Spacecraft redesign to reduce microphonic response of a VCO component

Reaction wheel vibration was found to induce out of specification sidebands on the carrier frequencies of some spacecraft components containing mechanical voltage control oscillators (VCOs). Concurrent investigations were performed to redesign the VCOs to reduce their response to the wheel vibration, and to design a reaction wheel isolation system to reduce the vibration input to the affected components. Component level tests indicated that both efforts provided viable solutions. The redesigned VCO will be incorporated into future spacecraft in the series, while affected spacecraft already in production will be retrofitted with the reaction wheel isolation system

Evaluation of serum lipid profile in cases of pre-eclampsia and eclampsia

Background: According to the current knowledge, rise in the serum triglyceride level is a major contributor in the pathogenesis of preeclampsia and eclampsia. The present study was designed to compare the changes in lipid profile in normal pregnancy, pre-eclampsia & eclampsia cases.Methods: A case control study was done consisting of total 100 study subjects, 75 already diagnosed pre-eclamptic & eclamptic women and 25 normotensive pregnant women. Age range was 18-35 years, gestational age 28 weeks to term were included. Serum Total Cholesterol (TC), triglyceride and HDL-cholesterol by enzymatic colorimetric method were done.Results: Results showed that level of serum triglycerides in mild pre-eclampsia (156.22 ± 66.5 mg/dl), severe pre-eclampsia (168.30 ± 68.1 mg/dl) & eclampsia (224.89 ± 84.40 mg/dl) as compared to normal pregnant women (130.95 ± 44.64 mg/dl) was increased significantly (P <0.05). Other parameters TC, HDL-C, LDL-C were not changed significantly.Conclusions: The findings of the present study are consistent with previous studies, suggesting increased levels of serum triglyceride as an important factor in the pathological process of preeclampsia & eclampsia. This may help in developing strategies for prevention or early diagnosis of the disorder

Morphology of the Esophageal Hiatus: Is It Different in 3 Types of Hiatus Hernias?

Background/aimsThe esophageal hiatus is formed by the right crus of the diaphragm in the majority of subjects. Contraction of the hiatus exerts a sphincter-like action on the lower esophageal sphincter (LES). The aim is to study the hiatal anatomy (using CT scan imaging) and function (using high-resolution manometry [HRM]), and esophageal motor function in patients with sliding and paraesophageal hiatal hernia.MethodsWe assessed normal subjects (n = 20), patients with sliding type 1 hernia (n = 18), paraesophageal type 2 hernia (n = 19), and mixed type 3 hernia (n = 19). Hernia diagnosis was confirmed on the upper gastrointestinal series. The hiatal morphology was constructed from the CT scan images. The LES pressure and relaxation, percent peristalsis, bolus pressure, and hiatal squeeze pressure were assessed by HRM.ResultsThe CT images revealed that the esophageal hiatus is formed by the right crus of the diaphragm in all normal subjects and 86% of hernia patients. The hiatus is elliptical in shape with a surface area of 1037 mm2 in normal subjects. The hiatal dimensions were larger in patients compared to normal subjects. The HRM revealed impaired LES relaxation and higher bolus pressure in patients with paraesophageal compared to the sliding hernia. The hiatal pinch on HRM was recognized in significantly higher number of patients with sliding as compared to paraesophageal hernia.ConclusionsUsing a novel approach, we provide details of the esophageal hiatus in patients with various kinds of hiatal hernia. Impaired LES relaxation in paraesophageal hernia may play a role in its pathophysiology and genesis of symptoms

Large-Eddy simulation of pulsatile blood flow

Large-Eddy simulation (LES) is performed to study pulsatile blood flow through a 3D model of arterial stenosis. The model is chosen as a simple channel with a biological type stenosis formed on the top wall. A sinusoidal non-additive type pulsation is assumed at the inlet of the model to generate time dependent oscillating flow in the channel and the Reynolds number of 1200, based on the channel height and the bulk velocity, is chosen in the simulations. We investigate in detail the transition-to-turbulent phenomena of the non-additive pulsatile blood flow downstream of the stenosis. Results show that the high level of flow recirculation associated with complex patterns of transient blood flow have a significant contribution to the generation of the turbulent fluctuations found in the post-stenosis region. The importance of using LES in modelling pulsatile blood flow is also assessed in the paper through the prediction of its sub-grid scale contributions. In addition, some important results of the flow physics are achieved from the simulations, these are presented in the paper in terms of blood flow velocity, pressure distribution, vortices, shear stress, turbulent fluctuations and energy spectra, along with their importance to the relevant medical pathophysiology

Influence of Microstructure on Mechanical Properties of Snow

Snow, being composed of ice grains of varying shapes, sizes, orientations, etc., has been treated as a particulate material. The mechanical properties of snow have been described in terms of microstructural parameters. A set of variables, which characterise the microstructure of snow at the granular level, has been chosen and quantified following the techniques of quantitative stereology for section plane. The data of quasi-static tests, e.g. constant strain-rate creep tests, have been analysed to determine the Young's modulus and compactive viscosity and the same have been correlated with the microstructural parameters. Inspite of scatter, definite trends are discernible. Considering the fact that deformation of snow is associated with translation and rotation of constituent grains in such a way as to attain the most stable configuration, the concept of fabric reconstruction, which is characterised by the concentration of normals (to the tangent plane at the point of grain contact) in the direction of the applied load, has been examined. The results demonstrated the occurrence of fabric reconstruction during the process of deformation. Finally, a dimensionless quantity, called the microstructural index (I), has been proposed to adequately represent the influence of microstructure