bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuevas narrativas en publicidad. El storydoing como modelo de comunicación que favorece la cocreación del relato de marca entre los usuarios de Instagram
Authors: Rodríguez-Ríos Antonio , Lázaro Pernias Patrícia
Published: July 2022

Internet ha generado nuevos paradigmas de comunicación, por lo que las marcas han desarrollado nuevas estrategias basadas en el compromiso social, un aspecto que las ayuda a destacar en una era saturada de mensajes. En este contexto, el storydoing se presenta como un nuevo discurso publicitario de carácter narrativo que implica a las personas en una causa social y hace que participen cocreando y difundiendo el relato de marca a través de sus redes sociales digitales. El presente trabajo tiene como objetivo identificar los mecanismos narrativos con los que los usuarios de Instagram extienden el storytelling de marca. Para ello, se ha llevado a cabo un análisis de contenido de 691 publicaciones de usuarios de Instagram, de 12 campañas storydoing recogidas del anuario Los Anuncios del Año y del archivo creativo c de c. Dicho análisis ha consistido en marcar en la muestra la presencia de los elementos narrativos que propone el modelo actancial de Greimas (1971) teniendo en cuenta los recursos de la narrativa audiovisual de Canet y Prósper (2009). Los resultados muestran nuevas fórmulas narrativas visuales cuyo pivote central es la relación entre un sujeto y el propósito de la campaña como objeto de deseo en un escenario propiciado por la propia marca.
Influencers de ciencia en YouTube. Divulgación científica en el contexto español de la plataforma hegemónica de vídeo online
Authors: Buitrago Álex , Torres Ortiz Lidia
Published: July 2022

Tras el inicio de década se ha incrementado el uso de plataformas de vídeo online como alternativa al consumo de medios audiovisuales tradicionales (IAB, 2021). Este artículo explora la divulgación científica presente en el contexto español de YouTube —plataforma hegemónica de vídeo online—, focalizando en el análisis de contenido de piezas audiovisuales generadas por influencers de ciencia que cohabitan en YouTube junto a canales de moda, videojuegos y todo tipo de social media entertainment. Para ello, se empleó una orientación metodológica cualitativa –basada en un set de categorías discursivas– que se aplicó sobre la producción de una muestra de seis de los divulgadores científicos más representativos de la youtubesfera española. Los resultados despliegan las estrategias discursivas de las piezas analizadas y visibilizan las particularidades de un tipo de divulgación científica –generada por influencers de ciencia– que convive dentro del ecosistema mediático con los medios generalistas y las fuentes oficiales científicas. En concreto, los divulgadores científicos de YouTube apuestan por un formato audiovisual que combina el cuidado formal con la estética youtuber y un tono ameno basado en unos códigos comunes compartidos con la comunidad. Pese a tratarse de un tipo de comunicación científica aún en ciernes, los resultados de este estudio apuntan a la divulgación en YouTube como un vehículo eficiente para captar la atención del público joven hacia la ciencia y al compromiso de los creadores estudiados por un discurso basado en el rigor científico y la información de calidad.
Citizenship or political? The Twitter accounts that the Media and their Directors started to follow
Authors: Israel-Turim Verónica , Micó-Sanz Josep Lluís
Published: July 2022

Digital platforms have transformed the influence streams among media, journalists, politicians and the citizenship, as well as concerning gatekeeping and agenda setting  (Guo and Vargo, 2017; Wallace, 2018; Casero-Ripollés, 2021). Nonetheless, homophilic tendencies among power groups continue to be reproduced online (McPherson, Smith-Lovin and Cook, 2001; Maares, Lind and Greussing, 2021). With the objective of contributing to the deepening of the understanding of the dynamics and influence flows online among power elites, we analyzed via a machine learning Software, the 50 accounts that the network of the most followed Media Directors in Spain began following and compared them with the accounts that the Media they manage started following. We categorized them in Types of accounts, Location and Gender, and analyzed the repetitions between the accounts they began to follow to subsequently work with data visualization methods in order to find trends and tendencies (Bail, 2014; Batrinca and Treleaven, 2015). The results of this research indicate that some patterns of behavior differ between both networks, such as the gender and types of accounts they began following, whereas the location presented similar trends. The year where we can see the highest similarities corresponds to 2018, an electoral year in Spain, where both networks started following a majority of Spanish male politicians.
Interacción y fidelización de las audiencias digitales en la ficción televisiva: el transmedia en el caso de la serie L’Alqueria Blanca de À Punt
Authors: Marin Pérez Benjamin , Bañon Castellón Lola
Published: July 2022

El trasvase de las audiencias televisivas tradicionales al entorno digital y al consumo pluripantalla ha determinado que las cadenas reorganicen la difusión de contenidos en diferentes plataformas. La estrategia transmedia en las series de ficción busca la participación de los espectadores para posibilitar que se conviertan en reduplicadores y colaboradores en la formación de las tramas. La televisión pública ha fomentado estas nuevas formas narrativas como forma de fidelizar a las audiencias. En el caso de la televisión autonómica valenciana, L’Alqueria Blanca supone un caso especial puesto que se trata de una serie de éxito interrumpida abruptamente por el cierre de la cadena Canal 9 y recuperada ocho años más tarde en la nueva À Punt. Esta investigación analiza la introducción de la estrategia transmedia en esta serie tradicional en el ámbito digital y sus resultados de fidelización. La metodología se cimenta en el estudio de las plataformas que configuran la estructura transmedia de la serie para determinar la respuesta de los públicos ante las interacciones.  Se concluye que facilita no solo la recuperación de anteriores audiencias, de ese público más mayor, sino que incorpora además a espectadores que están ya situados en la línea del consumo digital (25-44 años). Además, este aumento de las audiencias los días de emisión supone un mayor consumo de televisión en todas las franjas de edad.
La difusión de valores corporativos a través de la estructura de contenidos en RTVE Play y Atresplayer
Authors: Rodríguez-Martelo Talia , Maroto González Isaac
Published: July 2022

