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We have grown GaN and AlGaN nanowires on Si (111) substrates with gas-source molecular beam epitaxy (MBE). No metal catalysts were used. The nanowires displayed a number of interesting materials properties, including room-temperature luminescence intensity greater than that of free-standing HVPE-grown GaN, relaxed lattice parameters, and the tendency of nanowires dispersed in solvents to align in response to electric fields. The wires were well separated, 50-250 nm in diameter, and grew to lengths ranging from 2 µm to 7 µm. Transmission electron microscopy indicated that the wires were free of defects, unlike the surrounding matrix layer. [ABSTRACT FROM AUTHOR]

We have measured singly clamped cantilever mechanical-resonances in ensembles of as-grown gallium nitride nanowires (GaN NWs), from 12?K to 320?K. Resonance frequencies are approximately linearly dependent on temperature near 300?K with relative shifts of 40?±?20?ppm/K, consistent with temperature-dependent elastic moduli. Below 100?K, we find that some GaN NWs have mechanical quality factors well above 400 000, at mechanical resonance frequencies near 1 MHz. We also observe a correlation between increased amplitude of dissipation and increased temperature dependence of resonance frequencies. The microwave homodyne detection technique we use is simple, allows for the investigation of as-grown or processed NWs, and is sensitive enough to observe the thermal motion of individual NWs while providing for the simultaneous measurement of large ensembles of NW mechanical resonances. [ABSTRACT FROM AUTHOR]

We present a near-field scanning microwave microscope (NSMM) that has been configured for imaging photovoltaic samples. Our system incorporates a Pt-Ir tip inserted into an open-ended coaxial cable to form a weakly coupled resonator, allowing the microwave reflection S11 signal to be measured across a sample over a frequency range of 1 GHz - 5 GHz. A phase-tuning circuit increased impedance-measurement sensitivity by allowing for tuning of the S11 minimum down to -78 dBm. A bias-T and preamplifier enabled simultaneous, non-contact measurement of the DC tip-sample current, and a tuning fork feedback system provided simultaneous topographic data. Light-free tuning fork feedback provided characterization of photovoltaic samples both in the dark and under illumination at 405 nm. NSMM measurements were obtained on an inhomogeneous, third-generation Cu(In,Ga)Se2 (CIGS) sample. The S11 and DC current features were found to spatially broaden around grain boundaries with the sample under illumination. The broadening is attributed to optically generated charge that becomes trapped and changes the local depletion of the grain boundaries, thereby modifying the local capacitance. Imaging provided by the NSMM offers a new RF methodology to resolve and characterize nanoscale electrical features in photovoltaic materials and devices. [ABSTRACT FROM AUTHOR]

A means of reproducibly fabricating stable cw lasers in rare-earth-doped Ti:LiNbO3 has been demonstrated through judicious choice of waveguide orientation. Z-propagating waveguides have been fabricated in Nd- and Er-diffused Ti:LiNbO3 and room-temperature laser operation with greatly reduced photorefractive instability has been obtained. The reduced photorefractive damage susceptibility in this waveguide configuration has led to the realization of a 980 nm pumped laser in Er:Ti:LiNbO3, with a threshold of 10.5 mW of absorbed pump power and a slope efficiency of 8.5%. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Talks about the risks of giving drugs to pregnant women. Reason for the difficulty in predicting the effects of a given drug on the human fetus based on experimental animal data; Risks of hydantoins to the fetus; Effects of trimethadione to fetus.

