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1.
J Prev Alzheimers Dis ; 11(3): 710-720, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38706287

RESUMO

BACKGROUND: The potential for greenness as a novel protective factor for Alzheimer's disease (AD) requires further exploration. OBJECTIVES: This study assesses prospectively and longitudinally the association between precision greenness - greenness measured at the micro-environmental level, defined as the Census block - and AD incidence. DESIGN: Older adults living in consistently high greenness Census blocks across 2011 and 2016 were compared to those living in consistently low greenness blocks on AD incidence during 2012-2016. SETTING: Miami-Dade County, Florida, USA. PARTICIPANTS: 230,738 U.S. Medicare beneficiaries. MEASUREMENTS: U.S. Centers for Medicare and Medicaid Services Chronic Condition Algorithm for AD based on ICD-9 codes, Normalized Difference Vegetation Index, age, sex, race/ethnicity, neighborhood income, and walkability. RESULTS: Older adults living in the consistently high greenness tertile, compared to those in the consistently low greenness tertile, had 16% lower odds of AD incidence (OR=0.84, 95% CI: 0.76-0.94, p=0.0014), adjusting for age, sex, race/ethnicity, and neighborhood income. Age, neighborhood income and walkability moderated greenness' relationship to odds of AD incidence, such that younger ages (65-74), lower-income, and non-car dependent neighborhoods may benefit most from high greenness. CONCLUSIONS: High greenness, compared to low greenness, is associated with lower 5-year AD incidence. Residents who are younger and/or who reside in lower-income, walkable neighborhoods may benefit the most from high greenness. These findings suggest that consistently high greenness at the Census block-level, may be associated with reduced odds of AD incidence at a population level.


Assuntos
Doença de Alzheimer , Humanos , Doença de Alzheimer/epidemiologia , Feminino , Idoso , Masculino , Florida/epidemiologia , Estudos Longitudinais , Estados Unidos/epidemiologia , Incidência , Idoso de 80 Anos ou mais , Características da Vizinhança , Medicare/estatística & dados numéricos , Características de Residência , Estudos Prospectivos
2.
BJS Open ; 5(2)2021 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-33834189

RESUMO

BACKGROUND: Determining the cost-effectiveness and sustainability of patient blood management programmes relies on quantifying the economic burden of preoperative anaemia. This retrospective cohort study aimed to evaluate the hospital costs attributable to preoperative anaemia in patients undergoing major abdominal surgery. METHODS: Patients who underwent major abdominal surgery between 2010 and 2018 were included. The association between preoperative patient haemoglobin (Hb) concentration and hospital costs was evaluated by curve estimation based on the least-square method. The in-hospital cost of index admission was calculated using an activity-based costing methodology. Multivariable regression analysis and propensity score matching were used to estimate the effects of Hb concentration on variables related directly to hospital costs. RESULTS: A total of 1286 patients were included. The median overall cost was US $18 476 (i.q.r.13 784-27 880), and 568 patients (44.2 per cent) had a Hb level below 13.0 g/dl. Patients with a preoperative Hb level below 9.0 g/dl had total hospital costs that were 50.6 (95 per cent c.i. 14.1 to 98.9) per cent higher than those for patients with a preoperative Hb level of 9.0-13.0 g/dl (P < 0.001), 72.5 (30.6 to 128.0) per cent higher than costs for patients with a Hb concentration of 13.1-15.0 g/dl (P < 0.001), and 62.4 (21.8 to 116.7) per cent higher than those for patients with a Hb level greater than 15.0 g/dl (P < 0.001). Multivariable general linear modelling showed that packed red blood cell (PRBC) transfusions were a principal cost driver in patients with a Hb concentration below 9.0 g/dl. CONCLUSION: Patients with the lowest Hb concentration incurred the highest hospital costs, which were strongly associated with increased PRBC transfusions. Costs and possible complications may be decreased by treating preoperative anaemia, particularly more severe anaemia.


