bluuebunny/crossref_metadata_2025 huggingface dataset:
In-House Design, Manufacturing, and Testing of a 2.856 GHz Combline Microwave Cavity Filter for the Low-Level RF Systems of Linear Particle Accelerators
Authors: Giannetti G. , Bellaveglia M. , Gallo A. , Maddio S. , Mostacci A. , Piersanti L. , Serenellini B. , Selleri S. , Tocci S.
Published: February 2025

A combline microwave cavity filter has been developed to generate the 2.856 GHz radio frequency (RF) tone to be used as the master reference of SPARC_LAB electron linac facility at the Frascati National Laboratories of the National Institute for Nuclear Physics (LNF-INFN). The filter must select the 36th harmonic from a frequency comb with a repetition frequency of 79.33MHz and reject the other harmonics. The comb is generated by the electric conversion of the laser pulse train from the oscillator of the photocathode laser. Since a filter for this very specific application is off-the-shelf, it was designed, manufactured, and tested in-house at LNF-INFN. The measured insertion loss at the center frequency is 2.2 dB, the bandwidth is 30MHz (percentage fractional bandwidth is 1.1 %). This narrow bandwidth is required to ensure effective rejection (insertion loss > 65 dB) of adjacent harmonics in the frequency comb, specifically at frequencies of 2.77633 GHz and 2.93533 GHz. The purpose of filtering is to ensure that the tone, distributed in the low-level RF system, remains clean and can be used to synchronize the most crucial machine subsystems, such as RF power units, accelerating cavities, diagnostic systems, and lasers.
Corona or hydrochloric acid modulates embryonic diapause in silkworms by activating different signaling pathways
Authors: Zhang Yuli , Zhang Guizheng , Jiang Mangui , Wang Pingyang , Wang Xia , Cui Qiuying , Sun Quan
Published: February 2025

Background

To adapt to environmental changes, diapausing silkworm eggs remain dormant during the early stages of embryonic development. Various methods have been used to terminate silkworm egg diapause and promote egg hatching.

Methods

To elucidate the molecular mechanisms by which corona and other treatments terminate silkworm egg diapause, we collected eggs at 1, 6, and 20 h after treatments and sequenced their transcriptomes.

Results

The results showed that both corona and hydrochloric acid (HCl) treatments effectively terminated diapause and promoted egg hatching, with corona treatment inducing faster hatching than HCl treatment. Differentially expressed gene (DEG) analysis revealed the presence of fewer DEGs at 1 h, with a marked increase observed at 6 and 20 h post treatment. Functional enrichment analysis showed that the FoxO signaling pathway was activated at 6 h, with more substantial gene expression changes observed after corona treatment. In addition, HCl treatment appeared to activate the heat shock protein and hormone-regulated pathways. Our study results provide a basis for further analysis of the molecular mechanisms underlying diapause termination in silkworm eggs.
Seismic Performance of RC Frame Hospital Buildings Using Friction Dampers under Multiple Earthquakes
Authors: He HaoYang
Published: February 2025

Frequent earthquakes indicate that isolated seismic events are rare, with the probability of an independent earthquake typically not exceeding 10%. Earthquakes are not isolated phenomena and may occur in quick succession under certain conditions. If buildings are not reinforced, they may suffer significant damage or even collapse when subjected to subsequent earthquakes. Currently, most international seismic design codes only consider single seismic events, i.e., the effect of the main earthquake. Studying the seismic performance of buildings under multiple earthquakes is of great significance both academically and practically, under a seismic load of 620 Gallons, the damping structure reduced inter story displacement by 18% compared to traditional design, indicating improved elasticity.
Impact of Math Manipulatives on Grade One Pupils’ Attitudes and Academic Achievement
Authors: GUILLERMO BENJIE I.
Published: February 2025

This study examined the achievement levels of Grade One pupils and their attitudes towards the use of Math Manipulatives in teaching. It was conducted at Mataguisi Elementary School, Pudtol District, Division of Apayao, during the School Year 2023-2024. It specifically aimed to: 1) profile the respondents based on sex, educational attainment of parents, occupation of parents, and monthly income; 2) analyze the attitudes of the pupils towards Math Manipulatives; 3) determine any significant differences in these attitudes and achievements when pupils are grouped according to profile variables; and 4) assess the relationship between attitudes and achievement levels in mathematics. Since the enrollment of the school was small and manageable, complete enumeration was used.  Data were gathered using a questionnaire checklist specifically designed to capture pupils' attitudes towards Math Manipulatives, while academic achievements were determined from final grades recorded in the School Report Cards. The collected data were tabulated, analyzed, and interpreted using frequency counts, means, percentages, and weighted means alongside a five-point Likert scale for attitude assessment. Findings revealed that most parents of the respondents had attained only elementary education, and they were predominantly employed in low-income occupations. The overall mean score for pupils’ attitudes towards Math Manipulatives was 4.08, reflecting a general agreement among pupils on the positive effects of these teaching tools. Significant differences in attitudes based on the sex of the pupils were noted, while no significant differences were found regarding educational attainment or occupations of parents. The pupils achieved a weighted mean of 86.09%, categorized as “Very Satisfactory.” The study concludes that the use of manipulatives in mathematics instruction fosters greater interest, engagement, and self-confidence among pupils, contributing to enhanced academic performance. It is recommended that educators integrate manipulatives into curricular activities to support positive attitudes and achievements in mathematics education.
Identifying Efficient Marketing Channels for BT Cotton: The Case of Devbhumi Dwarka, Gujarat, India
Authors: Nakum M. M. , Bhalerao S. S. , Nayan P. , Kotvaliya N. A.
Published: February 2025

