bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative Abundance, Distribution, and Diversity of Mosquitoes in District Peshawar, Charsadda, and Swabi
Authors: Azim Soneela , Nawab Sadia , Ali Naima
Published: February 2023

Aims: To date, there are 3601 named mosquito species recognized worldwide representing the diverse and medically important fly family Culicidae. In this study, after collection and identification of mosquitoes from the study area, their diversity, relative abundance (RA), and distribution (C) were evaluated for the prevention of mosquito-borne diseases.

Place and Duration of Study: Mosquitoes in their immature and adult stages were collected from their habitats in district Peshawar, Charsadda, and Swabi from September 2021 till April 2022.

Study Design: The immature samples were collected from various places such as pots, small water containers, bushy places under trees, and from the edges of some open drains. While the adult mosquitoes were collected during the same period by using the light trap and Pyrethrum spray methods for outdoor and indoor environment, respectively.

Methodology: 252 and 295 mosquitoes in their larval and pupal, and adult stages, respectively, were collected and brought to the laboratory for rearing and were observed on daily basis. All the adult specimens were preserved using silica gel in test tubes. The specimens were kept in entomological boxes after rearing and preservation for identification. Taxonomic identification of the adult mosquitoes was made using the key provided in the fauna of British India.

Results: The identification showed the presence of four species belonging to three genera: Culex quinquefasciatus; Aedes aegypti, Aedes albopictus; and Armigeres subalbatus. Culex quinquefasciatus was the most abundant specie found at all the study sites (C=100% and RA=44.24%), while Armigeres subalbatus was found to be an infrequent specie (C=25% and RA=20.66%). Several indices were also calculated to find out the diversity of the mosquitoes. The Shannon-Weiner index (H) for the month of April and December are 1.32 and 0.60, respectively, representing highest and lowest diversities among the study period.

Conclusion: The study found that Culex quinquefasciatus, Aedes aegypti, and Aedes albopictus are the most prevalent species in the study area and their presence increases the risk of mosquito-borne diseases such as West Nile virus, Filariasis, and Japanese Encephalitis transmission in the area. The study suggests further research to examine the diversity of mosquitoes more thoroughly to design effective vector control strategies and predict the risk of future disease outbreaks.
Construction Project Delay Factors of Public Universities in Ethiopia: A Structural Equation Modeling Approach
Authors: Yohannes Hailu Abenet , Mohammed Ismael , Alemu Dereje , Gesese Anley
Published: February 2023

Aims: This study aimed to identify causes of construction projects delay in Public Universities in Ethiopia.

Study Design: This was a cross-sectional survey using quantitative method.

Place and Duration of Study: Jigjiga, Haromaya, Dire Dewa and Kibrdhar universties between April and September 2022.

Methodology: This study identified project delay factors and modelled the Partial Least Square Structural Equation (PLS-SEM) model. a structured questionnaire used to collect data from contractors, consultants and clients. Data were analyzed using SmartPLS4 software.

Results: The findings show that Clients, Contractors, Consultants, Materials, and Labor related factors significantly affect delayed projects. Labour-related factors had the greatest impact on construction delay, while the external factor had an insignificant effect on project delay. The overall model had 73.1% explanatory power. These findings might support practitioners and decision-makers to focus on potential construction delay factors that might occur in their current or future projects.
Experiment Study: Auditor’s Going Concern Opinion Decision During Covid 19 Pandemic
Authors: Wardani Rr. Puruwita , Hartanto Susanna
Published: February 2023

This research is an experimental research that assesses the giving of going concern opinions conducted by auditors during the Covid 19 pandemic. To enhance the degree of confidence in the financial statements, a qualified external party (an auditor) is engaged to examine the financial statements. However, Auditors are increasingly being asked to provide assurance on non-financial information, both on a standalone basis or in conjunction with the audit of normal financial statements. Auditors shall perform a risk assessment in order for continuity of the going concernThe participants who participated and can be used in this study are members of IAPI in the East Java region as many as 40 auditor. Participants in this research have experiences in positions as senior auditors, supervisors, managers and partners. The results of this study are that auditors do not differentiate in auditing the functioning and non-functioning companies in the context of giving going-concern opinion decisions. Auditor considers financial information more than non-financial information in giving a going concern opinion because financial information is historical data that can be used to assess the company's current condition and to predict future financial conditions. Non-financial information is used as supporting information for going concern decision making.
Distribution and spatial autocorrelation of maternal mortality from preeclampsia and eclampsia in Brazil / Distribuição e autocorrelação espacial da mortalidade materna por pré-eclâmpsia e eclâmpsia no Brasil
Authors: Tavares Ana Maria Batista , Moroskoski Márcia , Cioffi Juliana Karyna Romanini , De Oliveira Rosana Rosseto
Published: February 2023

Objetivo: analisar a distribuição e autocorrelação espacial das taxas de mortalidade materna por pré-eclâmpsia e eclâmpsia no Brasil. Método: estudo ecológico, transversal, das taxas de mortalidade por pré-eclâmpsia e eclâmpsia de mulheres residentes no Brasil, em 2019. Foram calculadas as taxas, segundo estado e região de residência. A dependência espacial foi analisada pelo coeficiente de autocorrelação de Moran Global e Local. Resultados: foram analisados 278 óbitos (9,7/100 mil nascidos vivos). A autocorrelação espacial indicou um aglomerado alto-alto envolvendo o Norte e Nordeste e um único aglomerado baixo-baixo no Sul. Houve predomínio de óbitos em mulheres de 20 a 34 anos (60,79%), com oito anos ou mais de estudo (55,04%), sem companheiro (63,31%), ocorrência no ambiente hospitalar (92,81%), e de cor preta/parda (70,50%). Conclusão: as disparidades na distribuição das taxas de mortalidade materna mostram a necessidade de políticas públicas que considerem as especificidades de cada local para ações de prevenção.
An interleukin‐1β‐converting enzyme‐like protease is a common mediator of apoptosis in thymocytes
Authors: Fearnhead Howard O. , Dinsdale David , Cohen Gerald M.
Published: July 2002

