bluuebunny/crossref_metadata_2025 huggingface dataset:
Upregulation of heparin‐binding epidermal growth factor‐like growth factor and osteopontin in experimental hydronephrosis
Authors: Katerelos M , Kirkland G , Paizis K , Khong T , KANELLIS1 J. , Power Da
Published: July 2002

SUMMARY This study examined the expression of heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF) and osteopontin in unilateral ureteral obstruction (UUO) in the rat, a model of obstructive uropathy. HB‐EGF mRNA was upregulated 5.5‐fold at 4 h post‐obstruction (P < 0.05) and 4.5‐fold after 12 h (P < 0.05). Immunohistochemical staining for HB‐EGF demonstrated an increase in protein in the distended tubules. To determine what effects increased HB‐EGF might have in the obstructed kidney, we attempted to determine whether HB‐EGF upregulates osteopontin and α‐smooth muscle actin (α‐SMA) in the tubular line NRK‐52E. Both of these molecules are increased in UUO. Osteopontin mRNA was upregulated in NRK‐52E cells after 24, 48 and 72 h HB‐EGF stimulation. In contrast, HB‐EGF caused a downregulation of α‐SMA protein by Western blot in NRK‐52E cells. When a blocking mAb against secreted HB‐EGF was administered, however, there was no effect on osteopontin mRNA levels or immunohistochemical staining for α‐smooth muscle actin. These data suggest that the action of HB‐EGF in UUO may be to increase osteopontin and reduce α‐smooth muscle actin expression by tubular epithelial cells by an autocrine or intracrine mechanism. By reducing α‐SMA expression, HB‐EGF may also act to maintain epithelial cell morphology in this model.
A new treatment for penile conservation in penile carcinoma: a preliminary study of combined laser hyperthermia, radiation and chemotherapy
Authors: Shirahama  , Takemoto  , Nishiyama  , Nobori  , Kawahara  , Ohyama  , Ohi
Published: July 2002

Objective

 To investigate the role of laser hyperthermia in penis‐conserving therapy for penile carcinoma.

Patients, materials and methods

 Penile carcinoma KPK‐1 cells were transplanted into nude mice to induce tumour; the effects of laser hyperthermia, the chemotherapeutic agent peplomycin, or their combination on the inhibition of KPK‐1 tumour growth were assessed. In a clinical study, two patients with well‐differentiated, stage T2 penile tumours with corporeal involvement were treated to conserve the penis using concurrent radiation, laser hyperthermia and peplomycin. They had no pathologically identified regional lymph node metastasis. Radiation was given for 5 days a week for 3 weeks at a total dose of 30 Gy. Nd:YAG laser hyperthermia was administered at 42–43°C for 15 min twice a week for 3 weeks immediately after radiation. Peplomycin (10 mg per day) was administered intravenously over 24 h together with the laser hyperthermia.

Results

 The combined treatment with laser hyperthermia and peplomycin completely inhibited KPK‐1 tumour growth, but the treatment with either laser hyperthermia or peplomycin alone had little effect. The results were also corroborated by the histopathological findings; the necrotic area in mice treated with combined therapy was much larger than that in those treated with laser hyperthermia alone. Both patients given combined laser hyperthermia, radiation and peplomycin were treated successfully, with the penis and sexual function conserved, and both survived for >7 years with no evidence of any local or regional recurrence. There were no major complications related to the combined treatment.

Conclusions

 This preliminary study showed that combined treatment with laser hyperthermia, radiation and peplomycin might be a promising therapy for conserving the penis in some patients with stage T2 penile tumours.
Diabetes in the Caribbean: results of a population survey from Spanish Town, Jamaica
Authors: Wilks R. , Rotimi C. , Bennett F. , McFarlane‐Anderson N. , Kaufman J. S. , Anderson S. G. , Cooper R. S. , Cruickshank J. K. , Forrester T.
Published: July 2002

Aims To characterize the prevalence of diabetes and associated risk attributes in the Jamaican population.

Methods A random population sample was recruited by door‐to‐door canvassing (n = 1303). A final participation of 60% was achieved. Oral glucose tolerance testing was conducted after an overnight fast and standard anthropometric and demographic data were collected.

Results The prevalence of Type 2 diabetes mellitus was 9.8% (95% confidence interval (CI) 7.2–12.4) among men and 15.7% (95% CI 13.1–18.3) among women with an overall prevalence of 13.4% (95% CI 11.5–15.2). Impaired glucose tolerance was found among 12.3% of men and 14.7% of women. The sex patterns were consistent with a fourfold excess of obesity in women compared to men. The odds ratios for diabetes, fourth vs. first quartiles were 5.42 (95% CI 2.02–16.88) in men and 3.32 (95% CI 1.73–6.63) in women for body mass index (BMI) and 17.39 (95% CI 3.86–78.27) in men and 5.48 (95% CI 2.84–11.00) in women for WHR in a logistic model controlling for age. The population attributes risk percentage, for diabetes, of being overweight and having waist‐to‐hip ratio (WHR) greater than the median (0.80) were 66% and 80%, respectively. The contribution of central obesity, as characterized by WHR, was also significant in sex‐specific multivariate models that included age and BMI. Prevalent hypertension and family history of diabetes were likewise associated with increased odds of having the disease.

