bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced discrimination between signals of danger and safety but not overgeneralization is linked to exposure to childhood adversity in healthy adults
Authors: Klingelhöfer-Jens Maren , Hutterer Katharina , Schiele Miriam A , Leehr Elisabeth J , Schümann Dirk , Rosenkranz Karoline , Böhnlein Joscha , Repple Jonathan , Deckert Jürgen , Domschke Katharina , Dannlowski Udo , Lueken Ulrike , Reif Andreas , Romanos Marcel , Zwanzger Peter , Pauli Paul , Gamer Matthias , Lonsdorf Tina B
Published: February 2025

Childhood adversity is a strong predictor of developing psychopathological conditions. Multiple theories on the mechanisms underlying this association have been suggested which, however, differ in the operationalization of ‘exposure.’ Altered (threat) learning mechanisms represent central mechanisms by which environmental inputs shape emotional and cognitive processes and ultimately behavior. 1402 healthy participants underwent a fear conditioning paradigm (acquisition training, generalization), while acquiring skin conductance responses (SCRs) and ratings (arousal, valence, and contingency). Childhood adversity was operationalized as (1) dichotomization, and following (2) the specificity model, (3) the cumulative risk model, and (4) the dimensional model. Individuals exposed to childhood adversity showed blunted physiological reactivity in SCRs, but not ratings, and reduced CS+/CS- discrimination during both phases, mainly driven by attenuated CS+ responding. The latter was evident across different operationalizations of ‘exposure’ following the different theories. None of the theories tested showed clear explanatory superiority. Notably, a remarkably different pattern of increased responding to the CS- is reported in the literature for anxiety patients, suggesting that individuals exposed to childhood adversity may represent a specific sub-sample. We highlight that theories linking childhood adversity to (vulnerability to) psychopathology need refinement.
AI detectors are poor western blot classifiers: a study of accuracy and predictive values
Authors: Gosselin Romain-Daniel
Published: February 2025

The recent rise of generative artificial intelligence (AI) capable of creating scientific images presents a challenge in the fight against academic fraud. This study evaluates the efficacy of three free web-based AI detectors in identifying AI-generated images of western blots, which is a very common technique in biology. We tested these detectors on AI-generated western blot images (n = 48, created using ChatGPT 4) and on authentic western blots (n = 48, from articles published before the rise of generative AI). Each detector returned a very different sensitivity (Is It AI?: 0.9583; Hive Moderation: 0.1875; and Illuminarty: 0.7083) and specificity (Is It AI?: 0.5417; Hive Moderation: 0.8750; and Illuminarty: 0.4167), and the predicted positive predictive value (PPV) for each was low. This suggests significant challenges in confidently determining image authenticity based solely on the current free AI detectors. Reducing the size of western blots reduced the sensitivity, increased the specificity, and did not markedly affect the accuracy of the three detectors, and only slightly improved the PPV of one detector (Is It AI?). These findings highlight the risks of relying on generic, freely available detectors that lack sufficient reliability, and demonstrate the urgent need for more robust detectors that are specifically trained on scientific contents such as western blot images.
Hydroxycinnamoyl-coenzyme A: tetrahydroxyhexanedioate hydroxycinnamoyl transferase (HHHT) from Phaseolus vulgaris L.: phylogeny, expression pattern, kinetic parameters, and active site analysis
Authors: Fanelli Amanda , Stonoha-Arther Christina , Sullivan Michael L.
Published: February 2025

BAHD acyl-coenzyme A (CoA) transferases comprise a large family of enzymes in plants which transfer an acyl group from a CoA thioester to hydroxyl or amine groups to form esters or amides, respectively. Clade Vb of this family primarily utilizes hydroxycinnamoyl-CoA as the acyl donor. These enzymes are involved in biosynthesis of diverse specialized metabolites with functions such as structure (e.g., lignin formation) and biotic/abiotic stress mitigation. The diversity of these enzymes has arisen from both divergent and convergent evolution, making it difficult to predict substrate specificity or enzyme function based on homology, and relatively few BAHD transferases have been characterized biochemically with respect to substrate specificity. We previously identified a hydroxycinnamoyl-CoA: tetrahydroxyhexanedioate hydroxycinnamoyl transferase (HHHT) from common bean capable of transferring hydroxycinnamic acids to mucic or saccharic acid to form the corresponding esters. Here, to better understand the structure/function relationships of this enzyme, we have further characterized it with respect to expression pattern, kinetic parameters, and predicted three-dimensional (3-D) structure and active site interactions with acceptor substrates. The hhht gene was expressed predominantly in leaves and to a lesser extent flowers and shoots. KM values did not vary greatly among donor or among acceptor substrates (generally less than two-fold), while kcat values were consistently higher for saccharic acid as substrate compared to mucic acid, leading to higher catalytic efficiency (as kcat/KM) for saccharic acid. Both acceptors had similar binding poses when docked into the active site, and the proximity of multiple hydroxyl groups to the catalytic His 150, especially for saccharic acid, might provide some insights into regiospecificity. These findings provide a foundation for better understanding how the 3-D structure of BAHD transferases relates to their substrate specificity, as we explore the chemistry of the active site and interactions with ligands. This could ultimately lead to better prediction of their function and ability to rationally design BAHD transferases to make useful and novel products.
O Programa Mais Médico para o Brasil (PMMB) e os gestores municipais: revisão de escopo
Authors: Mesquisa Eliana Mendes , Campelo Jorge Pessoa , Costa Cassandra Pereira Borges , Sousa Ronny Batista de , Ferreira Breno de Oliveira , Campelo Viriato
Published: February 2025

