bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular cloning, functional expression, and signal transduction of the GIP‐receptor cloned from a human insulinoma
Authors: Volz Anja , Göke Rüdiger , Lankat-Buttgereit Brigitte , Fehmann Hans-C. , Bode Hans P. , Göke Burkhard
Published: July 2002

Glucose‐dependent insulinotropic polypeptide (GIP) plays an important role in the regulation of postprandial insulin secretion and proinsulin gene expression of pancreatic β‐cells. This study demonstrates the molecular cloning of a cDNA for the GIP‐receptor from a human insulinoma λgt11 cDNA library. The cloned cDNA encoded a seven transmembrane domain protein of 466 amino acids which showed high homology (41%) to the human glucagon‐like peptide 1 (GLP‐1) receptor. Homology to the GIP receptor from rat or hamster was 79% and 81%, respectively. When transfected stably into fibroblast CHL‐cells a high affinity receptor was expressed which coupled to the adenylate cyclase with normal basal cAMP and increasing intracellular cAMP levels under stimulation with human GIP‐1–42 (EC50 = 1.29 × 10−13 M). The receptor accepted only human GIP 1–42 (K
d = 1.93 ± 0.2 × 10−8 M) and porcine truncated GIP‐1–30 (K
d = 1.13 ± 0.1 × 10−8 M) as high affinity ligands. At 1 μM, exendin‐4 and (9–39)amide weakly reduced GIP‐binding (25%) whereas secretin, glucagon, glucagon‐like peptide‐1, vasoactive intestinal polypeptide, peptide histidine‐isoleucine, and pituitary adenylyl cyclase activating peptide were without effect. In transfected CHL cells, GIP‐1–42 did not increase intracellular calcium. Northern analysis revealed one transcript of human GIP receptor mRNA with an apparent size of 5.5 kb. The exact understanding of GIP receptor regulation and signal transduction will aid in the understanding of the incretin hormone's failure to exert its biological action at the pancreatic B‐cell in type II diabetes mellitus.
Endoscopic surgery in gynecologic practice
Authors: Verhulst G. , Devroey P.
Published: July 2002

In recent decades, the operative approach for several gynecologic diseases has changed from laparotomy to laparoscopy. New techniques and indications are continuously being developed. Laparoscopy offers a lot of advantages for the patient, but still a lot of additional data are required to determine the exact indications. Operative laparoscopy requires not only skill and experience, but also specialized equipment and paramedical staff. The most important topics for the gynecologist will be reviewed in this article.
Dysgerminoma of the ovary in a patient with triple‐X syndrome
Authors: Kemp B. , Hauptmann S. , Schröder W. , Amo‐Takyi B. , Leeners B. , Rath W.
Published: July 2002

A 24‐year‐old patient with dysgerminoma of the right ovary and hypoplastic left ovary was screened for chromosomal aberration. Triple‐X syndrome was found in the oral epithelium and lymphocyte culture, while chromosomal in situ hybridization of the tumor itself showed a normal XX karyotype. Although trisomy X and dysgerminoma are coincidental findings in our case report, women with malignant germ cell tumors and abnormal genitalia should be checked for chromosomal aberrations to exclude anomalies carrying a Y chromosome.
Lithium: poisonings and suicide prevention
Authors: Montagnon F. , Saïd S. , Lepine J.P.
Published: July 2002

This study concerns 81 cases of lithium poisoning and shows that deliberate intoxications are prevalent during the first 3 years of lithium treatment as well as in cases with a previous history of suicide attempt. Therapeutic intoxications could generally be avoided by education concerning hygiene and diet and careful monitoring in cases of intercurrent diseases.
Combined Effects of Temperature and Medium Composition on Exopolysaccharide Production by Lactobacillusrhamnosus RW‐9595M in a Whey Permeate Based Medium
Authors: Macedo Maria G. , Lacroix Christophe , Champagne Claude P.
Published: July 2002

The effects of temperature (22–42 °C), whey permeate concentration (WP, 1.6–8.4%), and supplementation level with yeast nitrogen base (YNB, 0–2.0%) on exopolysaccharide (EPS) production was studied during 20 pH‐controlled (pH = 6.0) batch cultures with Lactobacillus rhamnosus RW‐9595M, using a central composite design (CCD). The EPS production was measured using both the conventional method based on ethanol precipitation of EPS and a new ultrafiltration (UF) method. EPS production was not growth‐associated for high temperatures (32–42 °C) and WP concentrations (7.0–8.4%). In contrast, at suboptimal temperature (22–26 °C), EPS production was growth‐associated. Maximal EPS production measured with the UF method was approximately 2‐fold higher than those measured with the conventional method and varied from 125 to 477 mg/L. This parameter was significantly influenced by WP and YNB*WP interaction, whereas ANOVA for maximal EPS production measured by the conventional method did not show significant factor effects. EPS volumetric productivities varied from 3.0 to 16.4 mg EPS/L·h. YNB supplementation did not promote cell growth but did increase EPS production at high WP concentrations. Our data indicate the potential of L. rhamnosus RW‐9595M for producing EPS in a supplemented WP medium and suggest that this production could be further increased by the addition of a growth‐limiting nutrient in the medium.
Effects of solution polarity and viscosity on peptide deamidation
Authors: Li R. , D'souza A.J. , Schowen R.L. , Borchardt R.T. , Topp E.M. , Laird B.B.
Published: July 2002