Conclusions The prevalence of diabetes in Jamaica now exceeds that observed among European‐origin populations and reflects the emerging epidemic of obesity. The excess risk for this population could not be attributed entirely to relative weight. The pronounced sexual dimorphism in diabetes prevalence most likely reflects the substantial excess of obesity among women compared to men. Like many other island nations, Caribbean societies now appear to be at substantial risk of diabetes.
Natural history of echogenic foci within ventricles of the fetal heart
Authors: Petrikovsky B. M. , Challenger M. , Wyse L. J.
Published: July 2002

Echogenic foci within the fetal heart have been reported in association with cardiac tumors and chromosomal abnormalities. They have been observed also as a normal variant of cardiac development. The goal of this study was to analyze the frequency, distribution and natural history of echogenic foci within the fetal heart. A total of 1139 patients referred for targeted ultrasound were studied. Patients with positive findings (presence of the echogenic foci) were referred for serial fetal echocardiographic examinations at 26–28 weeks and 34–36 weeks of pregnancy. Neonatal follow‐up examinations were performed within the first 3 months of life in 27 cases.

Ventricular echogenic foci were seen in 3.6% of fetuses. The locations of the echogenic foci were as follows: left ventricle, 92.8%; right ventricle, 4.8%; both ventricles, 2.4%. All fetuses had a normal karyotype. Echogenic foci remained present in all infants who underwent echocardiographic examination within the first 3 months of life.

Echogenic intracardiac foci probably represent a normal variant of the development of papillary muscles and chordae tendinae. Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology
MEISSNER CORPUSCLES IN PATIENTS WITH CONGENITAL AND ACQUIRED SENSORY NEUROPATHIES
Authors: Provitera V. , Nolano M. , Crisci C. , Stancanelli A. , Balbi P. , Lullo F. , Filla A. , Santoro L. , Caruso G.
Published: July 2002

Cutaneous innervation and particularly Meissner Corpuscles have been studied in glabrous skin of subjects with congenital and acquired sensory neuropathies.

We performed 3‐mm punch skin biopsies from fingertips of 14 patients with Friedreich's Ataxia (FA), 6 young subjects with diabetes mellitus without symptoms and clinical or electrophysiological signs of sensory neuropathy, and in 4 subjects with acquired sensory neuropathy of undefined origin. An age‐ and sex‐matched control group of ten healthy subjects underwent the same procedures. All subjects included in the study signed an informed consent form.

Once fixed and cryoprotected, the skin specimens were cut in 100‐micron‐thick sections and immunostained using primary antibodies specific for collagen (Col IV), nerve fibers (PGP 9.5), myelin sheet (MBP), and Meissner corpuscle capsula (S100), and linked to secondary antibodies labeled with Cy3 and Cy5 fluorophores. Digitized, completely in‐focus 3D images were obtained from z‐series of 2‐μm‐thick optical sections acquired with a confocal microscope.

We found a reduction of Meissner corpuscle total number, area, and density of innervation that appeared marked in patients with FA and moderate in diabetic patients. The third group of patients showed anomalies ranging from a mild reduction of the Meissner corpuscle area and density of innervation to a complete loss of the receptors.

Punch biopsy turned out to be an accurate tool to study the cutaneous innervation in glabrous skin and to assess the nervous structures health status also in the very early stages of the sensory neuropathies.
CONGENITAL HYPOMYELINATION NEUROPATHY WITH A NOVEL MUTATION OF PMP22
Authors: Rigatelli F. , Fabrizi G.M. , Simonati A. , Cavallaro T. , Ferrarini M. , Taioli F. , Mostacciuolo M.L. , Rizzuto N.
Published: July 2002

Congenital hypomyelination neuropathy (CHN) has been related with mutations of the MPZ gene that codes for P0, the major structural protein of the peripheral myelin and of EGR2/Krox20 gene that codes for a transcription factor essential for the normal development of myelinating Schwann cell. More recently, we reported the association between CHN and a Ser72Leu mutation of the peripheral myelin protein 22 (PMP22), a quantitatively minor component of the compact myelin of peripheral nerves, whose functions are still debated. Here we describe a second patient with CHN associated with a novel mutation of PMP22.

The patient is the 4‐year‐old daughter of healthy nonconsanguineous parents and is affected with early delay of motor development. At seven years she could not walk without support; examination disclosed muscle weakness and atrophy, foot drop, pes cavus, scoliosis, areflexia, and impairment of all sensory modalities. MNCV at the median nerve was 3.6 m/s. Nerve biopsy disclosed marked loss of fibers; residual fibers were devoid of myelin or encircled by extremely thin myelin sheaths and were surrounded by basal laminae onion bulbs. Clinical follow up demonstrated no progression of the disease. Molecular analysis disclosed a novel heterozygous T‐to‐C transition at nucleotide 374 of PMP22, that is predicted to cause a nonconservative substitution of cysteine109 (a phylogenetically conserved residue) with arginine, in the third transmembrane domain.

The duplication of PMP22 causes the common demyelinating form of Charcot‐Marie‐Tooth neuropathy type 1 (CMT1). Our reports indicate that missense mutations of the same protein may cause dysmyelination rather than demyelination, and prompt to investigate the function of PMP22 in myelinogenesis as well as in Schwann cell differentiation.
DISTINCT ROLES FOR LAMININ RECEPTORS IN THE DEVELOPMENT OF THE PERIPHERAL NERVOUS SYSTEM
Authors: Previtali S.C. , Nodari A. , Pardini C. , Taveggia C. , Dina G. , Villa A. , Graus‐Porta D. , Mueller U. , Wrabetz L. , Quattrini A. , Feltri M. L.
Published: July 2002

