1,722,181 research outputs found
Novel optical fibre distributed temperature sensor based on the Landau-Placzek ratio
Get PDFWe report our latest results on a compact, diode pumped optical fibre distributed temperature sensor based on Brillouin scattering. A high power, short pulse Q-switched Erbium/Ytterbium fibre laser and a double pass in-fibre Mach-Zehnder interferometer make this Brillouin distributed temperature sensor an attractive commercial device. A spatial and temperature resolution of 10 metres and + or - 1.7°C has been demonstrated
A Dog in the Synagogue!
No full textLetter to Rabbi N. Frankenstein, regarding a wealthy women who apparently came to synagogue with her dog. Rabbi Placzek informs Rabbi Frankenstein that such behavior cannot be tolerated. The reply denies the affair.digitizedScott Offen Fund in Memory of Herbert Offen10439 [Ms.] R. Abraham Placzek, A Dog in the Synagogue!, Boskovice, Moravia, c. 1860[1] p., 130:203 mm., light age staining, Ashkenazic script, signed and dated.Abraham Placzek (1799—1884) was Landesrabbiner of Moravia. From 1840 until his death he was rabbi in Boskowitz (today Boskovice). Rabbi Placzek was an outstanding talmudic scholar and strictly orthodox, but he attempted to avoid open conflicts between the factions in Moravia.Source for 545: E
Kaethe Placzek Collection 1894-1931 Bulk dates: 1907-1920
No full textThe Kaethe Placzek Collection focuses on the family life of Kaethe Spiegel née Placzek, and especially on several years in the lives of Hermann and Melvine Placzek and Julian Spiegel. This collection consists entirely of correspondence, both that sent to Kaethe by her own family and that sent by Julian Spiegel. Prominent topics include spa treatments and culture in the early twentieth century and Julian Spiegel’s World War I experiences.Käthe Placzek was the daughter of Hermann and Malvine Placzek. In November 1919 she married Julian Spiegel.Julian Spiegel was born in England in 1884, the son of Felix and Sophie (née Ohlmann) Spiegel, and had two siblings, Percy and Helen. He designed airplanes for the aviation firm Rumpler-Werke AG.Julian and Käthe had one son, Walter.Kaethe Placzek was Karen Spiegel Franklin's grandmotherProcesseddigitize
Ab initio wavelength-dependent raman spectra: Placzek approximation and beyond
No full text576586We analyze how to obtain non-resonant and resonant Raman spectra within the Placzek as well as the Albrecht approximation. Both approximations are derived from the matrix element for light scattering by application of the Kramers, Heisenberg, and Dirac formula. It is shown that the Placzek expression results from a semi-classical approximation of the combined electronic and vibrational transition energies. Molecular hydrogen, water, and butadiene are studied as test cases. It turns out that the Placzek approximation agrees qualitatively with the more accurate Albrecht formulation even in the resonant regime for the excitations of single vibrational quanta. However, multiple vibrational excitations are absent in Placzek but can be of similar intensities to single excitations under resonance conditions. The Albrecht approximation takes multiple vibrational excitations into account, and the resulting simulated spectra also exhibit good agreement with experimental Raman spectra in the resonance region.16
Lastverteilung und Flankenkorrektur in gerad[verzahnten] und schrägverzahnten Stirnradstufen
No full textThe Landau-Placzek ratio for multicomponent fluids
Get PDFUnder the assumption that the coupling between the sound modes and modes associated with heat and mass diffusion can be neglected, an expression for the Landau-Placzek ratio for multicomponent fluids is derived using thermodynamic fluctuation theory. Applications of the general formula to ternary systems arc discussed briefly
A conditional error function approach for adaptive enrichment designs with continuous endpoints
No full textAdaptive enrichment designs offer an efficient and flexible way to demonstrate the efficacy of a treatment in a clinically defined full population or in, eg, biomarker‐defined subpopulations while controlling the family‐wise Type I error rate in the strong sense. Frequently used testing strategies in designs with two or more stages include the combination test and the conditional error function approach. Here, we focus on the latter and present some extensions. In contrast to previous work, we allow for multiple subgroups rather than one subgroup only. For nested as well as nonoverlapping subgroups with normally distributed endpoints, we explore the effect of estimating the variances in the subpopulations. Instead of using a normal approximation, we derive new t ‐distribution–based methods for two different scenarios. First, in the case of equal variances across the subpopulations, we present exact results using a multivariate t ‐distribution. Second, in the case of potentially varying variances across subgroups, we provide some improved approximations compared to the normal approximation. The performance of the proposed conditional error function approaches is assessed and compared to the combination test in a simulation study. The proposed methods are motivated by an example in pulmonary arterial hypertension.Bundesministerium für Bildung und Forschung https://doi.org/10.13039/501100002347Deutsches Zentrum für Herz-Kreislaufforschung https://doi.org/10.13039/10001044
Clinical trials with nested subgroups: Analysis, sample size determination and internal pilot studies
No full text The importance of subgroup analyses has been increasing due to a growing interest in personalized medicine and targeted therapies. Considering designs with multiple nested subgroups and a continuous endpoint, we develop methods for the analysis and sample size determination. First, we consider the joint distribution of standardized test statistics that correspond to each (sub)population. We derive multivariate exact distributions where possible, providing approximations otherwise. Based on these results, we present sample size calculation procedures. Uncertainties about nuisance parameters which are needed for sample size calculations make the study prone to misspecifications. We discuss how a sample size review can be performed in order to make the study more robust. To this end, we implement an internal pilot study design where the variances and prevalences of the subgroups are reestimated in a blinded fashion and the sample size is recalculated accordingly. Simulations show that the procedures presented here do not inflate the type I error significantly and maintain the prespecified power as long as the sample size of the smallest subgroup is not too small. We pay special attention to the case of small sample sizes and attain a lower boundary for the size of the internal pilot study. </jats:p
Rayleigh-Brillouin Light Scattering from Noble Gas Mixtures. 1. The Landau-Placzek Ratio
Get PDFWe present the Rayleigh-Brillouin light scattering data for He + Xe mixtures of various compositions and pressures between 2 and 10 MPa. We compare our experimental data to calculations for a mixture that behaves according to the van der Waals equation of state. Our analysis shows that the contribution of concentration fluctuations to the Landau-Placzek ratio is very important. Furthermore, we demonstrate experimentally the relation between the Landau-Placzek ratio, the adiabatic velocity of sound, and the reduced second moment of the dynamic light scattering spectrum. We show that the van der Waals equation of state can be used to predict the Landau-Placzek ratio in these mixtures quantitatively for mixtures with compositionsxu < 0.9. For mixtures with higher xenon concentrations, experimental results agreed quantitatively up to 5 MPa with calculations
Landau Placzek ratio applied to distributed fibre sensing
No full textIt is shown experimentally that the ratio of the intensities of Rayleigh and Brillouin backscattered light (Landau Placzek ratio) in an optical fibre has a temperature dependence which may be used for the basis of a distributed temperature sensor. This result, combined with the known frequency dependence of be Brillouin backscattering on temperature and strain, indicates that spontaneous Brillouin backscatter may be used for the unique determination of either temperature or strain in a distributed optical fibre sensing system
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