bluuebunny/crossref_metadata_2025 huggingface dataset:
On the prognostic value of survival models with application to gene expression signatures
Authors: Hielscher T. , Zucknick M. , Werft W. , Benner A.
Published: March 2010

As part of the validation of any statistical model, it is a good statistical practice to quantify the prediction accuracy and the amount of prognostic information represented by the model; this includes gene expression signatures derived from high‐dimensional microarray data. Several approaches exist for right‐censored survival data measuring the gain in prognostic information compared with established clinical parameters or biomarkers in terms of explained variation or explained randomness. They are either model‐based or use estimates of prediction accuracy.

As these measures differ in their underlying mechanisms, they vary in their interpretation, assumptions and properties, in particular in how they deal with the presence of censoring. It remains unclear, under what conditions and to what extent they are comparable. We present a comparison of several common measures and illustrate their behaviour in high‐dimensional situations in simulation examples as well as in applications to real gene expression microarray data sets. An overview of available software implementations in R is given. Copyright © 2010 John Wiley & Sons, Ltd.
Statistical models for heart rate correction of the QT interval
Authors: Ring Arne
Published: March 2010

The analysis of QT interval data is now an essential part of the assessment of drug safety. As the QT interval is inversely associated with heart rate, an appropriate correction must be applied in order to evaluate QT data in clinical trials. The aim is to characterize changes in QT interval at a standard heart rate, taking into account the correlation between these two variables to adjust for heart rate changes during the course of the trial. It has been shown that the relationship between the RR interval (=1/heart rate) and the QT interval is highly variable between individuals but stable over time within each individual.

Many mathematical models have been developed to describe the QT–RR relationship. However, there has been less emphasis on the derivation of suitable statistical models that account for the multilevel structure of the ECG data.

An important example is the interpretation of the so‐called population‐specific heart rate corrections, which are based on data pooled from different subjects. Often, simple regression techniques are used to quantify the population correction, disregarding the subject level and leading to biased parameter estimates. Instead, population‐based corrections that account for individual intercepts should be used, in order to distinguish within‐subject‐effects from between‐subject effects. Therefore, population‐specific corrections cannot be derived solely from the cross‐sectional data. The impact of the different statistical models is illustrated by data from the baseline periods of six clinical QT studies. Copyright © 2010 John Wiley & Sons, Ltd.
Burnout as an important factor in the psychophysiological responses to a work day in Teachers
Authors: Moya‐Albiol Luis , Serrano Miguel Ángel , Salvador Alicia
Published: March 2010

Burnout syndrome is an important psychosocial risk in the job context, especially in professions with a strong social interaction, as in the case of teaching. This study analyses the role of burnout in the psychophysiological responses to a work day in teachers. High burnout was related to worse mood, and higher perceived stress throughout the work day. Moreover, burnout is positively related to systolic blood pressure and negatively related to salivary cortisol levels at the beginning of the work day. Higher scores of burnout in teachers are also related to lower heart rate in the middle of the work day. The psychophysiological responses to a work day are specifically associated with the different burnout subscales (emotional exhaustion, depersonalization and personal accomplishment). Men presented higher diastolic blood pressure than women at the beginning and the middle of the work day. Burnout could induce an alteration in mood together with a dysregulation of the cardiovascular activity and the hypothalamo‐pituitary‐adrenocortical axis functioning in response to a work day in teachers. Moreover, our results offer different burnout‐dependent patterns of relationships between psychological, cardiovascular and cortisol responses, and they suggest that gender plays a moderator role in the cardiovascular response to a work day. Copyright © 2010 John Wiley & Sons, Ltd.
Entrepreneurial finance meets organizational reality: comparing investment practices and performance of corporate and independent venture capitalists
Authors: Dushnitsky Gary , Shapira Zur
Published: March 2010

This paper investigates the effect of compensation of corporate personnel on their investment in new technologies. We focus on a specific corporate activity, namely corporate venture capital (CVC), describing minority equity investment by established‐firms in entrepreneurial ventures. The setting offers an opportunity to compare corporate investors to investment experts, the independent venture capitalists (IVCs). On average, we observe a performance gap between corporate investors and their independent counterparts. Interestingly, the performance gap is sensitive to CVCs' compensation scheme: it is the largest when CVC personnel are awarded performance pay. Not only do we study the association between incentives and performance but we also document a direct relationship between incentives and the actions managers undertake. For example, we observe disparity between the number of participants in venture capital syndicates that involve a corporate investor, and those that consist solely of IVCs. The disparity shrinks substantially, however, for a subset of CVCs that compensate their personnel using performance pay. We find a parallel pattern when analyzing the relationship between compensation and another investment practice, staging of investment. To conclude, the paper investigates the three elements of the principal‐agent framework, thus providing direct evidence that compensation schemes (incentives) shape investment practices (managerial action), and ultimately investors' outcome (performance). Copyright © 2010 John Wiley & Sons, Ltd.
‘Keep out’ signs: the role of deterrence in the competition for resources
Authors: Clarkson Gavin , Toh Puay Khoon
Published: March 2010