Laminin‐2 is required for normal nerve development, as mutations in a2 laminin chain in dystrophia muscularis mice disrupt Schwann cell‐axon relationships before birth (axonal sorting) in the proximal peripheral nervous system, and after birth (paranode formation, myelination) in the distal peripheral nervous system. Which laminin receptor(s) mediate these different roles, and the reasons for district variability is unknown. We first show that compensation by laminin‐1 in nerves, but not roots of dystrophic mice may explain the regional differences in severity. Second, we investigated spatial, temporal, and hierarchy of expression of pure laminin receptors, integrin a6b1 and a6b4, and dystroglycan, in the normal Schwann cell lineage from precursors to mature Schwann cells. A combination of descriptive and loss‐of‐function experiments in vivo, and a synchronized myelinating model in vitro, showed that a6b1 has a prominent role in prenatal Schwann cell‐axon interactions. Conditional inactivation of b1 integrin in Schwann cells is not compensated before birth by other laminin receptors, and arrests most Schwann cells at early stages of axonal sorting. However, some Schwann cells escape the block and myelinate normally, possibly because of redundancy of laminin receptors after birth, during myelination. In support for this, dystroglycan and a6b4 appear perinatally both in normal and mutant mice, and are expressed by b1 deleted‐Schwann cells that form normal myelin. Interestingly, the onset of dystroglycan expression in a single fiber immediately precedes and correlates with the beginning of myelination, while a6b4 distribution is related to late myelination and possibly to maintenance of myelin sheaths. These data indicate that laminin support early axoglial interactions (axonal sorting) through b1‐class integrins, and late axoglial interactions through dystroglycan and a6b4 integrin.
DEPTH DISTRIBUTIONS OF DNA DAMAGE IN ANTARCTIC MARINE PHYTO‐ AND BACTERIOPLANKTON EXPOSED TO SUMMERTIME UV RADIATION
Authors: Buma Anita G. J. , De Boer M. Karin , Boelen Peter
Published: July 2002

During a survey from January to March 1998, the occurrence of UV‐B radiation (UVBR)‐ induced DNA damage in Antarctic marine phytoplankton and bacterioplankton was investigated. Sampling was done in Ryder Bay, off the British base Rothera Station, 67°S, 68°W (British Antarctic Survey). Samples were taken regularly during the survey period at fixed depths, after which DNA damage was measured in various plankton size fractions (>10, 2–10, and 0.2–2 μm). Incident solar radiation was measured using spectroradiometry, whereas attenuation of biologically effective UVBR was studied using a DNA dosimeter. A diatom bloom was found in the bay during the research period, judging from microscopic observations and HPLC analyses of taxon‐specific pigments. The high phytoplankton biomass likely caused strong attenuation of DNA effective UVBR (Kbd‐eff). Kbd‐eff values ranged from 0.83·m−1 at the peak of the bloom to 0.47·m−1 at the end of the season. UVBR‐mediated DNA damage, as measured by cyclobutane pyrimidine dimer (CPD) abundance, was detected in all plankton size fractions. Highest levels were found in the smallest size fraction, mainly consisting of heterotrophic bacteria. Clear CPD depth profiles were found during mid‐summer (January, beginning of February) with surface levels exceeding 100 CPDs per million nucleotides in the bacterioplankton fraction. At that time, melting of the continuously present shelf ice caused strong salinity gradients in the upper meters, thereby stimulating water column stabilization. At the end of February and beginning of March, this phenomenon was less pronounced or absent. At that time, DNA damage was homogeneously distributed over the first 10 m, ranging between 20 and 30 CPDs per million nucleotides for the smallest size fraction.
Atomic constraint in hydrogenated ‘‘diamond-like’’ carbon
Authors: Tamor M. A. , Vassell W. C. , Carduner K. R.
Published: July 2002

Carbon bonding environments (measured by nuclear magnetic resonance spectroscopy) and compressive stress in plasma-deposited hydrogenated diamond-like carbon (DLC) films have been examined systematically as a function of substrate bias voltage. These results are related in terms of random network theory to show that hard DLC formed in an intermediate voltage range (100–400 V) consists of small graphitic clusters linked in a random network which is stiffened by a high density of quaternary carbon.
Growth of cubic boron nitride on diamond particles by microwave plasma enhanced chemical vapor deposition
Authors: Saitoh H. , Yarbrough W. A.
Published: July 2002

The nucleation and growth of cubic boron nitride (c-BN) onto diamond powder using solid NaBH4 in low pressure gas mixtures of NH3 and H2 by microwave plasma enhanced chemical vapor deposition has been studied. Boron nitride was deposited on submicron diamond seed crystals scattered on (100) silicon single crystal wafers and evidence was found for the formation of the cubic phase. Diamond powder surfaces appear to preferentially nucleate c-BN. In addition it was found that the ratio of c-BN to turbostratic structure boron nitride (t-BN) deposited increases with decreasing NH3 concentration in H2. It is suggested that this may be due to an increased etching rate for t-BN by atomic hydrogen whose partial pressure may vary with NH3 concentration.
Nonlinear refractive index measurement in chalcogenide-glass fibers by self-phase modulation
Authors: Asobe Masaki , Suzuki Ken’ichi , Kanamori Terutoshi , Kubodera Ken’ichi
Published: July 2002

Nonlinear refractive index (n2) of chalcogenide-glass (As2S3) fibers has been evaluated for the first time from spectral broadening due to self-phase modulation. The obtained value of n2 was 1.7×10−14 (cm2/W) which is two orders of magnitude higher than the value with silica-glass fiber. This large n2 value is useful in reducing switching power and size when fiber is used for all-optical switches.
Broadly tunable picosecond pulses generated in a β-BaB2O4 optical parametric amplifier pumped by 0.532 μm pulses
Authors: Zhu X. D. , Deng L.
Published: July 2002

