Regaining a Spatial Dimension: Mechanically Transferrable Two-Dimensional InAs Nanofins Grown by Selective Area Epitaxy.

We report a method for growing rectangular InAs nanofins with deterministic length, width, and height by dielectric-templated selective-area epitaxy. These freestanding nanofins can be transferred to lay flat on a separate substrate for device fabrication. A key goal was to regain a spatial dimension for device design compared to nanowires, while retaining the benefits of bottom-up epitaxial growth. The transferred nanofins were made into devices featuring multiple contacts for Hall effect and four-terminal resistance studies, as well as a global back-gate and nanoscale local top-gates for density control. Hall studies give a 3D electron density 2.5-5 × 1017 cm-3, corresponding to an approximate surface accumulation layer density 3-6 × 1012 cm-2 that agrees well with previous studies of InAs nanowires. We obtain Hall mobilities as high as 1200 cm2/(V s), field-effect mobilities as high as 4400 cm2/(V s), and clear quantum interference structure at temperatures as high as 20 K. Our devices show excellent prospects for fabrication into more complicated devices featuring multiple ohmic contacts, local gates, and possibly other functional elements, for example, patterned superconductor contacts, that may make them attractive options for future quantum information applications.

Achieving short high-quality gate-all-around structures for horizontal nanowire field-effect transistors.

We introduce a fabrication method for gate-all-around nanowire field-effect transistors. Single nanowires were aligned perpendicular to underlying bottom gates using a resist-trench alignment technique. Top gates were then defined aligned to the bottom gates to form gate-all-around structures. This approach overcomes significant limitations in minimal obtainable gate length and gate-length control in previous horizontal wrap-gated nanowire transistors that arise because the gate is defined by wet-etching. In the method presented here gate-length control is limited by the resolution of the electron-beam-lithography process. We demonstrate the versatility of our approach by fabricating a device with an independent bottom gate, top gate, and gate-all-around structure as well as a device with three independent gate-all-around structures with 300, 200, and 150 nm gate length. Our method enables us to achieve subthreshold swings as low as 38 mV dec-1 at 77 K for a 150 nm gate length.

Using Ultrathin Parylene Films as an Organic Gate Insulator in Nanowire Field-Effect Transistors.

We report the development of nanowire field-effect transistors featuring an ultrathin parylene film as a polymer gate insulator. The room temperature, gas-phase deposition of parylene is an attractive alternative to oxide insulators prepared at high temperatures using atomic layer deposition. We discuss our custom-built parylene deposition system, which is designed for reliable and controlled deposition of <100 nm thick parylene films on III-V nanowires standing vertically on a growth substrate or horizontally on a device substrate. The former case gives conformally coated nanowires, which we used to produce functional Ω-gate and gate-all-around structures. These give subthreshold swings as low as 140 mV/dec and on/off ratios exceeding 103 at room temperature. For the gate-all-around structure, we developed a novel fabrication strategy that overcomes some of the limitations with previous lateral wrap-gate nanowire transistors. Finally, we show that parylene can be deposited over chemically treated nanowire surfaces, a feature generally not possible with oxides produced by atomic layer deposition due to the surface "self-cleaning" effect. Our results highlight the potential for parylene as an alternative ultrathin insulator in nanoscale electronic devices more broadly, with potential applications extending into nanobioelectronics due to parylene's well-established biocompatible properties.

Diabetes or war? Incidence of and indications for limb amputation in Lebanon, 2007.

Chronic diseases such as diabetes and vascular disease are a major public health problem in Lebanon, where primary care is not well developed. This study aimed to describe the incidence and indications for limb amputation in Lebanon and identify associated factors (age, sex, level of surgery, length of hospital stay). There were 1.6 amputations per 10 000 persons. The rate of amputation was highest in southern Lebanon at 3.8 per 10 000. The most important indication for surgery was diabetes (59%). Diabetic patients were older (mean age 73 years versus 30 years), more likely to have major surgery (OR = 7.87; 95% CI: 2.83-21.9) and stay in hospital longer (RR = 4.56, 95% CI: 2.41-8.64) than patients with trauma-related amputation. Diabetes prevention, detection and management should be prioritized in any attempt to reduce the current incidence of amputation in Lebanon.

Novel concept suppressing plasma heat pulses in a tokamak by fast divertor sweeping.