Catalyst-free GaN nanowires with InGaN quantum disks (QDs) were characterized by scanning/transmission electron microscopy (S/TEM) and photoluminescence. A variety of structures, from QDs with large strain fields to apparently strain free QDs were observed. TEM lattice imaging revealed dislocations in the QD regions of the samples. Stacking faults were also observed and appear to be associated with the GaN growth temperature rather than the presence of indium. Energy dispersive X-ray spectroscopy in the TEM revealed indium concentrated in stacking faults but not always localized in the QD regions. Photoluminescence spectra show a red-shift, possibly associated with indium concentration. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We report on the fabrication of a GaN nanowire probe for near-field scanning microwave microscopy. A single nanowire was Pt-bonded to a commercial Si cantilever prior to evaporation of a Ti/Al coating to provide a microwave signal pathway. Testing over a microcapacitor calibration sample shows the probe to have capacitance resolution of at least 0.7 fF with improved sensitivity and reduced uncertainty compared with a commercial microwave probe. High wear resistance of the defect-free nanowire enabled it to maintain a tip radius of 150 nm after multiple contact-mode scans while demonstrating nanometer-scale topographical resolution. [ABSTRACT FROM AUTHOR]

Focuses on several anticonvulsant agents and their potential adverse behavioral and cognitive effects on epileptic children. Phenobarbital; Phenytoin; Carbamazepine; Clonazepam;

Focuses on several inactive ingredients in pharmaceutical products and their possible adverse effects. Benzyl alcohol; Propylene glycol; Lactose; Sulfites; Saccharin.

Abstract. Length of stay data collected for high-risk newborn infants admitted to a tertiary care children's hospital neonatal unit over a 6-year period were compared with mean and outlier lengths of stay published in the Federal Register as part of a proposed system for prospective payment of hospital cost by diagnosis-related groupings (DRGs). We found that the classification system for newborns markedly underestimated the number of days required for the treatment of these infants. The use of the geometric mean instead of the arithmetic mean as the measure of central tendency was a significant contributor to the discrepancy, especially in those subgroups with bimodal frequency distributions of lengths of stay. Another contributor to the discrepancy was the lack of inborn patients in the children's hospital cohort. The system of prospective payments, as outlined, does not take into account several factors that have a strong influence on length of stay such as birth weight (which requires more than three divisions to serve as an effective predictor), surgery, outborn status, and ventilation. Implementation of the system described in the Federal Register would severely discourage tertiary care referral hospitals from providing neonatal intensive care. Pediatrics 1985;76:104-109; diagnosis-related groups, tertiary care, high-risk newborn. [ABSTRACT FROM AUTHOR]

We present a de-embedding roadmap for extracting parasitic elements of a nanowire (NW) metal semiconductor field effect transistor (MESFET) from full two-port scattering-parameter measurements in 0.1-25 GHz range. The NW MESFET is integrated in a microwave coplanar waveguide structure. A conventional MESFET circuit model is modified to include capacitors of small value that is non-negligible in NW devices. We follow a step-by-step removal of external elements and an iteration search for optimized model data. The fitted model indicates good agreement with experimental data. This letter reflects a significant step toward full circuit modeling of NW MESFETs under normal operating conditions. [ABSTRACT FROM AUTHOR]

We report high mechanical quality factors Q for GaN nanowire cantilevers grown by molecular beam epitaxy. Nanowires with 30–500 nm diameters and 5–20 μm lengths having resonance frequencies from 400 kHz to 2.8 MHz were measured. Q near room temperature and 10-4 Pa ranged from 2700 to above 60 000 with most above 10 000. Positive feedback to a piezoelectric stack caused spontaneous nanowire oscillations with Q exceeding 106. Spontaneous oscillations also occurred with direct e-beam excitation of unintentionally doped nanowires. Doped nanowires showed no oscillations, consistent with oscillation arising via direct actuation of piezoelectric GaN. [ABSTRACT FROM AUTHOR]

Discusses issues on the prescription of generic drugs. Focuses on issues concerning generic prescribing. Bioavailability of a drug product; Stance of the Committee on Drugs of the American Academy of Pediatrics on generic prescribing; Duty of physicians to patients.

Presents a review by the Committee on Drugs of the American Academy of Pediatrics on the use of iodides in the therapy of asthma and other pulmonary diseases in infants. Dosage recommendations of potassium iodides; Effectiveness of iodides; Effects of iodides on the thyroid; Recommendations.