The marketing of Bt cotton is a critical component of the agricultural value chain, especially in regions like Devbhumi Dwarka, Gujarat. This study was conducted to estimate the marketing costs, margins, and price spread through different marketing channels of Bt cotton in the Devbhumi Dwarka district of the west Gujarat region. Total 120 number of Bt cotton farmers and market functionaries were randomly selected and interviewed for collecting information by using the designed schedule. Two major marketing channels were identified for Bt cotton: Channel-I (Producer → Cotton Corporation of India (CCI)) and Channel-II (Producer → Commission Agent → Ginner → Consumer). In Devbhumi Dwarka district, producers could secure approximately 86.44% of the consumer’s rupee in Channel-I and 82.64% in Channel-II. Consequently, Channel-I was found to be more efficient compared to other channels.
Advances in Skin Cancer Detection Using Machine Learning: Current Methods and Future Directions
Authors: Hasan Kazheen Ismael , Yasin Hajar Maseeh
Published: February 2025

With increasing incidence rates, high mortality risks, and substantial cost burdens, skin cancer is a serious global health concern. In order to improve patient outcomes, early and accurate detection is essential. Due to their heavy reliance on clinical knowledge, traditional diagnostic techniques are prone to subjectivity. In order to overcome these obstacles, automated skin cancer diagnosis has been using machine learning (ML) and deep learning (DL) models more and more. Convolutional Neural Networks (CNNs), Vision Transformers (ViTs), and ensemble learning models are among the ML and DL models that are methodically assessed and contrasted in this study for their ability to classify skin lesions. We examine how classification performance is affected by preprocessing methods, optimization tactics, and dataset selection. More specifically, this study makes use of publically accessible benchmark datasets including PH2, ISIC, and HAM10000 to guarantee a thorough assessment of model effectiveness. Our results show the benefits and drawbacks of various approaches, offering guidance for creating AI-driven diagnostic tools that are more precise, understandable, and useful for actual clinical settings.
Mycoremediation of Heavy Metals from Wupa River Using Aspergillus niger and Aspergillus fumigatus
Authors: U. F. Ibrahim , A. O. Omotosho , M. Abdulrasheed , H. Kanki , A. H. Ndanusa , M. I. Ibrahim , R. A. Tunau
Published: February 2025

Water pollution by heavy metals poses significant environmental and health risks, particularly in regions with high anthropogenic activities. This study evaluated the bioremediation potential of Aspergillus niger and Aspergillus fumigatus for heavy metal removal from water samples collected from the Wupa River in Abuja, Nigeria. The physicochemical parameters and heavy metal concentrations (lead, copper, and zinc) of the water samples were analyzed. The fungi were screened for their ability to remediate heavy metals, and their removal efficiency was assessed over an 8-day period. The results showed that Aspergillus niger achieved the highest removal efficiency for zinc (90%), while Aspergillus fumigatus was most effective for lead (83.77%). The consortium of both fungi demonstrated significant removal efficiency for all three metals, with lead removal reaching 83.77%. This study highlights the potential of fungal bioremediation as a sustainable and eco-friendly method for heavy metal removal from contaminated water bodies.
Knowledge and practices about techniques for inserting a peripherally inserted central catheter / Conhecimento e práticas sobre as técnicas de inserção do cateter central de inserção periférica
Authors: Furlan Colichio Aguida Thaisa , Scoqui Guimarães Carolina , Stabile Angelita , Cristina de Campos Pereira Silveira Renata , Gonçalves Menegueti Mayra , Salles Margatho do Nascimento Amanda
Published: February 2025

Objetivo: avaliar o conhecimento e as práticas dos enfermeiros sobre as técnicas de inserção do PICC. Método: estudo descritivo quantitativo, do tipo levantamento (Survey). A população do estudo foi constituída por 32 enfermeiros habilitados para inserção do PICC. A coleta foi realizada atraves do RedCap com as seguintes variáveis:  dados dos participantes; características do enfermeiro que insere PICC; características da instituição; avaliação Pré- Inserção do PICC e avaliação no Ato da Inserção. Resultado: a prática e o conhecimento dos enfermeiros na pré-inserção e inserção do PICC são bastante variados. Um destque pode ser feito para a utilização do ultrassom que é feita por 57,1% dos profissionais. Conclusão: evidenciou-se o conhecimento deficiente a respeito de questões sobre as técnicas de inserção do PICC e demonstrou-se que algumas práticas clínicas não estão em conformidade com o recomendado pelos guidelines de terapia infusional reconhecidos mundialmente.
Events supposedly attributable to vaccination or immunization against covid-19 in Brazil – scoping review / Eventos supostamente atribuíveis a vacinação ou imunização contra a covid-19 no Brasil – revisão de escopo
Authors: Santos William França dos , Elias Ivana Luiza da Silva , Silva Ítala Paula Morais da , Costa Thamyris Eduarda Moura da , Souza Jordana da Silva , Francisco Marta Maria
Published: February 2025

