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High-mass star formation is not well understood chiefly because examples are deeply embedded, relatively distant, and crowded with sources of emission. Using VLA and VLBA observations of H2O and SiO maser emission, we have mapped in detail the structure and proper motion of material 20-500 AU from the closest high-mass YSO, radio source I in the Orion KL region. We observe streams of material driven in a rotating, wide angle, bipolar wind from the the surface of an edge-on accretion disk. The example of source I provides strong evidence that high-mass star formation proceeds via accretion.
We report the results of CO J=l—+0 mapping of portions of the blue outflow lobe of L1551 with ~ 7” (N-S) × 4” (E-W) resolution, obtained with the 3-element OVRO millimeter array. Comparison of our interferometer mosaic with lower resolution single-dish data shows that we resolve the strongest single-dish emission regions into filamentary structures, such as are characteristic of shock fronts mapped via their near-infrared H2 emission in other outflow sources.
For over a decade, the structure of the inner “hole” in the transition disk around TW Hydrae has been a subject of debate. To probe the innermost regions of the protoplanetary disk, observations at the highest possible spatial resolution are required. We present new interferometric data of TW Hya from near-infrared to millimeter wavelengths. We confront existing models of the disk structure with the complete data set and develop a new, detailed radiative-transfer model. This model is characterized by: 1) a spatial separation of the largest grains from the small disk grains; and 2) a smooth inner rim structure, rather than a sharp disk edge.
To identify risk factors associated with methicillin-resistant Staphylococcus aureus (MRSA) acquisition in long-term care facility (LTCF) residents.
Multicenter, prospective cohort followed over 6 months.
Three Veterans Affairs (VA) LTCFs.
All current and new residents except those with short stay (<2 weeks).
MRSA carriage was assessed by serial nares cultures and classified into 3 groups: persistent (all cultures positive), intermittent (at least 1 but not all cultures positive), and noncarrier (no cultures positive). MRSA acquisition was defined by an initial negative culture followed by more than 2 positive cultures with no subsequent negative cultures. Epidemiologic data were collected to identify risk factors, and MRSA isolates were typed by pulsed-field gel electrophoresis (PFGE).
Among 412 residents at 3 LTCFs, overall MRSA prevalence was 58%, with similar distributions of carriage at all 3 facilities: 20% persistent, 39% intermittent, 41% noncarriers. Of 254 residents with an initial negative swab, 25 (10%) acquired MRSA over the 6 months; rates were similar at all 3 LTCFs, with no clusters evident. Multivariable analysis demonstrated that receipt of systemic antimicrobials during the study was the only significant risk factor for MRSA acquisition (odds ratio, 7.8 [95% confidence interval, 2.1–28.6]; P = .002). MRSA strains from acquisitions were related by PFGE to those from a roommate in 9/25 (36%) cases; 6 of these 9 roommate sources were persistent carriers.
MRSA colonization prevalence was high at 3 separate VA LTCFs. MRSA acquisition was strongly associated with antimicrobial exposure. Roommate sources were often persistent carriers, but transmission from roommates accounted for only approximately one-third of MRSA acquisitions.
We have tracked the proper motions of ground-state λ7mm SiO maser emission excited by radio Source I in the Orion BN/KL region. Based on dynamical arguments, Source I is believed to be a hard 20 M⊙ binary. The SiO masers trace a linear bipolar outflow (NE-SW) 100 to 1000 AU from the binary. The median 3D velocity is 18 km s−1. An overlying distribution of 1.3 cm H2O masers betrays similar characteristics. The outflow is aligned with the rotation axis of an edge-on disk and wide angle flow known inside 100 AU. Gas dynamics and emission morphology traced by masers around Source I provide dynamical evidence of a magnetocentrifugal disk-wind around this massive YSO, notably a measured gradient in line-of-sight velocity perpendicular to the flow axis, in the same direction as the disk rotation and with comparable speed. The linearity of the flow, despite the high proper motion of Source I and the proximity of dense gas associated with the Orion Hot Core, is also more readily explained for a magnetized flow. The extended arcs of ground-state maser emission bracketing Source I are a striking feature, in particular since dust formation occurs at smaller radii. We propose that the arcs mark two C-type shocks at the transition radius to super-Alfvénic flow.