We report the generation of a highly intense, tunable source from 0.67 μm to 2.58 μm by optical parametric generation and amplification in β-barium borate (BBO) pumped by picosecond pulses at 0.532 μm. The maximum conversion efficiency from the pump to the signal is 13%. The output energy is in the range a few hundred μJ.
Infrared reflectance of thin aluminum nitride films on various substrates
Authors: MacMillan M. F. , Devaty R. P. , Choyke W. J.
Published: July 2002

The measured room-temperature infrared reflectance at near-normal incidence of thin AlN films deposited by metalorganic chemical vapor deposition on various substrates is compared with calculated spectra based on Lorentz oscillator models for the reststrahl regions with parameters obtained from the literature. The effects of film and substrate anisotropy and non-normal incidence are included. The contribution of AlN can be analyzed even when the substrate and/or a thin overlayer have overlapping reflection bands. It is possible to obtain information on the thickness and other properties of the AlN films.
p-type zinc-blende GaN on GaAs substrates
Authors: Lin M. E. , Xue G. , Zhou G. L. , Greene J. E. , Morkoç H.
Published: July 2002

We report p-type cubic GaN. The Mg-doped layers were grown on vicinal (100) GaAs substrates by plasma-enhanced molecular beam epitaxy. Thermally sublimed Mg was, with N2 carrier gas, fed into an electron-cyclotron resonance source. p-type zinc-blende-structure GaN films were achieved with hole mobilities as high as 39 cm2/V s at room temperature. The cubic nature of the films were confirmed by x-ray diffractometry. The depth profile of Mg was investigated by secondary ions mass spectroscopy.
Eddy current damping of planar domain wall in bistable amorphous wires
Authors: del Real R. P. , Prados C. , Chen D.-X. , Hernando A. , Vázquez M.
Published: July 2002

An exact formula for the field produced by the eddy currents induced by transverse movements of a longitudinal planar domain wall in a magnetic cylinder is obtained. The result has been extended to satisfy the situation of bistable iron-rich amorphous wires and compared with the dMav/dt pulse of such wires during magnetization reversal. It is shown that the propagating wall is essentially planar and the damping is solely due to eddy currents.
Electron transport in strained Si layers on Si1−xGex substrates
Authors: Vogelsang Th. , Hofmann K. R.
Published: July 2002

Results on the in-plane electron drift velocities and mobilities in strained Si layers grown on Si1−xGex substrates are reported for 300 and 77 K. High-field drift velocities are calculated by Monte Carlo simulations and low-field mobilities by numerical solution of Boltzmann’s equation including intra- and intervalley phonon and impurity scattering mechanisms. Significant improvements of drift velocities relative to bulk Si are found for electric fields up to several 10 kV/cm, while saturation occurs at the bulk values for both temperatures. A much stronger mobility enhancement of 74% is obtained at 300 K compared to 36% at 77 K, which is consistent with recent experimental results.
Room temperature conductance quantization in V‖amorphous-V2O5‖V thin film structures
Authors: Yun Eui-Jung , Becker M. F. , Walser R. M.
Published: July 2002

With a parallel component removed, the room temperature conductance of V‖amorphous-V2O5‖V sandwiches at low voltages (8<qV/kT<15) is stepped at discrete values G=2ie2/h, where h is Planck’s constant, e is the electron charge, and i is the integer or half-integer. In contrast with similar results reported by J. Hajto, M. J. Rose, A. J. Snell, I. S. Osborne, A. E. Owen, and P. G. LeComber [J. Non Cryst. Solids 137-138, 499 (1991)] conductance quantization was observed without electroforming at high voltages. The results suggest that a ballistic point contact was formed in the nonmetal-metal interphase either by a laterally unstable contact reaction during deposition, or by electronic injection at low bias voltage. The onset of conductance quantization at a highly characteristic threshold voltage favors the latter.
Talbot assisted hexagonal beam patterning in a thin liquid crystal film with a single feedback mirror at negative distance
Authors: Ciaramella E. , Tamburrini M. , Santamato E.
Published: July 2002

We investigate experimentally the generation of hexagonal patterns of filaments in a laser beam traversing a thin liquid crystal cell placed in front of a single ‘‘virtual mirror.’’ This mirror is the image of a real mirror and is placed either in front of or behind the cell. The results clearly support the physical idea that the Talbot effect governs the phenomenon. Edge effects due to the limited width of the pump beam are accounted for both theoretically and experimentally.
Hole capture in boron-doped diamond
Authors: Glesener John W.
Published: July 2002

A carrier capture model based on the work of Lax [Phys. Rev. 119, 1502 (1960)] and Gibb et al. [Philos. Mag. 36, 1021 (1977)] is applied to diamond. This model accounts for the lower activation energy for boron in diamond measured using deep level transient spectroscopy (DLTS) techniques. The model assumes that when a carrier in the valence band is captured by an impurity, it occupies the highest energy acceptor excited state and then is quickly funneled to the lowest excited acceptor level. At the lowest energy excited acceptor level the trapped hole either thermalizes back to the valence band or reaches the ground state of the impurity via a ‘‘slow’’ multiphonon decay. Using this kinetic picture, previously reported DLTS results are shown to be consistent with the energy parameters for the boron acceptor level. These results will be of interest to researchers simulating the device properties of diamond and are an indication of the influence of the acceptor spectrum on the electrical properties of boron-doped diamond.
Quantum cascade laser with plasmon-enhanced waveguide operating at 8.4 μm wavelength
Authors: Sirtori Carlo , Faist Jerome , Capasso Federico , Sivco Deborah L. , Hutchinson Albert L. , Cho Alfred Y.
Published: July 2002

