bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of glucagon on insulin receptor substrate‐1 (IRS‐1) phosphorylation and association with phosphatidylinositol 3‐kinase (PI 3‐kinase)
Authors: Saad Mario J.A. , Hartmann Luiz G.C. , de Carvalho Daniela S. , Galoro Cesar A.O. , Brenelli Sigisfredo L. , Carvalho Carla R.O.
Published: July 2002

In the present study we have examined the levels and phosphorylation state of the insulin receptor and insulin receptor substrate 1 (IRS‐1) as well as the association between IRS‐1 and phosphatidylinositol 3‐kinase (PI 3‐kinase) in the liver and muscle of rats treated with glucagon. There was a decrease in the insulin‐stimulated receptor and IRS‐1 phosphorylation levels which was paralleled by a reduced association between IRS‐1 and PI 3‐kinase in vivo in the liver and muscle of glucagon‐treated rats. These observations suggest that glucagon, probably acting through cAMP, may impair insulin signaling in the three early steps in insulin action after binding.
Proteins in the early Golgi compartment of Saccharomyces cerevisiae immunoisolated by Sed5p
Authors: Cho Jung-Hwa , Noda Yoichi , Yoda Koji
Published: July 2002

The yeast tSNARE Sed5p is considered to mainly reside in the early Golgi compartment at the steady state of its intracellular cycling. To better understand this compartment, we immunoisolated a membrane subfraction having Sed5p on the surface (the Sed5 vesicles). Immunoblot studies showed that considerable portions (20–30%) of the Golgi mannosyltransferases (Mnt1p, Van1p, and Mnn9p) were simultaneously recovered while the late Golgi (Kex2p) or endoplasmic reticulum (Sec71p) proteins were almost excluded. The N‐terminal sequences of the polypeptides detectable by Coomassie blue staining indicated that the prominent components of the Sed5 vesicles include Anp1p, Emp24p, Erv25p, Erp1p, Ypt52p, and a putative membrane protein of unknown function (Yml067c).
Molecular characterization of a calmodulin‐like Dictyostelium protein CalB
Authors: Rösel Daniel , Půta František , Blahůšková Anna , Smýkal Petr , Folk Petr
Published: July 2002

A gene named calB was cloned and characterized in Dictyostelium. A relationship to calmodulin (CaM) is suggested by sequence identity (50%), similar exon–intron structure and cross‐reactivity with anti‐CaM sera. The level of calB mRNA is developmentally regulated with maxima during aggregation and in spores. CalB null cells grow normally, develop and produce viable spores. We demonstrated the capacity of tagged CalB to bind Ca2+ using the 45Ca2+ overlay assay and showed that its mobility on SDS–PAGE is dependent on Ca2+/EGTA pretreatment.
Mechanical Deformation of Compressible Chromatographic Columns
Authors: Keener R. N. , Maneval J. E. , Östergren K. C. E. , Fernandez E. J.
Published: July 2002

A one‐dimensional model of mechanical deformation of compressible chromatography columns is presented. The model is based on linear elasticity and continuum mechanics and is compared to a more complete two‐dimensional model and one‐dimensional porosity profiles measured by NMR imaging methods. The model provides a quantitative description of compression and the effects of wall support during scale‐up. A simple criterion for the significance of wall support as a function of both diameter and length is also developed. Although the model accounts only for mechanical deformation, flow compression can be included, and validation presented here suggests that a more complete model may be valuable for anticipating the effects of scale and aspect ratio on pressure‐flow behavior of compressible columns.
Three novel small deletion mutations of the LDL receptor gene in Korean patients with familial hypercholesterolemia
Authors: Chae Jae Jin , Kim Sung Han , Kim Un Kyung , Han Ki‐Hoon , Kim Hyo‐Soo , Kastner Daniel L. , Namkoong Yong , Park Young‐Bae , Lee Chung Choo
Published: July 2002

The low‐density lipoprotein (LDL) receptor gene from 80 unrelated Korean patients with familial hypercholesterolemia (FH) was analyzed to screen for small structural rearrangements that could not be detected by Southern blot hybridization. Three different small deletions were detected in exon 11 of 3 FH patients and were characterized by DNA sequence analysis. Of them two mutations are in‐frame 36‐bp (FH 2) and 9‐bp (FH 34) deletions that result in the loss of twelve amino acids (from Met510 to Ile521) and three amino acids (Thr513, Asp514 and Trp515), respectively. Both mutations are located in the third of the five YWTD motifs of the LDL receptor gene. The third mutation (FH 400) is a 2‐bp deletion that shifts the translational reading frame and results in a prematurely terminated receptor protein. The generation of a 36‐bp deletion can be explained by the formation of a hairpin‐loop structure mediated by inverted repeat sequences. On the other hand, the mechanism responsible for the 9‐ and the 2‐bp deletions is probably strand‐slippage mispairing mediated by short direct repeats. All of these three deletions are novel mutations. Each of the three deletions was detected only in a single pedigree out of 80 FH families analyzed.
The p55 tumour necrosis factor receptor TNFR1 contains a trans-Golgi network localization signal in the C-terminal region of its cytoplasmic tail
Authors: STOREY Helen , STEWART Abigail , VANDENABEELE Peter , LUZIO J. Paul
Published: July 2002

