Growth of large-sized relaxor ferroelectric PZN-PT single crystals by modified flux growth method

A novel bottom-cooling high-temperature solution growth technique is developed for growing large-sized relaxor ferroelectric 0.91Pb(Zn1/3Nb2/3O3)-0.09PbTiO3 (PZN-PT) single crystals. During the growth, an inverse temperature gradient is maintained in the crucible base by flowing air at a controlled rate. This method restricts the number of spontaneously nucleated crystals at crucible bottom, reduces loss of volatile PbO component and favours the growth of large-sized PZN-PT single crystals. Large-sized PZN-PT single crystals of dimensions ~ 22x20x14 mm3 are reproducibly grown by the proposed method. The electrical characteristics of the PZN-PT wafers oriented along the , and directions are investigated. PZN-PT wafers oriented along the direction exhibited superior piezoelectric coefficient (d33) of ~ 2221 pm/V. The homogeneity of the physical parameters is analysed by preparing 10 elements with dimensions of ~5x2.5x2.5 mm3 which were cut from single wafer oriented along the direction. The ferro-, piezo- and dielectric characteristics of these wafers were found to be highly uniform with small standard deviation. The observation of d33 value with less than 2 % deviation from mean value confirms the growth of high quality PZN-PT single crystals.Comment: 16 pages, 7 figure

Infecções em dispositivos neurológicos implantáveis em crianças e adolescentes

OBJETIVO: Determinar a freqüência, as causas, o sítio específico e as manifestações clínicas e laboratoriais das infecções em crianças e adolescentes após a implantação de dispositivos neurológicos (DVP) no Hospital Governador João Alves Filho (Aracaju SE). MÉTODO: Estudo prospectivo, observacional, não controlado de 50 pacientes, submetidos a DVP (58 procedimentos), no período de janeiro de 2003 a outubro de 2004. RESULTADOS: Observaram-se taxas de infecção por procedimento de 27,6%, taxas de infecção de índice cirúrgico zero, 1 e 2 de 25,7% e 30,4%, respectivamente (NNIS-CDC). A infecção de sítio cirúrgico foi a principal complicação com 50% das infecções. CONCLUSÃO: Taxa de infecção por procedimento, paciente e índice de risco cirúrgico mostraram-se elevadas. Não houve significância estatística com relação à idade, etiologia da hidrocefalia, ao tipo de procedimento (derivação primária e reinserção), tempo de internação pré-operatória, duração da cirurgia, antibioticoprofilaxia, cateter SNC prévio e índice de risco cirúrgico. _________________________________________________________________________________________ ABSTRACT: OBJECTIVE: To determine frequency, etiology, site and clinical and laboratory findings of ventriculoperitoneal shunt (VPS) infections in children and adolescents with hydrocephalus managed in Hospital Governador João Alves Filho, Aracaju SE, Brazil. METHOD: A non-controlled prospective observational study comprising 50 patients that underwent VPS (58 procedures) from January/2003 to October/2004. RESULTS: Infection rate per procedure was 27.6%; surgical risk index (NNISS-CDC) 0 and 1-2 were 25.7% and 30.4% respectively; surgical site infection was the main complication with 50% of the cases. CONCLUSION: Infection rates per procedure, per patient, and per surgical risk index were high. No statistical differences were found related to the following: age, etiology of hydrocephalus, type of procedure, pre-operative length of stay, duration of procedure, antibiotic prophylaxis, previous central nervous system catheter, and surgical risk index

Ventriculoperitoneal shunt infections

Central nervous system (CNS) shunt infection is a cause of significant morbidity, causing shunt malfunction and chronic ill health. This study was carried out to evaluate the infection rate associated with CNS shunts, assess the frequency of the pathogens as well as their antibiotic sensitivity pattern aiming at suitable prophylaxis. A retrospective analysis of 226 CSF cerebrospinal fluid (CSF) shunt procedures sent for bacteriological work up over a period of one year and six months was undertaken. Laboratory diagnosis was established by subjecting the CSF to cell count, biochemical tests, bacteriological culture and antibiotic susceptibility test. Nine out of 226(3.98%) of the CSF samples were culture positive. Coagulase negative Staphylococcus   was the most common isolate accounting for 36.36%. Majority of the isolates were sensitive to the thirdgeneration cephalosporins and quinolones. The antibiotic sensitivity pattern suggests cephalosporins and quinolones to be a better choice of antibiotics either prophylactically or therapeutically, which may result in effective and rapid sterilisation of the CSF

Outbreak of acute viral hepatitis due to hepatitis E virus in Hyderabad

Purpose: A waterborne outbreak of viral hepatitis occurred in the old city of Hyderabad from March through August 2005. An attempt was made to study the outbreak clinically, serologically, and etiologically. Methods: Five hundred and forty-six clinically and biochemically documented cases were screened for the hepatotropic viral markers, hepatitis A, B, C, and E by the ELISA method. Their demographic characteristics and outcomes were analyzed. Point source contamination of the water supply with sewerage was identified. Result: Our data confirms hepatitis E as the major cause of the outbreak (78.57%). Occasionally, mixed infection of HEV-HAV (5.31%) or HEV-HBV (0.91%) was detected in the present series of acute viral hepatitis. Conclusions: HEV was confirmed as the major etiological agent in this outbreak that was transmitted by contaminated drinking water. The study highlights the importance of screening for both enterically transmitted hepatotropic viral markers as well as the parenterally transmitted hepatotropic viral markers during outbreaks of acute viral hepatitis