Measurements of the hole boring velocity from Doppler shifted harmonic emission from solid targets

The fast ignitor scheme for inertial confinement fusion requires forward driving of the critical density surface by light pressure (hole boring) to allow energy deposition close to the dense fuel. The recession velocity of the critical density surface has been observed to be nu/c = 0.015 at an irradiance of 1.0 x 10(19) W cm(-2) at a wavelength of 1.05 micron, in quantitative agreement with modeling. (C) 1996 American Institute of Physics.

Time-averaged velocity and turbulence intensity at the initial downstream flow from a six-bladed propeller

The current study investigated the time-averaged velocity and turbulence intensity at the initial downstream flow from a six-bladed ship propeller. The six-bladed propeller provided the rapid periodical pulses of thrust in one revolution due to the blades leading to a complex downstream jet. The six-bladed propeller is popular as a boat racing propeller, but the presentation of its flow structure was rarely found in the previous studies. In this study, the experiments were carried out in a water tank to measure the time-averaged velocity and turbulence intensity by using a Laser Doppler Anemometry (LDA) system. The jet was produced by rotating the propeller at a constant speed powered by an electric motor. The maximum tangential and radial velocities of the six-bladed propeller were of 76% and 17% of the maximum axial velocity respectively. The study found that the six-bladed propeller has a lower tangential velocity, but a higher radial velocity with its own diffusing mechanism when comparing to the three-bladed propeller.

Assessment of sample quality in soft clay using shear wave velocity and suction measurements

The characterisation of soils for civil engineering purposes depends on removing sufficiently high-quality samples from the ground. Accurate evaluation of sample quality is therefore important if reliable design parameters are to be determined. This paper describes the use of unconfined shear wave velocity (V _s) and suction (u _r) measurements to assess sample quality rapidly in soft clay. Samples of varying quality from three well-characterised soft clay sites are initially assessed using conventional techniques, and their results compared with V _s and u _r measurements performed on the same samples. It is observed that the quality of samples indicated by these measurements is very similar to those inferred from traditional disturbance measures, with V _s being the more reliable indicator. A tentative empirically derived criterion, based on samples tested in this project, is proposed to quantify sample disturbance combining both V _s and u _r measurements. Further work using this criterion on different materials is important so as to test its usefulness.

Effect of increasing dietary folate on red-cell folate: Implications for prevention of neural tube defects

Background Recommendations by the UK Department of Health suggest that protection from neural tube defects (NTD) can be achieved through intakes of an extra 400 mu g daily of folate/folic acid as natural food, foods fortified with folic acid, or supplements. The assumption is that all three routes of intervention would have equal effects on folate status.

Methods We assessed the effectiveness of these suggested routes of intervention in optimising folate status. 62 women were recruited from the University staff and students to take part in a 3-month intervention study. Participants were randomly assigned to one of the following five groups: folic acid supplement (400 mu g/day; I); folic-acid-fortified foods (an additional 400 mu g/day; II); dietary folate (an additional 400 mu g/day; III); dietary advice (IV), and control (V). Responses to intervention were assessed as changes in red-cell folate between preintervention and postintervention values.

Findings 41 women completed the intervention study. Red-cell folate concentrations increased significantly over the 3 months in the groups taking folic acid supplements (group I) or food fortified with folic acid (group II) only (p<0.01 for both groups). By contrast, although aggressive intervention with dietary folate (group III) or dietary advice (group IV) significantly increased intake of food folate (p<0.001 and p<0.05, respectively), there was no significant change in folate status.

Interpretation We have shown that compared with supplements and fortified food, consumption of extra folate as natural food folate is relatively ineffective at increasing folate status. We believe that advice to women to consume folate-rich foods as a means to optimise folate status is misleading.