Apoptosis was induced in thymocytes using diverse stimuli in order to identify events within a common apoptotic pathway. Benzyloxycarbonyl‐valinyl‐alaninyl‐aspartyl fluoromethyl ketone (Z‐VAD.FMK), an interleukin‐1β‐converting enzyme (ICE)‐like protease inhibitor, inhibited apoptosis assessed by flow cytometry, proteolysis of poly (ADP)‐ribose polymerase (PARP), an early biochemical marker of apoptosis, and cleavage of DNA to both large kilobase pair fragments.(30–50 and 200–300 kbp) and to nucleosomal fragments. Z‐VAD.FMK also blocked all the classical ultrastructural features of apoptosis including chromatin condensation to one pole of the nucleus, nucleolar disintegration and cytoplasmic vacuolation. These results suggest the involvement of an ICE‐like protease as a common mediator of apoptosis in thymocytes.
Adenosarcomas originating from sites other than uterine endometrium
Authors: Inoue M. , Fukuda H. , Tanizawa O.
Published: July 2002

We report three cases of adenosarcomas arising from extraendometrium of the uterus: one arising from the ovary, one from the paracolpium and one from the endocervix of the uterus. Microscopically, they consisted of an admixture of benign‐appearing epithelial and mesenchymal components with hypercellularity and minimal atypia. Two of the tumors were initially misdiagnosed as endometriosis and one was diagnosed as adenofibroma. One patient had several recurrences and died 7 years after the initial laparotomy and another patient had sarcomatous overgrowth which invaded the muscular tissues of the large intestine. Thus it appears that adenosarcoma occasionally shows grave clinical behavior, despite the benign or low‐grade appearance of its microscopic features. Problems of diagnosis and management of this tumor are discussed. An aggressive therapeutic approach including wide surgical excision is recommended even in questionable cases.
A plant defensive cystatin (soyacystatin) targets cathepsin L‐like digestive cysteine proteinases (DvCALs) in the larval midgut of western corn rootworm (Diabrotica virgifera virgifera)
Authors: Koiwa Hisashi , Shade Richard E. , Zhu-Salzman Keyan , D'Urzo Matilde Paino , Murdock Larry L. , Bressan Ray A. , Hasegawa Paul M.
Published: July 2002

Feeding bioassay results established that the soybean cysteine proteinase inhibitor N (soyacystatin N, scN) substantially inhibits growth and development of western corn rootworm (WCR), by attenuating digestive proteolysis [Zhao, Y. et al. (1996) Plant Physiol. 111, 1299–1306]. Recombinant scN was more inhibitory than the potent and broad specificity cysteine proteinase inhibitor E‐64. WCR digestive proteolytic activity was separated by mildly denaturing SDS–PAGE into two fractions and in‐gel assays confirmed that the proteinase activities of each were largely scN‐sensitive. Since binding affinity to the target proteinase [Koiwa, H. et al. (1998) Plant J. 14, 371–380] governs the effectiveness of scN as a proteinase inhibitor and an insecticide, five peptides (28–33 kDa) were isolated from WCR gut extracts by scN affinity chromatographic separation. Analysis of the N‐terminal sequence of these peptides revealed similarity to a cathepsin L‐like cysteine proteinase (DvCAL1, Diabrotica virgifera virgifera cathepsin L) encoded by a WCR cDNA. Our results indicate that cathepsin L orthologs are pivotal digestive proteinases of WCR larvae, and are targets of plant defensive cystatins (phytocystatins), like scN.
The presence of 4‐hydroxyphenylacetic acid in human saliva and the possibility of its nitration by salivary nitrite in the stomach
Authors: Takahama Umeo , Oniki Takayuki , Murata Hideaki
Published: July 2002

Human saliva contained 4‐hydroxyphenylacetic acid (HPA) (2–10 μM) and nitrite (60–300 μM). HPA was nitrated to 4‐hydroxy‐3‐nitrophenylacetic acid (NO2HPA) when HPA and sodium nitrite were mixed at pH 1.0. NO2HPA was also formed when saliva was incubated under acidic conditions. These results suggest that salivary HPA is nitrated to NO2HPA when saliva is swallowed into the stomach.
International Study of Asthma and Allergies in Childhood: Validation of the rhinitis symptom questionnaire and prevalence of rhinitis in schoolchildren in São Paulo, Brazil
Authors: Vanna Ana Tereza , Yamada Elza , Arruda Luisa Karla , Naspitz Charles Kirov , Solé Dirceu
Published: July 2002

