Microsecond time-resolved X-ray diffraction for the investigation of fatigue behavior during ultrasonic fatigue loading

A new method based on time-resolved X-ray diffraction is proposed in order to measure the elastic strain and stress during ultrasonic fatigue loading experiments. Pure Cu was chosen as an example material for the experiments using a 20 kHz ultrasonic fatigue machine mounted on the six-circle diffractometer available at the DiffAbs beamline on the SOLEIL synchrotron facility in France. A two-dimensional hybrid pixel X-ray detector (XPAD3.2) was triggered by the strain gage signal in a synchronous data acquisition scheme (pump-probe-like). The method enables studying loading cycles with a period of 50 µs, achieving a temporal resolution of 1 µs. This allows a precise reconstruction of the diffraction patterns during the loading cycles. From the diffraction patterns, the position of the peaks, their shifts and their respective broadening can be deduced. The diffraction peak shift allows the elastic lattice strain to be estimated with a resolution of ∼10^-5. Stress is calculated by the self-consistent scale-transition model through which the elastic response of the material is estimated. The amplitudes of the cyclic stresses range from 40 to 120 MPa and vary linearly with respect to the displacement applied by the ultrasonic machine. Moreover, the experimental results highlight an increase of the diffraction peak broadening with the number of applied cycles.

Listeriosis surveillance: 1991

A total of 130 cases of listeriosis was reported in England, Wales and Northern Ireland in 1991. This represents a slight increase on the 1990 total of 118 reports but a marked decline compared with the peak incidence of reporting of 291 in 1988, which was part of an upsurge of cases between 1987 and mid 1989. Two epidemiological features of note in 1991 were the reappearance of a late summer-autumn peak in cases (commonly seen prior to 1987) and an increase in the number of reports among younger patients and children. The decline in listeriosis observed during the second half of 1989, which followed government health warnings about the consumption of pâté, and the continued low level of reporting since 1989 may be due to the disappearance of a common food source. However, in the light of the recent outbreak of listeriosis in France it is important that diagnostic vigilance and warnings about high risk foods are maintained.

Spontaneous abortion and work with visual display units

OBJECTIVE

To determine whether women who work with visual display units are at increased risk of spontaneous abortion.

DESIGN

Case-control study.

SETTING

Women were recruited during the three years 1987-9 from the Royal Berkshire Hospital in Reading, and from a large group practice situated within the hospital's catchment area.

SUBJECTS

Cases were 150 nulliparous working women with a clinically diagnosed spontaneous abortion and controls were 297 nulliparous working women attending for antenatal care.

MAIN OUTCOME MEASURES

Cases and controls were contacted and personally interviewed using the same structured questionnaire. Exposure to visual display units (VDUs) at work was assessed from information supplied at interview.

RESULTS

No evidence of an increased risk of spontaneous abortion was found in women who reported that they used a VDU at work compared with women who reported that they did not (odds ratio (OR) = 0.9, 95% confidence interval (95% CI) = 0.6-1.4); and no relation with the amount of time spent actively using a VDU was evident (OR = 0.9, 95% CI = 0.5-1.6 for women who worked with a VDU for 21 hours or more each week). No effect of passive exposure to VDUs at work was found (OR = 0.9, 95% CI = 0.6-1.6 for women who reported working less than 10 feet away from a VDU that was usually switched on). These findings were not explained by maternal age, marital state, housing tenure, partner's social class, educational level, smoking, alcohol consumption, or number of previous spontaneous abortions.

CONCLUSION

Given the findings and their consistency with the results from other recent studies it is concluded that pregnant women who work with VDUs are not at increased risk of clinically diagnosed spontaneous abortion. For the many women who use VDUs in their jobs, this finding provides reassurance.

Listeriosis surveillance: 1990

The annual numbers of reports of listeriosis in England, Wales and Northern Ireland received by the PHLS Communicable Disease Surveillance Centre (CDSC) and the Division of Microbiological Reagents (DMR) have shown remarkable changes in recent years. There was a near doubling in 1987 compared to 1986; a further increase in 1988; a sharp decline in 1989 (which occurred in the second half of that year) and, finally, the total in 1990 was the lowest since 1984. The rise and fall particularly (but not exclusively) involved pregnancy-associated cases and illness caused by serotype 4. The epidemiological and clinical features reported in 1990 were otherwise similar to those reported in previous years and in other countries. Patients with the non pregnancy-associated (also called 'adult/juvenile') type were in the majority, most of whom had an underlying disorder associated with impaired immunity. The reason for the changes in reported incidence is not completely understood but is probably due to the emergence and disappearance of a common food source of the organism. There is, however, no cause for complacency. Diagnostic vigilance must be maintained and vulnerable groups should adhere to existing dietary advice.