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Giant electromagnetic pulses (EMP) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMP emission is caused by the acceleration of hot electrons inside the target, which produce radiation across a wide band from DC to terahertz frequencies. Improved understanding and control of EMP is vital as we enter a new era of high repetition rate, high intensity lasers (e.g. the Extreme Light Infrastructure). We present recent data from the VULCAN laser facility that demonstrates how EMP can be readily and effectively reduced. Characterization of the EMP was achieved using B-dot and D-dot probes that took measurements for a range of different target and laser parameters. We demonstrate that target stalk geometry, material composition, geodesic path length and foil surface area can all play a significant role in the reduction of EMP. A combination of electromagnetic wave and 3D particle-in-cell simulations is used to inform our conclusions about the effects of stalk geometry on EMP, providing an opportunity for comparison with existing charge separation models.
Background: Disgust is thought to play a prominent role in multiple anxiety disorders and fears, including spider phobia, though little attention has been given to specific treatment strategies that may be effective for multiple disgust-based fears. Aims: In the present study, we evaluated contamination-focused exposure as a potential transdiagnostic treatment strategy for disgust-based fears in a spider fearful sample. Method: Women with significant spider fear were randomized to three 30-minute sessions of exposure therapy involving repeated contact with a dirt mixture (n=17) or a waitlist control condition (n=17). Assessments of spider fear and disgust were administered at baseline and at one-week posttreatment. Results: At high (but not low) levels of pretreatment disgust propensity, exposure led to lower in vivo spider fear and perceived danger than waitlist, though exposure had no effects on spider-related disgust. Similar effects of exposure on spider fear were found at high levels of pretreatment spider-related disgust. Exposure also reduced fear and danger perceptions, but not disgust, related to a separate contamination assessment (touching a toilet). No effects of treatment were found on self-report measures of spider fear or disgust propensity. Conclusions: These findings suggest contamination-focused exposure therapy may be an effective transdiagnostic treatment strategy for individuals with elevated disgust propensity. Limitations and directions for future research are discussed.
To explore the views of non-morbidly obese people (BMI 30–40 kg/m2) with type 2 diabetes regarding: (a) the acceptability of bariatric surgery (BS) as a treatment for type 2 diabetes, and (b) willingness to participate in randomised controlled trials comparing BS versus non-surgical intervention.
Despite weight management being a key therapeutic goal in type 2 diabetes, achieving and sustaining weight loss is problematic. BS is an effective treatment for people with morbid obesity and type 2 diabetes; it is less certain whether non-morbidly obese patients (BMI 30–39.9 kg/m2) with type 2 diabetes benefit from this treatment and whether this approach would be cost-effective. Before evaluating this issue by randomised trials, it is important to understand whether BS and such research are acceptable to this population.
Non-morbidly obese people with type 2 diabetes were purposively sampled from primary care and invited to participate in semi-structured interviews. Interviews explored participants’ thoughts surrounding their diabetes and weight, the acceptability of BS and the willingness to participate in BS research. Data were analysed using Framework Analysis.
To investigate potential sources and risks associated with multidrug-resistant (MDR) bacteria in a deployed US military hospital.
Retrospective analysis of factors associated with recovery of MDR bacteria, supplemented by environmental sampling.
The largest US military hospital in Afghanistan.
US and Afghan patients with positive bacterial culture results, from September 2007 through August 2008.
Microbiologic, demographic, and clinical data were analyzed. Potential risk factors included admission diagnosis or mechanism of injury, length of stay, gender, age, and nationality (US or Afghan). Environmental sampling of selected hospital high-touch surfaces and equipment was performed to help elucidate whether environmental MDR bacteria were contributing to nosocomial spread.
A total of 266 patients had 411 bacterial isolates that were identified during the study period, including 211 MDR bacteria (51%). Gram-negative bacteria were common among Afghan patients (241 [76%] of 319), and 70% of these were classified as MDR. This included 58% of bacteria recovered from Afghan patients within 48 hours of hospital admission. The most common gram-negative bacteria were Escherichia coli (53% were MDR), Acinetobacter (90% were MDR), and Klebsiella (63% were MDR). Almost one-half of potential extended-spectrum β-lactamase (ESBL) producers were community acquired. Of 100 environmental swab samples, 18 yielded MDR bacteria, including 10 that were Acinetobacter, but no potential ESBL-producing bacteria.
Gram-negative bacteria from Afghan patients had high rates of antimicrobial resistance. Patients experiencing Complex trauma and prolonged hospital stays likely contribute to the presence of MDR bacteria in this facility. However, many of these patients had community-acquired cases, which implies high rates of colonization prior to hospital admission.
High resolution spectroscopy of Nd3+ in Potassium Lithium Yttrium Fluoride (KLiYF5 ) at ≤80 K reveals two crystal-field sites which are equally populated independent of concentration. Site selective excitation of photoluminescence distinguishes each site's contribution to the spectra. The analysis of integrated line intensities reveals a bidirectional energy transfer between Nd3+ ions in different sites. A rapid increase in transfer rate with increasing Nd concentration is explained only if non-radiative transfer via exchange interaction contributes strongly to the effect. The observed relative decrease with increasing concentration of those emission lines which overlap strongly with opposite-site absorption lines implies that radiative transfer is also important. The energy transfer strongly depends on temperature (2 K – 80 K) which indicates the participation of phonons.
Expanding the crystal field in terms of operators that transform as the irreducible representations of the Td group leads to an intuitive interpretation of the crystal-field parameters. We apply this method to the crystal field experienced by Nd3+ dopants in the laser crystals YLiF4, YVO4, and KLiYF5.