A unipolar cascade laser operating at 8.4 μm wavelength is reported. The structure, grown by molecular beam epitaxy in the AlInAs/GaInAs material system, contains a 25-stage coupled-quantum-well active region. The waveguide design is optimized to enhance optical confinement and reduce losses associated with the interface plasmon mode, by taking advantage of the dispersion of the refractive index of the contact layer near the plasma frequency. The peak optical power is 30 mW and the threshold current density 2.8 kA/cm2, at a heat-sink temperature of 100 K and the highest operating temperature is 130 K. The slope efficiency at 100 K is ∼0.1 W/A, corresponding to a differential quantum efficiency of 5.4% per stage. This work, combined with previous results on shorter wavelength quantum cascade lasers, demonstrates that the wavelength of these new light sources can be tailored over a wide range by changing the active layers’ thicknesses using the same materials.
Self-aligning capacitive transducer for the detection of broadband ultrasonic displacement signals
Authors: Kim Kwang Yul , Sachse Wolfgang
Published: July 2002

This paper describes a self-aligning capacitive transducer for detecting broadband ultrasonic signals in structural components. The fixed electrode is the specimen surface while the adjustable electrode is pivoted on a ball mount so designed that the electrode aligns itself parallel to the specimen surface when pressed against it. The working gap between the adjustable electrode and the specimen surface is set by a mechanically driven differential micrometer. The design of the transducer permits minimization of the electrode gap to maximize the sensitivity of the transducer to small amplitude, surface displacement signals. It is demonstrated that such a capacitive transducer is well suited to obtaining a high-fidelity response to transient surface displacement signals which are of broad bandwidth and low amplitude.
Small diameter nozzle plasma arc as a processing tool
Authors: Kimura T. , Komatsu A. , Yoshioka S. , Miyazaki T.
Published: July 2002

High-power-density plasma arc equipment with a small diameter nozzle of 0.1–0.3 mm has been developed, which produces power density of about 104 W/mm2 at the exit of the nozzle. The density is comparable to those produced by electron and laser beams. In the present article, development procedure, power density on the target surface, and processing capability in comparison to the conventional electron and laser beams are described. The power density as the processing heat source depends on the kind of processing. The apparent power density in cutting is of the order of 104 W/mm2; on the other hand, that in surface hardening is of the order of 102 W/mm2. The processing capability for causing melting such as cutting and welding does not depend on the working distance, which is defined as the distance between the torch and target material; furthermore, the deviation of the torch from the correct position does not affect the processing capability. The equipment developed is suitable for an automated production system because high precision position control of the torch is not required.
High-temperature diamond p-n junction: B-doped homoepitaxial layer on N-doped substrate
Authors: Borst T. H. , Strobel S. , Weis O.
Published: July 2002

Boron-doped homoepitaxial layers have been selectively grown on synthetic type Ib substrates of (100) cut. Ohmic contacts were formed by evaporating a Mo/Pt/Au sandwich and subsequent annealing at 950°C for h. Current–voltage characteristics of diode type could be taken in vacuum in the temperature range 360–900 °C. Green light emission due to electroluminescence was observed from the junction area showing a maximum at a wavelength of 534 nm corresponding to a photon energy of 2.32 eV. The normalized emission spectrum was measured over the temperature range 320–440 °C with the device in air and was found independent of temperature and boron concentration.
A compact, high-pressure capillary viscometer
Authors: Ripple Dean
Published: July 2002

A high-pressure capillary viscometer is described. Similar to an Ubbelhode viscometer, the instrument is compact, requires a sample of only 1 ml of saturated liquid, and is simple to make and use. The viscometer can readily measure kinematic viscosities as small as 2×10−7 m2/s and can sustain vapor pressures over 1 MPa. The sample contacts only sapphire, stainless steel, and gold, allowing measurement of corrosive liquids. The overall accuracy is approximately 3%.
Rapid projection of crystal grain orientation distribution in mild steel sheets by synchrotron x-ray diffraction
Authors: Kawasaki Koichi , Iwasaki Hiroshi , Yoshinaga Naoki
Published: July 2002

An investigation on primary recrystallization process of mild steel sheets was carried out by using the method developed by the present authors for rapid projection of the crystal grain orientation distribution, the pole figure, in polycrystalline materials. Measurements were made at the beamline BL-3A at the Photon Factory. It was shown that the projected pattern was continuous in the cold-rolled state. When the sheet was annealed, tiny diffraction spots or small grains appeared in the continuous pattern of cold-rolled state. Successive growing of crystal grains is seen as an increase in the size of diffraction spots.
Sensitivity analysis of a resonant-mass gravitational wave antenna with a parametric transducer
Authors: Tobar Michael Edmund , Blair David Gerald
Published: July 2002

A frequency domain approach is applied to the University of Western Australia’s resonant bar detector to determine its potential sensitivity and calculate the limiting noise sources. To understand its behavior the sensitivity is calculated as a function of various noise components. To minimize seismic noise upconversion, the system is operated in the cold damping regime at the turning point in the antenna frequency versus pump frequency characteristic. For this configuration it is shown that the spectral strain sensitivity of a high-Q antenna with a parametric transducer can exceed 10−21 √Hz with approximately a 20 Hz bandwidth, using existing microwave technology. This corresponds to a strain sensitivity of less than 10−19 for a 1 ms gravitational pulse.
Interferometric measurements of electric field-induced displacements in piezoelectric thin films
Authors: Kholkin A. L. , Wütchrich Ch. , Taylor D. V. , Setter N.
Published: July 2002

