bluuebunny/crossref_metadata_2025 huggingface dataset:
GCN2 eIF2 kinase promotes prostate cancer by maintaining amino acid homeostasis
Authors: Cordova Ricardo A , Misra Jagannath , Amin Parth H , Klunk Anglea J , Damayanti Nur P , Carlson Kenneth R , Elmendorf Andrew J , Kim Hyeong-Geug , Mirek Emily T , Elzey Bennet D , Miller Marcus J , Dong X Charlie , Cheng Liang , Anthony Tracy G , Pili Roberto , Wek Ronald C , Staschke Kirk A
Published: September 2022

A stress adaptation pathway termed the integrated stress response has been suggested to be active in many cancers including prostate cancer (PCa). Here, we demonstrate that the eIF2 kinase GCN2 is required for sustained growth in androgen-sensitive and castration-resistant models of PCa both in vitro and in vivo, and is active in PCa patient samples. Using RNA-seq transcriptome analysis and a CRISPR-based phenotypic screen, GCN2 was shown to regulate expression of over 60 solute-carrier (SLC) genes, including those involved in amino acid transport and loss of GCN2 function reduces amino acid import and levels. Addition of essential amino acids or expression of 4F2 (SLC3A2) partially restored growth following loss of GCN2, suggesting that GCN2 targeting of SLC transporters is required for amino acid homeostasis needed to sustain tumor growth. A small molecule inhibitor of GCN2 showed robust in vivo efficacy in androgen-sensitive and castration-resistant mouse models of PCa, supporting its therapeutic potential for the treatment of PCa.
Bombardier beetles repel invasive bullfrogs
Authors: Sugiura Shinji , Date Tomoki
Published: September 2022

Invasive non-native predators negatively affect native species; however, some native species can survive the predation pressures of invasive species by using pre-existing antipredator strategies or evolving defenses against invasive predators. The American bullfrog Lithobates catesbeianus (Anura: Ranidae) has been intentionally introduced to many countries and regions, and has impacted native animals through direct predation. Bombardier beetles (Coleoptera: Carabidae: Brachininae: Brachinini) discharge chemicals at a temperature of approximately 100 °C from the tip of the abdomen when they are attacked by predators. This “bombing” can successfully repel predators. However, adults of a native bombardier beetle Pheropsophus (Stenaptinus) occipitalis jessoensis have been reportedly found in the gut contents of the introduced bullfrog L. catesbeianus in Japan. These records suggest that the invasive bullfrog L. catesbeianus attacks the native bombardier beetle P. occipitalis jessoensis under field conditions in Japan; however, the effectiveness of the bombing defense against invasive bullfrogs is unclear. To test the effectiveness of the bombing defense against bullfrogs, we investigated the behavioral responses of L. catesbeianus juveniles to P. occipitalis jessoensis adults under laboratory conditions. Contrary to previous gut content results, almost all the bullfrogs (96.3%) rejected bombardier beetles before swallowing them; 88.9% rejected the beetles after being bombed, and 7.4% stopped attacking the beetles before being bombed. Only 3.7% successfully swallowed and digested the beetle. All of the beetles collected from non-bullfrog-invaded sites could deter bullfrogs, suggesting that the pre-existing defenses of bombardier beetles played an essential role in repelling bullfrogs. When treated beetles that were unable to discharge hot chemicals were provided, 77.8% of bullfrogs successfully swallowed and digested the treated beetles. These results indicate that bombing is important for the successful defense of P. occipitalis jessoensis against invasive bullfrogs. Although invasive bullfrogs have reportedly impacted native insect species, P. occipitalis jessoensis has an existing defense mechanism strong enough to repel the invasive predators.
Analysis of road traffic injuries and casualties in China: a ten-year nationwide longitudinal study
Authors: Qi Miao , Hu Xiuli , Li Xiahong , Wang Xue , Shi Xiuquan
Published: September 2022

Background

Road traffic injuries (RTIs) are a serious global problem, and a huge challenge for both economic development and public health.

Methods

This longitudinal study was based on the national data from Chinese authorities. Descriptive analysis was utilized to analyze the prevalence and trend of RTIs among different types, groups and regions. In addition, ridge regression or/and curve regression were also used to explore the relationship between those possible influencing factors and RTIs.

Results

From 2010 to 2019, the death toll from motor vehicle accidents (MVAs) decreased firstly and then increased, while the death toll from non-MVAs continued to rise since 2012, and the death toll from pedestrian and occupant accidents fluctuated only a little. The mortality rate of MVA was relatively stable from 2010 to 2012, and declined from 2013. The mortality rate of motor vehicle accidents was higher in rural than urban, the same to male compared with female. The results of ridge regression showed that gross domestic product (GDP)-per-capita, total population, number of health personnel and car ownership were positively correlated with the death toll of non-MVAs (P < 0.05). Additionally, the results of curve regression suggested that the quadratic or cubic relationship between each factor and the number of MVAs was well fitted, while only partially fitted in fatalities.

Conclusions

In recent years, RTIs in China show different trends, and the problem of non-motor vehicle traffic injuries has been neglected which should be paid more attention. Moreover, according to the new trends and traffic conditions in RTIs revealed in this study, it is necessary to formulate targeted intervention measures establish a multi-faceted comprehensive safety system to reduce the disease burden of RTIs as well as the total injuries.
miR-378 associated with proliferation, migration and apoptosis properties in A549 cells and targeted NPNT in COPD
Authors: Qian Guoqing , Liao Qi , Li Guoxiang , Yin Fengying
Published: September 2022

Background

microRNAs contribute to the development and progression of chronic obstructive pulmonary disease (COPD). However, the underlying molecular mechanisms are largely unclear. The goal of this study was to investigate the roles of miR-378 in alveolar epithelial type II cells and identify molecular mechanisms which contribute to the pathogenesis of COPD.

