bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of Escherichia coli O157: H7 and Non-O157 Strains in Meat, Human Stool, Abattoir Wastewater and Hygiene Practices among Meat Peddlers in Port Harcourt, Nigeria
Authors: Ujoh Ngozi A. , Amala Smart E. , Nwokah Easter G. , Wachukwu Confidence K.
Published: June 2022

Aim: To determine the prevalent rates of Escherichia coli O157: H7 and non-O157 strains in of isolates from meat, human stool and abattoir waste water, collected from selected sources in Port Harcourt, Nigeria.

Study Design: Case-controlled study.

Place and Duration of Study: Selected places in Port Harcourt, Rivers State, Nigeria, between November, 2020 to November, 2021.

Methodology: Three hundred and forty -nine (349) samples were analyzed, 80 meat and 63 waste waters from five abattoirs cited in the city, 46 meat samples from five selected sites sold by roadside butchers, 109 patient stool samples and 30 stool samples from food sellers, in addition to 20 stool samples from healthy subjects and 1 commercial bottled water which served as control samples. Tryptone soya broth (TSB) as an enrichment media, selective agar media namely; Eosin methylene blue agar, cefixime tellurite-sorbitol MacConkey agar (CT-SMAC), Chromagar STEC were used to isolate STEC from the samples and serology done with O157 latex agglutinating kit to confirm E. coli O157:H7 serogroup.

Results: The results showed that Isolation rates obtained for E. coli O157:H7 and non O157 respectively were: abattoir meat 11(13.8%);13(16.3%), roadside meat 5(10.9%); 10(21.7%), clinical stool 7(6.4%); 27(24.7%), food sellers’ stool 4(13.3%);6(20%), waste abattoir water 2(3%); 14(22.2%). Food sellers and abattoir effluents were found to be potential sources of STEC dissemination in Port Harcourt. The data obtained were statistically analyzed using chi- square which showed that there was no significant difference (p < 0.05) in the rate of isolation of E. coli O157: H7 and non- O157 strain from the samples.

Conclusion: The detection of E.coli O157:H7 and non-O157 strains in raw meat (food), environment and clinical samples in Port Harcourt may give rise to a potential widespread public health hazard if strict adherence to proper hygiene management are not place to regulate food processing in other to reduce contamination and foodborne infections.
Socio Economic Impact of Skill Development Training Program on Employment Status of Rural Youth: A Case of RSETI, Gujarat
Authors: Dodiya Jaydipkumar , Panigrahy Shakti Ranjan , Nayak Archit Kumar , Mohapatra Arpita
Published: June 2022

Aims: This paper investigated the need and socio-economic impact of skill development training program on employment status of rural youth by using the case of Rural Self Employment Training Institute (RSETI) located in Nadiad, Gujarat.

Study Design: A random sample of 120 trainees who took skill development training during the period 2013-16 were selected for the study. Data collected were subjected to in-depth tabular analysis as well as statistical techniques such as Principal component analysis (PCA).

Results: The study showed that the skill training imparted by RSETI was widely taken by rural youths with the motive of starting a new venture. The impact of training program on occupational status of trainees showed that the training significantly raised the level of self-employment in the youths. The economic impact of the training indicated that the trainees were either monetary motivated or they felt improvement in the job quality.  On the basis of social impact, the trainees were segmented into four broad categories namely self-employment seekers, prestige seekers, confident & positive respondents and efficient respondents.

Conclusion: The study suggested that selective training methods should be devised, based on interests and capabilities of the individuals, that were leaders, entrepreneurs, Pessimist, self-conscious and self-motivated categories, to get the effective results.
Phosphorylation of human plasminogen activators and plasminogen
Authors: Barlati Sergio , De Petro Giuseppina , Bona Chiara , Paracini Francesco , Tonelli Mariella
Published: July 2002

Plasminogen (PG), urokinase‐type plasminogen activator (u‐PA) and tissue‐type PA (t‐PA) are the main molecules involved in fibrinolysis and in many other physiological and pathological processes. In the present study we report that human t‐PA, purified from human melanoma cells, and PG, purified from human plasma, both contain P‐Tyr residues, as revealed by immunoblotting analyses with monoclonal anti‐P‐Tyr antibodies. In addition HPLC amino acid analysis of acid‐hydrolyzed t‐PA, PG and u‐PA, shows that: (i)P‐Ser and P‐Tyr residues are present in t‐PA; (ii)P‐Thr and P‐Tyr are present in PG; (iii) P‐Ser, P‐Thr and P‐Tyr are present in u‐PA. The utilization of monoclonal anti‐P‐Ser and anti‐P‐Thr antibodies in immunoblotting experiments has confirmed these data which indicate that phosphorylation is a common feature of PAs and of PG.
Primary squamous cell carcinoma of the endometrium
Authors: Aikins J.K. , Gisser S. , Qasim S. , Saul H. , Rocereto T.
Published: July 2002

All reported cases of primary squamous cell carcinoma of the endometrium and the effectiveness of the different treatment modalities in the world literature are reviewed. We present the first reported case of primary squamous cell carcinoma of the endometrium treated by radical hysterectomy, pelvic and para‐aortic lymphadenectomy. The patient is without signs of disease 4 years after surgery. This is the longest follow‐up of all reported cases. There are very few cases from which to conclusively predict the best mode of therapy. The current standard of treatment is total abdominal hysterectomy and bilateral salpingo‐oophorectomy with or without pelvic and para‐aortic lymph node sampling, depending on the histology and depth of the myometrial invasion. Adjuvant therapy includes radiation therapy according to the extent of disease.
Large accumulation of mRNA and DNA point modifications in a plant senescent tissue
Authors: Pla Maria , Jofré Anna , Martell Maria , Molinas Marisa , Gómez Jordi
Published: July 2002

