Search Results - (Author, Cooperation:C. C. Wu)

2011-07-23

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Base Pairing ; Catalytic Domain ; Crystallography, X-Ray ; DNA/*chemistry/metabolism ; DNA Topoisomerases, Type II/*chemistry/genetics/metabolism ; DNA-Binding Proteins/*chemistry/genetics/metabolism ; Drug Resistance, Neoplasm ; Etoposide/analogs & derivatives/*chemistry/metabolism/*pharmacology ; Humans ; Models, Molecular ; Mutant Proteins/chemistry/metabolism ; Mutation ; Protein Multimerization ; Protein Structure, Quaternary ; Protein Structure, Tertiary ; Structure-Activity Relationship ; Topoisomerase II Inhibitors/*chemistry/metabolism/*pharmacology

2015-11-13

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Adenocarcinoma/drug therapy/metabolism/pathology ; Animals ; Carcinoma, Pancreatic Ductal/drug therapy/metabolism/pathology ; Cell Proliferation/drug effects ; Deoxycytidine/analogs & derivatives/pharmacology/therapeutic use ; Disease Models, Animal ; Disease Progression ; Drug Resistance, Neoplasm/*drug effects ; *Epithelial-Mesenchymal Transition ; Female ; Male ; Mice ; Neoplasm Invasiveness/pathology ; Neoplasm Metastasis/*pathology ; Nucleoside Transport Proteins/metabolism ; Pancreatic Neoplasms/*drug therapy/genetics/metabolism/*pathology ; Survival Analysis ; Transcription Factors/deficiency/genetics/metabolism ; Twist Transcription Factor/deficiency/genetics/metabolism

2018-05-30

American Physical Society (APS)

1098-0121

1095-3795

Physics

Errata

1089-7550

AIP Digital Archive

Physics

Heavily carbon-doped GaAs (1×1018∼1×1020 cm−3) grown by low-pressure metalorganic chemical vapor deposition using triethylgallium and arsine as sources and liquid carbon-tetrachloride (CCl4) as dopant has been investigated. The carrier concentration was verified at various growth temperatures, V/III ratios, and CCl4 flow rates. Dopant concentration first increased from 550 °C and reached a maximum at 570 °C growth temperature (Tg) and then decreased monotonously. Carbon incorporation was strongly enhanced when the V/III ratio was less than 30 at Tg=590 °C or less than 40 at Tg=630 °C. Hole concentration increased and then decreased as CCl4 flow rate increased. Growth rate of layers decreased as growth temperature and flow rate of CCl4 increased. The doping efficiency of epitaxial layers grown on the (100) substrate was higher than that on the 2° off toward 〈110(approximately-greater-than) misoriented substrate. Carbon-doped GaAs films had higher Hall mobility than zinc-doped GaAs films at high doping levels due to less self-compensation. The highest dopant concentration in this system was 2.3×1020 cm−3 at Tg=580 °C and V/III=10.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We have successfully grown In0.49Ga0.51P/GaAs heterostructures and made InGaP-based high electron mobility transistors (HEMTs) by low-pressure metalorganic chemical vapor deposition. We have found the epitaxial layer of InGaP with a Hall mobility of 4073 cm2/V s (300 K) and the photoluminescence full width at half-maximum of 1 meV (4.2 K) for GaAs, 12 meV (4.2 K) for In0.49Ga0.51P. Zinc-induced disordering phenomenon was examined by transmission electron microscope. By Shubnikov-de Haas measurement, we demonstrated the existence of a two-dimensional electron gas in InGaP/GaAs heterojunctions. The sheet carrier concentration of 2DEG is around 8.8×1011 cm−2 at 1.5 K. A HEMT device with 1 μm×40 μm gate (pattern) shows an extrinsic transconductance of 65.5 mS/mm and an intrinsic transconductance of 266 mS/mm at 300 K.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We studied the subband energy levels in AlGaAs/GaAs multiple quantum wells grown at different temperatures (200–600 °C) by using the piezoreflectance and photoreflectance in room temperature. Under subsequent 30 s rapid-thermal annealing at different temperatures (600–1000 °C), we observed a large energy blueshift in samples with growth temperature below 400 °C. This blueshift energy may be attributed to the modification of quantum wells caused by gallium vacancy enhanced Al–Ga interdiffusion. The energy blueshifts were analyzed by solving Fick's second law for Al diffusion in quantum wells, obtaining an effective activation energy of 0.75 eV. We discuss our results using the nonequilibrium diffusion equation and comparing them with other experiments. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Low-temperature (20 K) luminescent properties of heavily carbon- and zinc-doped GaAs grown by low-pressure metalorganic chemical vapor deposition were investigated. The luminescence linewidth became broader at low temperatures when p(approximately-greater-than)4×1019 cm−3 due to the appearance of a shoulder peak. The main peak shifted to low energy when the dopant concentration was increased; however, the shoulder peak was at around 1.485 eV and was nearly independent of the dopant concentration. The peak of the band-to-acceptor transition occurred at low temperature and dominated the emission spectra of degenerate GaAs. The peak energy of Zn-doped samples was lower than that of C-doped samples because of the existence of defects. The excitation power intensity was varied to investigate the behavior of the shoulder peak for both types of dopants. The shoulder peak was a part of the main peak because of the recombination between the conduction band and the bottom of the impurity band.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