Assuntos
Abdome/cirurgia , Anemia/etiologia , Custos Hospitalares/estatística & dados numéricos , Cuidados Pré-Operatórios/economia , Idoso , Anemia/terapia , Análise Custo-Benefício , Feminino , Hemoglobinas/análise , Humanos , Modelos Lineares , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Estudos Retrospectivos
3.
Eur J Clin Nutr ; 71(7): 870-880, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28378847

RESUMO

There has been a marked increase in the prevalence of diabetes in Asia, including China, over the last few decades. While the increased prevalence of diabetes has often been attributed to the nutritional transition associated with recent economic development, emerging data suggest that early-life exposures also play a major role in shaping developmental trajectories, and contributes to alter an individual's susceptibility to diabetes and other non-communicable diseases (NCDs). Early-life exposures such as in utero exposure to undernutrition has been consistently linked with later risk of diabetes and obesity. Furthermore, in utero exposure to maternal hyperglycemia, maternal obesity and excess gestational weight gain are all linked with increased childhood obesity and later risk of diabetes. Emerging data have also highlighted the potential link between early-feeding practices, the role of one-carbon metabolism in metabolic programming and endocrine disrupting chemicals (EDCs) with later risk of diabetes. These different developmental exposures may all be highly relevant to the current epidemic of diabetes in China. For example, the prevalence of gestational diabetes has increased markedly over the last two decades, and may contribute to the diabetes epidemic by driving macrosomia, childhood obesity and later risk of diabetes. In order to address the current burden of diabetes, a lifecourse perspective, incorporating multisectoral efforts from public health policy down to the individuals, will be needed. Several major initiatives have been launched in China as part of its national plans for NCD prevention and treatment, and the experience from these efforts would be invaluable.


Assuntos
Diabetes Mellitus Tipo 2/epidemiologia , Diabetes Gestacional/epidemiologia , Desnutrição/epidemiologia , Fenômenos Fisiológicos da Nutrição Materna , Obesidade/epidemiologia , Complicações na Gravidez/epidemiologia , China/epidemiologia , Dieta , Feminino , Comportamentos Relacionados com a Saúde , Política de Saúde , Humanos , Estilo de Vida , Metanálise como Assunto , Gravidez , Efeitos Tardios da Exposição Pré-Natal , Prevalência , Saúde Pública , Fatores de Risco
4.
BJOG ; 123 Suppl 3: 23-9, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27627592

RESUMO

OBJECTIVE: To assess the feasibility and performance of the first-trimester combined screening test for trisomy 21 in a resource-limited setting in mainland China. DESIGN: Prospective observational cohort study. SETTING: First Affiliated Hospital of Kunming Medical University, China. POPULATION: Ten thousand four hundred and forty-two pregnant women requesting first-trimester screening. METHODS: The combined screening test was performed from May 2012 to December 2014. Women with a high-risk result (≥1:600) were offered further confirmatory tests after counselling. The threshold for high risk was determined by Monte Carlo simulation to achieve a 5% false-positive rate according to the local age distribution. Pregnancy outcome and screening results were recorded for all women and monthly audits were conducted. MAIN OUTCOME MEASURES: Sensitivity, screen positive rate, cost per case of Down syndrome detected. RESULTS: Six hundred and ten women (5.8% of the total screened) had a high-risk screening test, of whom 274 (44.9%) underwent a diagnostic test and 169 (27.7%) opted for a noninvasive prenatal screening test (NIPT); 160 (26.2%) declined further testing after counselling. The pregnancy outcome was available for 10 174 (97.4%) of the women. The observed incidence of Down syndrome was 0.13% (1/750). All 14 women with a trisomy 21 pregnancy had a high-risk screening test result. The cost per Down syndrome detected was RMB596 686 compared with RMB1.79 million if all had been screened by NIPT. CONCLUSIONS: The combined screening test appears to be a more cost-effective strategy in mainland China. Screening performance in China would be improved by adopting Chinese-specific models, external quality control and assurance, and establishing risk thresholds appropriate for the age distribution of the population. TWEETABLE ABSTRACT: Combined first-trimester Downs screening in China was improved by adopting Chinese-specific models and external QC.