Interferometric measurements of electric field-induced displacements in piezoelectric thin films using single-beam and double-beam optical detection schemes are reported. It is shown that vibrational response measured with a single-beam interferometer includes a large contribution of the bending motion of substrate. Therefore, it is difficult to apply single-beam technique for piezoelectric measurements in thin films. To suppress the bending effect a high-resolution double-beam interferometer is proposed. The sensitivity of the interferometer is significantly improved in comparison with previously reported system. The interferometer is shown to resolve small displacements without using a lock-in technique. An example of the interferometric capabilities is demonstrated with experimental results on electric field, frequency, and time dependences of piezoelectric response for quartz and Pb(Zr,Ti)O3 thin film.
Compact active quenching circuit for fast photon counting with avalanche photodiodes
Authors: Ghioni M. , Cova S. , Zappa F. , Samori C.
Published: July 2002

A compact and flexible circuit for operating avalanche photodiodes in Geiger mode was designed, fabricated, and tested. A new voltage driver stage, based on fast n-channel double-diffused metal–oxide–semiconductor (DMOS) transistors in a bootstrap configuration, makes it possible to obtain quenching pulses up to 25 V amplitude and fast active reset of the detector. At 20 V excess bias voltage above the photodiode breakdown level, an overall deadtime shorter than 36 ns is attained. The avalanche pulse charge is minimized by means of a mixed passive–active quenching approach, thus reducing self-heating and afterpulsing effects in the photodiode. A user-controllable hold-off time is available for further reducing the afterpulsing effect. The saturated counting rate of the circuit exceeds 25 Mcounts/s, but, by working with avalanche photodiodes with high breakdown voltage (250–400 V) and high avalanche current (10–40 mA), a practical limit is set at about 9 Mcounts/s by thermal effects in the detector. Gated-detector operation with gate times down to 10 ns is provided. The suitability of the new active-quenching circuit for the development of compact, all-solid-state instruments for high-performance photon counting was verified in experimental tests.
Formation of YBa2Cu3O7−y/BaTiO3 multistructures by pulsed laser deposition for high-temperature superconducting device applications
Authors: Hontsu S. , Ishii J. , Tabata H. , Kawai T.
Published: July 2002

The formation of YBa2Cu3O7−y(YBCO)/BaTiO3(BTO)//SrTiO3(STO) (100) and BTO/ YBCO//STO(100) bilayer structures is demonstrated for the construction of a superconductor ferroelectric field transistor. The resulting films of the bilayers have highly c-axis oriented structure. Epitaxial YBCO films formed on the BTO//STO(100) have a zero resistance temperature of 88.9 K. The surface morphology of the epitaxial BTO films on the YBCO//STO is very smooth with a mean surface roughness of 32 Å. Moreover, the Au/BTO/YBCO structures have been fabricated, and the dielectric constant and remanent polarization of BTO layer are obtained to be 180 and 3.5 μC/cm2 at 77 K, respectively.
Application of liftoff low-temperature-grown GaAs on transparent substrates for THz signal generation
Authors: Heiliger H.-M. , Vossebürger M. , Roskos H. G. , Kurz H. , Hey R. , Ploog K.
Published: July 2002

Epitaxial liftoff (ELO) of low-temperature-grown GaAs (LT-GaAs) is employed to fabricate (sub)picosecond photoconductive switches on optically transparent substrates for THz applications. Glass is selected as a substrate for on-wafer probes while sapphire is chosen for free-space antennas.
Observation of electrically resettable negative persistent photoconductivity in InAs/AlSb single quantum wells
Authors: Wang Fu-Cheng , Zhang W. E. , Yang C. H. , Yang M. J. , Bennett B. R.
Published: July 2002

The mechanism of the negative persistent photoconductivity (NPPC) in InAs/AlSb single quantum wells is discussed. The molecular beam epitaxy grown single InAs quantum well sample is made into Hall bars with the substrate as the backgate. Using the newly designed buffer, the gate bias can deplete or enhance the two-dimensional electrons in the InAs quantum well without substantial gate leakage current. Based on the 4.2 K magnetoresistance data, and the fact that the trapped electrons can be redistributed by gate bias, we conclude that the NPPC effect at low temperatures is a result of the capture of photoexcited electrons by ordinary, deep donors in AlSb. Numerical modeling using physical assumptions can quantitatively explain our experimental observation, and the calculated AlSb donor energy is 0.41±0.05 eV above the AlSb valence band maximum, with 4×1016/cm3 to 1017/cm3 in concentration. The previously discussed DX-center-like characteristic of deep levels in AlSb, i.e., lattice-relaxation with a relatively high activation energy, is not evidenced in this work.
New features of the layer-by-layer deposition of microcrystalline silicon films revealed by spectroscopic ellipsometry and high resolution transmission electron microscopy
Authors: Roca i Cabarrocas P. , Hamma S. , Hadjadj A. , Bertomeu J. , Andreu J.
Published: July 2002

Spectroscopic ellipsometry and high resolution transmission electron microscopy have been used to characterize microcrystalline silicon films. We obtain an excellent agreement between the multilayer model used in the analysis of the optical data and the microscopy measurements. Moreover, thanks to the high resolution achieved in the microscopy measurements and to the improved optical models, two new features of the layer-by-layer deposition of microcrystalline silicon have been detected: (i) the microcrystalline films present large crystals extending from the a-Si:H substrate to the film surface, despite the sequential process in the layer-by-layer deposition; and (ii) a porous layer exists between the amorphous silicon substrate and the microcrystalline silicon film.
Microstructure of Ti/Al ohmic contacts for n-AlGaN
Authors: Ruvimov S. , Liliental-Weber Z. , Washburn J. , Qiao D. , Lau S. S. , Chu Paul K.
Published: July 2002

