Search Results - (Author, Cooperation:B. A. Miller)

2018-11-01

American Association for the Advancement of Science (AAAS)

2375-2548

Natural Sciences in General

2012-04-12

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Antimalarials/*pharmacology/therapeutic use ; Artemisinins/*pharmacology/therapeutic use ; Cambodia ; DNA Copy Number Variations ; Drug Resistance/*genetics ; Gene Frequency ; Genetic Association Studies ; *Genome, Protozoan ; Haplotypes ; Humans ; Laos ; Malaria, Falciparum/drug therapy/*parasitology ; Microsatellite Repeats ; Plasmodium falciparum/*drug effects/*genetics ; Polymorphism, Single Nucleotide ; Protozoan Proteins/genetics ; *Selection, Genetic ; Thailand

1089-7550

AIP Digital Archive

Physics

We report on the performance of GaAs/AlGaAs quantum-well infrared detectors exhibiting intersubband absorption in the 8–14 μm band. The dark current characteristics have been investigated as a function of barrier width and electron density in the well and compared with a model which takes into account thermionic emission and thermally assisted tunneling in the Wentzel–Kramers–Brillouin approximation. The model gives a good description of the data and is extended to predict the variation of detectivity and background limited operating temperature with structural parameters.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

In this letter, photoluminescence results obtained from two different undoped multilayered pseudomorphic structures grown by molecular beam epitaxy are compared. Intense and spectrally narrow emission was observed from both GaAs/InxGa1−xAs/GaAs and AlxGa1−xAs/InxGa1−xAs/GaAs structures. Excitonic emission from the quantum wells was confirmed by measurements of photoluminescence excitation spectra. The intensity and temperature dependences of the photoluminescence also revealed emission arising from bound excitons and impurities in the quantum wells. Intrinsic and extrinsic emission from confined levels was confirmed by the recorded photoluminescence excitation spectra along with intensity and temperature dependences. In the asymmetric AlxGa1−xAs/InxGa1−xAs/GaAs structure large changes were observed in the photoluminescence intensity under continuous optical excitation which are caused by the optical excitation of defects in the ternary AlxGa1−xAs on top of the pseudomorphically grown InxGa1−xAs.

Electronic Resource

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Amyloid β-peptide (Aβ) is the main component of senile plaques which characterize Alzheimer's disease and may induce neuronal death through mechanisms which include oxidative stress. To date, the signalling pathways linking oxidant stress, a component of several neurodegenerative diseases, to cell death in the CNS are poorly understood. Melastatin-like transient receptor potential 2 (TRPM2) is a Ca2+-permeant non-selective cation channel, which responds to increases in oxidative stress levels in the cell and is activated by oxidants such as hydrogen peroxide. We demonstrate here that Aβ and hydrogen peroxide both induce death in cultured rat striatal cells which express TRPM2 endogenously. Transfection with a splice variant that acts as a dominant negative blocker of TRPM2 function (TRPM2-S) inhibited both hydrogen peroxide- and Aβ-induced increases in intracellular-free Ca2+ and cell death. Functional inhibition of TRPM2 activation by the poly(ADP-ribose)polymerase inhibitor SB-750139, a modulator of intracellular pathways activating TRPM2, attenuated hydrogen peroxide- and Aβ-induced cell death. Furthermore, a small interfering RNA which targets TRPM2, reduced TRPM2 mRNA levels and the toxicity induced by hydrogen peroxide and Aβ. These data demonstrate that activation of TRPM2, functionally expressed in primary cultures of rat striatum, contributes to Aβ- and oxidative stress-induced striatal cell death.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Variable temperature Hall and low-temperature photoluminescence measurements have been used to monitor changes in the transport properties of electrons in modulation doped GaAs/InGaAs/AlGaAs structures that result from growth interruptions and varying temperature growth profiles during deposition by molecular beam epitaxy. Growth interruptions at the InGaAs/AlGaAs interface can lead to higher two-dimensional electron gas mobilities since the AlGaAs near the heterojunction interface can be grown nearer its optimum growth temperature. Changes in carrier mobilities as a result of growth variations are correlated with differences in the energy dependence of the photoluminescence spectrum.

