bluuebunny/crossref_metadata_2025 huggingface dataset:
OTEX, an androgen-regulated human member of the paired-like class of homeobox genes
Authors: GESERICK Christoph , WEISS Bertram , SCHLEUNING Wolf-Dieter , HAENDLER Bernard
Published: July 2002

paired genes emerged early in evolution and code for homeobox transcription factors, having fundamental roles in various biological processes. We identified a novel human member of the paired-like class, which we named OTEX. A phylogenetic analysis revealed that OTEX belonged to the recently defined PEPP subfamily of paired-like homeobox genes. It was organized into three introns and, like the other PEPP genes, it was mapped to chromosome X. Its transcripts were detected mainly in the ovary, testis and epididymis, but also in the prostate and mammary gland. In the PC-3/ARwt prostate cell line, OTEX expression was stimulated dramatically following androgen treatment. Immunofluorescence studies revealed an exclusively nuclear localization of the OTEX protein. Mutation of the RARCRRHQRE amino acid sequence present at the C-terminus of the OTEX homeodomain resulted in a mainly cytoplasmic localization, indicating that this motif harboured the nuclear localization signal. No inherent transactivation function was seen for OTEX using the one-hybrid assay, and no homodimer formation was observed in the two-hybrid assay, suggesting that additional partners were needed for this activity. Taken together, the data show that OTEX represents a novel, androgen-regulated, paired-like homeobox protein, with possibly an important role in human reproduction.
Endothelial cell prostacyclin synthesis induced by lymphocytes is independent of the membrane fatty acid composition of both cell types and of E‐selectin, VCAM‐1 or ICAM‐1‐mediated adhesion
Authors: Dominguez Zury , Merhi‐Soussi Faten , Macovschi Olga , Némoz Georges , Lagarde Michel , Prigent Annie‐France
Published: July 2002

Prostacyclin (PGI2), the main prostanoid in most vascular tissues regulates haemostasis and vascular tone, as well as the proliferation of smooth muscle cells. We have previously reported that lymphocyte contact with endothelium enhances endothelial cell PGI2 output. Here, we demonstrate the specificity of lymphocytes for switching on this response. Co‐incubation of human umbilical vein endothelial cells (HUVEC) in serum‐free medium with allogeneic peripheral blood lymphocytes (PBL), at a PBL:HUVEC ratio of 9:1, enhanced the basal (HUVEC alone) PGI2 output by 2·5‐fold under static conditions, and was not altered in conditions mimicking shear stress. It occurred without previous activation of either cell type and was dependent upon specific interactions with PBL. Indeed, the PGI2 output induced by the co‐incubation with resting neutrophils, non‐activated platelets or latex beads was significantly lower than that induced by PBL. Blocking endothelial cell adhesion molecules (ECAM) E‐selectin, vascular cell adhesion molecule‐1 (VCAM‐1) or intracellular adhesion molecule‐1(ICAM‐1) did not modify the PBL‐induced PGI2 output, although 51Cr‐labelled PBL adhesion was significantly decreased with anti‐ICAM‐1 antibody. Changes in the fatty acid composition of membrane phospholipids induced by incubation with eicosapentaenoic (EPA) or docosahexaenoic acids (DHA) resulted in diminished basal PGI2 output and adhesion of 51Cr‐labelled PBL, whereas the PBL‐stimulated PGI2 output was not modified. This specific cell–cell interaction represents a new stimulus for PGI2 synthesis that does not primarily involve the ECAM pathway, is independent of cell membrane fatty acid composition and shear stress. This switch‐on for PGI2 synthesis, which is induced by lymphocytes, might serve as a protection against atherogenesis.
Comparative methodological analysis of erbB‐2/HER‐2 gene dosage, chromosomal copy number and protein overexpression in breast carcinoma tissues for diagnostic use
Authors: Bánkfalvi À , Simon R , Brandt B , Bürger H , Vollmer I , Dockhorn‐Dworniczak B , Lellé R‐J , Boecker W
Published: July 2002

Aims

: This study was performed to test the validity of different methods for determining the status of the erbB‐2/HER‐2 oncogene in breast cancer tissues for diagnostic use.

Methods and results

: Forty formalin‐fixed, paraffin‐embedded breast carcinomas were investigated by fluorescence in situ and comparative genomic hybridization (FISH, CGH) as well as by immunohistochemistry (IHC) using Dako‐HercepTestTM and CB11 antibody (Ventana). Additionally, competitive‐differential polymerase chain reaction (cdPCR) was performed on frozen samples to estimate gene dosage alterations of erbB‐2/HER‐2. Amplification was detected in 12–23% and protein overexpression in 16–68% of the cases, depending on the methodology and/or the reagent used. Perfect concordance (100%) was found between the results of cdPCR and CB11‐IHC, and a 97% concordance between FISH and CB11‐IHC. The concordance between Dako‐HercepTestTM and CB11‐IHC was 78%; seven of eight 2 + carcinomas with the Dako‐HercepTestTM were classified as nonamplified using FISH.

Conclusions

: Our results indicate that high‐level expression as well as normal erbB‐2/HER‐2 status of breast carcinomas can be detected reliably both by IHC and gene dosage assessment in paraffin material for diagnostic use. However, borderline results, especially those with 2 + immunopositivity, should be interpreted with caution and increased emphasis should be given to other clinical and prognostic information available.
Testing for glaucoma with the frequency‐doubling illusion in the whole, macular and eccentric visual fields
Authors: Maddess T , Severt W L
Published: July 2002

Purpose: The frequency doubling (FD) illusion is the basis for new diagnostic methods for glaucoma. The FD illusion is seen when low spatial frequency grating patterns are contrast modulated at high rates. The present experiments examined which spatial frequencies might be optimal and whether high flicker rates are required.