Assuntos
Síndrome de Down/diagnóstico , Primeiro Trimestre da Gravidez , Diagnóstico Pré-Natal , Adulto , China , Gonadotropina Coriônica Humana Subunidade beta/análise , Síndrome de Down/epidemiologia , Estudos de Viabilidade , Feminino , Recursos em Saúde/economia , Humanos , Idade Materna , Medição da Translucência Nucal , Gravidez , Resultado da Gravidez , Proteína Plasmática A Associada à Gravidez/análise , Diagnóstico Pré-Natal/economia , Diagnóstico Pré-Natal/métodos , Estudos Prospectivos , Fatores de Risco , Ultrassonografia/economia
5.
Diabet Med ; 31(3): 302-18, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24417604

RESUMO

There has been a marked increase in the prevalence of diabetes in Asia over recent years. Diabetes complicating pregnancy, in particular gestational diabetes, has also increased markedly in the region. Multi-ethnic studies have highlighted the increased risk of gestational diabetes mellitus among the different Asian populations. Prevalence of gestational diabetes in Asian countries varies substantially according to the screening strategy and diagnostic criteria applied, and ranges from 1% to 20%, with evidence of an increasing trend over recent years. The International Association for Diabetes in Pregnancy Study group criteria have been adopted by some Asian countries, although they present significant challenges in implementation, especially in low-resource settings. Studies on offspring of mothers with gestational diabetes have reported adverse cardiometabolic profiles and increased risk of diabetes and obesity. Gestational diabetes is likely to be a significant factor contributing to the epidemic of diabetes and other non-communicable diseases in the Asian region. In recognition of this, several large-scale prevention and intervention programmes are currently being implemented in different Asian countries in order to improve glucose control during pregnancy, as well as overall maternal health. Lessons emerging from gestational diabetes studies in Asia may help inform and provide insights on the overall burden and treatment strategies to target gestational diabetes, with the ultimate aim to reduce its adverse short- and long-term consequences.


Assuntos
Povo Asiático , Diabetes Mellitus Tipo 2/prevenção & controle , Diabetes Gestacional/diagnóstico , Programas de Rastreamento/organização & administração , Obesidade/prevenção & controle , Gravidez em Diabéticas/diagnóstico , Ásia/epidemiologia , Análise Custo-Benefício , Diabetes Mellitus Tipo 2/epidemiologia , Diabetes Gestacional/epidemiologia , Diagnóstico Precoce , Feminino , Teste de Tolerância a Glucose , Humanos , Recém-Nascido , Obesidade/epidemiologia , Inovação Organizacional , Gravidez , Gravidez em Diabéticas/epidemiologia , Prevalência , Saúde Pública , Fatores de Risco
6.
J Int Med Res ; 37(5): 1311-20, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19930836

RESUMO

This study aimed to investigate the effects of sleep deprivation on postural control, subjective fatigue assessment and psychomotor performance, and to assess the efficiency of an objective posturographic test as an indicator of mental fatigue. Postural sway using static posturography (Romberg's test), subjective fatigue assessment (Stanford Sleepiness Scale) and psychomotor performance (Sternberg dual-task test) were assessed in 12 subjects before and after 24 h of sustained wakefulness. After sustained wakefulness, the Romberg test parameters of circumference area and rectangle area with the eyes-closed, and standard deviation in the anterior-posterior direction with the eyes-open were significantly higher compared with baseline values (before sustained wakefulness). Subjective fatigue assessment scores were also significantly increased, while psychomotor performance was unchanged. Sleep deprivation can arouse a feeling of fatigue and can affect postural stability, hence an objective posturographic test score may be useful as an indicator of mental fatigue.