O presente estudo teve como objetivo mapear e analisar a literatura científica quanto as experiências de gestores da saúde sobre o Programa Mais Médicos. Trata-se de uma revisão de escopo realizada seguindo as orientações do protocolo (PRISMA-ScR) nas principais bases de dados: MEDLINE, por meio da PUBMED; LILACS, BDENF, via Biblioteca Virtual em Saúde (BVS), portal de periódicos CAPES e google acadêmico. Para construção da estratégia de busca foram utilizados descritores controlados e não controlados registrados no DeCS e no MeSH. Gestor de Saúde/Health Manager; Consórcios de Saúde/Health Consortia; Atenção primária a saúde/ Primary Health Care. Os operadores booleanos AND e OR foram utilizados para realizar os cruzamentos entre os descritores. Inicialmente, foram identificados um total de 236 estudos. Após triagem de elegibilidade, 11 estudos foram elegíveis para análise qualitativa. Os principais resultados mostram que, de maneira geral, o Programa Mais Médicos foi amplamente valorizado pelos gestores por ter preenchido lacunas importantes na cobertura médica e promovido avanços na Atenção Primária. A presença de médicos estrangeiros contribuiu para melhorias no acesso à saúde e na humanização do atendimento. No entanto, também foram identificados desafios substanciais, como a inadequação da infraestrutura das Unidades Básicas de Saúde, a necessidade de medidas estruturantes para garantir a sustentabilidade do programa, e fragilidades na rede de atenção à saúde, dificultando a continuidade do cuidado. Como conclusão, estudos adicionais poderiam explorar a eficácia do programa em diferentes configurações geográficas e administrativas, e analisar o impacto das políticas estruturantes propostas para garantir a sustentabilidade a longo prazo.
Qualidade pós-colheita de pedúnculos de cajueiro (Anarcardium Occidentale l.) submetido a armazenamento refrigerado
Authors: Silva Whashington Idalino da , Pereira Francisco Hevilásio Freire , Sousa Diogenes Damarsio Andrade de , Silva Francisco de Assis da , Gondim Ancélio Ricardo de Oliveira , Dias Mirandy dos Santos
Published: February 2025

Objetivou-se avaliar a qualidade pós-colheita dos pedúnculos de clones de cajueiro submetidos a armazenamento refrigerado. O trabalho foi desenvolvido no Laboratório de Fisiologia Vegetal do Centro de Ciências e Tecnologia Agroalimentar na Universidade Federal de Campina Grande-CCTA/UFCG. Os tratamentos foram compostos por 5 clones de cajueiro (CCP 76, BRS 189, BRS 226, BRS 265 e BRS 253) e 2 tempos de armazenamento (0 e 7 dias após a colheita), distribuídos em delineamento inteiramente casualizado em esquema fatorial 5×2 com 5 repetições. Avaliou-se:  massa fresca total, da castanha e do pedúnculo, diâmetro basal, apical, comprimento, coloração e firmeza do pedúnculo, sólidos solúveis totais, acidez total titulável, relação sólidos solúveis e acidez total titulável, pH, vitamina C, açúcares totais, luminosidade, cromaticidade e ângulo Hue. O armazenamento não influenciou nas características físicas dos clones de cajus, mostrando-se eficiente quanto a conservação.  O clone BRS 265 destacou-se com maiores valores na massa fresca total de frutos, massa da castanha, sólidos solúveis e reduziu a acidez titulável com o tempo de armazenamento. Os clones 226 e 189, obtiveram maiores índices de vitamina C, no entanto não houve variação entre o tempo de 0 e 7 dias de armazenamento.
Termoterapia via calor úmido no controle de patógenos em sementes de Dimorphandra gardneriana Tul
Authors: Messias Karla Danieli de Souza Vieira , Dias Francisca Hortência Couras , Silva Edcarlos Camilo da , Farias Otília Ricardo de , Silva Hilderlande Florêncio da , Nascimento Luciana Cordeiro do
Published: February 2025

Objetivando avaliar a eficiência da termoterapia via calor úmido na qualidade sanitária e fisiológica de sementes de Dimorphandra gardneriana. O experimento foi conduzido na Universidade Federal da Paraíba (UFPB), Campus II, município de Areia, Paraíba. As sementes foram submetidas a tratamento térmico via calor úmido. O teste de sanidade, germinação e emergência consistiu em onze tratamentos: T0: Testemunha (sementes não tratadas); T1: Fungicida de contato Dicarboximida; T2: 50o 10’ min, T3: 50o 15’ min, T4: 50o 20’ min, T5: 60o 10’ min, T6: 60o15’ min, T7: 60o20’ min, T8: 70o10’ min, T9: 70o15’ min e T10: 70o20’ min. A incidência do Fusarium sp. foi favorecida com o tratamento térmico via calor úmido na temperatura de 70°C durante 20 min. Ao analisar os resultados do teste de germinação verificou-se que a porcentagem de germinação GE e a PCG não apresentaram diferença estatisticamente. Houve diferença significativa apenas para os tratamentos, 50oC a 10 minutos e 70oC a 20 minutos. O tratamento 70oC influenciou negativamente as variáveis de Emergência (EM), primeira contagem de emergência (PCE) e índice de velocidade de emergência (IVE). Os resultados do presente trabalho indicaram boas perspectivas de utilização do tratamento térmico, na erradicação de Aspergillus sp e Penicillium sp em sementes de Dimorphandra gardneriana, não influenciando na qualidade fisiológica das mesmas. Do ponto de vista ambiental, é um método não-poluente ou sem efeito residual e deve ser recomendado para erradicação de patógenos.
Direcionamentos propostos para a redução do desperdício de alimentos no contexto de instituições públicas hospitalares no Estado do Tocantins
Authors: Santos Adão Pinto dos , Milan Gabriel Sperandio , Bochardt Miriam , Pereira Giancarlo Medeiros , Carmo Annibal José Roriz Rodriguez Scavarda do
Published: February 2025

