bluuebunny/crossref_metadata_2025 huggingface dataset:
Profile of Tuberculosis Deaths by Mesoregion in the State of Pará from 2012 to 2022: An Ecological Study
Authors: Marcos Weber , Lobato Diana da Costa , Garcez Juliana Conceição Dias , Sardinha Daniele Melo , Marinho Rebecca Lobato , Júnior Adilson Mendes De Figueiredo , Lima Karla Valéria Batista
Published: February 2025

Introduction: Tuberculosis (TB) is an infection caused by bacteria from the Mycobacterium tuberculosis complex, transmitted through airborne aerosols, released during coughing, talking, or sneezing. Despite advancements in TB control and the availability of established treatments for over 40 years, there are still ten million new cases, and 1.5 million deaths reported annually worldwide.
Methods: A descriptive and ecological study was performed on all TB-related deaths reported between 2010 and 2022, in Pará, Brazil. Data were obtained from Notifiable diseases Information System. The study have analyzed clinical, epidemiological and sociodemographic characteristics, as well as geographical and statistical trends in mortality, using binary logistic regression.
Results: A total of 1,253 TB-related deaths were reported in Pará. There was a significant increasing trend in the mortality rate, with the highest value observed in the metropolitan mesoregion. The mean age was 52.1 years, most were male, brown, without elementary education and lived in the urban area.  New TB cases were the most frequently recorded, with the pulmonary clinical form accounting for 84% of cases and 15.5% of cases reported from alcoholism. The most common diagnosis was sputum smear microscopy, however, follow-up sputum smear microscopies were infrequently and directly observable treatment was rarely performed (19.2%). The multivariate analysis of deaths by mesoregion revealed significant differences with each mesoregion exhibiting distinct contributing variables.
Conclusions: Our results show the need for epidemiological surveillance professionals to implemente different surveillance measures and strategies for each mesoregion. Strengthening municipal healthcare system is a critical step to ensure early diagnosis and appropriate treatment for each clinical case. In addition, public policies should aim to improve socio-environmental and economic conditions addressing regional disparities to better serve the community.
Constitutive activation of muscarinic receptors by the G‐protein Gq
Authors: Burstein Ethan S. , Spalding Tracy A. , Braüner-Osborne Hans , Brann Mark R.
Published: July 2002

In the absence of ligands, G‐protein coupled receptors interconvert between active and inactive conformations. These conformations are stabilized by agonists and antagonists, respectively. Like agonists, G‐proteins are thought to preferentially associate with receptors in the active conformation and should therefore be able to promote their formation in the absence of agonist. We show that over‐expression of Gq induces constitutive activation of compatible muscarinic receptors and that this activity is blocked by muscarinic antagonists. Gq also increases the potency and efficacy of agonists. These results indicate that regulation of G‐protein levels has a profound impact on receptor control of cellular physiology, even in the absence of agonist ligands.
Three‐dimensional architecture of the skeletal muscle ryanodine receptor
Authors: Wagenknecht Terence , Radermacher Michael
Published: July 2002

Recent advances in determining the three‐dimensional architecture of the skeletal muscle ryanodine receptor/calcium release channel (RyR) by cryo‐electron microscopy and three‐dimensional reconstruction are discussed. The tetrameric receptor is characterized by a large 4‐fold symmetric cytoplasmic assembly that consists of many domains separated by solvent‐containing crevices and holes. Experimental evidence suggests that at least one regulatory ligand, calmodulin, binds to sites on the cytoplasmic assembly that are at least 10 nanometers from the transmembrane channel.
The centrosomal big bang: From a unique central organelle towards a constellation of MTOCs
Authors: Mignot Jean‐Pierre
Published: July 2002

Summry— This article is the fruit of reflections on the comparative study of centrosomal structures of various protists, and on recent data on the organization and composition of the centrosome of multicellular organisms. On the basis of a few significant situations encountered in protists, a model is proposed in which the metazoan centrosome represents a complex of three types of specialized microtubule‐organizing centers (MTOCs) of different origin and function, designated MTOC1, MTOC2, MTOC3. MTOCs1, presumably the most primitive, drive the mitosis. Associated with the chromosomes, they would be primitively included in the nuclear matrix acting as polar bodies in closed mitosis which characterizes many protists. MTOCs2 correspond to the centrioles, relics of basal bodies, whose primitive function was to engender a motor organelle. They differ from other cytoskeletal organizing centers only by their ubiquity and their 9+0 organization. MTOCs3, which may form stable structures of specific shape in some protists, control cellular morphology and intracellular traffic. The relationships between the various components and the nucleus are considered. Using a speculative scheme, we attempt to understand how this ensemble has diversified over the evolution of protists.
Cytoskeleton alterations of erythrocytes from patients with Fanconi's anemia
Authors: Malorni Walter , Straface Elisabetta , Pagano Giovanni , Monti Daniela , Zatterale Adriana , Del Principe Domenico , Deeva Irina B. , Franceschi Claudio , Masella Roberta , Korkina Ludmilla G.
Published: July 2002

Fanconi's anemia (FA) is a very rare genetically heterogeneous disease which has been hypothesized to be defective in the detoxification of reactive oxygen species. In this work we report the results obtained by morphometric and biochemical analyses on the red blood cells (RBCs) from FA patients. With respect to RBCs from healthy donors the following changes have been detected: (i) a variety of ultrastructural alterations, mainly surface blebbing typical of acanthocytes and stomatocytes; (ii) a significant quantitative increase of these altered forms; (iii) modifications of spectrin cytoskeleton network; (iv) an altered redox balance, e.g. a decreased catalase activity and significant variations in the GSSG/GSH ratio. We hypothesize that remodeling of the redox state occurring in FA patients results in cytoskeleton‐associated alterations of red blood cell integrity and function.
Intrinsic Oxygen Use Kinetics of Transformed Plant Root Culture
Authors: Asplund Patrick T. , Curtis Wayne R.
Published: July 2002

