1,210 research outputs found
Towards Novel Nonparametric Statistical Methods and Bioinformatics Tools for Clinical and Translational Sciences
No full textAs the field of functional genetics and genomics is beginning to mature, we become confronted with new challenges. The constant drop in price for sequencing and gene expression profiling as well as the increasing number of genetic and genomic variables that can be measured makes it feasible to address more complex questions. The success with rare diseases caused by single loci or genes has provided us with a proof-of-concept that new therapies can be developed based on functional genomics and genetics. Common diseases, however, typically involve genetic epistasis, genomic pathways, and proteomic pattern. Moreover, to better understand the underlying biologi-cal systems, we often need to integrate information from several of these sources. Thus, as the field of clinical research moves toward complex diseases, the demand for modern data base systems and advanced statistical methods increases. The traditional statistical methods implemented in most of the bioinformatics tools currently used in the novel field of genetics and functional genomics are based on the linear model and, thus, have shortcomings when applied to nonlinear biological systems. The previous work on partially ordered data (Wittkowski 1988; 1992), when combined with theoretical results (Hoeffding 1948) and computational strategies (Deuchler 1914) has opened a new field of nonparametric statistics. With grid technology, new tools are now feasible when screening for interactions between genetics (Wittkowski, Liu 2002) and functional genomics (Wittkowski, Lee 2004). Having more complex study designs and more specific methods available increases the demand for decision support when selecting appropriate bioinformatics tools. With the advent of rapid prototyping systems for Web based database application, we have recently begun to complement previous work on knowledge based systems with graphical Web-based tools for acquisition of DESIGN and MODEL knowledge.Biostatistics Bioinformatics NIH NCRR ROADMAP
Studying travel-related individual assessments and desires by combining hierarchically structured ordinal variables
No full textSubjective mobility, Travel desires, Ordinal variables, Factor analysis, Multidimensional data,
High-pressure free-radical copolymerization of ethene with methacrylic acid and ethene with acrylic acid, 2 - Ethene reactivity ratios
No full textFree-radical copolymerizations of ethylene (E) with methacrylic acid (MAA) and of E with acrylic acid (AA) were carried out in a continuously operated tank reactor at 2000 bar and temperatures up to 280 degrees C. The (M)AA content of the polymer, F-(M)AA, that may be reached by polymerization in homogeneous phase, e.g., at 260 degrees C, is below 10 mol-% and the associated (M)AA content of the monomer mixture is below 1 mol-%. Under such conditions, the ethene and the comonomer reactivity ratios, r(E) and r((M)AA), respectively, can not be simultaneously derived by fitting the measured F-(M)AA and f((M)AA) data according to the classical procedure. With r((M)AA), however, being available from a preceding C-13 NMR study(1)), r(E) may be calculated from each pair of experimental F-(M)AA and f((M)AA) values. F-(M)AA values are determined by means of elemental analysis of carbon and oxygen with consistency checks of copolymer composition brine performed via FT-IR spectroscopy on polymeric films. f((M)AA) is deduced from the measured monomer feed fluxes and from the amount and composition of the copolymer produced within given intervals of stationary polymerization. The r(E) data for the E/MAA and E/AA systems are presented and discussed. At identical polymerization pressure and temperature, the measured r(E) values of both systems agree within about +/-10%. The r(E) values, in addition, are very close to the ethene reactivity ratios that were recently measured for several E/(meth)acrylate copolymerizations. Arguments for this family-type behavior of r(E) are discussed
Report on the ESO Workshop The Origin and Fate of the Sun: Evolution of Solar-mass Stars Observed with High Angular Resolution
No full textThe goal of the workshop was to review recent results on solar-mass stars obtained with infrared and millimetre interferometers, and to discuss their importance for our understanding of stellar evolution from star formation to the late stages. The workshop was preceded by a one-day ALMA+VLTI interferometry primer. A brief summary of the workshop is presented
Variable cant angle winglets for improvement of aircraft flight performance
