary structure analyses. ITS2 sequence analysis was carried out to see the occurrence of interspecific variations among the species. Phylogenetic analyses were performed for primary sequence data alone as well as the combined sequence-structure information using neighbour-joining and Bayesian approaches. The sequence analysis revealed that there exist considerable interspecific variations among the various gastrothylacid fluke species. In contrast, the inferred secondary structures for the five species using minimum free energy modelling showed structural identities, in conformity with the core four-helix domain structure that has been recently identified as common to almost all eukaryotic taxa. The phylogenetic tree reconstructed using combined sequence–structure data showed a better resolution, as compared to the one using sequence data alone, with the gastrothylacid species forming a monophyletic group that is well separated from members of the other family, Paramphistomidae, of the amphistomid flukes group. The study provides the molecular characterization based on primary sequence data of the rDNA ITS2 region of the gastrothylacid amphistome flukes. Results also demonstrate the phylogenetic utility of the ITS2 sequence–secondary structure data for inferences at higher taxonomic levels.
The effect of substrate bias on the properties of rf sputtered boron nitride films on Si and GaAs substrate were investigated. IR transmission and reflectivity of films with different substrate bias were measured with Perkin Elmer 983 IR spectroscopy. From the IR reflectivity data, transverse optical mode(TO) and longitudinal optical mode(LO) frequencies were derived by fitting Kramer-Kronig model. Absorption coefficient was determined from IR transmission data. The resultant TO and LO modes showed that substrate bias caused broadening of reststrahlen band of rf sputtered boron nitride. We also tried to dope boron nitride films with silicon by alternate sputtering of BN and Si targets controlling sputtering time of each target followed by annealing. Electrical resistivity was measured over the temperature range between 175 K to 370 K for both intrinsic and Si-doped boron nitride films. Intrinsic rf sputtered boron nitride showed Little change in resistivity (109 Ω cm - 1011 Ω cm ) over the temperature range studied. While Si doped BN showed linear change in resistivity with increasing temperature and its activation energy was about 0.22 eV. The effect of substrate bias was also investigated by monitoring the XPS core level spectra of both Bis and N Is peaks, respectively. Substrate bias caused the shift of both B ls and N ls peak to higher binding energy. The effect of substrate bias on refractive index was also studied.
Deep levels in MOCVD grown p-InP on GaAs substrates have been investigated by Deep Level Transient Spectroscopy (DLTS). The effect of hydrogenation on the electrical activity of these levels has been studied through a combination of DLTS and Photoluminescence (PL) measurements. DLTS measurements indicate a drop of trap density from σ 5 × 1014 cm−3 to σ 1 × 1012 cm−3 after hydrogenation. Annealing at 400°C reactivated only the dopants, while temperatures above 600°C were necessary for deep-level reactivation. This combined with a logarithmic dependence on fill pulse time, indicate that at least one broad DLTS peak is associated with dislocations. The PL the DLTS results show that the dislocation related traps are passivated by hydrogen, preferentially over the dopants and that a wide annealing window exists for dopant reactivation.
Analysis of the current density-voltage (J-V) characteristics of sandwich a-Si:H n+-i-n+ structures made of the same materials but with varying thicknesses of the i-layer, has given rise to two somewhat contradictory speculations regarding the density of states (DOS) at the Fermi level of the i-layer. The first of these postulates that the DOS over the first 2000–4000A of the i-a-Si:H layer is larger by a factor of 3–10 than that in the rest of the film With this hypothesis however, the experimentally observed low activation energies (Ea) for thin n+-i-n+ devices remain unexplained. In the other analysis, a consideration of the n+-i space-charge regions enables a fair description of the experimental results assuming that the electron DOS is position independent in the i-layer. In the present report we use accurate computer modelling to calculate and analyse the J-V characteristics of a-Si:H n+-i-n+ structures in the low bias ohmic region as a function of device thickness, ambient temperature and the quality of the i-layer. We find that the n+-i interface is abrupt only for a device with a high dangling bond density. For good quality material however, the depletion width extends right across the i-layer for a thin device and the zone of charge neutrality is never reached, resulting in low values of Ea in the ohmic region. In the latter case Ea increases with i-layer thickness. Analysis by detailed computer modelling confirms that the experimental results may be explained by assuming a density of states independent of the thickness of the i-layer.