The Golden-cheeked Warbler Dendroica chrysoparia is a federally endangered Neotropical migrant that inhabits montane pine-oak forests in Mexico and northern Central America during the non-breeding season. Although it is known that Golden-cheeked Warblers are closely associated with ‘encino’ oaks (evergreen or holm oak) such as Quercus sapotifolia, Q. eliptica and Q. elongata, which have shiny, narrow, elliptical, or oblong leaves, quantitative habitat targets are useful for effectively incorporating this information into conservation planning and forest management practices. We analysed data on wintering Golden-cheeked Warblers collected during the non-breeding season in Honduras from 1996 to 1998 to identify quantitative targets for habitat conditions for this species. Data on warbler abundance were collected using line transect surveys located in montane pine-oak forests in a stratified-random fashion. Habitat data were collected at five 0.04 ha plots on these same transects and the averaged values used as predictors of Golden-cheeked Warbler abundance. We found that Golden-cheeked Warblers were strongly associated with the basal area of encino oaks and density of ‘roble’ oaks, such as Q. segoviensis, Q. purulhana and Q. rugosa, which have large, lobed leaves. Density of Golden-cheeked Warblers peaked at ≈ 5.6 m2 ha–1 basal area of encino and ≈7 roble oaks ha–1. These values can be used to identify quantitative habitat targets that can be directly incorporated into forest management practices to ensure that these activities maintain habitat conditions necessary for their use by Golden-cheeked Warblers.
The electronic structure of single crystal UO2 and polycrystalline δ-Pu is examined using photoelectron spectroscopy. These two actinide materials exhibit properties consistent with the 5f electrons at the threshold between localized and itinerant character. The results for δ-Pu may be viewed as the 5f electrons exhibiting a dual nature with some fraction of the 5f levels localized and not participating in the bonding while the other fraction of 5f character is involved in bonding and hybridization with the conduction electrons. For UO2 where angle-resolved photoemission is available, one observes dispersion in the 5f features indicative of the 5f electrons being influenced by the periodic potential of the lattice rather than purely influenced by the site to which the 5f electrons are generally localized.
We describe here the use of calixarenes, methylene (-CH2-) linked phenolic macrocyclic molecules, to stabilize the formation of quantum-confined (Q-) CdS clusters. Specifically, we focus on the use of an amino-derivatized calixarene, para-[(dimethylamino)- methyl]calixarene, to stabilize Q-CdS clusters which have been characterized by High Resolution TEM (HREM), as well as absorption and emission spectroscopies. Under typical preparative conditions, an average particle diameter of 36 Å is obtained. HREM, in combination with Selected Area Diffraction (SAD), confirms the structure of the clusters as zinc blende CdS. Spectroscopic studies using absorption and emission methods indicate that both particle size and cluster photophysics are sensitive to the ratio of CdS to calixarene.
Plasma-enhanced CVD (PECVD) deposited alumina (A12O3) thin films and single sapphire crystals were co-doped with both erbium and ytterbium using ion implantation. Yb3+ and Er3+ concentrations ranged from 2.4At% to 8At% and from 0.4At% to 0.8At%, respectively. The samples show relatively strong, broad, room-temperature photoluminescence (PL) at λ=11.53µm corresponding to the intra-4f transitions between the 4I13/2 (first excited) and the 4I15/2 (ground) state of Er3+. The full width at half maximum (FWHM) of the emission spectrum is as high as 67nm for the A12O3 thin films; for the sapphire crystals it is 45nm. The fluorescence lifetime of the samples has been measured to be as high as 4.2ms at 50mW laser pump power. The indirect pumping of erbium through the transfer of energy from ytterbium has been demonstrated and the PL peak intensity has been studied as a function of the Yb3+/Er3+ concentration ratio when the samples are pumped at 514nm and 850nm; the PL excitation spectrum (PL at 1.53gm as a function of pump wavelength) of an Er3+/Yb3+ co-implanted sample is also presented. Both the PL peak intensity at 1.53µm and the fluorescence lifetime have been studied as functions of annealing temperature. Luminescence spectra attributed to defects in the alumina matrix are presented for as-implanted samples and following thermal annealing.