Root meristem oxygen uptake, root tip extension rate, and specific growth rate are assessed as a function of dissolved oxygen level for three transformed root cultures. The influence of hydrodynamic boundary layer was considered for all measurements to permit correlation of oxygen‐dependent kinetics with the concentration of oxygen at the surface of the root meristem. Oxygen uptake rate is shown to be saturated at ambient conditions, and a saturation level of approximately 300 μmole O2/(cm3 tissue·hr) was observed for all three of these morphologically diverse root types. In nearly all cases, the observation of a minimum oxygen pressure, below which respiration, extension, or root growth would not occur, could be accounted for as a boundary layer mass transfer resistance. The critical oxygen pressure below which respiration declines is below saturated ambient oxygen conditions. In contrast, critical oxygen pressures for root tip extension were much higher; extension was nearly linear for the two thicker root types (Hyoscyamus muticus, henbain; Solanum tuberosum, potato) above ambient oxygen levels. The performance of the thinnest root, Brassica juncea (Indian mustard) was consistent with reduced internal limitations for oxygen transport. Extension rates did not correlate with biomass accumulation. The fastest growing henbain culture (μ = 0.44 day−1) displayed the slowest extension rate (0.16 mm/hr), and the slowest growing mustard culture (μ = 0.22 day−1) had the fastest tip extension rate (0.3 mm/hr). This apparent paradox is explained in terms of root branching patterns, where the root branching ratio is shown to be dependent upon the oxygen‐limited mersitem extension rate. The implications of these observations on the performance of root culture in bioreactors is discussed.
Cell death in maize
Authors: Buckner Brent , Johal Guri S. , Janick‐Buckner Diane
Published: July 2002

Cell death occurs in plants as a part of normal development and as a response to toxins, pathogens and other environmental stimuli or insults. When cell death occurs as an orderly disassembly of the cell under the control of a genetically determined program, the process is referred to as programmed cell death (PCD). The PCD mechanisms of plants show many striking similarities to, but also intriguing differences from, those of animals. The extensive genetic, developmental and physiological characterizations of maize have made it an excellent system for the study of cell death. We describe the recent advances in the study of cell death in maize in light of what is known in plants and animals.
Temperature and oxygen regulation of oleate desaturation in developing sunflower (Helianthus annuus) seeds
Authors: García‐Díaz M. Teresa , Martínez‐Rivas José M. , Mancha Manuel
Published: July 2002

The effect of low (10°C) and high (30°C) temperature on in vivo oleate desaturation has been studied in developing sunflower (Helianthus annuus L.) seeds under conditions of different oxygen availability (capitulum, detached achenes or peeled seeds). In seeds remaining in the capitulum, only a part of the oleate newly synthesized at high temperature was desaturated to linoleate, whereas more oleate than that synthesized de novo was desaturated at low temperature. Achenes were only able to significantly desaturate oleate at low temperatures. In contrast, oleate desaturation was detected in peeled seeds incubated at low and high temperatures, showing the highest rate at 20°C. Hull removing dramatically increased the activity of the microsomal oleate desaturase (FAD2, EC 1.3.1.35) at all studied temperatures, although a long‐term inactivation of the enzyme was observed at high temperatures. Low oxygen concentration (1–2%) obtained by respiration of peeled seeds incubated in sealed vials, brought about the inactivation of the enzyme. All these data suggest that temperature regulates oleate desaturation controlling the amount of oleate and the FAD2 activity. In addition, this enzyme seems to be also regulated by the availability of oxygen, which is affected inside the achene by its diffusion through the hull, and the competition with respiration, both factors being temperature‐dependent.
Explanatory models in the interpretations of clinical features of dental patients within a university dental education setting
Authors: Maupome Gerardo , Sheiham Aubrey
Published: July 2002

Clinicians may acquire biased perceptions during their dental education that can affect decisions about treatment/management of dental decay. This study established explanatory models used by students to interpret clinical features of patients. It employed a stereotypical dental patient under standardised consultation conditions to identify the interpretation of oral health/disease features in the eyes of student clinicians. The study aimed to establish the perceptions of the patient as a client of the university dental clinic, as seen through the ideological lens of a formal Dental Education system. The discourse during simulated clinical consultations was qualitatively analysed to interpret values and concepts relevant to the assessment of restorative treatment needs and oral health status. Three constructs during the consultation were identified: the Dual Therapeutic Realms, the Choices Underlying Treatment Options, and the High‐Risk Triad. Comparing these discourse components, the Patient Factors of the Bader and Shugars model for treatment decisions supported the existence of a core set of themes. It was concluded that certain consultation circumstances influenced the adequacy of diagnostic strategies, mainly by introducing loosely defined but highly specific socio‐cultural biases ingrained in the Dental Education concepts and diagnostic/treatment needs systems.
Activated neutrophils oxidize extracellular proteins of endothelial cells in culture: effect of nitric oxide donors
Authors: CZAPSKI Grzegorz A. , AVRAM Diana , SAKHAROV Dmitri V. , WIRTZ Karel W.A. , STROSZNAJDER Joanna B. , PAP Everard H.W.
Published: July 2002

