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The abundances of Ni, Fe, Cr, Mn, P, Cu, K, Na, Ga, Ge, Se, Zn, S, Br, and C were measured in interplanetary dust particles (IDPs) collected from the Earth's stratosphere. All elements with nebular condensation temperatures lower than Mn, except S, were enriched relative to the most volatile-rich type of meteorite while the refractory elements Cr and Ni were present at chondritic abundances. This element abundance pattern is consistent with nebular condensation, suggesting the IDPs condensed at either a different location or time in the evolving solar nebula than do the meteorites. The enrichments of the major elements C, Na, P, and K exclude the possibility that the volatile enrichment in IDPs results from a minor amount of contamination.
Two major sources are observed to contribute to the Zodiacal Cloud: main-belt asteroids and active comets. However, the discovery of 100 km size objects in trans-Neptunian orbits (Jewitt & Luu 1993) coupled with Pioneer 10 measurements showing an essentially constant flux of 10 μm dust from 4 to 18 AU with indications that dust may be in near-circular orbits (Humes 1980) suggests that collisions in the Kuiper Belt may contribute significantly to the Zodiacal Cloud and to the interplanetary dust collected from the Earth's stratosphere. Kuiper Belt dust collected at Earth could be identified by high densities of solar flare tracks, unusually thick amorphous rims, and high concentrations of spallogenic isotopes.
Interplanetary dust particles (IDPs), ∼ 10μm particles from comets and asteroids, have been collected by NASA from the Earth's stratosphere. We compared carbon X-ray Absorption Near-Edge Structure (XANES) and Fourier Transform Infra-Red (FTIR) spectra of anhydrous and hydrated interplanetary dust particles and found that anhydrous and hydrated IDPs have similar types and abundances of organic carbon. This is different from results on meteorites, which show that hydrated carbonaceous meteorites contain abundant organic matter, while anhydrous carbonaceous meteorites contain less carbon mostly in elemental form. But all anhydrous carbonaceous meteorites are depleted in moderately volatile and volatile elements in a pattern that suggested they experienced temperatures in excess of 1200°C, a temperature sufficient to destroy any organic matter they originally contained, while many anhydrous IDPs show no evidence of severe heating. These IDP results indicate that the bulk of the pre-biotic organic matter in extraterrestrial materials formed before aqueous processing, possibly by irradiation of C-bearing ices or by a Fisher-Tropsch type process operating in the gas phase of the nebula or in the interstellar medium.
Observations in psychiatric in-patient settings are used to reduce suicide, self-harm, violence and absconding risk. The study aims were to describe the characteristics of in-patients who died by suicide under observation and examine their service-related antecedents.
A national consecutive case series in England and Wales (2006–2012) was examined.
There were 113 suicides by in-patients under observation, an average of 16 per year. Most were under intermittent observation. Five deaths occurred while patients were under constant observation. Patient deaths were linked with the use of less experienced staff or staff unfamiliar with the patient, deviation from procedures and absconding.
We identified key elements of observation that could improve safety, including only using experienced and skilled staff for the intervention and using observation levels determined by clinical need not resources.
To compare benzodiazepine and z-hypnotic prescribing practices in an inpatient psychiatric unit to best practice standards.
Medication charts of all inpatients in the psychiatric unit, over a 1-week period, were reviewed. Details of current benzodiazepine and z-hypnotic prescriptions were collected. Information collected included the substance prescribed, duration and administration instructions. Feedback was communicated to medical practitioners through a presentation and email. A re-audit was completed 4 months later.
There were increases in total benzodiazepine and z-hypnotic prescribing despite intervention. A reduction of 2 mg occurred in the mean regular dose of benzodiazepine prescribed. Lorazepam was the most prescribed benzodiazepine throughout. In both data sets, at least 50% of regular z-hypnotics and benzodiazepines were initiated before admission. There was an increase of 14% in regular benzodiazepines initiated in hospital exceeding 4 weeks in duration. In neither data collection did regular z-hypnotics initiated in hospital exceed this cut off. A greater number of individuals were in the process of being withdrawn from regular benzodiazepine or z-hypnotic prescriptions in the re-audit. There were minimal improvements in ‘as required’ prescribing as regards documentation of an indication, time limit and maximum dose.
