Performance of silicon nanocrystal non-volatile memory devices under various programming mechanisms

Non-volatile memory devices based on silicon nanocrystal synthesized with very low energy Si+ implantation are fabricated. Memory performance under various programming mechanisms including Fowler-Nordheim (FN), drain-bias channel-hot-electron (DCHE), and source-bias channel-hot-electron (SCHE) has been investigated. It is observed that the DCHE yields the largest memory window among the three programming mechanisms. The DCHE and SCHE have similar endurance characteristics, but the SCHE has a longer retention time than the DCHE. Both the DCHE and SCHE have a larger memory window, a better endurance and a longer retention time as compared to the FN. Explanations to the phenomena are given.     

Comparison of the Reaction Systems ZrO2-Si3N4 and TiO2-Si3N4

Reaction mechanisms occurring in the systems ZrO2-Si₃N₄ and TiO2-Si₃N₄ have been compared. The thermodynamics of several overall reaction mechanisms have been analyzed, including the effects of the gas phase composition to determine the most energetically favorable course of each reaction .     

Interregional migration in an extended input-output model

"This article develops a two-region version of an extended input-output model that disaggregates consumption among employed, unemployed, and inmigrant households, and which explicitly models the influx into a region of migrants to take up a proportion of any jobs created in the regional economy. The model is empirically tested using real data for the Scotland (UK) regions of Strathclyde and Rest-of-Scotland. Sets of interregional economic, demographic, demo-economic, and econo-demographic multipliers are developed and discussed, and the effects of a range of economic and demographic impacts are modeled. The circumstances under which Hawkins-Simon conditions for non-negativity are breached are identified, and the limits of the model discussed."     

Long-Term Sex- and Genotype-Specific Effects of 56Fe Irradiation on Wild-Type and APPswe/PS1dE9 Transgenic Mice

Space radiation presents a substantial threat to travel beyond Earth. Relatively low doses of high-energy particle radiation cause physiological and behavioral impairments in rodents and may pose risks to human spaceflight. There is evidence that ⁵⁶Fe irradiation, a significant component of space radiation, may be more harmful to males than to females and worsen Alzheimer’s disease pathology in genetically vulnerable models. Yet, research on the long-term, sex- and genotype-specific effects of ⁵⁶Fe irradiation is lacking. Here, we irradiated 4-month-old male and female, wild-type and Alzheimer’s-like APP/PS1 mice with 0, 0.10, or 0.50 Gy of ⁵⁶Fe ions (1GeV/u). Mice underwent microPET scans before and 7.5 months after irradiation, a battery of behavioral tests at 11 months of age and were sacrificed for pathological and biochemical analyses at 12 months of age. ⁵⁶Fe irradiation worsened amyloid-beta (Aβ) pathology, gliosis, neuroinflammation and spatial memory, but improved motor coordination, in male transgenic mice and worsened fear memory in wild-type males. Although sham-irradiated female APP/PS1 mice had more cerebral Aβ and gliosis than sham-irradiated male transgenics, female mice of both genotypes were relatively spared from radiation effects 8 months later. These results provide evidence for sex-specific, long-term CNS effects of space radiation.     

ADDRESSING SUSTAINABILITY AND THE ENVIRONMENT DURING EMERGENCY DROUGHT RELIEF IN MOYALE, NORTH KENYA

During the period 1999–2000, North Kenya experienced extended drought, which resulted in severe pressure on available water resources and increased mortality of livestock. In response, Action Against Hunger (an international relief agency with project-specific funding from the EC Humanitarian Aid Office) implemented an emergency water-resource programme in the Moyale District. This paper examines some of the sustainability issues relating to such implementations and their impact upon the fragile semi-arid pastoral environment of the region. Specific aspects are drawn from the Moyale programme to illustrate what is often a complex situation. The challenge is how to strike the balance between the short-term needs of an emergency response and the long-term aims of sustainable development and use of resources.     