Assuntos
Fadiga/diagnóstico , Equilíbrio Postural/fisiologia , Desempenho Psicomotor , Privação do Sono/fisiopatologia , Adulto , Diagnóstico por Computador , Humanos , Masculino , Vigília , Adulto Jovem
7.
Nutr Hosp ; 22(5): 590-5, 2007.
Artigo em Espanhol | MEDLINE | ID: mdl-17970544

RESUMO

With the objective of studying the nutritional status and its relationship with hospitalization period, a cross-sectional study was done with patients from a private hospital representing a population with a better socioeconomic condition. The anthropometric data of 267 patients, 46% males and 54% females ranging from 20 to 80 years of age, were assessed on the second day of hospitalization. Hospitalization period associated with nutritional status. The data were analyzed by the software Excel and Sigma Stat, using Fisher's exact test and the chi-square test. The studied population presented a body mass index of 25.9 +/- 5.3 and most patients lost weight during hospitalization. The longest hospitalization periods were found among patients with lung diseases (13 days), some being pre-obese (40%) with a small prevalence of undernutrition (4%). The percentage distribution of nutritional status among the groups according to diagnosis was different (P < 0.01) when assessed by the Fisher's exact test and the percentage distribution in weight variation between men and women was different (P < 0.02) when assessed by the chi-square test. When the population was segmented according to age, the percentage distribution of the nutritional status between > 60 and < or = 60 did not present a difference when assessed by the chi-square test. The results of this study show that the nutritional status in some diseases deserves special attention given the greater risk found in these situations, contributing to a longer hospitalization period.


Assuntos
Pacientes Internados/estatística & dados numéricos , Tempo de Internação/estatística & dados numéricos , Desnutrição/epidemiologia , Estado Nutricional , Adulto , Idoso , Idoso de 80 Anos ou mais , Antropometria , Brasil/epidemiologia , Grupos Diagnósticos Relacionados , Feminino , Hospitais Privados/estatística & dados numéricos , Humanos , Masculino , Pessoa de Meia-Idade
8.
Br J Dermatol ; 154(4): 658-64, 2006 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-16536808

RESUMO

BACKGROUND: The role of nickel in causing hand dermatitis in some occupations has been difficult to assess due to problems with reliable measurement of the exposure to nickel in the workplace and lack of a definitive threshold for nickel allergic contact dermatitis. It is not uncommon to find nickel allergy on patch testing but it is difficult to determine whether this is of relevance to occupational nickel exposure or simply a reflection of past exposure to nickel-plated jewellery or other nonoccupational nickel exposure. OBJECTIVES: To devise a simple and reproducible method to quantify the amount of nickel on the skin and to apply the technique to measure dermal nickel exposure in various occupational settings. METHODS: A rapid and simple sampling procedure was developed for determination of nickel on the skin of workers potentially exposed to nickel by exposing individuals to nickel-releasing coins and measuring exposure by immersing the exposed thumbs and index fingers directly into graduated sample tubes containing ultrapure water and aqueous nickel extracts. The solutions were analysed by inductively coupled plasma-optical emission spectrometry after stabilization with nitric acid. The method shows advantages over alternatives such as wipe testing and tape stripping in terms of extraction efficiency, speed and ease of operation in the field. A pilot survey of dermal nickel exposure for workers in several occupational settings was conducted. RESULTS: The study suggested that a 'normal' level of nickel on the skin is <10 ng cm(-2). Coin handling induced an appreciable increase in the amount of nickel on the skin within 2 min. Experiments indicated a linear relationship between coin handling (exposure time) and measured dermal nickel levels following standardized coin handling. A pilot survey, conducted among cashiers, shop assistants, bar staff, hairdressers and workers in the nickel industry revealed dermal nickel concentrations ranging from <0.9 to 7160 ng cm(-2). The levels of nickel on the skin of cashiers, shop assistants, bar staff and hairdressers were below the threshold level for water-soluble ionic nickel for occluded exposure at which 10% of nickel-allergic subjects react (0.01% or 100 parts per million, equivalent to 530 ng cm(-2)) and the five-times higher threshold for unoccluded exposure (500 parts per million). The levels in some nickel platers and nickel refinery workers approached or exceeded these levels. However, few cases of nickel dermatitis are observed in plating and refinery facilities, perhaps due to immune tolerance, self-selection or, for refinery workers, exposure to water-insoluble rather than water-soluble nickel compounds. The elicitation threshold for water-soluble nickel compounds cannot be compared directly with dermal exposure to water-insoluble nickel compounds as the latter release a significantly lesser amount of nickel ions. CONCLUSIONS: We describe a reproducible, simple and rapid procedure for the assessment of nickel levels in occupationally exposed individuals.