Written questionnaires (WQ) have been widely used in epidemiologic studies. In order to yield comparable results, they must be validated after translation to another language. The International Study of Asthma and Allergies in Childhood (ISAAC) WQ has been previously validated by a comprehensive study, but its validation in Brazil has not been performed. Our objectives were to validate the rhinitis component of the ISAAC's self‐applicable WQ following its translation to Portuguese, and to determine the prevalence of rhinitis and related symptoms among Brazilian children living in the city of São Paulo. A group of 10 pediatricians and 10 pediatric allergists graded the questions from 0 to 2 and established a maximum score for each question. The WQ was answered by parents or guardians of children 6–7 years of age with rhinitis (R) (n = 27) and of control children of the same age without rhinitis (C) (n = 27). The WQ was also completed by adolescents 13–14 years of age with rhinitis (R) (n = 32) and without rhinitis (C) (n = 32). Half of these individuals answered the same WQ after 2–4 weeks, to ensure reproducibility. Cut‐off scores of 4 and 3 were identified for the 6–7‐ and 13–14‐year‐old groups, respectively, as scores predictive of rhinitis. The prevalence of rhinitis was 28.8% in the group of 3005 children 6–7 years of age and 31.7% in the group of 3008 children 13–14 years of age, respectively. Using the global cut‐off score, these prevalences were even higher, in the order of 34.7% and 40.7%, respectively. In conclusion, the rhinitis component of the ISAAC WQ was proven to be reproducible, adequate and able to discriminate children and adolescents with and without rhinitis, and revealed that the prevalence of rhinitis among Brazilian children living in the city of São Paulo was as high as the prevalence of rhinitis in other areas of the world.
Ascorbate up-regulates MLH1 (Mut L homologue-1) and p73: implications for the cellular response to DNA damage
Authors: CATANI M. Valeria , COSTANZO Antonio , SAVINI Isabella , LEVRERO Massimo , DE LAURENZI Vincenzo , WANG Jean Y.J. , MELINO Gerry , AVIGLIANO Luciana
Published: July 2002

We have found previously that ascorbic acid (vitamin C), as well as acting as a radical scavenger, may modulate the expression of several genes [i.e. fra-1, glutathione S-transferase Pi (GSTpi) and Mut L homologue-1 (MLH1)] in human keratinocytes. In the present paper, we demonstrate that MLH1, as well as its downstream target p73, can be positively modulated by this antioxidant vitamin, indeed, up-regulation of the two mRNAs was observed after just 2h, and increased further up to 16h of treatment. Modulation of MLH1 and p73 gene expression improves cellular susceptibility to apoptosis triggered by the DNA-damaging agent cisplatin. Indeed, in ascorbate-supplemented cells, increased cisplatin-induced apoptosis was seen, involving activation of the MLH1/c-Abl/p73 signalling cascade. Our results were further confirmed by studies performed on genetically defined mutants, i.e. mouse embryo fibroblasts derived from knock-out animals for c-Abl or p53, as well as human colon carcinoma cell lines deficient in MLH1. The increased sensitivity to cisplatin observed in ascorbate-loaded cells appeared to be dependent exclusively on MLH1 and c-Abl expression, and independent of p53. These data suggest a potential mechanism accounting for the anti-carcinogenic and anti-cancer activities of vitamin C.
Coordination chemistry of iron(III)–porphyrin–antibody complexes
Authors: de Lauzon Solange , Mansuy Daniel , Mahy Jean‐Pierre
Published: July 2002

An artificial peroxidase‐like hemoprotein has been obtained by associating a monoclonal antibody, 13G10, and its iron(III)–α,α,α,β‐meso‐tetrakis(ortho‐carboxyphenyl)porphyrin [Fe(ToCPP)] hapten. In this antibody, about two‐thirds of the porphyrin moiety is inserted in the binding site, its ortho‐COOH substituents being recognized by amino‐acids of the protein, and a carboxylic acid side chain of the protein acts as a general acid base catalyst in the heterolytic cleavage of the O–O bond of H2O2, but no amino‐acid residue is acting as an axial ligand of the iron.

We here show that the iron of 13G10–Fe(ToCPP) is able to bind, like that of free Fe(ToCPP), two small ligands such as CN–, but only one imidazole ligand, in contrast to to the iron(III) of␣Fe(ToCPP) that binds two. This phenomenon is general for a series of monosubstituted imidazoles, the 2‐ and 4‐alkyl‐substituted imidazoles being the best ligands, in agreement with the hydrophobic character of the antibody binding site. Complexes of antibody 13G10 with less hindered iron(III)–tetraarylporphyrins bearing only one [Fe(MoCPP)] or two meso‐[ortho‐carboxyphenyl] substituents [Fe(DoCPP)] also bind only one imidazole. Finally, peroxidase activity studies show that imidazole inhibits the peroxidase activity of 13G10–Fe(ToCPP) whereas it increases that of 13G10–Fe(DoCPP). This could be interpreted by the binding of the imidazole ligand on the iron atom which probably occurs in the case of 13G10–Fe(ToCPP) on the less hindered face of the porphyrin, close to the catalytic COOH residue, whereas in the case of 13G10–Fe(DoCPP) it can occur on the other face of the porphyrin. The 13G10–Fe(DoCPP)–imidazole complex thus constitutes a nice artificial peroxidase‐like hemoprotein, with the axial imidazole ligand of the iron mimicking the proximal histidine of peroxidases and a COOH side chain of the antibody acting as a general acid‐base catalyst like the distal histidine of peroxidases does.
Sip feed prescribing in primary care: an audit of current practice in Greater Glasgow Health Board, Glasgow, UK
Authors: McCombie L.
Published: July 2002

Background and aims: Prior to September 1995, prescribing of sip feeds had been increasing at a higher rate than any other part of the drugs bill. An increase in requests for information on the use of these products led the Prescribing Advisers Department to seek funding for a 1‐year project to document current practice in this area and produce guidelines for GPs, their practice nurses and district nurses.

Methods: Questionnaires were completed by GPs (n=52), district nurses (n=94) and dietetic departments (n= 8) concerning current practice. In addition, 90 patients were interviwed and in all but one instance case notes were also consulted.

Results: The most significant findings were that Primary Care staff see palliative care as one of the main areas of usage of these products and that 40% of patients were found to have some degree of undernutrition. The majority of patients interviewed were elderly and 10% of patients interviewed were in nursing homes. A significant proportion of patients interviewed had commenced sip feeds whilst in hospital. The majority of patients reported receiving no advice on diet with only one GP making written dietary advice available to patients. Finally, district nurses view company representatives as the most useful source of information on these products.