Protein oxidation of human umbilical-vein endothelial cells (HUVEC) in culture was examined under various conditions of oxidative stress. Extracellular protein (ECP) oxidation was assessed by determining dityrosine bond formation, which is indicated by the covalent coupling of the membrane-impermeable tyramine—fluorescein conjugate (TyrFluo) to HUVEC proteins. The acetylated membrane-permeable form of TyrFluo (acetylTyrFluo) was used for the determination of intracellular protein (ICP) oxidation. Oxidative stress was induced by exposing the HUVEC to PMA-activated human neutrophils, to a horseradish peroxidase/hydrogen peroxide (HRP/H2O2) system or to H2O2 alone. Coupling of the probes was determined by confocal laser scanning microscopy and by Western blotting using anti-fluorescein antibody. Diethylamine nitric oxide (DEANO) was used to determine the effect of NO on the tyrosyl radical formation in proteins. The oxidative burst generated by activated neutrophils for 15min, resulted in inducing dityrosine formation in ECP of HUVEC. Similar results were obtained with HRP/H2O2, but H2O2 alone did not have any effect on ECP. In the presence of DEANO (0.1mM or higher), ECP oxidation was almost completely inhibited. This indicates that NO may protect endothelial cells against protein oxidation by activated neutrophils under pro-inflammatory conditions. Activated neutrophils did not oxidize ICP of HUVEC, which strongly suggests that the effect of the oxidative burst was restricted to the proteins exposed to the medium.
Mycolic acid biosynthesis and enzymic characterization of the β-ketoacyl-ACP synthase A-condensing enzyme from Mycobacterium tuberculosis
Authors: KREMER Laurent , DOVER Lynn G. , CARRÈRE Séverine , NAMPOOTHIRI K. Madhavan , LESJEAN Sarah , BROWN Alistair K. , BRENNAN Patrick J. , MINNIKIN David E. , LOCHT Camille , BESRA Gurdyal S.
Published: July 2002

Mycolic acids consist of long-chain α-alkyl-β-hydroxy fatty acids that are produced by successive rounds of elongation catalysed by a type II fatty acid synthase (FAS-II). A key feature in the elongation process is the condensation of a two-carbon unit from malonyl-acyl-carrier protein (ACP) to a growing acyl-ACP chain catalysed by a β-ketoacyl-ACP synthase (Kas). In the present study, we provide evidence that kasA from Mycobacterium tuberculosis encodes an enzyme that elongates in vivo the meromycolate chain, in both Mycobacterium smegmatis and Mycobacterium chelonae. We demonstrate that KasA belongs to the FAS-II system, which utilizes primarily palmitoyl-ACP rather than short-chain acyl-ACP primers. Furthermore, in an in vitro condensing assay using purified recombinant KasA, palmitoyl-AcpM and malonyl-AcpM, KasA was found to express Kas activity. Also, mutated KasA proteins, with mutation of Cys171, His311, Lys340 and His345 to Ala abrogated the condensation activity of KasA in vitro completely. Finally, purified KasA was highly sensitive to cerulenin, a well-known inhibitor of Kas, which may lead to the development of novel anti-mycobacterial drugs targeting KasA.
Cytomegalovirus seropositivity adversely influences outcome after T‐depleted unrelated donor transplant in patients with chronic myeloid leukaemia: the case for tailored graft‐versus‐host disease prophylaxis
Authors: Craddock C. , Szydlo R. M. , Dazzi F. , Olavarria E. , Cwynarski K. , Yong A. , Brookes P. , De La Fuente J. , Kanfer E. , Apperley J. F. , Goldman J. M.
Published: July 2002

Graft‐versus‐host disease (GVHD) remains a major cause of morbidity and mortality after haematopoietic stem cell transplantation from matched unrelated donors (MUD). The role of T‐cell depletion (TCD) as a strategy to prevent GVHD is controversial because of the associated increased risk of leukaemic relapse, graft failure and delayed immune reconstitution. The demonstration that donor lymphocyte infusion (DLI) is effective salvage therapy if patients relapse after transplantation for chronic myeloid leukaemia (CML) prompted us to examine the proposal that TCD may be a form of GVHD prophylaxis particularly suited to this disease in patients undergoing MUD transplantation. We analysed the outcome of 106 consecutive patients with CML in first chronic phase who underwent MUD transplantation. Patients were conditioned with cyclophosphamide and total body irradiation (TBI), and received in vivo TCD, using CD52 monoclonal antibody, as GVHD prophylaxis. Donor lymphocytes were infused at the time of leukaemic relapse. The projected survival at 5 years for all patients was 52·6%. The probability of developing severe acute GVHD (grade 3 or 4) was 14·5%. The only significant predictor of overall survival in univariate and multivariate analysis was patient cytomegalovirus (CMV) serostatus: in CMV‐negative patients survival at 5 years was 60% vs. 42% in CMV‐positive patients (P = 0·006). The use of TCD was associated with an increased risk of relapse (62% probability at 5 years after transplant), but 80% of patients who received DLI achieved molecular remission that was durable in all but two cases. In vivo TCD, in conjunction with DLI at relapse, is a valuable GVHD prophylactic regimen in CMV‐seronegative recipients of MUD allografts, but in CMV‐seropositive patients this approach is associated with an increased non‐relapse mortality. Consequently, GVHD prophylactic regimens in MUD transplantation should be tailored according to the patient and donor pretransplant characteristics.
A method of choosing locations based on genotype × environment interaction for regional trials of rice
Authors: Fan L. J. , Hu B. M. , Shi C. H. , Wu J. G.
Published: July 2002

An ideal test location with particular environmental conditions should generate a relatively large genotype × environment interaction (GE) value in regional trials. A method of selecting test locations based on GE was proposed. Using the statistic Dj, the ranking of ability to discriminate the best genotypes for locations could be obtained. The locations among the group with the smallest Dj value were deleted from the whole set step by step, and the number of locations was reduced to a rational level at which most (over 85%) of the GE sum of squares of trials were maintained. A comparative evaluation based on data collected from Zhejiang Province (China) rice regional trials showed that the new method was more feasible than two other methods without loss of accuracy and reliability.
A MODIFICATION OF ISOLATED ROUX LOOP RECONSTRUCTION AFTER PANCREATICODUODENECTOMY
Authors: Toogood Giles J. , Wilson Thomas G. , Padbury Robert T. A.
Published: July 2002

Background: Different techniques of reconstruction following pancreaticoduodenectomy have been described. A new modification using an isolated Roux‐en‐Y loop is reported.