Assuntos
Níquel/análise , Numismática , Exposição Ocupacional/análise , Dedos , Dermatoses da Mão/induzido quimicamente , Humanos
9.
Kidney Int ; 69(2): 383-7, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16408130

RESUMO

Although much emphasis has been placed on screening for albuminuria in type II diabetic patients, less attention has been focused on the role of glomerular filtration rate (GFR) in the assessment of risk. Herein, we examined the association between GFR and vascular complications in a consecutive cohort of 5174 type II diabetic patients between 1995 and 2000. Renal function was assessed by GFR (estimated by Modification of Diet in Renal Disease equation). The frequency of chronic kidney disease (CKD) as defined by GFR <60 ml/min/1.73 m(2), micro- and macrovascular complications, and their associations were analyzed. In this study cohort, 6% had serum creatinine > or =150 micromol/l and 15.8% had CKD. After adjustment for potential confounders, including urinary albumin excretion, odds ratios [95% confidence interval (CI)] across different stages of estimated GFR (> or =90, 60-89, 30-59, 15-29, <15 ml/min/1.73 m(2)) for macrovascular disease were 1.00, 1.42 [1.12-1.80], 1.80 [1.32-2.45], 2.74 [1.64-4.56], and 4.05 [1.77-9.26], respectively (P for trend <0.001); for retinopathy were 1.00, 1.23 [1.04-1.46], 1.80 [1.40-2.30], 2.05 [1.25-3.37], and 4.12 [1.56-10.90], respectively (P for trend <0.001); for sensory neuropathy were 1.00, 1.53[1.27-1.85], 2.09 [1.58-2.76], 4.32 [2.41-7.77], and 3.16 [1.25-8.02], respectively (P for trend <0.001); and for microalbumuria (with GFR <15 ml/min/1.73 m(2) excluded from the analysis) were 1.00, 1.51 [1.30-1.75], 5.80 [4.52-7.44], and 52.5 [16.4-168.2] respectively (P for trend <0.001). Measurement of serum creatinine alone without GFR may underestimate renal impairment in type II diabetic patients. Decreasing GFR was significantly associated with increasing frequency of micro- and macrovascular complications.


Assuntos
Albuminúria/fisiopatologia , Diabetes Mellitus Tipo 2/fisiopatologia , Angiopatias Diabéticas/fisiopatologia , Nefropatias Diabéticas/fisiopatologia , Taxa de Filtração Glomerular , Adulto , Idoso , Creatinina/sangue , Diabetes Mellitus Tipo 2/urina , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
10.
Sci Total Environ ; 299(1-3): 1-19, 2002 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-12462571

RESUMO

Traffic is the main source of platinum-group element (PGE) contamination in populated urban areas. There is increasing concern about the hazardous effects of these new pollutants for people and for other living organisms in these areas. Airborne and road dusts, as well as tree bark and grass samples were collected at locations in the European cities of Göteborg (Sweden), Madrid (Spain), Rome (Italy), Munich (Germany), Sheffield and London (UK). Today, in spite of the large number of parameters that can influence the airborne PGE content, the results obtained so far indicate significantly higher PGE levels at traffic sites compared with the rural or non-polluted zones that have been investigated (background levels). The average Pt content in airborne particles found in downtown Madrid, Göteborg and Rome is in the range 7.3-13.1 pg m(-3). The ring roads of these cities have values in the range 4.1-17.7 pg m(-3). In Munich, a lower Pt content was found in airborne particles (4.1 pg m(-3)). The same tendency has been noted for downtown Rh, with contents in the range 2.2-2.8 pg m(-3), and in the range 0.8-3.0 and 0.3 pg m(-3) for motorway margins in Munich. The combined results obtained using a wide-range airborne classifier (WRAC) collector and a PM-10 or virtual impactor show that Pt is associated with particles for a wide range of diameters. The smaller the particle size, the lower the Pt concentration. However, in particles