Although nucleic acids are the paradigm of genetic information conservation, they are inherently unstable molecules that suffer intrinsic and environmental damage. Oxidative stress has been related to senescence and aging and, recently, it has been shown that mutations accumulate at high frequency in mitochondrial DNA with age. We investigated RNA and DNA modifications in cork, a senescent plant tissue under high endogenous oxidative stress conditions. When compared to normally growing young tissue, cork revealed an unexpected high frequency of point modifications in both cDNA (Pn=1/1784) and nuclear DNA (Pn=1/1520). Cork should be viewed as a mosaic of genetically heterogeneous cells. This has biological implications: it supports somatic mutation models for aging and challenges ‘single cDNA clone’ as descriptor for the molecular genetics of senescent tissues.
The Krüppel‐like transcriptional factors Zf9 and GKLF coactivate the human keratin 4 promoter and physically interact
Authors: Okano Jun-ichi , Opitz Oliver G. , Nakagawa Hiroshi , Jenkins Timothy D. , Friedman Scott L. , Rustgi Anil K.
Published: July 2002

Zf9/CPBP/KLF6 is a widely expressed member of the Krüppel‐like family of transcriptional factors which regulates gene expression in hepatic stellate cells. Because of its ubiquitous expression including in the esophagus, we have explored its function in the esophageal squamous epithelium, a model system to study cellular proliferation and differentiation. Reverse transcription‐PCR (RT‐PCR) and Western blot analyses revealed that Zf9 was highly expressed in human esophageal squamous cancer cell lines. Additionally, Zf9 localizes to the esophageal squamous epithelium by immunohistochemistry. Using transient transfection, Zf9 transactivates the human keratin 4 (K4) promoter reporter gene construct in a subset of the esophageal cancer cell lines through indirect mechanisms. Co‐transfection of Zf9 and GKLF/KLF4, which is also a member of the Krüppel‐like factors and expressed in the esophageal squamous epithelium, leads to coactivation in an additive fashion. Furthermore, we demonstrate that there is a physical interaction between GKLF and Zf9, a novel finding for Krüppel‐like family members.
Different membrane targeting of prostaglandin EP3 receptor isoforms dependent on their carboxy‐terminal tail structures
Authors: Hasegawa Hiroshi , Katoh Hironori , Yamaguchi Yoshiaki , Nakamura Kazuhiro , Futakawa Satoshi , Negishi Manabu
Published: July 2002

Mouse prostaglandin EP3 receptor consists of three isoforms, EP3α, β and γ, with different carboxy‐terminal tails. To assess the role of their carboxy‐terminal tails in membrane targeting, we examined subcellular localization of myc‐tagged EP3 isoforms expressed in MDCK cells. Two isoforms, EP3α and EP3β, were localized in the intracellular compartment but not in the plasma membrane, while the EP3γ isoform was found in the lateral plasma membrane and in part in the intracellular compartment. Mutant EP3 receptor lacking the carboxy‐terminal tail was localized in the intracellular compartment but not in the plasma membrane. Thus, EP3 isoforms differ in subcellular targeting, and the carboxy‐terminal tails play an important role in determination of the membrane targeting of EP3 receptor.
The Rab3‐interacting molecule RIM is expressed in pancreatic β‐cells and is implicated in insulin exocytosis
Authors: Iezzi Mariella , Regazzi Romano , Wollheim Claes B.
Published: July 2002

The putative Rab3 effector RIM (Rab3‐interacting molecule) was detected by Northern blotting, RT‐PCR and Western blotting in native pancreatic β‐cells as well as in the derived cell lines INS‐1E and HIT‐T15. RIM was localized on the plasma membrane of INS‐1E cells and β‐cells. An involvement of RIM in insulin exocytosis was indicated by transfection experiments of INS‐1E cells with the Rab3 binding domain of RIM. This domain enhanced glucose‐stimulated secretion in intact cells and Ca2+‐stimulated exocytosis in permeabilized cells. Co‐expression of Rab3A reversed the effect of RIM on exocytosis. These results suggest an implication of RIM in the control of insulin secretion.
The modulating actions of sulfonylurea on atrial natriuretic peptide release in experimental acute heart failure
Authors: Chen Horng H. , Oh Karen Y. , Terzic Andre , Burnett John C.
Published: July 2002

Objectives

This study defined the modulating actions of sulfonylurea on acute release of atrial natriuretic peptide (ANP) in experimental acute heart failure.

Background:

Sulfonylurea drugs, blockers of cardioprotective ATP‐sensitive K+ (KATP) channels, may increase the risk of early cardiovascular mortality. In cardiovascular diseases such as acute heart failure, early release of ANP is essential for cardiorenal homeostasis. Although KATP channels regulate secretion of hormones, such as insulin, it is unknown whether sulfonylureas interfere with ANP release in acute heart failure.

Methods

The effects of acute administration of glyburide (0.3 mg/kg), a prototype sulfonylurea, on ANP release and sodium excretion were measured in vivo in a canine model of pacing‐induced acute heart failure characterized by acute atrial stretch. Immunoreactivity, in atrial tissue, for ANP and the KATP channel subunit, Kir6.2, was determined using specific antibodies.

Results

With increased left atrial pressure in heart failure, plasma levels of ANP increased rapidly and peaked within 25±3 min. Glyburide delayed the time required for peak plasma ANP secretion to 48±5 min. This resulted in reduced natriuresis from 84±17 μEq/min in the absence of glyburide, to 34±9 μEq/min in the presence of glyburide. However, glyburide did not alter the renal natriuretic responsiveness to exogenously administered ANP in normal dogs. In atrial tissue, both ANP and the KATP channel subunit, Kir6.2, displayed strong immunoreactivity and co‐localization.