La identidad corporativa en televisión como forma de transmitir los valores que representa un canal determinado se configura a través de diferentes elementos comunicativos que construyen esta imagen. La evolución constante del sistema mediático promovido por Internet, los entornos digitales y las plataformas VOD suponen una transformación de la estrategia comunicativa de la identidad corporativa de la televisión. La presente investigación realiza un análisis exploratorio y descriptivo para determinar si la organización de contenidos en las plataformas televisivas de Atresmedia y RTVE, Atresplayer y RTVE Play respectivamente, difunden los valores con los que las corporaciones mediáticas se identifican y quieren transmitir a su audiencia. A través de una metodología basada en el análisis de contenido se han mapeado las secciones y subsecciones de las plataformas y se han analizado cualitativamente sus contenidos y categorización para luego establecer una relación entre estas estructuras y los valores con los que se representa cada corporación. Los resultados apuntan que la organización de contenidos refleja la naturaleza estructural de cada televisión. La plataforma de la televisión pública se centra ofrecer contenido generalista y plural que atiende a los valores sociales que contempla su identidad. Por su parte, la plataforma de Atremesdia refleja un interés por promover los contenidos propios buscando un alcance promocional en la organización de contenidos sin apenas encontrar una relación con los valores que representa.
Ecosistema y dinámicas de innovación en una narración digital interactiva de éxito: flujo de trabajo del webdoc Parir en el siglo XXI
Authors: Grandío Pérez María del Mar , Aguado Terrón Juan Miguel
Published: July 2022

Este artículo tiene como objetivo principal sistematizar el flujo de trabajo del webdoc de éxito Parir en el Siglo XXI para comprender la confluencia entre el proceso creativo innovador y la implicación de distintos actores de un ecosistema de innovación en el sector de la comunicación en España, sustanciado en una narrativa digital interactiva específica. Para ello, se ha realizado una investigación empírica en profundidad del proceso creativo de este webdoc basada en cuatro entrevistas en profundidad semi-estructuradas a todos los agentes responsables de este formato (Barret Cooperativa/RTVE Lab/À Punt Mèdia/Datadista) junto con el análisis del dossier creativo y maqueta de navegación proporcionados por Barret Cooperativa a efectos de esta investigación. Los resultados obtenidos muestran un modelo abierto de producción circular en el que se respeta la libertad creativa de creadores independientes y cada agente aporta valor desde su especialidad técnica, al mismo tiempo que se genera una cultura empresarial colaborativa auspiciada por la asesoría y apoyo financiero de entes públicos. Se detecta la necesidad de estandarización de los procesos de testeo de la experiencia del usuario, así como la creación de protocolos internos de evaluación de los factores de éxito de la narrativa digital interactiva estudiada.
Editorial. El desarrollo de nuevas narrativas y formatos en el campo de la comunicación
Authors: Marzal-Felici Javier , Casero-Ripollés Andreu
Published: July 2022

Editorial del número 24.
Resistance to CD95/Fas‐induced and ceramide‐mediated apoptosis of human melanoma cells is caused by a defective mitochondrial cytochrome c release
Authors: Raisova Monika , Bektas Meryem , Wieder Thomas , Daniel Peter , Eberle Jürgen , Orfanos Constantin E. , Geilen Christoph C.
Published: July 2002

Intracellular CD95/Fas‐signaling pathways have not been investigated in melanoma yet. Two different CD95 receptor‐induced apoptotic pathways are presently known in other cell types: (i) direct activation of caspase‐8 and (ii) induction of ceramide‐mediated mitochondrial activation, both leading to subsequent caspase‐3 activation. In the present study, five of 11 melanoma cell populations were shown to release cytochrome c from mitochondria, which activates caspase‐3 and finally results in DNA fragmentation upon treatment with the agonistic monoclonal antibody CH‐11. In contrast, this apoptotic pathway was not activated in the remaining six melanoma cell populations. Interestingly, the susceptibility of melanoma cells to CD95L/FasL‐triggered cell death was clearly correlated with N‐acetylsphingosine‐mediated apoptosis. Our results are in line with a defect upstream of mitochondrial cytochrome c release in resistant cells.
Raspberry Ketone from Submerged Cultured Cells of the Basidiomycete Nidula niveo‐tomentosa
Authors: Böker Andreas , Fischer Manuela , Berger Ralf G.
Published: July 2002

The basidiomycete Nidula niveo‐tomentosa produced 4‐(4‐hydroxyphenyl)‐butan‐2‐one (raspberry ketone), one of the character impact components of raspberry flavor, and its corresponding alcohol. A systematic attempt was made to improve the productivity of this fungus. Variation of nutrient medium composition, precursor amount, time of supplementation, and cultivation period yielded a 50‐fold increase in metabolite concentrations. Raspberry ketone and alcohol were easily isolated from the culture medium by solvent extraction. Glycosidically bound forms or accumulation of raspberry compounds in fungal cells were not detected. This microbial process offers an alternative for the production of natural raspberry flavor.
Influence of Fungal Elicitors on Production of Ajmalicine by Cell Cultures of Catharanthus roseus
Authors: Namdeo Ajay , Patil Shridhar , Fulzele Devanand P.
Published: July 2002

