Search Results - (Author, Cooperation:L. Pan)

2018-06-28

Royal Society

2054-5703

Natural Sciences in General

environmental chemistry

2018-02-16

The American Association for Cancer Research (AACR)

1078-0432

1557-3265

Medicine

2018-08-03

Institute of Physics (IOP)

1757-8981

1757-899X

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

2011-02-12

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Amino Acid Motifs ; Amino Acid Sequence ; Animals ; Crystallography, X-Ray ; Humans ; Mice ; Models, Molecular ; Molecular Sequence Data ; Mutation, Missense ; Myosins/*chemistry/metabolism ; Nerve Tissue Proteins/*chemistry/metabolism ; Protein Binding ; Protein Conformation ; Protein Structure, Tertiary ; Recombinant Fusion Proteins/chemistry/metabolism

2014-08-15

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; *Binding, Competitive ; *Cell Differentiation ; Cell Proliferation ; DNA Helicases/metabolism ; Drosophila Proteins/metabolism ; Drosophila melanogaster/*cytology/*metabolism ; Female ; Intracellular Signaling Peptides and Proteins/metabolism ; Male ; Multiprotein Complexes/*chemistry/*metabolism ; Ovary/cytology ; Peptide Hydrolases/*chemistry/*metabolism ; Protein Binding ; Stem Cells/*cytology/*metabolism ; Ubiquitins/metabolism

2015-03-25

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Female ; Forkhead Transcription Factors/deficiency/metabolism ; Hemiptera/*anatomy & histology/enzymology/genetics/*metabolism ; Insulin/metabolism ; Male ; Molecular Sequence Data ; Phosphatidylinositol 3-Kinases/metabolism ; Proto-Oncogene Proteins c-akt/metabolism ; Receptor, Insulin/deficiency/*metabolism ; Signal Transduction ; Wings, Animal/anatomy & histology/enzymology/*growth & development/*metabolism

2012-03-30

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Binding Sites ; Cell Membrane/metabolism ; Crystallography, X-Ray ; Cytosol/metabolism ; Diphosphonates/chemistry/metabolism ; Fabaceae/*enzymology ; Hydrolysis ; Inorganic Pyrophosphatase/*chemistry/*metabolism ; Magnesium/metabolism ; Membrane Proteins/*chemistry/metabolism ; Models, Molecular ; Protein Structure, Tertiary ; Protein Subunits/chemistry/metabolism ; Protons ; Static Electricity ; Vacuoles/metabolism

1573-0530

81E10

Springer Online Journal Archives 1860-2000

Mathematics

Physics

Abstract In this Letter, the authors prove some nonexistence theorems for regular static Yang-Mills fields outside the black hole of the Schwarzschild spacetime under certain boundary conditions.

Electronic Resource

2018-11-16

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

Chemistry, Immunology

2018-12-04

Cold Spring Harbor Laboratory Press

0890-9369

Biology

1089-7550

AIP Digital Archive

Physics

The combined electron and hole mobility of a single-crystal type IIa natural diamond and a polycrystalline diamond film deposited by chemical vapor deposition (CVD) were measured using transient photoconductivity as a function of excitation density (1013–1017 cm−3) and temperature (120–410 K). In natural diamond the temperature dependence suggests that the mobility is limited by phonon scattering at low free carrier densities, and by electron-hole scattering at high densities. The combined electron and hole phonon-limited mobility at room temperature is 3000 (±500) cm2/V s. In the CVD film, the mobility at room temperature was estimated to be 50 cm2/V s at low excitation densities. The temperature dependence of the mobility-lifetime product at low excitation densities is different from that of natural diamond, and suggests that charged center scattering, rather than acoustic phonon scattering, is the dominant effect. High densities of nitrogen and dislocations are known to be present in the natural diamond, and these appear to be the dominant recombination sites which limit the carrier lifetime. In the polycrystalline film a variety of structural defects and impurities are believed to exist, but it is unknown which of these dominates the transport and recombination properties.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Photoconductive devices have been fabricated from type IIa diamonds. The sensitivity of these devices is independent of photon energy from 200 to 2200 eV. The dynamic range is 105. The large band gap of the diamond greatly reduces the sensitivity to photons with an energy less than 5.5 eV which is an attractive feature for many applications. The carrier lifetime in the material is 90 ps and the mobility is 1650 cm2/V/s at 106 V/m.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Electrical characteristics associated with radiation detection were measured on single-crystal natural type-IIa diamond using two techniques: charged particle-induced conductivity and time-resolved transient photoinduced conductivity. The two techniques complement each other: The charged particle-induced conductivity technique measures the product of the carrier mobility μ and lifetime τ throughout the bulk of the material while the transient photoconductivity technique measures the carrier mobility and lifetime independently at the first few micrometers of the material surface. For each technique, the μτ product was determined by integration of the respective signals. The collection distance that a free carrier drifts in an electric field was extracted by each technique. As a result, a direct comparison of bulk and surface electrical properties was performed. The data from these two techniques are in agreement, indicating no difference in the electrical properties between the bulk and the surface of the material. The collection distance continues to increase with field up to 25 kV/cm without saturation. Using the transient photoconductivity technique the carrier mobility was measured separately and compared with a simple electron-phonon scattering model. The general characteristics of carrier mobility, lifetime, and collection distance at low electric field appear to be adequately described by the model.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

