Photocurrents in P3MeT Schottky barrier diodes

The photocurrent action spectrum of a Schottky diode formed from electrodeposited poly(3-methylthiophene) is shown to follow closely the UV-visible absorption spectrum. At low forward bias, the peak photocurrent asymptotes to the expected square-root dependence on total potential, V-t, across the depletion region. At high reverse bias the superlinear dependence of the photocurrent on V-t suggests that internal photoemission from the rectifying aluminium electrode may be the dominant process.

Electrical AC behaviour of MPCVD diamond Schottky diodes

The present work reports some experimental results on the electrical AC behaviour of metal-undoped diamond Schottky diodes fabricated with a free-standing MPCVD diamond film (5 mum thick). The metals are gold for the ohmic contact and aluminium for the rectifier. The capacitance and loss tangent vs, frequency shows that capacitance presents a relaxation maximum at frequencies near 10 kHz at room temperature. Although the simple model (small equivalent circuit) can justify the values for the relaxation, it cannot justify the departure from the Debye model, also verified in the Cole-Cole plot. Taking into account the existence of traps in the depletion region, a best fit to the experimental results was obtained. The difference between the Fermi level and the band edge of 0.2-0.3 eV is in agreement with the activation energy found from the loss tangent analysis. The capacitance with applied voltage (Mott-Schottky plots) gives a defect density of 10(16) cm(-3) with contact potentials near 0.5 V and the profile of defect density obtained shows a major density (approx. 10(17) cm(-3)) in a layer with a thickness less than 50 nm from the junction, decreasing by one order of magnitude with increasing distance. Finally a structural model is proposed to explain the AC behaviour found. (C) 2001 Elsevier Science B.V. All rights reserved.

Schottky barrier diodes from semiconducting polymers

Schottky barrier diodes based on Al/poly(3-methylthiophene)/Au have been fabricated and their electrical behaviour investigated. I-V characteristics revealed a dependence on the fabrication conditions, specifically on the time under vacuum prior to evaporation of the rectifying contact and post-metal annealing at elevated temperature. The available evidence is consistent with the formation of a thin insulating layer between the metal and the polymer following these procedures. Long periods under vacuum prior to deposition of the aluminium electrode reduced the likelihood of such a layer forming. Capacitance-voltage plots of the devices were stable to voltage cycling, so long as the forward voltage did not exceed similar to 1 V. Above this a small degree of hysteresis was observed, which is attributed to the filling/emptying of interface states or traps in the polymer.

Evaluación de la función renal en pacientes con enfermedad renal crónica (ERC) sin tratamiento sustitutorio, tras un programa de intervención nutricional (PIN): estudio aleatorizado

La Enfermedad Renal Crónica (ERC) se define como la disminución de la función renal, donde se reduce el filtrado glomerular (FG) estimado < 60 ml/min/1,73m2 o como la presencia de daño renal de forma persistente durante al menos tres meses. La enfermedad renal crónica (ERC) es una patología progresiva que afecta cada vez más a la población, el daño renal aumenta con el paso del tiempo, siendo su resultado el tratamiento renal sustitutivo, trasplante o incluso la muerte, el gran problema es que en ocasiones no hay síntomas hasta que esta instaurada. Las causas de la ERC son complejas e incluyen enfermedades comunes, como la hipertensión, el síndrome metabólico (conjunto de varios factores como HTA, obesidad), la diabetes y otras patologías que afectan al riñón. Desde la clasificación de ERC en 5 fases, los clínicos pueden diagnosticar precozmente, incluso en estadios iniciales. Para frenar la progresión de la enfermedad es recomendable la disminución de ingesta de proteica. El objetivo de este estudio es evaluar una intervención nutricional (PIN) sobre la función renal, valorando la ingesta, vigilando el estado renal y nutricional en pacientes con enfermedad renal crónica sin tratamiento sustitutorio. Se siguieron los criterios de las quías KDIGO/KDOQI, y los diferentes Documentos de Consenso de las Sociedades Científicas. Se diseñó un estudio longitudinal aleatorizado de 86 participantes, de los 43 que componían el grupo estudio (E) finalizaron el programa de intervención nutricional 90,69% de la muestra inicial, y 38 de los participantes del grupo control (C) (88,37%). La duración del ensayo fue de 12 meses. El estado nutricional se evaluó mediante la valoración global subjetiva (VSG), datos antropométricos, dietéticos y analíticos. Se realizó los análisis estadísticos con el programa SPSS. A los doce meses, se ha observado un aumento de FG y una disminución de otros parámetros que agravan la enfermedad. Además, se ha producido un control de la ingesta proteica y de la ingesta energética. Conclusión: Mediante una intervención nutricional mantenida en el tiempo, se puede controlar el estado nutricional y se evita la progresión de la enfermedad renal, influyendo positivamente en algunos parámetros de riesgo. Por lo que podemos concluir que la utilización de programas de intervención nutricional (PIN) en las consultas de enfermería nefrológica para pacientes con enfermedad renal crónica, podría evitar, en ocasiones, el paso del paciente a diálisis, trasplante o a la muerte.