Methods: We determined contrast thresholds for the following: W1, a wide‐field 0.25 c/deg grating at 27 Hz contrast reversal; W2, as W1 but no flicker; MAC, 27 Hz, 4 c/deg grating presented to the central 4°; and E1 to E7, seven spatial frequencies in the range 0.063–0.813 c/deg, 27 Hz, presented in a 5° aperture at 15° (nasal) eccentricity.

Results: W1 was the best predictor of glaucoma. Of the eccentrically presented stimuli, E6 (0.688 c/deg) was the best predictor of glaucoma while the lower spatial frequencies performed less well. Only MAC was significantly age‐dependent.
Mechanism of octreotide in acute necrotizing pancreatitis (ANP) of rats: An experimental study
Authors: Xiao Yu , Shengdao Zhang , Ruoqing Lei , Zongqin Xia , Tianquan Han , Yaoqing Tang , Sheng Chen , Jiancheng Wang , Zurong Yuan
Published: July 2002

OBJECTIVE: To study the action of octreotide in acute necrotizing pancreatitis (ANP) in rats.

METHODS: The effect of octreotide on pancreatic acinar cells with respect to amino acid uptake, protein synthesis and secretion of enzymes was observed by using radioactive tracing and autoradiography on both healthy rats and rats with ANP.

RESULTS: It was shown that octreotide has no effect on pancreatic acinar cells with respect to amino acid uptake and protein synthesis in both ANP and in control rats. However, octreotide was able to inhibit the secretion of enzyme‐proteins. There were secretions from the basolateral membrane of the acinar cells in ANP rats, which could be reduced by treatment with octreotide.

CONCLUSIONS: Octreotide has no effect on pancreatic acinar cells with respect to amino acid uptake and enzyme‐protein synthesis, but it can inhibit the secretion of enzyme‐proteins, in particular, from the basolateral membrane of ANP rats and prevent the accumulation of zymogen granules in the interstitium.
Inhibitory effect of a liposome‐mediated antisense oligodeoxynucleotide on telomerase activity in a human gastric cancer cell line
Authors: Zhihui Lin , Houyu Liu , Xiuzhen Pan
Published: July 2002

OBJECTIVE: To investigate the effect of a specific antisense oligodeoxynucleotide (ASODN) on the telomerase activity of the human gastric cancer cell line FGC85.

METHODS: FGC85 cells were treated in vitro with ASODN complementary to the template region of the RNA component of human telomerase. A cationic liposomal transfection reagent was used as a delivery vector. Telomerase activity was detected by using the telomeric repeat amplification protocol/polymerase chain reaction/enzyme‐linked immunosorbent assay (TRAP‐PCR‐ELISA) method.

RESULTS: The telomerase activity of FGC85 cells was suppressed significantly by the liposome/ASODN treatment and the effect was related to the con‐centration of liposome/ASODN and treatment time.

CONCLUSIONS: Specific ASODN have an inhibitory effect on telomerase activity in human gastric cancer cell line FGC85. Specific ASODN could be used in research into gene therapy for cancer treatments and the exploration of carcinogenesis.
Clinical application of computed tomography virtual colography
Authors: Xu Sun , Wei Lu , Dianhui Zhao , Daoying Gen , Tianzhen Shen , Xingrong Chen
Published: July 2002

OBJECTIVE: To investigate the computed tomography (CT) virtual colographic features of colonic polyps, colorectal cancer, diverticula, ulcerative colitis and other benign colonic lesions. Also, to assess the value of this method in the diagnosis of colorectal lesions.

METHODS: Computed tomography colography was performed in 37 patients (26 male, 11 female) suffering from the following conditions: 20 colonic adenomas, six colon cancers, four diverticula, five ulcerative colitis and one each of melanosis coli and amyloidosis. The data from CT scanning were processed by computer with specific software and the colonic lesions were evaluated with 2‐ or 3‐D images, depending on the individual software.

RESULTS: Seventeen cases of colonic adenoma, six colon cancers, four diverticula and two cases of ulcerative colitis were detected by using CT colography. However, melanosis coli and amyloidosis of the colon were not detected.

CONCLUSION: Computed tomography colography can detect all colonic polyps of 0.5 cm in diameter or larger, colon cancer, diverticula and some ulcerative colitis successfully. It is quick, minimally invasive and able to be tolerated well. It has the potential to become an effective radiological tool in diagnosing colonic lesions.
Mechanism of metronidazole resistance in Helicobacter pylori
Authors: Kui Jiang , Jianzhong Zhang , Guozong Pan
Published: July 2002

OBJECTIVE: Drug resistance to Helicobacter pylori is one of the most important reasons for the failure of anti‐H. pylori treatment. Metronidazole is a preferred drug for the elimination of H. pylori. However, using this drug alone can easily lead to resistance. The aim of the present study was to investigate the mechanism of metronidazole resistance in H. pylori.

METHODS: International standard strain NCTC11639 was used. For the nitrate reduction test, four strains were used as positive controls, two strains of Bacillus coli and two strains of Vibrio cholerae. Metronidazole was used as tablets (0.2 g per tablet). The following techniques were used: (i) metronidazole used to apply selective pressure; (ii) sodium dodecylsulfate–polyacrylamide gel electrophoresis (SDS‐PAGE); (iii) nitrate reduction test; and (iv) test to detect the enzyme activities associated with 95 different substrates for Gram‐negative bacteria.