Abstract: Deamidation kinetics were measured for a model hexapeptide (l‐Val‐l‐Tyr‐l‐Pro‐l‐Asn‐Gly‐l‐Ala, 0.02 mg/mL) in aqueous solutions containing glycerol (0–50% w/w) and poly(vinyl pyrrolidone) (PVP, 0–20% w/w) at 37 °C and pH 10 to determine the effects of solution polarity and viscosity on reactivity. The observed pseudo‐first order deamidation rate constants, kobs, decreased markedly when the viscosity increased from 0.7 to 13 cp, but showed no significant change at viscosities > 13 cp. Values of kobs also increased with increasing dielectric constant and decreasing refractive index. Molecular dynamics simulations indicated that the free energy associated with Asn side‐chain motion is insensitive to changes in dielectric constant, suggesting that the observed dielectric constant dependence is instead related primarily to the height of the transition state energy barrier. An empirical model was proposed to describe the effects of the viscosity, refractive index and dielectric constant on kobs. Analysis of the regression coefficients suggested that both permanent and induced dipoles of the medium affect the deamidation rate constant, but that solution viscosity is relatively unimportant in the range studied.
Expression of human electron transfer flavoprotein-ubiquinone oxidoreductase from a baculovirus vector: kinetic and spectral characterization of the human protein
Authors: ŠIMKOVIČ Martin , DEGALA Gregory D. , EATON Sandra S. , FRERMAN Frank E.
Published: July 2002

Electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) is an iron—sulphur flavoprotein and a component of an electron-transfer system that links 10 different mitochondrial flavoprotein dehydrogenases to the mitochondrial bc1 complex via electron transfer flavoprotein (ETF) and ubiquinone. ETF-QO is an integral membrane protein, and the primary sequences of human and porcine ETF-QO were deduced from the sequences of the cloned cDNAs. We have expressed human ETF-QO in Sf9 insect cells using a baculovirus vector. The cDNA encoding the entire protein, including the mitochondrial targeting sequence, was present in the vector. We isolated a membrane-bound form of the enzyme that has a molecular mass identical with that of the mature porcine protein as determined by SDS/PAGE and has an N-terminal sequence that is identical with that predicted for the mature holoenzyme. These data suggest that the heterologously expressed ETF-QO is targeted to mitochondria and processed to the mature, catalytically active form. The detergent-solubilized protein was purified by ion-exchange and hydroxyapatite chromatography. Absorption and EPR spectroscopy and redox titrations are consistent with the presence of flavin and iron—sulphur centres that are very similar to those in the equivalent porcine and bovine proteins. Additionally, the redox potentials of the two prosthetic groups appear similar to those of the other eukaryotic ETF-QO proteins. The steady-state kinetic constants of human ETF-QO were determined with ubiquinone homologues, a ubiquinone analogue, and with human wild-type ETF and a Paracoccus—human chimaeric ETF as varied substrates. The results demonstrate that this expression system provides sufficient amounts of human ETF-QO to enable crystallization and mechanistic investigations of the iron—sulphur flavoprotein.
Intracorneal vacuoles in skin diseases with parakeratotic hyperkeratosis in the dog: a retrospective light‐microscopy study of 111 cases (1973–2000)
Authors: Senter David A. , Scott Danny W. , Miller William H. , Erb Hollis N.
Published: July 2002

Two recent case reports described a congenital keratinization defect (congenital follicular parakeratosis; CFP) in Rottweiler and Siberian Husky dogs. Skin biopsy specimens revealed marked parakeratosis targeting the hair follicle and numerous intracorneal vacuoles. A retrospective histopathological study was conducted on skin biopsy specimens from 111 dogs with diseases associated with parakeratotic hyperkeratosis to determine whether intracorneal vacuoles were present. Additional criteria evaluated were the size and location of the vacuoles and the degree of parakeratosis. Cases examined included dogs with primary idiopathic seborrhoea, necrolytic migratory erythema (NME),Malasseziadermatitis, zinc‐responsive dermatosis, hereditary nasal hyperkeratosis of Labrador Retriever dogs, thallotoxicosis and CFP. Thirty‐seven cases (37/111, 33%) had intracorneal vacuoles, including nine cases of primary idiopathic seborrhoea (9/29, 31%), 10 cases of NME (10/18, 56%), five cases ofMalasseziadermatitis (5/19, 26%), five cases of zinc‐responsive dermatosis (5/36, 14%), five cases of hereditary nasal hyperkeratosis (5/5, 100%) and three cases of CFP (3/3, 100%). If present, intracorneal vacuoles were found throughout all layers of the parakeratin. The sizes of intracorneal vacuoles varied among diseases, but large (> 5 µm) vacuoles only were present in CFP. Biopsies with a larger degree of parakeratosis were significantly more likely to have intracorneal vacuoles (P = < 0.001). Based on this study, intracorneal vacuoles are a common finding in many parakeratotic skin diseases of the dog, but large (> 5 µm) vacuoles are found only in CFP.
A systematic collaborative overview of randomized trials comparing idarubicin with daunorubicin (or other anthracyclines) as induction therapy for acute myeloid leukaemia
Authors:   T HE AML C OLLABORATIVE G ROUP
Published: July 2002

