8 research outputs found

    Multiple light scattering in nematic liquid crystals

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    We present a rigorous treatment of the diffusion approximation for multiple light scattering in anisotropic random media, and apply it to director fluctuations in a nematic liquid crystal. For a typical nematic material, 5CB, we give numerical values of the diffusion constants D‚ą•D_{\|} and D‚ä•D_{\perp}. We also calculate the temporal autocorrelation function measured in Diffusing Wave Spectroscopy.Comment: 5 pages RevTeX, 1 postscript figure, to be published in Phys. Rev. E (Rapid Communication

    Multiple light scattering in anisotropic random media

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    In the last decade Diffusing Wave Spectroscopy (DWS) has emerged as a powerful tool to study turbid media. In this article we develop the formalism to describe light diffusion in general anisotropic turbid media. We give explicit formulas to calculate the diffusion tensor and the dynamic absorption coefficient, measured in DWS experiments. We apply our theory to uniaxial systems, namely nematic liquid crystals, where light is scattered from thermal fluctuations of the local optical axis, called director. We perform a detailed analysis of the two essential diffusion constants, parallel and perpendicular to the director, in terms of Frank elastic constants, dielectric anisotropy, and applied magnetic field. We also point out the relevance of our results to different liquid crystalline systems, such as discotic nematics, smectic-A phases, and polymer liquid crystals. Finally, we show that the dynamic absorption coefficient is the angular average over the inverse viscosity, which governs the dynamics of director fluctuations.Comment: 23 pages, 12 ps figures, to be published in Phys. Rev.

    New genetic loci link adipose and insulin biology to body fat distribution.

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    Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

    Value of risk scores in the decision to palliate patients with ruptured abdominal aortic aneurysm

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    Background: The aim of this study was to develop a 48-h mortality risk score, which included morphology data, for patients with ruptured abdominal aortic aneurysm presenting to an emergency department, and to assess its predictive accuracy and clinical effectiveness in triaging patients to immediate aneurysm repair, transfer or palliative care. Methods: Data from patients in the IMPROVE (Immediate Management of the Patient With Ruptured Aneurysm: Open Versus Endovascular Repair) randomized trial were used to develop the risk score. Variables considered included age, sex, haemodynamic markers and aortic morphology. Backwards selection was used to identify relevant predictors. Predictive performance was assessed using calibration plots and the C-statistic. Validation of the newly developed and other previously published scores was conducted in four external populations. The net benefit of treating patients based on a risk threshold compared with treating none was quantified. Results: Data from 536 patients in the IMPROVE trial were included. The final variables retained were age, sex, haemoglobin level, serum creatinine level, systolic BP, aortic neck length and angle, and acute myocardial ischaemia. The discrimination of the score for 48-h mortality in the IMPROVE data was reasonable (C-statistic 0·710, 95 per cent c.i. 0·659 to 0·760), but varied in external populations (from 0·652 to 0·761). The new score outperformed other published risk scores in some, but not all, populations. An 8 (95 per cent c.i. 5 to 11) per cent improvement in the C-statistic was estimated compared with using age alone. Conclusion: The assessed risk scores did not have sufficient accuracy to enable potentially life-saving decisions to be made regarding intervention. Focus should therefore shift to offering repair to more patients and reducing non-intervention rates, while respecting the wishes of the patient and family

