Search Results - (Author, Cooperation:D. Y. Kim)

2014-10-14

Nature Publishing Group (NPG)

0028-0836

1476-4687

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Medicine

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Alzheimer Disease/genetics/*metabolism/*pathology ; Amyloid beta-Peptides/chemistry/genetics/metabolism ; Cell Culture Techniques/*methods ; Cell Differentiation ; Drug Evaluation, Preclinical/methods ; Extracellular Space/metabolism ; Glycogen Synthase Kinase 3/metabolism ; Humans ; Microtubule-Associated Proteins/metabolism ; *Models, Biological ; Neural Stem Cells/*metabolism/pathology ; Neurites/metabolism ; Phosphorylation ; Presenilin-1/metabolism ; Protein Aggregation, Pathological ; Reproducibility of Results ; tau Proteins/chemistry/metabolism

2011-12-23

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

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Affinity Labels ; Animals ; Core Binding Factor beta Subunit/*metabolism ; Cullin Proteins/metabolism ; Cytidine Deaminase/*metabolism ; Gene Knockdown Techniques ; Gene Products, vif/*metabolism ; Genetic Complementation Test ; HEK293 Cells ; HIV Infections/*metabolism/*virology ; HIV-1/*physiology ; Host-Pathogen Interactions ; Humans ; Jurkat Cells ; Macaca mulatta/metabolism/virology ; Mass Spectrometry ; Models, Biological ; Protein Binding ; Proteolysis ; Simian Immunodeficiency Virus/metabolism ; Ubiquitin-Protein Ligases/chemistry/metabolism ; Ubiquitination ; Virus Replication ; vif Gene Products, Human Immunodeficiency Virus/*metabolism

2011-04-30

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

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2018-01-31

The American Society for Microbiology (ASM)

0022-538X

1098-5514

Medicine

2018-02-02

The Society of Nuclear Medicine (SNM)

0022-3123

Medicine

2018-09-07

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

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Medicine, Diseases, Neuroscience, Online Only

1089-7550

AIP Digital Archive

Physics

The native oxide, thermally oxidized and hydrofluoric acid rinsed surfaces of Si(100) have been characterized by photon stimulated ion desorption (PSD), and both photoelectron and Auger electron spectroscopies. The only species detected by PSD were H+ ions with different kinetic energies. Low kinetic energy H+ ions were detected only from the HF rinsed surfaces presumably arising from scission of Si—H bonds while higher kinetic energy ions attributed to adsorbed hydrocarbon dissociation were observed for all of the surfaces.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We have extended the stable amorphous phase of the Co1−xZrx system to 7〈x〈52 by compositionally modulating very thin (five to ten atomic layers) layers of Co and Zr by rf diode sequential sputtering from the elemental targets onto rotating, water cooled substrates. This extension was attributed to a stable, two-phase, hetero-amorphous state similar to that previously reported for Co/B layered structures (Ref. 1). The measured compositional variation of Ms of our Co/Zr layered structures indicated that, as expected, the composition of the stable Co-rich clusters in the heterogeneous state lies near the stable Co-rich eutectic of the CoZr system. The composition variation of the coercivity of the as-deposited Co/Zr structures was remarkably low (〈1 Oe) over the entire composition range. The uniaxial anisotropies of 15–30 Oe were reduced to ≈2 Oe by a combination of bias sputtering and rotating field annealing. Although they have reduced Ms, the permeabilities of the Zr-rich films are (approximately-greater-than)1200, and constant (to 10%) to ≈50 MHz. They also have high resistivities (≈190 μΩ cm), potentially increased hardness and stability, and could be useful for magnetic recording head applications.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

GaAs films grown on untilted Si substrates and prepared by molecular-beam epitaxy were characterized by low-temperature photoluminescence (PL) spectroscopy. The GaAs layer was irradiated in situ with a 50 keV electron beam during growth. The PL spectrum of the electron-beam-irradiated GaAs/Si consisted of four well-resolved peaks at 1.502, 1.488, 1.471, and 1.434 eV. The peaks at 1.502 and 1.488 eV are related to the intrinsic emissions, and the peaks at 1.471 and 1.434 eV originate from the extrinsic emission band. The full width at half-maximum of the 1.488 eV emission band is only 2.8 meV, which is much smaller than the value obtained from the unirradiated GaAs/Si. The strain induced in the GaAs layer was estimated from the intrinsic peaks observed in the temperature range of 5–200 K. The PL properties of the species after postgrowth treatment, such as rapid thermal annealing are discussed.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