High bandwidth freestanding semipolar (11–22) InGaN/GaN light-emitting diodes

Freestanding semipolar (11–22) indium gallium nitride (InGaN) multiplequantum-well light-emitting diodes (LEDs) emitting at 445 nm have been realized by the use of laser lift-off (LLO) of the LEDs from a 50- m-thick GaN layer grown on a patterned (10–12) r -plane sapphire substrate (PSS). The GaN grooves originating from the growth on PSS were removed by chemical mechanical polishing. The 300 m × 300 m LEDs showed a turn-on voltage of 3.6 V and an output power through the smooth substrate of 0.87 mW at 20 mA. The electroluminescence spectrum of LEDs before and after LLO showed a stronger emission intensity along the [11–23]InGaN/GaN direction. The polarization anisotropy is independent of the GaN grooves, with a measured value of 0.14. The bandwidth of the LEDs is in excess of 150 MHz at 20 mA, and back-to-back transmission of 300 Mbps is demonstrated, making these devices suitable for visible light communication (VLC) applications.

Computational characterization of carbazole-benzonitrile derivatives for applications in Organic Light Emitting Diodes

The technology of Organic Light-Emitting Diodes has reached such a high level of reliability that it can be used in various applications. The required light emission efficiency can be achieved by transforming the triplet excitons into singlet states through Reverse InterSystem Crossing (RISC), which is the main process of a general mechanism called thermally activated delayed fluorescence (TADF). In this thesis, we theoretically analyzed two carbazole-benzonitrile (donor-acceptor) derivatives, 2,5-di(9H-carbazol-9-yl)benzonitrile (p-2CzBN) and 2,3,4,5,6-penta(9H-carbazol-9-yl)benzonitrile (5CzBN), and addressed the problem of how donor-acceptor (D-A) or donor-acceptor-donor (D-A-D) flexible molecular architectures influence the nature of the excited states and the emission intensity. Furthermore, we analyzed the RISC rates as a function of the conformation of the carbazole lateral groups, considering the first electronic states, S0, S1, T1 and T2, involved in TADF process. The two prototype molecules, p-2CzBN and 5CzBN, have a similar energy gap between the first singlet and triplet states (∆EST, a key parameter in the RISC rate), but different TADF performances. Therefore, other parameters must be considered to explain their different behavior. The oscillator strength of p-2CzBN, never tested as emitter in OLEDs, is similar to that of 5CzBN, which is an active TADF molecule. We also note that the presence of a second T2 triplet state, lower in energy than S1 only in 5CzBN, and the reorganization energies, associated with RISC processes involving T1 and T2, are important factors in differentiating the rates in p-2CzBN and 5CzBN. For p-2CzBN, the RISC rate from T2 to S1 is surprisingly higher than that from T1 to S1, in disagreement with El-Sayed rules, due to a large reorganization energy associated to the T1 to S1, process; while the contrary occurs for 5CzBN. These insights are important for designing new TADF emitters based on the benzo-carbazole architecture.