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] The oscillations that we observe are resonant acoustic waves, called p modes. The eigenfunction of a mode varies in the horizontal approximately as a spherical harmonic Y"' of degree / and azimuthal order ra, and is characterized also by a principal quantum number n, called the order, which is ...

Electronic Resource

1432-1009

Soil lose ; Universal soil loss equation ; Nonpoint pollution ; Water quality ; Soil conservation ; Erosion

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Abstract A series of computer programs designed to predict gross annual soil loss on a watershed basis by application of the Universal Soil Loss Equation (USLE) have been developed. The programs provide an easy-to-use, flexible, and standardized means of organizing base data and applying the USLE to large land areas. The programs can be used to assess and to evaluate the effects of changing land-use patterns and conservation practices on soil losses. Critical or problem areas can be readily identified. The USLE Computer Programs are a useful research tool for investigators involved in water quality management, 208 planning, or conservation research. The package of computer programs consists of three main components: data input, the Main Program, and the Totals Program. Input data include both field base data describing the watershed and corresponding values for the factors in the USLE. The Main Program calculates the average rate of soil loss (tons/ acre/yr) and the total soil loss (tons/yr) for the smallest subunit of the watershed identified as the soil unit. Also calculated is an RKLS factor, which is an indication of the erosive potential of a given soil type, slope, and slope length, under a particular rainfall regime. The Totals Program aggregates soil unit losses into progressively larger units, that is, field, farm, subwatershed, and watershed units. An example of the programs' versatility and use is presented.

Electronic Resource

1432-1017

Key words Mechanosensitivity ; Stretch sensitivity ; Curvature sensitivity ; Potassium channels ; Locust muscle

Springer Online Journal Archives 1860-2000

Biology

Physics

Abstract Patch clamp recordings have been made from adult locust (Schistocerca gregaria) muscle membrane to study the mechanosensitivity of potassium channels (BK and IK) in cell-attached patches by transiently applying measured pressures to the contents of the patch pipettes. The aim of the investigations was to demonstrate a novel gating behaviour by pressure of the BK channel in contrast to the familiar behaviour of the IK channel. The open probability (p 0) of the IK channel increased rapidly in response to a pressure step and monotonically during a pressure ramp. This gating was readily repeatable and rapidly reversible. The relationship between ln[p 0/(1–p 0)] and transmembrane pressure was linear. In comparison, p 0 for the BK channel was also increased by pressure, but its gating was delayed, cumulative, and hysteretic.

Electronic Resource

1432-2013

Key words Patch clamp ; Locust muscle ; Potassium channel ; Ca2+ activation ; Quaternary ammonium ions

Springer Online Journal Archives 1860-2000

Medicine

Abstract Two types of K+ channels have been identified in patches of plasma membrane of metathoracic extensor tibiae muscle fibres of adult locust, Schistocerca gregaria. One channel had a maximum conductance of 170 pS, fast open-closed kinetics, and a linear current/ voltage relationship. In inside-out patches it was activated by ‘‘internally applied’’ Ca2+, but at unexpectedly low levels (between 10−10 and 10−9M). The other channel had a maximum conductance of 35 pS, slower open-closed kinetics, and was not activated by Ca2+. In cell-attached patches, its channel conductance measured in symmetrical salines was about three times greater for hyperpolarisations than for depolarisations. This inward rectification was proved to be due to block by intracellular Mg2+. For both channels, open probability (P o) and mean open time increased during depolarisations and decreased during hyperpolarisations, resulting in outward rectifications in terms of net current (I n , product of the single-channel current and P o). For both channels, the K+ conductance was 10 times greater than that for Na+. Internally applied tetraethylammonium or tetramethylammonium ions blocked both channels.

Electronic Resource