The growth and structural characterization of UHV-compatible LPCVD grown strained-Si layer on linearly graded relaxed SiGe layer and the electrical properties of the high-k ultrathin ZrO2 films deposited on strained-Si layer using microwave-plasma CVD at low temperature (150°C) are reported. The strained-Si layer has been characterized using AFM, TEM and Raman spectroscopy. The C-V and G-V characteristics of ZrO2 films have been used to calculate the interface trap density, Dit, near the midgap energy, and the fixed oxide charge density, Qf/q. These are found to be 2.24 × 1012 cm−2 eV−1 and 1.45 × 1011 cm−2, respectively. Poole-Frenkel (PF) conduction mechanism is found to dominate the current conduction at room temperature.
In this study, well separated tapered CuO nanowires have been synthesized on copper grid using an easy and cost effective thermal oxidation method. A set of spectroscopic investigations have been performed on one single tapered CuO nanowire using Energy Dispersive X-ray, confocal Raman and confocal Photoluminescence spectroscopy to get insight into the mechanism of growth of the nanowires. Energy Dispersive X-ray studies reveal crystallization process of CuO nanowires occur from Cu/Cu2O mixed phase state to pure CuO structure. Raman measurements indicate a little sharpening of the Raman peaks with increasing growth temperature of the nanowires starting from 400°C to 600°C. Photoluminescence studies were carried out by mapping along the length of the nanowire to investigate the growth as well as optical properties of a single tapered CuO nanowire. As the diameter of the single tapered CuO nanowire decreases, the green emission of the nanowire gradually shifts towards the higher energy side. A steady blue shift of 20 nm of the photoluminescence peak has been attributed to the nanosize effect of the tapered nanowire along the length and enhanced surface defects.
Recent observations have revealed two new classes of planetary orbits. Rossiter-Mclaughlin (RM) measurements have revealed hot Jupiters in high-obliquity orbits. In addition, direct-imaging has discovered giant planets at large (~ 100 AU) separations via direct-imaging technique. Simple-minded disk-migration scenarios are inconsistent with the high-inclination (and even retrograde) orbits as seen in recent RM measurements. Furthermore, forming giant planets at large semi-major axis (a) may be challenging in the core-accretion paradigm. We perform many N-body simulations to explore the two above-mentioned orbital architectures. Planet–planet scattering in a multi-planet system can naturally excite orbital inclinations. Planets can also get scattered to large distances. Large-a planetary orbits created from planet–planet scattering are expected to have high eccentricities (e). Theoretical models predict that the observed long-period planets, such as Fomalhaut-b have moderate e ≈ 0.3. Interestingly, these are also in systems with disks. We find that if a massive-enough outer disk is present, a scattered planet may be circularized at large a via dynamical friction from the disk and repeated scattering of the disk particles.
Giardia lamblia, a protozoan parasite, infects a wide variety of vertebrates, including humans. Studies indicate that this anaerobic protist possesses a limited ability to synthesize lipid molecules de novo and depends on supplies from its environment for growth and differentiation. It has been suggested that most lipids and fatty acids are taken up by endocytic and non-endocytic pathways and are used by Giardia for energy production and membrane/organelle biosynthesis. The purpose of this article is to provide an update on recent progress in the field of lipid research of this parasite and the validation of lipid metabolic pathways through recent genomic information. Based on current cellular, biochemical and genomic data, a comprehensive pathway has been proposed to facilitate our understanding of lipid and fatty acid metabolism/syntheses in this waterborne pathogen. We envision that the current review will be helpful in identifying targets from the pathways that could be used to design novel therapies to control giardiasis and related diseases.
Faecal specimens of diarrhoea cases (n=2495, collected between November 2007 and October 2009) from Infectious Diseases and Beliaghata General (ID&BG) Hospital, Kolkata, India, were screened by RT–PCR using specific primers targeting region C of the capsid gene of noroviruses (NoVs) to determine the seasonal distribution and clinical characteristics of NoVs associated with diarrhoea. NoV infection was detected in 78 cases, mostly in children aged <2 years. In 22/78 positive cases, the virus was detected as the sole agent; others were as mixed infections with other enteric pathogens. Sequencing of NVGII strains showed clustering with GII.4 NoVs followed by GII.13 and GII.6 NoVs. Clinical characteristics of the diarrhoeic children and adults in Kolkata indicated that NoV infections were detected throughout the year and were associated with a mild degree of dehydration.