Spectrometric characterization of amorphous silicon PIN detectors

During the last years, much interest has been dedicated to the use of amorphous silicon PIN diodes as particle and radiation detectors for medical applications. This work presents the spectrometric characterization of PECVD high deposition rate diodes fabricated at our laboratory, with thickness up to 17.5 μm. Results show that the studied devices detect the Am^(241) alpha particles and the medical X-rays generated by a mammograph model Senographe 700T from General Electric. Possible reasons of the observed energy losses are discussed in the lest. Using the SRIM2000 program, the transit of 5.5 MeV alpha particles through a diode was simulated, determining the optimum thickness for these particles to deposit their energy in the intrinsic layer of the diode

Charge-based continuous model for long-channel Symmetric Double-Gate Junctionless Transistors

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EVALUATION OF ANTIMICROBIAL AND CYTOTOXIC ACTIVITIES OF PLANT EXTRACTS FROM SOUTHERN MINAS GERAIS CERRADO

The antimicrobial activity of plant hidroethanolic extracts on bacteria Gram positive, Gram negative, yeasts, Mycobacterium tuberculosis H37 and Mycobacterium bovis was evaluated by using the technique of Agar diffusion and microdilution in broth. Among the extracts evaluated by Agar diffusion, the extract of Bidens pilosa leaf presented the most expressive average of haloes of growth inhibition to the microorganisms, followed by the extract of B. pilosa flower, of Eugenia pyriformis' leaf and seed, of Plinia cauliflora leaf which statistically presented the same average of haloes inhibitory formation on bacteria Gram positive, Gram negative and yeasts. The extracts of Heliconia rostrata did not present activity. Mycobacterium tuberculosis H37 and Mycobacterium bovis (BCG) appeared resistant to all the extracts. The susceptibility profile of Candida albicans and Saccharomyces cerevisiae fungi were compared to one another and to the Gram positive Bacillus subtilis, Enterococcus faecalis and the Gram negative Salmonella typhimurium bacteria (p > 0.05). The evaluation of cytotoxicity was carried out on C6-36 larvae cells of the Aedes albopictus mosquito. The extracts of stem and flower of Heliconia rostrata, leaf and stem of Plinia cauliflora, seed of Anonna crassiflora and stem, flower and root of B. pilosa did not present toxicity in the analyzed concentrations. The highest rates of selectivity appeared in the extracts of stem of A. crassiflora and flower of B. pilosa to Staphylococcus aureus, presenting potential for future studies about a new drug development

Analysis and simulation of the post-breakdown leakage current in electrically stressed TiO2/SiO2 gate stacks

The post-breakdown leakage current in electrically stressed metal-oxide-semiconductor structures with thin stacked layers of titanium dioxide (TiO2) over silicon dioxide (SiO2) Was investigated. The samples were obtained by plasma oxidation at room temperature. Multiple dielectric breakdowns were induced by the application of successive high-field voltage ramps. The resulting current-voltage characteristics were simulated using an equivalent electrical circuit model consisting in a diode with series and parallel resistances, which is solved using the Lambert W function. We show that after the first breakdown event the current that flows through the non-damaged gate stack area may still play a major role in determining the shape of the post-breakdown current-voltage characteristic. Similarities and differences with previous studied systems are discussed. (C) 2008 Elsevier B.V. All rights reserved

Host and environment factors for exposure to poisons: a case-control study of preschool children in Thailand

Objective—To identify host and environment characteristics associated with poison exposure among preschool children in Thailand. Setting—A matched case-control study in 20 public hospitals in Khon Kaen province. Methods—Cases comprised 100 consecutive preschool children attending hospital between September 1997 and February 1999 because of reported exposure to a poison. Controls were three children matched by age, sex and area of residence to each case, who had never attended a hospital for this reason. Risk factors were elicited by interviewing the children's caregivers at their homes using a structured questionnaire and analyzed using conditional logistic regression. Results—Number of siblings, whether the child was "medicine eating" and "rushing to explore new objects", the child's activities while the caregiver was working during the daytime, the child's distance from the caregiver while the caregiver was working, whether the child was taken to a non-agricultural worksite, and the number of used containers around the residence, were all statistically significant in univariate analyses. However, when all significant variables were included in a multivariate model, only "medicine eating" and the number of used containers around the residence remained statistically significant. Conclusion—Attention to "medicine eating" and used containers through increased supervision could be a protective factor against poison exposure for these children. To reduce risk, caregivers should not refer to medicines as foods and used containers should be systematically collected for disposal or recycling

Initial synchronization procedure for UMTS-FDD mode in FPGA

An implementation in FPGA of an algorithm suited for initial synchronization in mobile terminals for UMTS-FDD has been considered. Since software realization requires large amounts of MIPS and memory, the proposal allows a physical realization of a hardware system saving area and power which are critical in mobile terminal

FD MOS SOI circuit to enhance the ratio of illuminated to dark current of a co-integrated a-Si : H photodiode

In this paper we first present the integration of amorphous silicon photodiodes with a fully depleted silicon on isolator (FD SOI) MOSFET circuit. Taking the advantage of the better subthreshold characteristic of FD SOI MOSFETs with respect to bulk devices, a very simple SOI circuit integrated with the amorphous silicon photodiode is presented to significantly improve the ratio of the circuit output current when the diode is illuminated to when it is not. The use of one additional reference source voltage to adjust the operating point of the photodiode, allows to obtain a very significant increase in this current ratio, much higher than what can be obtained using a simple diode. Circuit solutions used to amplify the diode current under illumination are usually more complicated and involve a capacitor or more transistors than the circuit we present. All the other properties of the photodetector, as its spectral characteristic and linear dependence of detection with light intensity are maintained. The circuit can also be used in conjunction with other circuits for further amplification and/or processing, (C) 2002 Elsevier Science Ltd. All rights reserved

New method for determination of harmonic distortion in SOI FD transistors

We present a new method for calculating the total harmonic distortion (THID) and the third harmonic distortion (HD3) of the output current-voltage characteristics of a semiconductor device. The method is based on the calculation of two functions which we call D and D3 and are based on a specific integration of the DC current-voltage characteristic of the device. In this paper we demonstrate that function D can be correlated with the THD and function D3 with the HD3, so that they can be determined in a much simpler way, with no need to use derivatives, Fourier coefficients or fast Fourier transforms. The new method is applied to calculate the harmonic distortion of a silicon-on-insulator (Sol) fully depleted (FD) MOS transistor in the triode regime to be used as an active resistor at the input of an operational amplifier in a MOSFET-C filter configuration. It is also demonstrated that the transistor I-DS-V-DS characteristics used in these calculations can be obtained from either measurements, analytical models or numerical simulations. (C) 2002 Elsevier Science Ltd. All rights reserved

A method to extract mobility degradation and total series resistance of fully-depleted SOI MOSFETs

Free-carrier mobility degradation in the channel and drain/source series resistance are two important parameters limiting the performance of MOS devices. In this paper, we present a method to extract these parameters from the drain current versus gate voltage characteristics of fully-depleted (FD) SOI MOSFETs operating in the saturation region. This method is developed based on an integration function which reduces errors associated with the extraction procedure and on the d.c. characteristics of MOS devices having several different channel lengths. Simulation results and measured data of FD SOI MOSFETs are used to test and verify the method developed