A collaborative overview, using individual patient data, has been performed to compare idarubicin versus daunorubicin or other anthracyclines, when used with cytosine arabinoside as induction chemotherapy for newly diagnosed acute myeloid leukaemia. There were 1052 patients in five trials versus daunorubicin, 100 in one trial versus doxorubicin, and 745 in one trial versus zorubicin. In the trials of idarubicin versus daunorubicin, early induction failures were similar with the two treatments (20% idarubicin v 18% daunorubicin; P = 0.4), but after day 40 the later induction failures were fewer with idarubicin (17% v 29%; P < 0.0001). Therefore complete remission rates were higher with idarubicin (62% v 53%; P = 0.002). Among remitters, fewer of the patients allocated to idarubicin relapsed (P = 0.008) but slightly more died in remission, leading to a non‐significant benefit (P = 0.07) in disease‐free survival. Overall survival in these five trials was significantly better with idarubicin than with daunorubicin (13% v 9% alive at 5 years; P = 0.03). There was a trend (P = 0.006 for remission rate) for the benefit of idarubicin over daunorubicin to decrease with increasing age. There were no significant differences in outcome in the small trial comparing idarubicin versus doxorubicin, or in the large trial comparing idarubicin versus zorubicin. The induction regimens based on idarubicin achieved, in the particular circumstances of the trials reviewed here, better remission rates and better overall survival than those based on daunorubicin.
Monitoring antimalarial drug resistance within National Malaria Control Programmes: the EANMAT experience
Authors:   The East African Network for Monitoring Antimalarial Treatment (EANMAT)
Published: July 2002

The National Malaria Control Programme (NMCP), organized within the Ministry of Health (MoH), is an essential component for the planning, execution and coordination of malaria control activities. As effective case management remains the mainstay of malaria control in almost every African country, antimalarial drug resistance is a major barrier to the implementation of effective malaria control policies. In order to function effectively, these units must have an efficient surveillance system which can provide reliable and current estimates of the severity of drug resistance. Without this information, it is impossible for the MoH to design and promote a rational antimalarial policy, but because of limited resources, especially of people and expertise, most NMCPs have been unable to initiate and manage such a system. The need for collaborative partnerships between the MoH and the research community prompted the establishment of the East Africa Network for Monitoring Antimalarial Treatment (EANMAT). EANMAT has attempted to bring together the complimentary skills of malaria researchers and MoH staff in four east African countries. After 3 years of operation, data generated by EANMAT have been used to review and modify national malaria treatment policies in Kenya, Uganda, Rwanda and Tanzania. This new approach, which forges a closer working relationship between the research and policy communities, has effectively built capacity around the complex of surveillance, interpretation and use of evidence within a policy environment. The added‐value of this approach is that the research community has learned to appreciate the constraints of policy development, and that the control community has established the need to build capacity and ownership of research evidence. Networks similar to EANMAT should be encouraged elsewhere in Africa to engender similar partnerships: to assist the development of rational treatment policies, and thus more effective malaria chemotherapy leading to significant lowering of malaria morbidity and mortality.
Regulation of cellular retinol‐binding protein type II gene expression by arachidonic acid analogue and 9‐cis retinoic acid in Caco‐2 cells
Authors: Suruga Kazuhito , Mochizuki Kazuki , Suzuki Rie , Goda Toshinao , Takase Sachiko
Published: July 2002

We previously showed that unsaturated fatty acids induced gene expression of cellular retinol‐binding protein type II (CRBPII) in rat jejunum [Suruga, K., Suzuki, R., Goda, T. and Takase, S. (1995) J. Nutr.125, 2039–2044]. In the present study, we investigated this induction mechanism(s) using the human intestinal Caco‐2 cell line. The postconfluent mature Caco‐2 cells were maintained in serum‐free medium containing arachidonic acid or its analogue, 5,8,11,14‐eicosatetraynoic acid (ETYA). Northern blot analysis showed that these compounds induced CRBPII mRNA levels to rise and that this induction was more effective when combined with 9‐cis retinoic acid. This effect was independent of cycloheximide and inhibited by actinomycin D. Nuclear run‐on assays confirmed that the ETYA and 9‐cis retinoic acid‐induced increase of CRBPII mRNA levels was due to an increased rate of transcription of its gene. In Caco‐2 cells, the transcripts of peroxisome proliferator‐activated receptor α (PPARα) and retinoid X receptor α (RXRα), which were activated by their ligands ETYA and 9‐cis retinoic acid, respectively, were coexpressed. The gel shift study using rat CRBPII gene nuclear receptor response elements (RXRE, RE2, RE3) revealed that several forms of nuclear proteins from Caco‐2 cells specifically bound to these elements. Some of these protein/DNA complexes reacted to both anti‐RXRα and anti‐PPAR antibodies. In addition, in‐vitro synthesized RXRα and PPARα cooperatively bound to these elements as a heterodimer and these binding activities were enhanced by addition of ETYA or arachidonic acid but not by addition of 9‐cis retinoic acid. These studies suggest that fatty acid or its analogue may regulate CRBPII gene expression through PPAR/RXR heterodimer bound to the nuclear receptor response element(s) of the CRBPII genes.
Cost‐effectiveness of digital cataract assessment
Authors: Dimock J , Robman L D , McCarty C A , Taylor H R
Published: July 2002

Purpose: The aim of this study was to compare costs of digital photograph grading with that of film‐based, human grading of the lens in epidemiological studies involving cataract assessment.

Methods: Cost‐effectiveness was measured by establishing the number of participants with ungradeable images and incorporating these lost data into the overall cost per participant for each study.

Results: The digital grading system cost was A$105 000 with operating costs of $2.81 per participant, with 99.4% effectiveness. The film‐based, human grading set‐up costs were $43 000 with operating costs of $18.49 per participant and 90% effectiveness. After examining 3500 people the use of the digital equipment becomes cost‐beneficial.