To explain resource heterogeneity, past research focuses on how rivals' resources are hidden from firms and firms accordingly have difficulties accessing them. We argue that resource heterogeneity may also arise when firms are deterred from a technological space upon being shown what resources rivals already possess within that space. To illustrate this deterrence effect, we use patent reexamination certificates, which indicate strategic stakes within a technological space without materially disclosing additional details of the underlying technologies and hence avoid the confounding effect of attracting competition through disclosure. We demonstrate how rivals' reexamination certificates within a technological space induce a firm to subsequently allocate less inventive effort in that space, based on two mechanisms—indications of rivals' developmental speed and exclusionary ability. We further develop these two mechanisms by arguing that the deterrence effect is stronger when rivals' speed is enhanced by their downstream capabilities, or when rivals' exclusion is enhanced by their litigation experiences. Findings suggest that a firm's path of resource accumulation evolves through avoidance of rivals' paths, and deterrence may constitute a viable alternative theory of resource heterogeneity. Copyright © 2010 John Wiley & Sons, Ltd.
Label‐Free Attomolar Detection of Proteins Using Integrated Nanoelectronic and Electrokinetic Devices
Authors: Gong Jian‐Ru
Published: March 2010

High‐sensitivity screening of biomarkers is critical to areas ranging from early disease detection and diagnosis to bioterrorism surveillance. Here the development of integrated nanoelectronic and electrokinetic devices for label‐free attomolar detection of proteins is reported. Electrically addressable silicon nanowire field‐effect transistors and electrodes for electrokinetic transport are integrated onto a common sensor chip platform, and the nanowire devices are subsequently functionalized with receptors for selective biomarker detection. Nanowire devices modified with monoclonal antibody for prostate specific antigen exhibit close to a 104 increase in sensitivity due to streaming dielectrophoresis and corresponding electrostatic contribution to the binding affinity after application of an AC electric field. The devices are also modified with receptors for cholera toxin subunit B and achieve a similar enhancement. These results show general applicability of this method, and could open up opportunities in early stage disease detection and the analysis of proteins from single cells.
Eine Integrierte Methode für die Sicherheitsbewertung von Glasbauteilen
Authors: Bos Freek Paul
Published: March 2010

Die bestehenden Methoden zur Sicherheitsbewertung von Glaskonstruktionen sind unzureichend. Es fehlen identifizierbare Bauteil‐Sicherheits‐Eigenschaften. Die Folge sind Diskussionen und Unsicherheiten in der Ingenieurpraxis. Ziel der Integrierten Methode für die Sicherheitsbewertung von Glasbauteilen ist die Schaffung objektiver Kriterien für den Vergleich von Glaskonstruktionen hinsichtlich ihrer Sicherheit. Dafür werden vier Eigenschaften von Glaskonstruktionen definiert: Widerstand, Schadensanfälligkeit, Redundanz und Bruchart. Diese sind graphisch im Bauteilsicherheitsdiagramm zusammengefasst. Es werden ebenso unterschiedliche, zugrunde liegende Konzepte, vorgestellt, die es erlauben, das Leistungsvermögen so zu definieren, dass jede einzelne Bauteil‐Sicherheits‐Eigenschaft geprüft werden kann.

An Integrated Approach to Structural Glass Safety. Existing methods to asses the safety of structural glass elements are insufficient. There is a lack of identifiable element safety properties. As a result, there is much confusion and discussion in professional practice. In an attempt to obtain objective criteria to compare structural glass designs with regard to safety, the Integrated Approach to Structural Glass Safety is proposed. Four properties of the glass elements are defined: resistance, damage sensitivity, redundancy and fracture mode. They are graphically combined in the element safety diagram. Several underlying concepts are also introduced, so that performance requirements can be formulated to which each element safety property can be checked.
Interaktion Gleis/Brücke – Stand der Technik und Beispiele
Authors: Freystein Hartmut
Published: March 2010