Suspension cultures of Catharanthus roseus ( C. roseus) were elicited with fungal cell wall fragments of Aspergillus niger (A.niger), Fusarium moniliforme (F. moniliforme), and Trichoderma viride (T.viride). The effects of elicitor dosage, exposures time, and age of subculture on ajmalicine accumulation were studied. A higher concentration of elicitor extract responded positively to C. roseus suspension cultures. Ajmalicine accumulation increased by about 3‐fold when cells were treated with A.niger, F. moniliforme, and T. viride. The maximum ajmalicine production (75 μg g−1 dry weight (DW)) was observed in cells treated with T. viride. Cell cultures were elicited with 5% preparation of A. niger, F. moniliforme, and T. viride and exposed for 24, 48, 72, and 96 h. for elicitation. Suspension cultures elicited with T. viride for 48 h showed a 3‐fold increase (87 μg g−1 DW) in ajmalicine contents, whereas A. niger and F. moniliforme synthesized a 2‐fold increase in alkaloid and yielded 52 and 56 μg g−1 DW ajmalicine, respectively. C. roseus cells of different age (5,10, 15, 20, and 25 days old) were treated with a 5% elicitor of A. niger, F. moniliforme, and T. viride and investigated elicitors activity at different age of cell cultures. Maximum yield 166 μg g−1 DW of ajmalicine was synthesized in 20 day old suspension cultures treated with T. viride. A longer period of incubation of cell cultures with elicitors adversely affected the ajmalicine synthesis.
AUDIT OF OUTPATIENT LAPAROSCOPIC CHOLECYSTECTOMY
Authors: Fleming Universities Of Melbourne Hpb Group: William R. , Michell Ian , Douglas Malcolm
Published: July 2002

Background: Because the postoperative stay after laparoscopic cholecystectomy (LC) has shortened, it seemed that outpatient LC would be feasible. The aim of this study was to prospectively audit initial experience with outpatient LC at the Austin and Repatriation Medical Centre. We aimed to determine appropriate patient selection criteria, to devise anaesthetic and discharge protocols and to assess patient satisfaction at follow up.

Methods: All patients presenting for LC were assessed for suitability, and those elective cases unlikely to have a duct stone and fulfilling the social criteria were studied. After standard anaesthetic and LC technique, patients recovered in the day surgery unit for up to 8 h and were discharged if stable. The hospital in the home nursing service monitored patients for 48 h and arranged readmission if needed. Patient satisfaction was assessed by independent telephone questionnaire 6 weeks postoperatively.

Results: Forty‐five patients (median age 43 years) underwent outpatient LC with a discharge rate of 82.3%, resulting in a cost saving of $984 per patient treated. One patient was readmitted, giving an overall success rate of 80%. After stricter implementation of the protocol in the second half of the study, the discharge rate rose to 92%. Patient acceptance of the technique was high at 84.5%.

Conclusions: The results of the first 45 patients show that it is possible to safely perform outpatient LC with a low admission rate in fit, elective patients who live close to medical care. Provided a strict anaesthetic protocol is followed, the technique has good patient acceptance and provides some economic benefit to the hospital.
Urethroplasty for balanitis xerotica obliterans
Authors: Venn  , Mundy
Published: July 2002

Objective

 To review the results of different methods of urethroplasty for anterior urethral strictures caused by balanitis xerotica obliterans (BXO).

Patients and methods

 Twenty‐eight patients underwent urethroplasty for BXO; 12 had a one‐stage pedicled penile skin‐flap urethroplasty and 16 excision and a two‐stage free‐graft urethroplasty using nongenital skin.

Results

 The treatment failed in all patients undergoing a one‐stage pedicle penile skin urethroplasty because the disease recurred with BXO, whereas the treatment failed in only one patient using a two‐stage free graft procedure.

Conclusion

 A two‐stage free‐graft urethroplasty using nongenital skin is recommended for anterior urethral strictures caused by BXO.
A five‐year evaluation of intervention in diabetes care in Trinidad and Tobago
Authors: Gulliford M. C. , Mahabir D.
Published: July 2002

Aims To evaluate an intervention to improve diabetes care in government‐run heath centres in Trinidad and Tobago over 5 years.

Methods A cross‐sectional survey of 690 subjects with clinical diabetes attending nine health centres was carried out in 1993. The intervention was: reports to the Ministry of Health, dissemination of management guidelines and annual training workshops for healthcare staff. Re‐evaluation was through a survey of 1579 subjects with diabetes, attending 23 health centres in 1998.

Results Comparing 1993 with 1998, foot examinations in the previous year increased from 38 (6%) to 346 (22%) and fundoscopy from 6 (1%) to 139 (9%). For subjects attending for 1 year or less, 34/96 (35%) had dietary advice recorded in 1993 compared with 77/143 (54%) in 1998. Exercise advice was recorded for 3/96 (3%) in 1993 and 48/143 (34%) in 1998. In 1993, 329 (48%) were taking chlorpropamide but this fell to 57 (4%) in 1998. Glibenclamide use increased from 214 (31%) to 856 (54%) and gliclazide from four (1%) to 205 (13%). In 1993, 198/338 (56%) of hypertensive subjects were taking Brinerdin, this fell to 56/829 (7%) in 1998 while use of thiazide diuretics, methyldopa and angiotensin‐converting enzyme (ACE) inhibitors increased. There were no changes in indicators of metabolic control, blood pressure control or body weight.