Conclusions: The high costs of setting up a digital cataract grading system are offset by the low running costs, less ungradeable images and greater accuracy over the duration of a large scale ophthalmic epidemiological study.
Of mice, frogs and flies: Generation of membrane asymmetries in early development
Authors: Müller H.‐Arno J.
Published: July 2002

Embryonic development begins with cleavage of the fertilized egg. Cleavage comprises two major processes: cytokinesis and formation of a polarized epithelial cell layer. The focus of this review is comparison of the generation of membrane polarity during embryonic cleavage in three different developmental model systems. In mammalian embryos, as exemplified by analysis of the mouse, generation of distinct membrane domains is uncoupled from cleavage divisions and is initiated in a specific developmental phase, called compaction. In Xenopus laevis embryos, generation of polarized blastomeres occurs simultaneously with cytokinesis. The origin of specific membrane domains of X. laevis polar blastomeres, however, can be traced back to oogenesis. Finally, in Drosophila melanogaster, generation of polarized cells occurs at cellularization. The relevance of cell adhesion, cell junctions and cytocortical scaffolds will be discussed for each of the model systems. Despite enormous morphologic differences, the three models share many common features; in particular, many important molecular interactions are conserved.
Postnatal corticosteroids and sensorineural outcome at 5 years of age
Authors: The Victorian Infant Collaborative Study Group
Published: July 2002

Background: Postnatal corticosteroids reduce ventilator dependence in preterm infants, but possible long‐term benefits for either survival or sensorineural morbidity are not proved.

Aim: The aim of this study was to determine the association between corticosteroid therapy given postnatally and sensorineural outcome in childhood.

Subjects: The subjects comprised 346 consecutive livebirths either of birthweight < 1000 g or with gestational age < 28 weeks born in the state of Victoria during 1991 and 1992, and who survived the first week after birth; 120 (34.7%) were given corticosteroids postnatally.

Results: Of the 120 children who received corticosteroids, 98 (81.7%) survived to 5 years of age, compared with 200 (88.5%) of the 226 children who did not receive corticosteroids. At 5 years of age, survivors treated with corticosteroids postnatally had significantly higher rates of cerebral palsy (corticosteroids 23%, no corticosteroids 4%), blindness (corticosteroids 4%, no corticosteroids 1%) or an intelligence quotient more than one standard deviation below the mean (corticosteroids 54%, no corticosteroids 32%) compared with children not treated with corticosteroids. The rate of sensorineural disabilities imposed by these impairments was significantly higher in children treated with postnatal corticosteroids, and the association between adverse sensorineural outcome and postnatal corticosteroids remained after adjustments for potentially confounding variables. In a separate case‐control analysis of 60 children in each group, the rate of cerebral palsy remained significantly elevated (corticosteroids 22%, no corticosteroids 5%).

Conclusion: Postnatal corticosteroid therapy is associated with substantial adverse sensorineural outcomes at 5 years of age.
Diabetes mellitus secondary to glycogen storage disease type III
Authors: Oki Y. , Okubo M. , Tanaka S. , Nakanishi K. , Kobayashi T. , Murase T.
Published: July 2002

SUMMARY

Background  Diabetes mellitus is a rare complication of glycogen storage disease type III (GSD III).

Case report  We describe a 47‐year‐old man with GSD III who developed diabetes mellitus. He was diagnosed as having GSD III at the age of 18 years, and his glucose tolerance was normal at that time. Liver dysfunction and muscle atrophy gradually progressed, and the patient developed diabetes mellitus at the age of 45. When the post‐prandial hyperglycaemia worsened, we instituted treatment with an alpha‐glucosidase inhibitor, voglibose, and this improved glycaemic control without any adverse effects.

Conclusions  We recommend serial evaluation for complications of GSD III, and propose that an alpha‐glucosidase inhibitor may be a favourable drug in treating diabetes mellitus secondary to GSD III.
Characterization of fcp4 and fcp12, Two Additional Genes Encoding Light Harvesting Proteins of Cyclotella cryptica (Bacillariophyceae) and Phylogenetic Analysis of this Complex Gene Family
Authors: Eppard M. , Krumbein W. E. , von Haeseler A. , Rhiel E.
Published: July 2002

Abstract: Two additional cDNA clones containing genes which encode fucoxanthin chlorophyll a/c binding proteins (Fcps) of the centric diatom Cyclotella cryptica have been sequenced. The first cDNA clone containing fcp12 had an insert size of 871 base pairs (bp). The open reading frame (ORF) of 693 bp corresponds to a precursor protein of 231 amino acids with a molecular weight (Mr) of 25 200. For the mature Fcp12, a protein of 196 amino acids with a Mr of 21 700 is proposed. The second cDNA clone contained the fragmentary fcp4 with an insert of 805 bp. The ORF of 492 bp corresponds to a polypeptide of 164 amino acids with a Mr of 18 050. Phylogenetic analyses revealed that the proteins Fcp1, Fcp2, Fcp3 and Fcp5 are closely related to the Fcps of other diatoms, whereas Fcp6, Fcp7 and Fcp12 share the highest homology to the Fcp of the haptophyte Isochrysis galbana and to the light inducible proteins LI818r3 and LI818 of Chlamydomonas reinhardtii and Chlamydomonas eugametos. The subunit Fcp4 revealed some homology with the red algal LH subunits LhcaR1 and LhcaR2 of Porphyridium cruentum.
Protection from Paraquat‐Mediated Photo‐Oxidative Stress by Glutathione in Poplar (Populus tremula×P. alba) Plants
Authors: Will B. , Jouanin L. , Rennenberg H.
Published: July 2002