Conclusions

Glyburide delays release of ANP in acute heart failure resulting in impaired natriuresis. This cannot be ascribed to an antinatriuretic effect on the kidney, but rather may be due to interference with KATP channel‐dependent ANP secretion from the atrium. Such adverse outcome of sulfonylurea drug use could reduce the compensatory capacity to preserve cardiorenal homeostasis in acute heart failure.
Enzymatic Hydrolysis of Waste Office Paper Using Viscosity as Operating Parameter
Authors: Park Enoch Y. , Michinaka A. , Okuda N.
Published: July 2002

Enzymatic hydrolysis of waste office (WO) paper with feeding WO paper in a reactor was investigated using apparent viscosity as operating parameter. Since the apparent viscosity was correlated with the concentration of pulping WO paper, the amount of hydrolyzed WO paper was assumed by measuring the decrease in the apparent viscosity. Then the amount of hydrolysis WO paper and the amount of enzyme corresponding to the desired ratio were fed into the reactor. When the WO paper and 1% (to the amount of WO paper) enzyme were fed to the hydrolytic reaction, 87 g/L of reducing sugar (RS) with a hydrolytic yield of 42.2% was obtained for a 24‐h hydrolysis. However, when nonpulping WO paper and 5% (to the amount of WO paper) enzyme were fed to the hydrolytic reaction, 120 g/L of RS with a hydrolytic yield of 40% was obtained for a 24‐h hydrolysis. Therefore, the RS concentration from this hydrolysis process feeding WO paper using apparent viscosity as operating parameter may be of sufficient concentration to serve as a carbon source in microorganism culture or chemical feedstock.
Stationary and Microcarrier Cell Culture Processes for Propagating Japanese Encephalitis Virus
Authors: Wu Suh‐Chin , Huang Gloria Ya‐Ling
Published: July 2002

Inactivated mouse‐brain‐derived vaccines for Japanese encephalitis virus (JEV) have been used for many years. Recently, attempts have been made to employ cultured Vero cells to replace mouse brain tissues for developing cell‐culture‐derived vaccines that will be more suitable for worldwide usage. In this study, JEV replication processes in Vero and BHK cells and between stationary and microcarrier culture systems were investigated. Our results demonstrated that a stationary Vero cell culture system produced higher viral titers of JEV, including the Beijin‐1 vaccine strain and the attenuated strain CH2195LA, than microcarrier culture did. BHK cells showed less significant differences in their replication kinetics between stationary and microcarrier cultures. Reducing serum concentration during infection led to an overall decrease of JEV production in Vero cells but an increase in BHK cells. By establishing a complete serum‐free Vero cell culture, the microcarrier system resulted in a more than 4‐log lowered yield compared to that of the stationary culture for JEV production. Thus, the stationary culture is the most efficient system for JEV production from cultured Vero cells.
Characterization of Patatin Esterase Activity in AOT‐Isooctane Reverse Micelles
Authors: Jiménez M. , Escribano J. , Gandía‐Herrero F. , Chazarra S. , Cabanes J. , García‐Carmona F. , Pérez‐Gilabert M.
Published: July 2002

Patatin is a family of glycoproteins that accounts for 30–40% of the total soluble protein in potato ( Solanum tuberosum L.) tubers. This protein has been reported not only to serve as a storage protein but also to exhibit lipid acyl hydrolase (LAH) activity. In this study patatin is characterized in AOT‐isooctane reverse micelles. The influence on the enzymatic activity of characteristic parameters of reverse micelles, wo (= H2O/AOT), and the percentage of H2O, θ, were investigated. The results obtained show that patatin esterase activity varies with wo but remains constant throughout the range of θ values studied. The variation with wo showed that the activity follows an S‐shaped behavior pattern, reaching a maximum at about wo = 20 for 2% H2O. Patatin esterase activity was compared with p‐nitrophenyl (PNP) fatty acid esters of different chain lengths. The activity was much higher for PNP‐caprylate. The pH optimum was 6.0, different from the value obtained when patatin esterase activity was measured in mixed micelle systems. The optimal temperature was 35 °C, above which the activity decreased to almost zero. The kinetic parameters were also evaluated ( Km = 10 mM, Vm = 158 μM/min, Vm/ Km = 15.8 × 10−3 min−1). This paper shows the suitability of reverse micelles for measuring patatin esterase activity, since it allows the study of the enzyme in similar conditions to that prevailing in vivo.
Influence of Morphology on Product Formation in Aspergillusawamori during Submerged Fermentations
Authors: Johansen Claus L. , Coolen Leon , Hunik Jan H.
Published: July 2002

The relationship between fungal morphology and heterologous protein production was examined for an Aspergillus awamori strain during a series of fermentations with a batch phase followed by a fed‐batch phase. Agitation rate and inoculation concentration were used as controlled variables to generate different fungal morphologies in 20‐dm3 stirred tank reactors. Morphology was quantitatively characterized using Image Analysis. The different agitation rates and inoculum concentrations had large effects on the development in hyphal length and number of tips during the fermentations. A reduced inoculum concentration resulted in a more branched mycelium. The different agitation rates affected the morphology after 30 h of fermentation significantly but did not affect the start time of fragmentation. A 3‐fold increase in hyphal length increased the apparent viscosity by a factor of 7. The observed morphological differences had only a limited effect on product formation, suggesting that the structural features such as hyphal length and number of tips are of less importance for product formation. The primary effect of morphology on product formation is due to viscosity.
Platelet glycoprotein IIb/IIIa blockade with tirofiban: effect on aggregation caused by P256, an antibody to human IIb/IIIa receptors
Authors: Fisher Ian , Robinson Paul , Ritter James M.
Published: July 2002

Aims
 P256 is a divalent antibody which aggregates human platelets by interaction with glycoprotein (GP) IIb/IIIa receptors. We investigated the effect of tirofiban, an antagonist of the GP IIb/IIIa receptor, on P256‐mediated platelet aggregation.