Conclusions Use of audit data to inform health policy and practice, linked with educational interventions, may modify patterns of care in government‐run primary care health centres in a middle‐income country with a high prevalence of diabetes.
Methodologic Issues in Conducting Research on Hospitalized Older People
Authors: Berkman Cathy S. , Leipzig Rosanne M. , Greenberg Sherry A. , Inouye Sharon K.
Published: July 2002

OBJECTIVE: To describe challenges in conducting research with hospitalized geriatric patients.

DESIGN: Quasi‐experimental longitudinal study with in‐person interviews at baseline and discharge and a three‐month postdischarge telephone interview. Study protocol required baseline interviews within 48 hours of admission for patients or 72 hours for proxies.

SETTING: 813‐bed urban teaching hospital.

PARTICIPANTS: 240 patients, mean age 83.8 years, at moderate to high risk for functional decline during hospitalization, admitted from the emergency room to a general medical unit.

MEASUREMENTS: Delays starting or interruptions continuing interviews; patient and environmental conditions potentially affecting data quality; and information on proxy use.

RESULTS: Timely access to patients or proxies was a major difficulty, resulting in the screening of only 53.1% of 867 potentially eligible patients. Multiple patient contacts and visits were required to complete interviews. Only 61.3% of baseline and 28.1% of follow‐up interviews were completed on the initial day of contact. Despite having on‐site interviewers 7 days a week, 29% of discharge interviews were conducted by telephone. Interviews were> 90% complete in 487 of 503 of encounters (97%). Baseline delays and interruptions were usually due to the presence of medical staff, off‐unit tests, patient illness, nurse unavailability for interview, and need for a proxy. Most in‐hospital interviews were conducted with others present. Proxies were required for approximately one‐third of patients at all three interviews.

CONCLUSION: Conducting clinical research with older adults in the current inpatient setting, where patients are more severely ill yet have shorter lengths of stay now than in the past, proves a challenging yet achievable goal. Effective procedures for negotiating the acute care environment are critical to successful studies.
Sulfur as a surface passivation for InP
Authors: Iyer R. , Chang R. R. , Lile D. L.
Published: July 2002

We have investigated the use of liquid and gas phase sulfur pretreatment of the surface of InP as a way to form a near ideal passivated surface prior to chemical vapor deposition of SiO2 . Results of high-frequency and quasi-static capacitance-voltage measurements as well as enhancement mode insulated gate field-effect transistor (FET) transconductance and drain current stability studies all support the efficacy of this approach for metal-insulator-semiconductor application of this semiconductor. In particular we have measured surface state values in the range of 1010 to a few 1011 cm−2  eV−1 and enhancement mode FET drain current drifts of <5% over a 12 h test period.
108 GHz passive mode locking of a multiple quantum well semiconductor laser with an intracavity absorber
Authors: Sanders Steve , Eng Lars , Paslaski Joel , Yariv Amnon
Published: July 2002

A two-section multiple quantum well laser is passively mode locked without an external cavity at ∼108 GHz. The pulse widths average 2.4 ps and have a time-bandwidth product of 1.1. Self-pulsations at frequencies up to 8 GHz are also observed.
Measured brightness of electron beams photoemitted from multicrystalline LaB6
Authors: Oettinger P. E.
Published: July 2002

Laser-driven semiconductor photoemitters can provide the very bright beams of electrons needed in advanced accelerators. However, these semiconductors are easily degraded in operation. Photoemissive testing of the compound LaB6, which is expected to be a more environmentally rugged material, has shown that under excimer laser irradiation normalized electron beam brightnesses of 6.7×106 , 2.6×106 , and 1.5×105 A/cm2  rad2 can be achieved at photon wavelengths, respectively, of 193, 248, and 308 nm.
Effect of spacer layer thickness on the static characteristics of resonant tunneling diodes
Authors: Mehdi I. , Mains R. K. , Haddad G. I.
Published: July 2002

A self-consistent quantum mechanical simulation is used to study the effect of spacer layer thickness on such resonant tunneling diode properties as the peak current and peak-to-valley current ratio. It is found that with a low cathode doping the peak current is insensitive to the commonly used spacer layer thickness. However, for higher cathode doping the peak current decreases with increasing spacer layer thickness. This phenomenon is explained on the basis of the junction potential between the heavily doped cathode contact region and the undoped double-barrier region. Thus, for device applications where a high current density is desired the cathode spacer layer should be designed as thin as possible.
Construction of an all-optical flip-flop by combination of two optical triodes
Authors: Tsuda Hiroyuki , Kurokawa Takashi
Published: July 2002

An optical flip-flop with two nonlinear étalons as inverter gates was investigated. The results show that the device works well for a large coupling constant, large detuning (which lead to a high contrast and stable operation), and short feedback delay. Based on calculated results, an optical flip-flop was constructed by coupling two optical triode switches using a nonlinear étalon and gradient-index lenses, and successful operation was demonstrated.
Limits of imaging resolution for atomic force microscopy of molecules
Authors: Weihs T. P. , Nawaz Z. , Jarvis S. P. , Pethica J. B.
Published: July 2002