    International Social Survey Programme: Work Orientations II - ISSP 1997

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    Einstellung zur Arbeit. Arbeitsorientierung und Beschreibung derArbeitsinhalte. Themen: Gew√ľnschte Zeitaufteilung f√ľr ausgew√§hlte T√§tigkeiten wieArbeit, Freizeit usw.; Arbeitsorientierung (Skala); Erledigung vonArbeiten im Haushalt; Wichtigkeit ausgew√§hlter Anspr√ľche an einenArbeitsplatz; wichtigste Kriterien f√ľr die Bestimmung der Gehaltsh√∂he;Einflu√ü neuer Technologien auf Arbeitsplatzangebot und aufArbeitsplatzqualit√§t; Pr√§ferenz f√ľr die Arbeit im Dienstleistungsbereichoder in der Industrie sowie in der Privatwirtschaft oder im √∂ffentlichenSektor; Pr√§ferenz f√ľr Arbeitsnehmerstatus oder beruflicheSelbst√§ndigkeit sowie f√ľr das Arbeiten in einem Gro√üunternehmen oder ineinem kleinen Unternehmen; Teilzeitbesch√§ftigung; Interesse an einerVollzeitbesch√§ftigung; erwartete Schwierigkeiten bei einer Jobsuche;Bezahlung der Arbeit; Beschreibung des eigenen Engagements bei derArbeit; Pr√§ferenz f√ľr mehr Arbeit und mehr Lohn oder f√ľr mehr Freizeit;Sicherheit des eigenen Arbeitsplatzes; Bedeutung vonKarrierem√∂glichkeiten und flexibler Arbeitszeitgestaltung;Charakterisierung der Arbeit als harte physische T√§tigkeit undBeschreibung des Ausma√ües von Stre√ü bei der Arbeit; physischeErsch√∂pfung nach der Arbeit; gef√§hrliche und ungesundeArbeitsplatzsituationen; eigene Einflu√üm√∂glichkeit auf die Gestaltungdes Arbeitstages bzw. der Arbeitsabl√§ufe; allgemeineArbeitsplatzbeschreibung; Nutzen der erlernten F√§higkeiten aus derSchul- oder Universit√§tszeit; Beurteilung des Verh√§ltnisses zwischenManagement und Mitarbeitern; Betriebsklima; Arbeitszufriedenheit;Abwesenheit in den letzten 6 Monaten; Suche nach neuer Arbeit in denn√§chsten 12 Monaten. Nichterwerbst√§tige wurden gefragt: Arbeit f√ľr mehr als ein Jahr undZeitpunkt des Endes der letzten bezahlten Arbeit; Gr√ľnde f√ľr das Endeder Besch√§ftigung; erwartete Schwierigkeiten bei der Jobsuche; momentaneSuche nach Arbeit; Art der Arbeitssuche; Haupteinkommensquelle. Demographie: Geschlecht; Alter; Familienstand; Zusammenleben mit einemPartner; Ausbildung und Ausbildungsdauer; momentanerBesch√§ftigungsstatus; Besch√§ftigung im privaten oder √∂ffentlichenSektor; Selbst√§ndigkeit bzw. Arbeitsverh√§ltnis; eigene Angestellte;Wochenarbeitszeit; Vorgesetztenfunktion und Kontrollspanne;Betriebsgr√∂√üe; Einkommen; Konfession; Religiosit√§t;Gewerkschaftsmitglied; Selbsteinsch√§tzung der Schichtzugeh√∂rigkeit;Selbsteinsch√§tzung auf einem Links-Rechts-Kontinuum; Parteipr√§ferenz;Haushaltsgr√∂√üe und Zusammensetzung; Ortsgr√∂√üe; Region; urspr√ľnglichesHerkunftsland bzw. ethnische Gruppenzugeh√∂rigkeit

    Defining the role of common variation in the genomic and biological architecture of adult human height

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    Using genome-wide data from 253,288 individuals, we identified 697 variants at genome-wide significance that together explained one-fifth of the heritability for adult height. By testing different numbers of variants in independent studies, we show that the most strongly associated ‚ąľ2,000, ‚ąľ3,700 and ‚ąľ9,500 SNPs explained ‚ąľ21%, ‚ąľ24% and ‚ąľ29% of phenotypic variance. Furthermore, all common variants together captured 60% of heritability. The 697 variants clustered in 423 loci were enriched for genes, pathways and tissue types known to be involved in growth and together implicated genes and pathways not highlighted in earlier efforts, such as signaling by fibroblast growth factors, WNT/ő≤-catenin and chondroitin sulfate-related genes. We identified several genes and pathways not previously connected with human skeletal growth, including mTOR, osteoglycin and binding of hyaluronic acid. Our results indicate a genetic architecture for human height that is characterized by a very large but finite number (thousands) of causal variants

    Genetic studies of body mass index yield new insights for obesity biology