One of the remaining challenges in magnetic thermonuclear fusion is survival of the heat shield protecting the tokamak reactor vessel against excessive plasma heat fluxes. Unmitigated high confinement edge localized mode (ELM) is a regular heat pulse damaging the heat shield. We suggest a novel concept of magnetic sweeping of the plasma contact strike point fast and far enough in order to spread this heat pulse. We demonstrate feasibility of a dedicated copper coil in a resonant circuit, including the induced currents and power electronics. We predict the DEMO ELM properties, simulate heat conduction, 3D particles motion and magnetic fields of the plasma and coil in COMSOL Multiphysics and Matlab. The dominant system parameter is voltage, feasible 18 kV yields 1 kHz sweeping frequency, suppressing the ELM-induced surface temperature rise by a factor of 3. Multiplied by other known mitigation concepts, ELMs might be mitigated enough to ensure safe operation of DEMO.

Integrated bioelectronic proton-gated logic elements utilizing nanoscale patterned Nafion.

A central endeavour in bioelectronics is the development of logic elements to transduce and process ionic to electronic signals. Motivated by this challenge, we report fully monolithic, nanoscale logic elements featuring n- and p-type nanowires as electronic channels that are proton-gated by electron-beam patterned Nafion. We demonstrate inverter circuits with state-of-the-art ion-to-electron transduction performance giving DC gain exceeding 5 and frequency response up to 2 kHz. A key innovation facilitating the logic integration is a new electron-beam process for patterning Nafion with linewidths down to 125 nm. This process delivers feature sizes compatible with low voltage, fast switching elements. This expands the scope for Nafion as a versatile patternable high-proton-conductivity element for bioelectronics and other applications requiring nanoengineered protonic membranes and electrodes.

Fast density reconstruction of Li-BES signal on the COMPASS tokamak.

This article describes a fast and automatic reconstruction of the edge plasma electron density from the radiation of energetic Li atoms of the diagnostic beam on the COMPASS tokamak. Radiation is detected by using a CCD camera and by using an avalanche photo-diode system with a temporal resolution of 20 ms and 2 µs, respectively. Both systems are equipped with a 670.8 nm optical filter which corresponds to the lithium 1s22s1-1s22p1 transition. A theoretical model and a data processing procedure of a raw signal to obtain the density profile are described. The reconstruction algorithm provides the absolutely calibrated electron density profiles together with the measurement error estimated from relatively calibrated light profiles; the implementation is performed in Python. Time demanding operations of the code were optimized to provide reconstruction of a single profile within less than 10 ms which makes the code applicable for processing of a large amount of data. Thanks to this calculation speed, it is possible to reconstruct electron density profiles between two consecutive shots on the COMPASS tokamak with 2 µs time resolution.

Filamentary probe on the COMPASS tokamak.

This paper describes a new filamentary probe recently introduced on the COMPASS tokamak. It allows the measurement of electrostatic and magnetic properties of the filaments and their changes in dependence on distance from the separatrix in the region between a divertor and midplane. The probe head is mounted on a manipulator moving the probe radially on a shot-to-shot basis. This configuration is suitable for the long term statistical measurement of the plasma filaments and the measurement of their evolution during their propagation from the separatrix to the wall. The basics of the filamentary probe construction, the evolution of the plasma parameters, and first conditional averages of the plasma filaments in the scrape-off layer of the COMPASS tokamak during the L-mode regime are presented.

Differential action of phenytoin and carbamazepine on cortical interhemispheric responses in young but not in adult rats.

Single as well as paired responses to stimulation of the contralateral sensorimotor cortex were recorded in adult and 12-day-old rats under urethane anesthesia. Carbamazepine (50 mg/kg i.p.) prolonged the peak latencies of single responses in both adult and young rats, while phenytoin (60 mg/kg i.p.) prolonged the latencies in adult animals but shortened them in the young ones. Excitability cycles of the amplitude of the initial positive-negative complex remained uninfluenced by either drug in both age groups. Since solvent alone did not induce any effects in either test, our results demonstrate a qualitative change in the action of phenytoin during development.

Paired-pulse and frequency potentiation of cortical responses in developing rats.

The postnatal development of paired-pulse and frequency potentiations of the first positive and negative components (P1N1) of the cortical interhemispheric response (IHR) was studied in urethane anesthetized rats aged from 7 to 90 days. The paired-pulse potentiation appeared in the rat sensorimotor cortex starting from the age of 15 days. The magnitude of potentiation increased with age. The interpulse interval inducing maximum potentiation shortened from 125 ms in 15-day-old rats to 70 ms in adult rats. Similar results concerning the paired-pulse responses were found for visual cortex but the maturation was somewhat delayed--potentiation first appeared at postnatal day (PND) 18. The frequency potentiation reached adult properties in the sensorimotor cortex by PND 25. There is no time coincidence in the development of the two potentiation phenomena studied, paired pulse potentiation appeared earlier than frequency potentiation.

Family practice residents' learning needs and beliefs about office-based psychological counseling.