An experimental method is described that is directed at monitoring the creation and decay of core hole states in molecules from state-to-state. Data in the form of a coincidence map are presented and analyzed for the case of nitrous oxide.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Tunable and polarized soft x-ray radiation was used to excite core electrons of H2O. Angle-resolved proton yields were measured by retarding potential analyzers at 0° and 90° with respect to the polarization vector of the radiation. The ability of angle-resolved detection to reveal hidden resonances in rich molecular spectra is demonstrated, and the anisotropy parameter obtained from the two ion yields identifies the symmetries and the relative oscillator strengths of the core-hole excited states in the near-edge region of the spectrum. The analysis of the data substantiates the validity of the axial recoil approximation and provides evidence for ultrafast dissociation. Comparisons with the results of theoretical calculations are made.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The symmetry of excited states reached by photoexcitation of K-shell electrons of N2 and O2 is identified from the fragmentation anisotropy. For each molecule, ion yield excitation spectra were obtained at 90°, 54.7°, and 0° relative to the axis of soft x-ray polarization. The degree of polarization of the synchrotron radiation was determined experimentally. From this determination and the angular dependence of the ion yield, the photoabsorption anisotropy parameter β is obtained as a function of photon energy. Variations in the β spectra are discussed in terms of previously assigned spectral features and are compared with other experimental results. A comparison also is made with theoretical calculations, which are available for the case of N2.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We present the optimized planar Hall resistance (PHR) obtained by using biaxial currents in a NiO (30 nm)/NiFe (30 nm) bilayers. The measured PHR, Rxy, had a drift resistance due to the intrinsic and extrinsic characteristics caused by magnetization and sample geometry, respectively. The drift voltage due to drift resistance restricted the PHR ratio and could be compensated for by using the auxiliary current Ix for the sensing current Iy to enhance PHR ratio. A huge PHR ratio over 3000% (±1500%) with the linearity and small hysteresis for the magnetic field experimentally obtained using biaxial currents and could be explained by the anisotropic characteristic of the magnetoresistance, which is influenced by the exchange coupling field (Hex) induced by the antiferromagnetic NiO layer. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The thermalization of nonequilibrium electrons and phonons is investigated theoretically within the framework of a semiclassical description of the Boltzmann equation. The electrons are assumed to be excited in the intraband absorption in a polar semiconductor and subsequently undergo a Fröhlich interaction to generate hot phonons. The coupled nonlinear Boltzmann equations for the electron-phonon system are directly solved numerically utilizing a discretization scheme. Consequently, a detailed analysis is given of the relaxation dynamics of the distribution functions and the decay of the hot electron and phonon temperatures. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The uniaxial anisotropy field HK and angle γ from exchange coupling field in anisotropic magnetoresistance sample has been analyzed on the basis of the rotational magnetization of single domain. The anisotropy field HK in bilayer NiO(30 nm)/NiFe(t) obtained from the measured magnetoresistance profiles at magnetizing angle θ=0° and 90° from the exchange coupling field changes from positive to negative as the thickness of NiFe increases, transition at about 20 nm. The anisotropy field |HK|, and angle γ show a minimum values at the transition thickness, which is the optimum thickness in anisotropic magnetoresistance sample design in order to increase the field sensitivity and reduces hysteresis loss. © 1999 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The enhanced positive magnetoresistance effect has been observed in GaAs containing nanoscale magnetic clusters. The ferromagnetic metallic clusters were embedded into GaAs by Mn ion implantation and rapid thermal annealing. Positive magnetoresistance in these structures has been observed and attributed to the enhanced geometric magnetoresistance effect in inhomogeneous semiconductors with metallic inclusions. The additional enhancement of positive magnetoresistance under light illumination is due to the higher mobility of photoexcited electrons in comparison with the mobility of holes in p-type GaAs prepared by Mn ion implantation. © 2001 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Photoluminescence (PL) measurements have been carried out to investigate the effects of the band-tail states on the exciton lines in unintentionally doped and Mg-doped GaN epilayers grown on sapphire substrates by using plasma-assisted molecular beam epitaxy. The results of the PL spectra for the Mg-doped epilayers show that the peak positions of the bound exciton lines shift to higher energy with increasing temperature within the low-temperature region. The radiative recombinations of the carriers are related to the band-tail states, and the temperature-dependent blueshifts are analyzed by using a Gaussian distribution of charged impurities. The calculated thermal activation energies of the band-edge emission lines show that those lines in Mg-doped GaN epilayers are related to ionized donor bound exciton recombinations. These results indicate that the positions and the intensities of the exciton peaks observed in Mg-doped GaN films are significantly affected by the concentration of the magnesium dopant. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The in-plane, dipolar anisotropy of a soft magnetic thin film with columnar growth features is thought to result from the alignment and eccentricity of the column cross sections. This anisotropy can be reduced either by randomizing the alignment of the elliptic axes or by reducing the eccentricity. To determine the origin of the reductions produced by processing variations, we image processed micrographs from transmission electron microscope (TEM) of sequentially sputtered, amorphous CoB alloy thin films, and correlated their in-plane magnetic anisotropies with the statistics of the nanoscale features in their morphologies. The results confirmed that the in-plane anisotropies were dominated by correlations in the alignment of the major axes of the anisotropic growth features. Reduced anisotropies were observed in obliquely deposited films grown under the influence of a substrate bias, even though the eccentricity in their growth features was significantly increased. The effect of the increased eccentricity was apparently overcompensated by a randomization in the orientation of the features of the relaxed film structures.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Sequentially cosputtered, amorphous thin films with an average composition of 〈Co61B39〉 were found to have an anomalously high Curie temperature (〉575 K) compared to those reported for their bulk counterparts. Melt-spun Co-B ribbons, for example, with only 30-at. % B(max) have a measured Tc ≈500 K. Tc of ≤300 K would be expected for ribbons with 39-at. % B. The sputtered films crystallized at ≈675 K, but became extremely soft when annealed in a rotating field at 500 K≤Tc. The coercivity of the as-deposited films was reduced from 1 to 2 Oe to approximately 0.01 Oe and the large uniaxial anisotropies of 5–10 Oe vanished; the annealed films were isotropic. Extremely large initial permeabilities of 8000–10 000 were measured to over 10 MHz. The observed anomalies indicate that the center regions of the columnar structure of the sputtered films were enriched by ≈10% Co compared to the boundaries.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

A high-current ion source requires a high-density plasma source to provide sufficient ions to be accelerated. For a continuous high-power ion source, a new concept ion source using a helicon plasma source has been developed. A compact high-density helicon plasma is generated with very high-power efficiency, and ion beams are extracted from the plasma source. With various plasma parameters, extracted ion-beam characteristics are studied in a helicon ion source for the first time. Plasma parameters, especially plasma density, are shown to be strongly correlated with the extracted beam characteristics. © 2000 American Institute of Physics.

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