A Systematic Approach for Multidimensional, Closed-Form Analytic Modeling: Minority Electron Mobilities in Ga1-xAlxAs Heterostructures.

A significant, practical challenge, which arises in developing computationally efficient physical models for use in computer simulations of microelectronic and optoelectronic devices (for example, transistors in digital cellular phones and lasers in optical networks, respectively), is to represent vast amounts of numerical data for transport properties in two or more dimensions in terms of closed form analytic expressions. In this paper, we present a general methodology to achieve the above goal for a class of numerical data in a bounded two-dimensional space. We then apply this methodology to obtain a closed-form analytic expression for the minority electron mobilities at 300 K in p-type Ga1- x Al x As as functions of the acceptor density N A between 10(16) cm(-3) and 10(20) cm(-3) and the mole fraction of AlAs x between 0.0 and 0.3. This methodology and its associated principles, strategies, regression analyses, and graphics are expected to be applicable to other problems beyond the specific case of minority mobilities addressed in this paper.

Technology Roadmaps for Compound Semiconductors.

The roles cited for compound semiconductors in public versions of existing technology roadmaps from the National Electronics Manufacturing Initiative, Inc., Optoelectronics Industry Development Association, Microelectronics Advanced Research Initiative on Optoelectronic Interconnects, and Optoelectronics Industry and Technology Development Association (OITDA) are discussed and compared within the context of trends in the Si CMOS industry. In particular, the extent to which these technology roadmaps treat compound semiconductors at the materials processing and device levels will be presented for specific applications. For example, OITDA's Optical Communications Technology Roadmap directly connects the information demand of delivering 100 Mbit/s to the home to the requirement of producing 200 GHz heterojunction bipolar transistors with 30 nm bases and InP high electron mobility transistors with 100 nm gates. Some general actions for progress towards the proposed International Technology Roadmap for Compound Semiconductors (ITRCS) and methods for determining the value of an ITRCS will be suggested. But, in the final analysis, the value added by an ITRCS will depend on how industry leaders respond. The technical challenges and economic opportunities of delivering high quality digital video to consumers provide concrete examples of where the above actions and methods could be applied.

A new case of monosomy for 17q25----qter due to a maternal translocation [t(3;17)(p12;q24)].

An 18-month-old girl was found to have monosomy for 17q25----qter which resulted from an unequal crossing-over in the mother carrying an apparently balanced translocation 46, XX, t(3;17) (p12;q24). Clinical features of the proband included: cleft palate, micrognathia and glossoptosis. It seems to be the first reported case where a single band deletion in the long arm of chromosome 17 has ever been noted.

Seizures in adolescence. A review of patients admitted in an adolescent service.

The admissions of new seizure patients to an adolescent service over a 10-year period were retrospectively reviewed with regard to the patient's etiology, work-up, and outcome. Head trauma and pseudoseizures were common, 21% and 19%, respectively. In general, the outcome in adolescents appears to depend more on the underlying diagnosis than on how the seizure presents.

Reduction of polypharmacy for epilepsy in an institution for the retarded.

It is a well-established fact that 20 to 40 per cent of patients in residential institutions for the retarded have seizures and take anticonvulsants. Most patients have quiescent seizure disorders and can manage well on monotherapy. In this study, 78 per cent of the patients remained seizure-free after switching from multiple-drug regimens to monotherapy.

The functional, comparative and evolutionary anatomy of myosins.

Actins and myosins are generally present in all animal, plant and fungal cells, and in some, if not all, prokaryotes as well. It is proposed that, in general, myosins can carry specific loads as they move along actin filaments, thus mediating a form of active transport. Myosins exert their mechanical forces by a lever action (moklokinesis) of a part of the molecule: the S-1 "head" in the case of muscle myosins. Various portions of myosin molecules can be assigned specialized functions. Each such part can be designated by an appropriate functional name. Examples are: the enzyme portion (zymomere), the motor portion (dynamere), the lever portion (moklomere), a connecting portion (desmomere), a coupling or binding portion (haptomere), and one or more flexible portions (kamptomeres). These parts can be recognized in highly evolved and specialized muscle myosins and can be postulated in simpler, single headed myosins. A primitive myosin, represented principally by a moklomere equipped with a zymomere and a dynamere, is envisioned as an evolutionary ancestor of all myosins. This primitive myosin resembles the S-1 head of muscle myosin. I suggest that from such a primitive myosin, more elaborate single-headed myosins have evolved, equipped with specific haptomeres coupled to the moklomere by desmomeres and kamptomeres. From such general single-headed myosins have arisen the highly specialized two-headed myosins represented in muscle. It is suggested that the two-headed feature is favored in myosins capable of forming bipolar filaments.