O estudo apresenta um conjunto de direcionamentos propostos para diminuir o desperdício de alimentos em hospitais públicos localizados no Estado do Tocantins (TO). O desperdício de alimentos é visto como um indicador crucial para a sustentabilidade destes hospitais, pois está relacionado aos recursos empregados na produção de alimentos que não são consumidos e são descartados como resíduos alimentares. As quatro instituições hospitalares investigadas foram selecionadas devido à sua importância para o sistema de saúde regional. A pesquisa foi operacionalizada por meio de entrevistas individuais com uma abordagem semiestruturada, sendo que os dados foram analisados mediante análise de conteúdo. Os direcionamentos propostos foram focados em três dimesões: pessoas, tecnologia e processos. A formação e a sensibilização dos profissionais envolvidos, por meio de treinamentos regulares são essenciais, enquanto que a tecnologia e a inovação podem ser integradas aos sistemas de gestão alimentar dos hospitais investigados. Algumas práticas podem ser discutidas, como é o caso da importância de parcerias e da colaboração com fornecedores e o desperdício de alimentos. Quanto aos processos, é necessário gerir a performance dos fornecedores em relação à quantidade e qualidade dos alimentos ou refeições prontas entregues e seu envolvimento na previsão de demanda para evitar o desperdício de alimentos.
A Descriptive Analysis of Bank Employees' Views on Governance and Bank Success in South-West Nigeria
Authors: Alaba Adebayo Emmanuel , Ade Bello Sunday
Published: February 2025

This study explores bank employees' views on the role of governance in the success of banking institutions in South-West Nigeria. The research uses an ex-post-facto design, targeting bankers from Lagos, Ogun, and Oyo states. A sample of 600 bankers was selected through random sampling. The study distinguishes between senior ((Highly Ranked Bankers -HRB) and junior (Lowly Ranked Bankers - LRB) bankers to compare perceptions of board composition and its influence on governance and organizational success. Data were collected via questionnaires and analyzed using mean, standard deviation, and t-test statistics. Findings show differing views between HRB and LRB. Senior bankers disagreed with the view that directors involved in daily operations should be on the board, citing concerns over operational interference. Junior bankers, however, emphasized the importance of a balanced and diverse board. The t-test analysis revealed no significant difference in the perceptions of HRB and LRB regarding governance’s impact on organizational success. The study concludes that effective board composition, including independence, expertise, and diversity, is crucial for improving governance practices and ensuring better organizational outcomes. It recommends clearer role definitions for board members to enhance accountability and reduce conflicts.
Toward Drought-Resilient Legumes: Integrative Mechanisms and Breeding Strategies
Authors: Harshavardhan S. S. , Darvhankar M. S.
Published: February 2025

Drought stress adversely affects the growth, development, and output of legumes, presenting a considerable challenge to agriculture. This article analyzes the genetic, physiological, and biochemical factors that allow legumes to withstand dry conditions. It examines the impact of drought on germination, seedling establishment, vegetative growth, and reproduction, emphasizing the stages most influenced by water deficiency. The review examines the decline in yield and quality resulting from drought, along with the biochemical and genetic underpinnings of drought resistance. Essential drought-resistant genes, along with genomic methodologies like genome-wide association studies (GWAS) and quantitative trait loci (QTL) mapping, are highlighted as vital for the identification of advantageous features for breeding. The study examines breeding options for creating drought-resistant legume varieties, encompassing both traditional and biotechnological methods. This study examines the role of beneficial microorganisms in enhancing drought tolerance, emphasizing plant-microbe interactions that strengthen stress resilience. Additionally, appropriate management strategies for legume cultivation in arid conditions are examined, alongside physiological and biochemical indicators for evaluating drought resistance. This paper synthesizes existing research to explain the mechanisms of drought resistance in legumes and emphasizes prospective research avenues for enhancing drought resilience via breeding, biotechnology, and integrated management.
Farmers Perception of the Soil Health Card Scheme in Bilaspur, Chhattisgarh, India
Authors: Shastri Sakshi , Saha Anindita
Published: February 2025

The Soil Health Card (SHC) is a government initiative that provides farmers with soil nutrient information to guide the use of fertilizers and improve soil health. The perception of farmers plays a crucial role in the effective implementation of agricultural schemes. The study was conducted in Bilaspur district, Chhattisgarh, where the Deputy Director of Agriculture implemented the SHC scheme in the Bilha, Kota, Masturi, and Takhatpur blocks during its initial and second phases. These blocks were selected purposively, and villages within them were chosen randomly. A list of SHC beneficiary farmers was compiled, and 30 farmers from each block were randomly selected, totaling 120 participants. Data collection was done through personal interviews using a pre-structured schedule to assess farmers' perceptions of the SHC's utility. The study examined both independent and dependent variables, with data analysis techniques such as descriptive statistics and inferential methods used to explore the factors influencing farmers' perceptions, including education, exposure to mass media, and scientific orientation. The results indicated that 95.83% of farmers had a medium to high level of perception regarding the usefulness of SHC. This positive perception can be attributed to their educational background (secondary level and above), moderate exposure to mass media, and a medium level of scientific orientation. The study highlights that awareness, access to information, and a scientific approach significantly influence farmers' perception of the SHC scheme, emphasizing the need for continued efforts in knowledge dissemination and training to enhance its impact.
Impacts Caused By Vulvovaginal Candidiasis On The Health Of Women Of Reproductive Age: Integrative Review
Authors: Oliveira Maria Paula Almeida , Da Silva Maria Nauside Pessoa , Alves Fabrício Bezerra , Chagas Larissa Souza , Da Silva Redycson Rodrigues Alves , Macedo Luis Felipe Teixeira
Published: February 2025

