A Systematic Approach for Multidimensional,Closed-Form Analytic Modeling: Effective Intrinsic Carrier Concentrations in Ga1?xAlxAs Heterostructures

A critical issue identified in both the technology roadmap from the Optoelectronics Industry Development Association and the roadmaps from the National Electronics Manufacturing Initiative, Inc. is the need for predictive computer simulations of processes, devices, and circuits. The goal of this paper is to respond to this need by representing the extensive amounts of theoretical data for transport properties in the multi-dimensional space of mole fractions of AlAs in Ga_1−xAl_xAs, dopant densities, and carrier densities in terms of closed form analytic expressions. Representing such data in terms of closed-form analytic expressions is a significant challenge that arises in developing computationally efficient simulations of microelectronic and optoelectronic devices. In this paper, we present a methodology to achieve the above goal for a class of numerical data in the bounded two-dimensional space of mole fraction of AlAs and dopant density. We then apply this methodology to obtain closed-form analytic expressions for the effective intrinsic carrier concentrations at 300 K in n-type and p-type Ga_1−xAl_xAs as functions of the mole fraction x of AlAs between 0.0 and 0.3. In these calculations, the donor density N_D for n-type material varies between 10¹⁶ cm⁻³ and 10¹⁹ cm⁻³ and the acceptor density N_A for p-type materials varies between 10¹⁶ cm⁻³ and 10²⁰ cm⁻³. We find that p-type Ga_1−xAl_xAs presents much greater challenges for obtaining acceptable analytic fits whenever acceptor densities are sufficiently near the Mott transition because of increased scatter in the numerical computer results for solutions to the theoretical equations. The Mott transition region in p-type Ga_1−xAl_xAs is of technological significance for mobile wireless communications systems. This methodology and its associated principles, strategies, regression analyses, and graphics are expected to be applicable to other problems beyond the specific case of effective intrinsic carrier concentrations such as interpreting scanning capacitance microscopy data to obtain two-dimensional doping profiles.     

The Scope and Impact of Perinatal Loss: Current Status and Future Directions.

The loss of an expected child can be devastating and traumatizing for parents, placing them at risk for postloss mental health complications, such as complicated or traumatic grief. The authors review the psychological and social impacts of perinatal loss and describe the standard care provided in the hospital. The authors review studies that examine the efficacy of standard care and highlight the need for empirical evidence confirming the efficacy of these current interventions. The authors provide recommendations for health care professionals in contact with the perinatally bereaved and suggest areas for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of p38 MAP kinase in myocardial stress

The current study focuses on the role of p38 MAP kinase in response to acute preconditioning stimuli and ischemia. Exposure of the rat myoblast cell line H9C2 to preconditioning stimuli, viz. brief duration of ischemia (metabolic inhibition) and adenosine, led to activation of p38 MAP kinase. The protective preconditioning effect of these stimuli against lethal ischemic insult was abolished in the presence or p38 MAP kinase inhibitor SB 203580 but not in the presence of MEK inhibitor PD 98509. Phorbol myristate acetate, PMA, which activates protein kinase C, PKC, activates p38 MAP kinase. and this activation is inhibited by PKC inhibitor G. 6850. The preconditioning effect of PMA was abolished by SB 203580 and also by protein kinase C inhibitor Go 6850. This indicates that the protective action of preconditioning by PKC is mediated via activation of p38 MAP kinase. Paradoxically, the presence of SB 203580 and Go 6850 during the lethal stress protected the cells against cell death. The mode of cell death in this study whether necrotic or apoptotic has not been established. Lethal ischemic stress activates p38 MAP kinase. Preconditioning the cells decreases the activation of p38 MAP kinase in response to the second lethal stress. These findings highlight the role of p38 MAP kinase in ischemic preconditioning v ischemia. Furthermore, our findings in an in vitro model using a proliferating cell line indicate that the duration and/or intensity of stimuli activating p38 kinase probably determines whether it would play a beneficial v deleterious role in cell survival in response to stress.     

Does existing law fail to address nanotechnoscience?

The realm of nanotechnoscience (NTS) is vast and dense. A niche industry of nanocritics has arisen to address ethical principles that should govern the field, causal factors in that development, and the types of nanotechnological futures considered desirable. Although their visions of a nanotechnologized world vary considerably, commentators of many stripes share a concern about what they perceive as the same worrisome issue: a lack of appropriate ethical and legal principles and processes to guide nanotechnological R&D and commercialization.     

Effect of adaptation to high altitude hypoxia on fixation of temporary connections

Parameters of preservation of conditioned defensive reflexes elaborated in one combination and of reflexes elaborated in many combinations in a T-maze varied as a function of time in animals preliminarily adapted to hypoxia and in control ones. Adaptation to altitude hypoxia raised the degree and duration of preservation of temporary connections and did not influence the course of conditioning. The degree of preservation in animals adapted to hypoxia was enhanced both during continued adaptation and in ten to twenty days after its cessation. It is probable that adaptation considerably intensifies the process of fixation of temporary connections. It is suggested that the effect results from activation of the synthesis of nucleic acids and proteins in the brain, due to adaptation to altitude hypoxia.     

Relation of PaCO2 to fresh gas flow in a circle system

Recent reports have described methods of controlling the level of CO2 during anesthesia with a N2O-relaxant sequence and controlled ventilation. This paper describes a method of predicting and controlling the PaCO2, using body weight for determination of the fresh gas flow from the anesthetic machine, removing the absorbent from the canister while leaving the canister in the circuit, and controlling ventilation at 12 ml/kg and at 12/min.     

The TRIUMF Time Projection Chamber Data Acquisition System

The Time Projection Chamber (TPC) at TRIUMF was developed for the search for muon-electron conversion, a lepton number violating process. This paper describes the data acquisition system in use for the last two years. Basic components of the system are a multi-crate CAMAC acquisition system, external memory, PDP 11/40 and VAX 11/780 coupled through DECNET. A discussion of the various software packages for data-taking and on-line track reconstruction follows.