Photoconductive detectors (PCDs) fabricated from natural IIa diamonds have been used to measure the x-ray power emitted from laser-produced plasmas. The detector was operated without any absorbing filters which distort the x-ray power measurement. The 5.5 eV band gap of the detector material practically eliminates its sensitivity to scattered laser radiation thus permitting filterless operation. Excellent agreement was achieved between a diamond PCD and a multichannel photoemissive diode array in the measurement of radiated x-ray power and energy.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Single-crystal natural diamonds have been intrinsically photoexcited using 2 ps laser pulses. Electron and hole mobilities and decay times are examined as a function of induced carrier density. Two major density dependent effects are observed. First, at high induced carrier densities, a dramatic decrease in the carrier mobility is observed. This is attributed to carrier-carrier scattering between the electrons and the holes. A model describing carrier-carrier scattering in silicon and germanium has been scaled to diamond. Second, the decay time of the electrons decreases as the initially photoexcited density increases. A simple one-level recombination model successfully explains this density dependence. The combination of these two effects results in a minimum in the measured photoconductive decay times.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Spatially resolved electron field emission measurements from a nanocrystalline diamond film grown by plasma-enhanced chemical transport deposition have been obtained using a scanning probe apparatus with micrometer resolution. Macroscopic regions with a high emission site density, and turn-on fields below 3 V/μm, comprised approximately 1/2 of the total sample area. The emitting and the nonemitting regions of the specimen are differentiated distinctly by Raman spectra and subtly by morphologies. Both areas are largely sp3-bonded, but only the nonemitting regions exhibit a sharp line at 1332 cm−1, a well-known signature of diamond in larger crystallites. © 1996 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

A treatment that lowers the threshold field for field emission and increases the emission site density from a nominally n-type diamondlike carbon film is described. The film was deposited using an rf plasma of methane and nitrogen gases. The treatment involved deposition of cesium followed by a low temperature anneal. Field emission measurements were used to characterize the threshold field and emission site density before and after cesium treatment. Ultraviolet photoemission was used to study the effect of cesium on the work function. Dramatic improvements to field emission by cesiation cannot be generalized to all diamondlike samples, as similar treatment of a type IIb single-crystal (p-type) diamond did not produce as pronounced an improvement in turn-on field or emission site density. © 1997 American Institute of Physics.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

This paper reviews the results obtained in this laboratory in experimental studies of volume H− ion sources. Two techniques are discussed, emission spectroscopy and vacuum ultraviolet laser absorption spectroscopy. Time-resolved detection of Balmer-alpha emission has been used to study the excited-state hydrogen atom population. Vacuum ultraviolet laser absorption spectroscopy has been used to measure the ground electronic state atomic and molecular hydrogen populations. The Balmer-alpha emission exhibits a modulation in the intensity at a frequency of twice the exciting rf radiation. On the other hand, the laser absorption measurements show that the density of ground-state hydrogen atoms does not vary significantly with the phase of the exciting rf. Measurements of the vibrational population summed over all rotational states give a vibrational temperature of 6200 K. However, there is no evidence of the "plateau'' predicted in the distribution for v≥5.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The electrical characteristics of chemically vapor deposited (CVD) diamond films were measured as a function of film thickness. The samples studied were polycrystalline with the average grain size increasing from approximately 1 μm on the substrate side to approximately 30 μm on the growth surface for the thickest sample. Using time-resolved transient photoconductivity and charged-particle induced conductivity, the collection distance (d) that a free carrier drifts under the influence of an applied electric field was measured. Our data indicate that there is a gradient in the collection distance through the material. This gradient in electrical properties has implications for electronic uses of CVD diamond.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Normal-incident infrared absorption in the 8–12-μm-atmospheric spectral window in the InGaAs/GaAs quantum-dot superlattice is observed. Using cross-sectional transmission electron microscopy, we find that the InGaAs quantum dots are perfectly vertically aligned in the growth direction (100). Under the normal incident radiation, a distinct absorption peaked at 9.9 μm is observed. This work indicates the potential of this quantum-dot superlattice structure for use as normal-incident infrared imaging focal arrays application without fabricating grating structures. © 1998 American Institute of Physics.

Electronic Resource