No full textTraditional winglets are designed as fixed devices attached at the tips of the wings. The primary purpose of the winglets is to reduce the lift-induced drag, therefore improving aircraft performance and fuel efficiency. However, because winglets are fixed surfaces, they cannot be used to control lift-induced drag reductions or to obtain the largest lift-induced drag reductions at different flight conditions (take-off, climb, cruise, loitering, descent, approach, landing, and so on). In this work, we propose the use of variable cant angle winglets which could potentially allow aircraft to get the best all-around performance (in terms of lift-induced drag reduction), at different flight phases. By using computational fluid dynamics, we study the influence of the winglet cant angle and sweep angle on the performance of a benchmark wing at Mach numbers of 0.3 and 0.8395. The results obtained demonstrate that by adjusting the cant angle, the aerodynamic performance can be improved at different flight conditions
Towards Novel Nonparametric Statistical Methods and Bioinformatics Tools for Clinical and Translational Sciences
No full textAs the field of functional genetics and genomics is beginning to mature, we become confronted with new challenges. The constant drop in price for sequencing and gene expression profiling as well as the increasing number of genetic and genomic variables that can be measured makes it feasible to address more complex questions. The success with rare diseases caused by single loci or genes has provided us with a proof-of-concept that new therapies can be developed based on functional genomics and genetics.
Common diseases, however, typically involve genetic epistasis, genomic pathways, and proteomic pattern. Moreover, to better understand the underlying biologi-cal systems, we often need to integrate information from several of these sources. Thus, as the field of clinical research moves toward complex diseases, the demand for modern data base systems and advanced statistical methods increases.
The traditional statistical methods implemented in most of the bioinformatics tools currently used in the novel field of genetics and functional genomics are based on the linear model and, thus, have shortcomings when applied to nonlinear biological systems. The previous work on partially ordered data (Wittkowski 1988; 1992), when combined with theoretical results (Hoeffding 1948) and computational strategies (Deuchler 1914) has opened a new field of nonparametric statistics. With grid technology, new tools are now feasible when screening for interactions between genetics (Wittkowski, Liu 2002) and functional genomics (Wittkowski, Lee 2004).
Having more complex study designs and more specific methods available increases the demand for decision support when selecting appropriate bioinformatics tools. With the advent of rapid prototyping systems for Web based database application, we have recently begun to complement previous work on knowledge based systems with graphical Web-based tools for acquisition of DESIGN and MODEL knowledge
New Statistical Paradigms Leading to Web-Based Tools for Clinical/Translational Science
No full textAs the field of functional genetics and genomics is beginning to mature, we become confronted with new challenges. The constant drop in price for sequencing and gene expression profiling as well as the increasing number of genetic and genomic variables that can be measured makes it feasible to address more complex questions. The success with rare diseases caused by single loci or genes has provided us with a proof-of-concept that new therapies can be developed based on functional genomics and genetics.
Common diseases, however, typically involve genetic epistasis, genomic pathways, and proteomic pattern. Moreover, to better understand the underlying biologi-cal systems, we often need to integrate information from several of these sources. Thus, as the field of clinical research moves toward complex diseases, the demand for modern data base systems and advanced statistical methods increases.
The traditional statistical methods implemented in most of the bioinformatics tools currently used in the novel field of genetics and functional genomics are based on the linear model and, thus, have shortcomings when applied to nonlinear biological systems. The previous work on partially ordered data (Wittkowski 1988; 1992), when combined with theoretical results (Hoeffding 1948) and computational strategies (Deuchler 1914) has opened a new field of nonparametric statistics. With grid technology, new tools are now feasible when screening for interactions between genetics (Wittkowski, Liu 2002) and functional genomics (Wittkowski, Lee 2004).