RESULTS: As a result of the selective pressure of metronidazole, 20 H. pylori colonies survived; the bacteriostatic zones of these colonies were 0 mm in diameter, whereas the original NCTC11639 bacteriostatic zones were 25 mm in diameter. There was no significant difference seen among the 18 strains of drug‐resistant H. pylori and the original NCTC11639 strain protein electrophoresis strips. In the nitrate reduction test, both sensitive and resistant H. pylori all tested negative and the control strains of Bacillus coli and Vibrio cholerae tested positive. After the mutation of H. pylori from sensitive to resistant, the activities of enzymes associated with mono‐methyl succinate, succinic acid and D‐alanine metabolism were decreased, and those associated with L‐fucose and 6‐phosphate glucose metabolism were increased.

CONCLUSIONS: The resistance of H. pylori to metronidazole is not related to nitroreductase. There may be no obvious changes in membrane protein in the drug‐resistant strain. The metronidazole resistance of H. pylori is associated with its metabolism and a change in enzyme activities.
Troglitazone reduces plasma levels of tumour necrosis factor‐α in obese patients with type 2 diabetes
Authors: Katsuki A. , Sumida Y. , Murata K. , Furuta M. , Araki‐Sasaki R. , Tsuchihashi K. , Hori Y. , Yano Y. , Gabazza E. C. , Adachi Y.
Published: July 2002

We evaluated the effect of troglitazone (given orally 400 mg/day) on glucose intolerance and on the plasma levels of tumour necrosis factor‐α (TNF‐α) in 12 obese patients with type 2 diabetes for 12 weeks. Troglitazone significantly decreased fasting plasma glucose, serum C‐peptide, serum insulin and HbA1c levels. Plasma levels of TNF‐α were significantly reduced by troglitazone administered for 8 and 12 weeks. Troglitazone administration significantly improved insulin resistance, but did not affect pancreatic β‐cell function as evaluated by the homeostasis model assessment (HOMA). In the present study, we reported for the first time that troglitazone administration significantly reduces plasma levels of TNF‐α in obese patients with type 2 diabetes.
Local dioptric power matrix in a progressive addition lens
Authors: Alonso José , Gómez‐Pedrero José A. , Bernabeu Eusebio
Published: July 2002

In this paper we use the formalism of the Dioptric Power Matrix to visualise and characterise the properties of a Progressive Addition Lens. For progressive addition lenses, the dioptric power matrix is point‐dependent, and we have measured its elements over the lens surface by means of an automatic focimeter. We show the obtained contour plots corresponding to the matrix elements, and we compare them with the traditional sphere and cylinder graphs. Although the two representations give the same information, the advantages and disadvantages between them are analysed. The dioptric power matrix method turns out to be specially useful for the computation of prismatic effects along the lens surface.
Breeding Birds as a Farm Product
Authors: Musters C. J. M. , Kruk M. , De Graaf H. J. , Keurs W. J. Ter
Published: July 2002

Abstract: Since the 1950s, meadowbird populations have been under increasing threat from radical changes in farming practices. We studied the possibilities for conserving meadowbirds on modern, intensive dairy farms in the Netherlands. Here, the conventional strategy for the conservation of meadowbirds is to restrict farming intensity and compensate farmers for their production losses. To increase the breeding success of meadowbirds, however, dairy farmers can fine‐tune farming practices to yearly and local circumstances. Because this fine‐tuning is difficult to enforce by legislation, we propose that farmers be paid for clutches bred on their land. Thus, farmers are paid for what they produce, but not restricted in their farming practices. The results of the first small‐scale experiments, in which breeding success was compared between farms where farmers were paid for meadowbird clutches and farms where farmers were not paid, are encouraging. Breeding success of meadowbirds was significantly higher where farmers were paid than where they were not ( breeding success of Lapwing [  Vanellus vanellus]: 64.7% on paid farms, 48.2% on unpaid farms; Black‐tailed Godwit [  Limosa limosa]: 63.1% paid, 39.3% unpaid). The effects on meadowbird populations could not yet be detected. The per‐clutch payment system is less expensive than compensation for income losses: paying for clutches costs 40 Euro per clutch, whereas compensating for income losses costs 100–400 Euro per clutch (1 Euro is approximately equal to 1 U.S. dollar). Farmers are enthusiastic, and the system encourages cooperation between farmers and nature conservationists.
Causes of Fruit Set Variation in Polygonatum odoratum (Liliaceae)
Authors: Guitián J. , Guitián P. , Medrano M.
Published: July 2002

Abstract: In Polygonatum odoratum (Liliaceae), flowers located distally within the flowering shoot typically exhibit lower fruit set than flowers located proximally. In this study, experiments were performed to investigate whether the lower fruit set of distal flowers is due to pollen limitation, resource competition or “architectural” effects. We found that (1) fruit set and mean number of ovules per flower decline within the flowering shoot from proximal to distal position; (2) variations in the amount of pollen received do not explain the observed differences in fruit set; (3) the fruit set of the most distal flowers was significantly increased by removal of other flower buds in the flowering shoot just before flower opening, indicating that fruit set in these flowers is resource‐limited; and (4) removal of proximal flowers increased the fruit set of later flowers to levels similar to those of early flowers of control shoots, arguing against the architectural effects hypothesis.
Band offset in elastically strained InGaAs/GaAs multiple quantum wells determined by optical absorption and electronic Raman scattering
Authors: Reithmaier J.-P. , Höger R. , Riechert H. , Heberle A. , Abstreiter G. , Weimann G.
Published: July 2002

