Infrared luminescence of annealed germanosilicate layers

Cataloged from PDF version of article.In the light of growing importance of semiconductor nanocrystals for photonics, we report on the growth and characterization of annealed germanosilicate layers used for Ge nanocrystal formation. The films are grown using plasma enhanced chemical vapor deposition (PECVD) and post-annealed in nitrogen at temperatures between 600 and 1200 degrees C for as long as 2 h. Transmission electron microscopy (TEM), Raman scattering and photoluminescence spectroscopy (PL) has been used to characterize the samples both structurally and optically. Formation of Ge precipitates in the germanosilicate layers have been observed using Raman spectroscopy for a variety of PECVD growth parameters, annealing temperatures and times. Ge-Ge mode at similar to 300 cm(-1) is clearly observed at temperatures as low as 700 degrees C for annealing durations for 45 min. Raman results indicate that upon annealing for extended periods of time at temperatures above 900 degrees C; nanocrystals of few tens of nanometers in diameter inside the oxide matrix and precipitation and interdiffusion of Ge, forming SiGe alloy at the silicon and oxide interface take place. Low temperature PL spectroscopy has been used to observe luminescence from these samples in the vicinity of 1550 nm, an important wavelength for telecommunications. Observed luminescence quenches at 140 K. The photoluminescence data displays three peaks closely interrelated at approximately 1490,, 1530 and 1610 nm. PL spectra persist even after removing the oxide layer indicating that the origin of the infrared luminescent centers are not related to the Ge nanocrystals in the oxide layer. (C) 2013 Elsevier B.V. All rights reserved

Plasma enhanced chemical vapor deposition of low loss as-grown germanosilicate layers for optical waveguides

We report on systematic growth and characterization of low-loss germanosilicate layers for use in optical waveguides. Plasma enhanced chemical vapor deposition (PECVD) technique was used to grow the films using silane, germane and nitrous oxide as precursor gases. Chemical composition was monitored by Fourier transform infrared (FTIR) spectroscopy. N-H bond concentration of the films decreased from 0.43 ×1022 cm -3 down to below 0.06x 1022 cm-3, by a factor of seven as the GeH4 flow rate increased from 0 to 70 seem. A simultaneous decrease of O-H related bonds was also observed by a factor of 10 in the same germane flow range. The measured TE loss rates at λ=632.8 nm were found to increase from are 0.20 ± 0.02 to 6.46 ± 0.04 dB/cm as the germane flow rate increased from 5 to 50 seem, respectively. In contrast, the propagation loss values for TE polarization at λ-1550 nm were found to decrease from 0.32 ± 0.03 down to 0.14 ± 0.06 dB/cm for the same samples leading to the lowest values reported so far in the literature, eliminating the need for high temperature annealing as is usually done for these materials to be used in waveguide devices

ACTS broadband aeronautical experiment

In the last decade, the demand for reliable data, voice, and video satellite communication links between aircraft and ground to improve air traffic control, airline management, and to meet the growing demand for passenger communications has increased significantly. It is expected that in the near future, the spectrum required for aeronautical communication services will grow significantly beyond that currently available at L-band. In anticipation of this, JPL is developing an experimental broadband aeronautical satellite communications system that will utilize NASA's Advanced Communications Technology Satellite (ACTS) as a satellite of opportunity and the technology developed under JPL's ACTS Mobile Terminal (AMT) Task to evaluate the feasibility of using K/Ka-band for these applications. The application of K/Ka-band for aeronautical satellite communications at cruise altitudes is particularly promising for several reasons: (1) the minimal amount of signal attenuation due to rain; (2) the reduced drag due to the smaller K/Ka-band antennas (as compared to the current L-band systems); and (3) the large amount of available bandwidth. The increased bandwidth available at these frequencies is expected to lead to significantly improved passenger communications - including full-duplex compressed video and multiple channel voice. A description of the proposed broadband experimental system will be presented including: (1) applications of K/Ka-band aeronautical satellite technology to U.S. industry; (2) the experiment objectives; (3) the experiment set-up; (4) experimental equipment description; and (5) industrial participation in the experiment and the benefits

Nutritional profile of Syrian refugee children before resettlement

Background The year 2015 marked the highest number of refugees globally and included record numbers of Syrians moving to neighboring countries. Half of the Syrians were children aged ≤18 years. Our study sought to examine undernutrition and overnutrition among a group of Syrian refugee children who underwent medical screening by IOM for resettlement. Methods This is a retrospective review of Syrian refugee children aged 6 to 59 months from January 1, 2015 to December 31, 2016. The World Health Organization (WHO) Stata package computed Z-scores based on available weight and height data. Prevalence estimates of undernutrition (wasting and stunting) and overnutrition (overweight and obesity) were made using WHO standards. Multivariate analysis was used to determine the factors associated with wasting, stunting, and overnutrition, adjusting for age, sex, family size, and country of health assessment. Results A total of 14,552 Syrian refugee children aged 6 to 59 months underwent health assessments in Jordan (43·1%), Lebanon (38·8%), Turkey (7·0%), Greece (6·7%), Egypt (2·4%), and Iraq (2·1%). Overall, this group of Syrian refugee children had a low prevalence of wasting (< 5%) and stunting (< 10%), and high prevalence of overweight or obese (10.6%). Differences were observed in the prevalence of wasting by country of health assessment. In the multiple regression analysis, the prevalence of stunting and overnutrition decreased with increasing age, and being male was associated with overnutrition but not wasting and stunting. Conclusions Findings revealed an overall low prevalence of undernutrition among this group of Syrian children assessed, although prevalence varied by age group. This low prevalence may reflect the effectiveness, as well as expose possible gaps, of refugee nutrition programs or interventions in countries of asylum. Further studies are recommended to evaluate other possible contributors to malnutrition in this refugee group

Nutritional profile of Syrian refugee children before resettlement.