Materials and methods

Human alveolar epithelial (A549) cells were cultured in Dulbecco’s Modified Eagle Medium. Cell proliferation was studied by using a cell counting kit-8 (CCK-8) and colony formation assays. Cell apoptosis and cell cycle were analyzed by flow cytometry and wound healing and Transwell were used to analyze the cell migration and. We performed bioinformatics analysis including target gene prediction, gene ontology (GO), Kyoto Encyclopedia of Genes and Genome (KEGG) pathway enrichment and construction of protein-protein interaction (PPI) network. The expression of miR-378 and NPNT from publically available expression microarray of COPD lung tissues was analyzed.

Results

Overexpression of miR-378 significantly increases cell proliferation, migration, and suppress apoptosis. GO analysis demonstrated that the miR-378 involved in transcription, vascular endothelial growth factor receptor signaling pathway, phosphatidylinositol 3-kinase signaling, cell migration, blood coagulation, cell shape, protein stabilization and phosphorylation. Pathway enrichment showed that the 1,629 target genes of miR-378 were associated with mTOR, ErbB, TGF-β, MAPK, and FoxO signaling pathways. Notably, miR-378 directly targets Nephronectin in A549 cells, and miR-378 was upregulated while NPNT was downregulated in COPD lung tissue samples.

Conclusions

These findings suggest that miR-378 can regulate the proliferation, migration, and apoptosis of A549 cells and target NPNT. miR-378 increased in COPD lung tissues while NPNT decreased, and might prove a potential target for novel drug therapy.
Cruzando tempo(s) e produzindo memórias do ativismo HIV/Aids no Brasil
Authors: Wiik Flávio , Duque Tiago , Oliveira Esmael Alves de
Published: September 2022

Não se aplica
Differential effects of Cbl and 70Z/3 Cbl on T cell receptor‐induced phospholipase Cγ‐1 activity
Authors: Graham Laurie J. , DeBell Karen E. , Verı́ Maria-Concetta , Stoica Bogdan , Mostowski Howard , Bonvini Ezio , Rellahan Barbara
Published: July 2002

We demonstrate that the differential effects Cbl and oncogenic 70Z/3 Cbl have on Ca2+/Ras‐sensitive NF‐AT reporters is partially due to their opposing ability to regulate phospholipase Cγ1 (PLCγ1) activation as demonstrated by analysis of the activation of an NF‐AT reporter construct and PLCγ1‐mediated inositol phospholipid (PI) hydrolysis. Cbl over‐expression resulted in reduced T cell receptor‐induced PI hydrolysis, in the absence of any effect on PLCγ1 tyrosine phosphorylation. In contrast, expression of 70Z/3 Cbl led to an increase in basal and OKT3‐induced PLCγ1 phosphorylation and PI hydrolysis. These data indicate that Cbl and 70Z/3 Cbl differentially regulate PLCγ1 phosphorylation and activation. The implications of these data on the mechanism of Cbl‐mediated signaling regulation are discussed.
Lipase Production by Acinetobacter radioresistens in the Presence of a Nonwoven Fabric
Authors: Shen Chi‐Chih , Wu Jau‐Yann , Chen Chuh‐Yung , Chen Teh‐Liang
Published: July 2002

Lipase production by Acinetobacter radioresistens was performed in a 2‐L tank fermentor equipped with a nonwoven fabric, which was made of nylon 6 fiber and coated with a hydrophobic acrylic resin. The fermentation medium contained 2% (v/v) n‐hexadecane as the carbon source. The use of the nonwoven fabric was intended for the dispersion of hydrocarbons; thus, the contact surface for the cells to assimilate n‐hexadecane can be increased without using emulsifiers. The formation of lipase was found to be growth‐associated when the cells grew on n‐hexadecane. The use of the nonwoven fabric increased the lipase yield by 130%. Further supplementation of 0.1% (v/v) olive oil to the medium could markedly shorten the fermentation time, and thus increase the volumetric productivity. The use of the nonwoven fabric offered two additional advantages in the lipase fermentation: ease of foam control and favorable partition of lipase in the aqueous phase.
Granular cell tumour of the oesophagus: Endoscopic ultrasound appearances
Authors: Love MHS , Glaser M , Edmunds SEJ , Mendelson RM
Published: July 2002

A case of granular cell tumour of the oesophagus in a middle‐aged woman is reported. The pathological features and appearances on endoscopic ultrasound (EUS) are described, and the role of EUS in the characterization of intramural oesophageal tumours is discussed.
Far-infrared cavity dump coupling of the UC Santa Barbara free-electron laser
Authors: Kaminski J. P. , Spector J. S. , Felix C. L. , Enyeart D. P. , White D. T. , Ramian G.
Published: July 2002

A Nd:YAG laser-induced semiconductor switch for far-infrared (FIR) radiation was mounted inside a free-electron laser (FEL) wiggler cavity to act as an intracavity output coupler. By timing the FEL to the Q-switched laser, the FIR switch could be turned on during the intracavity laser saturation period. In addition to demonstrating the generation of short, high peak power pulses, the cavity dump coupler (CDC) was used for the first time to image the intracavity mode structure of a FEL and to perform steady-state saturation spectroscopy studies in the FIR.
High coercivity in Sm2Fe17Nx magnets
Authors: Schnitzke K. , Schultz L. , Wecker J. , Katter M.
Published: July 2002