Objetivo: identificar na literatura científica, os tipos de eventos supostamente atribuíveis e seus fatores associados e relacionados à vacinação contra Covid-19 em adultos e idosos no Brasil. Método: revisão de escopo, realizada de junho a agosto de 2023; foram selecionados estudos primários, disponíveis na íntegra, publicados de janeiro de 2021 a agosto de 2023, em português, inglês ou espanhol, nas seguintes bases de dados: Embase, Pubmed, Scopus e BVS. Resultados: 14 artigos compuseram a amostra final; foi evidenciado que é frequente a ocorrência de eventos supostamente atribuíveis a vacinação ou imunização, majoritariamente, os eventos adversos não graves, todavia, eventos adversos graves também foram relatados, como trombose do sistema nervoso central, convulsões, dispnéia, paralisias faciais e óbitos. Conclusões: A predominância dos casos relatados nos estudos foram relacionados ao imunizante da Oxford-AstraZeneca e ocorreram principalmente em mulheres, na faixa etária de 30 a 50 anos.
Repercussions of chronic kidney disease on the life of a person undergoing dialysis treatment / Repercussões da doença renal crônica na vida da pessoa em tratamento dialítico
Authors: Vieira Alcivan Nunes , Nascimento Brenda Maria Tavares do , Costa Kalidia Felipe de Lima , Dantas Luana Adrielle Leal , Lopes Mariana Mayara Medeiros , Lima Deivson Wendell da Costa
Published: February 2025

Objetivo: analisar as implicações da Doença Renal Crônica na vida da pessoa em tratamento dialítico. Método: estudo qualitativo realizado por meio de entrevistas às pessoas com esta condição atendidas em um serviço de hemodiálise; os dados foram submetidos à análise de Bardin. Resultados e discussão: a perda crônica da função renal produziu impacto em vários aspectos da vida da pessoa, para além das alterações fisiológicas, incluindo na sua autonomia e inserção em atividades profissionais. Mudanças corporais e nos relacionamentos afetivos são relatadas com desconforto; a repercussão familiar reflete as adequações necessárias a esta nova condição. Considerações finais: A vivência do processo de adoecimento crônico devido à falência da função renal adquire perspectivas singulares delineadas pela história de vida, suporte familiar e assistencial ao qual a pessoa tem acesso. O conhecimento das necessidades de saúde pode subsidiar a produção do cuidado na perspectiva de ampliar o suporte às adaptações à doença.
Substrate‐induced acceleration of N‐ethylmaleimide reaction with the Cys‐65 mutant of the transposon Tn 10‐encoded metal‐tetracycline/H+ antiporter depends on the interaction of Asp‐66 with the substrate
Authors: Kimura Tomomi , Inagaki Youko , Sawai Tetsuo , Yamaguchi Akihito
Published: July 2002

We previously reported that the reaction of [14C]N‐ethylmaleimide (NEM) with the S65C mutant of the transposon Tn10‐encoded metal‐tetracycline/H+ antiporter (TetA(B)) is competitively inhibited by tetracycline [Yamaguchi, A. et al., FEBS Lett. 322 (1993) 201–204]. However, this observation has been revealed to be a mistake. The reaction of [14C]NEM with S65C TetA(B) was significantly and reproducibly accelerated by tetracycline, i.e. not inhibited. When Asp‐66 was replaced by Ala, the reaction of NEM with the Cys‐65 residue was no longer affected by tetracycline. In contrast, when Arg‐70 was replaced by Ala, the acceleration of the reaction was unaltered. The tetracycline acceleration of the reaction to the Cys‐65 residue was further stimulated with energization of the membrane on the addition of NADH. On the other hand, the tetracycline‐induced acceleration was not observed in the absence of a divalent cation. These observations indicated that the Cys‐65 locus is exposed to the medium according to the interaction of a divalent cationtetracycline chelation complex with Asp‐66.
Interleukin‐1β antagonizes phenobarbital induction of several major cytochromes P450 in adult rat hepatocytes in primary culture
Authors: Abdel-Razzak Ziad , Corcos Laurent , Fautrel Alain , Guillouzo André
Published: July 2002

We have investigated the effects of interleukin (IL)‐1β and IL6 on expression and phenobarbital (PB) induction of ethoxyresorufin O‐deethylase (EROD) and pentoxyresorufin O‐deethylase (PROD) activities, as well as on mRNA levels of cytochromes P450 (CYP) 1A, 2B, 2C, 2E and 3A, in rat hepatocytes in primary culture. IL6 slightly antagonized PB‐induced PROD activity. Strikingly, IL1β strongly inhibited basal EROD and PROD activities, and fully blocked their induction by PB in a dose‐dependent fashion. Furthermore IL1β completely suppressed PB induction of all CYP mRNAs analyzed. Our results demonstrate that IL1β can suppress basal CYP activities, as well as PB‐inducible expression of five CYP mRNAs in rat hepatocytes in primary culture.
Multiple roles for integrins during development
Authors: Beauvais‐Jouneau Alice , Thiery Jean‐Paul
Published: July 2002

Summry— Interactions between cells and extracellular matrix play a crucial role during development by controlling tissue remodelling and cell migration. Integrins are the main family of cell surface receptors for extracellular matrix. The knockout of integrin genes in mouse embryos has provided new insights into the function of these receptors during embryonic development and morphogenesis. The lethality observed either during embryonic life or after birth suggests that many integrins are essential.
Efficacy and tolerability of interleukin‐2 receptor blockade with basiliximab in pediatric renal transplant recipients
Authors: Vester Udo , Kranz Birgitta , Testa Giuliano , Malagò Massimo , Beelen Dietrich , Broelsch Christoph E. , Hoyer Peter F.
Published: July 2002

