Estudo e desenvolvimento de um modelo de análise de risco para Radiocirurgia intracraniana

Mundialmente, eventos relatados constituídos por incidentes e acidentes em radioterapia, tem aumentado ao longo dos últimos 25 anos e a maioria destes eventos são resultados de falha humana, além de terem ocorrido com maior frequência em centros sofisticados que utilizam alta tecnologia. Em radioterapia a Gestão da Qualidade necessita de uma abordagem prospectiva através de análise de risco. Esta abordagem é defendida por recentes publicações por ser atualmente uma urgência em virtude do expressivo número de acidentes ocorridos. Dada a complexidade do processo em radioterapia, a busca pela qualidade do tratamento de forma a garantir a segurança do paciente é um dos assuntos mais discutidos mundialmente. Embora apenas 14% dos centros de radioterapia no Brasil ofereçam tratamentos com a técnica de radiocirurgia intracranial (SRS), estudos relativos a qualidade do tratamento relacionada a segurança do paciente submetido à esta técnica, é de relevante importância, pois qualquer desvio da dose prescrita é considerado muito mais crítico que em outras modalidades de tratamento radioterápico, já que são utilizadas altas doses de radiação que em geral variam de 10 Gy a 40 Gy para lesões até 50 mm de diâmetro, que são aplicadas em uma única fração ou até cinco frações. Tendo em vista tais conhecimentos, o objetivo deste trabalho foi atender um novo paradigma de Gestão da Qualidade, através do desenvolvimento de um modelo de análise de risco e de um Índice de Qualidade para a SRS no Brasil, a partir da técnica de Mapa do Processo e FMEA utilizadas pelo TG 100/AAPM. O trabalho foi desenvolvido em três centros de radioterapia de referência em alta tecnologia, dois localizados no Rio de Janeiro e um em São Paulo. Um Mapa do Processo de SRS foi identificado em cada centro de radioterapia e em seguida foi aplicada a técnica FMEA para todos os subprocessos identificados no mapa. A partir dos valores de NPR obtidos pela FMEA foi realizado um ranqueamento dos modos de falha. Modos de falha com NPR ≥ 100 e S ≥ 7 foram escolhidos como prioridade para implementação de estratégias de segurança. A partir das pontuações do parâmetro S atribuídas na aplicação da FMEA foi criado o Índice de Severidade (IS) e um Índice de Qualidade (IQ) foi criado a partir de uma relação entre o NPR e o IS. O resultado deste estudo, indica que as estratégias de segurança sejam implementadas para os 10 primeiros modos de falha do ranking e uma reavaliação do processo deve ocorrer a cada 1 ano. É também indicado que o IQ obtenha uma melhora mínima de 9% após a reavaliação do processo. De forma geral, o estudo mostrou que a adoção da ferramenta FMEA juntamente com o IQ são de fato justificadas, por minimizar os riscos para o paciente, melhorando a qualidade do tratamento aprimorando a segurança, criando mecanismos que permitam a garantia de que a dose será entregue de forma precisa e exata, e consequentemente, aumentando as chances de cura ou do controle local com uma desejada qualidade de vida para estes pacientes.

Prawn culture and policy options: technology import and culture through fishermen vis a vis industry

Recent developments in aquaculture has created an awareness that prawn culture is a dollar spinner, in which industry can step in to earn foreign exchange by producing an expensive food iten which has a high market demand abroad. The Government has to take a policy decision whether the prawn culture should be done through small fishermen to improve their socio-economic condition or through private industry with the high technology input and predefined objectives of export trade. Perhaps a simultaneous operation of the two could be allowed best in the interest of India. Perhaps in the interest of quick development and adoption of high production technology, through fishermen organization, the development is encouraged through the implimentation of welfare and area development schemes. In some selected areas private industry may be encoureged to use high production technology to develop prawns.

Optically controlled quantum dot gated transistors with high on/off ratio

We report the design and fabrication of InAs quantum dot gated transistors, which are normally-on, where the channel current can be switched off by laser illumination. Laser light at 650 nm with a power of 850 pW switches the channel current from 5 mu A to 2 pA, resulting in an on/off ratio of more than 60 dB. The switch-off mechanism and carrier dynamics are analyzed with simulated band structure.

Fabrication of a Low-Loss SSC Using High-Dose Electron Beam Lithography Exposure With Negative PMMA Resist

A silicon-on-insulator optical fiber-to-waveguide spot-size converter (SSC) using Poly-MethylMethAcrylate (PMMA) is presented for integrated optical circuits. Unlike the conventional use of PMMA as a positive resist, it has been successfully used as a negative resist with high-dose electron exposure for the fabrication of ultrafine silicon wire waveguides. Additionally, this process is able to reduce the side-wall roughness, and substantially depresses the unwanted propagation loss. Exploiting this technology, the authors demonstrated that the SSC can improve coupling efficiency by as much as over 2.5 dB per coupling facet, compared with that of SSC fabricated with PMMA as a positive resist with the same dimension.

