886 resultados para Resonant Frequency.


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Strongyloidiasis is a disease of emerging public health importance. A survey was conducted in Araraquara city, São Paulo state, Brazil, in order to evaluate the frequency distribution of Strongyloides stercoralis in the area. A total of 9582 single stool samples were examined by direct examination, and by the Coprotest and Rugai's methods from January 2005 to January 2007. Out of the total samples examined, 408 (4,3%) were found to be infected by S. stercoralis (143 men and 265 women). The months with the highest frequency (5,0 - 8,2%) of positive patients were February, September and December (2005); April and November (2006) and January (2007). The frequencies from the other months varied around 2,5 to 4,9%. It was concluded that strongyloidiasis is endemic in Araraquara, but in some months, which presented the highest temperatures followed by rainy periods, the frequencies are typical from hyperendemic areas.

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Blastocystis hominis é um protozoário, causador de infecção intestinal denominada blastocistose humana, cujo diagnóstico é realizado pelo exame coproparasitológico e por meio de técnicas de coloração permanente. Este estudo foi desenvolvido para avaliar a freqüência da infecção por Blastocystis hominis em habitantes da região de Araraquara/SP, bem como comparar diferentes métodos para a pesquisa desse protozoário em amostras de fezes. Foram estudadas 503 amostras de fezes submetidas ao exame direto a fresco, às técnicas de Faust e cols, Lutz e de Rugai e cols, além das colorações pela hematoxilina férrica, tricrômio e de Kinyoun modificada. Entre as 503 amostras examinadas, 174 (34,6%) apresentaram-se positivas para a presença de parasitas intestinais. O protozoário e o helminto mais freqüentes foram Entamoeba coli (14,6%) e Strongyloides stercoralis (6,7%), respectivamente. Blastocystis hominis foi observado em 23 (4,6%) amostras fecais com consistência predominantemente pastosa, não caracterizando quadro diarréico. Apesar da baixa freqüência de Blastocystis hominis encontrada na região de Araraquara, comparativamente a outras regiões brasileiras, é importante a realização do diagnóstico laboratorial desse protozoário. O encontro de Blastocystis hominis em material fecal é indicativo de contaminação de alimentos e água de consumo, desde que se admita a rota de transmissão oral-fecal desse parasita, o que implica na orientação da população sobre as medidas de saneamento básico e higiene como meio para se controlar problemas de saúde ocasionados pelos enteroparasitas.

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O objetivo deste estudo foi avaliar a presença de aloanticorpos anti-HLA classe I em pacientes infectados pelo HIV-1 e relacioná-la aos diferentes cursos clínicos da doença. Amostras de sangue de 145 indivíduos HIV positivo foram coletadas em tubos com EDTA. A infecção pelo HIV-1 foi confirmada por teste ELISA e a presença de aloanticorpos anti-HLA classe I determinada em seguida. A evolução clínica foi definida como rápida (<1 ano entre diagnóstico e morte), moderada (1-3 anos) ou lenta (>3 anos). A presença de aloanticorpos anti-HLA classe I foi menor em indivíduos saudáveis em relação aos infectados pelo HIV-1 (4,2% contra 32,4%). Porém, a distribuição destes aloanticorpos entre os indivíduos infectados foi igual, independente da evolução clínica. Deste modo, a presença de aloanticorpos anti-HLA classe I não é um fator determinante na piora clínica do paciente.