Models and Simulations of Diamond-like Carbon for large-area high voltage power diodes

Silicon-based discrete high-power devices need to be designed with optimal performance up to several thousand volts and amperes to reach power ratings ranging from few kWs to beyond the 1 GW mark. To this purpose, a key element is the improvement of the junction termination (JT) since it allows to drastically reduce surface electric field peaks which may lead to an earlier device failure. This thesis will be mostly focused on the negative bevel termination which from several years constitutes a standard processing step in bipolar production lines. A simple methodology to realize its counterpart, a planar JT with variation of the lateral doping concentration (VLD) will be also described. On the JT a thin layer of a semi insulating material is usually deposited, which acts as passivation layer reducing the interface defects and contributing to increase the device reliability. A thorough understanding of how the passivation layer properties affect the breakdown voltage and the leakage current of a fast-recovery diode is fundamental to preserve the ideal termination effect and provide a stable blocking capability. More recently, amorphous carbon, also called diamond-like carbon (DLC), has been used as a robust surface passivation material. By using a commercial TCAD tool, a detailed physical explanation of DLC electrostatic and transport properties has been provided. The proposed approach is able to predict the breakdown voltage and the leakage current of a negative beveled power diode passivated with DLC as confirmed by the successfully validation against the available experiments. In addition, the VLD JT proposed to overcome the limitation of the negative bevel architecture has been simulated showing a breakdown voltage very close to the ideal one with a much smaller area consumption. Finally, the effect of a low junction depth on the formation of current filaments has been analyzed by performing reverse-recovery simulations.

Profile Of Phenolic Compounds Of Brazilian Virgin Olive Oils By Rapid Resolution Liquid Chromatography Coupled To Electrospray Ionisation Time-of-flight Mass Spectrometry (rrlc-esi-tof-ms).

In recent years, agronomical researchers began to cultivate several olive varieties in different regions of Brazil to produce virgin olive oil (VOO). Because there has been no reported data regarding the phenolic profile of the first Brazilian VOO, the aim of this work was to determine phenolic contents of these samples using rapid-resolution liquid chromatography coupled to electrospray ionisation time-of-flight mass spectrometry. 25 VOO samples from Arbequina, Koroneiki, Arbosana, Grappolo, Manzanilla, Coratina, Frantoio and MGS Mariense varieties from three different Brazilian states and two crops were analysed. It was possible to quantify 19 phenolic compounds belonging to different classes. The results indicated that Brazilian VOOs have high total phenolic content because the values were comparable with those from high-quality VOOs produced in other countries. VOOs from Coratina, Arbosana and Grappolo presented the highest total phenolic content. These data will be useful in the development and improvement of Brazilian VOO.

Resultados preliminares de um sistema de topografia de grande-ângulo usando videoceratógrafo com discos de Plácido

OBJETIVO: Desenvolver a instrumentação e o "software" para topografia de córnea de grande-ângulo usando o tradicional disco de Plácido. O objetivo é permitir o mapeamento de uma região maior da córnea para topógrafos de córnea que usem a técnica de Plácido, fazendo-se uma adaptação simples na mira. MÉTODOS: Utilizando o tradicional disco de Plácido de um topógrafo de córnea tradicional, 9 LEDs (Light Emitting Diodes) foram adaptados no anteparo cônico para que o paciente voluntário pudesse fixar o olhar em diferentes direções. Para cada direção imagens de Plácido foram digitalizadas e processadas para formar, por meio de algoritmo envolvendo elementos sofisticados de computação gráfica, um mapa tridimensional completo da córnea toda. RESULTADOS: Resultados apresentados neste trabalho mostram que uma região de até 100% maior pode ser mapeada usando esta técnica, permitindo que o clínico mapeie até próximo ao limbo da córnea. São apresentados aqui os resultados para uma superfície esférica de calibração e também para uma córnea in vivo com alto grau de astigmatismo, mostrando a curvatura e elevação. CONCLUSÃO: Acredita-se que esta nova técnica pode propiciar a melhoria de alguns processos, como por exemplo: adaptação de lentes de contato, algoritmos para ablações costumizadas para hipermetropia, entre outros.

Africanized honey bees are efficient at detecting, uncapping and removing dead brood

The hygienic behavior of honey bees is based on a two-step process, including uncapping and removing diseased, dead, damaged, or parasitized brood inside the cell. We evaluated during periods of 1 h the time that hygienic and non-hygienic colonies of Africanized honey bees spend to detect, uncap and remove pin-killed brood using comb inserts with transparent walls placed in observation hives. We observed that hygienic colonies are significantly faster in detecting, uncapping and removing dead brood in the cells (P < 0.001).