Laser-assisted atom probe tomography (L-APT) was used to examine superconducting TiN/Ti/TiN trilayer films with nominal respective thicknesses of 5/5/5 (nm). Such materials are of interest for applications that require large arrays of microwave kinetic inductance detectors. The trilayers were deposited on Si substrates by reactive sputtering. Electron energy loss microscopy performed in a scanning transmission electron microscope (STEM/EELS) was used to corroborate the L-APT results and establish the overall thicknesses of the trilayers. Three separate batches were studied where the first (bottom) TiN layer was deposited at 500°C (for all batches) and the subsequent TiN/Ti bilayer was deposited at ambient temperature, 250°C, and 500°C, respectively. L-APT rendered an approximately planar TiN/Si interface by making use of plausible mass-spectral assignments to N 3 1+ , SiN 1+ , and SiO 1+ and N 1+ and N 2 N phase was also revealed by L-APT. Neither L-APT nor STEM/EELS rendered sharp Ti/TiN interfaces and the contrast between these layers diminished with increased film deposition temperature. L-APT also revealed that hydrogen was present in varying degrees in all samples including control samples that were composed of single layers of Ti or TiN.1+ prevented their use in rendering the TiN/Si interface upon reconstruction. The non-superconducting Ti 2 N phase was also revealed by L-APT. Neither L-APT nor STEM/EELS rendered sharp Ti/TiN interfaces and the contrast between these layers diminished with increased film deposition temperature. L-APT also revealed that hydrogen was present in varying degrees in all samples including control samples that were composed of single layers of Ti or TiN., (Published by Elsevier Ltd.)

We investigated an Er(3+)/Yb(3+) codoped silicate glass as a host material for waveguide lasers operating near 1.5 microm. Spectroscopic properties of the glass are reported. Waveguide lasers were fabricated by K(+)-ion exchange from a nitrate melt. The waveguides support a single transverse mode at 1.5 microm. An investigation of the laser performance as a function of the Yb:Er ratio was performed, indicating an optimal ratio of approximately 5:1. Slope efficiencies of as great as 6.5% and output powers as high as 19.6 mW at 1.54 microm were realized. The experimental results are compared with a waveguide laser model that is used to extract the Er(3+) upconversion coefficients and the Yb(3+)-Er(3+) cross-relaxation coefficients. The results indicate the possibility of obtaining high-performance waveguide lasers from a durable silicate host glass.

Waveguide lasers operating near 1092 and 1076 nm were fabricated in Z-cut Nd-Ti codiffused LiTaO(3). The Nd diffusion was at 14000 degrees C for 120 h. Samples from two wafers were examined. The Nd film starting thickness was 7 nm in wafer 1 and 15 nm in wafer 2. Ti stripes, 8-15 microm wide, were diffused at 1500 degrees C for 4 h for wafer 1 (130-nm stripe thickness) and 2 h forwafer 2 (100-nm stripe thickness). Pumping was at 750 nm. Threshold occurred at 330 mW of absorbedpump power for the best waveguides from wafer 1 and100 mW for the best waveguides from wafer 2. The slope efficiency of the latter was 0.07%.

A Y-branch channel waveguide laser operating near 1057 nm was fabricated by electric-field-assisted ion exchange in Nd-doped silicate glass. The overall length was 24 mm. Optical pumping was performed with a cw Ti:sapphire laser. Mirrors were bonded to the polished waveguide facets. The slope efficiency was 5.1% when a 4%-transmitting output coupler was used. Threshold was reached at 26-mW absorbed pump power. The device exhibited a single-pass small-signal gain of 0.034 dB/mW when operated as an amplifier. The 3-dB splitting loss of the Y-branch structure was overcome when the absorbed pump power was approximately 85 mW.