Methods: The isolated loop is taken up to bile duct rather than pancreas as previously described.

Results: Seventeen patients have undergone this procedure. Two pancreatic fistulae developed, both following postoperative abscess formation. There was no operative mortality.

Conclusion: This reconstruction provides separation of biliary and pancreatic fluid but adds two further benefits: the wide jejunal lumen allows for an easier pancreaticojejunal anastomosis, particularly when operating on a soft pancreas, and separation of gastric and biliary anastomoses prevents the efflux of bile into stomach.
Near‐normoglycaemic remission in African‐Americans with Type 2 diabetes mellitus is associated with recovery of beta cell function
Authors: McFarlane S. I. , Chaiken R. L. , Hirsch S. , Harrington P. , Lebovitz H. E. , Banerji M. A.
Published: July 2002

SUMMARY

Aims  To prospectively determine the frequency of remission and possible mechanism of beta cell recovery in non‐Whites with Type 2 diabetes mellitus in the setting of intensive glycaemic regulation using pharmacological agents.

Methods  Twenty‐six consecutive, newly diagnosed African‐American, Type 2 diabetic patients presenting primarily for severe hyperglycaemia (31.0 ± 12.8 mmol/l) were followed for at least 1 year. Initial hospitalization included treatment with insulin, fluids and electrolytes. Outpatient intensive glycaemic regulation included insulin or glibenclamide, diabetes education and diet that altered nutrient content. Plasma glucose and C‐peptide responses to an oral glucose tolerance test and HbA1c were measured at < 14, 15–56 and 57–112 days after presentation. Remission was defined as a HbA1c ≤ 6.3% and fasting plasma glucose < 6.9 mmol/l, 3 months after discontinuing all pharmacological agents.

Results  Eleven of 26 patients (42.3%) developed remission after a mean of 83 days of pharmacological treatment and remained in remission during follow‐up for 248–479 days; one relapsed after 294 days. Fifteen patients who did not develop a remission and were followed for 168–468 days, required continuing pharmacological therapy to be well‐controlled. (mean HbA1c = 7.1%). There was no significant difference in age, sex, plasma glucose at presentation, initial glycaemic regulation, final body mass index, magnitude of weight change or pharmacological agents used for treatment between the two groups. Plasma C‐peptide response to oral glucose was initially (< 14 days) suppressed in all subjects and subsequently increased. The increase was significantly greater in those who underwent a remission than those who did not. Neither significant weight loss nor severe hypoglycaemia was observed in either group during intensive treatment.

Conclusions  Forty‐two per cent of newly diagnosed, unselected African‐Americans with Type 2 diabetes, treated intensively using pharmacological agents, education and diet developed near‐normoglycaemic remission. Remission was associated with a greater recovery of glucose‐stimulated insulin secretion suggesting that therapies directed at promoting beta cell recovery and preservation are potentially useful approaches to the treatment of Type 2 diabetes mellitus.
Effects of tinted intraocular lens on contrast sensitivity
Authors: Niwa Kazushi , Yoshino Yukio , Okuyama Fumio , Tokoro Takashi
Published: July 2002

We evaluated contrast sensitivity and glare in 64 pseudophakic eyes. An ultraviolet‐absorbing intraocular lens (IOL) was implanted in 32 eyes and a noncyanopsia yellow‐tinted IOL was implanted in 32 eyes. The latter lens was designed to effectively absorb light below a wavelength of 500 nm. Contrast sensitivity was measured at a pupil diameter of 3 mm using an artificial pupil. The implanted yellow‐tinted IOL showed improved contrast sensitivity in the middle spatial frequencies of 6 and 12 c/deg in photopic and mesopic vision. In addition, the yellow‐tinted IOL decreased the effect of central glare on the contrast sensitivity.
Femtosecond intervalley scattering in GaAs
Authors: Becker P. C. , Fragnito H. L. , Brito Cruz C. H. , Shah J. , Fork R. L. , Cunningham J. E. , Henry J. E. , Shank C. V.
Published: July 2002

We report the measurement of intervalley scattering rates for optically excited carriers in GaAs. The measurements were performed using optical pulses of 6 fs duration and an energy distribution centered at 2.0 eV. The average rates for Γ→X and Γ→L intervalley scattering were separately estimated by varying the sample temperature.
Lasing characteristics of GaAs microresonators
Authors: Jewell J. L. , McCall S. L. , Lee Y. H. , Scherer A. , Gossard A. C. , English J. H.
Published: July 2002

Lasing characteristics of optically pumped 1.5-μm-diam GaAs-AlAs microresonators are reported. Room-temperature thresholds of 9 pJ were observed. Uniform outputs were obtained from a simultaneously driven 2×2 array.
Enhanced magnetically tunable attenuation and relative velocity of 0.6 GHz Rayleigh waves in nickel thin films
Authors: Wiegert R. F. , Levy M.
Published: July 2002