Abstract: The sensitivity of hybrid poplar (Populus tremula×P. alba) to oxidative stress mediated by paraquat exposure was analysed with leaf discs from wild‐type plants and plants expressing the bacterial cDNA of the enzymes of glutathione synthesis, namely gshI, encoding γ‐glutamylcysteine synthetase (ECS), or gshII, encoding glutathione synthetase (GS), both in the cytosol. It was expected that leaf discs containing more than 2‐fold elevated glutathione concentrations due to over‐expression of ECS are less susceptible to paraquat exposure than wild‐type plants and transformants over‐expressing GS. However, neither over‐expression of GS nor of ECS improved paraquat tolerance of the leaves. This result was surprising, because in wild‐type plants reduced paraquat sensitivity of young compared with mature leaves coincided with ca. 30 % higher glutathione contents of the young leaves. Apparently, developmental changes in paraquat sensitivity of poplar leaves are controlled by factors different from glutathione contents. Feeding experiments with glutathione and its metabolic precursor γ‐glutamylcysteine (EC) plus gly showed that glutathione can provide protection from paraquat‐mediated photo‐oxidative stress; but at least ca. 5‐fold elevated glutathione levels are required for this effect in poplar leaves. Currently, such high glutathione levels have not been achieved by the application of plant molecular biology techniques. The significance of glutathione for the compensation of photo‐oxidative stress is discussed.
Laser wakefield acceleration and relativistic optical guiding
Authors: Sprangle P. , Esarey E. , Ting A. , Joyce G.
Published: July 2002

An electron acceleration method is investigated which employs a short (τL ∼2πωω−1p ∼1 ps), high-power (P≥1015 W), single frequency laser pulse to generate large amplitude (E≥1 GeV/m) plasma waves (wakefields). At sufficiently high laser powers [P≥17(ω/ωp )2 GW], relativistic optical guiding may be used to prevent the pulse from diffracting within the plasma.
Dynamics of laser-ablated particles from high T
c superconductor YBa2Cu3Oy
Authors: Eryu Osamu , Murakami Kouichi , Masuda Kohzoh , Kasuya Atsuo , Nishina Yuichirô
Published: July 2002

The dynamics of light-emitting particles produced by the excimer laser ablation of the high Tc superconductor YBa2Cu3Oy has been investigated by means of space/time resolved optical measurements near the surface region with a space resolution of 100 μm and a time resolution of 0.1 ns. Two distinct components of ablated particles were observed: one with high average velocities over 5×106 cm/s and the other with slow velocities, depending on laser energy density. The position of the maximum emission intensity in the slower component moved away from the surface and was further delayed from the time of maximum laser intensity as the laser energy density increased. If the incident laser was tilted from the normal of the target surface, the spatial distribution of the luminous plume inclined toward the incident laser beam. These results suggest that the slower component consists of light-emitting particles resulting from the fragmentation of clusters ejected from the surface.
Formation of planar superlattice states in new grid-inserted quantum well structures
Authors: Tanaka Masaaki , Sakaki Hiroyuki
Published: July 2002

We have prepared by molecular beam epitaxy a new type of planar superlattice (PSL), in which an array of periodically spaced AlAs bars of one monolayer (ML) in thickness is inserted in the middle of a GaAs quantum well. This grid-inserted quantum well (GI–QW) is prepared on a misoriented GaAs substrate of 2° off from (001) axis by depositing 0.5 ML of AlAs during the growth of a usual QW. Photoluminescence excitation spectra are measured at 20 K and have shown a clear dependence on the polarization of the excitation light, reflecting the in-plane anisotropy of electronic structures. The measured ratio of electron–heavy hole (e–hh) and electron–light hole (e–lh) transition peaks has shown the polarization dependence, which is in good agreement with theory; this demonstrates that 0.5 ML of AlAs atoms deposited on atomic terraces have formed a periodic potential as intended and given rise to the PSL states in this novel structure.
Generation of 5 THz repetition optical pulses by modulation instability in optical fibers
Authors: Sudo S. , Itoh H. , Okamoto K. , Kubodera K.
Published: July 2002

5 THz repetition rate optical pulses have been achieved with modulation instability in an optical fiber. The detailed investigation on the relationship between fiber anomalous dispersion and modulation frequency enables high repetition rate optical pulses, yielding a control method of pulse repetition rate.
Unpinned gallium oxide/GaAs interface by hydrogen and nitrogen surface plasma treatment
Authors: Callegari A. , Hoh P. D. , Buchanan D. A. , Lacey D.
Published: July 2002

The Fermi level at the Ga oxide/GaAs interface has been unpinned by rf plasma cleaning the GaAs surface in H2 and N2. Following plasma cleaning, a Ga oxide film is reactively electron beam deposited onto the substrate. Metal-oxide-semiconductor (MOS) capacitors fabricated on these structures show good high-frequency capacitance-voltage characteristics. This indicates that the density of interface states has been reduced to ∼1011 eV−1 cm−2. The MOS capacitors are found to be stable in air after several months.
Doped surfaces in one sun, point-contact solar cells
Authors: King R. R. , Sinton R. A. , Swanson R. M.
Published: July 2002

This letter reports two new types of large-area (>8.5 cm2), backside, point-contact solar cells with doped surfaces, designed for use in unconcentrated sunlight. One type was fabricated on an intrinsic substrate with an optimized phosphorus diffusion on the sunward surface. The apertured-area efficiency was independently measured to be 22.3% at 1 sun (0.100 W/cm2), 25 °C, the highest reported for a silicon solar cell. The other type is constructed on a doped substrate, and has an apertured-area efficiency of 20.9%, the highest reported for a point-contact solar cell with a base in low-level injection. Both cells have record open-circuit voltages above 700 mV.
Synthesis of high-density Ba1−xKxBiO3 superconducting samples
Authors: Hinks D. G. , Mitchell A. W. , Zheng Y. , Richards D. R. , Dabrowski B.
Published: July 2002