Nonconvulsive epileptiform activity appearing as ataxia.

Ataxia may be the result of otherwise silent epileptiform activity. We studied three patients, between 3 and 5 years of age, whose initial complaint was unsteadiness of gait. Each one of the patients had an epileptiform EEG with bursts of slow spike and wave activity. Each had normal results of diagnostic studies for other causes of ataxia. Specifically, none had anticonvulsant drug levels in the toxic range. Modification of the anticonvulsant regimen resulted in dramatic clinical and EEG improvement. Nonconvulsive epileptiform activity has been called pseudoataxia in the scant literature on this subject. This process should be considered in the evaluation of ataxia in children.

Ipecac-induced myopathy simulating dermatomyositis.

We studied a young woman with an eating disorder. To induce vomiting, she took syrup of ipecac daily for 2 years, and then developed insidious, progressive muscle weakness. Skin findings were similar to those of dermatomyositis. Muscle biopsy, however, was similar to experimental emetine myopathy and lacked inflammatory features. Upon cessation of ipecac abuse, strength returned. We believe that this patient had ipecac-induced muscle weakness.

Photoacoustic spectroscopy: a measurement technique for low absorption coefficients.

The case in which a laser beam modulated at angular frequency omega passes through the weakly absorbing windows of a gas cell which contains a nonabsorbing gas is investigated in this paper. In particular, the frequency dependences of the acoustic stresses in the gas which arise from the surface and bulk absorption are derived. An intermediate range of frequencies exists for which the acoustic stress due to surface absorption varies approximately as omega(-1) and has an approximate 90 degrees phase shift relative to the modulated laser beam and for which the acoustic stress due to bulk absorption varies approximately as omega(-3/2) and has an approximate 45 degrees phase shift. Numerical examples for a representative laser glass and air (nitrogen) are given.

Absorbing precipitates in cadmium telluride: estimates for catastrophic laser-damage thresholds.

One problem frequently encountered in high-power laser systems is thermal extrinsic damage to the laser materials, which arises from absorbing inclusions. In this paper the maximum tensile stresses as a function of inclusion size, laser pulse width, and laser power are estimated for the common precipitates in CdTe.

Science and art in preparing tissues embedded in plastic for light microscopy, with special reference to glycol methacrylate, glass knives and simple stains.

Plastic embedding preserves tissue structure much more faithfully than does paraffin. Acrylic polymerization is innocuous to dye-binding groups in sections. The water solubility of glycol methacrylate monomer and the hydrophilic properties of the polymer allow for convenience in dehydration and for versatility in staining sections. Five years of experience with glycol methacrylate (GMA) embedding for light microscopy is summarized. Methods for purifying GMA monomer are cited. Procedures for fixing, dehydrating, embedding, polymerizing, sectioning and staining, using GMA, are explained. A method is provided for making glass knives long enough to cut large blocks. Simple, reliable, quick staining methods are outlined. When compared with paraffin, GMA offers opportunities for simpler, quicker procedures and yields sections of superior quality, greater information content, and less distortion.

Absorption coefficients of weakly absorbing solids: theory of a barothermal gas cell.

For the case in which a laser beam passes through the weakly absorbing windows of a cell containing a non-absorbing gas, the temperature profiles in the cell windows and the pressure and temperature profiles in the gas have been calculated. Both the transient response and steady-state behavior of the cell are examined when the barothermal conditions are valid. These calculations suggest that sufficient heat transfers by thermal conduction from the weakly absorbing windows into the gas to produce a measurable pressure rise in the gas. The theory contains the two assumptions that bulk absorption in the window is the mechanism by which energy is transferred from the laser beam to the windows and that the window and adjacent gas are in good thermal contact. Numerical examples for a laser glass and air (nitrogen) are given.