Pseudomorphic InGaAs/GaAs multiple quantum well structures with In contents ranging from 18 to 25% were grown by molecular beam epitaxy and investigated by optical absorption, photoluminescence, and electronic Raman scattering. Sharp exciton peaks with linewidths of ∼3 meV for the first electron to heavy hole transition are observed in the absorption spectra. The electron subband structure was investigated independently by electronic Raman scattering. The transition energies are analyzed using a four-band effective mass Schrödinger equation taking strain into account. A conduction-band offset ratio ΔEc/ΔEg=0.6 is found for all samples independent of In content.
Measurement of AlGaAs/AlGaAs interface recombination velocities using time-resolved photoluminescence
Authors: Timmons M. L. , Colpitts T. S. , Venkatasubramanian R. , Keyes B. M. , Dunlavy D. J. , Ahrenkiel R. K.
Published: July 2002

Time-resolved photoluminescence has been used to examine AlxGa1−xAs/AlyGa1−yAs interfaces, focusing on the recombination velocity. For an Al0.08Ga0.92As/Al0.88Ga0.12As interface, important for solar cells, recombination velocities are about 104 cm/s with the growth conditions used in this study. Several types of interface passivation were attempted, but the most successful was the insertion of thin Al0.14Ga0.86As layers between the other two alloys. Using this technique, a 16-fold increase (to ∼20 ns) of the minority-carrier lifetime was measured in a 0.8-μm-thick Al0.08Ga0.92As layer in which interface recombination would normally have limited the lifetime to about 1–2 ns. Compositional grading was found to be ineffective at passivating the interfaces.
Epitaxial PtFe(001) thin films on MgO(001) with perpendicular magnetic anisotropy
Authors: Lairson B. M. , Visokay M. R. , Sinclair R. , Clemens B. M.
Published: July 2002

We report a technique for producing the ordered PtFe intermetallic compound with perpendicular magnetic anisotropy and a preferred c-axis orientation perpendicular to the film plane. PtFe alloys possess high magneto-optic Kerr rotations and magnetizations, suggesting them as likely candidates for magneto-optic and perpendicular magnetic recording.
InP on Si(111): Accommodation of lattice mismatch and structural properties
Authors: Krost A. , Heinrichsdorff F. , Bimberg D. , Cerva H.
Published: July 2002

The growth of InP by low-pressure metalorganic chemical vapor deposition on vicinal Si(111), misoriented 3° towards [1̄1̄2], is reported. By double crystal x-ray diffraction an order of magnitude improvement in structural quality is measured as compared to InP on Si(001). From high resolution electron microscopy near the interface a heavily twinned region of 25 nm in thickness is found with microtwins having their twin planes parallel to the Si(111) surface. In this region the 8% misfit between InP and Si is completely accommodated in one dimension by partial dislocations having Burgers vectors a/6〈112〉 (Schockley partial dislocations) in the (111) surface plane which are associated with the formation of the thin twinned region close to the interface. Above this zone the crystallographic orientations of the InP are identical to those of the Si substrate.
Millimeter-wave detection of free radicals using pulsed laser photolysis
Authors: Kolbe W. F. , Leskovar B.
Published: July 2002

The application of millimeter-wave microwave spectroscopy to the detection of free radicals and other species generated by pulsed excimer laser photolysis is described. To detect the radical species, a newly developed 140-GHz microwave spectrometer employing a high-Q Fabry–Perot cavity was used. The technique is illustrated by the observation of SO and CS radicals produced by photodissociation at 193 nm of SO2 and CS2, respectively. SO absorption signals from the ground vibrational state transition at 138.17 GHz and the first and second excited vibrational state transitions at 137.28 and 136.45 GHz were measured. CS was detected in several excited vibrational states up to ν=4. Finally, as an example of the application of the technique to chemical kinetic studies, the reaction rate of SO with NO2 was determined. The measured rate coefficient at 298 K of (1.46±0.12)×10−11 cm3 molecule−1 s−1 is in excellent agreement with values reported in other studies. Millimeter-wave spectroscopy is shown to be a sensitive and highly specific probe for the detection of short lived species in gas phase chemical kinetic studies.
Technique for visualization and analysis of mural thrombogenesis
Authors: Hubbell Jeffrey A. , McIntire Larry V.
Published: July 2002

Epi-fluorescence video microscopy, digital image processing, and photodiode measurements were used to visualize and analyze mural thrombogenesis, the initial stages of blood platelet adhesion to and aggregation on a surface. This technique permitted real-time visualization, high-resolution, quantitative, off-line measurement of the growth of individual thrombi and high-resolution, quantitative, end-point measurement of the accumulation of platelets as a function of position on the surface.
DENSEPACK: An array of Langmuir probes in the limiter shadow plasma of the Alcator C tokamak fusion experiment
Authors: LaBombard B. , Lipschultz B.
Published: July 2002

The boundary plasma of the Alcator C tokamak exhibits poloidal asymmetries in plasma parameters. In order to investigate this phenomenon, an array of 80 closely spaced Langmuir probes has been built to directly sample this plasma region. This specially developed, densely packed probe array (DENSEPACK) is unique in that it provides a simultaneous, time-dependent, two-dimensional mapping (minor radius r, poloidal angle θ) of plasma density, electron temperature, and floating potential over nearly the full 360° poloidal extent of the boundary plasma in this circular cross-section tokamak. The construction and operation of the DENSEPACK probe array, as well as support hardware and software systems needed to handle the large volume of data generated by this array, are described in this paper.
Application of capacitor insertion method to scanning tunneling microscopes
Authors: Kaizuka Hiroshi
Published: July 2002