Background: The year 2015 marked the highest number of refugees globally and included record numbers of Syrians moving to neighboring countries. Half of the Syrians were children aged ≤18 years. Our study sought to examine undernutrition and overnutrition among a group of Syrian refugee children who underwent medical screening by IOM for resettlement. Methods: This is a retrospective review of Syrian refugee children aged 6 to 59 months from January 1, 2015 to December 31, 2016. The World Health Organization (WHO) Stata package computed Z-scores based on available weight and height data. Prevalence estimates of undernutrition (wasting and stunting) and overnutrition (overweight and obesity) were made using WHO standards. Multivariate analysis was used to determine the factors associated with wasting, stunting, and overnutrition, adjusting for age, sex, family size, and country of health assessment. Results: A total of 14,552 Syrian refugee children aged 6 to 59 months underwent health assessments in Jordan (43·1%), Lebanon (38·8%), Turkey (7·0%), Greece (6·7%), Egypt (2·4%), and Iraq (2·1%). Overall, this group of Syrian refugee children had a low prevalence of wasting (< 5%) and stunting (< 10%), and high prevalence of overweight or obese (10.6%). Differences were observed in the prevalence of wasting by country of health assessment. In the multiple regression analysis, the prevalence of stunting and overnutrition decreased with increasing age, and being male was associated with overnutrition but not wasting and stunting. Conclusions: Findings revealed an overall low prevalence of undernutrition among this group of Syrian children assessed, although prevalence varied by age group. This low prevalence may reflect the effectiveness, as well as expose possible gaps, of refugee nutrition programs or interventions in countries of asylum. Further studies are recommended to evaluate other possible contributors to malnutrition in this refugee group

Channel and terminal description of the ACTS mobile terminal

The Advanced Communications Technology Satellite (ACTS) Mobile Terminal (AMT) is a proof-of-concept K/Ka-band mobile satellite communications terminal under development by NASA at JPL. Currently the AMT is undergoing system integration and test in preparation for a July 1993 ACTS launch and the subsequent commencement of mobile experiments in the fall of 1993. The AMT objectives are presented followed by a discussion of the AMT communications channel and mobile terminal design and performance

Putative dopamine agonist (KB220Z) attenuates lucid nightmares in PTSD patients: Role of enhanced brain reward functional connectivity and homeostasis redeeming joy

Background Lucid dreams are frequently pleasant and training techniques have been developed to teach dreamers to induce them. In addition, the induction of lucid dreams has also been used as a way to ameliorate nightmares. On the other hand, lucid dreams may be associated with psychiatric conditions, including Post-Traumatic Stress Disorder (PTSD) and Reward Deficiency Syndrome-associated diagnoses. In the latter conditions, lucid dreams can assume an unpleasant and frequently terrifying character. Case presentations We present two cases of dramatic alleviation of terrifying lucid dreams in patients with PTSD. In the first case study, a 51-year-old, obese woman, diagnosed with PTSD and depression, had attempted suicide and experienced terrifying lucid nightmares linked to sexual/physical abuse from early childhood by family members including her alcoholic father. Her vivid “bad dreams” remained refractory in spite of 6 months of treatment with Dialectical Behavioral Therapy (DBT) and standard pharmaceutical agents which included prazosin, clonidie and Adderall. The second 39-year-old PTSD woman patient had also suffered from lucid nightmares. Results The medication visit notes reveal changes in the frequency, intensity and nature of these dreams after the complex putative dopamine agonist KB220Z was added to the first patient’s regimen. The patient reported her first experience of an extended period of happy dreams. The second PTSD patient, who had suffered from lucid nightmares, was administered KB220Z to attenuate methadone withdrawal symptoms and incidentally reported dreams full of happiness and laughter. Conclusions These cases are discussed with reference to the known effects of KB220Z including enhanced dopamine homeostasis and functional connectivity of brain reward circuitry in rodents and humans. Their understanding awaits intensive investigation involving large-population, double-blinded studies

A simple approach for the fabrication of 3D microelectrodes for impedimetric sensing

In this paper, we present a very simple method to fabricate three-dimensional (3D) microelectrodes integrated with microfluidic devices. We form the electrodes by etching a microwire placed across a microchannel. For precise control of the electrode spacing, we employ a hydrodynamic focusing microfluidic device and control the width of the etching solution stream. The focused widths of the etchant solution and the etching time determine the gap formed between the electrodes. Using the same microfluidic device, we can fabricate integrated 3D electrodes with different electrode gaps. We have demonstrated the functionality of these electrodes using an impedimetric particle counting setup. Using 3D microelectrodes with a diameter of 25 μm, we have detected 6 μm-diameter polystyrene beads in a buffer solution as well as erythrocytes in a PBS solution. We study the effect of electrode spacing on the signal-to-noise ratio of the impedance signal and we demonstrate that the smaller the electrode spacing the higher the signal obtained from a single microparticle. The sample stream is introduced to the system using the same hydrodynamic focusing device, which ensures the alignment of the sample in between the electrodes. Utilising a 3D hydrodynamic focusing approach, we force all the particles to go through the sensing region of the electrodes. This fabrication scheme not only provides a very low-cost and easy method for rapid prototyping, but which can also be used for applications requiring 3D electric field focused through a narrow section of the microchannel. © 2015 IOP Publishing Ltd