Conclusions: In response to these findings, the project included the development of a standard communication form from secondary to primary care, dietary information resource development, development of guidelines on oral nutrition support in Primary Care and GP and district nurse training
Redox enzymes in the plant plasma membrane and their possible roles
Authors: Bérczi A. , Møller I. M.
Published: July 2002

Purified plasma membrane (PM) vesicles from higher plants contain redox proteins with low‐molecular‐mass prosthetic groups such as flavins (both FMN and FAD), hemes, metals (Cu, Fe and Mn), thiol groups and possibly naphthoquinone (vitamin K1), all of which are likely to participate in redox processes. A few enzymes have already been identified: Monodehydroascorbate reductase (EC 1.6.5.4) is firmly bound to the cytosolic surface of the PM where it might be involved in keeping both cytosolic and, together with a b‐type cytochrome, apoplastic ascorbate reduced. A malate dehydrogenase (EC 1.1.1.37) is localized on the inner side of the PM. Several NAD(P)H‐quinone oxidoreductases have been purified from the cytocolic surface of the PM, but their function is still unknown. Different forms of nitrate reductase (EC 1.6.6.1–3) are found attached to, as well as anchored in, the PM where they may act as a nitrate sensor and/or contribute to blue‐light perception, although both functions are speculative. Ferric‐chelate‐reducing enzymes (EC 1.6.99.13) are localized and partially characterized on the inner surface of the PM but they may participate only in the reduction of ferric‐chelates in the cytosol. Very recently a ferric‐chelate‐reducing enzyme containing binding sites for FAD, NADPH and hemes has been identified and suggested to be a trans‐PM protein. This enzyme is involved in the reduction of apoplastic iron prior to uptake of Fe2+ and is induced by iron deficiency. The presence of an NADPH oxidase, similar to the so‐called respiratory burst oxidase in mammals, is still an open question. An auxin‐stimulated and cyanide‐insensitive NADH oxidase (possibly a protein disulphide reductase) has been characterized but its identity is still awaiting independent confirmation. Finally, the only trans‐PM redox protein which has been partially purified from plant PM so far is a high‐potential and ascorbate‐reducible b‐type cytochrome. In co‐operation with vitamin K1 and an NAD(P)H‐quinone oxidoreductase, it may participate in trans‐PM electron transport.
Interaction of the DNA‐binding antitumor antibiotics, chromomycin and mithramycin with erythroid spectrin
Authors: Majee Sangita , Dasgupta Dipak , Chakrabarti Abhijit
Published: July 2002

The aureolic acid group of antitumor antibiotics, chromomycin A3 and mithramycin, are well established as transcription inhibitors, which bind reversibly to DNA at and above physiological pH, in the presence of divalent metal ions such as Mg2+. As part of our broad objective to elucidate their intracellular mode of action, other than association with DNA, we studied their interactions with the erythrocyte cytoskeletal protein, spectrin, in the absence and presence of magnesium. Different spectroscopic studies, such as absorbance, fluorescence and CD, have shown that both free chromomycin and mithramycin and their Mg2+ complexes bind to spectrin with an affinity higher than that reported for DNA. The affinity constants for the association of chromomycin and mithramycin (or their Mg2+ complexes) with spectrin are comparable with those for the association of spectrin with other cytoskeletal proteins, for example F‐actin, ankyrin, protein 4.1, etc. The nature of the binding of the two antibiotics to spectrin is different. The mode of binding of the antibiotics with spectrin also changes in the presence of Mg2+. The interaction leads to a change in the tertiary structure of the protein. The relevance of the results to our understanding of the mode of action of the antibiotics is discussed.
The relaxation effects of ginseng saponin in rabbit corporal smooth muscle: is it a nitric oxide donor?
Authors: Kim  , Woo  , Lee  , Kim
Published: July 2002

Objective

 To determine whether crude extracts of ginseng saponin (GCS), containing the active ingredients from Panax ginseng and used as an aphrodisiac in oriental countries, relax corpus cavernosal smooth muscle in the rabbit.

Materials and methods

 Corpus cavernosal strips were prepared from rabbit penises. Isometric tension changes, recorded with a pressure transducer, in response to various drugs and electrical stimulation were assessed in an organ chamber, after active muscle tone had been induced by 10 μmol/L phenylephrine.

Results

 GCS (0.2–8.0 mg) relaxed the smooth muscle of rabbit corpus cavernosum (SMRCC) pre‐contracted with phenylephrine in a dose‐dependent manner. GCS at 0.75 mg significantly enhanced the relaxation of SMRCC induced by electrical field stimulation. The relaxation induced by 0.2–8.0 mg GCS was significantly attenuated by atropine (1 μmol/L), methylene blue (100 μmol/L) and N‐omega‐nitro‐L‐arginine methyl ester (L‐NAME, 10 μmol/L). However, there was no significant difference in the attenuation of GCS‐induced relaxation of SMRCC by adding vasoactive intestinal peptide antagonists or indomethacin. In addition, the decreasing rate of GCS‐induced relaxation of SMRCC by methylene blue and L‐NAME was greater than that by atropine. l‐arginine (10 mmol/L) reversed the inhibitory effect induced by L‐NAME (1 mmol/L) on the attenuation of GCS‐induced relaxation.

Conclusions

 These data suggest that GCS, as a nitric oxide donor, induces the relaxation of SMRCC through the l‐arginine/nitric oxide pathway. For the clinical application of ginseng saponin, further studies are required to clarify the active subfraction(s) of GCS.
Screening for diabetes mellitus – a two‐step approach in individuals with impaired fasting glucose improves detection of those at risk of complications
Authors: Tai E. S. , Lim S. C. , Tan B. Y. , Chew S. K. , Heng D. , Tan C. E.
Published: July 2002

SUMMARY

Aims  To compare the new American Diabetes Association (ADA) fasting plasma glucose (FPG) criteria to the 1985 World Health Organization (WHO) 2‐h post glucose (2hPG) criteria when used for screening of those with no prior history of diabetes mellitus.