Methods
 Responses to agonists were measured turbidometrically at 37° C in stirred citrated platelet‐rich plasma from venous blood samples from healthy human volunteers. Inhibitory effects were determined by comparison with aggregation to the same concentration of agonist in a vehicle treated sample.

Results
 Tirofiban inhibited a near maximally effective dose of P256 (10−7 mol l−1 ) with an IC50 of 9.3×10−8 mol l−1. Tirofiban (10−7 mol l−1 ) inhibited responses to arachidonic acid, U46619 and P256 similarly, whereas aspirin (1.1×10−4 mol l−1 ) inhibited arachidonic acid more effectively than P256 (P<0.007 by anova ).

Conclusions
 Tirofiban potently and selectively inhibits P256‐stimulated aggregation of human platelets.
Thalidomide in multiple myeloma: lack of response of soft‐tissue plasmacytomas
Authors: Bladé Joan , Perales María , Rosiñol Laura , Tuset Montserrat , Montoto Silvia , Esteve Jordi , Cobo Francesc , Villela Luis , Rafel Montserrat , Nomdedeu Benet , Montserrat Emili
Published: July 2002

Thalidomide is active in patients with refractory myeloma. Seventeen patients (nine men/eight women, median age 73 years) with multiple myeloma (MM) were treated with thalidomide. Fifteen patients had refractory disease and two untested relapse. The median dose of thalidomide was 500 mg (range, 200–800 mg). Nine of the 17 patients (53%) responded. The response rate was significantly higher in patients with no extramedullary disease than in those with soft tissue masses (75% CI: 43–95% versus 0%; P = 0·01)). Of note, no decrease in the size of soft tissue plasmacytomas was observed in all the five patients who had extramedullary involvement. This data suggests that the mechanism of action and effectiveness of thalidomide might depend on the site of the tumour cells.
Surface Treated Catheters with Ion Beam Based Process for Blood Access
Authors: Bambauer Rolf , Mestres Pedro , Schiel Ralf , Schneidewind Jana Maria , Latza Reinhard , Bambauer Silke , Sioshansi Piran
Published: July 2002

Abstract: Infection, thrombosis, and stenosis are among the most frequent complications associated with blood contacting catheters. Because these problems are usually related to surface properties of the base catheter material, surface treatment processes such as ion implantation and ion beam assisted deposition (IBAD) (silver based coatings) can be used to mitigate such complications. Because these ion beam based processes affect only the near‐surface region (approximately the outer 1 μm), there is little effect on bulk material properties. This study evaluated silver coated large bore catheters used for extracorporeal detoxification. In a 135 patient prospective study, 170 large bore catheters were inserted into the internal jugular or subclavian veins. Seventy‐eight surface treated catheters (Spi‐Argent, Spire Corporation, Bedford, MA, U.S.A.; n = 32 acute catheters, n = 46 long‐term catheters) were inserted in 55 patients. Ninety‐two untreated catheters placed in 80 patients served as controls (n = 40 acute catheters, n = 52 long‐term catheters). After removal, the catheters were cultured for bacterial colonization using standard microbiologic assays. They also were examined using a scanning electron microscope (SEM). Bacterial colonization was observed in 7% of the treated catheters compared with 35.3% of untreated catheters. The SEM investigations showed all treated catheters to possess low thrombogenicity. Results of the study indicate that ion beam based processes can be used to improve thrombus and infection resistance of blood contacting catheters.
Theory of polymer ablation
Authors: Mahan G. D. , Cole H. S. , Liu Y. S. , Philipp H. R.
Published: July 2002

A new formula is presented for the etch depth l per pulse of an excimer laser of fluence F. Incremental ablation is defined as the etch depth per pulse after many pulses. We show that l is proportional to F, rather than ln(F).
Phase diagram of BinSrCaCu3−nOy on the line 1≤n≤2
Authors: Tomomatsu Kazuhiko , Kurosaka Akihito , Tominaga Haruo , Takayama Teruyuki , Fukuda Osamu , Osanai Hiroshi
Published: July 2002

The pseudobinary phase diagram of BinSrCaCu3−nOy was determined on the line 1≤n≤2 upon which the low Tc superconductor phase [Bi2(Sr,Ca)3Cu2Oy] and the semiconductor phase [Bi2(Sr,Ca)2CuOy] are located. The liquidus line of the superconductor phase was found to lie in the region 1.6≤n≤1.875. A small quantity of transparent crystal was found even in the melting phase, which suggests that samples with these compositions do not melt homogeneously. Therefore, single crystals or single-phase superconductor materials apparently can be grown from the liquid phase by obtaining a homogeneous melt in this region.
Digital etching of GaAs: New approach of dry etching to atomic ordered processing
Authors: Meguro T. , Hamagaki M. , Modaressi S. , Hara T. , Aoyagi Y. , Ishii M. , Yamamoto Y.
Published: July 2002

