Regulation of a Physiological Parameter or In Vivo Drug Concentration by Integral Pulse Frequency Modulated Bolus Drug Injections

This paper describes the designs for two novel, nonlinear, discrete, drug injection controllers. The basis for these controllers is integral pulse frequency modulation (IPFM). An IPFM controller injects small boluses of a drug into a pharmacokinetic (PK) plant to achieve regulation of the plant output. Bolus injections are advantageous because they provide a precise knowledge of the times and the cumulative amount of drug injected, and they require a discrete-action pump suitable for digital control, miniaturization, and implantation.     

Orally active, hydrolytically stable, semisynthetic, antimalarial trioxanes in the artemisinin family

In only three chemical operations, natural trioxane lactone artemisinin (1) was converted into a series of C-10 carbon-substituted 10-deoxoartemisinin compounds 4-9. The three steps involved lactone reduction, replacement of the anomeric lactol OH by F using diethylaminosulfur trifluoride, and finally boron trifluoride-promoted substitution of F by aryl, heteroaryl, and acetylide nucleophiles. All of these C-10 nonacetal, chemically robust, enantiomerically pure compounds 4-9 have high antimalarial potencies in vitro against Plasmodium falciparum malaria parasites, and furans 5a and 5b and pyrrole 7a are antimalarially potent also in vivo even when administered to rodents orally.     

Confirmation of large lattice relaxation of theDX center by extended photo-ionization cross-section measurements

Although the large lattice relaxation model (LLR) for electron capture at the donor relatedDX center in Al_xGa_1-xAs has seen wide acceptance over the last 12 years, there have been some recent proposals which have attempted to explain the experimental data with models that only require small lattice relaxation (SLR). One key piece of evidence supporting LLR is the large observed difference (in the case of Si-doped Al_xGa_1-xAs) between the optical (∼1.4 eV) and thermal (∼0.2 eV) ionization energies. The SLR model proposed that the lowest energy optical ionization was a very weak process, and that the optical transition which had been observed previously is a transition to a higher band. These arguments were supported by photoconductivity data showing a finite photo-ionization rate at energies as low as 200 meV. To resolve this question we have measured the photo-ionization cross section over 7 to 8 orders of magnitude using a tunable infrared laser as a source. A consistent optical ionization energy of about 1.4 eV was observed for 4 samples of differing alloy compositions and doping levels.In no case was there any detectable photo- ionization below 0.8 eV. A detailed discussion of these experiments examines the difficulty in obtaining such a large dynamic range optical spectrum. Of particular relevance are the issues of ionization detection, and the brightness of purity of the optical source. A thorough review of these issues and their impact on previous studies of theDX center is presented.     

Noninvasive optical polarimetric glucose sensing using a true phasemeasurement technique

The focus of this paper was to describe the development and testing of a noninvasive true phase optical polarimetry sensing system to monitor in vivo glucose concentrations. To demonstrate the applicability of this optical sensor for glucose measurement, we first calibrated the system and then tested it in vitro using both a glass test cell filled with glucose solution in the physiologic range, with a path length of 0.9 cm to approximate one centimeter path length present in the anterior chamber of the eye, and then on an excised human eye. Our technique used helium neon laser light which was coupled through a rotating linear polarizer along with two stationary linear polarizers and two detectors to produce reference and signal outputs whose amplitudes varied sinusoidally with a frequency of twice the angular velocity of the rotating polarizer, and whose phase was proportional to the rotation of the linear polarization vector passing through the glucose solution.     

Subtle transchondral fractures of the talar dome: a radiological perspective

Radiographic findings associated with small talar dome fractures were analyzed in 21 patients. Representative cases are presented. The classification of talar dome fractures, and the role of the radiologist in their evaluation, are discussed.     

Metal-germanium Schottky barriers

A systematic study has been made of the electrical characteristics of Schottky barriers fabricated by evaporating various metal films on n-type chemically cleaned germanium substrates. The diodes, with the exception of Al---Ge contacts, exhibit near-ideal electrical characteristics and age only slightly towards lower barrier height values. Al---Ge contacts exhibit very pronounced ageing towards higher barrier height values, due to formation of an extra aluminium oxide interfacial layer. Because of this, the barrier height values of aged Al---Ge contacts derived from I-V and C-V characteristics differ significantly. The dependence of the barrier height, (φ_b) on the metal work function, φ_m, for different metal-germanium contacts shows that surface states play an important role in the formation of the barrier. The density of germanium surface states is estimated to be D_s = 2 × 10¹³ eV⁻¹ cm⁻².     

Women in technical/scientific professions: results of two nationalsurveys

A survey to study women in technical and scientific fields was conducted in 1993. The study examined the environment in which women work, the relationship between women's personal lives and their work, and women's interpersonal communication styles. Results of the study supported some of the previous research findings related to glass ceilings and career paths. However, results related to sexual harassment and benefits prompted new questions, and results related to communication styles conflicted with the findings of much previous research. To further investigate these conflicting results, a follow-up survey was conducted in 1993. Results of this survey supported the 1993 findings. Results appear to indicate that the workplace and the women in it are changing. The workplace is becoming more family-oriented, and women are practicing strategies for working effectively in traditionally male-dominated organizations. In technical/scientific fields, men and women have adopted androgynous language patterns, and little difference exists between the interpersonal communication styles of men and women