The capacitor insertion method to compensate for hysteresis and creep in piezoelectric actuators is applied to scanning tunneling microscopes. By inserting a capacitor in series with the piezoelectric actuator, hysteresis and creep can be greatly reduced or eliminated. After the principle of the method is reviewed, a structure of a scanning tunneling microscope used here is described. A calibration grid for scanning electron microscopes (2000 lines/mm) can be imaged with greatly reduced distortion by inserting capacitors in series with the piezoelectric actuators, which consist of an x-y-z scanner of the microscope. Furthermore the method can be used to reduce the sensitivity of the x-y-z movements of the scanner because an applied voltage is divided between an inserted capacitor and a piezoelectric actuator. Hence, using suitably small capacitors, atomic-scale images of Kish-graphite can be easily obtained with the same microscope.
Anomalous charge state distribution in ECRIS for oxygen isotopes
Authors: Drentje A. G.
Published: July 2002

The performance of the KVI ECRIS-2 for a mixture of 18O, 17O, and 16O isotopes is−as expected−very much the same as for natural oxygen gas, i.e., the sum of the currents of given charge states of the isotopes equals that of the same charge state of the natural oxygen. However, it is found that the ratios of currents 18Oq+/17Oq+ and 18Oq+/16Oq+ increase with q. New measurements on ECRIS-1 (Minimafios) at KVI confirm this anomalous charge state distribution. This effect is also present when nitrogen or argon gas is mixed into the plasma. However, when applying helium as a mixing gas, the anomaly disappears. An explanation in terms of ion cooling (here transfer of kinetic energy to, in particular, the light species) seems valid.
Long-pulse analog integration
Authors: Ali-Arshad S. , de Kock L.
Published: July 2002

The presence of variable offsets at the input stage of analog integrators produces drifts in the output which limit the duration for which integration can be carried out at specified accuracy. In this article an integration system is demonstrated, accurate to within a few millivoltseconds over a time scale of several hours, with no special temperature control of the environment. The principle is to alternate between two individual integrators. While one integrates the signal, the other performs a drift measurement. This provides information sufficient to construct a continuous integral, and to perform time-dependent drift compensation. Estimates are given to show that the scheme could meet the magnetic diagnostic requirements of the next generation long-pulse devices for the magnetic confinement of thermonuclear plasmas. Modifications to the system tested are suggested, which could significantly further extend the period of accurate integration.
Sources of error in a laser rangefinder
Authors: Hashemi K. S. , Hurst P. T. , Oliver J. N.
Published: July 2002

We describe sources of error in a breadboard, low-cost, time-of-flight laser rangefinder. The rangefinder deduces the range of a retroreflecting target by directing an intensity-modulated laser beam at the target and measuring the phase difference between the returned and transmitted modulation envelopes. The phase measurement is performed by a combination of heterodyning and digital signal processing. We present an equation for the standard deviation of statistical errors generated by quantization in the digital signal processing. We show how both electrical crosstalk and stray light give rise to errors which are cyclic with target range, and we describe how these errors can be reduced. We demonstrate the importance of errors caused by the dependence of the photodiode’s propagation delay upon the intensity and placement of the light spot incident upon its surface, and discuss how the instrument’s optical components can be arranged to minimize such errors. Finally, we show that our rangefinder, using a modulation frequency of 140 MHz, has rms nonlinearity less than 85 μm.
Radio frequency phase shifting at the source simplifies NMR spectrometer design
Authors: Sternin E.
Published: July 2002

Two different approaches to the digital control of the phase of the radio frequency (rf) signal are reviewed. Given a fast reproducible digital phase control, a method is presented for performing digitally some of the traditionally analog spectrometer functions. As a result, the spectrometer design is simplified considerably. Selection of different phase settings during the transmission of the rf pulse and during signal detection and other digital operations are discussed as examples.
2-D FIR interferometry and polarimetry on TPX
Authors: Geck W. R. , Qin X. , Liao J. , Domier C. W. , Luhmann N. C.
Published: July 2002

A multiple fan-beam approach to 2-D FIR interferometry and polarimetry is under investigation for use on next generation tokamaks such as TPX. The approach utilizes a small number (3–5) of inside launch fan beams, and a finite number (5–15) of receive horns positioned within the vacuum vessel on the outboard side of the plasma. Positioning of the horns is achieved with minimal penetration of internal structures, within the design constraints dictated by a highly restricted viewing access. The choice of operating frequency is discussed considering both physics and design issues.
Study of the feasibility of self focusing of a relativistic electron beam in an electron beam ion source/trap
Authors: Mücke M. , Rao R. , Becker R. , Kleinod M.
Published: July 2002

With electron beam ion sources/traps (EBIS/T) ions with highest charge states can be produced. EBIT represents a successful device for atomic physics studies, while EBIS is also an injector to accelerate highly charged ions of every species. High performance EBIS/T usually uses a high magnetic field generated by superconducting coils to compress the electron beam, in order to obtain high electron beam current densities in the range of 102–103 A/cm2 along the ionization region. Studies on a crossover (X-) EBIS without magnetic field but using an electrostatically generated electron beam crossover have shown the production of highly charged ions like Ar18+ and Ba46+. A project was started to yield high current densities from the self pinching of a relativistic electron beam in a partially space charged compensated region. A 65 keV electron beam is produced by a high emissive cathode with the lowest possible beam emittance and is focused by magnetic lenses into the trap region, where the electronic space charge will be compensated by trapped ions. The current density produced by the crossover will be enhanced by the self pinching of the relativistic electron beam. Axial ion extraction optics and radial diagnostics in the ReXEBIST (relativistic XEBIS/T) allow both, EBIS and EBIT operation.
Simultaneous production of H− by both thermal and electron-stimulated desorptions from saline hydrides
Authors: Kawano Hiroyuki , Serizawa Naoshi , Tanaka Akihide , Wada Motoi , Sasao Mamiko , Miyake Kiyoshi
Published: July 2002