A synthesis procedure for producing high-density Ba1−xKxBiO3 has been developed. A novel melt-processing technique is described which yields strong, near 100% dense superconducting material. This material is much more amenable to experimental study than the powder samples produced by the previous synthesis methods.
Electron beam excitation of rare-gas alkali ionic excimers
Authors: Millar P. S. , Warwar G. , Wisoff P. J. , Sauerbrey R. , Balasubramanian K.
Published: July 2002

The observation of fluorescence from ionic rare-gas alkali molecules excited by an electron beam is reported. Gas mixtures of argon and xenon with hot vapors of either rubidium or cesium were excited to obtain emission from (XeRb)+ at 164 nm and (XeCs)+ at 160 nm. The spectral features observed in (XeRb)+ are assigned to three upper electronic states.
Elementary formula for the magneto-optic Kerr effect from model superlattices
Authors: Zak J. , Moog E. R. , Liu C. , Bader S. D.
Published: July 2002

An elementary formula is derived for the magneto-optic Kerr effect from model superlattices. An exact result is obtained for the case of equal refractive indices for the two constituents of the superlattice. Co/Pt is used as an example of such superlattices for wavelengths in the vicinity of 2 eV. First-order corrections in the difference of the refractive indices are derived which are suitable for treating a variety of materials.
Micromachined silicon tunnel sensor for motion detection
Authors: Kenny T. W. , Waltman S. B. , Reynolds J. K. , Kaiser W. J.
Published: July 2002

We have used the extreme sensitivity of electron tunneling to variations in electrode separation to construct a novel, compact displacement transducer. Electrostatic forces are used to control the separation between the tunneling electrodes, thereby eliminating the need for piezoelectric actuators. The entire structure is composed of micromachined silicon single crystals, including a folded cantilever spring and a tip. Measurements of displacement sensitivity and noise are reported. This device offers a substantial improvement over conventional technology for applications which require compact, highly sensitive transducers.
Experimental verification of a form-birefringent polarization splitter
Authors: Shiraishi K. , Sato T. , Kawakami S.
Published: July 2002

Experimental verification is made of a new polarization splitter which utilizes artificial anisotropic dielectrics. The splitter is composed of layers of periodically laminated SiO2/TiO2 thin films. The SiO2 and TiO2 films are alternately deposited by rf sputtering and reactive dc sputtering, respectively. The thickness of each layer is 50 nm, while the total number of the layers amounts to 2000. The measured polarization split angles are 5.7° (λ=0.63 μm) and 5.1° (λ=1.3 μm), being roughly the same as those predicted.
Continuously tunable, injection-seeded β-barium borate optical parametric oscillator: Spectroscopic applications
Authors: Haub J. G. , Johnson M. J. , Orr B. J. , Wallenstein R.
Published: July 2002

Simple spectroscopic control of a β-barium borate optical parametric oscillator is achieved by seeding at its visible signal wavelength with light from a tunable pulsed dye laser. This yields continuously tunable narrowband infrared output at the corresponding idler wavelength. The spectroscopic potential of this device is demonstrated by recording photoacoustic spectra of the near-infrared (ν1+2ν3+ν51) band of acetylene gas.
Real time diagnostics of detonation products from lead azide using coherent anti-Stokes Raman scattering
Authors: Grisch F. , Péalat M. , Bouchardy P. , Taran J. P. , Bar I. , Heflinger D. , Rosenwaks S.
Published: July 2002

We report on the first example that applies coherent anti-Stokes Raman scattering (CARS) to real time diagnostics of detonation products from a solid explosive. The supersonically expanding gaseous products, from the detonation of either lead azide pellets or powders, are studied, using broadband CARS. The density, and the rotational and vibrational temperatures of ground electronic state N2 molecules, N2(X), are monitored as a function of time at a fixed distance, 3.3 cm, from the azide surface. The rotational temperature is low, around 200–300 K, while the vibrational temperature is around 2000 K for delays of 8–12 μs, following the initiation of detonation. The density of N2(X), during this time interval, increases from ∼1×1017 to 1×1018 cm−3.
Nucleation of diamond films on surfaces using carbon clusters
Authors: Meilunas R. J. , Chang R. P. H. , Liu Shengzhong , Kappes Manfred M.
Published: July 2002

A unique method for nucleating diamond films on surfaces using C clusters is described. The process substitutes the need for diamond polish pretreatment of substrates prior to diamond film growth, as currently practiced in low-pressure (<1 atm) chemical vapor deposition methods. As an example, the use of C clusters C60 and C70 as nucleating layers on single-crystal Si surfaces is presented. It is shown that a thin layer (approximately 1000 Å) of pure carbon C70 is sufficient for the nucleation and growth of fine grain polycrystalline diamond films. The enhancement of nucleation by the C70 layer is nearly ten orders of magnitude over an untreated Si surface. It also follows that C clusters can be used as a one-step lithographic template for growing diamond on selected regions of the substrate. In addition, insight into the mechanism for diamond nucleation from C clusters is given.
Optical strip waveguides in KNbO3 formed by He ion implantation
Authors: Fluck D. , Günter P. , Irmscher R. , Buchal Ch.
Published: July 2002

Permanent optical strip waveguides in single crystals of KNbO3 were produced with MeV He ion implantation. Guided TE00 modes were observed and the propagation losses were characterized at the wavelengths of 514, 632, and 860 nm. Waveguide propagation losses of 1.4 dB/cm were measured at 632 nm.
Intersite Coulomb repulsion and intrasite attraction for DX centers in GaAs
Authors: Monroe Don
Published: July 2002