The magnetic field (H) dependences of the ultrasonic attenuation Δα(H) and the relative velocity ΔV(H) responses of 0.6 GHz Rayleigh-mode surface acoustic wave pulses in vacuum-evaporated, uniaxially anisotropic nickel thin films were measured and correlated with changes in the sample’s dc magnetoresistance Δρ(H). Recent advances in film preparation techniques have resulted in low magnetic anisotropy dispersion samples with enhanced magnetoelastic responses at small H [Δα(H)≊80 dB/cm and ΔV(H)/V≊0.07% as H varies from 0 to 100 Oe].
Band bending, Fermi level pinning, and surface fixed charge on chemically prepared GaAs surfaces
Authors: Yablonovitch E. , Skromme B. J. , Bhat R. , Harbison J. P. , Gmitter T. J.
Published: July 2002

We compare the nature of the band bending under GaAs surfaces prepared by alkaline sulfides [Na2S⋅9H2O, (NH4)2S] with that under oxidized GaAs surfaces. We make the point that Fermi level pinning implies band bending, but band bending does not necessarily imply ‘‘pinning.’’ In either case, even weak light illumination substantially flattens the bands. On ammonium sulfide treated surfaces the fixed and trapped charge density in the dark is only ∼5×1011 electrons/cm2, but these few states are mostly neutralized at low-level forward injection. This behavior should not be confused with Fermi level pinning.
Slow wave propagation in air-filled porous materials and natural rocks
Authors: Nagy Peter B. , Adler Laszlo , Bonner Brian P.
Published: July 2002

Slow compressional waves in fluid-saturated porous solids offer a unique acoustical means to study certain material properties, such as tortuosity and permeability. We present a novel experimental technique based on the transmission of airborne ultrasound through air-filled porous samples. The suggested method can be used to measure the velocity and attenuation of the slow compressional wave in a wide frequency range from 30 to 500 kHz. More important, the technique is so sensitive that it provides irrefutable evidence of slow wave propagation in air-saturated natural rocks and lends itself quite easily to tortuosity measurements in such materials, too.
Alexandrite laser pumped by semiconductor lasers
Authors: Scheps Richard , Gately Bernard M. , Myers Joseph F. , Krasinski Jerzy S. , Heller Donald F.
Published: July 2002

We report the first operation of a direct diode-pumped tunable chromium-doped solid-state laser. A small alexandrite (Cr:BeAl2O4) crystal was longitudinally pumped by two visible laser diodes. The threshold pump power was 12 mW using the R1 line at 680.4 nm for the pump transition, and the slope efficiency was 25%. The measured laser output bandwidth was 2.1 nm.
Molecular beam epitaxial growth of CdTe on 5-in.-diam Si (100)
Authors: Sporken R. , Lange M. D. , Masset C. , Faurie J. P.
Published: July 2002

CdTe (111)B films with a 5 in. diameter have been grown on Si (100) substrates. They were characterized by in situ electron diffraction, x-ray diffraction, and low-temperature photoluminescence. The layer thickness was measured across two diameters with infrared transmission, and a standard deviation of 2.3% is obtained. This demonstrates the possibility of producing CdTe layers with a 5 in. diameter with excellent uniformity in terms of thickness and crystalline quality. Moreover, this demonstrates the potential for molecular beam epitaxial growth of other materials on large-area substrates. In fact, these are the largest monocrystalline layers of a II-VI semiconductor material ever grown by any technique.
All-organic thin-film transistors made of alpha-sexithienyl semiconducting and various polymeric insulating layers
Authors: Peng Xuezhou , Horowitz Gilles , Fichou Denis , Garnier Francis
Published: July 2002

Thin-film transistors (TFTs) were fabricated with a variety of organic polymer insulators topped with a vacuum evaporated organic semiconductor, α-sexithienyl (α6T). No field-enhanced source-drain current was obtained with polystyrene (PSt) and polymethylmethacrylate (PMMA). The field-enhanced current is weak with polyvinyl chloride (PVC), but much stronger with polyvinyl alcohol (PVA) and cyanoethylpullulan (CYEPL), a cyanoethylated polysaccharide which possesses a high dielectric constant (εr=18.5 at 10 kHz). In these last two instances, the field-effect mobility surpasses the one measured on TFTs made on a SiO2 insulating layer. A strong correlation is found between the dielectric constant of the insulator and the field-effect mobility.
Terahertz radiation from large aperture Si p-i-n diodes
Authors: Xu L. , Zhang X.-C. , Auston D. H. , Jalali B.
Published: July 2002

Subpicosecond electromagnetic pulses having THz bandwidths have been generated from large aperture Si p-i-n diodes under different biases by illumination with fs-optical pulses. The amplitude and spectral bandwidth of the radiated pulses increases with the reverse bias on the p-i-n diode. This effect can be explained by the electric field dependence of the transient drift velocity of the photo-generated carriers in the intrinsic region of the p-i-n diode.
Periodically poled LiNbO3 for high-efficiency second-harmonic generation
Authors: Jundt D. H. , Magel G. A. , Fejer M. M. , Byer R. L.
Published: July 2002

Quasi-phase-matched room-temperature frequency doubling to generate blue, green, and red light was demonstrated using periodically poled LiNbO3 crystals. A 1.24-mm-long sample in an external resonant cavity generated 1.7 W of green power from an input of 4.2 W at the 1.064 μm Nd:YAG laser line when heated to 140 °C to compensate for a slight error in periodicity.
Diamond deposition on silicon surfaces heated to temperature as low as 135 °C
Authors: Ihara M. , Maeno H. , Miyamoto K. , Komiyama H.
Published: July 2002