‘Abstract: Rejection remains a major threat in pediatric renal transplantation (Tx), causing graft failure and increased exposure to drugs. The new chimeric antibody, basiliximab, directed against the α‐chain of the interleukin‐2 receptor (IL‐2R), has been shown to be effective in preventing rejection episodes in adult renal transplant recipients. In our single‐center experience from Essen, Germany, we evaluated prospectively the efficacy and tolerability of basiliximab, in combination with cyclosporin A (CsA) and prednisone, in 38 unselected pediatric patients. Mean patient age at Tx was 10.1 yr. Twenty‐eight children received a cadaveric organ and 10 children received living‐related donor grafts. The 1‐yr patient survival rate was 100% and the 1‐yr graft survival rate was 95% (36/38 patients). No graft was lost as a result of immunological factors, and single rejection episodes were observed in eight patients (21%). Two of these rejections were steroid‐resistant and responded to tacrolimus rescue therapy. The rate of infections was not enhanced; overt cytomegalovirus (CMV) disease was observed in two patients only. Malignancies have not been seen to date. The blockade of the α‐chain of the IL‐2R lasted for up to 6 weeks. We conclude that the addition of basiliximab to standard immunosuppression in pediatric renal transplant recipients is well tolerated and results in a low incidence of rejection. The simple mode of application and the lack of side‐effects make basiliximab an especially useful adjunct in pediatric patients.
Enabling children: participation as a new perspective on child‐health promotion
Authors: De Winter M. , Baerveldt C. , Kooistra J.
Published: July 2002

As fellow citizens, all children need a stimulating social environment that helps them develop self‐respect and social competence. Developmental research, however, shows, that many children do not or cannot fulfil the social, moral or cognitive developmental tasks which are necessary for healthy development. A lack of opportunities for gaining meaningful social experiences can be seen as a major source of psychosocial and behavioural problems in children. On the contrary, active commitment in educational environments such as the school and the neighbourhood, helps them to get an increasingly better grip on their own lives and health. Moreover, such ‘children's participation’ appears to have a protective and preventive effect for health‐related problems. Therefore, it is argued, that ‘enablement’, a key‐element of both the Ottawa Charter on Health Promotion and the International Convention on the Rights of the Child, should be at the core of every child‐health promotion programme.
Selection‐dominant and nonaccessible epitopes on cell‐surface receptors revealed by cell‐panning with a large phage antibody library
Authors: Hoogenboom Hennie R. , Lutgerink Jan T. , Pelsers Maurice M. A. L. , Rousch Mat J. M. M. , Coote James , van Neer Nicole , de Bruïne Adriaan , van Nieuwenhoven Frans A. , Glatz Jan F. C. , Arends Jan‐Willem
Published: July 2002

To generate antibodies to defined cell‐surface antigens, we used a large phage antibody fragment library to select on cell transfectants expressing one of three chosen receptors. First,in vitropanning procedures and phage antibody screening ELISAs were developed using whole live cells stably expressing the antigen of interest. When these methodologies were applied to Chinese hamster ovary (CHO) cells expressing one of the receptors for a neuropeptide, somatostatin, using either direct cell panning or a strategy of depletion or ligand‐directed elution, many different pan‐CHO‐cell binders were selected, but none was receptor specific. However, when using direct panning on CHO‐cells expressing the human membrane protein CD36, an extraordinary high frequency of antigen‐specific phage antibodies was found. Panning on myoblasts expressing the rat homologue of CD36 revealed a similar selection dominance for anti‐(CD36). Binding of all selected 20 different anti‐(CD36) phage was surprisingly inhibited by one anti‐(CD36) mAb CLB‐IVC7, which recognizes a functional epitope that is also immunodominantin vivo. Similar inhibition was found for seven anti‐(rat) CD36 that cross‐reacted with human CD36. Our results show that, although cells can be used as antigen carriers to select and screen phage antibodies, the nature of the antigen target has a profound effect on the outcome of the selection.
Effects of central corneal thickness on measurement of intra‐ocular pressure in keratoconus and post‐keratoplasty
Authors: Patel S. , McLaughlin J. M.
Published: July 2002

Purpose: To measure and compare central corneal thickness (CT) and intraocular pressure (IOP) in keratoconus and post‐keratoplasty subjects and examine the CT‐IOP relationship.

Methods: 22 keratoconus (category I: six female sixteen male, average age 27.0 range 12–47) and 19 post‐keratoplasty (category II: ten female nine male average age 34.6 range 16–54) patients without other anterior segment conditions were recruited. Only one, non‐contact lens wearing, eye of the patient was included for analysis. Cornea was anaesthetised with non‐preserved 0.4% Benoxinate Hydrochloride. Using a randomised approach, CT was measured using a standard ultrasonic pachymeter. IOP was then measured using a standard Goldmann tonometer. At all times the tonometrist remained unaware of the corneal thickness values.

Results: The mean (±s.d.) values for CT and IOP respectively in the two categories were: (I), 445 (45) μ and 9.8 (2.3) mmHg, (II), 564(44) microns and 15.8 (3.9) mmHg.

Differences between I and II for both CT and IOP were significant ( t‐test, p=0.01). Within each category, a significant correlation between CT and IOP was not found. Pooling all pairs of data ( n=41) a significant relationship between CT and IOP was detected ( r=0.635, p=0.0001).

Conclusion: The results confirm the hypothesis that an eye with a thicker cornea tends to present with a higher measured IOP. In the management of keratoconus and other corneal surgical procedures, changes in CT will contribute to any apparent changes in measured IOP.
Protection from Natural Enemies in Managing Rare Plant Species
Authors: Bevill R. L. , Louda S. M. , Stanforth L. M.
Published: July 2002