Material properties depend on their fabricated structure and orientation. It is thus important to develop rapid nondestructive techniques that will both allow determination of the orientation fabricated, and identify any changes that occur over time as a result of subsequent in service environmental conditions.
The present study examines the relationship between the thermal penetration time and planarity in polyimide films. Polyimides are advanced materials that have good high temperature stability, excellent dimensional stability, and excellent mechanical, electrical, and chemical resistance properties. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation in the polyimide film was characterized by polarizing microscope techniques, while the thermal penetration time measurements utilized a new rapid nondestructive modified hot wire instrument.
This correlation will be the first time thermal penetration time has been measured by modified hot wire techniques and related to the internal structure of a polyimide. The work contributes to a deeper theoretical understanding of heat transfer mechanisms as they relate to orientation. Thermal penetration time evaluation could provide a new tool in the arsenal of structural characterization techniques.
This relationship between thermal penetration time and orientation is key for film manufacturers. Such a correlation has potential to speed the development cycles of new materials and assure properties during production and end-use applications.
Certain diseases have been associated with the administration of heavy elements as contrast agents to patients undergoing medical imaging procedures. Recently, the presence of gadolinium (Gd) administered as a paramagnetic contrast agent for MRI contrast studies was associated with the incidence of Nephrogenic Fibrosing Dermopathy (NFD), also called Nephrogenic Systemic Fibrosis (NSF). To determine specific causation, Gd and other metallic nanoparticles in various tissues must be detected directly and characterized in-situ. This is done to develop specific mechanisms for the chemical modification of the metal elements as the result of a biologic response. Fixed biopsies embedded in paraffin were sectioned at 3-5 μm thick, deparaffinized by hand (xylene and 100% ethyl alcohol), placed on carbon planchettes, and allowed to air dry. Deparaffinized tissues were examined using a field emission SEM (FE-SEM) to directly detect and image the presence of Gd as well as other metals. Backscatter electron (BSE) imaging (20kV) was used to discern metal particles within tissues. Energy dispersive spectroscopy (EDS) (15kV) was used to verify the specific elements present. This allowed for the spatial characterization of the nanoparticles within the tissues but due to the physical limitations of SEM/EDS, quantification of the amount of metal was not possible. Mass concentration of the metal elements was determined using inductively coupled plasma mass spectrometry (ICP-MS) on digested tissues. Thick tissue sections, >30 μm, were used for ICP-MS to provide enough mass for detection. These sections were taken from the histology blocks adjacent to the thin sections used in the FE-SEM. Gadolinium was detected in skin, heart, lung and liver tissues. The highest concentrations were found in heart and skin; both had average tissue concentrations greater than 200μg/g (100-450μg/g range). In skin, gadolinium nano-particulates were readily seen near cell body locations in autopsy samples and within the cells in biopsy samples. The cells where gadolinium was most easily found were along blood vessels. In the cells the agglomerates appear granular with a size of less than 100 nm. They are diffused throughout the cell but as of this time not associated with any particular cell structure. Subsequent work using TEM will examine that aspect as well as the specific ultrastructure and chemistry of the nanoparticles. In this investigation, gadolinium was detected in the tissues of a number of patients with NSF. Although neither dispositive of a pathophysiologic mechanism, nor proof of causation, the detection and quantification of gadolinium within tissues of NSF patients is supportive of the epidemiologic association between exposure to gadolinium containing contrast material and development of the disease.
TiO2 anatase nanotubes synthesised via anodic oxidation were used as adsorbent for the uptake of U and Pb from aqueous solution and the photoremoval of As(III). An X-ray photoelectron spectroscopy study of the sorbent medium surface revealed a high adsorption of U and Pb at pH 8. The adsorption of the uranyl ion was enhanced in an anoxy (N2) atmosphere, because this prevents the formation of very stable carbonyl complexes. As(III) was adsorbed on TiO2 but in the presence of O2 and UV light was oxidized to As(V). XPS analysis revealed that in the pH range 3-9 As(V) was always the major species detected at the surface of the titania photocatalyst.