Using mechanical alloying and a subsequent two-step heat treatment we produced magnetically isotropic microcrystalline Sm2Fe17Nx samples with room-temperature coercivities up to 24 kA/cm (30 kOe). The remanence and the energy product are equivalent to similarly prepared Nd-Fe-B samples, but the properties at elevated temperatures are superior because of the high Curie temperature of 470 °C and the large anisotropy field of 14 T at room temperature. From differential scanning calorimetry it is concluded that the 2:17 nitride is metastable. It decomposes into Sm nitride and α-Fe above 600 °C.
Thickness dependence of the twin density in YBa2Cu3O7−δ thin films sputtered onto MgO substrates
Authors: Streiffer S. K. , Zielinski E. M. , Lairson B. M. , Bravman J. C.
Published: July 2002

The lengths and spacings of twins in YBa2Cu3O7−δ thin films deposited onto MgO substrates have been measured by transmission electron microscopy as a function of film thickness t, for t ranging from 50 to 1400 nm. The twin length is linear in t, while the twin spacing follows a t1/2 dependence. This form for the twin spacing is consistent with the prediction of a simple free energy expression for the twinning transformation.
Off-state leakage currents in n-channel metal-oxide-semiconductor field-effect transistors with 10-nm thermally nitrided and reoxidized nitrided oxides as the gate dielectric
Authors: Fleischer S. , Liu Z. H. , Lai P. T. , Ko P. K. , Cheng Y. C.
Published: July 2002

The effects of nitridation and reoxidation on the off-state leakage currents of n-channel metal-oxide-semiconductor-field-effect transistors have been investigated. It is found that nitridation greatly increases the gate leakage in the low-field range but ensuing reoxidation can effectively reduce it. Nitridation-induced oxide traps could be responsible for this leakage, along with traps introduced during the source/drain implant. A trap-assisted tunneling model has been proposed to explain this off-state gate leakage.
Capacitively coupled glow discharges at frequencies above 13.56 MHz
Authors: Surendra M. , Graves D. B.
Published: July 2002

Particle-in-cell/Monte Carlo simulations of glow discharges between parallel plate electrodes indicate that operation at frequencies above 13.56 MHz offers a number of attractive features for plasma processing applications. Plasma density and ion current scale approximately as the square of frequency, but maximum ion energy is unaffected to first order when applied voltage, pressure and electrode spacing remain constant. In addition, raising frequency decreases sheath thickness, thereby increasing ion directionality in the sheath at constant pressure. By manipulating both frequency and rf voltage, it is possible to control ion current and energy independently.
Flux pinning in hot isostatically pressed Bi2Sr2CaCu2Ox
Authors: Miller D. J. , Sengupta S. , Hettinger J. D. , Shi D. , Gray K. E. , Nash A. S. , Goretta K. C.
Published: July 2002

Magnetic hysteresis data were taken from 4.2 to 35 K on Bi2Sr2CaCu2Ox samples that were hot isostatically pressed at 105 MPa in an inert atmosphere at 825 °C. One set of samples was pressed for only 15 min while the other was pressed for 120 min. The samples pressed for 15 min contained a high density of dislocations and planar faults, while the samples pressed for 120 min contained fewer dislocations and faults, with most dislocations present within subgrain boundaries. The samples with the complex dislocation/planar fault structures exhibited substantially larger hysteresis loops, suggesting enhanced flux pinning.
Josephson coupling of YBa2Cu3O7−x through a ferromagnetic barrier SrRuO3
Authors: Antognazza L. , Char K. , Geballe T. H. , King L. L. H. , Sleight A. W.
Published: July 2002

Epitaxial barriers of ferromagnetic SrRuO3 have been used to fabricate high Tc superconductor-normal-superconductor Josephson junctions in the edge junction geometry. At small barrier thicknesses the SrRuO3 junctions follow the behavior of nonferromagnetic but otherwise closely related CaRuO3 junctions. A rapid disappearance of critical current is observed when the barrier thickness is increased to 250 Å. Possible origins of such a large critical thickness are discussed.
Generation of femtosecond optical pulses with nanojoule energy from a diode laser and fiber based system
Authors: Galvanauskas A. , Blixt P. , Tellefsen J. A.
Published: July 2002

Linearly chirped, subnanosecond optical pulses, emitted at an arbitrary repetition rate by a fast-tuned monolithic diode laser, were compressed down to 600 fs by group-velocity dispersion in a standard optical fiber. Subsequent amplification and nonlinear compression in an erbium-doped fiber amplifier produced pulses with the energy of up to 2 nJ and the duration down to 230 fs.
Enhanced differential magnetostrictive response in annealed Terfenol-D
Authors: Galloway N. , Schulze M. P. , Greenough R. D. , Jiles D. C.
Published: July 2002

The field and pressure dependencies of the magnetostriction of Tb0.316Dy0.684Fe1.982 have been measured in a grain-oriented rod after thermally annealing for 1 day at 850 °C and for 4 days at 950 °C in an argon atmosphere. The results of the heat treatment are a fivefold increase in the strain coefficient d33(=dλ/dH) and a 100% increase in the maximum strain (λ). There was also an increase in the λ-vs-H hysteresis. Under compressive uniaxial stress there was virtually no bulk change in magnetostrictive strain until the field exceeded a critical value which depended on the applied stress, for instance ∼12 kA/m under a stress of 6 MPa.
Wide wavelength and low dark current lattice-mismatched InGaAs/InAsP photodiodes grown by metalorganic vapor-phase epitaxy
Authors: Wada Morio , Hosomatsu Haruo
Published: July 2002