The present study aimed to identify the impacts caused by vulvovaginal candidiasis on the health of women of
reproductive age. As a method, it is characterized as an integrative literature review study. The search was
carried out during the month of September 2023, in the databases: (MEDLINE); (LILACS) and (BDENF). In the
research, the Health Sciences Descriptors (DECS) and Medical Subject Headings (MeSH) were used: Women
AND Candidiasis, Vulvovaginal AND Risk Factors. The search in the databases identified 136 publications
after applying the exclusion criteria, 15 articles were eligible for qualitative analysis. As a result, two thematic
categories were created: Profile of women with vulvovaginal candidiasis, where factors such as age at the
beginning of sexual activity, number of children, pregnancy loss and the state of pregnancy itself did not
demonstrate significant associations with the occurrence of vulvovaginal candidiasis in women of reproductive
age, and the category impacts and factors associated with vulvovaginal candidiasis on women's health,
inadequate diagnosis can lead to chronic vulvovaginal conditions. Depression, anxiety and stress have been
identified as risk factors for vulvovaginal candidiasis. In conclusion, it is of great importance to emphasize the need for health education, improvement of clinical diagnostic techniques, screening during pregnancy, mental health assessment, awareness of other similar conditions and continued research
Expression of tubulin polyglycylation in Giardia lamblia
Authors: Campanati Loraine , Bré Marie Hélène , Levilliers Nicolette , De Souza Wanderley
Published: July 2002

Summry— By means of immunofluorescence, immunoelectron microscopy and immunoblotting, we show that polyglycylation, a posttranslational modification of tubulin widely spread among eukaryotes, is present in the diplomonad, Giardia lamblia, a putative ancestral cell possessing a highly developed microtubular cytoskeleton. This modification was recently discovered in the ciliated protist, Paramecium, and was not found in the Euglenozoa, a lineage considered as ancient. We used two monoclonal antibodies (mABs), TAP 952 and AXO 49, specifically recognizing mono‐ and polyglycylated tubulin isoforms, to detect this modification in Giardia extracts and to localize it in the different classes of microtubules within the cell. The α‐ and β‐tubulin subunits were recognized by the two mAbs, indicating that both tubulin subunits are glycylated, in agreement with lately reported mass spectrometry results. Noticeably, Giardia tubulin was much more reactive with AXO 49 than with TAP 952. In situ, AXO 49 intensely labeled the microtubules present in the four pairs of flagella and the median body, and lightly decorated the microtubules from the adhesive disc. In contrast, TAP 952 intensely labeled only the microtubules of the median body. The results indicate a differential expression of glycylated isoforms within various microtubular structures of Giardia lamblia. They also suggest that the complete set of enzymes required for polyglycylation is expressed in very divergent eukaryotes.
Optimizing transurethral microwave thermotherapy: a model for studying power, blood flow, temperature variations and tissue destruction
Authors: BolmsjÖ  , Sturesson  , Wagrell  , Andersson‐Engels  , Mattiasson
Published: July 2002

Objective

 To examine the role of microwave power and blood flow on temperature variations and tissue destruction in the prostate, using a theoretical model of transurethral microwave thermotherapy (TUMT), and thus compare fixed‐energy TUMT with no intraprostatic temperature monitoring (constant microwave power applied over a fixed period) with ‘feedback’ TUMT in which the microwave power is adjusted according to the monitored intraprostatic temperature.

Materials and methods

 The temperature distribution in the prostate was modelled for a typical TUMT catheter at various blood flow rates. The volume of tissue destroyed was simultaneously calculated from cell survival data after thermal exposure. The calculated quantity of tissue destroyed at the different microwave power levels and blood flow rates was used to describe qualitatively the simulated treatments.

Results

 Treatment monitoring and consistency were better during feedback TUMT than fixed‐energy TUMT, in that the former compensated for variations in blood flow rate. The modelled values agreed with observations during real TUMT.

Conclusions

 Blood flow rate is a key factor in the outcome of TUMT. Only by measuring intraprostatic temperature is it possible to compensate for the large variations in prostatic blood flow and obtain consistent treatment results. Repeated interruptions prompted by high rectal temperatures should be minimized and preferably avoided, as the quantity of tissue destroyed is then greatly reduced, and in extreme cases the treatment is totally ineffective.
III-V/II-VI double-barrier resonant tunneling structures
Authors: Yu E. T. , McGill T. C.
Published: July 2002

GaAs-ZnSe and InAs-ZnTe double-barrier resonant tunneling devices are proposed and analyzed theoretically. These structures would provide a novel way to study mixed III-V/II-VI materials systems and growth techniques, and may also yield devices that are faster and have greater peak-to-valley current ratios than GaAs-AlGaAs tunnel structures. In the GaAs-ZnSe system, the increase in speed is due to the smaller dielectric constant in ZnSe, compared to that in AlGaAs. In the InAs-ZnTe system, the increase in speed is due to the small dielectric constant in ZnTe and the high mobility in InAs, and the larger peak-to-valley ratio is due to the large conduction-band offset that is expected. We calculate current-voltage curves for these devices and show that their negative differential resistance current-voltage characteristics should be comparable or superior to those of GaAs-AlGaAs devices. The effects of band bending and the general method used to calculate current as a function of voltage are briefly discussed.
Analysis of the quantum-confined Stark effect in GaSb/AlGaSb multiple quantum wells
Authors: Carr Elizabeth C. , Wood Thomas H. , Burrus Charles A. , Chiu T. H.
Published: July 2002