It has been reported in some human cells that, in addition to a plasma membrane localization, members of the tumour necrosis factor receptor superfamily may be localized to the Golgi complex. We have shown by immunofluorescence and immunoelectron microscopy that the p55 tumour necrosis factor receptor, TNFR1, is principally localized to the trans-Golgi network in the human breast carcinoma cell line, MCF7. Chimaeras consisting of the extracellular and transmembrane domains of CD8 together with the cytoplasmic tail of TNFR1 were targeted to the trans-Golgi network in stably transfected rat fibroblastic cells. Deletions in the cytoplasmic tails of these chimaeras demonstrated the requirement for the C-terminal sequence of 23 amino acids for this targeting. The 23 amino acid sequence is mostly outside the death domain and contains both an acid patch and a dileucine motif. Interaction of this sequence with membrane traffic adaptor proteins may play an important role in controlling the responses of cells to tumour necrosis factor, since binding of signalling adaptor proteins has only been demonstrated for plasma membrane, and not Golgi-localized, TNFR1.
Comparative structure analysis of proteinase inhibitors from the desert locust,Schistocerca gregaria
Authors: Gáspári Zoltán , Patthy András , Gráf László , Perczel András
Published: July 2002

The solution structure of three small serine proteinase inhibitors, two natural and one engineered protein, SGCI␣(Schistocerca gregariachymotrypsin inhibitor), SGCI[L30R, K31M] and SGTI (Schistocerca gregariatrypsin inhibitor), were determined by homonuclear NMR‐spectroscopy. The molecules exhibit different specificities towards target proteinases, where SGCI is a good chymotrypsin inhibitor, its mutant is a potent trypsin inhibitor, and SGTI inhibits both proteinases weakly. Interestingly, SGTI is a much better inhibitor of insect proteinases than of the mammalian ones used in common assays. All three molecules have a similar fold composed from three antiparallel β‐pleated sheets with three disulfide bridges. The proteinase binding loop has a somewhat distinct geometry in all three peptides. Moreover, the stabilization of the structure is different in SGCI and SGTI. Proton–deuterium exchange experiments are indicative of a highly rigid core in SGTI but not in SGCI. We suggest that the observed structural properties play a significant role in the specificity of these inhibitors.
Multicolour spectral karyotyping identifies new translocations and a recurring pathway for chromosome loss in multiple myeloma
Authors: Sawyer Jeffrey R. , Lukacs Janet L. , Thomas Edward L. , Swanson Charles M. , Goosen Linda S. , Sammartino Gael , Gilliland John C. , Munshi Nikhil C. , Tricot Guido , Shaughnessy John D. , Barlogie Bart
Published: July 2002

Multicolour spectral karyotyping (SKY) was performed on primary tumour specimens from 100 patients with multiple myeloma (MM) that showed complex clonal chromosome aberrations not fully characterized by G‐banding. In this study, SKY was able to identify or revise translocations with breakpoints involving 14q32, 11q13 or 8q24 in 32 patients (32%). Five new recurring translocations were identified, two of which involved chromosome 22. A subtle reciprocal translocation t(14;22) (q32;q11∼12) was identified using SKY in two patients and a second, much larger, translocation t(11;22)(q13;q13) was identified using G‐banding in three patients. A third new translocation was identified in two patients using SKY and G‐banding as der(7)t(7;7)(p15∼22;q22∼32). Twenty‐three patients (23%) showed the loss of 8p by whole‐arm translocations with different whole‐arm donor chromosomes. Among this group, two new recurring whole‐arm translocations involving the centromeric breakpoint 8q10 were identified as der(8;20)(q10;q10) and der(8;18) (q10;q10) in three patients each. In addition, a novel pattern of three‐way translocations involving the clonal evolution of the t(8;22)(q24;q11) by the subsequent loss of 8p by whole‐arm translocations was found in three patients. The chromosome instability identified here demonstrates that the loss of 8p can occur by multiple whole‐arm translocations, indicating a new pathway for the loss of a specific chromosome region in MM.
Laboratory investigations into the threshold of movement of natural sand‐sized sediments under unidirectional, oscillatory and combined flows
Authors: Paphitis D. , Velegrakis A. F. , Collins M. B. , Muirhead A.
Published: July 2002

The threshold of movement of sediment obtained from sandbanks within the Bristol Channel (UK) is investigated under unidirectional, oscillatory and combined flows. The experiments were undertaken in a recirculating, unidirectional laboratory flume containing an oscillating plate to simulate wave action, with movement along the same axis as the unidirectional flows. The sand samples consisted of cohesionless quartz grains with median grain sizes between 0·315 and 0·513 mm. The experiments were performed under flow velocities (measured at 2 cm above the bed) ranging between 0 and 24 cm s–1 and oscillatory currents (wave periods of 5, 12 and 15 s) ranging from 0 to 28 cm s–1. The critical conditions for the initiation of sediment movement were assessed, by visual observation, using the Yalin criterion. The results show that, under unidirectional flow, there is a slight overestimation of the threshold of naturally graded sediments derived on the basis of empirically derived threshold curves for artificially prepared sediments under similar flow conditions. In the case of oscillatory flows, the threshold for the natural sands is found to be higher than that predicted by previously derived empirical curves. Under combined flows, wave period is shown to control threshold conditions, with the unidirectional and oscillatory flow components combining in a linear fashion for long‐period (12 s and 15 s) waves. In contrast, in the presence of short‐period (5 s) waves, the unidirectional and oscillatory components of the flow appear to ‘decouple’. For high orbital velocities, in both cases, the effect of the wave period on threshold diminishes.
p53 autoantibodies in patients with urological tumours
Authors: Lang  , Unteregger  , Kartarius  , GÜnther  , Bonkhoff  , Montenarh  , Zwergel
Published: July 2002

Objective

 To determine the presence of p53 serum antibodies in patients with clinically well‐defined urological cancer using a new enzyme‐linked immunosorbent assay (ELISA).