Assuntos
Poluentes Atmosféricos/análise , Exposição por Inalação , Compostos de Platina/análise , Saúde Pública , Emissões de Veículos/análise , Poluentes Atmosféricos/efeitos adversos , Cidades , Poeira , Monitoramento Ambiental , Europa (Continente) , Humanos , Tamanho da Partícula , Compostos de Platina/efeitos adversos , Medição de Risco , População Urbana , Emissões de Veículos/efeitos adversos
11.
J Am Coll Cardiol ; 38(1): 253-61, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-11451283

RESUMO

OBJECTIVES: We sought to determine the accuracy of transthoracic echocardiography (TTE) in identifying risk factors in patients with an atrioventricular septal defect (AVSD). BACKGROUND: Atrioventricular septal defect is a common lesion, and many decisions about it are based on echocardiography alone. The identification of associated left-sided inflow and outflow obstructive lesions is important, as they are responsible for mortality and morbidity. METHODS: Between 1983 to 1998, 549 patients with AVSD underwent repair. The TTE findings were correlated with surgery, angiocardiography, autopsy or postoperative TTE. Papillary muscle measurements were made in those with either a left ventricular outflow tract (LVOT) or left ventricular inflow abnormality and compared with those measurements from control subjects. Measurements of the LVOT were made in patients with an identified LVOT abnormality. RESULTS: There were 63 missed lesions, decreasing over time. Double-orifice left atrioventricular valve (DOLAVV) and nonobstructive chordae in the LVOT were more often missed. Reoperation was performed to address a missed lesion in 2 of 68 patients. Two of 55 patients died of reasons related to a missed lesion. In 67% of patients, DOLAVV was missed. Abnormal papillary muscle angles were seen with either a LVOT abnormality or DOLAVV. High insertion of the anterolateral papillary muscle was a risk factor for death or residual LVOT obstruction. Abnormal LVOT measurements were found in patients with tunnel obstruction and those with an acquired subaortic ridge. CONCLUSIONS: Transthoracic echocardiography provides accurate preoperative information on AVSD.


Assuntos
Comunicação Interatrial/diagnóstico por imagem , Comunicação Interventricular/diagnóstico por imagem , Obstrução do Fluxo Ventricular Externo/diagnóstico por imagem , Adolescente , Criança , Pré-Escolar , Comunicação Interatrial/complicações , Comunicação Interatrial/cirurgia , Comunicação Interventricular/complicações , Comunicação Interventricular/cirurgia , Humanos , Lactente , Recém-Nascido , Músculos Papilares/patologia , Estudos Retrospectivos , Fatores de Risco , Ultrassonografia , Obstrução do Fluxo Ventricular Externo/complicações , Obstrução do Fluxo Ventricular Externo/patologia
12.
Med Phys ; 27(11): 2560-4, 2000 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-11128308

RESUMO

A new conducting plastic has been composed which accurately simulates the photon and neutron absorption properties of brain tissue. This tissue-equivalent (TE) plastic was formulated to match the hydrogen and nitrogen constituents recommended by ICRU Report #44 for brain tissue. Its development was initiated by the inability of muscle tissue-equivalent plastic to closely approximate brain tissue with respect to low-energy neutron interactions. This new plastic is particularly useful as an electrode in TE dosimetry devices for boron neutron capture therapy (BNCT), which utilizes low-energy neutrons for radiotherapy of the brain. Absorbed dose measurements in a clinical BNCT beam using a proportional counter constructed from this TE plastic show good agreement with Monte Carlo calculations.