Methods  The study included 3407 subjects without a history of diabetes in whom both FPG and 2hPG were available from the 1992 Singapore National Health Survey. The agreement (κ) between FPG and 2hPG for the diagnosis of DM was assessed. The optimal cut‐off of FPG for the detection of individuals with 2hPG ≥ 11.1 mmol/l was determined by receiver–operating characteristics analysis.

Results  The prevalence of diabetes diagnosed by FPG alone was 7.3% compared to 8.4% diagnosed by 2hPG. The prevalence of impaired fasting glucose was 8.0%. FPG and 2hPG showed moderate agreement(κ = 0.646, 95% confidence interval 0.584–0.708). Age, ethnic group and obesity did not affect the degree of agreement. Of those with 2hPG ≥ 11.1 mmol/l, 40.8% had FPG in the non‐diabetic range while 24.8% of those with FG ≥ 7.0 mmol/l had 2hPG in the non‐diabetic range. The optimal FPG for the detection of 2hPG ≥ 11.1 mmol/l was 6.1 mmol/l. Oral glucose tolerance tests (OGTT) in those with 6.0 mmol/ < FPG < 7.0 mmol/l resulted in the diagnosis of diabetes in 90.7% of individuals at risk of microvascular complications.

Conclusions  FPG provides a simple screening test for diabetes, which shows moderate agreement with the 2hPG. A two‐step strategy of OGTT in those with impaired fasting glucose improves the detection of at‐risk individuals. However, diabetes should not be diagnosed on a single test. The test should be repeated on another day if an individual tests positive for diabetes.
Photosynthesis, Soluble and Structural Carbon Compounds in Two Mediterranean Oak Species (Quercus pubescens and Q. ilex) after Lifetime Growth at Naturally Elevated CO2 Concentrations
Authors: Blaschke L. , Schulte M. , Raschi A. , Slee N. , Rennenberg H. , Polle A.
Published: July 2002

Abstract: To study physiological responses of mature forest trees to elevated CO2 after lifetime growth under elevated atmospheric CO2 concentrations (pCO2), photosynthesis, Rubisco content, foliar concentrations of soluble sugars and starch, sugar concentrations in transport tissues (phloem and xylem), structural biomass, and lignin in leaves and branches were investigated in 30‐ to 50‐year‐old Quercus pubescens and Q. ilex trees grown at two naturally elevated CO2 springs in Italy. Ribulose‐1,5‐bisphosphate carboxylase/oxygenase content was decreased in Q. pubescens grown under elevated CO2 concentrations, but not in Q. ilex. Photosynthesis was consistently higher in Q. pubescens grown at elevated CO2 as compared with “control” sites, whereas the response in Q. ilex was less pronounced. Stomatal conductance was lower in both species leading to decreased transpiration and increased instantaneous water use efficiency in Q. pubescens. Overall mean sugar + starch concentrations of the leaves were not affected by elevated pCO2, but phloem exudates contained higher concentrations of soluble sugars. This finding suggests increased transport to sinks. Qualitative changes in major carbon‐bearing compounds, such as structural biomass and lignins, were only found in bark but not in other tissues. These results support the concept that the maintenance of increased rates of photosynthesis after long‐term acclimation to elevated pCO2 provides a means of optimization of water relations under arid climatic conditions but does not cause an increase in aboveground carbon sequestration per unit of tissue in Mediterranean oak species.
Strained-layer Ga1−xInxAs/InP avalanche photodetectors
Authors: Gershoni D. , Temkin H. , Panish M. B.
Published: July 2002

We have investigated the electrical and optical properties of avalanche photodiodes with the absorption region formed by Ga1−x InxAs/InP strained-layer superlattices. High quality structures with the In concentration x as high as 1 have been grown by gas source molecular beam epitaxy. We have extended the photodiode response to approximately 2 μm and obtained avalanche gain of 16. The spectral range accessible with these strained-layer devices is carefully modeled.
High performance tunable 1.5 μm InGaAs/InGaAsP multiple quantum well distributed Bragg reflector lasers
Authors: Koch T. L. , Koren U. , Miller B. I.
Published: July 2002

We describe the structure and performance of tunable four-quantum-well InGaAs/InGaAsP distributed Bragg reflector lasers. We observe total tuning range as large as 94 Å, differential efficiency of 32%/front facet, thresholds of 17 mA, low-chirp high-speed digital operation, and linewidths as low as 5.75 MHz at only 2 mW output.
Column III and V ordering in InGaAsP and GaAsP grown on GaAs by metalorganic chemical vapor deposition
Authors: Plano W. E. , Nam D. W. , Major J. S. , Hsieh K. C. , Holonyak N.
Published: July 2002

Data are presented showing that GaAs1−y Py grown on GaAs by metalorganic chemical vapor deposition (MOCVD) at relatively low temperature (∼640 °C) exhibits ordering on the column V sublattice. These data, with electron diffraction data and impurity-induced layer disordering data, show that column III site and column V site ordering is possible for the quaternary InGaAsP grown on GaAs by MOCVD at relatively low temperature (∼640 °C). Ordered InGaAsP grown on GaAs shifts in photoluminescence wavelength ∼130 meV higher in energy with disordering by annealing or by impurity-induced intermixing.
Power spectrum of frequency noise of semiconductor lasers with optical feedback from a high-finesse resonator
Authors: Li H. , Abraham N. B.
Published: July 2002

