Techniques in X-ray astronomy

X-ray astronomy has benefited enormously with the deployment of imaging X-ray telescopes in space, leading to a veritable revolution. Such telescopes require distortion free focusing of X-rays and the use of position sensitive X-ray detectors. In this article I shall describe the importance of X-ray imaging, the optical principles behind the creation of images and the instruments based on these principles. The various techniques used to fabricate such X-ray telescopes are described briefly. The many types of detectors used in X-ray astronomy will be described in the second part of this article in a subsequent issue ofResonance. Kulinder Pal Singh is in the Department of Astronomy and Astrophysics of the Tata Institute of Fundamental Research, Mumbai. His primary fields of research are X-ray studies of hot plasmas in stars, supernova remnants, galaxies, intergalactic medium in clusters of galaxies, active galactic nuclei, cataclysmic variables and X-ray binaries. He is leading the development of a soft X-ray imaging telescope for the ASTROSAT mission to be launched by India in 2007–2008.     

Bilingual Infants Demonstrate Advantages in Learning Words in a Third Language

Prior research suggests that bilingualism may endow infants with greater phonological flexibility. This study investigated whether this flexibility facilitates word learning in additional languages (n = 96). Experiment 1 compared 18‐ to 20‐month‐old monolingual (English) and bilingual (English/Mandarin) infants on their ability to learn words distinguished by click consonants from a Southern African language, Ndebele. English–Mandarin bilingual infants were sensitive to Ndebele click contrasts, but monolingual English infants were not. In Experiments 2a and 2b, we investigated whether enhanced bilingual sensitivity extended to analogous nonlinguistic labels: hand claps and finger snaps. Although discriminated by infants, neither group distinguished words labeled by hand claps and finger snaps. Results suggest that bilingual infants' sustained openness to non native contrast may facilitate the uptake of words in distant languages.     

Recent insights on biochemical and molecular basis for developing antihaemostatic agents: A review

The normal coagulation process is initiated by disruption and exposure of the subendothelial components of blood vessels. Platelets adhere to subendothelium-bound von Willebrand factor via glycoprotein (GP) Ib complex. This initial interaction per se and the release of platelet agonists transduce signals that leads to the rise in intracellular Ca2+ which induces shape change, prostaglandin synthesis, release of granular contents and conformational changes in platelet Gp IIb-IIIa. Gp IIb-IIIa in activated platelets binds fibrinogen and other adhesive proteins and mediates platelet cohesion the primary haemostatic plug. Furthermore, the activated platelets due to aggregation, result in the formation of fibrin (secondary hemostasis). Normally the haemostatic process plays a delicate balance between keeping the blood in the fluid state to maintain flow and rapidly forming an occluding plug following vessel injury. Thrombosis occurs because of alteration in this delicate balance. Arterial thrombosis occurs in the setting of previous vessel wall injury mostly because of atherosclerosis, while venous thrombosis occurs in areas of stasis. The recent advances in understanding of the haemostatic process have led to a better understanding of the mechanism of action of many antithrombotic drugs and identification of new targets for drug development. The molecular target of the ticlopidine has been identified. Large numbers of IIb-IIIa inhibitors have been developed. The mechanism of action of heparin has been defined at the molecular level. As a result, a synthetic pentasaccharide, based on antithrombin-binding domain of heparin, has been developed and tested successfully in clinical trials. New generation direct thrombin inhibitors are being developed. Factor Xa has a critical position at the convergence of intrinsic and extrinsic pathway. The clinical tolerability and the efficacy of low molecular weight heparins has established that inhibition of further thrombin generation, by blocking factor Xa alone can be an effective way of preventing thrombus growth without inactivating thrombin. A large number of specific factor Xa inhibitors are under development. Some of these are in preliminary clinical trials and appear to be promising. Future clinical trials will determine whether these new drugs will provide better risk-benefit ratio in treatment of thrombotic disorders. Similarly role of thrombolytics has been clearly established in many diseases including coronary artery disease.     

Effect of feeding Carica papaya (Papita) fruits on blood lipid profile of albino rabbits

Effect of feeding ripe and unripe papaya fruit pulps were investigated on blood lipid profile of normal male adult albino rabbits by giving them pulps separately at the dose of 15 and 30g per day along with standard diet over a period of six weeks. As compared to controls both fruit pulps resulted in highly significant (p<0.001) and consistent lowering of serum cholesterol, low density lipoprotein cholesterol and triglycerides and elevation in phospholipids and high density lipoprotein cholesterol levels at 1,3 and 6 weeks of fruit pulp feeding indicating a dose dependent effect. Observations clearly support medicinal value ofC. Papaya in the management of atherosclerosis, fatty liver, ischaemic changes and consequential myocardial infarction.     

Assessment of renal acidification capacity of stone formers by acid challenge test

Acid challenge test was carried out on 87 subjects (37 normal and 50 radiologically proven stone formers) to assess their renal acidification capacity. NS were given three doses viz. 75, 100 and 150 mg NH₄Cl/Kg body weight while the SF were tested with only 150 mg dose which was found to be an adequate dose. Ammonium chloride was given in gelatin capsules with breakfast and hourly urine samples were collected for next 7 hours. pH, creatinine, calcium, inorganic phosphorus, citrate, titrable acid and ammonium were analysed in all the samples. The incidence of renal tubular acidosis (RTA) in NS, tested with 75 mg and 100 mg/kg doses of ammonium chloride, was 50% and 10% respectively while it was nil and 24% respectively in NS and SF tested with 150mg/kg dose. Complete RTA was detected in one SF. No significant difference was observed in urinary profile of NS and SF except that the hourly titrable acid excretion was lower in later. A comparison between with and without RTA SF revealed that titrable acid and phosphate excretion decreased in RTA defect. Overall data indicate that (a) RTA was an etiologic factor in one fourth of the SF; (b) an oral acid challenge test is a good adjunct to detect this condition and (c) acid challenge increases calcium, phosphate and titrable acid excretion and decreases citrate.     