Channel waveguides fabricated in Nd-doped glass were used as gain elements for extended-cavity lasers. End-fire pumping was performed with a Ti:sapphire laser operating at 807 nm. The 4-nm FWHM output spectrum was centered near 1057 nm. Slope efficiencies were typically 4-11%, with thresholds near 20 mW. Active mode locking and Q switching were separately performed; mode-locked pulse widths were roughly 80 ps FWHM. Q-switched peak power was 1.2 W. The cw output narrowed to 7 GHz and tuned over a range of 24 nm when a grating provided feedback; single-frequency operation resulted when a high-reflectivity étalon was added.

A continuous-wave integrated-optic channel waveguide laser operating at 1.057 microm has been fabricated in neodymium-doped soda-lime-silicate laser glass. The device was end-fire pumped with the 0.528-microm line of an argon-ion laser. Threshold for laser action occurs for an absorbed pump power of 31 mW. The slope efficiency for the integrated-optic laser is estimated to be 0.5%. Field-assisted ion exchange in a eutectic melt of CaNO(3) and KNO(3) was used to form the waveguide.

Depression of the surface index of Ti:LiNbO(3) channel waveguides by secondary diffusion of MgO forms a buffer layer that optically isolates the guided modes from attenuation caused by electrodes placed over the guides. For x-cut, z-propagating mode-conversion devices, we find high stability to optical drift when a dc voltage as high as 60 V is applied to electrodes (typical gap of 5 microm) to establish bias operating points. Photoconductivity is found to limit the long-term stability. Devices operating at 0.633-microm wavelength generally suffer significant drift in their mode-conversion efficiency when 100 microW or more of throughput power is present and a bias of 14 V is used. 10-microW throughput at the same wavelength is found to be stable over an 8-h period. At 0.8-microm wavelength, bias voltages as high as 60 V may be used for stable operation even at 100-microW optical throughput.

We describe the fabrication of optical waveguides in LiTaO(3) using proton exchange in hot benzoic acid. All specimens analyzed were X cut. An increase in surface extraordinary index of ~0.14 has been observed for samples exchanged for 3 h at a melt temperature of 249 degrees C. No change was observed in the ordinary index. Waveguide fabrication was facilitated by further baking the samples for an extended period of time at a temperature hotter than the acid melt. The latter technique also served to minimize the surface damage that is characteristic of acid baths exceeding roughly 4 h. The depth of proton exchange in X-cut LiTaO(3) appears to be considerably less than would be the case for X-cut LiNbO(3) under the same conditions.

Second-harmonic generation in the form of Cerenkov radiation has been used to make direct, contact-free measurements of the effective indices of guided modes in LiNbO(3) channel waveguides. X-cut substrates were used, and channels oriented along the y axis were formed by either proton exchange or titanium indiffusion. For end-fire TE excitation, the Cerenkov harmonic radiates forward at a shallow angle into the substrate, leaves the output facet of the substrate, and appears as bright bands in the far field. These bands are seen to form a one-to-one correspondence with the m lines that are due to guided modes when a prism coupler is simultaneously clamped to the sample surface. The effective indices of the guided modes can be obtained by a simple calculation that involves only the substrate index and the angle at which the Cerenkov harmonic is radiated into the substrate. This technique permits effective index measurements of cladded waveguides where prism coupler measurements cannot be made. Examples of the technique in which index oil is used as a guide overlayer are given.

Channel waveguides fabricated in LiNbO(3) substrates by proton exchange in melts of benzoic acid have been analyzed by secondary-ion mass spectroscopy. The depletion of lithium from the waveguide regions, owing to proton exchange, was found to depend to a strong degree on guide width as well as diffusion time for common (249 degrees C) ion-exchange temperatures. In addition to a reduced depth, a guide formed by diffusing through a 6-microm-wide metallic aperture for 10 min suffered 60% less lithium depletion near its surface than one formed by diffusing through a 12-microm aperture for the same time. Optical measurements were performed at 1060 and 1320 nm in guides of width ranging from 5 to 10 microm.