Using a very thin InP/InAsP cap layer and InAsP strained superlattices in a buffer layer, a lattice-mismatched InGaAs/InAsP photodiode with low dark current and very wide wavelength spectral response was fabricated by metalorganic vapor-phase epitaxy. External quantum efficiencies as high as 55% at 0.6 μm, 80%–90% at 0.8–1.9 μm, and 65% at 2.1 μm was obtained. For the 1-mm-diam photodiodes, typical dark current measured at 274 K and at a reverse bias voltage of 0.1 V was as low as 1×10−7 A.
Photoluminescence of porous silicon exposed to ambient air
Authors: Maruyama Toshiro , Ohtani Satoshi
Published: July 2002

The room-temperature photoluminescence and structure were studied concerning porous silicon which was exposed to ambient air. Water vapor in ambient air gradually oxidized the surface of the porous silicon with developing Si—O—Si bonds. This room-temperature oxidation progressively replaced an unstable H-passivated surface with a more stable O-passivated surface, dramatically increasing the intensity of the photoluminescence.
Boron doping of silicon using coalloying with aluminium
Authors: Lölgen P. , Sinke W. C. , Leguijt C. , Weeber A. W. , Alkemade P. F. A. , Verhoef L. A.
Published: July 2002

We present a new technique for boron (B) doping of silicon. In this letter we show that a B doping profile of more than 2 μm thickness with a maximum active doping concentration of 3×1019 cm−3 can be formed by a fast (<1 min) alloying process at a temperature of 850 °C. Thick-film aluminum is used to obtain an alloying and epitaxial regrowth process in accordance with the Al–Si phase diagram. The atomic concentration profile of the B- and Al-doped Si layer was determined by secondary ion mass spectrometry. The active doping concentration was measured with an automatic electrochemical capacitance/voltage profiler. By the addition of B to the Al paste, the epitaxially regrown layer is doped with B and Al to the solid solubility of these elements in Si at the particular regrowth temperature. The applicability of this fast low temperature B doping process in Si solar cell processing is discussed.
High temperature electron cyclotron resonance etching of GaN, InN, and AlN
Authors: Shul R. J. , Kilcoyne S. P. , Hagerott Crawford M. , Parmeter J. E. , Vartuli C. B. , Abernathy C. R. , Pearton S. J.
Published: July 2002

Electron cyclotron resonance etch rates for GaN, InN, and AlN are reported as a function of temperature for Cl2/H2/CH4/Ar and Cl2/H2/Ar plasmas. Using Cl2/H2/CH4/Ar plasma chemistry, GaN etch rates remain relatively constant from 30 to 125 °C and then increase to a maximum of 2340 Å/min at 170 °C. The InN etch rate decreases monotonically from 30 to 150 °C and then rapidly increases to a maximum of 2300 Å/min at 170 °C. This is the highest etch rate reported for this material. The AlN etch rate decreases throughout the temperature range studied with a maximum of 960 Å/min at 30 °C. When CH4 is removed from the plasma chemistry, the GaN and InN etch rates are slightly lower, with less dramatic changes with temperature. The surface composition of the III–V nitrides remains unchanged after exposure to the Cl2/H2/CH4/Ar plasma over the temperatures studied.
Surface reactions of metal clusters I: The fast flow cluster reactor
Authors: Geusic M. E. , Morse M. D. , O’Brien S. C. , Smalley R. E.
Published: July 2002

A new fast flow device for the study of metal cluster reactions in the gas phase is described and characterized. The new device utilizes metal clusters made by laser vaporization of an appropriate metal target mounted in the throat of a supersonic nozzle which exhausts into a fast-flow reaction tube. Reactants are injected into the flowing helium–metal cluster mixture at a point in the flow tube where shock waves have reheated the gas to roughly 320 K. Turbulence in the wake of these shock waves produces efficient mixing of the reactants. Measurement of the flow properties of this reaction tube indicate a residence time of 150–200 μs with an average density of helium buffer gas equivalent to 50–100 Torr at room temperature. Subsequent free expansion of this reaction mixture into a large vacuum chamber produces a supersonic beam with extensive cooling of the various constituents in the mixture (pyrazine was measured to be rotationally cooled to 10 K). The new cluster reaction device is, therefore, an excellent source for future studies of the jet-cooled metal cluster reaction products themselves.
Prepulse suppression in microwave pulse-compression cavities
Authors: Alvarez R. A. , Byrne D. P. , Johnson R. M.
Published: July 2002

It is possible to generate high-power microwave pulses with fast rise time by using resonant cavities to obtain power gain from pulse compression. In the usual case, especially when normal-conducting cavities are used, the principal output pulse from a pulse-compression device is preceded by a precursor signal that may be only 40 dB below the main pulse. For some applications this large a prepulse is unacceptable. We have developed a prototype normal-conducting, x-band, pulse-compression cavity in which the prepulse is suppressed by more than 70 dB. When this cavity is driven by a 20-kW source, output pulses with 200-kW peak power, 5-ns pulse width, and sub-nanosecond rise time can be obtained. We have also built an s-band cavity that has produced pulses of 5-ns width, 200-MW peak power, and under 3-ns rise time. The s-band cavity is typically driven at 5–10 MW and has a prepulse that can be more than 80 dB below the peak of the main pulse.
Effects of chemical composition on humidity sensitivity of Al/BaTiO3/Si structure
Authors: Li G. Q. , Lai P. T. , Zeng S. H. , Huang M. Q. , Liu B. Y.
Published: July 2002