Patients and methods

 The study included 73 patients with prostatic cancer, 72 with transitional cell carcinoma of the urinary tract, 37 with renal cell cancer and 16 controls with a benign disease, all of whom were tested using the ELISA for p53 autoantibodies. The specific reaction of the ELISA (positive p53 antibody titre) was confirmed by Western Blot analysis.

Results

 Thirteen patients with cancer and one control patient (7.6% overall) were positive for p53 autoantibodies. The sensitivity of the test was low, whereas the specificity was remarkably high. Surprisingly, 9 of the 13 p53‐positive patients died within a median of 3.7 months (range 2–6) and the one positive control patient died of undetected lung cancer. There was no significant correlation of p53 antibody positivity with clinical stage or tumour‐specific differences.

Conclusions

 The expression of p53 autoantibody seems to be a very late but significant event in urological tumour development, with the worst outcome (tumour‐specific death) within a few weeks of developing positivity. In histopathologically heterogeneous tumour entities, p53 autoantibodies might be independent prognostic factors in patients with urological cancers.
Type 1 diabetes mellitus in Czech children diagnosed in 1990–1997: a significant increase in incidence and male predominance in the age group 0–4 years
Authors: Cinek O. , Lánská V. , Koloušková S. , Šumník Z. , Šnajderová M. , Rønningen K. S. , Vavrinec J. ,   collaborators of the Czech Childhood Diabetes Registry
Published: July 2002

Aims To overview total, age‐and sex‐specific incidence rates of type 1 diabetes mellitus and their trends in Czech children 0–14 years of age in the period of 1990–1997.

Methods Type 1 DM cases were ascertained by two independent sources, data of general population were obtained from the annual demographic reports of the State Statistic Bureau. Incidence rates were computed using both ascertainment sources combined.

Results In the study period 1.1.1990–31.12.1997, the total incidence was 10.1 (95% CI 9.6–10.6) per 100 000/year in both sexes, 10.0 (95% CI 9.4–10.7) in boys, and 10.2 (95% CI 9.5–11.0) in girls. The total age‐standardized incidence was 9.9 (95% CI 9.4–10.4). The total incidence had a significant increasing trend over the study period (P = 10−4, annual increment 4.3%). A significant increasing trend was also found in the groups of children 0–4 (P = 0.033, increment 6.9%) and 5–9 years at diagnosis (P = 0.038, increment 4.8%). Statistically significant male predominance was observed in the group diagnosed at age 0–4 years (boys/girls ratio of incidence 1.33, P = 0.035).

Conclusions We report the first population‐based epidemiological data on incidence of childhood Type 1 DM in the Czech Republic. The incidence has increased significantly during the last 8 years. The present incidence is at an intermediate level compared to other European countries.
Bilateral optic atrophy following diabetic ketoacidosis
Authors: Song S. H. , Mowbray A. , O'Shea H. , Campbell I. W.
Published: July 2002

Diabetic ketoacidosis (DKA) can result in neuropathic abnormalities of the somatic and the autonomous nervous systems. We report the case of a 50‐year‐old man with Type 1 diabetes of 20‐year duration who after severe DKA lost vision in his right eye and only retain partial vision in his left. This case demonstrates that optic neural tissue is vunerable to haemodynamic and metabolic complications of DKA.
Low birthweight and metabolic abnormalities in twins with increased susceptibility to Type 2 diabetes mellitus
Authors: Bo S. , Cavallo‐Perin P. , Scaglione L. , Ciccone G. , Pagano G.
Published: July 2002

Aims To evaluate the role of environmental intra‐uterine factors in determining the birthweights of twins with increased susceptibility to diabetes and discordant for abnormal responses to the oral glucose tolerance test (OGTT) and verify the possible association of within‐pair birthweight differences and metabolic abnormalities in adult life.

Methods Forty‐six monozygotic (MZ) and 32 dizygotic (DZ) twins were enrolled; 13 MZ twins were discordant for impaired glucose tolerance (IGT) and/or hyperinsulinaemia compared to their co‐twins.

Results The 13 MZ discordant twins showed significantly lower birthweights than their normal co‐twins (P < 0.001). When dividing all twins in those with the highest birthweights within the couple and those with the lowest, all subjects with abnormal OGTT were found in the latter group (P < 0.0001). Within‐pair birthweight difference was significantly higher in MZ twins with abnormal OGTT and the metabolic syndrome compared to normal MZ twins. The relative risk of developing the metabolic syndrome was 8.7 (1.6–46.9) when comparing the higher tertile of within‐pair birthweight differences ( 0.450 kg) to the two lower tertiles (< 0.450 kg). Logistic regression analysis confirmed within‐pair birthweight difference as a significant predictor of abnormal responses to the OGTT and the metabolic syndrome.

Conclusions These data suggest a causative role for environmental intra‐uterine factors on the determination of birthweight and support the hypothesis that within‐pair birthweight difference, rather than an absolute low birthweight, is responsible for the metabolic abnormalities in the adult life.
Positive predictive value of optometrist‐initiated referrals for glaucoma
Authors: Theodossiades Julia , Murdoch Ian
Published: July 2002