The power spectrum of frequency noise of a semiconductor laser with optical feedback from a high-finesse resonator is calculated using a differential-difference equation. The results are compared with measurements. The feedback reduces the frequency noise at low Fourier frequencies, while enhancing the oscillations near the relaxation oscillation frequency, eventually driving the system unstable. The results show a simple way to choose the parameters of the high-finesse cavity to minimize the frequency noise without causing instabilities.
Telegraph-like noise in Y-Ba-Cu oxide thin-film dc SQUID’s
Authors: Matsuda M. , Kuriki S.
Published: July 2002

We have observed a telegraph-like noise in dc superconducting quantum interference devices (SQUID’s) made of low-temperature synthesized superconducting Y-Ba-Cu oxide thin films. The voltage of the SQUID jumps among two to four discrete levels randomly with time, and exhibits a Lorentzian type frequency dependence in the power spectrum. Periodic modulations of the voltage with magnetic flux are observed in a SQUID having narrow bridges of submicrometer width. The flux noise of the SQUID is dominated by the telegraph-like noise at low frequencies.
Mode locking and Q switching of a diode laser pumped neodymium-doped yttrium lithium fluoride laser
Authors: Maker G. T. , Ferguson A. I.
Published: July 2002

We have developed a mode-locked, diode pumped, neodymium-doped yttrium lithium fluoride (Nd:YLF) laser operating at 1.053 μm. The laser produces pulses of 18 ps duration at an average power level of 12 mW. When Q switched the duration of the pulse train was 140 ns, giving rise to peak powers of 15 kW.
Metalorganic chemical vapor deposition of high-purity GaAs using tertiarybutylarsine
Authors: Haacke G. , Watkins S. P. , Burkhard H.
Published: July 2002

The growth of high-purity gallium arsenide using tertiarybutylarsine (TBA) and trimethylgallium is reported. The availability of high-purity TBA has permitted the growth of material with liquid-nitrogen mobilities of up to 80 000 cm2/V s, the highest value yet reported for growth with any alkyl arsine. The residual donor species have been identified by magnetophotoluminescence.
Low-loss multiple quantum well GaInAs/InP optical waveguides
Authors: Deri R. J. , Kapon E. , Bhat R. , Seto M. , Kash K.
Published: July 2002

Propagation losses as low as 0.24±0.06 dB/cm are demonstrated for single-mode, GaInAs/InP multiple quantum well rib waveguides at 1.52 μm wavelength. We show that reproducibly low losses (≤0.6 dB/cm for rib widths ≥3 μm) can be maintained over a large chip area (9.4×5 mm2). Origins of the loss are discussed.
Effect of a GaAs buffer layer grown at low substrate temperatures on a high-electron-mobility modulation-doped two-dimensional electron gas
Authors: Melloch M. R. , Miller D. C. , Das B.
Published: July 2002

Sidegating in GaAs integrated circuits can be eliminated in molecular beam epitaxially grown structure with the incorporation of a GaAs buffer layer grown at low substrate temperatures (200–300 °C). We have grown two films which were identical except one had the low-temperature buffer layer included in the film structure. The films were modulation-doped heterojunctions designed to produce a high-mobility two-dimensional electron gas. The electrical characteristics of the two-dimensional electron gas were identical for the two samples. No deleterious effect on the mobility or carrier density was observed with the incorporation of the low-temperature buffer layer. At 4.2 K both films exhibited carrier densities of 4×1011 cm−2 and mobilities of (1.4–1.7)×106 cm2/V s in the dark. After a brief illumination at 4.2 K, the samples exhibited carrier densities of 5×1011 cm−2 and mobilities of (1.6–2.0)×106 cm2/V s. These electron mobilities are comparable to the highest electron mobilities ever obtained at these electron densities.
Nonradiative energy transfer in Nd:YAG—evidence for the correlated placement of ions
Authors: Rotman Stanley R.
Published: July 2002

Analysis of data from Nd:YAG indicates a substantial experimental divergence from the standard theoretical results predicted for nonradiative energy transfer. A new model for correlated ion placement in the crystal is shown to completely explain the discrepancy.
Fabrication of integrated optical structures in polydiacetylene films by irreversible photoinduced bleaching
Authors: Rochford K. B. , Zanoni R. , Gong Q. , Stegeman G. I.
Published: July 2002

Spin-coated and solution-cast films of poly[5,7-dodecadiyn-1,12-diol-bis(n-butoxycarbonyl-methyl-urethane)], or briefly, poly-4BCMU, irreversibly bleach when irradiated by light tuned within the absorption band of the polymer sample. Characteristic bleaching times have been measured at several wavelengths. The refractive index of poly-4BCMU has been measured at 1.064 μm for various photobleaching energies. Refractive index changes as large as −0.08 have been measured, and the decrease in refractive index has been used to define waveguide channels and gratings.
Transverse modes, waveguide dispersion, and 30 ps recovery in submicron GaAs/AlAs microresonators
Authors: Jewell J. L. , McCall S. L. , Scherer A. , Houh H. H. , Whitaker N. A. , Gossard A. C. , English J. H.
Published: July 2002

We have studied room-temperature optical gating of ∼5 ps pulses in GaAs/AlAs microresonators with diameters ranging from <0.5 μm to 1.5 μm by using a high-refractive-index lens system having a numerical aperture of 1.3. The larger devices exhibited well-defined transverse modes, which caused decreased modulation of the probe beam. Waveguide dispersion, present in all the devices, showed fair agreement with calculations. The smallest diameter devices (<0.5 μm) show high modulation, fully recover in <30 ps, and have their peak transmission wavelengths shifted by >500 Å compared to a large ∼10 μm nearby region.
Noise in vacuum tunneling: Application for a novel scanning microscope
Authors: Möller R. , Esslinger A. , Koslowski B.
Published: July 2002