Transmission electron microscopy was employed to evaluate the microstructure of Al/Ti ohmic contacts to AlGaN/GaN heterostructure field-effect transistor structures. Contact resistance was found to depend on the structure and composition of the metal and AlGaN layers, and on atomic structure of the interface. A 15–25-nm-thick interfacial AlTi2N layer was observed at the contact-AlGaN interface. Formation of such nitrogen-containing layers appears to be essential for ohmic behavior on n-type III-nitride materials suggesting a tunneling contact mechanism. Contact resistivity was found to increase with Al fraction in the AlGaN layer.
Island size effects in nanoparticle-enhanced photodetectors
Authors: Stuart Howard R. , Hall Dennis G.
Published: July 2002

We report the effect of metal-island size variation in nanoparticle-enhanced photodetectors. Nanoparticle size was controlled by varying the deposition and annealing conditions used to produce the metal-island films. Increasing the size of silver-island particles fabricated onto 165 nm thick silicon-on-insulator (SOI) photodetectors resulted in a dramatic increase in the observed photocurrent. A nearly factor-of-20 photocurrent enhancement was observed for light of wavelength 800 nm, a significant improvement over previously reported results. The improvement is linked to two physical effects: the increased scattering efficiency of the larger nanoparticles and a qualitative change in the resonance characteristics of the metal-island film due to radiative coupling to the SOI waveguide modes.
Effect of the linewidth reduction on the characteristic time spread in C49–C54 phase transition
Authors: Privitera S. , La Via F. , Grimaldi M. G. , Rimini E.
Published: July 2002

The kinetics of the C49–C54 phase transformation in TiSi2 narrow strips for width in the 0.5–1.3 μm range was investigated by sheet resistance measurements. The experimental data follow the Johnson–Mehl–Avrami equation for the fraction of the transformed material, with an exponent equal to 1 for all of the analyzed linewidths. Nucleation sites saturation occurs and the growth is one-dimensional along the length of the strip. The characteristic time, as obtained by the fit, increases as 1/W, W being the width of the strip, and a nucleation density of about 0.05 sites/μm2 has been obtained. The distribution of the characteristic times around the average value increases with decreasing the linewidth. The amplitude of the dispersion is in quantitative agreement with the statistical fluctuation of the number of nucleation sites.
Differential carrier lifetime in oxide-confined vertical cavity lasers obtained from electrical impedance measurements
Authors: Giudice G. E. , Kuksenkov D. V. , Temkin H. , Lear K. L.
Published: July 2002

Differential carrier lifetime measurements were performed on index-guided oxide-confined vertical cavity surface emitting lasers operating at 980 nm. Lifetimes were extracted from laser impedance measurements at subthreshold currents, with device size as a parameter, using a simple small-signal model. The carrier lifetimes ranged from 21 ns at 9 μA, to about 1 ns at a bias close to threshold. For a 6×6 μm2 oxide aperture device the threshold carrier density was nth∼2×1018 cm−3. The effect of carrier diffusion was also considered. An ambipolar diffusion coefficient of D∼11 cm2 s−1 was obtained.
Direct monitoring of thermally activated leakage current in AlGaInP laser diodes
Authors: Wood S. A. , Smowton P. M. , Molloy C. H. , Blood P. , Somerford D. J. , Button C. C.
Published: July 2002

Using specially prepared structures, we have observed emission from a layer of direct-gap “monitor” material placed between the p-contact layer and p-cladding layer of a conventional 670 nm GaInP laser diode at room temperature. This observation provides direct evidence for electron leakage through the p-cladding layer in these devices. Furthermore, although emission from the quantum well and waveguide core both pin above threshold, indicating that the Fermi levels clamp throughout the active region, the monitor emission continues to rise above threshold. This is characteristic of a drift component to the leakage current, which we have confirmed by a simulation of the carrier transport processes through the cladding layer with and without drift.
Scratching resistance of diamond-like carbon coatings in the subnanometer regime
Authors: Wienss A. , Persch-Schuy G. , Vogelgesang M. , Hartmann U.
Published: July 2002

In order to examine the scratching resistance of ultrathin hydrogenated amorphous carbon (a-C:H) coatings used in magnetic storage devices, a large number of scratches with reproducible residual groove depths well below 1 nm has been examined. All measurements were carried out with an atomic force microscope and diamond-tipped cantilevers. The analysis of such shallow scratches is made possible by means of an image processing procedure which minimizes surface roughness effects using subtraction imaging. This method was applied to a series of sputter-deposited, fully aged, unlubricated amorphous coatings with different hydrogenations. For low hydrogen content in the sputtering gas, the scratching resistance decreased with an increasing amount of hydrogen, in accordance with many other experiments. In contrast, an unusual slight improvement of the scratching resistance for a further increase of hydrogenation was obtained.
Backswitch poling in lithium niobate for high-fidelity domain patterning and efficient blue light generation
Authors: Batchko Robert G. , Shur Vladimir Y. , Fejer Martin M. , Byer Robert L.
Published: July 2002

In nonlinear optics applications employing quasiphase matching, short-pitch domain gratings are generally required for the efficient generation of visible and ultraviolet light. Here we introduce an improved electric-field poling technique, which incorporates spontaneous backswitching and leads to uniform short-pitch domain structures. The total volume of backswitched material, and hence the duty cycle of the backswitched domain grating, can be accurately controlled. First-order single-pass continuous-wave second harmonic generation of 60 mW at 460 nm is achieved at 6.1%/W efficiency in 0.5-mm-thick 4-μm-period backswitch-poled lithium niobate.
High-efficiency midinfrared “W” laser with optical pumping injection cavity
Authors: Felix C. L. , Bewley W. W. , Vurgaftman I. , Olafsen L. J. , Stokes D. W. , Meyer J. R. , Yang M. J.
Published: July 2002