To develop a compact negative ion source for solid samples, powder (∼10 mg) of saline hydride (LiH, CaH2, or SrH2) deposited on a molybdenum ribbon (R, ∼0.1 cm2) was heated up to ∼800 K, yielding the mass-analyzed current (iT−≈10−11 A) of H− due to thermal desorption (TD) together with the current (I−≈10−3 A) of thermal electron (e−). After the “activation” at ∼800 K, the work function (φ) of a SrH2/Mo system, e.g., was 7.3±0.3 eV, while the desorption energy (E−) of H− due to TD was 9.7±0.4 eV. The value of E−−φ=2.4±0.2 eV, thus determined agreed fairly with that (2.34 eV) evaluated thermochemically from our simple model. The sample vapor and e− originating from the hydride continually condensed onto and impacted against, respectively, the ion-extraction slit plate mounted above R, thereby giving the current (iE−) of H− due to electron-stimulated desorption (ESD). In the case of SrH2 at 760 K, iE− was ∼30× as large as iT−. Our dual ion source yielded stable currents of H− due to TD and ESD.
Study of microwave coupling in electron cyclotron resonance ion sources and microwave ion sources
Authors: Celona L. , Ciavola G. , Gammino S.
Published: July 2002

At the “Laboratorio Nazionale del Sud” two different ion sources are under development: SERSE (a superconducting electron cyclotron resonance ion source to be coupled to the superconducting cyclotron) and MIDAS (a microwave discharge ion source for recoils ionization). In most cases, for these kinds of sources, the coupling system remains empirical, and the exact description of the waves absorbed from the plasma is poorly known. In the following paper an analysis of power transfer characteristics between an arbitrary power source and load impedances is presented. Particular attention is paid to the matching systems. Herein is presented a 2.45 Ghz microwave line for the MIDAS ion source and a proposal for a matching system that can be used in SERSE when it will be driven by three frequencies: 10, 14, and 18 Ghz.
A microcontroller-based system for piezoscanner nonlinearity correction: Atomic force microscope
Authors: Cidade Geraldo Antônio Guerrera , Weissmüller Gilberto , Bisch Paulo Mascarello
Published: July 2002

Scanning probe microscopes use piezoelectric actuators (piezoscanners) as extremely sensitive and exact positioners for small scaled sample scannings. They are capable of making fine movements along the X, Y, and Z axes, with displacements that can vary from several hundreds of angstroms to some micrometers. For high amplitude sweeps, the displacement response results in visible distortions due to the intrinsic nonlinearity effects of the piezoelectric tube. This work proposes the nonlinearity correction by means of a microcontroller-based system which produces (in real time) the correction values using the piezoscanner quadratic transfer function, adapted to an atomic force microscope (AFM) of its own construction. The AFM is intended to be used with biological samples. Other correction methods are described.
Selection of the powdery metal hydride best for producing H− by thermal desorption
Authors: Kawano H. , Tanaka A. , Sugimoto S. , Iseki T. , Zhu Y. , Wada M. , Sasao M.
Published: July 2002

To find the metal hydride best for producing H− by thermal desorption, the desorption rates of H−, H2 and electron (e−) directly emitted from a powdery sample (∼1 mg) of NaH, LiH, MgH2, CaH2, SrH2, TiH2, ZrH2, KBH4, LiAlH4, or NaAlH4 heated up to ∼1000 K were determined simultaneously with a special system. Theoretical analysis of the experimental data thus achieved yields the following results. (1) Both H− and e− are emitted from those active spots (mainly consisting of alkali or alkali earth metal) created by thermal decomposition (e.g., LiH→Li+H2/2). (2) The active spots are readily destroyed and reconstructed by admission of H2 and by stopping the admission, respectively. (3) The work function (φ) of activated NaH is very low (∼2 eV), but NaH is rapidly depleted owing to its thermal instability. (4) Among the ten hydrides, CaH2 is concluded to be the best as a source material for thermal desorption of H− because activated CaH2 (φ≃5 eV) is most stable and strongest in H− (∼10−12 A or 10−10 A/cm2 after mass analysis) around 900 K.
Relation between vapor Cs and adsorbed Cs in H− ion source
Authors: Ogasawara M. , Morishita T. , Hatayama A.
Published: July 2002

The relation between gaseous Cs density and the coverage of Cs on the plasma grid surface is determined in the existence of the effect of Cs deposit on the cold surface. An equation for the deposit of Cs on the cold surface in the ion source is obtained by considering the saturation of the deposit. The Cs coverage is expressed as a function of gaseous Cs density in the volume of the ion source by considering the relation τθ≪τa, where τθ is the time scale of the Cs adsorption to the plasma grid surface and τa is that of the Cs adsorption to the cold surface. The coverage varies with the slow time scale through the variation of the gaseous density related to the deposit of Cs on the cold surface.
Properties of iodine laser-produced stream of multiply charged heavy ions of different elements
Authors: Láska L. , Krása J. , Mašek K. , Pfeifer M. , Rohlena K. , Králiková B. , Skála J. , Woryna E. , Parys P. , Wolowski J. , Mróz W. , Sharkov B. , Haseroth H.
Published: July 2002