A study was conducted at the Moorfields Community Eye Clinic at Ealing Hospital to determine the positive predictive value (ppv) of optometric referrals for suspected glaucoma. The information reported in the referrals and the reasons given for referral were also assessed and evaluated in relation to the ppv. Information was gathered through prospective analysis of patient clinic notes. Ninety patients were referred over a six‐month period of which 87 fulfilled the inclusion criteria. The optometrist referral letters for 79 of these patients were supplied by the GP. Results indicate a ppv of 0.43. The reason for referral in the majority of cases (48%) was raised IOP alone. However the most frequently reported mode of practice was a combination of disc and IOP assessment (57%). In line with other research our study demonstrates that referral accuracy improves as the number of suspicious findings increases. In addition those referrals reporting all three tests (IOP measurement, optic disc assessment and perimetry) are shown to have the highest ppv.
Smoking and lens optical density
Authors: Hammond Billy R. , Wooten Billy R. , Náñez José E. , Wenzel Adam J.
Published: July 2002

Epidemiological evidence indicates that smoking increases the risk of age‐related cataract. No information is currently available, however, on the effects of smoking on the lens prior to cataract development. In this study, we relate smoking behavior to lens optical density (OD) in younger individuals without frank cataract. Fifty three never smokers and 41 current smokers were compared directly. Thirty one past smokers were tested to examine the relationship between years since smoking cessation and lens OD. Lens OD was measured psychophysically by comparing scotopic thresholds obtained at 410 (measuring) and 550 nm (reference). Stimuli were presented in Maxwellian view. The smokers in the sample smoked an average of 17.3+/−11.3 cigarettes/day for 20.4+/−12 years. No significant differences (other than in fat intake) were found between the smokers and nonsmokers in iris color, dietary patterns, or age. Despite their overall similarity, lens OD was significantly (p=0.005) higher in the smokers. Moreover, we found a significant dose–response relationship (p=0.02) between smoking frequency and lens OD. There was also a weak relationship between smoking frequency and lens OD for past smokers (p=0.06), but no relationship between lens OD and years since smoking cessation. Our data indicate that smoking is directly related to age‐related increases in lens OD throughout life and that these increases persist even after smoking cessation.
Health Outcomes and Medicaid Costs for Frail Older Individuals: A Case Study of a MCO Versus Fee‐for‐Service Care
Authors: Burton Lynda C. , Weiner Jonathan P. , Stevens Gregory D. , Kasper Judith
Published: July 2002

Older individuals receiving both Medicare and Medicaid benefits are known to have a disproportionate burden of illness and high medical care costs. Elder Health, Inc., a private, for‐profit managed care organization operating in Maryland under capitation rates from both Medicare and Medicaid, has tailored a medical practice to these individuals, with the stated objective of providing integrated care. This study compared 200 Elder Health patients with a closely matched group of dually eligible older individuals receiving care in fee‐for‐service practices. There was a baseline in‐home structured interview with the patient, followed 1 year later with a telephone interview. Other data sources were Medicaid claims data and Elder Health's utilization records. The outcomes of interest were the patients' health and functional status, their satisfaction with care, rates of use of medical services, and costs to Medicaid.

Elder Health patients had similar general health status, better functional status, and greater satisfaction with access to care but less satisfaction with information giving than the fee‐for‐service group. They received more primary care and preventive services and had less than half the number of hospital days. Costs to Medicaid were nearly identical. Institutional and community‐based long‐term care costs were not included in the analysis.

As pressures mount for the Health Care Financing Administration to expand its prepaid contracts with private health plans and the need for integrated programs increase, quantitative assessment of innovative delivery models such as Elder Health, Inc. will be essential to ensure that patients' and the publics' interests are well served.

Analysis Health and functional status of Elder Health and comparison group patients at baseline and change at 1 year were compared using the chi‐square and t tests. Utilization data are presented as descriptive, with no statistical tests of means. Hospitalizations and hospital days are presented both from self‐report and from Medicaid data, because Medicaid data show only crossover payments for hospitalizations and therefore will not contain rehospitalizations within a 30‐day period.
Repression of α‐Amylase Activity by Anoxia in Grains of Barley is Independent of Ethanol Toxicity or Action of Abscisic Acid
Authors: Loreti E. , Vernieri P. , Alpi A. , Perata P.
Published: July 2002

Abstract: We studied the effects of anoxia on α‐amylase induction, comparing rice (Oryza sativa L.) and barley (Hordeum vulgare L.) grains. While gibberellic acid (GA3) induces α‐amylase in rice half‐grains under either aerobic or anaerobic conditions, barley half‐grains are insensitive to this hormone when applied under anoxia. The possible repressive role of ethanol and abscisic acid (ABA) was investigated. Exogenously added ethanol at concentrations mirroring those found in anaerobically treated tissues was unable to repress α‐amylase. The level of ABA in anoxic tissues was found to be much lower than the threshold for α‐amylase repression. Overall, the results indicated that these two compounds cannot be held responsible for the failure of barley grains to respond to gibberellic acid. Furthermore, anoxia repressed the induction of α‐amylase downstream of the slender mutation, indicating that the repression is independent of effects related to gibberellin perception. Overall, the results suggested that the ability of rice to respond to gibberellins under anoxia is an adaptative trait, independent of known negative regulators of α‐amylase induction.
High-power, diffraction-limited-beam operation from diode-laser phase-locked arrays operating in coupled first-order modes
Authors: Mawst L. J. , Botez D. , Roth T. J.
Published: July 2002

A novel index-guided, wide-waveguide coupled array structure grown entirely by metalorganic chemical vapor deposition has been demonstrated, which operates in a stable high-order array mode, remaining nearly diffraction limited to high drive currents (>5Ith ) and high-power levels (145 mW/uncoated facet). Strong lateral mode confinement (Δneff ≊1×10−2 ) at the element level coupled with the wide-waveguide geometry ensures operation in coupled first-order element modes. The out-of-phase operating array structure has interelement coupling that becomes stronger with increasing drive level, thereby offering stability against gain spatial hole burning at both the array level and the individual element level.
Response to ‘‘Comment on ‘Relaxation of strained-layer semiconductor structures via plastic flow’ ’’ [Appl. Phys. Lett. 5
3, 1127 (1988)]
Authors: Dodson Brian W. , Tsao Jeffrey Y.
Published: July 2002