Diamond films were deposited on the silicon wafer at as low a temperature as 135 °C by filament-assisted chemical vapor deposition. Silicon wafer substrate scratched with diamond powder was cooled by a stream of water flowing around a substrate holder. The films were identified as diamond by Raman spectroscopy. Clearly faceted crystals were shown in scanning electron micrographs.
Temperature dependence of the sticking probability and molecular size of the film growth species in an atmospheric chemical vapor deposition process to form AlN from AlCl3 and NH3
Authors: Kim H. J. , Egashira Y. , Komiyama H.
Published: July 2002

The sticking probability and molecular size of the growth species were determined as a function of deposition temperature ranging from 700 to 950 °C, in the AlN films prepared from AlCl3 and NH3. A novel method was developed, that includes the measurement of the film thickness profile on micron-sized trenches and the molecular diffusivity of the growth species. The molecular size was about 1 nm at 700–850 °C and decreased gradually with increasing temperature. The sticking probability increased from 0.02 to 0.5 in the temperature range 700–950 °C and, surprisingly, obeyed the Arrhenius law in spite of this large probability of sticking. The activation energy amounted to 136 kJ/mol.
Pd/Si plasma immersion ion implantation for selective electroless copper plating on SiO2
Authors: Kiang Meng-Hsiung , Lieberman Michael A. , Cheung Nathan W. , Qian X. Y.
Published: July 2002

Selective deposition of copper in SiO2 trenches has been carried out using Pd/Si plasma immersion ion implantation and electroless Cu plating. To form the seed layer for electroless Cu plating on SiO2, sputtered Pd and Si atoms were partially ionized by the Ar plasma and then deposited at bottoms of SiO2 trenches; Ar ion beam was then applied to assist the mixing of the deposited Pd/Si films with the SiO2 substrate by recoil implantation. We found a threshold Pd dose of 2×1014/cm2 is required to initiate the electroless plating of Cu. By careful control of the anisotropic etching of the oxide trenches and proper choice of the Pd dose, 1-μm wide Cu filled lines with flat surfaces suitable for planarized multilevel metallization were successfully fabricated.
Damage introduction in InP and InGaAs during Ar and H2 plasma exposure
Authors: Pearton S. J. , Ren F. , Abernathy C. R. , Hobson W. S. , Fullowan T. R. , Esagui R. , Lothian J. R.
Published: July 2002

Changes in the sheet resistance of doped epitaxial layers of InP and In0.53Ga0.47As exposed to microwave Ar or H2 discharges were measured as a function of the exposure time (1–20 min), plasma pressure (1–20 mTorr) and the additional rf-induced negative dc bias (50–400 V) on the sample. Changes in sheet resistance of ≤10% are only obtained for low dc biases (≤−75 V) or short exposures for either type of discharge. Hydrogen plasmas led to more substantial resistance changes than argon plasmas under all conditions, with the amount of damage introduction or hydrogen passivation being strongly dependent on dc bias and exposure time, but weakly dependent on pressure. The results indicate that high density, low pressure plasmas with low dc biases are capable of causing minimal disruption to InP-based materials during dry etching for device fabrication.
Emission of microwave and millimeter wavelength radiation during hollow cathode discharge operation of the back lighted thyratron
Authors: Liou R. , Figueroa H. , McCurdy A. H. , Kirkman-Amemiya G. , Temkin R. J. , Fetterman H. , Gundersen M. A.
Published: July 2002

Experimental observation of pulsed radiation ranging from ∼20 GHz to above 100 GHz during the hollow cathode discharge phase of operation of a back-lighted thyratron is reported. The discharge is operated with 120 mTorr Ar gas at 20 kV initial voltage. Pulsed radiation was observed for ∼50 ns, and an electron beam with energy of ∼20 keV was also observed. The observations are correlated with plasma processes predicted in recent computer simulations. The sudden turn-off of the radiation is believed to be a result of plasma expansion and sheath contraction inside the hollow cathode region. A method for varying the pulse length is discussed.
Preparation of Fe nanocrystalline in SiO2 by ion implantation
Authors: Zhang G. L. , Liu W. H. , Xu F. , Hu W. X.
Published: July 2002

We present a novel method, by using an ion implantation and subsequent heat treatment, to prepare Fe nanocrystalline in SiO2. The formation process of Fe granules was monitored by means of conversion electron Mössbauer spectroscopy and the size of which was determined by transmission electron microscopy. The magnetic coercivity of 100 and 70 Oe have been observed at room temperature and 80 K, respectively. A decrease of the coercivity at 80 K is probably caused by the appearance of a multidomain structure in the granules due to reducing the critical radius of single domain.
Properties of doped and undoped crystals of single domain KTiOAsO4
Authors: Cheng L. K. , Cheng L.-T. , Bierlein J. D. , Zumsteg F. C. , Ballman A. A.
Published: July 2002

Large single crystals of KTiOAsO4 (KTA) measuring up to 35×31×58 mm3 (along abc) are grown from the pure potassium arsenate self-fluxes and from the tungstate flux using the seeded high-temperature solution growth technique. Small amounts of Fe2O3, Sc2O3, or In2O3 (∼0.2–0.4 wt %) are added to the melt to promote single-domain formation in the flux-grown crystals. We report here the linear optical and nonlinear optical properties of these crystals. We observed an unusually strong optical birefringence increase with Fe2O3 dopant concentration [δ(nz−nx)∼0.017/wt % Fe]. This increase leads to a blue shift in the second-harmonic generation cutoff wavelength of as much as 37 nm for a ∼0.47 wt % Fe-dopant level in KTA.
Crystallographic tilting resulting from nucleation limited relaxation
Authors: LeGoues F. K. , Mooney P. M. , Chu J. O.
Published: July 2002