BACKGROUND AND OBJECTIVES: Teaching office-based psychological counseling is an essential component of family practice training. Most counseling training has been adapted from other disciplines without adequately identifying residents' learning needs, attitudes, and beliefs about counseling. This study was designed to 1) assess family practice residents' perceived learning needs for counseling, and 2) elicit and clarify their attitudes and beliefs about counseling. METHODS: Three consecutive groups of residents anonymously recorded their questions about psychological counseling. These questions were presented to the residents in focus groups for elaboration and clarification of underlying attitudes and beliefs. A consensus panel then categorized the learning needs and identified residents' attitudes and beliefs. RESULTS: Eighty-six distinct learning need questions were identified. These items clustered into four categories: skill development, problem/patient selection, practice management, and role confusion. Focus group findings identified four major themes: the need for limits and boundaries, limited understanding of change and the therapeutic process, doubts about personal readiness, and difficulty with the integration of mind and body. CONCLUSION: These findings parallel the concerns of physicians in practice and reinforce the need to identify resident concerns about office-based counseling. Failure to identify and respond to learner concerns may limit the effectiveness of teaching efforts in this curricular area.

A natural asymptomatic herpes B virus infection in a colony of laboratory brown capuchin monkeys (Cebus apella).

Herpes B virus (BV) infection of macaques persists in the natural host, but is mainly asymptomatic. However, BV can cause fatal disease in humans and in several non-macaque species such as capuchin monkeys (Cebus apella). The BV infection described here in a colony of capuchin monkeys was persistent but asymptomatic. Initially the infection was detected serologically in five out of seven animals. However, using polymerase chain reaction (PCR) developed specifically for BV, we found the virus in all seven clinically healthy animals. It is probable that the infection was transferred from BV-infected macaques housed in different cages but in the same room for several years. We have no evidence to indicate that similar asymptomatic infections may occur in other New World species but the possibility should not be discounted. We recommend that the housing of capuchin monkeys in close proximity to macaques should be avoided and that greater caution should be used when handling capuchin monkeys and possibly other New World species that have been in contact with macaques. All may act as a source of BV infection in humans, hence routine, repeated testing of all primates is essential.

Pneumomediastinum and subcutaneous emphysema following vaginal delivery. Case report and review of the literature.

A 23-year-old woman, gravida 1, para 0, at 42 weeks of pregnancy gave birth to a healthy female infant without complications except for a 4th-degree tear. Three hours after delivery, her voice was noted to have an unusual nasal quality, she complained of chest pain, and she developed extensive swelling of the neck and upper throat.

Dependence of erythropoietin production on blood oxygen affinity and hemoglobin concentration in rats.

Plasma erythropoietin titers (Ep) were compared in rats subjected to different kinds of systemic hypoxia. Ep increased exponentially, when hypoxia was induced by exposure to simulated altitude (from less than 0.025 IU Ep/ml plasma at sea-level up to 3.65 IU Ep/ml at 7000 m). An acute increase in the O2 affinity of blood augmented Ep production in normal rats but not in rats exposed to hypobaria. Ep also rose exponentially when isovolemic anemia was induced (e.g., 0.5 IU Ep/ml plasma were found at 7 g Hb/dl blood). When the same reduction in blood O2 carrying capacity was produced by CO-inhalation (0.1% CO in air), Ep increased to 5.57 IU/ml plasma. This very high value was considered to be partly due to the very high O2 affinity of carboxyhemoglobin. These results indicate that a left shift in the hemoglobin-O2 dissociation curve produces a stimulation of Ep production, particularly, when the O2-carrying capacity of blood is lowered.

Anti-metrazol effects of nitrazepam during ontogenesis in the rat.

Anti-metrazol effect of nitrazepam was studied in male rats aged 7, 12, 18 and 90 days. Nitrazepam protected all age groups against seizures elicited by metrazol (80 mg/kg s.c.); the 50%-protective dose decreased from 165.7 micrograms/kg in adult rats to 70.2 micrograms/kg in 7-day-old animals. The sensitivity of 7-day-old and adult rats to metrazol is nearly the same, so that we may conclude that nitrazepam exhibits higher anti-metrazol potency in 7-day-old rats than in adult ones.

Phorbol ester causes short term and transient accumulation of pteridines in T cells and in cell lines.

Upon exposure to 12-O-tetradecanoylphorbol 13-acetate, interleukin 2 receptor+ T cells transiently accumulate neopterin and biopterin as was determined by HPLC after iodine oxidation of acidic cell extracts. Pteridines peak at maximally 20 fold levels after 10-20 min and return to initial levels during the following 30-40 min. Resting human peripheral blood mononuclear cells do not react within this short period. TPA elicits similar neopterin and biopterin accumulation kinetics in cell lines such as HL-60, Reh, Jurkat JMN, HeLa and 293, whereby HL-60 and Reh release substantial amounts of these transiently formed pteridines into the medium.