Suspended particle display (SPD) can be controlled in transparency by applying a.c. voltage. We found new synthesized particles for SPD and methods for making them fine. Three new SPD particles showing different colors have been found: δ-herapathite, 1,10-phenanthroline-iodine complex and pyrazinophenanthroline-iodine complex as showing red, blue, purple, respectively. Recrystallization and ultrasonic treatment were found to make them fine crystals. Accordingly, transparency, stability for sedimentation and thermal stability were improved.
The surface morphology of 40-MHz PECVD SiNx films is investigated. We report on the correlation between the deposition conditions, bulk properties, and surface roughness of these TFT insulators. The roughness is measured with atomic-force microscopy, AFM. A link will be presented between the AFM properties and the effects of hydrogen dilution during deposition: gas composition and rf-power-density (P) dependences will be discussed. An increase of the surface roughness to 3.7 nm is observed upon H2 dilution and P increase, ascribed to enhanced ion bombardment of the surface during growth.
High deposition rates and good quality electrical properties and thickness uniformities over large areas are required for all three films (SiNx, a-Si:H and n+ a-Si:H) composing the thin film transistors (TFTs) for the AMLCD industry, while maintaining high tool up-time and low particle formation. Generally these conditions have been achieved for most single-panel multichamber PECVD systems; however, it has become increasingly apparent that a compromise is drawn between the TFT mobility and the deposition rate of the a-Si:H layer. Thus it becomes essential to clearly assess the industry requirements for both deposition rates as well as TFT performance for the different device structures used for AMLCDs, and to discover and control these underlying material properties.
The TEL VHF (40/60 MHz) PECVD system produces high quality, low defect density a- Si:H at deposition rates exceeding 1500 Å/min when analyzed by FTIR, CPM, photo and dark conductivity. Even though the low deposition rate a-Si:H exhibits very similar bulk properties, higher mobility TFTs are produced with a-Si:H deposited at lower RF power. Having both a high ion flux and low ion energy in the SiH4 discharge are likely the most critical conditions for controlling the a-Si:H quality and thus the TFT mobility. Increasing the RF frequency enhances both of these effects, as well as provides a higher deposition rate for a given power density and a higher power threshold for particle/powder formation. For these reasons it is likely a 40/60 MHz plasma will produce better performing TFTs for a given deposition rate when compared with a conventional 13.56 MHz system. Other process conditions such as diluting the SiH4 in H2 or Ar also seem to play an important role in the optoelectronic properties of the a-Si:H film and ultimately the TFT performance.
We apply a number of complementary characterization techniques including electron paramagnetic resonance, optical absorption, and photoluminescence spectroscopies to characterize a wide range of different ZnO phosphor powders. We generally observe a good correlation between the 510-nm green emission intensity and the density of paramagnetic isolated oxygen vacancies. In addition, both quantities are found to peak at a free-carrier concentration ne, of about 1.4 × 1018 cm-3. We also find that the green emission intensity can be strongly influenced by free-carrier depletion at the particle surface, especially for small particles and/or low doping. Our data suggest that the green PL in ZnO phosphors is due to the recombination of electrons in singly occupied oxygen vacancies with photoexcited holes in the valence band.
We have fabricated a poly-Si TFT using a novel oxidation method, which improves the surface roughness at the interface between the poly-Si layer and the gate oxide layer. Compared with the poly-Si TFTs fabricated by the conventional oxidation method, the proposed poly-Si TFT exhibits the remarkable enhancement of the electrical parameters, such as the subthreshold swing and the threshold voltage. It is observed that the proposed poly-Si TFT has a higher dielectric strength and the device characteristics are not degraded significantly after an electrical stress. The improvement of the surface roughness at oxide/poly-Si interface is found to be critical to enhance the device performance.
Poly-Si TFTs with high field effect mobility are fabricated by using PECVD SiO2 layer deposited with a new method: two-step (graded) oxide deposition. To adjust stoichiometry of the poly-Si/oxide interface and the bulk oxide layer, the double layer oxide films were deposited. The oxide films near the interface were deposited with high N2O/SiH4 gas ratio to obtain the stoichiometric layer for good matching between poly-Si and SiO2. The remaining bulk oxide films were deposited with low N2O/SiH4 gas ratio. The composition of the bulk oxide film was measured by using ESCA and the interface layer was analized with ESR. The poly-Si TFT with the double layer gate oxide resulted to the better performance than conventional TFT wth single layer gate oxde.
The field emission characteristics of the Si emitters and the diamond coated Si emitters are investigated. The Fowler-Nordheim plots of the two types of Si emitters show linear slopes. It means that the I-V characteristics follow the Fowler-Nordheim relation. Field emission for the two types of diamond coated Si emitters exhibits significant enhancement both in turn-on voltage and total emission current. The Raman spectrum shows that the high intensity graphite peak is observed with diamond peak and thereby large amounts of graphite may be included in the diamond grain boundary. It seems to be thought that the graphite participates in the low field emission. However, further investigations are needed to understand whether the graphite may enhance the emission characteristics of diamond or not.
We have examined the material properties and operation of bottom-gate amorphous silicon thin film transistors (TFTs) using temperature measurements of the subthreshold current. From the derivative of current activation energy with respect to gate bias, we have deduced information about the density of states for several different transistor types. We have demonstrated that, in TFTs with thin active layers and top nitride passivation, the current conduction channel moves from the gate insulator interface to the passivation insulator interface as the transistor switches off. Our 2D simulations clarify these experimental results. We have examined the effect of bias stress on the transistors and analyzed the resulting reduction in the subthreshold slope. Based on these results, we have extended our analytic amorphous silicon TFI SPICE model to include the effect of bias stress.