Sequential hygienic behavior in Carniolan honey bees (Apis mellifera carnica)

We examined the sequence, order or steps of hygienic behavior (HB) from pin-killed pupae until the removal of them by the bees. We conducted our study with four colonies of Apis mellifera carnica in Germany and made four repetitions. The pin-killing method was used for evaluation of the HB of bees. The data were collected every 2 h after perforation, totaling 13 observations. Additionally, for one hygienic colony and another non-hygienic colony, individual analyses of each dead pupa were made at every observation, including all details, steps or sequences of HB. The bees recognize the cells containing dead pupae within 2 h after perforation, initially making a hole in the capping, which is the beginning of HB. Uncapping of the dead brood cell reached maximum values from 4 to 6 h after perforation; after 24 h, practically all cells were already uncapped. Another variable, called brood partially removed, was analyzed 4 h after perforation, after the cells had been perforated, which involved uncapping, followed by partial or total removal of the brood. Maximum values of brood partially removed were found 10 h after perforation, though such cells could be found up to 48 h after perforation. The most frequent sequence of events in both colonies was: capped cell -> punctured cell. brood partially removed -> empty cell. A new model of three pairs of recessive genes (uncapping u1, u2 and remover r) was proposed in order to explain the genetic control of the HB in Apis mellifera. We recommend evaluating HB 24 h after perforation and using a correction factor to compensate for control removal levels. We found a series of details of HB, which allow a study of how various factors may affect the sequence of the activities involved in HB and investigation of the genetics that controls this process.

Comparative study of the hygienic behavior of Carniolan and Africanized honey bees directed towards grouped versus isolated dead brood cells

In Apis mellifera, hygienic behavior involves recognition and removal of sick, damaged or dead brood from capped cells. We investigated whether bees react in the same way to grouped versus isolated damaged capped brood cells. Three colonies of wild-type Africanized honey bees and three colonies of Carniolan honey bees were used for this investigation. Capped worker brood cells aged 12 to 14 days old were perforated with the pin-killing method. After making holes in the brood cells, the combs were placed back into the hives; 24 h later the number of cleaned cells was recorded in areas with pin-killed and control brood cells. Four repetitions were made in each colony. Isolated cells were more frequently cleaned than grouped cells, though variance analysis showed no significant difference (P = 0.1421). Carniolan bees also were somewhat, though not significantly more hygienic than Africanized honey bees (P = 0.0840). We conclude that honey bees can detect and remove both isolated and grouped dead brood. The tendency towards greater hygienic efficiency directed towards grouped pin-killed brood may be a consequence of a greater concentration of volatiles emanating from the wounds in the dead pupae.

LED Phototherapy to Prevent Mucositis: A Case Report

Objective: The purpose of this case report was to evaluate the efficacy of phototherapy using light-emitting diodes (LEDs) to prevent oral mucositis in a Hodgkin's disease patient treated with the ABVD ( doxorubicin [Adriamycin], bleomycin, vinblastine, and dacarbazine) chemotherapy regimen. Background Data: Mucositis is a common dose-limiting complication of cancer treatment, and if severe it can lead to alterations in treatment planning or suspension of cancer therapy, with serious consequences for tumor response and survival. Therefore, low-power lasers and more recently LEDs, have been used for oral mucositis prevention and management, with good results. Materials and Methods: In this study, a 34-year-old man received intraoral irradiation with an infrared LED array (880 nm, 3.6 J/cm(2), 74 mW) for five consecutive days, starting on chemotherapy day 1. In each chemotherapy cycle, he received the ABVD protocol on days 1 and 15, and received LED treatment for 5 d during each cycle. To analyze the results, the World Health Organization (WHO) scale was used to grade his mucositis, and a visual analogue scale (VAS) was used for pain evaluation, on days 1, 3, 7, 10, and 13 post-chemotherapy. Results: The results showed that the patient did not develop oral mucositis during the five chemotherapy cycles, and he had no pain symptoms. Conclusion: LED therapy was a safe and effective method for preventing oral mucositis in this case report. However, further randomized studies with more patients are needed to prove the efficacy of this method.

Hygienic behavior of the stingless bee Plebeia remota (Holmberg, 1903) (Apidae, Meliponini)

We investigated hygienic behavior in 10 colonies of Plebeia remota, using the pin-killed method. After 24 h the bees had removed a mean of 69.6% of the dead brood. After 48 h, the bees had removed a mean of 96.4% of the dead brood. No significant correlation was found between the size of the brood comb and the number of dead pupae removed, and there was no apparent effect of the origin and the condition of the colony on the hygienic behavior of the bees. Plebeia remota has an efficiency of hygienic behavior superior to that of three of the other four stingless bee species studied until now.