Abstract: Natural enemies such as pathogens, herbivores, and seed predators can substantially limit the abundance of plants, including rare species. Vulnerability to particular enemies is likely to differ between life‐history stages. We hypothesized that short‐term protection of juvenile plants from herbivores can be used to increase population growth of rare species and thus improve the probability of long‐term persistence. Using the federally listed (threatened) Pitcher's thistle (Cirsium pitcheri ) as a model, we experimentally excluded insect herbivores from juvenile rosettes to evaluate the potential benefits of deliberate insect control as a tool for management of rare species. Herbivore effects varied spatially across the local environment. Excluding insects in portions of the habitat where herbivory was high had direct benefits, including a 53% decrease in juvenile plant mortality (60% to 7%) and a 10‐fold increase in seed production of juveniles that matured and flowered. In other areas, where herbivore‐induced juvenile mortality was relatively low, excluding insects either increased seed production of plants that flowered or had no major effect. Our data also suggest indirect benefits to the metapopulation via potential improvement in dispersal among patches. Temporal variation in growing conditions occurred between years, suggesting that multiple‐year exclusions would be most effective. Our study suggests that small–scale manipulation of often inconspicuous interactions between rare plants and their natural enemies can be an effective, relatively low‐cost tool for the management and restoration of rare plant species.
Outdiffusion of oxygen and carbon in Czochralski silicon
Authors: Shimura F. , Higuchi T. , Hockett R. S.
Published: July 2002

The outdiffusion behavior of oxygen and carbon in heat-treated Czochralski (CZ) silicon has been investigated by secondary ion mass spectroscopy. The results show that oxygen diffusion is greatly retarded by oxygen precipitation and strongly support a vacancy-dominant diffusion mechanism for oxygen in silicon. In carbon-doped CZ silicon, the diffusion of both oxygen and carbon is greatly enhanced at 750 °C, but is significantly retarded at 1000 °C. In conjunction with the infrared absorption data, the enhanced diffusion has been attributed to the formation of fast-diffusing O-C complexes, while the retarded diffusion of carbon has been tentatively attributed to the formation of slow-diffusing complexes, such as Si-O-C.
Temperature dependence of interstitial oxygen diffusion in antimony-doped Czochralski silicon
Authors: Oates A. S. , Lin W.
Published: July 2002

We have measured directly the diffusivity of interstitial oxygen in Sb-doped Czochralski silicon in the temperature range 750–1150 °C. Using secondary-ion mass spectroscopy of outdiffusion profiles, we show that the diffusivity is the same as that for lightly B-doped crystals heated under identical conditions over the temperature range studied. We briefly discuss the implication of these results upon oxygen precipitation mechanisms in Sb-doped silicon.
InGaAs/InP superlattice mixing induced by Zn or Si diffusion
Authors: Schwarz S. A. , Mei P. , Venkatesan T. , Bhat R. , Hwang D. M. , Schwartz C. L. , Koza M. , Nazar L. , Skromme B. J.
Published: July 2002

Recent studies have shown that Zn diffusion preferentially induces mixing (interdiffusion) of In and Ga in unstrained InGaAs/InP superlattices, with little diffusion of the anions. In the present study, a 3.1% lattice mismatch is accommodated in the mixed superlattice with no observable defects in layers on the order of the predicted critical layer thickness. At high concentrations, Zn resides preferentially in the InP layers in the form of Zn3P2. In marked contrast to this behavior of Zn, Si diffusion is observed to cause comparable interdiffusion on the cation and anion sublattices within a narrow range of dopant concentration. This result is at odds with some recent mixing models and is consistent with a divacancy mixing mechanism.
Titanium diffusion in silicon
Authors: Hocine S. , Mathiot D.
Published: July 2002

Titanium diffusion profiles in silicon were determined in the 950–1200 °C temperature range, with experimental conditions avoiding any oxygen or nitrogen contamination, which could perturb the boundary condition at the TiSi2/Si interface. Thus diffusivity values in the range 5×10−10–10−8 cm2 s−1 are obtained, and are about two orders of magnitude higher than previously reported.
Band-edge absorption coefficients from photoluminescence in semiconductor multiple quantum wells
Authors: Kost Alan , Lee H. C. , Zou Yao , Dapkus P. D. , Garmire Elsa
Published: July 2002

We describe a novel approach to determining absorption coefficients in thin films using luminescence. The technique avoids many of the difficulties typically encountered in measurements of thin samples, Fabry–Perot effects, for example, and can be applied to a variety of materials. We examine the absorption edge for GaAs/AlGaAs multiple quantum well structures with quantum well widths ranging from 54 to 193 Å. Urbach parameters and excitonic linewidths are tabulated.
Solid phase epitaxy of molecular beam deposited amorphous GaAs on Si
Authors: Yoshino Kiyohiko , Murakami Kouichi , Yokoyama Shin , Masuda Kohzoh
Published: July 2002

Solid phase epitaxial (SPE) crystallization of amorphous GaAs on (100) Si tilted by 4° toward 〈011〉 formed by molecular beam deposition (MBD) was first achieved by cw Kr laser irradiation for short durations. The ratio of As to Ga (y/x) in deposited amorphous GaxAsy films was varied from 0.4 to 1.2. During the laser irradiation, movement of the amorphous/crystalline interface was measured using time-resolved optical reflectivity (TROR). It was found from TROR and micro-Raman scattering measurements that hetero-SPE is attained in samples with As/Ga ratios ranging from 0.8 to 1.1 and that the interface roughness is larger than that observed in homo-SPE (e.g., MBD GaAs on GaAs and P+ ion-implanted GaAs).
Transient absorption spectroscopy of Kr2F(42Γ)
Authors: Greene D. P. , McCown A. W.
Published: July 2002

An optical multichannel detection system was used in conjunction with a pulsed xenon lamp and an ultraviolet preionized discharge to record the continuous absorption spectrum of Kr2F(42Γ-92Γ) in the 255–455 nm wavelength region. The absorbing species was positively identified by its temporal and F2 pressure dependences. Peak absorption occurs at 315 nm and has a half width of 85 nm.
cw diode pumped 2.3 μm fiber laser
Authors: Allen R. , Esterowitz L.
Published: July 2002