We have measured the crystallographic tilt in thick relaxed Si0.7Ge0.3 layers grown on vicinal (001) Si substrates, with and without a step graded intermediate layer, as a function of the angle of miscut away from the exact (001) surface. In both cases, the tilt angle has the same azimuthal orientation as the miscut, but is opposite in sign, and varies linearly with the angle of miscut. The tilt is significantly larger for samples with intermediate graded layers, reaching 0.6° for an angle of miscut of 2°. We interpret these data by noting that relaxation of layers grown on top of a compositionally graded buffer occurs by a nucleation limited mechanism, whereas relaxation in samples grown without graded buffers is glide limited. The miscut affects the activation energy of nucleation, which is an exponential effect, while it linearly changes the glide force applied on dislocations.
Pulsed laser deposition of oriented In2O3 on (001) InAs, MgO, and yttria-stabilized zirconia
Authors: Tarsa E. J. , English J. H. , Speck J. S.
Published: July 2002

Oriented In2O3 films have been grown on (001) InAs, MgO, and YSZ substrates using pulsed laser deposition. The films in each case displayed a cube-on-cube orientation relation with respect to the substrate, as determined by in situ RHEED analysis and x-ray θ–2θ measurements. X-ray rocking curve full width at half-maximum values as low as 1.3°, 1.5°, and 0.29° have been obtained for In2O3 layers on InAs, MgO, and YSZ, respectively. An oriented native surface oxide layer was employed to provide an appropriate epitaxial template for aligned growth of In2O3 on InAs substrates, while growths were carried out directly on MgO and YSZ. The not intentionally doped films displayed resistivities on the order of 10−4 Ω cm, with Hall mobilities of 50 cm2/V s measured for In2O3 deposited on YSZ substrates.
New fabrication method for highly oriented J aggregates dispersed in polymer films
Authors: Misawa Kazuhiko , Ono Hiroshi , Minoshima Kaoru , Kobayashi Takayoshi
Published: July 2002

We present a new fabrication method, called ‘‘vertical spin coating,’’ to prepare highly oriented J aggregates dispersed in polymer films. Linear dichroic spectra of the oriented J aggregate of 1,1′-diethyl-2,2′-quinocyanine bromide PIC-Br were measured at 5 K. The dichroic ratio at the peak of J band was 5 to 10, dependent on the preparation conditions. Precise measurement of the dichroism at the J band revealed that the J band is composed of two bands with transition dipole moments perpendicular to each other. The films are stable even at room temperature, and have applications as nonlinear optical devices.
Electrical properties of thermal oxide grown using dry oxidation on p-type 6H-silicon carbide
Authors: Alok Dev , McLarty P. K. , Baliga B. J.
Published: July 2002

The electrical properties of thermal oxides grown on p-type 6H-silicon carbide were investigated during this work. Thermal oxides were grown on 7×1015 cm−3 aluminum doped p-type 6H-silicon carbide at 1275 °C in a dry oxygen ambient. Capacitance-voltage measurement indicated the presence of a large positive charge in the oxide. The interface state density and effective charge density for these oxides was estimated to be 1×1011 cm−2 eV−1 and 8×1012 cm−2 respectively. Bias temperature stress measurement showed the presence of negative bias stress instability and slow trapping.
Laser ablation threshold of YBa2Cu3O6+x
Authors: Dam B. , Rector J. , Chang M. F. , Kars S. , de Groot D. G. , Griessen R.
Published: July 2002

Using projection optics we made a detailed study of the interaction of a spatially uniform 248 nm excimer laser beam and a 99% dense YBa2Cu3O6+x target. Below a threshold fluence of 1 J/cm2 the roughness of the irradiated target increases dramatically due to non-stoichiometric ablation. The overall target surface composition becomes increasingly Y rich and Cu poor, while the opposite is found for the corresponding ablated thin films. Above the threshold fluence the composition of the ablated target surface is conserved. As a result of the energy homogeneity of the laser beam obtained by means of projection optics, the optimization of the deposition parameters has been improved leading to the reproducible fabrication of flat, stoichiometric YBa2Cu3O7 films with Tc0’s over 91 K.
Graded-index diffractive elements by thermal ion exchange in glass
Authors: Salmio Risto-Pekka , Saarinen Jyrki , Turunen Jari , Tervonen Ari
Published: July 2002

High-efficiency diffractive elements with a graded volume distribution of refractive index are proposed, designed, and fabricated using thermal ion exchange in glass. A deliberate use of isotropic diffusion of ions enables us to generate, even with a single binary mask, a structure that acts like a continuous surface-relief profile. The advantages of the proposed method include the ease of cleaning and antireflection coating the flat surface, the absence of alignment problems in the fabrication process, and compatibility with stacked planar optics. A grating beam splitter with three equal-efficiency central orders and 89.7% diffraction efficiency is demonstrated.
Epitaxial growth of SrTiO3 thin films by metalorganic chemical vapor deposition
Authors: Gilbert S. R. , Wessels B. W. , Studebaker D. B. , Marks T. J.
Published: July 2002

Epitaxial SrTiO3 thin films were prepared using low pressure metalorganic chemical vapor deposition. The volatile metalorganic precursors employed were Sr(hexafluoroacetyl acetonate)2⋅tetraglyme and titanium tetraisopropoxide. Single-phase, epitaxial films were deposited on (100)LaAlO3 at a temperature of 810 °C. In-plane epitaxy was verified using x-ray phi scan analysis. The SrTiO3 films exhibit a significant tetragonal distortion with c/a=1.010(±1.6×10−4) at room temperature. No evidence of fluorine contamination is noted by x-ray diffraction or by Auger electron spectroscopy measurements.
Fluorescence rejection in Raman spectroscopy by a gated single-photon counting method
Authors: Watanabe Junji , Kinoshita Shuichi , Kushida Takashi
Published: July 2002