Argon-ion-beam sputtering technique has been applied to deposit barium titanate (BaTiO3) films on silicon wafers at room temperature under vacuum, and then Al/BaTiO3/Si structures were fabricated. Results show that the current and capacitance of these devices are sensitive to the change of relative humidity at room temperature, and saturation absorption (response) time as well as humidity sensitivity of the devices depend on the chemical composition of the BaTiO3 films. For higher annealing temperature and longer annealing time, the oxygen composition increases while fixed charge density decreases. These changes result in lower humidity sensitivity and longer response time.
Optical probes for local void fraction measurements: Characterization of performance
Authors: Cartellier Alain
Published: July 2002

Optical probes are widely used in two phase gas-liquid flows, especially in laboratories for experimental research. However, despite all the work previously done on the subject, the performance of these sensors is not yet firmly established. To clarify this point, well controlled experiments dealing with the response of various optical probes during the piercing of an interface are presented. The latency length concept L*, which is the spatial resolution of the interface detection by a given probe, is introduced. The minimum value recorded is about 130 μm. Moreover, this parameter is closely related to the hydrodynamic response time of the sensor, and as such, to the geometric displacement velocity of each interface detected. Hence, the latency length is proposed as an objective basis for the comparison of the different probes. Finally, the relation between the response time and the signal processing techniques is discussed, and it is shown that the shortest length L* must be sought in order to ensure a better accuracy of the local void fraction.
Calibration and characterization of piezoelectric elements as used in scanning tunneling microscopy
Authors: van de Leemput L. E. C. , Rongen P. H. H. , Timmerman B. H. , van Kempen H.
Published: July 2002

We investigated the behavior of piezoelectric elements used in an STM for fine positioning of the tip. Special attention was paid to the influence of hysteresis. We found that the expansion coefficient of the elements depends on the magnitude of the displacements they produce. If the range is limited to several nanometers, the sensitivity can be taken constant and hysteresis can be neglected. However,if displacements of about a micron are involved, the sensitivity is about 40% higher and the hysteresis will significantly disturb the image. We also compared different calibration methods. An inductive displacement transducer yields results which correspond to those obtained with the known height of steps on a flat gold surface. A Michelson interferometer yields results which are valid for large displacements which cannot be used if small-scale structures are imaged.
A novel signal processing scheme for a fluorescence based fiber-optic temperature sensor
Authors: Zhang Zhiyi , Grattan K. T. V. , Palmer A. W.
Published: July 2002

A novel signal processing approach, which results in a significant improvement in the measurement resolution for a fluorescent decay-time-based fiber optic temperature sensor, is proposed. The technique discussed is based on the phase sensitive detection (lock-in) of the fluorescent signal. As with the other phase-sensitive detection techniques, it has the significant advantage of a high noise-suppression ability, but it differs from existing phase sensitive detection methods in several aspects which are discussed to yield this improvement. When the system is used to monitor the fluorescence lifetime of ruby, in the range from 40 °C to 100 °C, the measurement resolution achievable due to the signal processing scheme is ±0.04 °C, and from 100 °C to 200 °C, it is ±0.2 °C. It should be noted that other measurement errors must be reduced to achieve a high accuracy of measurement comparable with this. Finally, the proposed technique can be used not only for the monitoring of fluorescence lifetime, but also for the highly accurate monitoring of the time-constants of other appropriate first order systems, such as a capacitive sensor, operating under high noise conditions.
Auger photoelectron coincidence spectroscopy using synchrotron radiation
Authors: Jensen E. , Bartynski R. A. , Hulbert S. L. , Johnson E. D.
Published: July 2002

The technique of Auger photoelectron coincidence spectroscopy (APECS) using synchrotron radiation is discussed. Technical considerations and experimental details are emphasized. Results from Cu(100), Ta(100), and Al(111) are presented to show the kinds of new information that APECS can provide.
Differential optical absorption spectrometer for measuring atmospheric trace gases
Authors: Plane John M. C. , Nien Chia-Fu
Published: July 2002

The construction of a differential optical absorption spectrometer (DOAS) is described. The instrument was designed for making automated measurements, with relatively high detection sensitivities, of important tropospheric trace gases, and with the ability to operate in rugged environments without frequent attention. Major innovative features of the instrument include a retroreflector to fold the light path, a diode array detector, and computer-controlled operation of the entire instrument package. The advantages of these modifications with respect to previously reported designs are discussed in detail. This DOAS has been employed since 1989 to measure NO3 (1 ppt), NO2 (0.6 ppb), HONO, O3, and CH2O (0.8 ppb), where the mixing ratios in parentheses indicate the detection limits over a 5 km path length and 4 min integration time, for the species where these could be determined.
Resonant tunneling transport across YBa2Cu3O7–SrRuO3 interfaces
Authors: Dömel Regina , Horstmann C. , Siegel M. , Braginski A. I. , Kupriyanov M. Yu.
Published: July 2002

We have investigated superconductor–normal metal–superconductor junctions with metallic perovskite SrRuO3 barriers. Ramp-type junctions with ion-beam-etched and wet-chemical-etched YBa2Cu3O7 (YBCO) ramps have been compared with planar junctions where the interfaces were fabricated completely in situ. Regardless of the fabrication method, the junction properties were determined not by the metallic SrRuO3 barrier, but by an insulating layer at the interface. The shape of the I–V curves, and the temperature dependence of the normal resistance of junctions, could be well explained by quasiparticle resonant tunneling via two localized states in the interface layer. Furthermore, a model for the Cooper pair transport will be discussed that assumes resonant tunneling via one localized state as transport mechanism.
Enthalpy probe performance in compressible thermal plasma jets
Authors: Fincke J. R. , Swank W. D. , Snyder S. C. , Haggard D. C.
Published: July 2002