We report the first successful operation of a diode pumped continuous-wave (cw) thulium-doped fluorozirconate fiber laser at 2.3 μm. Output power of 1 mW and slope efficiency of 10% are demonstrated. Saturation effects limiting efficiency are observed and discussed.
Low-threshold continuous-wave room-temperature operation of AlxGa1−xAs/GaAs single quantum well lasers grown by metalorganic chemical vapor deposition on Si substrates with SiO2 back coating
Authors: Egawa T. , Tada H. , Kobayashi Y. , Soga T. , Jimbo T. , Umeno M.
Published: July 2002

We demonstrate the first room-temperature low-threshold continuous-wave (cw) operation of Al0.3Ga0.7As/GaAs single quantum well (SQW) heterostructure lasers grown by metalorganic chemical vapor deposition (MOCVD) on Si substrates using techniques of SiO2 back coating and thermal cycle annealing. The all-MOCVD-grown SQW lasers on GaAs/Si with etch pit density of 1.5× 107 cm−2 have threshold current as low as 55 mA (1.41 kA/cm2) under cw at room temperature. The SiO2 back coating is effective to obtain excellent current-voltage characteristics. Thermal cycle annealing is also found to improve the crystallinity of GaAs/Si and to contribute to room-temperature cw operation of the lasers on Si substrates.
Highly conductive and wide optical band gap n-type μc-SiC prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition
Authors: Futagi Toshiro , Katsuno Masakazu , Ohtani Noboru , Ohta Yasumitsu , Mimura Hidenori , Kawamura Kazuhiko
Published: July 2002

We have investigated the gas pressure dependence of electron cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition (PECVD) and prepared n-type μc-SiC:H with wide optical band gap (2.1–2.5 eV) and high dark conductivity (10−3– 1 S/cm). It has been suggested from plasma diagnoses of the ECR plasma that at low gas pressure a strong etching effect of hydrogen radicals and/or ions dominates the film growth process and the hydrogen ions impinging on the growing surface make the formation of μc-SiC:H difficult, and that at high gas pressure, for the formation of μc-SiC:H, there are nonemissive radicals contributing to the surface coverage or a nucleus formation mechanism which has not been taken into consideration in conventional rf-PECVD.
Second-harmonic generation of blue light in a LiTaO3 waveguide
Authors: Mizuuchi Kiminori , Yamamoto Kazuhisa , Taniuchi Tetsuo
Published: July 2002

We report blue light generation in a LiTaO3 waveguide by quasi-phase-matched (QPM) second-harmonic generation (SHG). A periodically domain-inverted structure for QPM is fabricated in LiTaO3 by proton exchange of a selective Ta-masked area using pyrophosphoric acid followed by heat treatment. By utilizing this structure and low-loss proton-exhanged waveguides, we have realized a third-order QPM-SHG device. As a result, 0.13 mW of harmonic blue light was generated for a conversion efficiency of 18%/W.
Reflectance-difference spectroscopy study of surface reactions in atomic layer epitaxy of GaAs using trimethylgallium and tertiarybutylarsine
Authors: Maa B. Y. , Dapkus P. D.
Published: July 2002

A real-time reflectance-difference spectroscopy (RDS) study of surface reactions of trimethylgallium (TMGa) and tertiarybutylarsine (TBAs) with (001)GaAs surfaces in an ultrahigh vacuum environment is reported. These studies reveal several phases of atomic layer epitaxy of GaAs using TMGa. A model consistent with various kinetics studies is established to explain the distinct behavior observed in RDS during TMGa exposures. It is shown that optimal growth conditions can be achieved through RDS monitoring. The self-limiting mechanism which occurs in TMGa exposure cycle is believed to result from both selective adsorption and reaction of TMGa at As atoms and Ga vacancy induced Ga-rich surface reconstruction. It is also shown that TBAs is a promising arsenic source for atomic layer epitaxy.
Electrical conduction in undoped diamond films prepared by chemical vapor deposition
Authors: Muto Y. , Sugino T. , Shirafuji J. , Kobashi K.
Published: July 2002

Electrical conduction along conducting layers between grains in chemical vapor deposited polycrystalline diamond films has been studied. The dc current-voltage characteristic consists of an ohmic region at low voltages and a highly nonlinear region at high voltages. As-grown films are dominated by the ohmic conduction with a small activation energy through disordered graphitic (disordered sp2 bonded carbon) regions between grains. When the as-grown film is annealed at 670 K, the conductivity of the ohmic region becomes governed by levels at 0.93 eV leading to a drastic decrease by several orders of magnitude, and the nonlinear conduction dominates. Hydrogenation of the annealed sample causes an increase in the conductivity around room temperature with little change in the high-temperature conductivity governed by 0.93 eV levels.
Epitaxial growth of BaTiO3 thin films by plasma-enhanced metalorganic chemical vapor deposition
Authors: Chern C. S. , Zhao J. , Luo L. , Lu P. , Li Y. Q. , Norris P. , Kear B. , Cosandey F. , Maggiore C. J. , Gallois B. , Wilkens B. J.
Published: July 2002

High-quality BaTiO3 thin films have been epitaxially grown on (001) LaAlO3 and (001) NdGaO3 substrates by plasma-enhanced metalorganic chemical vapor deposition at a substrate temperature of 680 °C. X-ray diffraction θ–2θ, ω, and φ scan results all indicate that single-crystalline BaTiO3 thin films were epitaxially grown on the substrates with 〈100〉 orientation perpendicular to the substrates. The high degree of epitaxial crystallinity is further confirmed by Rutherford backscattering spectrometry which gives a minimum yield of 7.5% and 11% for films deposited on LaAlO3 and NdGaO3, respectively. Cross-section high-resolution electron microscopy images also showed that the layer epitaxy of BaTiO3 was characterized by an atomically abrupt film/substrate interface. Scanning electron micrographs showed that these films had very smooth surface morphologies.
Observation of negative persistent photoconductivity in an n-channel GaAs/AlxGa1−xAs single heterojunction
Authors: Chen J. , Yang C. H. , Wilson R. A. , Yang M. J.
Published: July 2002