Properties of laser produced stream of ions of high- and medium-Z elements were analyzed in the far expansion zone using time-of-flight method and Thomson parabola spectrograph in experiments performed with the iodine laser system PERUN at IP ASCR, Prague (λ=1.315 μm, EL∼45 J,τL∼300–700 μs). Ta, Au, and Pb, as well as Co, Sn, and Ag were mainly used as targets onto which a laser power density up to 1×1015 W cm−2 was delivered. Attention is paid to the evolution and comparison of different produced ion groups, and to the number, charge state, energy, and angular distribution of emitted ions.
Theoretical study of short electrostatic lens for the Columbia ion microprobe
Authors: Dymnikov Alexander D. , Brenner David J. , Johnson Gary , Randers-Pehrson Gerhard
Published: July 2002

A short probe-forming system is developed for the Columbia Microprobe that includes four electrostatic quadrupoles with a Russian quadruplet configuration. The smallest beam spot size and appropriate optimal parameters of the probe-forming systems have been found. These parameters of the system are compared with appropriate parameters of other field configurations including the electrostatic and magnetic fields with dipole, quadrupole, and rotational symmetry. The new original construction of the electrostatic quadruplet has been manufactured. The sensitivity of this quadruplet to some misalignments of the construction is investigated.
Simultaneous, noninvasive measurements of convective heat transfer and solid volume fraction at the wall of an entrained gas–solid suspension
Authors: Griffith A. Elizabeth , Louge Michel , Mohd-Yusof Jamaludin
Published: July 2002

We describe an instrument for local, instantaneous, noninvasive, simultaneous measurements of solid volume fraction and convective heat transfer at the wall of a vertical tube containing a relatively dense, entrained suspension of gas and fine solids. The instrument combines a small platinum coil and a guarded capacitance sensor. The capacitance sensor records instantaneous solid volume fraction in the near vicinity of the wall. The coil is maintained at constant temperature by a rapid anemometer bridge circuit. The vessel is wrapped in electric heaters to avoid artificially high rates associated with developing heat transfer and to minimize conduction losses from the coil. Using a model capturing these losses, convective heat transfer rates are inferred from the power input to the coil. The instrument is tested in a cold circulating fluidized bed riser. The temporal response of the thermal sensor is faster than 30 ms.
Synthesis of GaAs nanoparticles by digital radio frequency sputtering
Authors: Hirasawa M. , Ichikawa N. , Egashira Y. , Honma I. , Komiyama H.
Published: July 2002

Nanometer-sized GaAs particles embedded in SiO2 were prepared by a digital rf-sputtering method, where GaAs and SiO2 targets were alternately sputtered in an Ar atmosphere. The GaAs deposition time was kept shorter than the time required to form a continuous layer. Transmission electron microscopy observations showed that the sizes of the GaAs particles can be controlled from 2 to 8 nm by changing the sputtering cycle time of the GaAs target. In spite of their small size, the GaAs particles have crystallinity similar to the target material without substrate heating or postannealing. The optical absorption spectra of the GaAs particles show a blue shift as large as 1.6 eV, corresponding to strong quantum confinement of electrons and holes.
Experimental determination of a time–temperature-transformation diagram of the undercooled Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 alloy using the containerless electrostatic levitation processing technique
Authors: Kim Y. J. , Busch R. , Johnson W. L. , Rulison A. J. , Rhim W. K.
Published: July 2002

High temperature high vacuum electrostatic levitation was used to determine the complete time–temperature–transformation (TTT) diagram of the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass forming alloy in the undercooled liquid state. This is the first report of experimental data on the crystallization kinetics of a metallic system covering the entire temperature range of the undercooled melt down to the glass transition temperature. The measured TTT diagram exhibits the expected ‘‘C’’ shape. Existing models that assume polymorphic crystallization cannot satisfactorily explain the experimentally obtained TTT diagram. This originates from the complex crystallization mechanisms that occur in this bulk glass-forming system, involving large composition fluctuations prior to crystallization as well as phase separation in the undercooled liquid state below 800 K.
Integration of nonlinear optical polymer waveguides with InGaAs p-i-n photodiodes
Authors: Cites Jeffrey S. , Ashley Paul R. , Leavitt Richard P.
Published: July 2002

Performance requirements for systems employing optical guided wave components may be satisfied more easily through the hybrid integration of nonlinear optical (NLO) polymers and semiconductors. Reported in this letter, is the integration of NLO polymer waveguides with InGaAs p-i-n photodetectors at 1.3 μm, with coupling efficiencies greater than 99% and system responsivities of 0.84 A/W. An analysis of the structure using a two-dimensional beam propagation model was performed. Planarization was maintained and the design allows for further integration of optoelectronic components.
Synthesis of ultrafine gallium nitride powder by the direct current arc plasma method
Authors: Li H. D. , Yang H. B. , Yu S. , Zou G. T. , Li Y. D. , Liu S. Y. , Yang S. R.
Published: July 2002

Ultrafine gallium nitride (GaN) powder has been synthesized by the dc arc plasma method through the reaction of metal gallium (Ga) with the mixture gas of nitrogen ( N2) and ammonia ( NH3). The analyses of the produced powder by x-ray diffraction, transmission electron microscopy, and selected-area electron diffraction showed that the GaN particles in wurtzite structure consisted of nanometer-sized polycrystals and monocrystals. The conversion of Ga to GaN was determined by the mixture ratio of NH3 and N2 in the mixture gas. The morphology of the GaN particles was mainly hexagonal with the size about 20–200 nm. When heated in air or nitrogen atmosphere, the thermostablity of the GaN powder was different.
Abrupt discontinuous relationships between supercooling and melt overheating
Authors: Tong H. Y. , Shi F. G.
Published: July 2002