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The effect of manganese on the vibrational properties of Ga(1-x)Mn(x)N (0 <= x <= 0.18) films has been investigated by Raman scattering using 488.0 and 632.8 nm photon excitations. The first-order transverse and longitudinal optical GaN vibrational bands were observed in the whole composition range using both excitations, while the corresponding overtones, as well as a prominent peak located in 1238 cm(-1) (153.5 meV) were only observed in the Mn-containing films under 488.0 nm excitation. We propose that the peak observed at 1238 cm(-1) is due to resonant Mn local vibrational modes, the excitation process being related to electronic transitions involving the Mn acceptor band.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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This paper presents an analysis of a novel pulse-width-modulated (PWM) voltage step-down/up Zeta converter, featuring zero-current-switching (ZCS) at the active switches. The applications in de to de and ac to de (rectifier) operation modes are used as examples to illustrate the performance of this new ZCS-PWM Zeta converter. Regarding to the new ZCS-PWM Zeta rectifier proposed, it should be noticed that the average-current mode control is used in order to obtain a structure with high power-factor (HPF) and low total harmonic distortion (THD) at the input current.Two active switches (main and auxiliary transistors), two diodes, two small resonant inductors and one small resonant capacitor compose the novel ZCS-PWM soft-commutation cell, used in these new ZCS-PWM Zeta converters. In this cell, the turn-on of the active switches occurs in zero-current (ZC) and their turn-off in zero-current and zero-voltage (ZCZV). For the diodes, their turn-on process occurs in zero-voltage (ZV) and their reverse-recovery effects over the active switches are negligible. These characteristics make this cell suitable for Insulated-Gate Bipolar Transistors (IGBTs) applications.The main advantages of these new Zeta converters, generated from the new soft-commutation cell proposed, are possibility of obtaining isolation (through their accumulation inductors), and high efficiency, at wide load range. In addition, for the rectifier application, a high power factor and low THD in the input current ran be obtained, in agreement with LEC 1000-3-2 standards.The principle of operation, the theoretical analysis and a design example for the new de to de Zeta converter operating in voltage step-down mode are presented. Experimental results are obtained from a test unit with 500W output power, 110V(dc) output voltage, 220V(dc) input voltage, operating at 50kHz switching frequency. The efficiency measured at rated toad is equal to 97.3%for this new Zeta converter.Finally, the new Zeta rectifier is analyzed, and experimental results from a test unit rated at 500W output power, 110V(dc) output voltage, 220V(rms) input voltage, and operating at 50kHz switching frequency, are presented. The measured efficiency is equal to 96.95%, the power-factor is equal to 0.98, and the input current THD is equal to 19.07%, for this new rectifier operating at rated load.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The search for better performance in the structural systems has been taken to more refined models, involving the analysis of a growing number of details, which should be correctly formulated aiming at defining a representative model of the real system. Representative models demand a great detailing of the project and search for new techniques of evaluation and analysis. Model updating is one of this technologies, it can be used to improve the predictive capabilities of computer-based models. This paper presents a FRF-based finite element model updating procedure whose the updating variables are physical parameters of the model. It includes the damping effects in the updating procedure assuming proportional and none proportional damping mechanism. The updating parameters are defined at an element level or macro regions of the model. So, the parameters are adjusted locally, facilitating the physical interpretation of the adjusting of the model. Different tests for simulated and experimental data are discussed aiming at defining the characteristics and potentialities of the methodology.

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The research trend for harvesting energy from the ambient vibration sources has moved from using a linear resonant generator to a non-linear generator in order to improve on the performance of a linear generator; for example, the relatively small bandwidth, intolerance to mistune and the suitability of the device for low-frequency applications. This article presents experimental results to illustrate the dynamic behaviour of a dual-mode non-linear energy-harvesting device operating in hardening and bi-stable modes under harmonic excitation. The device is able to change from one mode to another by altering the negative magnetic stiffness by adjusting the separation gap between the magnets and the iron core. Results for the device operating in both modes are presented. They show that there is a larger bandwidth for the device operating in the hardening mode compared to the equivalent linear device. However, the maximum power transfer theory is less applicable for the hardening mode due to occurrence of the maximum power at different frequencies, which depends on the non-linearity and the damping in the system. The results for the bi-stable mode show that the device is insensitive to a range of excitation frequencies depending upon the input level, damping and non-linearity.

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This paper investigates the feasibility of using an energy harvesting device tuned such that its natural frequency coincides with higher harmonics of the input to capture energy from walking or running human motion more efficiently. The paper starts by reviewing the concept of a linear resonant generator for a tonal frequency input and then derives an expression for the power harvested for an input with several harmonics. The amount of power harvested is estimated numerically using measured data from human subjects. Assuming that the input is periodic, the signal is reconstructed using a Fourier series before being used in the simulation. It is found that although the power output depends on the input frequency, the choice of tuning the natural frequency of the device to coincide with a particular higher harmonic is restricted by the amount of damping that is needed to maximize the amount of power harvested, as well as to comply with the size limit of the device. It is also found that it is not feasible to tune the device to match the first few harmonics when the size of the device is small, because a large amount of damping is required to limit the motion of the mass.