Having more complex study designs and more specific methods available increases the demand for decision support when selecting appropriate bioinformatics tools. With the advent of rapid prototyping systems for Web based database application, we have recently begun to complement previous work on knowledge based systems with graphical Web-based tools for acquisition of DESIGN and MODEL knowledge
Tests of stellar model atmospheres by optical interferometry
No full textContext: .Optical interferometry allows a measurement of the intensity profile across a stellar disc, leading to a direct test and calibration of theoretical model atmospheres as well as to a precise determination of fundamental stellar parameters. Aims: .We present a comparison of the visual and near-infrared intensity profile of the M0 giant γ Sagittae to plane-parallel ATLAS 9 as well as to plane-parallel and spherical PHOENIX model atmospheres. Methods: .We use previously described visual interferometric data obtained with the Navy Prototype Optical Interferometer (NPOI) in July 2000. We apply the recently developed technique of coherent integration, and thereby obtain visibility data of more spectral channels (526-852 nm) and with higher precision than before. In addition, we employ new measurements of the near-infrared K-band (~2200 nm) diameter of γ Sagittae obtained with the instrument VINCI at the ESO VLT Interferometer (VLTI) in 2002. Results: .The spherical PHOENIX model leads to a precise definition of the Rosseland angular diameter and a consistent high-precision diameter value for our NPOI and VLTI/VINCI data sets of Θ_Ross=6.06 ± 0.02 mas, with the Hipparcos parallax corresponding to R_Ross=55 ± 4~R_☉, and with the bolometric flux corresponding to an effective temperature T_eff=3805 ± 55 K. Our visual visibility data close to the first minimum and in the second lobe constrain the limb-darkening effect and are generally consistent with the model atmosphere predictions. The visual closure phases exhibit a smooth transition between 0 and π. Conclusions: .The agreement between the NPOI and VINCI diameter values increases the confidence in the model atmosphere predictions from optical to near-infrared wavelengths as well as in the calibration and accuracy of both interferometric facilities. The consistent night-by-night diameter values of VINCI give additional confidence in the given uncertainties. The closure phases suggest a slight deviation from circular symmetry, which may be due to surface features, an asymmetric extended layer, or a faint unknown companion...
Diagnostic value of hepatocellular nodule vascularity after microbubble injection for characterizing malignancy in patients with cirrhosis
No full textOBJECTIVE:
The purpose of this study was to assess the diagnostic value of hepatocellular nodule vascularity after microbubble injection for characterization of malignancy in patients with cirrhosis of the liver.
MATERIALS AND METHODS:
After sulfur hexafluoride-filled microbubble injection, the vascularity of 236 hepatocellular nodules (1-5 cm in diameter) in 215 patients with cirrhosis (151 men, 64 women; mean age, 62 +/- 11 [SD] years) was evaluated by consensus of three reference radiologists. The relation between nodule vascularity in the arterial (10-40 seconds from injection) and portal venous (45 seconds to microbubble disappearance) phases and dimension of malignancy was evaluated by multivariate U statistical analysis. Two blinded independent reviewers using reference criteria classified nodules as benign or malignant after review of unenhanced and contrast-enhanced sonograms.
RESULTS:
The final diagnoses were 96 malignant (84 hepatocellular carcinoma, 12 tumors not hepatocellular carcinoma) and 140 benign nodules (57 regenerative and 13 dysplastic nodules, 70 other benign lesions). Nodule hypervascularity during the arterial phase and hypovascularity during the portal venous phase (odds ratio, 27.78) and nodule diameter greater than 2 cm combined with hypervascularity during the arterial phase and isovascularity or hypervascularity during the portal venous phase (odds ratio, 3.3) were related to the presence of malignancy. Contrast-enhanced sonography improved diagnostic accuracy (unenhanced sonography vs contrast-enhanced sonography, 32% vs 71% for reviewer 1 and 22% vs 66% for reviewer 2; p < 0.05, McNemar test) even though hypervascular nodules 2 cm or smaller (malignant, n = 2; benign, n = 40) that appeared isovascular or hypervascular during the portal venous phase were misclassified.
CONCLUSION:
Assessment of hepatocellular nodule vascularity after microbubble injection allowed characterization of malignancy, but characterization was limited for hypervascular nodules 2 cm or less in diameter
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