Die Wahl einer geeigneten Brücke sowie die Konstruktion und die Bemessung von Eisenbahnbrücken werden maßgeblich beeinflusst von der Interaktion zwischen dem Oberbau und der Brücke aufgrund der Einwirkungen aus dem Eisenbahnverkehr (Anfahren, Bremsen und LM 71) sowie Temperaturschwankungen. Wesentliche Parameter auf Bauwerksseite sind die Oberbauart, die Ausgleichs‐ und Dehnlängen des Überbaus, die Unterbausteifigkeit, die Übergangskonstruktion sowie die Bauweise. Während in den meisten Fällen vereinfachte Bemessungsverfahren zum Einsatz kommen, müssen in schwierigen Fällen aufwändige Berechnungsverfahren durchgeführt werden. In diesem Beitrag werden die technischen Hintergründe und der Stand der Technik mit einem Ausblick auf Weiterentwicklungen aufgezeigt.

Track/Bridge‐Interaction – State of the art and examples. Track/Bridge‐Interaction significantly influences the choice of bridge‐systems, the construction and calculation because of the actions due to rail traffic (braking and acceleration, LM 71) and changes of temperature. Main parameters with regard to the construction are the track superstructure, expansion length of bridge superstructure, support stiffness, transitions structures for bridges and the bridge design. Whereas in the majority of cases simplified calculation methods are sufficient, in certain difficult cases special and complex calculation methods are necessary. This article demonstrates the technical background and the state of the art with a perspective to further developments.
Geklebte Ganzglaskonstruktion für das Leibniz‐Institut für Festkörper‐ und Werkstoffforschung in Dresden
Authors: Weller Bernhard , Döbbel Florian , Nicklisch Felix , Prautzsch Volker , Rücker Sebastian
Published: March 2010

Die historischen Drucktanks der neuen Heliumverflüssigungsanlage des Leibniz‐Instituts für Festkörper‐ und Werkstoffforschung in Dresden präsentieren sich der Öffentlichkeit in einer in Deutschland bisher einmaligen Ganzglaskonstruktion. Die Vision einer gläsernen Hülle ohne störende metallische Verbindungsmittel konnte von der Idee bis hin zum fertigen Bauwerk verwirklicht werden. Vier gläserne Rahmen, in den Ecken durch transparente Klebungen gefügt, tragen die äußere Hülle der Glasbox. Der Ausführung gingen umfangreiche theoretische und experimentelle Untersuchungen zum Tragverhalten und zur Herstellungstechnologie voraus und bildeten die Grundlage für die notwendige Zustimmung im Einzelfall.

All Glass Enclosure for the Leibniz Institute for Solid State and Material Research in Dresden. The pressure tanks – components of historic value – for the recently installed helium liquefaction unit at the Leibniz Institute for Solid State and Materials Research in Dresden are displayed in an all glass enclosure which has been produced for the first time in Germany. The idea of a transparent structure with no distracting bolts or clamps was developed from vision to final solution. Four glass frames joined by transparent adhesives at their corners support the outer walls and ceiling of the glass box. Substantial theoretical and experimental studies of the structural behaviour and the manufacturing technology were required for the approval by the building authorities.
Transparentes Raumstabwerk über dem Innenhof des Berliner Reichstagspräsidentenpalais
Authors: Weller Bernhard , Reich Stefan , Ebert Jan
Published: March 2010

Das Institut für Baukonstruktion, Technische Universität Dresden, ist maßgeblich an der Entwicklung von selbsttragenden transparenten Raumstabwerken beteiligt. Diese basieren auf stählernen Raumfachwerken, bei denen alle Stäbe der Druckebene durch in ihrer Ebene lastabtragende Verglasungen ersetzt werden. Im Jahr 2009 wurde eine erste Dachkonstruktion dieser neuartigen Bauweise über dem Innenhof des ehemaligen Berliner Reichstagspräsidentenpalais errichtet. Dabei handelt es sich um ein zweilagiges, einachsig gekrümmtes, biegesteifes Raumtragwerk mit Abmessungen von 21 m x 14 m. Der Lastabtrag der Druckkräfte in der Obergurtebene wird durch Mehrscheiben‐Isolierglas mit Scheibenabmessungen von 1,80 m x 1,26 m sichergestellt. Dieser Beitrag beschreibt das Konzept, die Tragwerksplanung, die Bauteilversuche zur Erlangung der ZiE sowie die Bauausführung.