A new approach to dry etching of GaAs, digital etching, has been demonstrated. In digital etching, the etchant and an energetic beam, which induces chemical sputtering at the surface, alternately impinge onto the surface. Electrons and Cl2 gas were used as the energetic beam and the etchant, respectively, in the present experiment. Etching rates of 1/3 monolayer/cycle, independent of Cl2 flux and electron current density, were obtained. The present results show that an inherent self-limiting mechanism is involved and that the etching process is limited by the adsorption of etchant. This digital etching technique is expected to be applied to the fabrication of well-defined quantum wire and quantum box structures.
Band offset variations at Ge/GaAs (100) interfaces
Authors: Dahmen M. , Rau U. , Kawanaka M. , Sone J. , Werner J. H.
Published: July 2002

We analyze the band offsets at Ge/GaAs (100) interfaces by internal photoemission, capacitance/voltage and current/voltage measurements. The conduction band offset varies with Ge growth temperature from −0.025 eV for 300 °C to 0.33 eV for 500 °C. We attribute these drastic offset variations to different microscopic interface configurations at the polar Ge/GaAs (100) heterojunction.
Mass-resolved ion energy measurements at the grounded electrode of an argon rf plasma
Authors: Snijkers R. J. M. M. , van Sambeek M. J. M. , Kroesen G. M. W. , de Hoog F. J.
Published: July 2002

The mass-resolved ion energy distribution (IED) at the grounded electrode has been determined in a 13.56-MHz parallel-plate plasma in argon. The IED is determined of Ar+, Ar2+, Ar2+, ArH+, H3O+, and H3+ for several plasma conditions. At pressures higher than 10 mTorr, collisions in the sheath become important. The IED of Ar+ is particularly defined by charge exchange collisions in the sheath while the IED of the other ions shows only features generated by elastic scattering. This is confirmed by Monte Carlo simulations. The measurements clearly show the necessity of simultaneous mass and energy separation, rather than the nonmass-resolved IED reported in the literature.
Schottky barrier photodetector based on Mg-doped p-type GaN films
Authors: Asif Khan M. , Kuznia J. N. , Olson D. T. , Blasingame M. , Bhattarai A. R.
Published: July 2002

In this letter we report the fabrication and characterization of Schottky barrier photodetectors on p-type GaN films. These films were grown over basal plane sapphire substrates using low pressure metalorganic chemical vapor deposition and magnesium as the p-type dopant. The current-voltage and capacitance-voltage characteristics were measured for Ti/Au Schottky barriers for a film with a p doping of 7×1017 cm−3. We measured a 1.5 V forward turn on and a 3 V reverse breakdown. The zero bias responsivity of a detector with 1 mm2 area was measured to be 0.13 A/W. For these photovoltaic detectors, the photoresponse was nearly constant from 200 to 365 nm and fell sharply by several orders of magnitude for wavelengths above 365 nm.
Role of arsenic in the heteroepitaxy of Ge/GaAs
Authors: Leycuras A. , Lee M. G.
Published: July 2002

During the heteroepitaxy of Ge on GaAs, arsenic diffuses from the GaAs substrates and hence is present in the Ge epilayer. It has been shown that As is incorporated into the layer but also segregated to the surface. The Ge growth is monitored in situ by laser reflectometry, and it gives the thickness, the growth rate, and the morphology of the layer. It is shown here that a too large surface concentration of As due to intentional doping can block the Ge growth. Atomic force micrographs of the morphological defects (pyramidlike void and large steps) suggest that these defects are due to local segregated excess As concentrations caused by the step advance. It is shown that the density of defects as well as the thickness at which they appear are characterized by the same activation energy of ∼1 eV.
Atomic force microscopic study of rubbed polyimide films
Authors: Zhu Yang-Ming , Wang Lin , Lu Zu-Hong , Wei Yu , Chen X. X. , Tang J. H.
Published: July 2002

Rubbed polyimide films have been studied by atomic force microscopy from micrometer to nanometer scales. On a large scale, oriented scratches and microstructures due to rubbing have been observed, while on a nanometer scale, oriented polyimide aggregates are visible. The alignment of liquid crystals on these films is thus discussed.
Rubbed polyimide films studied by scanning force microscopy
Authors: Kim Y. B. , Olin H. , Park S. Y. , Choi J. W. , Komitov L. , Matuszczyk M. , Lagerwall S. T.
Published: July 2002

The surfaces of rubbed polyimide films for aligning liquid crystal have been studied by atomic force microscopy. The unrubbed films consisted of randomly distributed polyimide clusters of different sizes. On the rubbed surface, however, the clusters are aligned in long chains along the rubbing direction. The cluster chains were separated by about 100 nm for small rubbing strength. For higher strength the cluster chains coalesced into wider ones.
p-type conduction in Mg-doped Ga0.91In0.09N grown by metalorganic vapor-phase epitaxy
Authors: Yamasaki S. , Asami S. , Shibata N. , Koike M. , Manabe K. , Tanaka T. , Amano H. , Akasaki I.
Published: July 2002

p-type conduction in InN-containing nitrides doped with Mg has been achieved by metalorganic vapor-phase epitaxy. The hole concentration at room temperature is as high as 7×1017 cm−3. The activation energy of a Mg acceptor is estimated to be 204 meV. D–A pair emission with peak wavelength of about 405 nm is enhanced by thermal annealing.
Construction of compact electron storage ring JSR
Authors: Yokomizo H. , Yanagida K. , Sasaki S. , Harami T. , Konishi H. , Mashiko K. , Ashida K. , Harada S. , Hashimoto H. , Iizuka M. , Kabasawa M. , Nakayama K. , Yamada K. , Suzuki Y.
Published: July 2002