In response to the  Comment of Strained−Layer Semiconductor Structures Plastic Flow , we would like to point out that one of us has developed an approximate solution for the plastic flow model which interpolates between the Matthews−Blakeslee expression for thermodynamic critical thickness and the People−Bean expression for large amounts of relaxation, and that Peopl e’s comment that high resolution studies of relaxation in the SiGe/Si system are lacking is not quite correct. (AIP)
Time-of-flight measurement of excitonic polaritons in a GaAs/AlGaAs quantum well
Authors: Ogawa K. , Katsuyama T. , Nakamura H.
Published: July 2002

We report the first experimental observation of excitonic polaritons in a GaAs/AlGaAs quantum well with incident light propagating parallel to the quantum well layer. We have built a time-of-flight measurement system which allows us to investigate low-temperature optical properties of semiconductor waveguides with picosecond time resolution. This system has been used to measure propagation delay time of an incident light pulse transmitted through the quantum well. The delay time increases drastically near the photon energies resonant to the optical absorption lines of the quantum well excitons. This behavior shows that the group velocity of the light pulse decreases as a result of the formation of quantum well excitonic polaritons. The group velocity drops to 7×104 m/s at a heavy-hole exciton absorption line at 6.0 K.
Anomalous diffusion of boron implanted into silicon along the [100] direction
Authors: Michel A. E. , Numan M. , Chu W. K.
Published: July 2002

We have observed transient enhanced diffusion of boron implanted into silicon along the [100] channeling direction and compared it with that of boron implanted in a ‘‘random’’ direction. It is found that the anomalous boron displacement for the channeled implants is significantly greater than for the random counterparts. An empirical explanation for the greater displacement of the channeled implants is proposed that is related to the spatial distribution of the implanted boron and the lattice damage generated by the implantation process.
Synchrotron x-ray standing-wave study of arsenic on Si(100)
Authors: Zegenhagen J. , Patel J. R. , Kincaid B. M. , Golovchenko J. A. , Mock J. B. , Freeland P. E. , Malik R. J. , Huang K.-G.
Published: July 2002

The position of As atoms on the silicon(100) surface has been determined using the x-ray standing-wave technique and synchrotron radiation. Since the experiments were performed in air, the As-covered (100) surface was capped with amorphous silicon. The results of the measurements are in agreement with the symmetric As dimer model for the (100) surface. The distance of the As dimers normal to the ideal (100) surface was found to be 1.26±0.01 Å which agrees with the value obtained from total energy minimization calculations. With no protective coating the As position was higher.
Solvable optimized four-wave mixing configuration with cubic photorefractive crystals
Authors: Fischer Baruch , Weiss Shimon
Published: July 2002

An analysis of an optimized configuration for phase conjugation and four-wave mixing in cubic photorefractive crystals (such as GaAs and Bi12SiO20) is presented. We obtain an exact solution of the four-wave mixing configuration, and find a wide range of self-oscillation regime.
Grating structure in self-pumping barium titanate by local erasure
Authors: Brody P. S.
Published: July 2002

A method of examining the photorefractive grating in a self-pumping barium titanate crystal is described; in this method, photorefractive grating elements are sequentially erased using a fine pulsed beam of photocarrier-generating light, while the resulting decrements in the phase-conjugate output are recorded. The erase beam scans the crystal in raster fashion, producing a map of decrements in the phase-conjugate output; these are interpreted as indicating the position of volume photorefractive grating elements that contribute to the phase-conjugate output. The results show that important elements of grating structure do exist in the front region of the crystal where the pumping beam enters.
Structural and microstructural characterization of a high T
c superconducting BiSrCaCu oxide
Authors: Liang J. M. , Chang L. , Tang S. F. , Chen Y. C. , Wu P. T. , Chen L. J.
Published: July 2002

The crystal structure and microstructures of a high Tc BiSrCaCuO (BSCCO) compound were characterized by transmission electron microscopy, x-ray diffraction (XRD), and energy dispersive spectrometry (EDS). Convergent beam electron diffraction (CBED) analysis established that the crystal is of mm2 symmetry. Combined with electron diffraction, XRD, and EDS data, the high Tc superconducting BSCCO compound was found to be of the Pnn2 space group, orthorhombic in structure with a=0.540 nm, b=2.689 nm, and c=3.040 nm and with an approximate composition of Bi2Sr2CaCu2Oy. Diffraction contrast analysis indicated that the dislocations are predominantly of screw character with [010] or [001] Burgers vectors. However, edge type dislocations and dislocations with [100] Burgers vector were also observed. The magnitude of the Burgers vector along the [100] direction was determined to be 1/2 [100] by high-resolution lattice imaging. Stacking faults and small-angle grain boundaries were frequently observed. The presence of a high density of defects in the superconducting oxide may facilitate the processing of the material and serve as effective flux line barriers.
Faraday rotation in the 10 μm region in InSb at liquid-helium temperature
Authors: Aggarwal R. L. , Lucey R. F. , Ryan-Howard D. P.
Published: July 2002

