Formulation of boundary conditions for the multigrid acceleration of the Euler and Navier Stokes equations

An explicit, Multigrid algorithm was written to solve the Euler and Navier-Stokes equations with special consideration given to the coarse mesh boundary conditions. These are formulated in a manner consistent with the interior solution, utilizing forcing terms to prevent coarse-mesh truncation error from affecting the fine-mesh solution. A 4-Stage Hybrid Runge-Kutta Scheme is used to advance the solution in time, and Multigrid convergence is further enhanced by using local time-stepping and implicit residual smoothing. Details of the algorithm are presented along with a description of Jameson's standard Multigrid method and a new approach to formulating the Multigrid equations

Skin blood flow changes during apneic spells in preterm infants

Changes in skin blood flow during apneic spells were determined in 18 preterm infants using a diode laser Doppler flow meter without light conducting fibres. Heart rate, nasal air flow, impedance pneumography, skin and incubator temperature and laser Doppler skin blood flow were recorded simultaneously in each infant. During 212 apneic spells with a duration of 11.6 ± 7.5 s (mean ± S.D.) (range 6.0–48.0 s), the laser Doppler skin blood flow was measured. In all children except one, the majority of the apneic spells was associated with a decrease in skin blood flow. During 155 apneic spells (73%) skin blood flow decreased significantly P < 0.025), the maximum decrease being 16.7 ± 14.8%, 28.5 ± 23.9% and 18.9 ± 16.1% (mean ± S.D.) for central, obstructive and mixed apneic spells, respectively. The decrease in skin blood flow started immediately after the beginning of apneic spells in 71%, the rest started with a mean delay of 3.4 s (range 0.1–7.0 s). No relation was found between the decrease in skin blood flow and the duration of the apneic spells. Thirty-four percent of the apneic spells were accompanied by bradycardia. In apneic spells accompanied by bradycardia the decrease in skin blood flow was not related to the fall in heart rate

A compact differential laser Doppler velocimeter using a semiconductor laser

A small differential laser Doppler velocimeter which uses a semiconductor laser and a small number of optical components is described. In this device the light from the laser diode is split into coherent beams by means of a diffraction grating. The two first-order beams are crossed in a probe volume with a lens. In a test experiment the velocity of water containing 0.9 mu m polystyrene spheres was determined from the fluctuation of the scattered light. This velocity agreed with the velocity calculated from flux measurements

ABORAS: polarimetric, 10cm/s RV observations of the Sun as a star

We present a description of A dual-Beam pOlarimetric Robotic Aperture for the Sun (ABORAS), to serve as a Solar input with a dedicated Stokes V polarimeter for the HARPS3 high-resolution spectrograph. ABORAS has three main science drivers: trying to understand the physics behind stellar variability, tracking the long-term stability of HARPS3, and serve as a benchmark for Earth-sized exoplanet detection with HARPS3 by injecting an Earth RV signal into the data. By design, ABORAS will (together with the HARPS3 instrument) be able to measure 10cm/s variations in RV of the integrated Solar disk and detect integrated magnetic field levels at sub 1 Gauss level through circularly polarized light.Comment: 8 pages, 5 figures, SPIE Proceedings pre-print, draft version

Economic burden of neural tube defects and impact of prevention with folic acid: a literature review

Neural tube defects (NTDs) are the second most common group of serious birth defects. Although folic acid has been shown to reduce effectively the risk of NTDs and measures have been taken to increase the awareness, knowledge, and consumption of folic acid, the full potential of folic acid to reduce the risk of NTDs has not been realized in most countries. To understand the economic burden of NTDs and the economic impact of preventing NTDs with folic acid, a systematic review was performed on relevant studies. A total of 14 cost of illness studies and 10 economic evaluations on prevention of NTDs with folic acid were identified. Consistent findings were reported across all of the cost of illness studies. The lifetime direct medical cost for patients with NTDs is significant, with the majority of cost being for inpatient care, for treatment at initial diagnosis in childhood, and for comorbidities in adult life. The lifetime indirect cost for patients with spina bifida is even greater due to increased morbidity and premature mortality. Caregiver time costs are also significant. The results from the economic evaluations demonstrate that folic acid fortification in food and preconception folic acid consumption are cost-effective ways to reduce the incidence and prevalence of NTDs. This review highlights the significant cost burden that NTDs pose to healthcare systems, various healthcare payers, and society and concludes that the benefits of prevention of NTDs with folic acid far outweigh the cost. Further intervention with folic acid is justified in countries where the full potential of folic acid to reduce the risk of NTDs has not been realized