Transparent space grid structure above the inner courtyard of the Berlin palace Reichstagspräsidentenpalais. The Institute of Building Construction, Technische Universität Dresden, is decisively involved in the development of transparent space grid structures. These structures base on steel space grid structures, at which all steel members in the compression layer are replaced by in‐plane loaded glazing. In 2009, the first glass roof made of this new construction type was erected above the inner courtyard of the Berlin palace Reichstagspräsidentenpalais. The roof consists of a single curved, double layer transparent space grid structure with dimensions of 21 m x 14 m. The load transfer in the compression layer is ensured by IGU with regular dimensions of 1.80 m x 1.26 m. The contribution describes the concept, the structural design, the testing and the erection.
Knickfestigkeit und einheitliche Knickkurven für scheibenförmige Glasstützen mit Monoglasquerschnitt aus TVG und ESG
Authors: Feldmann Markus , Langosch Katharina
Published: March 2010

Erst in letzter Zeit wurden die Knick‐ und Stabilitätseigenschaften von Baugläsern näher erforscht. Dabei sind überwiegend Untersuchungen an Monoglasquerschnitten, vereinzelt auch an Verbundglasquerschnitten durchgeführt worden. Gleichwohl fehlt es bis jetzt an konsistenten technischen Regeln für die Bemessung von stabilitätsgefährdeten Glasbauteilen. Deswegen wurde vom Deutschen Stahlbauverband (DSTV) ein AiF‐Projekt aufgelegt, das Wissenslücken schließen und einheitliche Regelvorschläge zur Bemessung von stabilitätsgefährdeten Glasbauteilen geben soll. Das Projekt bezieht sich sowohl auf Knicken als auch auf Biegedrillknicken jeweils für verschiedene Belastungsarten und Querschnittsausführungen. Der vorliegende Aufsatz soll sich auf das Knicken von Glasstützen mit monolithischen Querschnitten beschränken und stellt die hierfür notwendigen Grundlagen, Experimente und Herleitungen von einheitlichen Knickspannungslinien vor.

Buckling resistance and buckling curves of pane‐like glass columns with monolithic sections of heat strengthened and tempered glass. There is some knowledge on the stability behaviour of glass panes under axial loading, i.e. of their buckling stability. However, only a few investigations have been performed so far in this direction, predominantly at cross‐sections with monopanes and sporadically at cross‐sections with laminated glass. Thus a research project was initiated by the Deutscher Stahlbauverband (DSTV, German Steel Construction Association) and the German Ministry of Economics, by which the buckling of pane‐like glass columns as well as the lateral torsional buckling of glass beams, both with mono‐ and laminated sections has been thoroughly investigated, where the aforementioned problems are to be resolved. The article focuses on the results for buckling with monolithic sections of heat strengthened and tempered glass, giving buckling curves proposed by derivations and experiments.
Censored data
Authors: Gijbels Irène
Published: March 2010

The analysis of censored data is a major issue in survival studies. Censored data are together with truncated data, missing data, current status data, and others, among the complex data structures in which only partial information on the variable(s) of interest is available. In this article, we discuss the various types of censoring mechanisms and review the basic statistical procedures for right random censored data, including maximum likelihood estimation of parameters of the distribution, nonparametric estimation of the cumulative distribution function, and estimation of the cumulative hazard function. We briefly discuss two of the most popular regression models for censored data and review estimation under the proportional hazards model. Copyright © 2010 John Wiley & Sons, Inc.

This article is categorized under:

Data: Types and Structure > Traditional Statistical Data
Docosahexaenoic acid status in females of reproductive age with maple syrup urine disease
Authors: Mazer Laura M. , Yi Sarah H. L. , Singh Rani H.
Published: March 2010

Individuals with maple syrup urine disease (MSUD) have impaired metabolism of branched‐chain amino acids (BCAA) valine, isoleucine, and leucine. Life‐long dietary therapy is recommended to restrict BCAA intake and thus prevent poor neurological outcomes and death. To maintain adequate nutritional status, the majority of protein and nutrients are derived from synthetic BCAA‐free medical foods with variable fatty acid content. Given the restrictive diet and the importance of omega‐3 fatty acids, particularly docosahexaenoic acid (DHA), in neurological development, this study evaluated the dietary and fatty acid status of females of reproductive age with MSUD attending a metabolic camp. Healthy controls of similar age and sex were selected from existing normal laboratory data. Total lipid fatty acid concentration in plasma and erythrocytes was analyzed using gas chromatography–mass spectroscopy. Participants with MSUD had normal to increased concentrations of plasma and erythrocyte alpha linolenic acid (ALA) but significantly lower concentrations of plasma and erythrocyte docosahexaenoic acid (DHA) as percent of total lipid fatty acids compared with controls (plasma DHA: MSUD 1.03 ± 0.35, controls 2.87 ± 1.08; P = 0.001; erythrocyte DHA: MSUD 2.58 ± 0.58, controls 3.66 ± 0.80; P = 0.011). Dietary records reflected negligible or no DHA intake over the 3‐day period prior to the blood draw (range 0–2 mg). These results suggest females of reproductive age with MSUD have lower blood DHA concentrations than age‐matched controls. In addition, the presence of ALA in medical foods and the background diet may not counter the lack of preformed DHA in the diet. The implications of these results warrant further investigation.
The Arabidopsis ortholog of the 77 kDa subunit of the cleavage stimulatory factor (AtCstF‐77) involved in mRNA polyadenylation is an RNA‐binding protein
Authors: Bell Stephen A. , Hunt Arthur G.
Published: March 2010