Faraday rotation has been measured at 10.59 and 9.66 μm in n-type InSb at ∼6 K having a carrier concentration of ∼2×1014 cm−3, using magnetic fields up to 50 kG. In addition to the interband and free-carrier plasma contributions to the Faraday rotation, an appreciable contribution from the conduction electron spins has been observed. The latter contribution is proportional to the spin alignment that saturates at magnetic fields exceeding ∼5 kG. Its saturation value of −17±1°/cm at 10.59 μm is in good agreement with the value calculated from published theoretical results. A value of −1.8±0.1°/kG cm has been deduced for the interband contribution at 10.59 μm, in disagreement with the previously published value of −3.8°/kG cm. Design for a 10 μm Faraday isolator is proposed for operation at ∼5 kG, a field well within the range of permanent magnets.
Sensitive, highly linear lithium niobate interferometers for electromagnetic field sensing
Authors: Bulmer C. H.
Published: July 2002

An asymmetric Mach–Zehnder interferometer in Ti:LiNbO3 has been demonstrated to have a 84 dB linear dynamic range and 1.1 μV sensitivity, for a 3 kHz detection bandwidth and a 50 Ω resistance, at the 1.3 μm wavelength. This device is useful for electric and magnetic field sensing. Optimum linearity is achieved with a 90° intrinsic phase bias. The dependence of dynamic range and sensitivity on optical power, phase bias, and modulation voltage is reported. The reasons for, and magnitudes of, deviations from optimum linear behavior are described for many fabricated interferometers.
Far-infrared absorption by oxygen in silicon
Authors: Yamada-Kaneta Hiroshi , Ogawa Tsutomu , Muraishi Shuichi , Kaneta Chioko , Wada Kunihiko
Published: July 2002

Far-infrared absorption measurements in the 14–50 cm−1 range have been performed for oxygen containing silicon crystals in a temperature range of 4.2–35 K. In addition to the previously reported absorption peaks at 29.3, 37.8, 43.3, and 49.0 cm−1 [D. R. Bosomworth, W. Hayes, A. R. L. Spray, and G. D. Watkins, Proc. R. Soc. London A 317, 133 (1970)], a fine structure with peaks at 25.3, 28.3, 30.2, and 33.3 cm−1 has been found, which is considered to be a sideband caused by a coupling between the off-center excitation of the interstitial oxygen and other anharmonic localized excitation of an energy of about 1 cm−1 hc.
Plasma focus wiggler for free-electron laser applications
Authors: Venneri F. , Kislev H. , Miley G. H.
Published: July 2002

A magnetically stabilized plasma focus with controlled modulations has been demonstrated for the first time. A 3-mm-diam plasma focus with two wiggler periods of 1 cm each was kept stable for about 30 ns. Similar configurations with shorter periods could be used as intense wigglers for short-wavelength free-electron lasers.
In0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistor on GaAs by molecular beam epitaxy
Authors: Won T. , Agarwala S. , Morkoç H.
Published: July 2002

We report on the first In0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistors grown on a GaAs substrate. In order to suppress the propagation of threading dislocations to the surface, a ten-period AlAs/In0.52Al0.48As (20 Å/20 Å) strained-layer superlattice was repeated twice with intervening undoped In0.52Al0.48As layers. The typical common emitter current gain in 50×50 μm2 emitter area devices was 50, with a maximum of 63, at a collector current density of 2×103 A/cm2.
Thermally and light-induced instabilities in phosphorus-doped hydrogenated amorphous silicon
Authors: Banerjee Ratnabali , Furui Tatsuya , Okushi Hideyo , Tanaka Kazunobu
Published: July 2002

Changes in the gap-state profile of phosphorus-doped hydrogenated amorphous silicon films subjected to light soaking and thermal quenching have been studied by isothermal capacitance transient spectroscopy. No suggestive changes due to thermal quenching are observed in the density-of-states distribution at least in the energy range 0.25–1.50 eV below the conduction-band edge (Ec). On the other hand, gap states are created in the range of 0.25–0.35 eV below Ec by light soaking, in addition to the conversion from deeper states located 1.0–1.2 below Ec to shallower states located 0.4–0.6 below Ec. These results suggest that the effects of light soaking and thermal quenching are apparently independent of each other.
High-power, high-brightness, phase-locked broad-stripe diode lasers
Authors: Lindstrom C. , Josefsson A. , Franklin G. , Milton M. , Nyberg C.
Published: July 2002

A novel superlinear graded index separate confinement laser diode structure is proposed. Single stripe diode lasers with 210 μm emitting aperture generate 3.2 W cw, and 6.3 W quasi-cw of light-output power in a phase-locked operation. The catastrophic optical density (30 W/mm) obtained for these lasers is better than that reported for devices with nonabsorbing mirrors.
Pinning mechanism in a continuous ultrafine Nb3Al multifilamentary superconductor
Authors: Takeuchi T. , Iijima Y. , Kosuge M. , Inoue K. , Watanabe K. , Noto K.
Published: July 2002

For Nb3Al multifilamentary superconductors fabricated by a newly developed composite process using continuous ultrafine Al-based alloy cores and pure Nb matrix, Jc properties have been investigated in detail in regard to the size and morphology of the Al core. A significant enhancement in pinning force caused by reducing the Al core size and an anisotropy in Jc observed in a rolled tape have indicated that the Nb3Al-matrix (or core) interface acts as a dominant pinning center of fluxoids.
Indium oxide diffusion barriers for Al/Si metallizations
Authors: Kolawa E. , Garland C. , Tran L. , Nieh C. W. , Molarius J. M. , Flick W. , Nicolet M-A. , Wei J.
Published: July 2002

