Suicide substrate reaction-diffusion equations: varying the source

The suicide substrate reaction is a model for certain enzyme-inhibiting drugs. This reaction system is examined assuming that the substrate diffuses freely while the enzyme remains fixed. Two sets of initial and boundary conditions are examined: one modelling an instantaneous point source, akin to an injection of substrate, the other, a continuous point source, akin to a continuing influx, or intravenous drip, of substrate. The quasi-steady-state assumption is applied to obtain analytical solutions for a limited parameter space. Finally, further applications of numerical and analytical experimentation on pharmaceutical mechanisms are described

On the kinetics of suicide substrates

We consider a realistic suicide substrate reaction which can be represented by four rate equations for the concentrations of the various molecules as functions of time. We present a general procedure to obtain accurate, approximate solutions analytically in terms of the rate equation parameters. This systematic technique provides more accurate approximations to the exact (numerical) solutions than other approximate methods which have been proposed based on a pseudo-steady state hypothesis

Recent developments in CID imaging

Readout of CID imaging arrays was first performed by injecting and detecting the signal charge from each sensing site in sequence. A new readout method, termed parallel injection, has been developed in which the functions of signal charge detection and injection have been separated. The level of signal charge at each sensing site is detected during a line scan, and during the line retrace interval, all charge in the selected line is injected. The parallel injection technique is well adapted to TV scan formats in that the signal is read out at high speed, line by line. A 244 line by 248 element TV compatible imager, employing this technique and including an on chip preamplifier, has been constructed and operation demonstrated

Multi-modal information processing for visual workload relief

The simultaneous performance of two single-dimensional compensatory tracking tasks, one with the left hand and one with the right hand, is discussed. The tracking performed with the left hand was considered the primary task and was performed with a visual display or a quickened kinesthetic-tactual (KT) display. The right-handed tracking was considered the secondary task and was carried out only with a visual display. Although the two primary task displays had afforded equivalent performance in a critical tracking task performed alone, in the dual-task situation the quickened KT primary display resulted in superior secondary visual task performance. Comparisons of various combinations of primary and secondary visual displays in integrated or separated formats indicate that the superiority of the quickened KT display is not simply due to the elimination of visual scanning. Additional testing indicated that quickening per se also is not the immediate cause of the observed KT superiority

Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li-O2_2 battery capacity

Among the 'beyond Li-ion' battery chemistries, nonaqueous Li-O$_2$ batteries have the highest theoretical specific energy and as a result have attracted significant research attention over the past decade. A critical scientific challenge facing nonaqueous Li-O$_2$ batteries is the electronically insulating nature of the primary discharge product, lithium peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance solubility to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochemical stability of the system, thereby deleteriously affecting battery rechargeability. In this study, we report that a significant enhancement (greater than four-fold) in Li-O$_2$ cell capacity is possible by appropriately selecting the salt anion in the electrolyte solution. Using $^7$Li nuclear magnetic resonance and modeling, we confirm that this improvement is a result of enhanced Li$^+$ stability in solution, which in turn induces solubility of the intermediate to Li$_2$O$_2$ formation. Using this strategy, the challenging task of identifying an electrolyte solvent that possesses the anti-correlated properties of high intermediate solubility and solvent stability is alleviated, potentially providing a pathway to develop an electrolyte that affords both high capacity and rechargeability. We believe the model and strategy presented here will be generally useful to enhance Coulombic efficiency in many electrochemical systems (e.g. Li-S batteries) where improving intermediate stability in solution could induce desired mechanisms of product formation.Comment: 22 pages, 5 figures and Supporting Informatio

Average and worst-case specifications of precipitating auroral electron environment

The precipitation electrons in the auroral environment are highly variable in their energy and intensity in both space and time. As such they are a source of potential hazard to the operation of the Space Shuttle and other large spacecraft operating in polar orbit. In order to assess these hazards both the average and extreme states of the precipitating electrons must be determined. Work aimed at such a specification is presented. First results of a global study of the average characteristics are presented. In this study the high latitude region was divided into spatial elements in magnetic local time and corrected geomagnetic latitude. The average electron spectrum was then determined in each spatial element for seven different levels of activity as measured by K sub p using an extremely large data set of auroral observations. Second a case study of an extreme auroral electron environment is presented, in which the electrons are accelerated through field aligned potential as high as 30,000 volts and in which the spacecraft is seen to charge negatively to a potential approaching .5 kilovolts

R-matrix Floquet theory for laser-assisted electron-atom scattering

A new version of the R-matrix Floquet theory for laser-assisted electron-atom scattering is presented. The theory is non-perturbative and applicable to a non-relativistic many-electron atom or ion in a homogeneous linearly polarized field. It is based on the use of channel functions built from field-dressed target states, which greatly simplifies the general formalism.Comment: 18 pages, LaTeX2e, submitted to J.Phys.

Making the Case for Exploratory World Language Instruction in Catholic Elementary Schools through University Partnerships

As a result of a university partnership, elementary students at two midwest Catholic elementary schools have been provided with exploratory world language instruction (FLEX) from pre-service teachers. To investigate students’ attitudes and learning of Spanish, researchers interviewed second and fourth graders. The students’ parents and pre-service teachers answered open-ended questionnaires. The research questions for this qualitative study were: 1) How does exploratory world language instruction (FLEX) affect children’s attitudes about learning world languages and cultures? 2) How does exploratory world language instruction (FLEX) affect children’s learning of a world language? The results showed that students possessed positive attitudes about world language instruction, and they learned numbers, colors, cultural information, and food and animal vocabulary, as well as how to communicate at the novice level. Universities should consider engaging in service-learning partnerships with Catholic elementary schools so students learn to open their minds and hearts to diverse languages and cultures. Como resultado de una colaboración con una universidad, se les ofreció a estudiantes de dos escuelas elementales católicas del medio oeste la enseñanza exploratoria de lenguas extranjeras (FLEX) por parte de docentes en prácticas. Para investigar las actitudes de los estudiantes y su aprendizaje de español, los investigadores entrevistaron a estudiantes de segundo y cuarto curso. Los padres de los estudiantes y los docentes en prácticas contestaron cuestionarios abiertos. Las preguntas de investigación para este estudio cualitativo fueron: (a) ¿Cómo afecta la enseñanza exploratoria de lenguas extranjeras (FLEX) a las actitudes de los niños frente al aprendizaje de lenguas y culturas del mundo? (b) ¿Cómo afecta la enseñanza exploratoria de lenguas extranjeras (FLEX) al aprendizaje por parte de los niños de una lengua del mundo? Los resultados mostraron que los estudiantes disponían de una actitud positiva sobre la enseñanza de lenguas del mundo, y aprendieron números, colores, información cultural, vocabulario de comida y animales, así como a comunicarse a un nivel básico. Las universidades deberían considerar participar en colaboraciones de aprendizaje-servicio con escuelas elementales católicas para que los estudiantes puedan abrir sus mentes y corazones a las diversas lenguas y culturas. Palabras clave: escuelas elementales, FLEX, aprendizaje-servicio, aprendizaje a través del servicio, lenguas del mund