Enthalpy probe measurements in compressible argon/helium thermal plasma jets are compared with results from high spectral resolution laser light scattering. In the laser scattering measurement the plasma temperature and velocity are determined directly from high-resolution line-shape analysis of light scattered by the plasma. The technique yields an unambiguous determination of gas or kinetic temperature without the assumption of local thermodynamic equilibrium. Velocity is determined directly from the measured Doppler shift. The enthalpy probe is a combination stagnation probe and flowing calorimeter. Gas temperatures and velocities are calculated from measured values using both frozen flow and equilibrium flow assumptions for the stagnation process. Over the Mach number range examined, the assumption of isentropic, frozen composition stagnation best matches the laser results. In the jet periphery a significant streamline displacement is caused by the presence of the probe. The displacement, which is a function of the nondimensional radial velocity gradient, distorts the velocity and temperature results in the wings of the profiles. In the core of the jets examined, probe measurements in both subsonic and supersonic compressible flows show excellent agreement with laser scattering results.
A new smoothing method for obtaining the electron energy distribution function in plasmas by the numerical differentiation of the I-V probe characteristic
Authors: Fernández Palop J. I. , Ballesteros J. , Colomer V. , Hernández M. A.
Published: July 2002

A new smoothing method has been used to obtain the electron energy distribution function (EEDF) in plasmas by evaluating the second derivative of the I-V characteristic of a probe inmersed in the plasma. The smoothing method is based on the use of the instrument function. A comparison with other smoothing techniques has permitted us to show the advantages in using the new smoothing method. The experimental setup used to measure the I-V probe characteristic fast and accurately is also presented. The smoothing method was tested by measuring the EEDF in an argon dc discharge at different conditions of the gas pressure and discharge current. The plasma parameters (electron density and temperature) evaluated from the EEDF were compared with those evaluated by using other classic diagnostic methods obtaining a quite good consistency among them.
Sputtering and thermal effect during ion microbeam patterning of polymeric films
Authors: Ektessabi A. M. , Sano T.
Published: July 2002

The purpose of this article is to investigate the machinability of polymers and the main parameters involved during ion microbeam processing of polymers. Investigations were made for the case of ion microbeam patterning of polyethyleneterephthalate and nylon-6 using a focused ion beam system with a needle type ion source. The extracted beam diameter was 0.2 μm, the current density on the target was 1.0 A/cm2, and the beam energy was 30 keV. The removal rate, which shows the number of atoms removed when an ion impinges on the surface, was obtained experimentally. By comparing the removal rate and the theoretical sputtering yield, it became clear that effects other than sputtering have a great influence on the machinability of polymers. Two-dimensional unsteady heat conduction equations were computed using the finite difference method in order to estimate the temperature increment within and around the beam irradiated area. The results show that localized heating and a change of chemical bonding state during ion microbeam processing strongly influence the patterning of polymers.
Infrared imaging of defects heated by a sonic pulse
Authors: Favro L. D. , Han Xiaoyan , Ouyang Zhong , Sun Gang , Sui Hua , Thomas R. L.
Published: July 2002

High-frequency pulsed sonic excitation is combined with an infrared camera to image surface and subsurface defects. Irreversible temperature increases on the surface of the object, resulting from localized heating in the vicinity of cracks, disbonds, or delaminations, are imaged as a function of time prior to, during, and following the application of a short pulse of sound. Pulse durations of 50 ms are sufficient to image such defects, and result in surface temperatures variations of ∼2 °C above the defect. As an example, sonic infrared images are presented for two fatigue cracks in Al and of interply delamination impact damage in a graphite–fiber-reinforced polymer composite. The shorter of the two fatigue cracks is ∼0.7 mm in length, and is tightly closed. Thus, this new technique is sensitive, and capable of rapid imaging of defects under wide surface areas of an object.
Furnace gas-phase chemistry of silicon oxynitridation in N2O
Authors: Ellis K. A. , Buhrman R. A.
Published: July 2002

During furnace N2O-based silicon oxynitride growth, the total concentration of NOx species varies strongly with the flow rate of N2O. At low flow rates the N2O decomposes at least partially in the cooler region of the furnace near the gas inlet. This results in lower than expected NOx (x=1,2) concentrations in the oxidizing ambient. At high flow rates, the exothermic decomposition of N2O can heat the inlet region of the furnace, resulting in decomposition at a temperature above the nominal furnace temperature and higher than expected NOx concentrations. These effects can lead to a substantial variation in the concentration of N in the oxynitride as a function of N2O flow.
Effects of electron mass anisotropy on Hall factors in 6H-SiC
Authors: Chen G. D. , Lin J. Y. , Jiang H. X.
Published: July 2002

The room temperature Hall factors in 6H-SiC have been measured under different magnetic fields. It is found that the Hall coefficient RH increases with magnetic field, implying a Hall factor of less than one at zero magnetic field. This behavior has been accounted for by a model based on electron mass anisotropy in 6H-SiC. The Hall factor results show that in 6H-SiC the mass along the c direction is a factor of 5 larger than that in the transverse direction and that the electron–phonon scattering time is aobut 1 ps at room temperature, which is consistent with a recent optically detected resonance spectroscopy measurement. Our results indicate that the Hall measurement can be utilized as an effective and simple method for studying scattering mechanisms as well as for determining anisotropic transport properties in SiC and that a correction of the Hall factor is necessary in order to determine the carrier concentration and mobility accurately.
Stochastic electron heating in bounded radio-frequency plasmas
Authors: Kaganovich I. D. , Kolobov V. I. , Tsendin L. D.
Published: July 2002