We report the first observation of negative persistent photoconductivity at 4.2 K in an n-channel modulation doped GaAs/Al0.33Ga0.67As single heterostructure, where two-dimensional electrons have a mobility of ∼550 000 cm2/V s when density is ∼3.0×1011 cm−2. Based on extensive magnetotransport measurements, we conclude that the negative persistent photoconductivity effect comes from the time dependence of (1) the annihilation of two-dimensional electrons by photoexcited holes, and (2) the trapping and de-trapping of photoexcited electrons by shallow donors in doped Al0.33Ga0.67As. A model that quantitatively explains the nonexponential recovery time is presented.
Anion-assisted pulsed laser deposition of lead zirconate titanate films
Authors: Leuchtner R. E. , Grabowski K. S. , Chrisey D. B. , Horwitz J. S.
Published: July 2002

A modification of the conventional pulsed laser deposition technique is presented whereby a low energy (≤0.5 eV) electron emitting filament was placed over the substrate during deposition. Using this experimental arrangement, it was possible to deposit oriented films of the ferroelectric perovskite PbZr0.52Ti0.48O3 on 〈100〉 MgO substrates at 550 °C. When optimized in terms of emission current, the use of the filament caused a decrease by six orders of magnitude in the ratio of a nonferroelectric pyrochlore phase relative to the ferroelectric perovskite phase. The surface morphology concomitantly changed from porous to essentially smooth as the electron emission current was increased. The surface reaction of oxygen anions generated by electron attachment to oxygen molecules is believed to be responsible for these crystallographic and morphological changes.
Variation of the Schottky barrier height of the differently oriented CoGa on GaAs by molecular beam epitaxy
Authors: Kuo T. C. , Wang K. L. , Arghavani R.
Published: July 2002

The Schottky barrier formation of CoGa on (100)n-GaAs is investigated. CoGa is grown by molecular beam epitaxy and the epitaxial orientation is controlled by the initial growth conditions of the GaAs substrate. Schottky diodes with three different phases of CoGa: (100)CoGa, (110)CoGa, and mixed (100) and (110)CoGa, are fabricated and Schottky barrier heights are measured by I-V, C-V, and internal photoemission. The fact that these three types of diodes have different values of barrier height indicates that the mechanisms of the barrier formation for these three phases are different. Finally, the temperature dependence of the Schottky barrier height is also examined and the barrier height is found to be constant from 150 to 300 K for each of the phases.
Improved performance of compressively as well as tensile strained quantum-well lasers
Authors: Krijn M. P. C. M. , ’t Hooft G. W. , Boermans M. J. B. , Thijs P. J. A. , van Dongen T. , Binsma J. J. M. , Tiemeijer L. F. , van der Poel C. J.
Published: July 2002

The results of a theoretical study together with an experimental verification of the effects of strain on the laser characteristics of InxGa1−xAs/InGaAsP quantum-well lasers are reported. It is shown that tensile strained quantum-well lasers can perform as well as compressively strained lasers with respect to the threshold current density. Both show an improved performance when compared to the unstrained case. The origin of this improved performance is discussed.
Reflection high-energy electron diffraction intensity oscillations and anisotropy on vicinal AlAs(001) during molecular-beam epitaxy
Authors: Shitara T. , Neave J. H. , Joyce B. A.
Published: July 2002

We have examined the reflection high-energy electron diffraction (RHEED) specular beam intensity oscillations on vicinal AlAs(001) which was grown on GaAs(001) substrates misoriented by 2° or 3° toward [110], [010], and [1̄10]. The temperature dependence of the RHEED oscillation behavior on vicinal surfaces is similar to that on GaAs(001) and InAs(001). The cation flux and misorientation angle dependencies of Tc on AlAs(001) also followed the same pattern as on GaAs(001), as expected. Similarly, the same anisotropic behavior was also obtained, in that Tc[110]≳Tc[1̄10]. Unlike GaAs(001), however, the surface reconstruction could not be kept constant during the growth mode transition and it is therefore very difficult to analyze AlAs(001) data in as much detail as that for GaAs(001), but from the similarity between them we have qualitatively estimated the effective surface migration barrier for Al adatoms on AlAs(001) as ∼1.74 eV.
Occurrence of layerlike growth mode in the formation of hydrogenated amorphous silicon film on graphite from SiH3 radicals
Authors: Kawasaki Mitsuo , Kawaguchi Yusuke
Published: July 2002

Based on an x-ray photoelectron spectroscopy (XPS) analysis, we could gain new implication on the growth mechanism of hydrogenated amorphous silicon (a-Si:H) from SiH3 radicals. Despite the choice of a considerably small deposition rate and a chemically inert graphite substrate, the substrate signal underwent approximately single-exponential decay with deposition time. Within the capability of XPS of distinguishing different film-growth modes, as independently tested by comparing XPS and scanning tunneling microscopy data taken for sputter-deposited gold, the occurrence of a layerlike a-Si:H growth is strongly suggested.
X-ray characterization of Si δ-doping in GaAs
Authors: Hart L. , Fahy M. R. , Newman R. C. , Fewster P. F.
Published: July 2002