An anomalous mobility enhancement and metallic-type conductivity were observed in heavily carbon-doped GaAs grown by low-pressure metalorganic chemical vapor deposition. The 77 K mobility was slightly lower than that of 300 K for hole concentration between 1×1018 and 4×1018 cm−3. However, the 77 K mobility was enhanced from p(approximately-greater-than)4×1018 cm−3, and the 300 K mobility slowly decreased with increasing hole concentration that ranged from 7×1018 to 3×1019 cm−3. As a result, the 77 K mobility was around 50%–60% greater than the 300 K mobility due to the metallic-type conductivity.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Ink-jet printing was used to directly deposit patterned luminescent doped-polymer films. The luminescence of polyvinylcarbazol (PVK) films, with dyes of coumarin 6 (C6), coumarin 47 (C47), and nile red was similar to that of films of the same composition deposited by spin coating. Light emitting diodes with low turn-on voltages were also fabricated in PVK doped with C6 deposited by ink-jet printing. © 1998 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We report a demonstration of the integration of individual polymer-based light emitting devices of three different colors on the same substrate. Orange, green, and blue color devices are sequentially fabricated on the same indium–tin oxide (ITO) coated glass substrate coated with a patterned insulator on the ITO, by the spin coating of polymer thin films, the vacuum deposition of top metal contacts, and the patterning of polymer thin film by plasma etching, using the top metal contacts as the self-aligned etching mask. The devices exhibit no degradation of device characteristics due to the integration processing compared to discrete devices on separate substrates. This demonstration shows a new path towards the fabrication of high performance low-cost full-color organic flat panel displays. © 1996 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Transverse mode emission characteristics of gain-guided surface emitting lasers at 0.85 μm were investigated. Up to six nondegenerate circularly symmetrical modes were observed with detunings between the adjacent modes around 2.5 A(ring). Numerical simulations were performed. The calculated beam sizes, difference of modal gains to account for the side mode suppression ratio when operated with one dominant mode, and wavelength detunings agreed with experiments. Numerical simulations also predict that the mirror loss due to Gaussian beam diffraction is nonnegligible for the 1.3–1.55 μm devices.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Ga0.51In0.49P/GaAs tunneling emitter bipolar transistors (TEBTs) grown by gas source molecular beam epitaxy with different barrier thicknesses (50 and 100 A(ring)) have been fabricated and measured at different temperatures (77 and 300 K) for the first time. A current gain of 141 and an offset voltage of 50 mV at room temperature were achieved in the thick barrier (100 A(ring)) device with heavily doped p+ (1×1019 cm−3) base. The thinner device had a lower gain (∼53) than the thick barrier device at room temperature. The functional dependence of gain on thickness was attributed to carrier tunneling through the barrier inserted between the base and the emitter. The low-temperature (77 K) results showed that the gain of the thick barrier device was almost the same as that at 300 K while that of the thin barrier device increased, which was explained by the nonequilibrium electron transport in the base.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Results are presented from polymer/molecular organic heterostructure light emitting diodes composed of a layer of the conjugated conducting polymer poly(p-phenylene vinylene) (PPV), and a layer of fluorescent molecular compound tris(8-hydroxy) quinoline aluminum (Alq). The external quantum efficiency of these heterostructure LEDs is ∼0.1%, which is over one order of magnitude higher than that of simple PPV LEDs. The electroluminescence (EL) spectra indicate that both materials in the device emit comparable amounts of light. The dependence of the EL spectra on the layer thicknesses and its independence on bias suggest that neutral excitons are formed in the Alq, far from the PPV/Alq interface, and subsequently diffuse into the PPV layer. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We demonstrate the improvement of an indium tin oxide anode contact to an organic light emitting device via oxygen plasma treatment. Enhanced hole-injection efficiency improves dramatically the performance of single-layer doped-polymer devices: the drive voltage drops from 〉20 to 〈10 V, the external electroluminescence quantum efficiency (backside emission only) increases by a factor of 4 (from 0.28% to 1%), a much higher drive current can be applied to achieve a much higher brightness (maximum brightness ∼10,000 cd/m2 at 1000 mA/cm2), and the forward-to-reverse bias rectification ratio increases by orders of magnitude (from 102 to 106–107). The lifetime of the device is also enhanced by two orders of magnitude. © 1997 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

An efficient and morphologically stable pyrimidine-containing spirobifluorene-cored oligoaryl, 2,7-bis[2-(4-tert-butylphenyl)pyrimidine-5-yl]-9,9′-spirobifluorene (TBPSF), as an emitter or a host for blue organic light-emitting devices (OLEDs), is reported. The steric hindrance inherent with the molecular structure renders the material a record-high neat-film photoluminescence (PL) quantum yield of 80% as a pure blue emitter (PL peak at 430 nm) of low molecular weight, and a very high glass-transition temperature (Tg) of 195 °C. Blue OLEDs employing this compound as the emitter or the emitting host exhibit unusual endurance for high currents over 5000 mA/cm2. When TBPSF is used as a host for perylene in a blue OLED, maximal brightness of ∼80 000 cd/m2 had been achieved, representing the highest values reported for blue OLEDs under dc driving. © 2002 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