We describe an optical pumping injection cavity (OPIC) edge-emitting laser which employs GaSb/AlAsSb distributed Bragg reflectors above and below the type-II “W” active region to form an etalon for the pump beam. A pulsed W–OPIC laser emitting at 3.1–3.4 μm displays an incident threshold pump intensity of only 8 kW/cm2 at 300 K, and incident power conversion efficiencies per facet of 9% at 77 K and 4% at 275 K.
Thin film characterization by atomic force microscopy at ultrasonic frequencies
Authors: Crozier K. B. , Yaralioglu G. G. , Degertekin F. L. , Adams J. D. , Minne S. C. , Quate C. F.
Published: July 2002

We present a technique in which atomic force microscopy at ultrasonic frequencies is used to determine the thickness of thin films. In this technique, the resonance frequency of a flexural mode of an atomic force microscope cantilever is used to determine the tip-sample contact stiffness. This allows the film thickness to be determined, provided that the tip and sample elastic moduli and radii of curvature are known. We report experimental results for thin metal and polymer films deposited on silicon substrates and compare them with the predictions of a theoretical model.
Electric-pulse-induced reversible resistance change effect in magnetoresistive films
Authors: Liu S. Q. , Wu N. J. , Ignatiev A.
Published: July 2002

A large electric-pulse-induced reversible resistance change active at room temperature and under zero magnetic field has been discovered in colossal magnetoresistive (CMR) Pr0.7Ca0.3MnO3 thin films. Electric field-direction-dependent resistance changes of more than 1700% were observed under applied pulses of ∼100 ns duration and as low as ±5 V magnitude. The resistance changes were cumulative with pulse number, were reversible and nonvolatile. This electrically induced effect, observed in CMR materials at room temperature has both the benefit of a discovery in materials properties and the promise of applications for thin film manganites in the electronics arena including high-density nonvolatile memory.
Performance and spectral response of Pb1−xSnxTe(In) far-infrared photodetectors
Authors: Khokhlov D. R. , Ivanchik I. I. , Raines S. N. , Watson D. M. , Pipher J. L.
Published: July 2002

We have compared directly the performance of a Pb1−xSnxTe(In) photodetector with that of two other state-of-the-art far-infrared detectors: a Si(Sb) blocked impurity band (BIB) detector and a Ge(Ga) photoconductor in an integrating cavity. The Pb1−xSnxTe(In) photodetector has current responsivity SI several orders of magnitude higher than the Si(Sb) BIB at wavelength λ=14.5 μm. Persistent photoresponse with SI∼103 A/W at 40 mV bias and 1 s integration time at the wavelengths λ=90 and 116 μm has also been observed in the Pb1−xSnxTe(In) photodetector. This is larger by a factor of ∼100 than the responsivity of the Ge(Ga) photoconductor in the same conditions.
Electronic structure of the Fe–Cu–Nb–Si–B alloys by x-ray absorption spectroscopy
Authors: Cheng Y. H. , Jan J. C. , Chiou J. W. , Pong W. F. , Tsai M.-H. , Hseih H. H. , Chang Y. K. , Dann T. E. , Chien F. Z. , Tseng P. K. , Leu M. S. , Chin T. S.
Published: July 2002

We measured x-ray absorption near-edge-structure (XANES) spectra of nanocrystalline- (nc-) and amorphous- (a-) Fe73.5Cu1Nb3Si13.5B9 (nc-FCNSB and a-FCNSB) and Fe78Si13B9 (a-FeSiB) alloys at the Fe L3,2 edge using the sample drain current mode and at the Cu L3,2, and Nb L3 edge and Si K edge using the fluorescence mode. The features in the Fe L3-edge XANES spectrum of nc-FCNSB changed shape significantly with the addition of Cu and Nb to the Fe–Si–B alloy under the optimum annealing conditions, indicating that Cu and Nb strongly influence the Fe 3d local electronic structure. Closely examining the Cu L3,2-edge XANES spectrum of nc-FCNSB reveals that the Cu clusters essentially have a body-centered-cubic structure. The white-line features at the Nb L3 edge suggest a slight increase in delocalization of Nb 4d orbits when a-FCNSB is crystallized into nc-FCNSB. The Si K-edge XANES spectrum demonstrates the dominance of Fe–Si bonds around the Si atom in nc-FCNSB.
Electron transport in a single silicon quantum structure using a vertical silicon probe
Authors: Nishiguchi Katsuhiko , Oda Shunri
Published: July 2002

We present a method of electrical measurement of single nanocrystalline silicon (nc-Si) particles fabricated by plasma-enhanced chemical vapor deposition (CVD) at very high frequency of 144 MHz. A vertical Si probe structure with a spheroidal shaped hole in SiO2 and a CVD grown polycrystalline Si electrode allows stable measurement of current through a single nc-Si quantum dot. Periodic Coulomb staircases are observed between 5 and 50 K. The temperature dependence of the differential conductance is consistent with these being electron transport through a double junction array. A Monte Carlo simulation further supports the double junction array model where a nc-Si quantum dot is covered by 1.5-nm-thick natural oxide as a tunnel barrier. Moreover, applying a wraparound gate makes it possible to observe Coulomb oscillation.