Assuntos
Encéfalo/efeitos da radiação , Nêutrons , Fótons , Plásticos , Terapia por Captura de Nêutron de Boro/instrumentação , Método de Monte Carlo , Radiometria
13.
Anal Chem ; 72(20): 4878-81, 2000 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-11055703

RESUMO

Isotopic analysis of uranium in tree bark by ICP mass spectrometry is proposed as a new measurement strategy for monitoring airborne contamination and for discrimination of nuclear and nonnuclear emission sources. A quadrupole-based ICP mass spectrometer equipped with a microconcentric nebulizer and membrane desolvator was used to provide high-sensitivity measurement. The limit of detection for uranium (238U) was 0.004 ng L(-1). Measurement precision (235U/238U) was between 0.2 and 0.5% RSD for isotopic SRMs (U005 and U015; concentration, 1 microg L(-1)) and ranged from 0.4 to 3.1% RSD for tree bark extracts (U concentration, 0.03-0.08 microg L(-1)). Bark samples collected from the Peak District National Park in Derbyshire (U.K.) exhibited a natural 235U/238U isotope ratio value (0.0072) whereas samples from Sellafield, West Cumbria (U.K.) showed depletion in 235U (235U/238U = 0.0053-0.0064).

14.
Ann N Y Acad Sci ; 904: 148-51, 2000 May.
Artigo em Inglês | MEDLINE | ID: mdl-10865727

RESUMO

Differences in body size and shape can cause large variances in the in vivo results of neutron activation analysis. To introduce corrections for body size for the delayed gamma neutron activation facility at Brookhaven National Laboratory, "reference man"-sized and "reference woman"-sized phantoms were constructed. Simulation results using the Monte Carlo Neutron and Photon Transport code also provided correction factors for people of different sizes. For individuals with a body mass index (BMI = weight (kg)/height (m)2) between 20 and 30, no correction was required. At BMIs greater than 30, the effects of neutron attenuation were significant and a correction factor of CF = -0.0192 x BMI + 1.5635 can be applied.


Assuntos
Composição Corporal , Cálcio/análise , Análise de Ativação de Nêutrons , Constituição Corporal , Índice de Massa Corporal , Calibragem , Feminino , Humanos , Masculino , Método de Monte Carlo , Imagens de Fantasmas , Valores de Referência
15.
Space Med Med Eng (Beijing) ; 12(2): 106-10, 1999 Apr.
Artigo em Chinês | MEDLINE | ID: mdl-12430535

RESUMO

Objective. To compare the sensitivities of indexes used in the assessment of mental load. Method. Twenty five indexes belonging to primary task performance, additional task performance, subjective rate and psychophysiological measure were recorded during performance of 11 different difficult tasks. Result. It showed that tracking error (ER), reaction time (RT), correct rate (CR), category scale (CS), multistage evaluation scale (MES), multi-dimensional scale (MDS), latency of P3 (LAT), inter beat interval (IBI), inter respiration interval (IRI) and blink rate (BR) were significantly different among the various tasks. CS, MES and MDS were more sensitive to the total load; ER, LAT, IBI and IRI were more sensitive to the load of primary task, while RT and CR to that of additional task and BR to the visual load. Conclusion. It demonstrated that the sensitivities of the various indexes are different and the information are limited. Multi-indexes may be preferred for mental load assessment.


Assuntos
Processos Mentais , Desempenho Psicomotor , Análise e Desempenho de Tarefas , Carga de Trabalho , Medicina Aeroespacial , Humanos , Psicofisiologia , Tempo de Reação , Sensibilidade e Especificidade
16.
Appl Radiat Isot ; 49(5-6): 533-5, 1998.
Artigo em Inglês | MEDLINE | ID: mdl-9569536

RESUMO

Total body chlorine (TBCI), used to estimate the extracellular space, is measured by delayed-gamma neutron activation (DGNA) using the reaction 37Cl(n, gamma)38Cl, at Brookhaven National Laboratory. During the calibration process, we noticed that different values were obtained when different amounts of Cl were placed in the phantom. This non-linear relationship is due to the thermal neutron flux suppression by the thermal neutron capture reaction 35Cl(n, gamma)36Cl. Monte Carlo simulations confirm the results of phantom measurements showing an inverse relationship between the Cl content in the phantom and the gamma-ray yield per gram Cl. Thus, it is important to calibrate the DGNA system for TBCl using phantom standards containing an amount of Cl close to that expected in the individual undergoing measurement.