The imaging resolution of an atomic force microscope operating in contact with a Langmuir–Blodgett (LB) film is predicted as a function of applied force, tip radius, adhesive force, and tip and film properties. The elastic modulus and the hardness of the LB film were measured using a nanoindenter and the imaging resolution is predicted using both a simple Hertzian elastic analysis and one that includes adhesive forces between the tip and the sample. For a small applied force (<1 nN) the resolution improves sharply as the tip radius and the adhesive force decrease. The onset of inelastic deformation, however, limits the resolution of the sharpest tips.
Sr2RuO4: A metallic substrate for the epitaxial growth of YBa2Cu3O7−δ
Authors: Lichtenberg F. , Catana A. , Mannhart J. , Schlom D. G.
Published: July 2002

Single crystals of Sr2RuO4 were grown by the floating zone melting technique. The crystals have the K2NiF4 structure and display a metallic resistivity behavior in the a-b-plane between 300 and 4.2 K (ρab≂10−4 Ω cm at 300 K). The in-plane lattice mismatch between YBa2Cu3O7−δ (001) and Sr2RuO4 (001) is smaller than 1.3%, better than that to SrTiO3 {100}. Epitaxial films of YBa2Cu3O7−δ with Tc(R=0) as high as 86 K have been grown on Sr2RuO4 crystals. The epitaxial growth of YBa2Cu3O7−δ on Sr2RuO4 was revealed by four-circle x-ray diffraction as well as by transmission electron microscopy.
Correlation of Raman and photoluminescence spectra of porous silicon
Authors: Tsu R. , Shen H. , Dutta M.
Published: July 2002

The discovery of luminescence in electrochemically etched porous silicon is an extremely important scientific breakthrough with enormous technological implications. It opens the door for silicon, the most important microelectronic material, as a possible material for optoelectronics applications. Our result, a correlation of Raman and photoluminescence spectra, shows that the observed luminescence is originated from extremely small microstructures. As the luminescent peak increases in photon energy, the Raman feature shifts to lower energy, remaining sharp, and eventually splits, developing into TO and LO modes. No peak at 480 cm−1 is observed, which indicates no substantial contribution from an amorphous region. These data provide strong evidence of the role of microstructures in porous silicon.
Sharp-line photoluminescence of GaAs grown by low-temperature molecular beam epitaxy
Authors: Yu P. W. , Reynolds D. C. , Stutz C. E.
Published: July 2002

We report sharp-line photoluminescence spectra from GaAs layers grown by low-temperature molecular beam epitaxy. The photoluminescence consists of no-phonon line (A) at 1.467 eV and associated phonon sidebands of both lattice and localized vibrational modes. Photoluminescence features, layer growth condition, and heat treatment of the layer for the complex responsible for the photoluminescence spectrum are found to be consistent with the C3v symmetry of the complex. The spectra reveal five local phonons having stronger intensity compared to the lattice phonon. We propose that the complex is due to the nearest-neighbor VGa-Asi pair.
Simultaneous multiwavelength operation of Nd:YAG laser
Authors: Danailov M. B. , Milev I. Y.
Published: July 2002

Operation of pulsed Nd:YAG laser simultaneously at 1.052, 1.061, 1.064, and 1.074 μm is reported. The suppression of the weaker lines by the strongest line (1.064 μm) is avoided by using a cavity scheme which disperses the frequency components transversely in the crystal. The frequency doubling of this radiation in KDP provides several new lines.
Directional light coupling from microdisk lasers
Authors: Levi A. F. J. , Slusher R. E. , McCall S. L. , Glass J. L. , Pearton S. J. , Logan R. A.
Published: July 2002

We describe methods for directional coupling of light output from whispering-gallery mode microdisk lasers. Patterned asymmetries in the shape of microdisk resonators provide control of both direction and intensity of light output without dramatically increasing laser thresholds.
Point defect generation during high temperature annealing of the Si-SiO2 interface
Authors: Devine R. A. B. , Mathiot D. , Warren W. L. , Fleetwood D. M. , Aspar B.
Published: July 2002

Spectroscopic identification of the microscopic defects responsible for annealing induced degradation of the oxide in Si/SiO2/Si structures is presented. Hole injection or x irradiation reveals the presence of oxygen-vacancy centers and oxygen-vacancy center/Si interstitial complexes in the oxide following annealing. O related donors in the Si substrate are also present. These defects result from the diffusion of O from the SiO2 network into the Si; the primary driving force for O diffusion is the difference in the chemical potential of the O in the two phases.
Pulsed laser deposition of VO2 thin films
Authors: Kim D. H. , Kwok H. S.
Published: July 2002

High quality vanadium dioxide (VO2) thin films have been successfully deposited by pulsed laser deposition without postannealing on (0001) and (101̄0) sapphire substrates. X-ray diffraction reveals that the films are highly oriented with (010) planes parallel to the surface of the substrate. VO2 thin films on (0001) and (101̄0) substrates show semiconductor to metal transistions with electrical resistance changes as large as 4×104, 105, respectively. Thin films on (101̄0) substrate have a transition at as low as 55 °C with a hysteresis less than 1 °C. These transition properties are comparable with single crystal VO2.
Two approaches to construction of vibrating probes for electrical current measurement in solution
Authors: Scheffey Carl
Published: July 2002

Two systems are described that implement the vibrating probe method for recording the voltage field in electrolyte solutions. The method has a spatial resolution of 5–40 μm and very low drift. The first system is a simple device that allows inexpensive but reliable use of the method to record the field in one dimension. It is based on a metal electrode vibrating along a line, with power supplied by a single piezoelectric bimorph. The second is a more complex system, with computer support, that measures the field in two dimensions, acquires the data to the computer disk, and plots the field measurement on a video image of the experimental preparation. A π-shaped linkage of three bimorphs is used to move the metal electrode in two dimensions. Motor micrometers with optical encoders are used to move the electrode and monitor its position.
Nonperturbing electron beam probe to diagnose charged-particle beams
Authors: Pasour John A. , Ngo Mai T.
Published: July 2002