The dependence of the degree of supercooling (ΔT−) of melts preceding the onset of solidification on the level of melt overheating (ΔT+)above the equilibrium liquidus or melting temperature, is investigated on Sn and SnPb. We demonstrate the dependence of ΔT− on ΔT+ can be either abrupt or continuous, depending on the length of holding time. In particular, the dependence is bounded by two discontinuous limits, and the known continuous linear relationship between ΔT− and ΔT+ is only a special possibility. Our observations can be tentatively linked to the transient structural evolution of melts, and are probably general, occurring also for element Bi and SnSb. Our results may have important consequences for any thermal modeling of electronics manufacturing involving soldering operations.
Radiation hardening of pure-silica-core optical fibers: Reduction of induced absorption bands associated with self-trapped holes
Authors: Griscom David L.
Published: July 2002

Visible/near-IR-range radiation hardening of a pair of low-OH/low-Cl silica-core optical fibers has been accomplished by γ-ray preirradiation at 27 C to a dose of 13 MGy(Si) at a dose rate of 1 Gy(Si)/s in the dark. Reirradiation under identical conditions three months later demonstrated a 25-fold decrease in the initially induced intensities of the prominent radiation-induced bands centered near 660 and 760 nm and comparable decreases in weaker bands at longer and shorter wavelengths. Spectral changes observed in the wavelength regime 400–1000 nm upon quenching the irradiated fibers to 77 K have revealed the likely copresence, even at room temperature, of a previously reported “low temperature infrared absorption” which peaks near 1600 nm. Based on this insight, induced losses at 1550 nm have been extrapolated from the present data. It is argued that self-trapped holes are most likely responsible for most of the metastable induced absorption bands in the range ∼400–2000 nm.
Organic smart pixels
Authors: Dodabalapur A. , Bao Z. , Makhija A. , Laquindanum J. G. , Raju V. R. , Feng Y. , Katz H. E. , Rogers J.
Published: July 2002

The fabrication and characteristics of organic smart pixels are described. The smart pixel reported in this letter consists of a single organic thin-film field effect transistor (FET) monolithically integrated with an organic light-emitting diode. The FET active material is a regioregular polythiophene. The maximum optical power emitted by the smart pixel is about 300 nW/cm2 corresponding to a luminance of ∼2300 cd/m2.
Surface-emitting 10.1 μm quantum-cascade distributed feedback lasers
Authors: Hofstetter Daniel , Faist Jérôme , Beck Mattias , Oesterle Ursula
Published: July 2002

We present measurement results on a surface-emitting quantum-cascade distributed feedback laser emitting infrared radiation at 10.1 μm. The use of a second order grating enabled the laser to emit about 25% of its total optical power from the grating. The beam radiated from the grating was at a very low divergence angle of about 1°×14°. As already presented in a previous paper, we simplified the processing by using a lateral current injection scheme avoiding epitaxial regrowth. At 85 K, the laser emitted 210 and 60 mW of pulsed power from facet and grating, respectively; at room temperature, the corresponding numbers were 70 and 18 mW. Threshold current densities of 2.1 kA/cm2 at 85 K and 5.6 kA/cm2 at room temperature were observed. The device showed single mode behavior for the entire temperature range and all investigated power levels. In addition, a constant temperature tuning coefficient of 0.06 cm−1/K was seen.
Formation mechanism of a degenerate thin layer at the interface of a GaN/sapphire system
Authors: Xu X. L. , Beling C. D. , Fung S. , Zhao Y. W. , Sun N. F. , Sun T. N. , Zhang Q. L. , Zhan H. H. , Sun B. Q. , Wang J. N. , Ge W. K. , Wong P. C.
Published: July 2002

It has recently been suggested that the thin degenerate layer found at the GaN/sapphire interface results from a high concentration of stacking faults. The studies of this letter, however, show that this is not the most likely explanation for the presence of such a degenerate layer. Using x-ray energy-dispersive spectroscopy and secondary ion-mass spectroscopy, profile distributions of elements Ga, N, O, C, and Al, near the interface, have been obtained. The distributions reveal very high O and Al concentrations in the GaN film within 0.2 μm from the interface, together with a material depletion of Ga and N. Such conditions strongly favor n+ conductivity in this interfacial region because not only are N-vacancy and N-site O donors present, but Al incorporated on the Ga sublattice reduces the concentration of compensating Ga-vacancy acceptors. The two-layer (film plus interface) conduction has been modeled, and the effect of conduction in the GaN film thus isolated.
Self-assembled ErAs islands in GaAs for optical-heterodyne THz generation
Authors: Kadow C. , Jackson A. W. , Gossard A. C. , Matsuura S. , Blake G. A.
Published: July 2002

We report photomixer devices fabricated on a material consisting of self-assembled ErAs islands in GaAs, which is grown by molecular beam epitaxy. The devices perform comparably and provide an alternative to those made from low-temperature-grown GaAs. The photomixer’s frequency response demonstrates that the material is a photoconductor with subpicosecond response time, in agreement with time-resolved differential reflectance measurements. The material also provides the other needed properties such as high photocarrier mobility and high breakdown field, which exceeds 2×105 V/cm. The maximum output power before device failure at frequencies of 1 THz was of order 0.1 μW. This material has the potential to allow engineering of key photomixer properties such as the response time and dark resistance.