Assuntos
Composição Corporal , Cloro/análise , Espaço Extracelular , Imagens de Fantasmas , Calibragem , Simulação por Computador , Feminino , Raios gama , Humanos , Masculino , Método de Monte Carlo , Análise de Ativação de Nêutrons/métodos , Radioisótopos , Reprodutibilidade dos Testes , Esqueleto
17.
Appl Radiat Isot ; 49(5-6): 531-2, 1998.
Artigo em Inglês | MEDLINE | ID: mdl-9569535

RESUMO

Differences in body size and shape can cause large variances in the results of in vivo neutron activation analysis. Preliminary body-size correction data were obtained for the delayed-gamma neutron activation facility (DGNA) at Brookhaven National Laboratory (BNL), based on phantom standards of different sizes, used in combination with computer simulations on the effect of different body sizes.


Assuntos
Composição Corporal , Constituição Corporal , Imagens de Fantasmas , Índice de Massa Corporal , Cálcio , Simulação por Computador , Feminino , Raios gama , Humanos , Masculino , Método de Monte Carlo , Análise de Ativação de Nêutrons/métodos , Análise de Regressão
19.
Appl Radiat Isot ; 49(5-6): 731-2, 1998.
Artigo em Inglês | MEDLINE | ID: mdl-9569593

RESUMO

The precision and accuracy of a prompt-gamma neutron activation facility developed to assess total body protein in rats is estimated. The coefficient of variation of nitrogen measurement, as estimated by repeated measurements on 15 rats, was 5.5% for an equivalent dose of 60 mSv (Q = 20). Good agreement was observed in comparing the results of in vivo neutron activation analysis and chemical carcass analysis performed by the Kjeldahl method. The application of the technique in comparing the effect of a low-fat and a high-fat diet on body protein in rats is demonstrated.


Assuntos
Composição Corporal , Imagens de Fantasmas , Proteínas/análise , Análise de Variância , Animais , Dieta com Restrição de Gorduras , Gorduras na Dieta , Raios gama , Método de Monte Carlo , Análise de Ativação de Nêutrons/métodos , Nitrogênio/análise , Ratos , Reprodutibilidade dos Testes
20.
Phys Med Biol ; 43(2): 339-49, 1998 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-9509530

RESUMO

The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, repositioning the system's two NaI(Tl) detectors, and improving the neutron and gamma shielding of these detectors. The new source collimator has a graphite reflector around the 238PuBe neutron source to enhance the low-energy region of the neutron spectrum incident on the patient. The gamma detectors have been relocated from positions close to the upward-emerging collimated neutron beam to positions close to and at the sides of the patient. These modifications substantially reduced spurious counts resulting from the capture of small-angle scattered neutrons in the NaI detectors. The pile-up background under the 10.8 MeV 14N(n, gamma)15N spectral peak has been reduced so that the nitrogen peak-to-background ratio has been increased by a factor of 2.8. The resulting reduction in the coefficient of variation of the total body nitrogen measurements from 3% to 2.2% has improved the statistical significance of the results possible for any given number of patient measurements. The new system also has a more uniform composite sensitivity.


Assuntos
Raios gama , Análise de Ativação de Nêutrons/instrumentação , Nêutrons , Nitrogênio/análise , Imagens de Fantasmas , Humanos , Modelos Teóricos , Método de Monte Carlo , Análise de Ativação de Nêutrons/métodos , Isótopos de Nitrogênio , Reatores Nucleares , Proteção Radiológica , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
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