The mechanisms of electron heating in low-pressure bounded rf plasmas are analyzed. These processes are determined by the combined effect of electron interaction with the rf electric field, reflections from the walls and collisions. It is shown that when the discharge gap is small with respect to the electron mean-free path the finite size of the plasmas is crucial for the stochastic heating. A classification of heating regimes is performed and expressions for the power deposition are derived. In many cases, even though in a semi-infinite plasma heating exists, in a bounded plasma the electron motion is regular and there is no collisionless heating.
ICl/Ar electron cyclotron resonance plasma etching of III–V nitrides
Authors: Vartuli C. B. , Pearton S. J. , Lee J. W. , Hong J. , MacKenzie J. D. , Abernathy C. R. , Shul R. J.
Published: July 2002

Electron cyclotron resonance plasma etch rates for GaN, InN, InAlN, AlN, and InGaN were measured for a new plasma chemistry, ICl/Ar. The effects of gas chemistry, microwave and rf power on the etch rates for these materials were examined. InN proved to be the most sensitive to the plasma composition and ion density. The GaN, InN, and InGaN etch rates reached ∼13 000, 11 500, and ∼7000 Å/min, respectively, at 250 W rf (−275 V dc) and 1000 W microwave power. The etched surface of GaN was found to be smooth, with no significant preferential loss of N from the surface at low rf powers, and no significant residue on the surface after etching.
Measurement of the mean electron-hole pair creation energy in crystalline silicon for photons in the 50–1500 eV spectral range
Authors: Scholze F. , Rabus H. , Ulm G.
Published: July 2002

This letter reports a measurement of the mean electron-hole pair creation energy in crystalline silicon using photons in the 50–1500 eV spectral range. A cryogenic electrical substitution radiometer in combination with monochromatized synchrotron radiation was used to determine the spectral responsivity of silicon photodiodes in this spectral range with a relative uncertainty of less than 0.3%. The mean electron-hole pair creation energy has been determined from these measurements and in contrast to recent theoretical and experimental results a constant value of (3.64±0.03) eV was obtained in accordance with a calculation presented here.
Resonant Raman scattering in GaN/(AlGa)N single quantum wells
Authors: Behr D. , Niebuhr R. , Wagner J. , Bachem K.-H. , Kaufmann U.
Published: July 2002

Resonant Raman scattering has been used to study longitudinal optical (LO) phonon modes in 2–4-nm-wide GaN/Al0.15Ga0.85N single quantum wells (QW). Raman spectra recorded using subband gap excitation were found to be completely dominated by the phonon modes of the (AlGa)N barriers. In contrast, for excitation close to resonance with the lowest transition between confined electron and hole states in the GaN QW scattering by the A1(LO) phonon in the QW became dominant in spite of the narrow width of the QW. For well widths of 3 and 4 nm, the frequency of the A1(LO) phonon in the QW was found to be close to that in bulk GaN, whereas for a well width of 2 nm the QW phonon was broadened and shifted towards the frequency of the (AlGa)N A1(LO) phonon mode. This broadening and frequency shift indicate some cation intermixing for the narrowest QW with the widths of the interface regions being comparable to the well width of 2 nm, demonstrating the usefulness of resonant Raman scattering for quality assessment of GaN/(AlGa)N QWs and interfaces.
Femtosecond continuously tunable second harmonic generation over the entire-visible range in orthorhombic acentric Gd2(MoO4)3 crystals
Authors: Nishioka H. , Odajima W. , Tateno M. , Ueda K. , Kaminskii A. A. , Butashin A. V. , Bagayev S. N. , Pavlyuk A. A.
Published: July 2002

Second harmonic generation over the entire visible range in Nd3+ doped and undoped Gd2(MoO4)3 crystals under ultrashort hypercontinuum pumping is presented. The continuous tuning ranges from 487 to 790 nm in a single crystal.
Near-field scanning optical microscopy of ferroelectric domain walls
Authors: Yang T. J. , Mohideen U. , Gupta Mool C.
Published: July 2002

We have observed domain walls in ferroelectric LiTaO3 crystals using a polarization and phase sensitive near-field scanning optical microscope. The strain induced birefringence was used to observe the domain walls. The domain walls are measured to be 1 μm wide and show a variation of strain along the domain walls probably due to defects. These measurements allow an estimate of the birefringence at the domain wall of 6×10−5 and associated shear strain of 4×10−5.
Dual-functional polymeric waveguide with optical amplification and electro-optic modulation
Authors: An Dechang , Yue Zuzhou , Chen Ray T.
Published: July 2002

Optical amplification and first-order electro-optic effect have been observed simultaneously in one polymeric material photolime gel which has been used widely as a volume holographic material to produce dichromated gelatin films. In this letter, the dual functions were achieved by doping neodymium chloride hexahydrate and chlorophenol red. The optimized doping concentration of Nd+3 is 6.7×1019 cm−3. The weight percentage of chlorophenol red is 23%. We observed a 3.8 dB of optical gain at 1.06 μm and an electro-optic coefficient of 22 pm/V at 633 nm.
Determination of elastic constants in thin films using hydrogen loading
Authors: Laudahn U. , Fähler S. , Krebs H. U. , Pundt A. , Bicker M. , v. Hülsen U. , Geyer U. , Kirchheim R.
Published: July 2002