A nonperturbing diagnostic tool which is capable of precisely measuring the position and charge distribution of charged-particle beams, including those from rf accelerators, is described. The diagnostic uses as a probe a low-energy (1–20 keV), μA-level electron beam, which is injected across the path of the primary beam to be diagnosed. The probe electrons are deflected as they pass near or through the primary beam, after which they are collected by a suitable detector. The deflection of the probe electrons depends on the position of the primary beam relative to the test beam as well as on the charge distribution of the primary beam. Consequently, by measuring the deflections, one can determine these primary beam parameters. Calculations which illustrate the capabilities of this technique are presented, and the design and performance of a prototype version of the diagnostic are described. The prototype results agree very well with the calculations, verifying the theory and demonstrating the fundamental soundness of the approach for measuring the position and charge distribution of a relativistic beam. Although the prototype has only been tested with relatively low-energy beams (<500 keV), the extension to highly relativistic beams is straightforward and completely described by the theory. Based on these results, we have a very high degree of confidence that the diagnostic is fully capable of operating as predicted by the calculations.
A novel computer based pseudo-logarithmic capacitance/conductance DLTS system specifically designed for transient analysis
Authors: Doolittle William A. , Rohatgi Ajeet
Published: July 2002

A new inexpensive, simple to construct, PC based deep level transient spectroscopy (DLTS) system has been developed that efficiently digitizes and analyzes capacitance and conductance transients by conventional DLTS methods (boxcar, rectangular, and exponential) as well as by several transient methods (nonlinear least squares, modulation function methods, and correlation method of linear predictive modeling). A unique ‘‘pseudo-logarithmic’’ sample storage scheme allows each transient to be sampled at more than 11 different rates, permitting 3 to 5 decades of time constants to be observed in one thermal scan allowing the resolution of closely spaced defect energy levels. The high system flexibility allows weighting times (or transient observation times) to be selected between <200 μs to 3 days. This is the first report that details the merits, including faster response and recovery times, of using the new Boonton 7200 capacitance meter in a DLTS system. This is also the first reported use of the pseudo-logarithmic sample spacing to enhance the range of time constants observable in a single thermal cycle as well as the first use of selectable resistance values in conjunction with selectable capacitance values to allow the conductance and capacitance to be sampled simultaneously in high resolution mode (<1 fF and <0.01 μS). It is shown experimentally that the transient analysis capability of this system can separate closely spaced deep levels where the conventional DLTS methods fail.
A new scheme for Langmuir probe measurement of transport and electron temperature fluctuations
Authors: Tsui H. Y. W. , Bengtson R. D. , Li G. X. , Lin H. , Meier M. , Ritz Ch. P. , Wootton A. J.
Published: July 2002

A new scheme to extend the triple Langmuir probe technique for the measurement of electron temperature fluctuations and the fluctuation-driven transport has been developed. The extension is aimed at reducing the phase delay error introduced by finite probe tip separations in standard triple-probe method. The modified triple-probe scheme provides a more reliable measurement of the temperature fluctuations for a proper interpretation of the density and potential fluctuations and the transport measurement from Langmuir probe data. New results on fluctuations have been obtained from Phaedrus-T and TEXT-U tokamaks.
High mobility GaAs heterostructure field effect transistor for nanofabrication in which dopant-induced disorder is eliminated
Authors: Kane B. E. , Pfeiffer L. N. , West K. W.
Published: July 2002

We have fabricated field effect transistors with undoped GaAs channels, undoped AlxGa1−xAs barriers, and either n+GaAs or epitaxial Al gates. Low resistance ohmic contacts are made separately to the gate and channel in samples with 250 Å barriers and in which the depth of the channel below the top surface is 900 Å. Because electrons in the channel are neutralized by conducting charge on the gate, they do not experience the dopant-induced disorder inevitable in modulation doped structures. Electron mobility is above 106 cm2/V s, even when their Fermi wavelength exceeds 1000 Å, making these devices ideally suited for nanofabrication.
An electron optical theory of beam blanking
Authors: Gesley M.
Published: July 2002

Trajectory equations are derived in closed form for electrons in time-dependent electric fields produced by beam blankers. Simple parallel plate and double-deflection blankers with transmission delay lines are evaluated. Lens imaging of the apparent beam motion is analyzed by developing the virtual electron trajectories obtained from linear extrapolation back into the blanker region. Lens excitation effects and conjugate blanking optics can then be described. The blanker voltage is represented by a damped exponential cosine term, which satisfies a typical circuit equation for the driver-amplifier. The form of the trajectory equation is written as a 3×3 matrix, which comprises a set of conditional solutions that are determined by blanker geometry. The optimum delay line length of any double-deflection blanker can then be determined. The blanker-induced beam jitter is shown to be significantly reduced by using this configuration. The effect of the blanker beam stop on the motion at the target plane is given by combining results on the real and apparent beam trajectories.
A new method for measuring liquid surface tension with acoustic levitation
Authors: Tian Yuren , Holt R. Glynn , Apfel Robert E.
Published: July 2002