Effect of l-Arginine on Nitric Oxide Levels in Intrauterine Growth Restriction and its Correlation with Fetal Outcome

The current management of intrauterine growth restriction (IUGR) being empirical and aimed at selecting a safe time for delivery. Acknowledging the beneficial effects of l-arginine on endothelial vasculature the present study was designed to evaluate efficacy of l-arginine on bioavailability of nitric oxide (NO) with respect to fetal outcome. With l-arginine supplementation, mean NO levels were significantly increased and a significant mild reduction in systolic/end-diastolic velocity ratio (S/D ratio) was observed on doppler blood flow study, also neonatal outcome improved and incidences of complications were lowered. A deficiency in NO may play an important role in the causation of asymmetric fetal growth restriction. l-Arginine can be used to increase maternal NO levels, enhancing birth weight and decreasing neonatal morbidity. The ideal candidate for arginine therapy according to our study would be IUGR cases with S/D ratio less than 4.96 ± 0.49 and NO levels below 33 μmol/L with minimum of 3 weeks duration of arginine supplementation.     

Association of Resistin with Insulin Resistance and Factors of Metabolic Syndrome in North Indians

Metabolic syndrome (MetS) is a cluster of interrelated common clinical disorders. The role of resistin in insulin sensitivity and MetS is controversial till date. So, the aim of the present study was to investigate the relationship of plasma resistin levels with markers of the MetS in Indian subjects. In a case control study, total 528 subjects were selected for the study. 265 (194 male and 71 female) were cases (with MetS) and 263 (164 male and 99 female) were controls (without MetS). Required anthropometric measurements and calculations were carried out accordingly. All the Biochemical estimations were carried out according to standard protocol. Resistin level was measured by the standard protocol (By ELISA i.e. enzyme linked immunosorbent assay) as illustrated in the kit. Insulin level was also measured by the standard protocol as illustrated in the kit and insulin resistance was calculated by the standard procedures. Plasma resistin levels were significantly higher in cases compared with controls (male = 13.05 ± 4.31 vs. 7.04 ± 2.09 ng/ml; p ≤ 0.001 and female = 13.53 ± 4.14 vs. 7.42 ± 2.30 ng/ml; p ≤ 0.001). Plasma resistin levels were well correlated with waist circumference, glucose, triglycerides, waist/hip ratio, systolic and diastolic blood pressure, high density lipoprotein, total cholesterol, serum low density lipoprotein, serum very low density lipoprotein, insulin and insulin resistance. Plasma resistin levels were elevated in presence of the MetS and were associated with increased metabolic risk factors.     

Urinary Organic Acids Quantitated in a Healthy North Indian Pediatric Population

Human urine gives evidence of the metabolism in the body and contains numerous organic acids and other compounds at a variety of concentration. The concentration of organic acids in urine varies from population to population due to genotype, food habits and other epigenetic and environmental influences. Knowledge of the reference values for urinary organic acids in a healthy pediatric population is very important for critical evaluation. This study was designed to quantify 16 organic acids in a healthy north Indian pediatric population. Early morning urine samples from healthy pediatric subjects of age 1 day to 16 years who did not have symptoms of any disease were analyzed for organic acid content. The children were not on any supplemental vitamins or drugs and were on a free and unrestricted diet. The creatinine concentration of each sample was determined before organic acid analysis. Organic acids were extracted from urine with ethyl acetate, extracted residue was air dried, converted into trimethylsilyl derivatives and analysed by gas chromatography mass spectrometry. Here we reported the age wise mean values and standard deviations for each compound, adjusted for creatinine content (mmol/mol of creatinine). We found the concentration of most of the metabolites are higher in our population in comparison to other populations. Such data may help to provide a basis for diagnosing metabolic abnormalities in patients in a specific ethnicity.     

Back to Basics: A Bilingual Advantage in Infant Visual Habituation

Comparisons of cognitive processing in monolinguals and bilinguals have revealed a bilingual advantage in inhibitory control. Recent studies have demonstrated advantages associated with exposure to two languages in infancy. However, the domain specificity and scope of the infant bilingual advantage in infancy remains unclear. In the present study, 114 monolingual and bilingual infants were compared in a very basic task of information processing—visual habituation—at 6 months of age. Bilingual infants demonstrated greater efficiency in stimulus encoding as well as in improved recognition memory for familiar stimuli as compared to monolinguals. Findings reveal a generalized cognitive advantage in bilingual infants that is broad in scope, early to emerge, and not specific to language.     

Positioning in groups: a new development in systemic consultation

This article describes a new approach, employing a combination of Positioning Theory and Semantic Polarities, that educational psychologists can use to develop and facilitate change in organisations and groups. Resistance to change can be seen as reflecting a lack of the language that the members of an organisation need to participate effectively in the new discourses that are associated with change. Positioning Theory can be used to develop this new language of participation, which can then be used by all in the organisation or group to agree how development can happen and what their contribution to this would be.