High-resolution triple-axis x-ray diffractometry has been used to examine the structural properties of a δ-doped superlattice of sixty periods, each consisting of half a monolayer of Si and 500 Å of GaAs, grown by molecular beam epitaxy (MBE) at 400 °C under an arsenic flux. The measurements indicated that the superlattice was of high structural quality. Using dynamical simulation, it was demonstrated that the period variation was equal to 3%, while the silicon spreading was no greater than 2 monolayers. It was possible to extract this information because of the high-resolution diffractometer which produced the theoretical line shape and wide dynamic range. Using a simple model, it was deduced that virtually all Si atoms were located on Ga lattice sites.
Electrically active, ion implanted boron at the solubility limit in silicon
Authors: Liefting J. R. , Schreutelkamp R. J. , Vanhellemont J. , Vandervorst W. , Maex K. , Custer J. S. , Saris F. W.
Published: July 2002

For 30 keV B implants in Si, doses above 1.5×1014 B/cm2 will lead to dislocation formation during a subsequent 900 °C anneal to make the B electrically active. Although dislocations are avoided for doses <1.5×1014 B/cm2, the B concentration is only ∼1×1019 B/cm3, a factor of 4–5 lower than the solid solubility of B in Si at 900 °C. Using multiple implant/anneal steps, we demonstrate here that implanted, electrically active B can be introduced up to the solid solubility limit while avoiding dislocation formation.
Quantum-confined Stark effect in interdiffused AlGaAs/GaAs quantum well
Authors: Li E. Herbert , Chan K. S. , Weiss Bernard L. , Micallef Joseph
Published: July 2002

The quantum-confined Stark effect is analyzed in an interdiffused Al0.3Ga0.7As/GaAs single quantum well (QW) with an as-grown well width of 100 Å, where the confinement profile is modeled by an error function. Results indicate a twofold enhancement of the Stark shift for the interdiffused quantum well over that of the square quantum well for a 50 kV/cm applied field. The fundamental exciton absorption peak also shows a much larger reduction with increasing applied field in the more extensively interdiffused QW. These characteristics may be used to realize optical modulators with higher on/off ratios and lower drive voltages.
Self-assembly of a homopolymer mixture via phase separation
Authors: Krausch Georg , Kramer Edward J. , Rafailovich Miriam H. , Sokolov Jonathan
Published: July 2002

We propose a mechanism for creating lateral order in thin films of a homopolymer mixture via spinodal decomposition in the presence of a laterally structured substrate surface. The system under consideration is a mixture of deuterated polystyrene and partially brominated polystyrene (PBrxS, x=0.5) spuncast onto different substrates from toluene solution. We demonstrate that periodic stripe-like domain structures can be observed in the polymer films after spinodal decomposition on a periodic array of Cr lines on a H-terminated Si surface. The effect vanishes when the chemistry of the underlying structure is changed, strongly indicating an interface-driven ordering of the polymer film.
Quantum reflection and transmission of ballistic two-dimensional electrons by a potential barrier
Authors: Ying X. , Lu J. P. , Heremans J. J. , Santos M. B. , Shayegan M. , Lyon S. A. , Littman M. , Gross P. , Rabitz H.
Published: July 2002

Measurements of the reflection and transmission coefficients of ballistic two-dimensional electrons by a potential barrier, induced via a surface gate, reveal that both coefficients vary gradually with the barrier height when it is less then the electron Fermi energy. Superimposed on the gradual variation, oscillatory structure which are consistent with interference resonances are also observed. The data imply that the potential barrier seen by the two-dimensional electrons is sharp compared to the electron wavelength.
Room-temperature characterization of InGaAs/AlAs multiple quantum well p-i-n diodes
Authors: Ghisoni M. , Parry G. , Hart L. , Roberts C. , Stavrinou P. N.
Published: July 2002

We report the growth and fabrication of strained InxGa1−xAs/AlAs multiple quantum well p-i-n diodes, where 5.6%<x<15.3%. Characterization via high-resolution x-ray diffraction shows that for the higher indium composition, partial relaxation of the strain has occurred. Using photocurrent spectroscopy, we demonstrate that all the samples studied (whether partially relaxed or not) show (i) strong room-temperature excitonic features and (ii) under an applied electric field, a strong quantum confined Stark effect with retention of clearly resolvable excitons for fields up to ≊300 kV/cm. Both these results can be attributed to the substantial confining potential caused by our use of AlAs barriers. The results demonstrate that the system has potential use for the production of optical modulators.
Ethyliodide n-type doping of Hg1−xCdxTe (x=0.24) grown by metalorganic molecular beam epitaxy
Authors: Benz R. G. , Conte-Matos A. , Wagner B. K. , Summers C. J.
Published: July 2002

Conductive n-type Hg1−xCdxTe epitaxial layers with x=0.24 were grown by metalorganic molecular beam epitaxy using iodine doping. Ethyliodide was chosen as the dopant precursor based on previous results obtained for CdTe. The low-temperature (20 K) electron concentration increased from an undoped level of ∼1015 cm−3 to 5×1018 cm−3 for ethyliodide flow rates from 10−4 to 10 sccm. High electron mobilities were measured and secondary ion mass spectrometry measurements indicated a high degree of electrical activity. These results demonstrate that iodine is a highly effective n-type dopant for long-wavelength HgCdTe alloys and device structures.
High-temperature specific heat by a pulse-heating method
Authors: Wire M. S. , Fisk Z. , Webb G. W.
Published: July 2002

A pulse-heating method for measuring specific heat and electrical resistivity to high temperatures is described. This technique can be used for electrically conductive materials from room temperature to near 1300 K. As an example of this method, measurements of zirconium are presented.