A new method utilizing an acoustic levitation technique is introduced to measure liquid surface tension. During the measurement a small drop of test liquid is acoustically levitated in air, and its static shape is gauged with the variation of its altitude location. The experimental data are matched with theoretical calculations giving an estimation of liquid surface tension. Due to its noncontact manipulation and requirement for a small amount of test sample, this method can be applied in many special situations.
Measurement of the x-ray spectrometric properties of cesium hydrophthalate (CsAP) crystal with the synchrotron radiation
Authors: Beck L. , Stemmler P. , Legrand F.
Published: July 2002

The spectrometric properties of several hydrophthalate crystals (KAP, RbAP, TlAP, and CsAP) are studied. Especially investigated is cesium hydrophthalate for which little information is available in the literature. Experimental measurements of rocking curves at 1000 and 2500 eV performed on the SB3 beamline of Super ACO storage ring (LURE-Orsay) are presented. The experimental results are compared with calculations made with a new version of BRAGG, a preprocessor of the ray-tracing SHADOW. This improved version allows to generate rocking curves of any crystal structures. The results of the perfect crystal model matches well with the experimental observation. Among the selected crystals CsAP shows the highest reflectivity.
Pulsed thrust measurements using laser interferometry
Authors: Cubbin E. A. , Ziemer J. K. , Choueiri E. Y. , Jahn R. G.
Published: July 2002

An optical interferometric proximeter system (IPS) for measuring thrust and impulse bit of pulsed electric thrusters was developed. Unlike existing thrust stands, the IPS-based thrust stand offers the advantage of a single system that can yield electromagnetic interference-free, high accuracy (<2% error) thrust measurements within a very wide range of impulses (100 μN s to above 10 N s) covering the impulse range of all known pulsed plasma thrusters. In addition to pulsed thrusters, the IPS is theoretically shown to be capable of measuring steady-state thrust values as low as 20 μN for microthrusters such as the field emission electric propulsion thruster. The IPS-based thrust stand relies on measuring the dynamic response of a swinging arm using a two-sensor laser interferometer with 10 nm position accuracy. The wide application of the thrust stand is demonstrated with thrust measurements of an ablative pulsed plasma thruster and a quasi-steady magnetoplasmadynamic thruster.
Introduction to a kinetics-sensitive double-step voltcoulometry
Authors: Thurzo I. , Gmucová K. , Orlický J. , Pavlásek J.
Published: July 2002

As an alternative to the numerous state-of-the-art versions of voltammetry, a kinetics-sensitive double-step voltcoulometry is introduced. The transient current flowing in response to a potential step across the electrochemical cell is integrated and simultaneously processed by a deliberately selected time-domain “cascade” filter, while scanning the applied potential. In contrast to the widely used sampling scheme of sampling the transient current just before and in the end of the excitation pulse, three values of the transient charge are sampled in the interval between subsequent excitation pulses. Each measuring period is preceded by a single measurement of the steady-state current with the excitation pulse being switched off. The latter measurement makes it possible to actively compensate the parasitic charge across the feedback capacitor of the integrator, due to the steady-state current, while storing the steady-state current data. The goal of introducing the third sampling event resides in discriminating the kinetics of the transient charge via the parameter β that enters the time dependence of the transient charge Δq∝tβ. In general, our filtering scheme is capable of eliminating both any constant or linear components in the transient charge (β=0, 1). Moreover, any superlinear transient charge (β>1) is detected as a peak of the Δq versus potential plot with its sign being opposite to that one of a sublinear redox reaction (0<β<1). This enhanced performance of our double-step voltcoulometry is documented by a series of experiments on aqueous solutions of ascorbic acid using a carbon fiber microelectrode as the working electrode. Finally, how to assess the degree of reversibility of the redox reaction and deduce the time constant RC of the double-layer charging current is shown.
Magnetic background noise cancellation in real-world environments
Authors: Wöltgens P. J. M. , Koch R. H.
Published: July 2002

Measurements of the magnetic field noise and the spatial correlation of the noise were made in a typical laboratory environment using two three-axis fluxgate magnetometers. The magnitude of the magnetic field noise was found to be approximately 100 pT/Hz at 10 Hz with a correlation of 90% at a separation of 1 m between the two sensors. The correlation was significantly reduced from noise induced eddy currents near large metallic surfaces.
Time resolved blue and ultraviolet photoluminescence in porous GaP
Authors: Anedda A. , Serpi A. , Karavanskii V. A. , Tiginyanu I. M. , Ichizli V. M.
Published: July 2002

Porous GaP layers prepared by electrochemical anodization of (100)-oriented bulk material was found to exhibit blue and ultraviolet photoluminescence when excited by a KrF excimer laser. The energy position of the UV luminescence band (3.3 eV at 300 K) is explained on the basis of charge carrier confinement in crystalline quantum wires of about 25 Å in diameter. Additional evidence for quantum size effect in porous GaP was obtained by Raman scattering measurements.
Observation of a negative electron affinity for boron nitride
Authors: Powers M. J. , Benjamin M. C. , Porter L. M. , Nemanich R. J. , Davis R. F. , Cuomo J. J. , Doll G. L. , Harris Stephen J.
Published: July 2002