We have measured the quantum-confined Stark effect in GaSb/AlGaSb multiple quantum wells. Our data are in good agreement with theory for electric fields from 2×104 to 13×104 V/cm. We found the effects of strain to be important in matching the theory to the low-field spectra.
Etching mechanisms of polymers in oxygen microwave multipolar plasmas
Authors: Pelletier J. , Arnal Y. , Joubert O.
Published: July 2002

A parametric study of polymer etching in an oxygen microwave multipolar plasma with independent rf wafer biasing is reported. The etch rate evolution as a function of atomic oxygen concentration, measured by actinometry, indicates a monolayer adsorption kinetics for the photoresist/oxygen system. Furthermore, a step-like variation in the etch rate with ion bombardment energy is observed. In the low-energy range, where sputtering effects are negligible, ion-induced chemical etching is the main etching component. In the high-energy range, an additional etching which exhibits sputtering behavior arises.
Structural defect related donor-bound exciton spectra in CdTe epitaxial films
Authors: Feng Z. C. , Burke M. G. , Choyke W. J.
Published: July 2002

In previous luminescence studies on CdTe epitaxial films, a line Dμ at 1.593 eV has been associated with the recombination of exciton bound to a neutral donor. We have new evidence to suggest that Dμ cannot be associated with a simple donor impurity, but should be associated with donor-like structural defects or impurity-defect complexes.
Injection locking characteristics of a 1 W broad stripe laser diode
Authors: Goldberg L. , Chun M. K.
Published: July 2002

Single narrow far-field lobe emission is observed in an injection-locked high-power broad stripe laser. Lobe widths below 1.3 times the diffraction limit for the 160-μm-wide stripe were observed for power levels up to 1.0 W. Decrease in the power contained within the narrow lobe for high laser bias currents is observed and is attributed to self-focusing effects in the active region. Small-signal external power gain of 21 dB was measured.
Modulation and spectral properties of semi-insulating blocked planar buried-heterostructure distributed feedback lasers
Authors: Eisenstein G. , Koren U. , Gnauck A. H. , Tucker R. S. , Koch T. L. , Corvini P. J. , Miller B. I.
Published: July 2002

We describe the spectral and high-speed modulation properties of 1.3-μm semi-insulating blocked planar buried-heterostructure distributed feedback lasers. We demonstrate the first single-frequency lasers with the capability for large-signal modulation at a bit rate as high as 16 Gb/s. The lasers exhibit a relatively small increase in spectral linewidth due to chirp even under high-speed modulation conditions.
Time-resolved reflectivity techniques for dynamic studies of electron beam recrystallization of silicon-on-insulator films
Authors: Timans P. J. , McMahon R. A. , Ahmed H.
Published: July 2002

A time-resolved reflectivity (TRR) technique has been developed for dynamic studies of swept beam heating of silicon-on-insulator (SOI) materials. The method exploits the temperature dependence of the reflectivity of SOI films to allow noncontact temperature measurement with high spatial and temporal resolution. This technique is of considerable practical importance for beam processing, since it allows the temperature distribution induced by a beam being scanned across a specimen to be determined. The temperature distribution produced by a line electron beam swept across a SOI specimen was experimentally measured and found to be consistent with a theoretical prediction. The TRR technique can also be used to study melting and will prove useful for characterizing zone melting recrystallization, where thermal modeling is often inadequate for the complex structures involved.
Structural characterization of a TlCaBaCu oxide in T
c onset=155 K and T
c zero=123 K superconducting specimens
Authors: Liang J. M. , Liu R. S. , Chang L. , Wu P. T. , Chen L. J.
Published: July 2002

The crystal structure of a Tl-Ca-Ba-Cu-O compound in Tc onset=155 K and Tc zero=123 K superconducting specimens was characterized by transmission electron microscopy. Convergent beam electron diffraction analysis established that the phase is of P4/mcc space group. The lattice parameters of the phase were determined to be a=b=0.394 nm and c=3.95 nm. The phase was found to be primarily of a ten-subcell structure by both high-resolution lattice imaging and diffraction pattern analysis. The composition of the grains with the ten-subcell structure being predominant was measured by energy dispersive spectrometry to be TlCa2Ba3Cu4Ox. Polytypes of the phase with four- and five-subcell structures were also observed. The five-subcell structure was identified to be of P4/mmm space group with a=b=0.394 nm and c=1.97 nm. The compositions of the specimens were measured to vary in composition ratios of Tl, Ca, Ba, and Cu from 1:2:2:3 to 1:2:3:4. The results strongly suggested that the TlCa2Ba3Cu4Ox phase is a high Tc superconducting phase with an exciting possibility that superconducting transition occurs at 155 K for this phase.
Si deposition by electron beam induced surface reaction
Authors: Matsui Shinji , Mito Masanobu
Published: July 2002

Si deposition has been achieved by electron beam induced surface reaction. An initial growth process for Si deposition using SiH2Cl2 source gas has been observed in situ by Auger electron spectroscopy. As a result, it became clear that the Si deposition growth rate is ∼0.3 Å/min at 7×10−7 Torr and that the deposition film contents (at. %) are 89% Si, 9.1% O, and 1.9% Cl. Moreover, a 0.5 μm linewidth Si pattern has been demonstrated by direct writing, using electron beam induced surface reaction.
Variable-energy positron-beam studies of SiO2/Si irradiated by ionizing radiation
Authors: Uedono A. , Tanigawa S. , Suzuki K. , Watanabe K.
Published: July 2002