The observed mobility increase in n-GaAs under hydrostatic pressure has been argued to favor a neutral DX center, since the pressure-induced electron-density reduction is then offset by reduced charged-center scattering. We show that the observations instead favor the negative-U model for DX: spatial correlations between the resulting negative and positive charges smooth the potential fluctuations and enhance the mobility.
Phase-matched second-harmonic generation in novel corona poled glass waveguides
Authors: Okada A. , Ishii K. , Mito K. , Sasaki K.
Published: July 2002

Second-order optical nonlinearity χ(2) is induced in glass films by corona poling. The glass films are fabricated by radio-frequency sputtering Corning7059 onto Pyrex glass substrates. The values of second-order nonlinear coefficient d33 of the corona-poled glass films are estimated to be ∼0.5 pm/V. Using the corona-poled glass films as a waveguide, phase-matched second-harmonic generation has been demonstrated in the glass films for the first time. The origin of the χ(2) is considered to be related to the defects in the glass films.
Improved laser-ablated thin films of NdCeCuO by use of N2O
Authors: Kussmaul A. , Moodera J. S. , Tedrow P. M. , Gupta A.
Published: July 2002

Thin films of the electron-doped superconductor Nd1.85Ce0.15CuO4−δ were prepared by laser ablation in O2 and N2O ambients. Although films prepared in an O2 ambient need to be reduced to become superconducting, the use of a lower oxygen pressure during deposition produces inferior films. A more metallic character can be obtained by increasing the O2 pressure during deposition. The substitution of N2O for O2 results in films that are superconducting without a separate reduction step, with a sharp transition at about 16 K. A short vacuum anneal at the deposition temperature yields reproducible films with Tc=20 K, without change in the transition width.
Hydride vapor phase epitaxial growth of a high quality GaN film using a ZnO buffer layer
Authors: Detchprohm T. , Hiramatsu K. , Amano H. , Akasaki I.
Published: July 2002

In hydride vapor phase epitaxial (HVPE) growth of GaN, the sputtered ZnO layer has been found to be one of the best buffer layers because of the fact that physical properties of ZnO are nearly analogous with those of GaN. With a ZnO buffer layer, the reproducibility of growing GaN single crystal by HVPE has been greatly improved. The GaN films grown by this method show excellent crystalline, electrical, and optical properties. In particular, the Hall mobility of 1920 cm2 V−1 s−1 at 120 K is the highest value that has ever been reported by HVPE.
Temperature dependence of the radiative lifetime in porous silicon
Authors: ’t Hooft G. W. , Kessener Y. A. R. R. , Rikken G. L. J. A. , Venhuizen A. H. J.
Published: July 2002

Using photoluminescence decay measurements the radiative lifetime of porous silicon is investigated between liquid helium and room temperature. The radiative recombination mechanism in porous silicon is in essence the same as in bulk silicon, viz. a phonon mediated indirect transition. The functional dependence of the lifetime on photon energy reveals the confinement character of the recombination carriers. The high external photoluminescence efficiency is well explained by the reduction of nonradiative recombination owing to low mobility, to low dimensionality, and to the extreme low surface recombination rate, and is further enhanced by the relatively small refractive index.
Limitations of magnetoresistive sensors based on the giant magnetoresistive effect in granular magnetic composites
Authors: Hylton T. L.
Published: July 2002

The giant magnetoresistive effect recently observed in thin film composites of ferromagnetic particles imbedded in a nonmagnetic metallic matrix offers the possibility that new magnetoresistive sensors can be fabricated using these structures. Here we consider the effects of particle size and shape, magnetocrystalline anisotropy and temperature on the performance and sensitivity of such devices. For the sensitivity required in read elements of high-performance magnetic heads, severe constraints on the choice of ferromagnetic material and particle size and shape are required.
Novel mechanism for high speed growth of transparent and conducting tin oxide thin films by spray pyrolysis
Authors: Kameswara Rao L. , Vinni V.
Published: July 2002

A novel mechanism is proposed for efficient manipulation of transport forces acting on the droplets during spray pyrolytic deposition of thin films. A ‘‘burst mode’’ technique of spraying is used to adjust the deposition conditions so as to transport the droplets under the new mechanism. Transparent, conducting thin films of undoped tin oxide prepared by this method showed significant improvement in growth rate. The films are found to be of fairly good quality with optical transmission of 82% and sheet resistance of 35 Ω/⧠. The films are chemically homogeneous and grow preferentially along 〈200〉 direction.
X-ray photoelectron spectroscopy measurement of valence-band offsets for Mg-based semiconductor compounds
Authors: Wang M. W. , Swenberg J. F. , Phillips M. C. , Yu E. T. , McCaldin J. O. , Grant R. W. , McGill T. C.
Published: July 2002

We have used x-ray photoelectron spectroscopy to measure the valence-band offsets for the lattice matched MgSe/Cd0.54Zn0.46Se and MgTe/Cd0.88Zn0.12Te heterojunctions grown by molecular beam epitaxy. By measuring core level to valence-band maxima and core level to core level binding energy separations, we obtain values of 0.56±0.07 eV and 0.43±0.11 eV for the valence-band offsets of MgSe/Cd0.54Zn0.46Se and MgTe/Cd0.88Zn0.12Te, respectively. Both of these values deviate from the common anion rule, as may be expected given the unoccupied cation d orbitals in Mg. Application of our results to the design of current II-VI wide band-gap light emitters is discussed.
Estimating oxide-trap, interface-trap, and border-trap charge densities in metal-oxide-semiconductor transistors
Authors: Fleetwood D. M. , Shaneyfelt M. R. , Schwank J. R.
Published: July 2002