Indium oxide (In2O3) films were prepared by reactive rf sputtering of an In target in O2/Ar plasma. We have investigated the application of these films as diffusion barriers in 〈Si〉/In2O3/Al and 〈Si〉/TiSi2.3/In2O3/Al metallizations. Scanning transmission electron microscopy together with energy dispersive analysis of x ray of cross-sectional Si/In2O3/Al specimens, and electrical measurements on shallow n+-p junction diodes were used to evaluate the diffusion barrier capability of In2O3 films. We find that 100-nm-thick In2O3 layers prevent the intermixing between Al and Si in 〈Si〉/In2O3/Al contacts up to 650 °C for 30 min, which makes this material one of the best thin-film diffusion barriers on record between Al and Si. (The Si-Al eutectic temperature is 577 °C, Al melts at 660 °C.) When a contacting layer of titanium silicide is incorporated to form a 〈Si〉/TiSi2.3/In2O3/Al metallization structure, the thermal stability of the contact drops to 600 °C for 30 min heat treatment.
Thermodynamic studies of the orthorhombic–tetragonal transition in Ba2YCu3O7−δ
Authors: Lo W. , Tang Tong B. , Li Chaorui , Xu Yuhuan
Published: July 2002

The superconducting oxide Ba2YCu3O7−δ is known to exist in two crystallographic structures, being orthorhombic or, at higher temperature, tetragonal. Thermogravimetric experiments have been performed to study their transition at different oxygen partial pressures. Weight loss curves, recorded by heating samples at various constant rates, each exhibit two inflection points. In our interpretation, such points delimit the regime within which the two structural phases coexist. Limiting values of temperature at these points, calculated by extrapolation to zero heating rates, and the corresponding magnitudes of oxygen nonstoichiometry are presented. Such data have basic significance as well as relevance to the thermal processing of materials.
Tunneling images of a high T
c superconducting Y1Ba2Cu3O7−x ceramic
Authors: Okoniewski A. M. , Klemberg-Sapieha J. E. , Yelon A.
Published: July 2002

Tunneling images of an Y1Ba2Cu3O7−x high Tc superconductor have been obtained in air. Slow scanning images show the roughness of surface in agreement with scanning electron microscope observations. Fast scanning pictures show the periodic structure with dimensions comparable to those of the bulk layered perovskite unit cell of the material.
Superconducting R-Ba-Cu-O balls made by rapid solidification
Authors: Li Yiping , Hadjipanayis G. C.
Published: July 2002

Melt spinning has been used to prepare superconducting R-Ba-Cu-O compounds with R=Y, Er, Dy, and Gd. The starting materials were sintered R-Ba-Cu-O samples, and most of them were not superconducting above 77 K. The melt-spun samples had a spherical shape with a diameter in the range of 0.1–2.0 mm. The samples were annealed in air at about 900 °C for 1 h. Samples with diameter greater than 1.5 mm were found to be not superconducting. The critical temperatures were found to be in the range of 60–88 K.
Two-beam coupling photorefractive spatial light modulation with reversible contrast
Authors: Marrakchi Abdellatif
Published: July 2002

The intricate polarization properties of Doppler-enhanced self-diffraction in linearly birefringent and optically active materials, such as bismuth silicon oxide crystals, are utilized to achieve real-time photorefractive spatial light modulation with contrast selection capability. The contrast reversal is explained in terms of the spatial modulation of the birefringence caused by an incoherent erasure beam.
Physical parameters of GaInAs/Si3N4 interface states obtained by the conductance method
Authors: Barrier Joël , Boher Pierre , Renaud Monique
Published: July 2002

Interface state parameters were studied in TiAu/Si3N4/Ga0.47In0.53As metal-insulator-semiconductor capacitors by conductance and capacitance measurements at various temperatures. The analysis of the data, taking into account the variation of the capture cross section versus energy, allows us to obtain the density of states, the capture cross section, the surface potential, and the dispersion parameter. The numerical values agree very well with results provided by capacitance transient methods at low temperatures (isothermal capacitance transient spectroscopy and deep level transient spectroscopy).
I
n s
i
t
u laser patterned desorption of GaAs quantum wells for monolithic multiple wavelength diode lasers
Authors: Epler J. E. , Treat D. W. , Chung H. F. , Tjoe T. , Paoli T. L.
Published: July 2002

A new laser-assisted crystal growth technique that enables three-dimensional patterning of the GaAs quantum well (QW) active layer within a laser diode structure is demonstrated. In this technique, the GaAs QW is locally heated with superimposed Ar+ and Nd:YAG laser beams during a pause in the metalorganic chemical vapor deposition growth. The evaporation rate of the GaAs is greatly increased by the laser heating, locally thinning the QW. After exposure, the crystal growth is resumed, burying the patterned QW within the crystal. Transmission electron microscopy is used to quantify the lateral profile of the QW thickness while photoluminescence is used to demonstrate the spatial variation of the energy band gap. Finally, multiple wavelength operation of broad-area diode lasers is observed, consistent with the spatial variation in the energy band gap.
Observation of a two-dimensional hole gas in boron-doped Si0.5Ge0.5/Ge heterostructures
Authors: Wagner G. R. , Janocko M. A.
Published: July 2002

The Hall mobility and magnetoresistance of Si0.5Ge0.5/Ge heterostructures grown by molecular beam epitaxy have been studied in the temperature range 1.5<T<300 K. Shubnikov–de Haas oscillations observed at T=1.5 K indicate that selective doping of the alloy with boron generates a two-dimensional hole gas in the Ge. The oscillation period yields a surface carrier density of 2×1012 cm−2, in reasonable agreement with the value of 3×1012 cm−2 obtained by Hall measurements. The mobility at T=4.2 K in a sample with an undoped alloy setback layer of 4 nm was μH=3.2×103 cm2/V s and in other samples was found to decrease with decreasing setback layer thickness.
Above-threshold analysis of ideal Y-junction semiconductor laser arrays
Authors: Streifer William , Welch David F. , Berger Josef , Scifres Don R.
Published: July 2002