A Low-Voltage Silicon Light Emitting Device in Standard Salicide CMOS Technology

National Natural Science Foundation of China 60536030 60776024 60877035 90820002 National High-Technology Research and Development Program of China 2007AA04Z329 2007AA04Z254

High Al-content AlInGaN epilayers with different thicknesses grown on GaN/sapphire templates

We studied the structural and optical properties of high Al-content AlInGaN epilayers with different thicknesses grown on GaN/sapphire templates by metalorganic chemical vapor deposition (MOCVD). Direct evidences of the gradual evolution of the content of Al, Ga and In along the growth direction were obtained. When the film thickness was over a certain value, however, the AlInGaN epilayer with constant element contents began to form. These results were also supported by the blue shift and splitting of the photoluminescence (PL) peak. For the thinnest epilayer, the surface was featured with outcrops of threading dislocations (TDs) which suggested a spiral growth mode. With increase in thickness, step-flow growth mode and V-shaped pits were observed, and the steps terminated at the pits. (C) 2008 Elsevier B. V. All rights reserved.

High efficiency operation of butt joint line-defect-waveguide microlaser in two-dimensional photonic crystal slab

Butt joint line-defect-waveguide microlasers are demonstrated on photonic crystal slabs with airholes in a triangular lattice. Such microlaser is designed to increase the output power from the waveguide edge directly. The output power is remarkably enhanced to 214 times higher by introducing chirped structure in the output waveguide. The lasing mode operates in the linear dispersion region of the output waveguide so that the absorption loss due to the band-edge effect is reduced. The laser resonance is illustrated theoretically using the finite difference time domain method. A practical high power efficiency of 20% is obtained in this microlaser. (C) 2008 American Institute of Physics.

High-speed 2 x 2 silicon-based electro-optic switch with nanosecond switch time

A 2 x 2 electro-optic switch is experimentally demonstrated using the optical structure of a Mach-Zehnder interferometer (MZI) based on a submicron rib waveguide and the electrical structure of a PIN diode on silicon-on-insulator (SOI). The switch behaviour is achieved through the plasma dispersion effect of silicon. The device has a modulation arm of I mm in length and cross-section of 400 nmx340 nm. The measurement results show that the switch has a V pi L pi figure of merit of 0.145 V-cm and the extinction ratios of two output ports and cross talk are 40 dB, 28 dB and -28 dB, respectively. A 3 dB modulation bandwidth of 90 MHz and a switch time of 6.8 ns for the rise edge and 2.7 ns for the fall edge are also demonstrated.

Deep levels in high resistivity GaN detected by thermally stimulated luminescence and first-principles calculations

Thermally stimulated luminescence spectroscopy has been applied to study the deep centres in unintentionally doped high resistivity GaN epilayers grown by the metal organic chemical vapour deposition method on c-sapphire substrates. Two trap states with activation energies of 0.12 and 0.62 eV are evaluated from two luminescence peaks at 141.9 and 294.7 K in the luminescence curve. Our spectroscopy measurement, in combination with more accurate first-principles studies, provided insights into the microscopic origin of these levels. Our investigations suggest that the lower level at 0.12 eV might originate from C-N, which behaves as a hole trap state; the deeper level at 0.62 eV can be correlated with V-Ga that corresponds to the yellow luminescence band observed in low-temperature photoluminescence spectra.

High-performance evanescently-coupled uni-traveling-carrier photodiodes

A new evanescently-coupled uni-traveling-carrier photodiode (EC-UTC PD) based on a multimode diluted waveguide (MDW) structure is fabricated, analysed and characterized. Optical and electrical characteristics of the device are investigated. The excellent characteristics are demonstrated such as a responsivity of 0.36 A/W, a bandwidth of 11.5 GHz and a small-signal 1-dB compression current greater than 18 mA at 10 GHz. The saturation current is significantly improved compared with those of similar evanescently-coupled pin photodiodes. The radio frequency (RF) bandwidth can be further improved by eliminating RF losses induced by the cables, the probe and the bias tee between the photodiode and the spectrum analyzer.

Overall optimization of high-speed semiconductor laser modules

Based on the high frequency techniques such as frequency response measurement, equivalent circuit modeling and packaging parasitics compensation, a comprehensive optimization method for packaging high-speed semiconductor laser module is presented in this paper. The experiments show that the small-signal magnitude frequency response of the TO packaged laser module is superior to that of laser diode in frequencies, and the in-band flatness and the phase-frequency linearity are also improved significantly.

12 W high efficiency single frequency ring laser

Single-frequency output power of 12 W at 1064 nm is demonstrated. Pumped by a fiber-coupled diode laser, the Nd:YVO4 produces 58.6% of the slope efficiency with respect to absorbed pump power, and 52.7% of the optical-optical efficiency and nearly diffraction-limited output with a beam quality parameter of M-2 approximate to 1.11. To the best of our knowledge, this is the highest slope efficiency and optical-optical efficiency in single-frequency Nd:YVO4 ring laser. The slope efficiency of the single frequency laser is close to the limit of the efficiency. [GRAPHICS] output spectrum of the single-frequency Nd:YVO4 ring laser

LD side-pumped high beam quality passive Q-switched and mode-locked Nd:YAG laser based on SESAM

We report a LD side-pumped fundamental-mode (Mx(2) = 1.35 and My(2) = 1.27) passive Q-switched and mode-locked Nd:YAG laser based on a semiconductor saturable absorber mirror (SESAM). At a pump current of 12.5 A, the average output power of 5.68 W with 80 kHz repetition rate and 2 mu s pulse width of the Q-switched envelope was generated. The repetition rate of the mode-locked pulse within the Q-switched envelope of 88 MHz was achieved.