Microheated substrates for patterning cells and controlling development

Here, we seek to control cellular development by devising a means through which cells can be subjected to a microheated environment in standard culture conditions. Numerous techniques have been devised for controlling cellular function and development via manipulation of surface environmental cues at the micro- and nanoscale. It is well understood that temperature plays a significant role in the rate of cellular activities, migratory behavior (thermotaxis), and in some cases, protein expression. Yet, the effects and possible utilization of micrometer-scale temperature fields in cell cultures have not been explored. Toward this end, two types of thermally isolated microheated substrates were designed and fabricated, one with standard backside etching beneath a dielectric film and another with a combination of surface and bulk micromachining and backside etching. The substrates were characterized with infrared microscopy, finite element modeling, scanning electron microscopy, stylus profilometry, and electrothermal calibrations. Neuron culture studies were conducted on these substrates to 1) examine the feasibility of using a microheated environment to achieve patterned cell growth and 2) selectively accelerate neural development on regions less than 100 /spl mu/m wide. Results show that attached neurons, grown on microheated regions set at 37/spl deg/C, extended processes substantially faster than those incubated at 25/spl deg/C on the same substrate. Further, unattached neurons were positioned precisely along the length of the heater filament (operating at 45/spl deg/C) using free convection currents. These preliminary findings indicate that microheated substrates may be used to direct cellular development spatially in a practical manner.     

Applications of infrared microscopy to IC and MEMS packaging

A high sensitivity, infrared (IR) microscope operating in the wavelength range 800 to 2500 nm has been applied to a variety of packaging related issues. Applications can be divided into three categories. 1) For flip chip devices the advantage of the IR microscope is that most silicon is effectively transparent at wavelengths greater than 1100 nm. This enable defects such as voids, delamination cracks and corrosion to be investigated while the chip is mounted on the substrate. 2) The IR microscope enables thermal images of devices to be obtained with a temperature resolution of approximately 1 K and spatial resolution of 2-3 /spl mu/m. 3) The transparency of silicon to IR radiation has proved particularly valuable for characterising micro-electro-mechanical systems (MEMS) devices such as microphones, at various stages of packaging, e.g., after die bonding and wire bonding.     

Phase Relationships and Related Microstructural Observations in the Ca-Si-Al-O-N System

A systematic set of samples with compositions in the Ca alpha-SiAlON (α') system has been fabricated using pressureless sintering to evaluate the phase relationships on, and near, the Ca α' plane. A phase behavioral diagram for the Ca α' plane within the Jänecke prism has been determined and found to be similar to those for the Y and Sm α' systems. However, distinct differences were also observed; two additional regions (α'+ 27R + liquid) and (α'+ 33R + liquid) have been identified. Investigation of the microstructures revealed elongated Ca α' grains in the samples prepared by pressureless sintering. The aspect ratio of the elongated grains of α' increased as the concentration of stabilizing cation was increased. Single crystalline phase Ca α' samples of comparable density to hot-pressed material were fabricated successfully using pressureless sintering.     

Comparison of methotrexate 30 mg per week with placebo in chronic steroid-dependent asthma: a 12-week double-blind, cross-over study

Methotrexate has been shown to have a steroid-sparing effect in chronic steroid-dependent asthmatics at a dose of 15 mg week-1. The aim of this study was to investigate the steroid-sparing activity and adverse events profile of methotrexate 30 mg week-1 in severe steroid-dependent asthma. Eighteen patients who had required 10-50 mg week-1 prednisolone for at least 6 months were asked to participate in a randomized, double-blind, placebo-controlled cross-over study lasting 24 weeks. Daily diary cards of symptoms, peak expiratory flow rate and medication requirements were kept and the patients attended for a chest X-ray, spirometry, lung volumes and gas transfer at commencement and after each 12-week treatment period. Every 3 weeks, adverse events were noted and blood taken for full blood count, urea and electrolytes and liver function tests. Twelve patients completed the trial. Withdrawals were due to non-compliance in two patients, pneumonia in two patients, depression in one patient (on placebo) and severe nausea in one patient. Adverse events were common, probably as a consequence of the higher dosage. Prednisolone requirements were not significantly reduced on methotrexate. Lung function improved on methotrexate with a significant rise in maximal mid-expiratory flow rate and a trend towards improvement in FEV1.