A K-CELL injection system for SH-PermEBIT

In this paper,we report a newly developed Knudsen Cell injection system for SH-PermEBIT.This technique can overcome disadvantages of introducing organometallic gases and wired probes into EBIT and provide steady continuous injection.A specially designed vacuum line is used to ensure that the Knudsen Cell satisfies the vacuum level of SH-permEBIT.Using this system we successfully injected ytterbium into the SH-pcrmEBIT and recorded a spectrum in the visible wavelength region.     

The use of controlled copper dissolution as an anti-fouling system

The use of copper as an anti-fouling surface is discussed and an electrochemical method for improving its performance is proposed. Seawater exposure trials of freely corroding, cathodically protected and electrochemically controlled copper specimens are described. The results show that the anti-fouling performance of copper surfaces may be improved by electrochemical control of its dissolution rates. The ultimate failure of the copper to anti-foul is due to insufficient dissolution rates. This may be due to electrochemical constraints, to the formation of insoluble corrosion products or to the precipitation of cathodic chalks at its surface.     

Efficient scatter modelling for incorporation in maximum likelihood reconstruction

Definition of a simplified model of scatter which can be incorporated in maximum likelihood reconstruction for single-photon emission tomography (SPET) continues to be appealing; however, implementation must be efficient for it to be clinically applicable. In this paper an efficient algorithm for scatter estimation is described in which the spatial scatter distribution is implemented as a spatially invariant convolution for points of constant depth in tissue. The scatter estimate is weighted by a space-dependent build-up factor based on the measured attenuation in tissue. Monte Carlo simulation of a realistic thorax phantom was used to validate this approach. Further efficiency was introduced by estimating scatter once after a small number of iterations using the ordered subsets expectation maximisation (OSEM) reconstruction algorithm. The scatter estimate was incorporated as a constant term in subsequent iterations rather than modifying the scatter estimate each iteration. Monte Carlo simulation was used to demonstrate that the scatter estimate does not change significantly provided at least two iterations OSEM reconstruction, subset size 8, is used. Complete scatter-corrected reconstruction of 64 projections of 40?128 pixels was achieved in 38 min using a Sun Sparc20 computer.     

Prevention and control of tuberculosis in the 1990s

Beginning in 1984, the long-term decline in tuberculosis (TB) cases stopped, and since 1985 the number of cases has actually increased by 18%, from 22,201 new cases in 1985 to 26,283 in 1991. The change in the morbidity trend appears to be primarily due to three factors: HIV coinfection, TB occurring in persons from countries where this disease is prevalent, and deterioration of the health care infrastructure with resultant outbreaks of TB. This article presents six interventions that address major areas where action is needed. These efforts will require coordinated action by health care providers, public health departments, and other public and private organizations. Protection of all workers and patients in health care settings is one important goal of these efforts.     

Differential effects of preterm birth and small gestational age on cognitive and motor development

AIMS: To determine the differential effects of preterm birth and being small for gestational age on the cognitive and motor ability of the child. METHODS: A longitudinal cohort of all infants of gestational age < or = 32 weeks born to mothers resident in the counties of Cheshire and Merseyside in 1980-1 was studied. The children were assessed at the age of 8 to 9 years using the Wechsler Intelligence Scale for Children, the Neale analysis of reading ability, and the Stott-Moyes-Henderson test of motor impairment. Adequacy of fetal growth was determined by the birthweight ratio--that is, the ratio of the observed birthweight to the expected birthweight for a given gestational age. Children with clinically diagnosed motor, learning or sensory disabilities were excluded. Information on social variables was obtained by a questionnaire completed by the parents. Of the 182 children, 158 were assessed. RESULTS: IQ was positively correlated with birthweight ratio but not with birthweight or gestational age. Motor ability was associated with birthweight, gestational age, and birthweight ratio. Reading comprehension was associated with birthweight ratio, but reading rate and accuracy were best explained by social variables and sex. IQ remained associated with birthweight ratio, after adjusting for maternal education, housing status, and number of social service benefits received. Reading ability was related to these social variables but motor ability was not. CONCLUSIONS: The effects of SGA and preterm birth differed: SGA was associated with cognitive ability, as measured by IQ and reading comprehension; motor ability was additionally associated with preterm birth. Reading rate and accuracy were not associated with SGA or preterm birth but were socially determined.