Raman measurements on ethanol containing rhodamine 6G have been carried out by a single-photon counting technique with highly repetitive (∼82 MHz), short-duration (∼5 ps) laser pulses using a time gate as narrow as 31 ps. The Raman-to-fluorescence intensity ratio and the signal-to-noise ratio have been improved by factors of 129 and 4.2, respectively. These values are in good agreement with numerical estimations. This method has also been found to be very effective in reducing dark counts and interfering plasma lines from the laser tube. The optimum width and position of the gate to attain the best signal-to-noise ratio for a given fluorescence decay time and a response function of the experimental system are also discussed.
New polarization-modulation spectrometer for simultaneous circular dichroism and optical rotary dispersion measurements (I): Instrument design, analysis, and evaluation
Authors: Shindo Yohji , Ohmi Yasuhiro
Published: July 2002

The Mueller matrix approach is used for designing, analyzing, and evaluating a new polarization-modulation spectrometer for simultaneous measurements of circular dichroism (CD) and optical rotatory dispersion (ORD). The same approach is applied to commercial CD spectropolarimeters for the evaluation of their performance in order to clarify our new spectrometer. On the basis of the results obtained, our JASCO J-500 CD spectropolarimeter was converted into the new spectrometer. Preliminary experiments indicate that CD and ORD can be measured simultaneously above 400 nm. It is also shown that this new spectrometer can be used for measuring linear dichroism and linear birefringence simultaneously.
Energy spectra and space resolved measurements of fusion reaction protons from plasma focus devices
Authors: Jäger U. , Bertalot L. , Herold H.
Published: July 2002

Methods for ion detection with high spatial and spectral resolution in the energy range 70 keV≤Ed≤5 MeV were developed and applied at plasma focus facilities. Particularly, the fusion reaction protons of the D(d,p) T reaction were studied. Nuclear track detectors LR115A, CR-39, and CR-39/PM355 with aluminum foil filters in front were used and calibrated using a Thomson analyzer. The influence of the azimuthal magnetic field on the trajectories of the charged particles was calculated using an ion optical code.
New surface wave launchers for sustaining plasma columns at submicrowave frequencies (1–300 MHz)
Authors: Moisan M. , Zakrzewski Z.
Published: July 2002

We describe new surface wave launchers intended to sustain plasma columns with high-frequency (hf) power in the range of 1–300 MHz. This frequency range complements that of the existing surface wave plasma generators (surfatron and surfaguide launchers), which are best suited to operate in the microwave domain (≳300 MHz). With the addition of this new type of launchers, called Ro-box, it is now feasible to achieve a surface wave produced plasma column at applied frequencies ranging from 1 MHz to 10 GHz. The possibility of using the same physical hf coupling mechanism (surface wave propagation) over such a broad frequency band is an unprecedented situation with hf produced plasmas. This is of interest for both fundamental and applied physics, as it allows frequency effect investigations and frequency optimization of plasma processes. The new devices can be made so that the wave-launching and the impedance-matching functions are physically separated, leading to a modular design, a feature that facilitates changing the plasma tube diameter and the operating frequency range. A further advantage of the new devices is that their launching section can be implemented around the discharge tube more compactly than with the other surface wave launchers.
Millimeter-wave interferometer for measuring plasma electron density
Authors: Domier C. W. , Peebles W. A. , Luhmann N. C.
Published: July 2002

A simple, low-cost millimeter-wave interferometer has been developed to measure the electron density of laboratory-type plasmas with densities n≤2×1012 cm−3 . Two 38.0-GHz Gunn oscillators, whose oscillation frequencies are offset by 40 MHz, are used in a heterodyne configuration. The high intermediate frequency allows the use of inexpensive, free-running mechanically tuned Gunn oscillators and permits this system to be utilized in the study of density fluctuations. A quadrature phase comparator is used to give simultaneously both the sine and cosine components of the plasma interference signal. The phase noise of the system is found to be <0.1°, with a settling time <100 ns. The system is to be used on a laboratory plasma to look at both the integrated electron density and the level of density fluctuations.
Streak tube with an electron-bombardment silicon diode array
Authors: Lucht H.
Published: July 2002

The electrode configuration and magnetic electronoptics of a newly designed streak tube (TDS200) are described. By using a silicon diode array of a Vidicon instead of a phosphor screen an electronic gain of more than 1200 and a direct electronic readout are attained. The results of our theoretical studies show a temporal resolution of better than 2.5 ps when the photocathode is illuminated at a wavelength of 500 nm. Measurements for the time-resolved fluorometry are presented.
Measurement of absolute thermoelectric power by photoemission
Authors: Wertheim G. K. , Buchanan D. N. E.
Published: July 2002

It is pointed out that a determination of the temperature dependence of the Fermi cutoff in the conduction band of a metal provides a means of measuring the thermal emf of a single metal, as well as the absolute thermoelectric power, without use of a reference substance. The energy of the Fermi cutoff is determined by photoemission. The method is illustrated by a crude determination of the thermal emfs of copper and constantan.
An amplifier for a fast semiconducting bolometer
Authors: Boragno C. , Buatier de Mongeot F. , Shen Y. , Racca L. , Valbusa U.
Published: July 2002

A new amplifier, designed to operate with fast semiconducting bolometers, is presented. Based on current detection of the bolometer signal, it allows one to obtain good sensitivity with response times of about 10 ns without using cryogenic electrical components. The amplifier was used to detect heat pulses propagating in a Si crystal.