An analysis of ideal Y-junction arrays above threshold shows that the radiation patterns deteriorate and the array begins to lase in more than one mode with increasing output power.
Thermal equilibrium changes in diode structures of doped amorphous silicon
Authors: Jang Jin , Lee Young Kuen , Kim Sung Chul , Lee Choochon
Published: July 2002

Thermal equilibration processes in diode structures of doped hydrogenated amorphous silicon have been studied. Fast cooling from above the thermal equilibrium temperature (TE) results in an increase in dark reverse current as well as in forward current. The reverse leakage current and the diode quality factor increase with quenching temperature at above TE. Therefore, it is concluded that the densities of metastable dangling bonds and active dopants increase upon fast cooling from above TE. We propose a new model to explain the experimental results.
Determination of electron energy distribution in a GaAs vertical field-effect transistor with hot-electron injection
Authors: Yamasaki K. , Daniels-Race T. , Lu S. S. , Schaff W. J. , Tasker P. J. , Eastman L. F.
Published: July 2002

Electron energy distribution on the drain edge of a channel in a GaAs nongated vertical field-effect transistor with hot-electron injection has been probed using hot-electron spectroscopy as a function of current density up to about 105 A/cm2. Electrons rapidly accelerated in an n+-i-p+-i-n+ planar-doped barrier source exhibit nonequilibrium transport through a thin channel (130 nm) with deceleration due to scattering and acceleration due to the electric field. The resulting hot-electron energy distribution, determined by using a planar-doped barrier as an analyzer, diverges from the steady-state one. This divergence dramatically increases with increasing the current density.
Calibration of the electrical response of piezoelectric elements at low voltage using laser interferometry
Authors: Riis E. , Simonsen H. , Worm T. , Nielsen U. , Besenbacher F.
Published: July 2002

A laser interferometric method is described by which the length-to-voltage sensitivity of piezoelectric elements, as used e.g., in scanning tunneling microscopes, can be calibrated. The method is based on measuring the optical frequency of a laser locked to a piezoelectrically tuned interferometer, relative to a stable reference. The high sensitivity of this technique allows the calibration to be carried out in the low-voltage regime.
Full-aperture, high-power semiconductor laser
Authors: Waters R. G. , Dalby R. J. , Emanuel M. A.
Published: July 2002

A single quantum well laser with a 2-mm-wide aperture has exhibited low threshold current density and nearly 100% packing fraction. The lateral structure relies on epitaxial growth on a corrugated substrate to frustrate radiative lateral processes and it thus eliminates the need for isolation at least for incoherent operation. Threshold current densities are comparable to those for low-power devices, and slope efficiencies remain undiminished to our current limit where 10.7 W per facet is attained. The aperture size is limited only by our fixturing arrangement.
Rapid fabrication of lightweight ceramic mirrors via chemical vapor deposition
Authors: Goela Jitendra S. , Taylor Raymond L.
Published: July 2002

Lightweight Si/SiC mirrors of nominal diameter 7.5 cm have been fabricated via a scalable and rapid, chemical vapor deposition (CVD) process to demonstrate the CVD mirror fabrication technology. These mirrors consist of a faceplate of either Si or Si-coated SiC and a lightweight backstructure made of either Si or SiC. The mirrors were polished to a figure better than 1/5th of a wave at 0.6328 Å and a finish of better than 10 Å rms. A procedure for fabricating these mirrors is described. The CVD fabrication process is fast and has the potential to yield several mirrors in a few weeks time from a single reactor. The CVD mirror fabrication technology is quite general and can be extended to include mirrors of other ceramic materials such as TiB2 and B4C.
Carrier-injection-type optical switch in GaAs with a 1.06–1.55 μm wavelength range
Authors: Ito Fumihiko , Tanifuji Tadatoshi
Published: July 2002

A carrier-injection-type optical switch which operates in the 1.06–1.55 μm wavelength range is designed and fabricated. This switch uses the plasma dispersion effect in GaAs. Switching current is about 90 mA at all in-range wavelengths. Its broad wavelength range is suitable for optical signal processing applications in wavelength division multiplexing transmission systems.
Improvements in the differential phase shift of magneto-optic waveguides by loading with high refractive index overlayers
Authors: Inuzuka H. , Okamura Y. , Yamamoto S.
Published: July 2002

Experimental results are presented for a nonreciprocal phase shift of vertically polarized waves in four-layer magneto-optic rib waveguides. The structure consists of a high refractive index nonmagnetic layer of titanium oxide on top of a magneto-optic film (a lanthanum and gallium substituted yttrium iron garnet film on a gadolinium gallium garnet substrate) to improve differential phase characteristics. The difference of phase constants for waves traveling in opposite directions is evaluated by observing the variation in the polarization coupled out of a straight waveguide when simultaneously exciting both horizontally and vertically polarized waves with equal amplitudes and phases. The phase shift difference varies with the thickness of the nonmagnetic film, and is larger than that of a previous three-layer waveguide in the overlayer thickness range 0.15–0.45 μm. The maximum phase shift obtained is 2.5 times as large as that of uncoated waveguides.
Electrical activation curve of silicon implanted in GaAs
Authors: Morrow Richard A.
Published: July 2002

A model describing the electrical activation of silicon implanted in semi-insulating GaAs is fit to carrier concentration versus silicon concentration data spanning over three decades. The model incorporates the reactions of silicon with boron and EL2 present in the substrate.