A compact electron storage ring (JSR) is under construction in order to study accelerator technologies and to be used as the test ring aiming at a highly brilliant synchrotron radiation facility (6–8 GeV). The JSR lattice is a double-focusing achromatic type. The circumference is 20.5 m. However, even in this small ring, one straight section with a length of ∼1.5 m, where the dispersion is free, is provided for the insertion device study. The electron beam is supplied by the linac with an energy of 150 MeV, and the stored energy is slowly increased up to 300 MeV. Power supplies of all magnets and the rf system are controlled by a real-time computer through optical fiber links, and signals of beam monitors are stored in the same computer so that it is easy to test any type of control procedures.
Novel electromagnetic field probes with ultrasonic transmission lines for field measurements with minimum interaction
Authors: Dürr W. , Oppelt R.
Published: July 2002

Electromagnetic field probes are described which use ultrasonic transmission lines for signal transmission from a small electric or magnetic measuring dipole to the data processing unit. These transmission lines are made of nonmetallic material with low permittivity and permeability so that its interaction with the field to be measured is minimum. In particular, there is no evidence of energy leakage via surface or sheath waves, which normally cause problems when usual metallic connecting cables are used. This is especially important when measuring near fields of antennas or fields in resonators with high Q factors. Wide-band operation was achieved by amplitude modulating the field to be measured at a low frequency. The purpose of this modulation is to create a low-frequency (kHz) signal which can be transmitted via an ultrasonic line, designed to resonate at this low frequency. The radio frequency (rf) itself can extend over a broad range since the ultrasonic line does not transmit this frequency directly. Since the ultrasonic line is operated at a low frequency, its design and manufacture including ultrasonic transducers are essentially simple, even for field probes working in the gigahertz range. The design of the transmission line and of the measuring dipoles with demodulation circuitry are described. The probe performance is discussed for a magnetic field probe used for field measurements in resonant antennas for magnetic resonance imaging in the frequency range up to about 200 MHz. A typical field measurement result is presented for this application.
Surface-enhanced Raman optical data storage: A new optical memory with three-dimensional data storage
Authors: Vo-Dinh T. , Stokes D. L.
Published: July 2002

A new optical data storage technology based on the surface-enhanced Raman scattering (SERS) effect has been developed for high-density optical memory and three-dimensional data storage. With the surface-enhanced Raman optical data storage (SERODS) technology, the molecular interactions between the optical layer molecules and the substrate are modified by the writing laser, changing their SERS properties, so that they are encoded to store information as bits. Since the SERS properties are extremely sensitive to molecular microenvironments, very small ‘‘spectrochemical holes’’ approaching the diffraction limit can be produced for the writing process. The SERODS device uses a reading laser to induce the SERS emission of molecules on the disk and a photometric detector tuned to the frequency of the Raman spectrum to retrieve the stored information. The results illustrate that SERODS is capable of three-dimensional data storage.
Quantum device simulation with a generalized tunneling formula
Authors: Klimeck Gerhard , Lake Roger , Bowen R. Chris , Frensley William R. , Moise Ted S.
Published: July 2002

We present device simulations based on a generalized tunneling theory. The theory is compatible with standard coherent tunneling approaches and significantly increases the variety of devices that can be simulated. Quasi-bound and continuum states in the leads are treated on the same footing. Quantum charge self-consistency is included in the leads and the central device region. We compare the simulated I–V characteristics with the experimental I–V characteristics for two complex quantum device structures and find good agreement.
X-ray magnetic Bragg scattering topography from Fe3O4
Authors: Kawata Hiroshi , Mori Koichi
Published: July 2002

A first methodological success of x-ray magnetic Bragg scattering topography from a Ferri-magnetic Fe3O4 single crystal is described. The flipping ratio on the magnetic Bragg scattering intensity can be enhanced by using a resonant effect at the Fe K-absorption edge. The domain formation including the direction of the spontaneous magnetization can be determined from the obtained topographic image.
Description of a single modular optical setup for ellipsometry, surface plasmons, waveguide modes, and their corresponding imaging techniques including Brewster angle microscopy
Authors: Harke M. , Teppner R. , Schulz O. , Motschmann H. , Orendi H.
Published: July 2002

A versatile modular setup is described which incorporates ellipsometry, surface plasmon spectroscopy, waveguide modes, their corresponding imaging techniques and Brewster angle microscopy in a single instrument. The important design criteria are discussed with special emphasis given to the requirements imposed by imaging under an oblique angle of incidence. Several experimental examples demonstrate the power of the instrument. Imaging nullellipsometry of a patterned monolayer on a highly reflecting support demonstrates a lateral resolution of approximately 1 μm and an accuracy in the thickness determination in the sub-nm region. The localization of the evanescent field of a surface plasmon was exploited to characterize adsorption layers in turbid and thus highly scattering solutions. An example of how an anisotropic sample can be characterized with the aid of waveguide modes is provided.
Cluster formation and uranium photoionization in the afterglow of a pulsed hollow cathode lamp
Authors: Neri J. W. , Silveira C. A. B. , Rodrigues N. A. S. , Schwab C. , Riva R. , Destro M. G. , Mirage A.
Published: July 2002

