Search Results - (Author, Cooperation:A. Amir)

2018-06-02

The Society of Nuclear Medicine (SNM)

0022-3123

Medicine

2014-08-12

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

*Brain ; *Brain-Computer Interfaces ; *Computer Simulation ; *Neural Networks (Computer) ; *Neurons ; Software ; Synapses

2015-12-15

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; Bacteria/classification/*metabolism ; Biodegradation, Environmental ; *Cadaver ; Ecosystem ; Fungi/classification/*metabolism ; Mice ; *Microbial Consortia ; Nitrogen Cycle ; Soil/chemistry/classification ; *Soil Microbiology

2018-07-22

MDPI Publishing

1424-8220

Chemistry and Pharmacology

Electrical Engineering, Measurement and Control Technology

2018-11-22

BMJ Publishing Group

Medicine

2018-03-23

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Geosciences

Computer Science

Medicine

Natural Sciences in General

Physics

2018-08-31

MDPI Publishing

1996-1944

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2018-11-15

American Physical Society (APS)

1098-0121

1095-3795

Physics

Superfluidity and superconductivity

1077-3118

AIP Digital Archive

Physics

Electronic properties of a doped zigzag nanotube are investigated by a self-consistent tight-binding method. We propose that a doped nanotube with donor atoms on one side and acceptors on the other can function as a nano diode. It is shown that a potential step in the tube, created by two different types of doping in this case, causes the nonlinear rectifying effect. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We have developed structures with two well-defined negative differential resistance (NDR) regions by sequentially growing two resonant tunneling devices separated by an n+ connecting layer. Devices fabricated from these structures exhibited three stable operating points for multilevel logic circuits and were used in circuits which multiplied the input signal frequency by 3 or 5. This approach can be extended to obtain more than two NDR regions by vertical integration of additional resonant tunneling structures.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Strong electron quantum interference effects have been observed at room temperature in the current-voltage characteristics of a double-barrier, wide-well, lattice-matched In0.52Al0.48As /In0.53Ga0.47As heterostructure tunneling device. A total of 22 oscillations was observed in the differential conductance. A model is proposed which attributes ten of the oscillations to the usual resonant tunneling via the subbands and the rest to the presence of virtual states that exist in the well and second barrier regions.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A device with multiple negative differential resistances was obtained by combining two AlInAs/InGaAs based resonant tunneling diodes in series. Equal peak currents and large current peak-to-valley ratios were demonstrated at room temperature. Three stable operating points were identified for trilevel logic applications and a multiply-by-three circuit was demonstrated.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Double-barrier/single-well resonant tunneling structures based on InAlAs/InGaAs were vertically integrated on an InP substrate to obtain devices with multiple negative-differential resistance (NDR) regions. These devices, with either two or five tunneling structures, exhibited uniform current peaks and valleys and also had NDR regions about equally spaced in bias voltage. The devices were used in simple circuits to demonstrate three or six stable logic levels which could be set with current pulses.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

A film of SiO2 was used to passivate Au:Ge:Ni on GaAs during the alloying cycle used to fabricate ohmic contacts. The passivated metallization produced smooth surfaces and interfaces and consistently resulted in a specific contact resistivity of 3×10−6 Ω cm2 over a wide range of alloying times and temperatures. On the other hand, the unpassivated pads exhibited an increasing contact resistivity with increasing alloying times. The sheet resistivity under the metal contact was also found to increase with alloying time when the metallization was not passivated. During the alloying cycle, severe damage to the substrate takes place at the metal-semiconductor interface if the metallization is not passivated. The passivating film of SiO2 remained intact during the heat treatment and its Auger depth profile revealed that it is impermeable to Au, Ge, Ni, Ga, and As at alloying temperatures up to 500 °C. It is proposed that better reproducibility of the specific contact resistivity and improved surface and interface morphologies are due to the suppression of As loss during the heat treatment.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The electrical characteristics of In0.52Al0.48As/In0.53 Ga 0.47 As resonant tunneling diodes are reported. These devices exhibit current peak-to-valley ratios up to 6.7 at room temperature. Differences in the current-voltage characteristics for devices made from epilayers grown simultaneously on n+ and semi-insulating InP substrates demonstrate the importance of minimizing the parasitic series resistance. The enhanced peak-to-valley ratio has been attributed to thick In0.52Al0.48 As barriers (50 A(ring)) and wide, undoped In0.53Ga0.47 As spacer-layers (400 A(ring)).

Electronic Resource

1600-065X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Summary:  A combination of approaches – gene mapping, biomarker analysis, and studies of signal transduction – has helped to clarify the mechanisms of age-related change in mouse immune status and the implications of immune aging for late-life disease. Mapping studies have documented multiple quantitative trait loci (QTL) that influence the levels of age-sensitive T-cell subsets. Some of these QTL have effects that are demonstrable in young-adult mice (8 months of age) and others demonstrable only in middle-aged mice (18 months). Biomarker studies show that T-cell subset levels measured at 8 or 18 months are significant predictors of lifespan for mice dying of lymphoma, fibrosarcoma, mammary adenocarcinoma, or all causes combined. Mice whose immune systems resemble that of young animals, i.e. with low levels of CD4+ and CD8+ memory T cells and relatively high levels of CD4+ T cells, tend to outlive their siblings with the opposite subset pattern. Biochemical analyses show that T cells from aged mice show defects in the activation process within a few minutes of encountering a stimulus and that the defects precede the recognition by the T-cell receptor of agonist peptides on the antigen-presenting cell. Defective assembly of cytoskeletal fibers and hyperglycosylation of T-cell surface glycoproteins contribute to the immunodeficiency state, and indeed treatment with a sialylglycoprotein endopeptidase can restore full function to CD4+ T cells from aged donors in vitro.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Ab initio total energy calculation and molecular dynamics simulation on the process of dopant insertion into carbon nanotubes are carried out on the basis of the all-electron mixed basis approach within the local density approximation. First, an upper bound for the height of the potential barrier which is seen by typical alkali metals (Na and K) going through the center of a hexagonal ring of the nanotube is estimated to be 40 eV for Na and 90 eV for K. Next, such an insertion process is simulated with a suitable kinetic energy of the dopant (70 eV for Na and 150 eV for K). It is observed that the carbon atoms are pushed to open the hexagonal ring wider and the dopant passes through. After encapsulation, the hexagonal ring restores its initial configuration, while the impact shock propagates along the nanotube and gradually decays. © 1999 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The four possible mechanisms of ring closure in dioxin formation from chlorophenols are studied using ab initio molecular dynamics, within generalized gradient approximation. Free energy barriers, derived as the potential of mean constraint force, directly lead to a static approximation for the transition rates. We show, however, that the static approximation overestimates the actual rates by 33%–345%, depending on the intermediate/temperature. Comparing our results with the available experimental data, we conclude that, contrary to what is widely assumed, the pathways starting from two chlorophenols are not among the most dominant pathways in the formation of highly toxic dioxins, at least in the gas phase. This signifies the role of catalysts and/or other precursors. © 2001 American Institute of Physics.

Electronic Resource

1546-1718

Nature Archives 1869 - 2009

Biology

Medicine

[Auszug] We compare the utility of core biopsy samples with surgical tumor specimens as starting material for microarray analysis. Two human tumor xenografts, Ewing sarcoma and neuroblastoma grown in Beige-Scid mice, served as source materials for this study. Six 16g-needle core biopsies and an excision ...

Electronic Resource

0009-8981

Carnosinase activity ; Neurological disorders

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Medicine

Electronic Resource