The increase in overall prescribing, despite intervention, maybe because these medications continued to be indicated in the acute presentations needing inpatient treatment. The small improvements in ‘as required’ prescribing patterns suggest that the intervention was limited in effecting change in this area.
3D printing is a versatile fabrication method that offers the potential to realize complex 3D devices with metamaterial characteristics in a single process directly from a computer aided design. However, the range of functional devices that might be realized by 3D printing is limited by the current range of materials that are compatible with a given 3D printing process: fused deposition modelling (FDM), which is a widely used 3D printing method, typically employs only common thermoplastics. Here we describe the development of a magnetic feedstock based on polymer-ferrite composite that is compatible with FDM. The feasibility of the technique is demonstrated by the permittivity and permeability measurement of direct printed blocks and the fabrication of a complex 3D diamond-like lattice structure. The development of printable magnetic composites provides increased design freedom for direct realization of devices with graded electromagnetic properties operating at microwave frequencies.
Endophthalmitis is a vision-threatening inflammation of the inner eye fluids and tissues. Infectious endophthalmitis results from either exogenous or endogenous entry of microbes into the eye. In reported clinical series, exogenous endophthalmitis is much more common than endogenous (or metastatic) endophthalmitis. By far, the most common cause of exogenous infection is intraocular procedures. Until recently, cataract surgery was the most frequently performed type of intraocular procedure, accounting for the greatest number of exogenous endophthalmitis cases. Intravitreal injection has now surpassed cataract surgery as the most frequently performed intraocular procedure and consequently is a significant contributor to the total number of exogenous endophthalmitis cases reported. Exogenous endophthalmitis can also occur after other types of intraocular surgery, including secondary lens implantation, glaucoma filtering surgery, vitrectomy surgery, and corneal transplantation. Organisms may also enter the eye during penetrating trauma, intraocular injection of medication, and contiguous spread into the eye from an infected corneal ulcer. Gram-positive bacteria are the most common cause of exogenous endophthalmitis.
Postoperative endophthalmitis cases from the University of Miami (Bascom Palmer Eye Institute) over an 8-year period (2002 to 2009) demonstrated the incidence of nosocomial endophthalmitis after cataract surgery to be 0.025%. Endophthalmitis occurs after open-globe injuries in 3% to 30% of patients depending on the nature of the injury. The rate of development of Candida endogenous endophthalmitis in patients with documented candidemia has been reported to range from 2.8% to 45%.
Complex faceted features of micrometer sizes and with intense luminescence rise 200-300 nm above the surface of a GaN thin film grown by molecular beam epitaxy on (0001) sapphire. Cathodoluminescence measurements at room temperature and at 8K were used to investigate the luminescence properties of these microfeatures in comparison with those of the background GaN material. The morphology of the micro-features was studied by scanning electron microscopy and by atomic force microscopy.
GaN and related compounds have been considered as promising materials for light emitting devices in the short wavelength visible and UV spectral regions because of their direct, wide band gaps and high luminescence efficiency. Remarkable, rapid success has been achieved in developing devices based on III-V nitrides, which allows these material systems to rival other systems under development . Blue-green LEDs fabricated from InGaN/AlGaN double-heterostructure layers on sapphire substrates by Nichia Chemical Industries in Japan are commercially available, despite the presence of high extended defect densities in the 1010 /cm2 range . In December 1995, an important milestone in the development of nitride lasers was reached; Nakamura et al. in Nichia demonstrated the first nitride-based laser diode which operated at 417 nm under pulsed conditions at room temperature .