The noise in the tunneling current of a scanning tunneling microscope (STM) has been investigated. At gap voltages above a few mV the current noise shows a 1/f spectral distribution over a range of 1 Hz to 100 kHz. However, at zero bias white noise scaling like thermal noise for the equivalent gap resistance is found. Due to its exponential distance dependence, this noise at zero bias can be used to adjust the tip-to-sample distance with an accuracy similar to the conventional STM method. The performance of a scanning microscope based on this principle is demonstrated.
Effects of arsenic concentration on the formation of dislocation loops near the projected ion range in high-dose As+-implanted (001) Si
Authors: Hsu S. N. , Chen L. J.
Published: July 2002

The formation of a two-layer structure and the inhibition of the formation of dislocation loops near the projected ion range (Rp ) have been observed by cross-sectional transmission electron microscopy in 80 keV, 1×1016 and 2×1016/cm2 As+-implanted (001) Si, respectively. The correlations among the arsenic concentration, electrical inactivation of impurity, suppression of the formation of interstitial loops near Rp, and retardation of the epitaxial regrowth rate provide significant insight into the point-defect migration and agglomeration during solid phase epitaxial regrowth of implantation amorphous silicon.
Glass-derived superconducting ceramics with zero resistance at 107 K in the Bi1.5Pb0.5Sr2Ca2Cu3Ox system
Authors: Bansal Narottam P. , Farrell D. E.
Published: July 2002

A melt of composition Bi1.5Pb0.5Sr2Ca2Cu3Ox was fast quenched to form a glass. This was subsequently air annealed and the influence of annealing time and temperature on the formation of various crystalline phases was investigated. X-ray powder diffraction indicated that none of the resulting samples were single phase. However, for an annealing temperature of 840 °C, the volume fraction of the high Tc phase (isostructural with Bi2 Sr2 Ca2 Cu3O10 ) increased with annealing time. A specimen annealed at this temperature for 243 h followed by slow cooling showed a sharp transition [ΔTc (10–90%) ∼2 K] and Tc (R=0)=107.2 K. To our knowledge, this is the highest Tc yet reported for any superconductor prepared via the glass route.
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u processing of textured superconducting thin film of Bi(-Pb)-Ca-Sr-Cu-O by excimer laser ablation
Authors: Kumar Ashok , Ganapathi L. , Narayan J.
Published: July 2002

We have prepared highly oriented bismuth cuprate thin films (c-axis textured) on yttria-stabilized zirconia (100) YS-ZrO2 substrates at 650 °C by pulsed excimer laser ablation in a 200 mTorr oxygen ambient. The films were annealed in oxygen and nitrogen atmospheres to study the effect on zero-resistance transition temperature (Tc0). Thin films deposited at 650 °C exhibited a Tc0 of 68 K with onset at 110 K. Post-annealing for 1 h at 400 °C in oxygen improved the Tc0 to 82 K, while the onset remained the same. X-ray diffraction, scanning electron microscopy, and Rutherford backscattering channeling studies were performed on these films for correlations between crystal structure, microstructure, and superconducting properties. X-ray diffraction patterns indicated a 2212 type phase with a=5.39 Å and c=30.76 Å; preferential orientation of the c axis perpendicular to the substrate was observed. The lattice parameters and x-ray diffraction patterns were found to be invariant with annealing treatments that improved Tc0 from 68 to 82 K.
Effects of hydrogen on the photochemical unpinning of gallium arsenide
Authors: Ives N. A. , Stupian G. W. , Leung M. S.
Published: July 2002

Recent studies have shown that, after a preparative photowashing step, water, oxygen, and light must all be present in order to produce Fermi level unpinning of gallium arsenide surfaces. The in situ photoluminescence (PL) investigations in an optical flow cell reported here confirm this finding and show that the unpinning and subsequent repinning processes speed up with an increase in oxygen concentration in the water during photoluminescence measurements. When the water is saturated with hydrogen the surface unpins, although more slowly than if the water were saturated with oxygen, air, or nitrogen. In addition the surface remains unpinned for longer periods. The PL transient response data suggest that hydrogen is an active participant in surface photochemical reactions. A conceptual model is advanced that is consistent with the experimental data on pinning/unpinning processes on the GaAs surface.
Si/SiO2 etch properties using CF4 and CHF3 in radio frequency cylindrical magnetron discharges
Authors: Yeom Geun Young , Kushner Mark J.
Published: July 2002

Si/SiO2 etch properties have been studied in CF4 and CHF3 cylindrical magnetron rf discharges as a function of magnetic field strength. As the magnetic field strength increases from 0 to 250 G, radical densities continuously increase and dc bias voltages exponentially decrease. The maximum etch rates of Si and SiO2, however, occur at an intermediate value of magnetic field strength which corresponds to the self-bias voltage being between 25 and 50 V. Using magnetic field strengths near the maximum etch rate, we obtained vertical features having <2000 Å widths and trenches deeper than 2 μm. Etch rates exceeding 2500 Å/min were obtained in a CF4 plasma, with little or no radiation damage, and with minimum contamination of the surface.
Spatial resolution of the capacitance-voltage profiling technique on semiconductors with quantum confinement
Authors: Schubert E. F. , Kopf R. F. , Kuo J. M. , Luftman H. S. , Garbinski P. A.
Published: July 2002

The spatial resolution of the capacitance-voltage profiling technique on semiconductors with one-dimensional quantum confinement is shown to be given by the spatial extent of the wave function. The Debye length limitation does not apply. Capacitance-voltage profiles on δ-doped GaAs of density 4–4.5×1012 cm−2 exhibit widths of 20 and 48 Å for p- and n-type impurities, respectively. The profiles agree with the theoretical resolution function and with Be and Si profiles measured by secondary-ion mass spectroscopy. It is further shown that the saturation of the free-carrier density of highly Si δ-doped GaAs grown by molecular beam epitaxy is due to inactive Si impurities
Near-diffraction-limited angle-switchable output beam from a broad-area diode laser with an intracavity spatial phase controller
Authors: Hohimer J. P. , Craft D. C. , Vawter G. A. , Myers D. R.
Published: July 2002