Visible-light-driven Ag3VO4 photocatalysts were successfully synthesized using low-temperature hydrothermal synthesis method. Under various hydrothermal conditions, the structures of silver vanadates were tuned by manipulating the hydrothermal time and the ratio of silver to vanadium. X-ray diffraction (XRD) results reveal that the powders prepared in a stoichiometric ratio consisted of pure α-Ag3VO4 or mixed phases of Ag4V2O7 and α-Ag3VO4. With increasing the Ag-to-V mole ratio to 6:1, the resulting samples were identified as pure monoclinic structure α-Ag3VO4. UV-vis spectroscopy indicated that silver vanadate particles had strong visible light absorption with associated band gaps in the range of 2.2-2.5 eV. The sample synthesized in the excess silver exhibited higher photocatalytic activity than that synthesized in a stoichiometric ratio. The powder synthesized at silver-rich at 140℃ for 4 h (SHT4) exhibited the highest photocatalytic activity among all samples. The reactivity of SHT4 (surface area, 3.52 m2 g-1) on the decomposition of gaseous benzene was about 16 times higher than that of P25 (surface area, 49.04 m2 g-1) under visible light irradiation. A well developed crystallinity of Ag3VO4 of SHT 4 was considered to enhance the photocatalytic efficiency.
Relapse prevention for bipolar disorder increases time to relapse but is not available in routine practice.
To determine the feasibility and effectiveness of training community mental health teams (CMHTs) to deliver enhanced relapse prevention.
In a cluster randomised controlled trial, CMHT workers were allocated to receive 12 h training in enhanced relapse prevention to offer to people with bipolar disorder or to continue giving treatment as usual. The primary outcome was time to relapse and the secondary outcome was functioning.
Twenty-three CMHTs and 96 service users took part. Compared with treatment as usual, enhanced relapse prevention increased median time to the next bipolar episode by 8.5 weeks (hazard ratio 0.79, 95% CI 0.45–1.38). Social and occupational functioning improved with the intervention (regression coefficient 0.68, 95% CI 0.05–1.32). The clustering effect was negligible but imprecise (intracluster correlation coefficient 0.0001, 95% CI 0.0000–0.5142).
Training care coordinators to offer enhanced relapse prevention for bipolar disorder may be a feasible effective treatment. Large-scale cluster trials are needed.
Around high-mass Young Stellar Objects (YSOs), outflows are expected to be launched and collimated by accretion disks inside radii of 100 AU. Strong observational constraints on disk-mediated accretion in this context have been scarce, largely owing to difficulties in probing the circumstellar gas at scales 10-100 AU around high-mass YSOs, which are on average distant (>1 Kpc), form in clusters, and ignite quickly whilst still enshrouded in dusty envelopes. Radio Source I in Orion BN/KL is the nearest example of a high-mass YSO, and only one of three YSOs known to power SiO masers. Using VLA and VLBA observations of different SiO maser transitions, the KaLYPSO project (http://www.cfa.harvard.edu/kalypso/) aims to overcome past observational limitations by mapping the structure, 3-D velocity field, and dynamical evolution of the circumstellar gas within 1000 AU from Source I. Based on 19 epochs of VLBA observations of v=1,2 SiO masers over ~2 years, we produced a movie of bulk gas flow tracing the compact disk and the base of the protostellar wind at radii < 100 AU from Source I. In addition, we have used the VLA to map 7mm SiO v=0 emission and track proper motions over 10 years. We identify a narrowly collimated outflow with a mean motion of 18 km/s at radii 100-1000 AU, along a NE-SW axis perpendicular to that of the disk traced by the v=1,2 masers. The VLBA and VLA data exclude alternate models that place outflow from Source I along a NW-SE axis. The analysis of the complete (VLBA and VLA) dataset provides the most detailed evidence to date that high-mass star formation occurs via disk-mediated accretion.