This study reports UV-photoemission (UPS) measurements made on boron nitride crystals and thin films. The materials examined are commercial grade c-BN powder and thin films of BN deposited with ion beam assisted e-beam evaporation and laser ablation. The thin film samples examined exhibited varying amounts of sp3 (cubic) and sp2 (hexagonal, amorphous) bonding as determined by FTIR measurements. The UPS measurements displayed the spectral distribution of the low energy photoemitted electrons and the total energy width of the spectra. These characteristics can be related to the electron affinity. The measurements on several of the BN powder and thin film samples revealed features in the emission spectra which are indicative of a negative electron affinity (NEA) surface.
X-ray Fraunhofer diffraction patterns from a thin-film waveguide
Authors: Feng Y. P. , Sinha S. K. , Fullerton Eric E. , Grübel G. , Abernathy D. , Siddons D. P. , Hastings J. B.
Published: July 2002

We have observed the Fraunhofer diffraction pattern of x-rays exiting from the end face of a SiO2/polyimide/Si thin-film waveguide. The measured angular intensity distributions are in excellent agreement with those calculated based on the dimensions and the refractive index profile of the guide. Our measurement confirms that, at the end face of the guide, the wavefront of a single guided mode is fully coherent in the direction normal to the guiding plane. This focused and transversely coherent x-ray beam may be used as a source for coherence-based experiments, such as x-ray photon correlation spectroscopy.
Ultrahigh resolution of calixarene negative resist in electron beam lithography
Authors: Fujita J. , Ohnishi Y. , Ochiai Y. , Matsui S.
Published: July 2002

A nonpolymer material, calixarene derivative (hexaacetate p-methnylcalix[6]arene) was tested as a high-resolution negative resist under an electron beam lithography process. It showed under 10-mm resolution with little side roughness and high durability to halide plasma etching. A sub-10-nm Ge quantum wire was perfectly etched off without defects. Such a performance is suitable for nanoscale device processes.
Superconductivity above 130 K in high-quality mercury-based cuprate thin films
Authors: Yun S. H. , Wu J. Z.
Published: July 2002

Superconductivity above 130 K has been achieved in c-axis-oriented HgBa2Ca2Cu3O8+δ thin films. At 5 K, the superconducting critical current density (Jc) of the film is 23 MA/cm2 in the absence of magnetic field and above 2 MA/cm2 in 5 T magnetic field with the field along the c axis. A zero field Jc of 0.5 MA/cm2 is maintained to temperatures over 100 K, which indicates that the mercury-based cuprate thin films are promising for applications of superconducting electronic devices operating at above 100 K.
Epitaxial HgBa2Ca2Cu3Oy films on SrTiO3 substrates prepared by spray pyrolysis technique
Authors: Moriwaki Y. , Sugano T. , Gasser C. , Fukuoka A. , Nakanishi K. , Adachi S. , Tanabe K.
Published: July 2002

HgBa2Ca2Cu3Oy (Hg-1223) films with a thickness of 1–2 μm and Tc (zero)∼130 K have been fabricated by utilizing a spray pyrolysis technique. X-ray diffraction indicates that the films consist of predominantly Hg-1223 phase grains with c-axis orientation. Moreover, the oscillation photograph taken by a Weissenberg camera confirms that the film grains are in-plane aligned and epitaxially grown on SrTiO3. In electrical transport measurements, the as-fabricated film exhibits a Tc (zero) of 123 K, and a zero-field Jc of 3.7×105 A/cm2 at 77 K. Additional post-annealing at 320 °C for 50 h in flowing oxygen has improved the transport properties as Tc (zero)∼130 K and Jc∼4.4×105 A/cm2 (77 K, 0 T).
Intrinsic optical properties of GaN epilayers grown on SiC substrates: Effect of the built-in strain
Authors: Buyanova I. A. , Bergman J. P. , Monemar B. , Amano H. , Akasaki I.
Published: July 2002

Intrinsic excitonic properties of GaN/SiC epilayers are studied by photoluminescence and reflectance spectroscopies. The residual built-in tensional biaxial strain, induced by the SiC substrate, is suggested to be responsible for the observed downshift of the excitonic band gap and the reduced valence band splitting in comparison with bulk strain-free GaN samples. By comparing the temperature dependence of the free exciton transition energies for bulk GaN, GaN/SiC, and GaN/Al2O3 samples, residual stress is shown to affect the temperature dependence of the excitonic band-gap energy.
Reduction of the thermal impedance of vertical-cavity surface-emitting lasers after integration with copper substrates
Authors: Mathine D. L. , Nejad H. , Allee D. R. , Droopad R. , Maracas G. N.
Published: July 2002

Vertical-cavity surface-emitting lasers (VCSELs) have been transferred from their original GaAs substrates to Cu substrates and continuous wave operation has been obtained on the VCSELs after epitaxial transfer. The resultant measurements show a doubling of the output power and a 20% reduction in the thermal impedance. Increased optical power is explained by improved thermal heat sinking as measured from the lasing spectra of horizontal-cavity edge-emitting lasers fabricated from the same VCSEL material.
High critical current densities of YBa2Cu3O7−x thin films on buffered technical substrates
Authors: Knierim A. , Auer R. , Geerk J. , Linker G. , Meyer O. , Reiner H. , Schneider R.
Published: July 2002

C -axis oriented YBa2Cu3O7−x (YBCO) thin films were deposited on polycrystalline metallic tapes buffered with yttria stabilized zirconia (YSZ). The in-plane alignment of the YSZ layers achieved by simultaneous ion bombardment of the growing film (ion beam assisted deposition) and of the postdeposited YBCO thin films was studied by x-ray diffraction as a function of the buffer layer thickness. A significant improvement of the in-plane texture, achieved for buffer layers exceeding a thickness of about 1.5 μm, resulted in high critical current densities above 106 A/cm2 of the YBCO films.