The production of a near-diffraction-limited single-lobed angle-switchable output beam from a broad-area diode laser with an intracavity spatial phase controller is demonstrated. This 100-μm-wide broad-area laser produces a 0.8° full width at half maximum output beam at single-facet pulsed powers of ≳300 mW. The spatial phase controller operates in two distinct modes (thermal and gain), providing beam scanning over 1.4° and beam switching of 8°. The phase controller also permits a dynamic study of the effect of wavefront tilt on device coupling and phasing.
Novel photoacoustic spectroscopy of semiconductor thin films by a transparent transducer: Pyroelectric and piezoelectric effects
Authors: Kanemitsu Yoshihiko , Nabeta Hiroyuki
Published: July 2002

We have studied the generation mechanism of photoacoustic (PA) signals in semiconductor thin films by means of a transparent LiNbO3 transducer both experimentally and theoretically. In the transparent transducer method, the PA signal was detected at the light-irradiated surface of the samples. The PA signal of the thin film directly attached to the transducer is mainly due to the pyroelectric effect, and the PA signal of the underlain substrate is the piezoelectric signal caused by sample bending. These results show that this method becomes a powerful tool for measuring optical and thermal properties of thin films on the substrate nondestructively.
Direct observation of ions in laser plume onto the substrate
Authors: Izumi H. , Ohata K. , Sawada T. , Morishita T. , Tanaka S.
Published: July 2002

Direct observation of ions in the laser plume of YBa2Cu3O7−δ was carried out by time-of-flight mass spectroscopy. The direct observation of the species impinging onto the substrate is very important in order to clarify the kinetics of the film formation, so ion sampling was done through the orifice set at the position of the substrate. Thus the results indicate directly the species of ions incident onto the substrate during laser deposition. The analysis of the ion energies was also carried out. Atomic, monoxide, and cluster ions were observed in the laser plume and their energies were determined to be around 200, several tens and a few eV, respectively.
Fast escape of photocreated carriers out of shallow quantum wells
Authors: Feldmann J. , Goossen K. W. , Miller D. A. B. , Fox A. M. , Cunningham J. E. , Jan W. Y.
Published: July 2002

We report that at room temperature the field-induced escape of photogenerated carriers out of shallow GaAs/AlxGa1−xAs multiple quantum wells is as fast as for pure GaAs of the same thickness, if the value of x does not exceed 0.04. Our experimental findings can be explained by assuming that carriers are efficiently scattered into the unconfined barrier states by absorption of a LO phonon, as long as the effective barrier height is less than the LO-phonon energy. The application of shallow quantum wells with x≤0.04 in self-electro-optic effect devices, providing not only strong excitonic electroabsorption but also fast sweep-out times at small biases, should lead to shorter switching times.
High detectivity InGaAs base infrared hot-electron transistor
Authors: Choi K. K. , Fotiadis L. , Taysing-Lara M. , Chang W. , Iafrate G. J.
Published: July 2002

An infrared hot-electron transistor with a thin (300 Å)InGaAs base layer is constructed. By adopting a thin base material with a large Γ-L valley separation, the photocurrent transfer ratio is improved by a factor of four in comparison with the GaAs base transistor. As a result, the detectivity of the transistor is increased to 1.4×1010 cm√Hz/W at 77 K with a cutoff wavelength of 9.5 μm, two times as large as the companion state-of-the-art GaAs quantum well photoconductor. Combined with the lower dark current, the voltage responsivity and the noise equivalent temperature difference of a detector array can be improved by more than an order of magnitude.
Study of the microstructure of low energy (70 keV) oxygen implanted silicon
Authors: Li Y. , Kilner J. A. , Hemment P. L. F. , Robinson A. K. , Zhang J. P. , Reeson K. J. , Marsh C. D. , Booker G. R.
Published: July 2002

Device grade (100) single crystal silicon wafers have been implanted with 70 keV oxygen ions over a dose range from 3.3×1017 /cm2 to 10×1017/cm2 at a temperature of 680 °C. The wafers were subsequently annealed at 1320 °C for 6 h. Transmission electron microscopy and ion channeling studies show that both the as-implanted microstructure and the damage distribution play an important role in determining the final microstructure of the annealed wafer. As the dose increases so does both the values of χmin for both as-implanted and annealed wafers, and the threading dislocation density in the silicon overlayer of the annealed wafers. For the wafer implanted with 70 keV oxygen ions at the lowest dose (3.3×1017/cm2), the threading dislocation density in the silicon overlayer after annealing was less than 105/cm2.
Monolithic 77 K dc SQUID magnetometer
Authors: Lee L. P. , Char K. , Colclough M. S. , Zaharchuk G.
Published: July 2002

We report the first fabrication of a monolithic dc SQUID magnetometer that operates above 77 K. We have used bi-epitaxial grain boundary Josephson junctions in YBa2Cu3O7 (YBCO) to produce the SQUID itself while the flux transformer consists of heteroepitaxial layers of YBCO/SrTiO3/LaAlO3/SrTiO3/YBCO. In the circuit fabricated, the SQUID is built on top of the epitaxial layers of the flux transformer. We have used dry etching, ion-beam cleaning, and photolithographic processing to pattern all the layers. Via contacts and step coverage of the epitaxial wire layers have been achieved without significant degradation of the superconducting properties of any of the three YBCO layers. The magnetometer enhances the magnetic field sensitivity of the bare SQUID by a factor of 127, giving an effective area, dΦ/dB, of 1.9 mm2.