The morphology and spatial distribution of luminescence in GaN thin films have been investigated by several research groups , , , although most efforts have been directed to developing appropriate growth conditions for improved film quality. From observations by scanning electron microscopy (SEM) and atomic force microscopy (AFM), Trager-Cowan et al. described an MBE-grown GaN film which contained an assembly of oriented hexagonal crystallites rising above a background of polycrystalline or amorphous material . All the crystallites, oriented in a similar fashion, had roughly the same sizes, 1 or 2 μm across a hexagonal face and about 1 μm high. These crystallites were much brighter than the surrounding background material in panchromatic low-temperature cathodoluminescence (CL) images. Trager-Cowan et al. concluded that the crystallites were of better quality than the background material. They also observed a green emission band, attributed to impurities, which became weaker for higher electron beam voltages, generating luminescence from deeper in the film. From this observation, they concluded that higher quality material is located closer to the film's outer surface. Spatial variation of the luminescence efficiency from MOCVD-grown films has also been observed by Ponce et al. in their room-temperature CL microscopy studies. Their results showed significant nonuniformities in both the band-edge and yellow band emissions. Although they reported no faceted island structures, one of their samples had “marked surface features” and consisted of hexagonal crystals 10 to 50 μm in diameter. The crystals gave strong band-to-band (364 nm) luminescence.
In this paper, the morphology of a GaN film grown on (0001) sapphire by MBE is characterized by SEM and AFM, and CL measurements are used to investigate the luminescence properties of the film at room temperature and at 8K. Some regions of this film are similar to the one described by Trager-Cowan et al.  in having micron sized, brightly luminescent islands. The hexagonal facet angles and bright luminescence of islands in our film also resemble the larger scale, more regularly shaped hexagonal crystals of Ponce et al. . These regions lie on the boundary of excess gallium growth conditions. Our results differ from those of Trager-Cowan in terms of the island morphologies and the spectral character of luminescence from the islands and from the background material. Possible causes of the large variations in luminescence efficiency are discussed.
Lithium bis(oxalato)borate (LiBOB) has gained widespread interest as an electrolyte salt for lithium ion batteries because of its high conductivity, low cost, thermal stability, and adequate solubility in many organic solvents . Cyclic voltammetric data taken on platinum  and carbon  indicate electrochemical stability over a wide potential range.
We show that bis(oxalato)borate (BOB) can be reduced at about 1.75 volts anodic to lithium, by discharging electrolytes at low current density (0.1 mA/cm2) on high surface area carbon electrodes containing a mixture of acetylene and Ketjen carbon blacks. The evidence includes discharge profiles and 11B NMR data. The behavior of discharge plateaus indicates that BOB is reduced to a soluble species with electrolytic properties, and the appearance of a broad 11B NMR peak in the electrolyte indicates that the reduced species undergoes extensive exchange.
Using polarized-neutron reflectivity, one can determine the layer-averaged magnetic structure of films and multilayers with exquisite precision. By employing the closely related phenomenon of grazing-angle diffraction, it is possible to obtain information about the in-plane structure in interfacial layers some tens of Ångstroms thick. We have used polarized-beam methods to study the Y/Gd interface using both reflectivity and grazingangle diffraction and discuss the status of these experiments.
Epitaxial growth of rare-earth superlattices is demonstrated to have opened important new areas of research on magnetic materials. The propagation magnetic order through non-magnetic elements, including its range and anisotropy, has been studied. The importance of magnetostriction in determining the phase diagram is demonstrated by the changes induced by epitaxial clamping. The crystallinity of epitaxial superlattices provides the opportunity to study interfacial magnetism by conventional x-ray and neutron scattering methods.
Thin films of lead zirconate titanate have been fabricated for application to a new family of flexure-wave piezoelectric micromotors that are characterized by low speed and high torque. The high relative dielectric constant and breakdown strength of the films lead to high stored energy densities. Evaluation of the film as a bimorph yielded a value of -88 pC/N for the transverse piezoelectric strain coefficient, d31; the relevant electromechanical coupling factor, k31, calculated thereupon was 0.22. The development of the piezoelectric ultrasonic micromotors from the PZT thin films, and the architecture of the stator structure are described. Nonoptimized prototype micromotors show rotational velocities of 100-300 rpm at drives of 3-5 V.