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Study Objectives: To study endotracheal tube (ETT) cuff pressures during nitrous oxide (N2O) anesthesia when the cuffs are inflated with air to achieve sealing pressure, and to evaluate the frequency of postoperative laryngotracheal complaints.Design: Prospective, randomized, blind study.Setting: Metropolitan teaching hospital.Patients: 50 ASA physical status I and II patients scheduled for elective abdominal surgery.Interventions: Patients received standard general anesthesia with 66% N2O in oxygen. In 25 patients, the ETT cuff was inflated with air to achieve a sealing pressure (P-seal group). In 25 patients, the ETT cuff was inflated with air to achieve a pressure of 25 cm H2O (P-25 group).Measurements and Main Results: ETT intracuff pressures were recorded before (control) and at 30, 60, 90, 120, and 150 minutes during N2O administration. We investigated the frequency and intensity of sore throat, hoarseness, and dysphagia in patients in the Post-Anesthesia Care Unit (PACU) and 24 hours following tracheal extubation. The cuff pressures in the P-seal group were significantly lower than in the P-25 group at all time points studied (p < 0.001), with a significant increase with time in both groups (p < 0.001). The cuff pressures exceeded the critical pressure of 30 cm H2O only after 90 minutes in the P-seal group and already by 30 minutes in the P-25 group. The frequency and intensity of sore throat, hoarseness, and dysphagia were similar in both groups in the PACU and 24 hours after tracheal extubation (p > 0.05).Conclusions: Minimum ETT sealing cuff pressure during N2O anesthesia did not prevent, but instead attenuated, the increase in cuff pressure and did not decrease postoperative laryngotracheal complaints. (C) 2004 by Elsevier B.V.

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CONTEXTO: Mães relatam início precoce de constipação em crianças atendidas em clínicas de gastroenterologia. OBJETIVOS: Estudar o hábito intestinal em crianças de baixa idade na comunidade, para avaliar se início precoce da constipação é confirmado neste contexto e se há concordância entre o hábito intestinal relatado e o registrado prospectivamente. MÉTODOS: Obtiveram-se dados sobre evacuações de 57 crianças com idade 6.0-40.7 meses, mediante relato materno (questionário sobre características fecais predominantes) e, a seguir, foram registradas 1.934 evacuações em casa e na creche. O hábito intestinal foi classificado como adequado, constipação, diarréia funcional, outro hábito intestinal, conforme frequência evacuatória e proporção das características fecais (macias, duras e/ou que escorrem). Usaram-se dois critérios para classificar o hábito intestinal registrado, devido indefinição no ponto de corte para fezes duras na identificação de constipação em crianças: critério predominante e critério adulto, respectivamente com >50% e >25% de evacuações com consistência alterada. Usou-se estatística não-paramétrica e, para concordância entre hábito intestinal relatado e registrado, o índice Kappa. RESULTADOS: Constipação ocorreu em 17.5%, 10.5%, 19.3% das crianças, respectivamente pelo relato e pelo registro segundo critérios predominante e adulto. Constipação foi o hábito intestinal mais frequentemente relatado, versus 12.3% outro hábito intestinal. Só uma criança se classificou como tendo diarréia funcional (pelo critério adulto). Concordância entre o hábito intestinal relatado e o registrado foi razoável (fair) para constipação, pelos critérios predominante e adulto (K=0.28 e 0.24, respectivamente), mas apenas leve (slight) para os demais hábito intestinal (K <0.16). Entretanto, dados individuais indicaram melhor relação entre relato de constipação com o critério adulto do que com o critério predominante. CONCLUSÕES: Confirmou-se que constipação é frequente e de início precoce. Concordância razoável entre o hábito intestinal relatado e o registrado segundo os dois critérios indica que o relato materno é razoavelmente confiável para detectar constipação.

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Introduction and objectives: Catfish occur in marine and freshwater environments worldwide. They have three serrated venomous bony stings in the dorsal and pectoral fins that are used for defence against predators and are refilled by glandular tissues under the epithelium. However, some catfishes do not have poisonous glands next to the sting and cause traumatic wounds without poisoning. The objective of this study was to provide data for, and comment on, the epidemiological and clinical problems caused by marine catfish.Patients and methods: the authors have observed, followed and documented 127 injuries caused by marine catfish stings during different phases of the envenoming over a time period of 8 years at three points along the Western Atlantic Ocean coast.Results: the patients presented intense pain during the acute phase of envenoming and complications, such as bacterial and fungi infections and retention of bony fragments, in the later phase. Immersion of the affected extremity in hot water was used in about 20% of cases with excellent results.Discussion: Injuries caused by marine catfish are common (about 20% of injuries caused by marine animals in a series of more than 700 injuries recorded by the author) and cause intense pain and later complications. Immersion of the affected extremity in hot water results in improvement in the acute phase, but does not prevent the appearance of secondary infection or foreign body reactions. (c) 2006 Elsevier Ltd. All rights reserved.