Uranium photoionization was observed in the afterglow of pulsed hollow cathode lamps illuminated by a dye laser tuned near the electronic transition around 591.5 nm (L605−16 900 cm−1 M77). The photoionization signal was used to monitor the time evolution of the ground state uranium vapor density in the cathode hole. Lifetimes over 1 ms were measured for the uranium vapor; that makes this device attractive for multistep photoionization spectroscopy. The obtained results lead to the conclusion that these long times are due to cluster formation in the afterglow.
Ca and O ion implantation doping of GaN
Authors: Zolper J. C. , Wilson R. G. , Pearton S. J. , Stall R. A.
Published: July 2002

p- and n-type doping of GaN have been realized by ion implantation of Ca and O, respectively. Rapid thermal annealing at 1100 °C or higher is required to achieve p-type conduction in Ca or Ca+P implanted samples with an estimated ionization level of 169 meV and a corresponding activation efficiency of ∼100%. This is the first experimental report of an acceptor species in GaN, other than Mg, with an ionization energy level less than 180 meV. O-implanted GaN displays an ionization level of ∼29 meV but with an activation efficiency of only 3.6% after a 1050 °C anneal that may result from insufficient vacancy generation for the lighter O ion or from the existence of a second, deeper O energy level. Neither Ca or O displayed measurable redistribution, based on secondary ion mass spectrometry measurements, even after a 1125 °C anneal.
A sulfur passivation for GaAs surface by an organic molecular, CH3CSNH2 treatment
Authors: Lu E. D. , Zhang F. P. , Xu S. H. , Yu X. J. , Xu P. S. , Han Z. F. , Xu F. Q. , Zhang X. Y.
Published: July 2002

A sulfur passivation method for GaAs, CH3CSNH2 treatment has been developed. It is quite effective for removing the surface oxide layer and forming the sulfide passivation layer on GaAs surface. The enhancements of the PL intensity reveal the reduction of the surface recombination velocity and the reduction of density of defect states by this treatment. The synchrotron radiation photoemission spectroscopy measurements show that sulfur atoms bond both Ga and As atoms. After being annealed, a stable sulfur passivation layer is terminated on the surface due to the As2S3 component react with GaAs into the GaS component.
Optical properties of tensile-strained wurtzite GaN epitaxial layers
Authors: Chichibu S. , Azuhata T. , Sota T. , Amano H. , Akasaki I.
Published: July 2002

Photo-modulated electroreflectance and photoluminescence spectra of wurtzite GaN epilayers grown on a 6H-SiC (0001)Si or a Si (111) substrate were measured as a function of temperature. The valence band structure of a biaxially tensile-strained (−0.15% in c axis) epilayer was drastically changed compared to that in unstrained and compressively strained ones; the optical transition between the conduction and the uppermost valence band exhibiting the minimum transition energy was polarized parallel to the c axis, which is characteristic of the spin split-off valence band in unstrained crystal.
Fatigue resistance in lead zirconate titanate thin ferroelectric films: Effect of cerium doping and frequency dependence
Authors: Majumder S. B. , Mohapatra Y. N. , Agrawal D. C.
Published: July 2002

We demonstrate improvement in fatigue resistance and other ferroelectric properties through cerium doping in sol–gel derived lead zirconate titanate thin films. We have studied frequency dependence of fatigue behavior and show that the loss of polarization due to fatigue follows a universal scaling behavior with N/f2, where N is the number of switching cycles and f the frequency. The origin of the scaling is attributed to the drift of oxygen vacancies, which is the rate limiting process in the growth of the interface layer responsible for fatigue. Empirical fits for both undoped and cerium-doped samples show that switchable polarization follows stretched exponential decay with time or N/f. Cerium doping is shown to improve fatigue resistance by impeding the motion of oxygen vacancies.
Erbium-doped phosphate glass waveguide on silicon with 4.1 dB/cm gain at 1.535 μm
Authors: Yan Y. C. , Faber A. J. , de Waal H. , Kik P. G. , Polman A.
Published: July 2002

Erbium-doped multicomponent phosphate glass waveguides were deposited by rf sputtering techniques. The Er concentration was 5.3×1020 cm−3. By pumping the waveguide at 980 nm with a power of ∼21 mW, a net optical gain of 4.1 dB at 1.535 μm was achieved. This high gain per unit length at low pump power could be achieved because the Er–Er cooperative upconversion interactions in this heavily Er-doped phosphate glass are very weak [the upconversion coefficient is (2.0±0.5)×10−18 cm3/s], presumably due to the homogeneous distribution of Er in the glass and due to the high optical mode confinement in the waveguide which leads to high pump power density at low pump power.
High carrier mobility in polycrystalline thin film diamond
Authors: Looi Hui Jin , Jackman Richard B. , Foord John S.
Published: July 2002

Polycrystalline diamond films have been found to display p-type surface conductivity. No bulk impurity is added to the films; the p-type characteristics of the undoped diamond are thought to be due to a surface or near surface hydrogenated layer. Carrier concentrations within the range 1017–1019 cm−3 have been measured; control over the carrier concentration can be achieved by annealing the “as-grown” films in air. For a given annealing temperature a stable carrier concentration arises. The Hall carrier mobility has been explored and a value of >70 cm2/Vs has been measured for a film with a carrier concentration of ∼5×1017 cm−3, the highest reported for polycrystalline thin film diamond and equivalent to boron doped single crystal diamond.
Ion–ion plasmas and double layer formation in weakly collisional electronegative discharges
Authors: Kolobov V. I. , Economou D. J.
Published: July 2002

Plasmas of electronegative gases often separate into two distinct regions: an ion–ion core and an electron–ion periphery. Under certain conditions, a double layer may form at the boundary between the two regions. In weakly collisional three-component electronegative plasmas, formation of a double layer depends on the ratio of the electron to negative ion temperatures, and the ratio of the electron to positive ion densities.
Charge transfer in charge-coupled devices fabricated on AlGaN/GaN heterostructures
Authors: Chen Q. , Blasingame M. , Faber C.
Published: July 2002