Variable-energy positron-beam studies have been carried out on Si with a 1.61 μm overlayer of SiO2 irradiated by x ray and γ ray up to the dose of 5×105 R. The Doppler broadening of annihilation photons was found to be strongly influenced by x-ray irradiation, and the effect was extended homogeneously over the entire oxide layer. A trapping model which neglects positron diffusion effects was applied to the dependence of the line shape parameter S on incident positron energy.
Deep levels in n-InP grown by molecular beam epitaxy
Authors: Iliadis A. A. , Laih S. C. , Martin E. A.
Published: July 2002

Deep level transient spectroscopy was used to study for the first time the deep traps in n-InP grown by molecular beam epitaxy (MBE). Three electron traps B1, B2, and B3 were found to be present in the grown layers with activation energies of 0.43, 0.52, and 0.57 eV from the conduction-band minimum. Based upon our photoluminescence and secondary-ion mass spectroscopy data, trap B1 at 0.43 eV from the conduction band was linked to Fe atoms that probably form a phosphorus vacancy-Fe impurity complex. Traps B2 and B3, observed in the low growth temperature sample, were tentatively attributed to native defects resulting from the low temperature of growth. It is concluded that the MBE growth of InP at the high-temperature regime may improve the material quality.
Residual carbon acceptor incorporation in gallium arsenide grown by metalorganic chemical vapor deposition
Authors: Reed A. D. , Bose S. S. , Stillman G. E.
Published: July 2002

Two mechanisms controlling residual carbon acceptor incorporation in GaAs grown by atmospheric pressure metalorganic chemical vapor deposition have been identified: (1) the removal of the first methyl group from trimethylgallium in the gas phase, and (2) the removal of the first hydrogen atom from AsH3 adsorbed on the substrate surface. An analysis of the chemical reactions involved shows that the likely source of the residual carbon acceptor is the surface adsorbed trimethylgallium molecule rather than other carbon species in the reactor.
Channel sensitivity to gate roughness in a split-gate GaAs-AlGaAs heterostructure
Authors: Kumar Arvind , Laux Steven E. , Stern Frank
Published: July 2002

The response of the width of the electron channel at a GaAs-AlGaAs heterointerface to variations in the gate opening of a split-gate structure is calculated using a three-dimensional solution of the Poisson equation in the continuum approximation and is analyzed in terms of the Fourier components of the perturbation. It is found that the effective potential well for the channel electron gas attenuates high wave vector components of the gate roughness.
Enhancement of second-harmonic generation in optical fibers by a hydrogen and heat treatment
Authors: Ouellette François , Hill Kenneth O. , Johnson Derwyn C.
Published: July 2002

Optical fiber exposed to high-pressure hydrogen gas for 3–4 days, and subsequently heated in air at temperatures in the range 250–500 °C for 8–24 h, shows an enhanced second-harmonic conversion efficiency after seeding with 1.06 μm and 532 nm light, when compared with untreated fiber seeded under similar conditions. Up to now, an enhancement by as much as a factor of 4.4 has been observed. Some possible correlations between this enhancement and the change in the defect content of the fiber due to the H2 -heat treatment are pointed out.
High-temperature superconductor opening switch
Authors: Tzeng Y. , Cutshaw C. , Roppel T. , Wu C. , Tanger C. W. , Belser M. , Williams R. , Czekala L. , Fernandez M. , Askew R.
Published: July 2002

A jitter-free, repetitive opening switch made of YBa2Cu3O7−x high-temperature superconductor is demonstrated. The switch conducts electrical current at no loss when it is superconducting. A pulse or pulse train of magnetic field on the order of 100 G causes the transition of the switch from the superconducting state to the resistive normal state and forces current to flow through a load resistor that is connected in parallel with the switch. Repetitive operation of this switch at rep rates higher than 1 kHz has been demonstrated.
Ion pairing effects on substitutional impurity diffusion in silicon
Authors: Cowern N. E. B.
Published: July 2002

Recent experiments have shown that ion pairing has a major influence on the diffusion and precipitation of oppositely charged impurities in silicon. Published data are used to obtain ion pairing coefficients Ω for n-type impurities with B and In. A single value, Ω=0.17/ni, suffices to describe the cases P-B, As-B, and Sb-B. For P-In and Sb-In, Ω is roughly an order of magnitude smaller. These observations are consistent with the picture that paired ions occupy adjacent substitutional sites, with a small perturbation in their Coulomb binding arising from elastic effects.
Improvement in the crystalline quality of heteroepitaxial GaAs on Si films grown by modulated molecular beam epitaxy
Authors: Lee Henry P. , Liu Xiaoming , Wang Shyh , George Thomas , Weber Eicke R.
Published: July 2002

GaAs films were grown on Si substrates by a two-step method in which a thin buffer layer was first deposited using a modulated molecular beam epitaxy (MBE) technique followed by a thick layer grown by conventional molecular beam epitaxy. The film quality was evaluated using 77 K photoluminescence (PL) and double-crystal x-ray rocking curves. It was found that GaAs films grown in this way have a superior crystalline quality compared to the films prepared by normal two-step MBE. To investigate the nucleation of this buffer layer, thin GaAs layers (150 Å) were grown on Si substrates and examined by plan-view and cross-sectional transmission electron microscope. A thin, two-dimensional nucleation pattern was found in this sample, in clear contrast to the three-dimensional nucleation islands found in samples grown by conventional MBE. This showed conclusively that modulated beam molecular beam epitaxy resulted in a more uniform and two-dimensional nucleation during the initial stage of the growth as speculated earlier and is believed to be the reason for the improvement of the crystalline quality of the overgrown layer.
Quadratic electro-optic effect in polydiacetylene single crystals
Authors: Greene B. I. , Thakur M. , Orenstein J.
Published: July 2002

