Prediction of dopant atom distribution on nanocrystals using thermodynamic arguments.

A theoretical approach aiming at the prediction of segregation of dopant atoms on nanocrystalline systems is discussed here. It considers the free energy minimization argument in order to provide the most likely dopant distribution as a function of the total doping level. For this, it requires as input (i) a fixed polyhedral geometry with defined facets, and (ii) a set of functions that describe the surface energy as a function of dopant content for different crystallographic planes. Two Sb-doped SnO2 nanocrystalline systems with different morphology and dopant content were selected as a case study, and the calculation of the dopant distributions expected for them is presented in detail. The obtained results were compared to previously reported characterization of this system by a combination of HRTEM and surface energy calculations, and both methods are shown to be equivalent. Considering its application pre-requisites, the present theoretical approach can provide a first estimation of doping atom distribution for a wide range of nanocrystalline systems. We expect that its use will support the reduction of experimental effort for the characterization of doped nanocrystals, and also provide a solution to the characterization of systems where even state-of-art analytical techniques are limited.

Características da tuberculose em idosos no Recife (PE): contribuição para o programa de controle / Characteristics of elderly tuberculosis patients in Recife, Brazil: a contribution to the tuberculosis control program

OBJETIVO: Descrever as características demográficas, de hábitos de vida, socioeconômicas, clínico-epidemiológicas e de acesso aos serviços de saúde de idosos com tuberculose, diagnosticados e tratados no Recife (PE), e compará-las com os adultos jovens em mesmas condições. MÉTODOS: Utilizou-se uma estratégia de análise do tipo caso-controle em uma coorte de pacientes com tuberculose, atendidos nas unidades de saúde pública do Recife no período de maio de 2001 a julho de 2003. RESULTADOS: Foram incluídos no estudo 1.127 pacientes, 136 idosos (casos) e 991 adultos jovens (controles). Nos dois grupos o sexo prevalente foi o masculino e a forma da doença a pulmonar. O etilismo foi mais freqüente entre os controles e o analfabetismo entre os casos. Os idosos queixaram-se menos de tosse, sudorese e dor torácica. A sorologia para o vírus da imunodeficiência humana foi realizada em apenas 29 pacientes (2,6 por cento). Os controles tiveram maior percentual de positividade nos exames de baciloscopia e cultura. Ambos os grupos tiveram que procurar mais de dois serviços de saúde e passaram-se mais de dois meses até que se fizesse o diagnóstico da doença. Os idosos tiveram maiores índices de cura e óbito, e abandonaram menos o tratamento. CONCLUSÃO: Na população estudada, os idosos apresentaram menos tosse, sudorese noturna e dor torácica, menor positividade nos exames complementares e maior mortalidade. Devem constituir um grupo com abordagem especial dos serviços de saúde pública.

OBJECTIVE: To describe the demographic characteristics, everyday habits, socio-economic conditions, clinico-epidemiological profiles and access to health care services among the elderly patients with tuberculosis diagnosed and treated in the city of Recife, Brazil, comparing them to those observed in young adults with tuberculosis. METHODS: A case-control type strategy was used to evaluate a cohort of patients with tuberculosis, all of whom were treated in public health care facilities in Recife between May of 2001 and July of 2003. RESULTS: The final cohort consisted of 1127 patients: 136 elderly patients (cases) and 991 young adults (controls). In both groups, males predominated, and the most common form of tuberculosis was the pulmonary form. Alcoholism was more common in the control group, whereas illiteracy was more common in the case group. There were fewer complaints of cough, sweats and chest pain among the patients in the case group than among those in the control group. Serological testing for the human immunodeficiency virus was performed in only 29 patients (2.6 percent). The percentage of positive sputum smear microscopy results, as well as that of positive cultures, was higher in the controls. Prior to being diagnosed with the disease, patients in both groups had sought treatment at more than two health care facilities and had waited more than two months (after first seeking treatment). The elderly patients presented higher indices of cure and were more often compliant with the treatment regimen, yet presented higher mortality rates. CONCLUSION: In the population studied, the elderly presented less cough, fewer episodes of night sweats and less chest pain, as well as less often presenting positivity on complementary exams. Nevertheless, the mortality rate was higher among the elderly patients than among the young adult patients. Elderly patients with tuberculosis constitute a population that should be given special attention...

Characteristics of elderly tuberculosis patients in Recife, Brazil: a contribution to the tuberculosis control program.

OBJECTIVE: To describe the demographic characteristics, everyday habits, socio-economic conditions, clinico-epidemiological profiles and access to health care services among the elderly patients with tuberculosis diagnosed and treated in the city of Recife, Brazil, comparing them to those observed in young adults with tuberculosis. METHODS: A case-control type strategy was used to evaluate a cohort of patients with tuberculosis, all of whom were treated in public health care facilities in Recife between May of 2001 and July of 2003. RESULTS: The final cohort consisted of 1127 patients: 136 elderly patients (cases) and 991 young adults (controls). In both groups, males predominated, and the most common form of tuberculosis was the pulmonary form. Alcoholism was more common in the control group, whereas illiteracy was more common in the case group. There were fewer complaints of cough, sweats and chest pain among the patients in the case group than among those in the control group. Serological testing for the human immunodeficiency virus was performed in only 29 patients (2.6%). The percentage of positive sputum smear microscopy results, as well as that of positive cultures, was higher in the controls. Prior to being diagnosed with the disease, patients in both groups had sought treatment at more than two health care facilities and had waited more than two months (after first seeking treatment). The elderly patients presented higher indices of cure and were more often compliant with the treatment regimen, yet presented higher mortality rates. CONCLUSION: In the population studied, the elderly presented less cough, fewer episodes of night sweats and less chest pain, as well as less often presenting positivity on complementary exams. Nevertheless, the mortality rate was higher among the elderly patients than among the young adult patients. Elderly patients with tuberculosis constitute a population that should be given special attention in public health care facilities.