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1.
We analysed rates of detection for smear abnormalities in 255,000 women served by the Bristol screening programme. The programme began in 1966 with the aim of eradicating the 30-40 deaths each year in Bristol from cervical cancer. Organisation has been good and population uptake has been high for the past 15 years. Records were computerised in 1977. During the 1988 to 1993 screening round, 225,974 women were tested. New smear abnormalities were found in 15,551, of whom nearly 6000 were referred for colposcopy. These numbers are excessively high in comparison with the incidence of the malignancy we are trying to prevent. The effect of screening on death rates in Bristol is too small to detect. Our conclusion is that despite good organisation of the service, much of our effort in Bristol is devoted to limiting the harm done to healthy women and to protecting our staff from litigation as cases of serious disease continue to occur. The real lesson from 30 years' cervical screening is that no matter how obvious the predicted benefit may seem for any screening test, introduction should never take place without adequate prior evaluation of both positive and negative effects in controlled trials. 相似文献
2.
Qufei Xie Abdel E. Bayoumi L. Alden Kendall 《Journal of Materials Shaping Technology》1990,8(4):255-265
This paper presents the results of an investigation of induced residual stress, induced strain, and induced subsurface energy
in machined surfaces due to the machining process. The influence of tool wear on residual stress, strain, and energy is also
reported. The exact elasticity solution for a split ring was extended and used to calculate the residual stress in the machined
surface by using ring dimension changes caused by the electrochemical removal of a thin layer of residually stressed surface.
The strain distribution beneath the machined surface was determined by using the grid technique. The subsurface energy stored
in the machined surface was then obtained from the data of residual stress and strain. For the materials studied, this investigation
showed that such energy could not be neglected when establishing the total energy needed for machining a unit volume of material.
Tool coatings having different surface roughness and tools having various magnitudes of flank wear were investigated. The
experimental results show that tool wear is a dominant factor affecting the values of induced residual stress, strain, subsurface
energy, and the quality of the machined surface. The increase of tool wear caused an increase of residual stress and strain
beneath the machined surface. It was also found that the overall energy stored in the machined subsurface increases as the
tool wear increases and as the tool surface gets rougher. When the cutting tool is severely worn, the machined surface not
only becomes very rough, but also contains many partially fractured laps or cracks. This makes tool wear a key factor in controlling
the quality of the machined surface. 相似文献
3.
4.
Thomas H. Alden 《Metallurgical and Materials Transactions A》1977,8(11):1675-1679
According to the theory of thermally-activated deformation, the plastic strain rate equality
will hold in a load relaxation experiment, wheret = 0 is de-fined as the time at which the crosshead stops. In this theory, plastic flow is intrinsically time dependent and
its rate is controlled by interaction of glide dislocations with thermal obstacles(e.g. forest dislocations). The strain rate equation is of the form
and att = 0 none of these variables changes instantaneously. Measurements reported here for [111] aluminum single crystals indicate
that this prediction is wrong. The ratio
is near zero at low stress and approaches unity only at high stress. This result is predicted if plastic strain itself is
time-independent (athermal), as in the author’s recent theory. Time-dependent strain is then the result of thermal changes
in structure, namely loss (recovery) and rearrangement of obstacle dislocations. Experi-ments were also done to test further
the essential hypothesis of Hart’s recent formula-tion of an equation of state for plastic deformation-namely that each distinct
σ-@#@
curve derived from load relaxation data corresponds to a unique “hardness” state and that re-covery does not occur. Significant
differences were observed in the 77 K strsss-strain curves for 295 K relaxed and unrelaxed samples which indicate that substantial
loss and some rearrangement of dislocations has occurred during the relaxation. It is concluded from both experiments that
load relaxation in aluminum is a manifestation of recovery creep and cannot be taken as evidence for a plastic equation of
state. 相似文献
5.
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7.
Joe Chalfoun Antonio Cardone Alden A. Dima Daniel P. Allen Michael W. Halter 《Journal of research of the National Institute of Standards and Technology》2010,115(6):477-486
In order to facilitate the extraction of quantitative data from live cell image sets, automated image analysis methods are needed. This paper presents an introduction to the general principle of an overlap cell tracking software developed by the National Institute of Standards and Technology (NIST). This cell tracker has the ability to track cells across a set of time lapse images acquired at high rates based on the amount of overlap between cellular regions in consecutive frames. It is designed to be highly flexible, requires little user parameterization, and has a fast execution time. 相似文献
8.
This paper analyses the contested concept of ‘social exclusion’, discusses the reasons for the concept's current prominence in discussions of public policy, and reviews recent European Union initiatives designed to tackle the problem. 相似文献
9.
10.
Tausha R. Carlson Bradley P. Marks Alden M. Booren Elliot T. Ryser Alicia Orta-Ramirez 《Journal of food science》2005,70(7):m363-m366
Many factors, such as fat content and pH, are known to affect thermal inactivation of pathogens in meat products, and a few studies have suggested that the humidity of the cooking environment also affects thermal inactivation. However, the effect of process humidity has not been previously isolated from the effect of water activity on Salmonella inactivation. Therefore, the objective of this study was to directly test the effect of meat water activity on thermal inactivation of Salmonella. Ground turkey was dried to achieve water activities of 0.95 to 0.99, inoculated with an 8‐strain Salmonella cocktail, and heated isothermally (60 °C) in a water bath. The rate of thermal inactivation of Salmonella decreased 64% (P < 0.01) when decreasing meat water activity from 0.99 to 0.95. Inclusion of water activity improved the accuracy of a 1st‐order/Arrhenius‐type inactivation model from 1.94 log10 to 0.8 log10 (colony‐forming units [CFU]/g). 相似文献