Direct measurements of the change in refractive index (Δn) as a function of applied electric field for polydiacetylene paratoluenesulfonate are reported. The magnitude of the effect is compared to that observed in GaAs, and a figure of merit with respect to device application is discussed.
Infrared to visible image frequency conversion in Cd(S,Se) glass composites
Authors: Acioli L. H. , Gomes A. S. L. , Rios Leite J. R. , de Araujo Cid B.
Published: July 2002

Wave mixing experiments are reported using two infrared and one visible laser beams which are incident on a semiconductor doped glass. The mixing process produces infrared to visible image conversion via the material electronic nonlinearity with fast (less than 20 ps) time response.
Picosecond electron drift mobility measurements in hydrogenated amorphous silicon
Authors: Schiff E. A. , Devlen R. I. , Grahn H. T. , Tauc J. , Guha S.
Published: July 2002

The electron photocarrier drift mobility in undoped, hydrogenated amorphous silicon was measured in the picosecond domain using optically detected time-of-flight techniques based on the electroabsorption effect. The electron drift mobility at room temperature was approximately 3 cm2 /V s between 50 and 500 ps at electric fields of (1–3)×105 V/cm, essentially the same as the mobility measured in the nanosecond domain. The picosecond measurement constrains transport models postulating larger electron mobilities shortly after photogeneration; the mobility lifetime product for a short-time process must be less than 3×10−11 cm2 /V. A slightly superlinear dependence of drift velocity upon an electric field was also found which could not be explained by dispersion effects.
Measurement of relaxation resonance, damping, and nonlinear gain coefficient from the sidebands in the field spectrum of a 1.3 μm InGaAsP distributed feedback laser
Authors: Lang R. J. , Mayer H.-P. , Schweizer H. , Mozer A. P. , Panknin P. , Elsässer W.
Published: July 2002

We calculate an expression for the fine structure in the field fluctuation spectrum of a semiconductor laser in terms of accessible device parameters. We measure the spectrum of an InGaAsP DFB laser and determine the linewidth, relaxation resonance, and damping versus current. From the relation between damping and current, we determine the nonlinear gain coefficient.
Scaling of an injection-controlled XeF(C→A) laser pumped by a repetitively pulsed, high current density electron beam
Authors: Hirst G. J. , Dane C. B. , Wilson W. L. , Sauerbrey R. , Tittel F. K. , Nighan W. L.
Published: July 2002

This letter reports the design and performance of a scaled, injection-controlled XeF(C→A) laser pumped by a repetitively pulsed, high current density electron beam with a temporal duration of 10 ns full width at half maximum. Injection of a 2 mJ pulse at 486.8 nm having a spectral width of <0.005 nm resulted in an amplified output of 0.7 J corresponding to energy density and efficiency values of 1.5 J/ℓ and 1.2%.
High-temperature superconductivity in ultrathin films of Y1Ba2Cu3O7−x
Authors: Venkatesan T. , Wu X. D. , Dutta B. , Inam A. , Hegde M. S. , Hwang D. M. , Chang C. C. , Nazar L. , Wilkens B.
Published: July 2002

We have grown ultrathin films of Y1Ba2Cu3O7−x in situ on (001) SrTiO3 by pulsed laser deposition. The zero resistance transition temperature (Tc0) is >90 K for films >300 Å thick. The critical current density (Jc at 77 K) is 0.8×106 A/cm2 for a 300 Å film and 4–5×106 A/cm2 for a 1000 Å film. The Tc0 and Jc deteriorate rapidly below 300 Å, reaching values of 82 K and 300 A/cm2 at 77 K, respectively, for a 100 Å film. Films only 50 Å thick exhibit metallic behavior and possible evidence of superconductivity without showing zero resistance to 10 K. These results are understood on the basis of the defects formed at the film-substrate interface, the density of which rapidly decreases over a thickness of 100 Å. We have studied these defects by ion channeling measurements and cross-section transmission electron microscopy. Our results suggest that the superconducting transport in these films is likely to be two dimensional in nature, consistent with the short coherence length along the c axis of the crystals.
Low-resistance contacts on YBa2Cu3O7−δ ceramics prepared by direct wire bonding methods
Authors: Suzuki Yoshihiko , Kusaka Tadaoki , Aoyama Takahiro , Yotsuya Tsutom , Ogawa Soichi
Published: July 2002

Wire bonding, such as electric discharge spot welding and ultrasonic bonding, has been investigated for use in simple, conventional methods of preparing low-resistance ohmic contacts on superconducting Y1 Ba2 Cu3 O7−δ ceramics. Spot welding with thermal annealing improves the contact’s resistivity to 2×10−7 Ω cm2 , while a sample without annealing shows non-ohmic and semiconductive characteristics. Change in the crystal structure induced by high current is analyzed. Ultrasonic bonding with annealing at 500 °C achieves 3×10−8 Ω cm2 , one of the lowest contact resistivities ever obtained in simple methods. The current-voltage characteristics show nonlinearity, which is attributed to the superconducting state of the Ag/Y1Ba2Cu3O7−δ interface.
Generation of thick Ba2YCu3O7 films by aerosol deposition
Authors: Kodas T. T. , Engler E. M. , Lee V. Y.
Published: July 2002