We report the results of a reflection high energy electron diffraction (RHEED) study on the order-disorder transitions at the (111) and (110) surface of Cu3Au. Our Cu3Au films were epitaxially grown on sapphire substrates with bcc (Nb or Mo-Cr) buffer layers. The (111) and (110) surfaces of Cu3Au are atomically flat as indicated by the RHEED patterns. We use the normalized integrated intensity of the superstructure streaks to measure the long range order parameter. We observed that the surface layers of both (110) and (111) Cu3Au exhibit an apparently continuous order-disorder transition, close to that predicted by mean field theory . The kinetics of surface ordering also were monitored by RHEED after initial deposition of disordered layers, 2 MLs thick, on the ordered Cu3Au templates. In studies of the surface reordering process we find that the RHEED pattern is almost entirely sensitive to the surface layer alone.
The technique of external reflection infrared (IR) spectroscopy is used to study silicon surface chemistry. External reflection is enhanced by implanting a buried cobalt silicide layer in silicon to act as an infrared reflector. The preparation of clean well-ordered surfaces from the ion implanted substrates is demonstrated. The reactions of water and ethanol with Si(100) are investigated.
Delta doping (paused growth doping) was investigated as an alternative to uniformly distributing the dopant in the nitride semiconductor layer. In this work, delta doped layers were produced in MOVPE-grown AlGaN and GaN layers at a susceptor temperature of 1220°C by turning off the group III precursors (TMG and TMA) and introducing into the reactor a silicon precursor Si2H6 (disilane) for a fixed period (pause time) before growth was restarted. The compositional and electrical properties as a function of aluminum content and dopant flux were investigated for nitride layers on 2 inch c-plane sapphire substrates. Secondary ion mass spectroscopy (SIMS) measurements revealed a sharp silicon peak with a FWHM of 5.7 ± 0.6 nm for an Al0.25Ga0.75N sample and 10.0 ± 0.6 nm for a GaN sample with sheet charges of 7.9×1012 cm−2 and 9.9×1012 cm−2,respectively. Room temperature Hall mobility as high as 265 cm2 V−1s−1 for a sheet charge 7.9×1012 cm−2 was demonstrated for delta doped Al0.25Ga0.75N layers, but the mobility enhancement saturated and then decreased with increasing sheet charge. Room temperature sheet charge increased with increasing dopant flux for delta-doped AlGaN and GaN layers. Sheet charge density as high as 2.2×1013 cm−2 and 1.3×1013 cm−2 was measured at room temperature for Al0.25Ga0.75N and GaN delta doped layers, respectively. Under identical doping conditions, the Hall sheet charge of the delta doped Al0.25Ga0.75N layer was approximately half as large as GaN layers. The impurity and electrical characteristics of the delta doped layers are further discussed.
We report on the growth of InGaN films, and the fabrication and characterization of GaN homojunction LEDs and InGaN double heterostructure (DH) LEDs on HVPE GaNon- sapphire substrates. The use of these substrates facilitates the III-nitrides growth process, as it avoids the use of complicated buffer layers. We have achieved InGaN films with strong and sharp band-to-band photoluminescence (PL) from 370 to 540 nm. Typical In 0.o9Ga0. g9N/GaN DH films had double-crystal XRD FWHM ∼ 300 arcsec, and 400 nm peak PL emission with FWHM ∼ 100 meV. DH-LEDs were fabricated with InGaN layers with various compositions, and produced strong electroluminescence (EL) in the blue and blue/green regions.
Stimulated emission characteristics are examined for GaN-AlGaN separate-confinement quantum-well heterostructures grown by MOVPE on 4H-SiC substrates. We specifically focus on comparison of structures with different quantum well active region designs. Polarization resolved edge emission spectra and stimulated emission thresholds are obtained under optical pumping using a stripe excitation geometry. Stimulated emission characteristics are studied as a function of the number of quantum wells in the structure, and are correlated with surface photoluminescence properties. We find reduced stimulated emission thresholds and increased surface photoluminescence intensities as the number of quantum wells is reduced, with the best results obtained for a single-quantum-well structure. These results should provide useful information for the design of GaN-based quantum well lasers.