A simple method is described that combines conventional threshold-voltage and charge-pumping measurements on n- and p-channel metal-oxide-semiconductor (MOS) transistors to estimate radiation-induced oxide-, interface-, and border-trap charge densities. In some devices, densities of border traps (near-interfacial oxide traps that exchange charge with the underlying Si) approach or exceed the density of interface traps, emphasizing the need to distinguish border-trap contributions to MOS radiation response and long-term reliability from interface-trap contributions. Estimates of border-trap charge densities obtained via this new dual-transistor technique agree well with trap densities inferred from 1/f noise measurements for transistors with varying channel length.
A new approach for synthesizing Ge quantum crystallites embedded in a-SiNx films
Authors: Qu X.-X. , Chen K.-J. , Huang X.-F. , Li Z.-F. , Feng D.
Published: July 2002

In this letter, we present a new approach for synthesizing Ge quantum crystallites embedded in a-SiNx films. On the basis of preferential chemical bonding formation of Si-N and Ge-Ge, thin films with Ge clusters embedded in a-SiNx matrix have been prepared by the plasma enhanced chemical vapor deposition method with reactant gases of SiH4, GeH4 and NH3 mixed in hydrogen plasma at substrate temperature of 250 °C. Then the as-deposited films were annealed at 800 °C for 30 min in the vacuum for the crystallization of Ge clusters and the growth of nanometer-sized Ge quantum crystallites. These samples were characterized by infrared absorption spectra, transmission electron microscopy, x-ray diffraction, and Raman scattering spectra. The average size of Ge crystallites was found to be about 200 Å. By choosing conditions of the deposition and thermal-annealing treatment, the size of Ge quantum crystallites can be prepared in a controlled manner.
Submicrometer resonant tunnelling diodes fabricated by photolithography and selective wet etching
Authors: Wang J. , Beton P. H. , Mori N. , Buhmann H. , Mansouri L. , Eaves L. , Main P. C. , Foster T. J. , Henini M.
Published: July 2002

A new process based on photolithography and selective wet etching has been used to fabricate small area resonant tunnelling diodes. The low-temperature current-voltage (I-V) characteristics of diodes with conducting widths less than 0.1 μm show additional peaks due to 1D lateral quantum confinement. We observe a pronounced asymmetry in I-V which we explain in terms of tunnelling from emitter states which have a different degree of lateral quantum confinement.
Growth and superconductivity of c-axis in-plane aligned YBa2Cu3O7−x films fabricated by the self-template method
Authors: Mahajan S. , Wen J. G. , Ito W. , Yoshida Y. , Kubota N. , Liu C.-J. , Morishita T.
Published: July 2002

In-plane aligned a-axis oriented and [110] oriented Y1Ba2Cu3O7−x (YBCO) films exhibiting different anisotropic ratio in resistivity were fabricated, respectively, on LaSrGaO4[100] and SrTiO3[110] substrates by the self-template method. The anisotropic properties of the a-axis films as studied by resistivity and thermoelectric power measurements are believed to reflect the anisotropy intrinsic to the YBCO system. The measured anisotropic properties of the a-axis films exhibiting anisotropy ratio ≳8 in resistivity and of the as-deposited [110] films were found to be related to cracks and the rough surface of these films. Furthermore, high-resolution microscopy revealed that a-axis film growth by our self-template method is dependent on the kinetics of the deposition process.
Simulation of wear in overhead current collection systems
Authors: Klapas D. , Benson F. A. , Hackam R.
Published: July 2002

Apparatus have been designed to simulate the wear from conductors in a railway current collection system. The main features of the wear machine include a continuous monitoring of the strip wear, strip traversing, and dwell-time test facilities for the investigation of oxidational wear on a copper disk, simulating the contact wire. Disk wear is measured in situ by the spherical indentations method. Typical results of the specific wear rate are also presented to demonstrate the capability of the apparatus.
Characteristics of a piezoelectric pulsed nozzle beam
Authors: Andresen P. , Faubel M. , Haeusler D. , Kraft G. , Luelf H.-W. , Skofronick J. G.
Published: July 2002

The characteristics of a molecular beam from a piezoelectric pulsed nozzle source are given and, where appropriate, compared to a continuous beam. These include variation during the pulse in the relative intensity and speed ratio for the gases He, Ar, Ne, and N2. The measurements were made by standard time-of-flight and laser-induced fluorescence techniques. For gas valve pulses of time duration less than 500 μs, there was a single peak during which the gases reached continuum steady flow behavior. Typical speed ratios (parallel temperatures) for the gases He, Ar, Ne, and N2 were 19, 34, 34, and 20 (2.1, 0.7, 0.7, and 1.9 K), respectively. These values are comparable to those from a continuous source with equivalent values of p0d, the product of source pressure and nozzle diameter. The dimer concentrations for Ne and Ar were also measured and found to be 0.4% and 0.7%, respectively. A major problem with the valve was its inability to open fully because of the limited motion of the piezoelectric element.
Beam depletion method for measuring velocity distributions of cluster beams
Authors: Vollmer Michael , Selby Kathy , Kresin Vitaly , Masui Jun , Kruger Michael , Knight W. D.
Published: July 2002

A simple method to investigate the velocity distributions of cluster beams is presented. Following photon absorption, excited clusters are removed from the beam. This results in a reduced signal at the detector. Using time-resolved detection, all the parameters of the velocity distribution can be extracted from the signal shape. The technique is demonstrated for a neutral sodium cluster beam. An analytical calculation of the signal shape is in excellent agreement with the data.