Thick superconducting films were fabricated by producing high-purity Ba2YCu3O7 particles by aerosol decomposition in a gaseous flow system, depositing the particles directly from the gas phase onto surfaces by thermophoresis, and then sintering and annealing the deposited particulate films in an oxygen flow. Particulate films with thicknesses of 1 mm were deposited on the inside surfaces of copper tubes and sintered to provide uniform adherent coatings with sharp superconducting transitions above 91 K. High-purity powders based on the Bi-Sr-Ca-Cu-O and Tl-Ca-Ba-Cu-O systems were also produced and sintered to form bulk ceramics with transitions at 80 and 110 K, respectively, suggesting that the process is general and can be used for a variety of materials. Advantages of the process include the ease of obtaining the correct oxygen content and the ability to fabricate thick films of fine grained material while minimizing exposure to carbon and other contaminants.
Scaling relations for strained-layer relaxation
Authors: Dodson Brian W. , Tsao Jeffrey Y.
Published: July 2002

Scaling relations for relaxation in strained-layer structures, based on simple descriptions of the dominant relaxation mechanisms and the influence of a stress-dependent relaxation activation energy, are obtained for general III-V semiconductor alloys. As a result, strained-layer relaxation in a given material system can be predicted over a wide range of structural parameters and temperature history based on a single relaxation measurement. This scaling treatment should prove useful in optimization of practical strained-layer device structures.
X-ray absorption fine structure of diamond films grown by chemical vapor deposition
Authors: Capehart T. W. , Perry T. A. , Beetz C. B. , Belton D. N. , Fisher G. B. , Beall C. E. , Yates B. N. , Taylor J. W.
Published: July 2002

We report the x-ray absorption spectra for two hard carbon films grown by filament-assisted chemical vapor deposition in gas mixtures of 1% and 0.18% methane in hydrogen. Although the Raman spectra of these two films suggest significant differences in structure, the x-ray absorption near-edge structure and extended x-ray absorption fine structure (EXAFS) are very similar. Analyzing the EXAFS from these films with a diamond crystal as a reference gives carboncarbon bond lengths of 1.53±0.03 Å. This result is consistent with diamond and incompatible with graphite. We conclude that the carbon films have the same local structure as diamond.
Kinetics of the solid-state amorphizing reaction in thin films studied by electrical resistivity
Authors: Rubin J. B. , Schwarz R. B.
Published: July 2002

We deposited Ni-Zr thin-film multilayers by electron beam evaporation onto polished alumina substrates. The multilayers were annealed at a constant heating rate, and in situ resistance measurements made to derive the growth kinetics of amorphous NiZr alloy at the Ni/Zr interfaces. Using a simple model that relates resistance change to amorphous-layer thickness, we derive the apparent diffusivity of nickel in amorphous Ni50Zr50, DNi =2.5×10−5 exp[−1.01(eV)/kT] cm2 s−1.
Broadband long-wavelength operation (9700 Å≳λ≳8700 Å) of AlyGa1−yAs-GaAs-InxGa1−xAs quantum well heterostructure lasers in an external grating cavity
Authors: Hall D. C. , Major J. S. , Holonyak N. , Gavrilovic P. , Meehan K. , Stutius W. , Williams J. E.
Published: July 2002

Data are presented on p-n AlyGa1−yAs- GaAs-InxGa1−xAs quantum well heterostructure lasers showing that the large band filling range of a combined GaAs-InxGa1−xAs quantum well makes possible a very large tuning range in external grating operation. Continuous 300 K laser operation is demonstrated in the 8696–9711 Å range (Δλ∼1000 Å, Δℏω∼150 meV) and pulsed operation in the 8450–9756 Å range (Δλ∼1300 Å, Δℏω∼200 meV). The band filling and gain profile are shown to be continuous from the InxGa1−xAs quantum well (Lz ∼125 Å, x∼0.2) up into the surrounding GaAs quantum well (Lz ∼430 Å).
Recombination-induced metastable to stable transformation of the EL2 center in GaAs
Authors: Sugiyama Toshinobu , Tanimura Katsumi , Itoh Noriaki
Published: July 2002

We carried out transient optical absorption measurements of the conversion, induced by electron pulse irradiation, of the GaAs EL2 between the normal (EL20) and metastable (EL2*) states. It is found that no thermal barrier exists in the EL2* to EL20 conversion when induced by electron pulse irradiation and that the yield of the EL20 to EL2* conversion is much lower than that of the reverse conversion. These conversion processes were attributed to arise from the electron-hole recombination at the EL2.
Ion-implanted In0.1Ga0.9As metal-semiconductor field-effect transistors on GaAs (100) substrates
Authors: Feng M. , Wang G. W. , Liaw Y. P. , Kaliski R. W. , Lau C. L. , Ito C.
Published: July 2002

Ion-implanted In0.1Ga0.9As metal-semiconductor field-effect transistors (MESFETs) have been fabricated on 3 in. GaAs (100) substrates. The structure comprises an undoped InGaAs epitaxially layer grown directly on a GaAs (100) substrate by the metalorganic chemical vapor deposition (MOCVD) technique. Si+28 is ion implanted into the InGaAs layer to form an active channel layer. MESFETs with 100 μm gate width and 0.5 μm gate length are fabricated using standard process techniques. The best device shows a maximum transconductance of 426 mS/mm. From S-parameter measurements, the current-gain cutoff frequency ft is 37 GHz and the maximum available gain cutoff frequency fmax is 85 GHz. These results are comparable to InGaAs MESFETs grown by MBE.
Optical window in strained-layer Si/Ge microstructures
Authors: Gell Michael
Published: July 2002

Theoretical predictions are presented of electronic and optical properties of the Si/Ge (2:6) superlattice grown on (001) SiGe buffers. It is shown that the buffer layer on which the superlattice is grown controls the polarization isotropy of the fundamental cross-gap transition and may be used to engineer an optical window for direct gap behavior.