By measuring stress and strain that build up in thin films during hydrogen absorption, the elastic constants of the films can be determined, if a one-dimensional elastic behavior occurs only. This will be demonstrated for hydrogen absorption in Nb films. The in-plane stress is determined from the substrate curvature that is measured by using a two-beam laser setup. The out-of-plane strain is measured via x-ray diffraction. Furthermore, this method allows us to distinguish whether the film is plastically or elastically deformed by checking the reversibility of the stress–strain curve. In the case of a 250-nm-thick Nb film, the elastic constants obtained are similar to that of bulk Nb.
Positioning of self-assembled, single-crystal, germanium islands by silicon nanoimprinting
Authors: Kamins T. I. , Ohlberg D. A. A. , Williams R. Stanley , Zhang W. , Chou S. Y.
Published: July 2002

Strain energy from the lattice mismatch of a heteroepitaxial system can create “self-assembled,” single-crystal islands irregularly arranged on the surface. Alternatively, features of tens of nanometers can be patterned on a substrate by “nanoimprinting” using a mold and etching. When these two techniques are combined, the small patterned features can interact with the self-assembly process, causing the islands to form at the patterned features. The resulting regular array of very small islands may be useful for future devices. The positioning of single-crystal Ge islands by Si mesas formed by nanoimprinting and etching is demonstrated in this letter.
Lithographically induced self-construction of polymer microstructures for resistless patterning
Authors: Chou Stephen Y. , Zhuang Lei , Guo Linjie
Published: July 2002

We have discovered and developed a method that can directly pattern polymer microstructures of arbitrary shapes without using a resist, exposure, chemical development, and etching. A mask with protruded patterns is placed a distance above an initially flat polymer film cast on a substrate. During a heating cycle that raises the temperature above the polymer’s glass transition temperature and then cooled back to the room temperature, we found that the polymer was attracted to the mask protrusions on their own, forming the mesas that have a lateral dimension identical to that of the mask protrusions, a height equal to the distance between the mask and the substrate, and a relatively steep sidewall. The method, termed lithographically induced self-construction, is important to the fabrication of polymer electronic and optoelectronic devices.
Red organic light-emitting diodes using an emitting assist dopant
Authors: Hamada Yuji , Kanno Hiroshi , Tsujioka Tsuyoshi , Takahashi Hisakazu , Usuki Tatsuro
Published: July 2002

We propose an emitting assist (EA) dopant system for obtaining organic light-emitting diodes (OLEDs) with pure red emission. The EA dopant (rubrene) did not itself emit but assisted the energy transfer from the host (Alq3) to the red emitting dopant (DCM2). The cell structure used was {indium tin oxide/hole injection layer [(20 nm), CuPc/hole transport layer (50 nm), NPB/emitting layer (40 nm), Alq3+DCM2 (2%)+rubrene (5 wt %)]/MgIn}. (CuPc: Copper (II) phthalocyanine, NPB: N, N′-Di(naphthalen-1-yl)-N, N′-diphenyl-benzidine, DCM2: 4-Dicyanomethylene- 2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-8-yl)vinyl]-4H-pyran). A stable red emission (chromaticity coordinates: x=0.64, y=0.36) was obtained in this cell within the luminance range of 100–4000 cd/m2. When the cell was not doped with rubrene, the emission color changed from red to orange as the luminance increased. The EA dopant system is a promising method for obtaining red OLEDs.
Photoinduced surface relief gratings on azopolymer films: Analysis by a fluid mechanics model
Authors: Sumaru K. , Yamanaka T. , Fukuda T. , Matsuda H.
Published: July 2002

Photoinduced surface relief grating (SRG) formation on azopolymer films is discussed precisely using a fluid mechanics model which takes depth dependence of photoinduced driving force and velocity distribution in the film surface into account. Formulation for the SRG dynamics is derived analytically as a function of film thickness and interference wave number. The film thickness dependence of diffraction efficiency, which is observed experimentally, agrees well with the theoretical value in the entire range of film thickness. The dependence of SRG driving force on interference wave number is also discussed in terms of the experimental data using proposed model.
Time-resolved photoluminescence spectra of strong visible light-emitting SiC nanocrystalline films on Si deposited by electron-cyclotron-resonance chemical-vapor deposition
Authors: Xu S. J. , Yu M. B. , Rusli  , Yoon S. F. , Che C. M.
Published: July 2002

SiC nanocrystalline films on Si substrates deposited using advanced electron-cyclotron-resonance chemical-vapor deposition exhibit intense visible light emission at room temperature under laser excitation. Continuous-wave and time-resolved photoluminescence measurements for these SiC films were carried out at room temperature. The photon energy of the dominant emission peaks is higher than the band gap of cubic SiC. Room-temperature optical absorption measurements show a clear blueshift of the band gap of the samples with a decrease of the average size of the nanoclusters, indicating an expected quantum-confinement effect. However, the emission spectra are basically independent of the size. Temporal evolution of the dominant emissions exhibits double-exponential decay processes. Two distinct decay times of ∼200 ps and ∼1 ns were identified, which are at least two orders of magnitude faster than that of the bound-exciton transitions in bulk 3C–SiC at low temperature. Strong light emissions and short decay times strongly suggest that the radiative recombinations may be from some direct transitions such as self-trapped excitons on the surface of the nanoclusters.