In this letter, we report a promising type of electrically programmable, i.e., reconfigurable, organic light-emitting devices (OLEDs) incorporating a thin carrier-blocking layer as the sacrificial fusing layer. In such devices, the carrier-blocking layer has a lower glass transition temperature than neighboring layers. By raising the internal temperature of the device above the transition temperature of the carrier-blocking layer with a large enough current, interdiffusion between organic layers could occur through such a layer. As a consequence, neighboring layers are fused and a new path for carrier transport is formed, bypassing the carrier-blocking property and altering the device characteristics. A device that emits blue light as fabricated but can be transformed into a green-emitting one is demonstrated. Such a type of device may be used for color pixels in OLED displays, user-programmable OLED applications, and nonvolatile memory devices.© 2001 American Institute of Physics.

Electronic Resource

1089-7666

AIP Digital Archive

Physics

The Cohen–Kulsrud–Burgers equation (CKB) is used to consider the nonlinear evolution of resistive, quasiparallel Alfvén waves subject to a long-wavelength, plane-polarized, monochromatic instability. The instability saturates by nonlinear steepening, which proceeds until the periodic waveform develops an interior scale length comparable to the dissipation length; a fast or an intermediate shock then forms. The result is a periodic train of Alfvén shocks of one or the other type. For propagation strictly parallel to the magnetic field, there will be two shocks per instability wavelength. Numerical integration of the time-dependent CKB equation shows that an initial, small-amplitude growing wave asymptotes to a stable, periodic stationary wave whose analytic solution specifies how the type of shock embedded in the shock train, and the amplitude and speed of the shock train, depend on the strength and phase of the instability. Waveforms observed upstream of the Earth's bowshock and cometary shocks resemble those calculated here.

Electronic Resource

1365-2044

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

We have proposed an equation for estimating the real-time mixed venous blood concentration (MVBC) of isoflurane in cardiac anaesthesia. However, information related to the application of our method to sevoflurane is lacking. We studied 12 patients undergoing cardiac surgery and anaesthetised with sevoflurane. At different time points, pulmonary arterial blood samples were collected for gas chromatography-mass spectrometry (GC-MS) to determine the real mixed venous concentrations of sevoflurane. The inspired and expired concentrations of sevoflurane, measured by a gas monitor, were used for the MVBC calculations. Using Bland-Altman analyses, we found that the calculated MVBCs accurately represent the actual concentrations of sevoflurane in pulmonary arterial blood, as shown by a near-zero percentage bias with a 0.14% precision between the two concentrations. The results demonstrated that our equation could be a useful method for estimating the pulmonary blood concentration of sevoflurane.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Behaviors of an excess proton in solute-containing water clusters were investigated using infrared spectroscopy and ab initio calculations. This investigation characterized the structures of protonated methanol-water clusters, H+(CH3OH)(H2O)n with n=2–6, according to their nonhydrogen-bonded and hydrogen-bonded OH stretches in the frequency range of 2700–3900 cm−1. Ab initio calculations indicated that the excess proton in these clusters can be either localized at a site closer to methanol, forming a methyloxonium ion core (CH3OH2+), or at a site closer to water, forming a hydronium ion core (H3O+). Infrared spectroscopic measurements verified the calculations and provided compelling evidence for the coexistence of two distinct structural isomers, CH3OH2+(H2O)3 and H3O+(CH3OH)(H2O)2, in a supersonic expansion. The spectral signatures of them (either CH3OH2+ or H3O+ centered) are the free-OH stretching absorption band at 3706 cm−1 of a single-acceptor-single-donor H2O, and the band at 3673 cm−1 of a single-acceptor CH3OH. At n=4–6, the clusters adopt structures similar to their pure water analogs with five-membered rings starting to form at n=5. The position of the excess proton in them varies sensitively with the number of solvent water molecules as well as the geometry of the clusters. To further elucidate the behaviors of the excess proton in these clusters, we analyze in detail the potential energy surface along the proton transfer coordinate for two specific isomers of n=2 and 4: MW2II and MW4I. It is found that the proton can be nearly equally shared by methanol and the water dimer subunit in the form of CH3OH–H+–(H2O)2, as substantiated by hydrogen bond cooperativity and zero-point vibrational effects. © 2000 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Infrared spectra of CH stretches have been investigated on the surfaces of synthetic diamond crystallites (5, 100, and 700 nm in diameter) to provide insights into the mid-infrared emission bands of stardusts in interstellar media. While the spectrum of 5-nm diamonds fails to display the distinct 2835 cm−1 (or 3.53 μm) band, a remarkably good match of the absorption bands of larger diamond grains with the emission observed for the stars Elias 1 and HD 97048 is obtained. Suggested by this study, the nanodiamonds that can display such characteristic emission bands at 3.53 μm in these two interstellar systems have a size significantly larger than 5 nm. © 2002 American Institute of Physics.

Electronic Resource