The fabrication and operation characteristics of linear array charge-coupled devices on AlGaN/GaN heterostructures are reported. In transistor mode, a three-stage device behaved as a multiple-gated field effect transistor with a transconductance of 12.8 mS/mm. In shift register mode, charge packages can be injected at one side and detected at the other side with a delay corresponding to the number of transfer electrodes of the device. At a transfer frequency of 6 MHz, the devices exhibited an estimated charge transfer efficiency of 0.94.
Interdiffusion of In and Ga in InGaN quantum wells
Authors: McCluskey M. D. , Romano L. T. , Krusor B. S. , Johnson N. M. , Suski T. , Jun J.
Published: July 2002

Interdiffusion of In and Ga is observed in InGaN/GaN multiple quantum wells for annealing temperatures of 1300–1400 °C. Hydrostatic pressures of up to 15 kbar were applied to prevent surface decomposition. In as-grown material, x-ray diffraction spectra show InGaN diffraction peaks up to the fourth order. After annealing at 1400 °C for 15 min, only the zero-order peak is observed, as a result of compositional disordering of the quantum well superlattice. Transmission electron microscopy confirms that the superlattice is completely disordered after annealing at 1400 °C for 15 min.
Laser-machined layer-by-layer metallic photonic band-gap structures
Authors: Katsarakis N. , Chatzitheodoridis E. , Kiriakidis G. , Sigalas M. M. , Soukoulis C. M. , Leung W. Y. , Tuttle G.
Published: July 2002

Metallic photonic band-gap crystals operating in the microwave frequency range were fabricated by laser precision machining. They consist of stainless steel plates with a tetragonal lattice of holes and a lattice constant of 15 mm. Transmission measurements show that periodic crystals exhibit a cutoff frequency in the 8–18 GHz range, below which no propagation is allowed. The cutoff frequency can be easily tuned by varying the interlayer distance or the filling fraction of the metal. Combinations of plates with different hole diameters create defect modes with relatively sharp peaks, which are tunable. The experimental measurements are in good agreement with theoretical calculations.
Growth of Nd:potassium gadolinium tungstate thin-film waveguides by pulsed laser deposition
Authors: Atanasov P. A. , Tomov R. I. , Perriére J. , Eason R. W. , Vainos N. , Klini A. , Zherikhin A. , Millon E.
Published: July 2002

Thin Nd-doped potassium gadolinium tungstate [KGW or KGd(WO4)2] films are grown by pulsed laser deposition by ablation of a stoichiometric monocrystal target. Rutherford backscattering, x-ray diffraction, atomic force microscopy, and waveguide propagation analyses are performed. The as-grown films are optically active, as evidenced by the photoluminescence spectra centered at 1.068 μm. In some of the films, fine photoluminescence spectra between Stark levels are observed.
Area detector based photon correlation in the regime of short data batches: Data reduction for dynamic x-ray scattering
Authors: Lumma D. , Lurio L. B. , Mochrie S. G. J. , Sutton M.
Published: July 2002

A method for reducing time sequences of raw scattering images to intensity time-autocorrelation functions is presented. The procedure is based on the use of a charge coupled device (CCD) area detector, and optimized for operating in the regime of short data batches. Its application to x-ray photon correlation spectroscopy (XPCS) measurements is described in detail. Using a slow-scan CCD, we explain how to achieve data acquisition on a 30 ms or faster time scale, while simultaneously acquiring data from many coherence areas in parallel. The statistical uncertainties of the acquired XPCS data are quantified experimentally, and compared to the theoretically expected noise levels of the correlation functions.
Gauge factor of thick-film resistors: Outcomes of the variable-range-hopping model
Authors: Grimaldi C. , Ryser P. , Strässler S.
Published: July 2002

Despite a large amount of data and numerous theoretical proposals, the microscopic mechanism of transport in thick-film resistors remains unclear. However, recent low-temperature measurements point toward a possible variable-range-hopping mechanism of transport. Here, we examine how such a mechanism affects the gauge factor of thick-film resistors. We find that at sufficiently low temperatures T, for which the resistivity follows the Mott’s law R(T)∼exp(T0/T)1/4, the gauge factor (GF) is proportional to (T0/T)1/4. Moreover, the inclusion of Coulomb gap effects leads to GF∼(T0′/T)1/2 at lower temperatures. In addition, we study a simple model which generalizes the variable-range-hopping mechanism by taking into account the finite mean intergrain spacing. Our results suggest a possible experimental verification of the validity of the variable-range hopping in thick-film resistors.
Quantum point contacts fabricated by nanoimprint lithography
Authors: Martini Ingo , Eisert Dominik , Kamp Martin , Worschech Lukas , Forchel Alfred , Koeth Johannes
Published: July 2002

The potential of integrating nanoimprint lithography into electronic device fabrication is demonstrated by means of a quantum point contact (QPC). A Si-mold with a split-gate pattern is embossed into a thin polymer film located on top of a modulation-doped GaAs/AlGaAs heterostructure. The split-gates are fabricated by metal evaporation and lift-off. The gate tip separation ranges from 180 nm to 400 nm. Transport studies performed at a temperature of 4.2 K show conductance quantization with varying gate voltages.
On upper bounds for infinite Prandtl number convection with or without rotation
Authors: Doering Charles R. , Constantin Peter
Published: July 2002

Bounds for the bulk heat transport in Rayleigh–Benard convection for an infinite Prandtl number fluid are derived from the primitive equations. The enhancement of heat transport beyond the minimal conduction value (the Nusselt number Nu) is bounded in terms of the nondimensional temperature difference across the layer (the Rayleigh number Ra) according to Nu⩽cRa2/5, where c<1 is an absolute constant. This rigorous upper limit is uniform in the rotation rate when a Coriolis force, corresponding to the rotating convection problem, is included.