MINT‐7712550: AtCstF77 (uniprotkb:Q8LKG5) binds (MI:0407) to AtCPSF30 (uniprotkb:A9LNK9) by pull down (MI:0096)
NUTRIENT USE PATTERN IN THE IRRIGATED RICE-WHEAT CROPPING SYSTEM IN THE INDO-GANGETIC PLAINS OF HARYANA, INDIA
Authors: SINGH SHER , MALIK R. K. , DHANKAR J. S. , YADAV ASHOK , GARG RAJBIR , KAMBOJ B. R. , SHEORAN P. , LATHWAL O. P.
Published: March 2010

On-farm nutrient management practices were evaluated in the irrigated rice-wheat cropping system (RWCS) in northwestern India. Large farmers used comparatively higher doses of nutrients than small and medium farmers for both rice and wheat crops. On average, a field is treated with organic manure after every 15 years for rice and 53 years for wheat. Nitrogen use was generally more than the recommended dose for both crops. Phosphorus use in wheat was nearly as per recommendation, while in rice it was below the recommended dose. Potassium use was almost nil; however, the use of Zn (particularly in rice) is becoming common. Use of biofertilizers was negligible. Overall, farmers applied higher doses of organic manures, K, Zn and biofertilizers in rice than wheat, and there was increasing trend in their use with increase in the size of land holdings. Grain yield increased significantly with increase in the size of land holding in rice but remained almost same in wheat. This study generated comprehensive data on nutrient use pattern in the RWCS, thus providing necessary input to researchers, planners and developmental agencies who wish to enhance food security.
Crystallization and textural evolution of a closed-system magma chamber: insights from a crystal size distribution study of the Lilloise layered intrusion, East Greenland
Authors: MAGEE C. , O'DRISCOLL B. , CHAMBERS A. D.
Published: March 2010

The recognition that postcumulus processes significantly modify primary textures in layered mafic intrusions has thrown into question many early observations on which classical crystallization theories are based. Petrographic observations combined with quantitative textural analysis of samples from various stratigraphic levels of the Lilloise intrusion, East Greenland, demonstrate that postcumulus textural modification of cumulates, formed during the solidification of a closed system magma chamber, may be detected. Crystal size distribution (CSD) measurements of Lilloise cumulates and the resulting CSD profiles are compared to predicted theoretical closed system CSD profiles. Similarities between the measured CSD profiles and published predicted CSD profiles support Lilloise magma evolving in a closed system chamber and indicate that primary crystallization processes can be distinguished using quantitative textural techniques. Textural coarsening driven by syn-magmatic deformation is suggested to be the dominant postcumulus process affecting CSD plot morphology. CSD slope values and profiles (plot shapes) remain relatively constant for a given liquidus mineral (particularly olivine and clinopyroxene), so that the number of phases on the liquidus at any one time affects mineral modal abundances. As a result, CSDs generally exhibit overall smaller grainsizes and progressively lower nucleation densities at higher levels in the intrusion.
Roman Seaborne Raids During the Mid-Republic: Sideshow or Headline Feature?
Authors: BRAGG EDWARD
Published: March 2010

I never share the feeling of those who go so far in their anger against men of their own race that they not only take away their enemies' annual crops but also destroy their trees and agricultural equipment, thereby leaving no opportunity for reparation. Instead, those who do that seem to me to be extremely short-sighted: the more they assume to be terrorizing the enemy by ruining their land and taking away all their hopes of earning a living – not just for the present, but also for the future – just that much more do they brutalize others and so create a hatred of themselves that is never removed.
Flattery and Frankness in Horace and Philodemus
Authors: KEMP JEROME
Published: March 2010

Conduct in human relationships, in amicitia (‘friendship’), is a prevalent theme in Horace's works, and was of considerable interest to ancient philosophers. The extent to which such aspects of human behaviour should be regarded as philosophical is a question that has been discussed both in relation to ancient philosophical texts and to Horace. My concern here, however, is not primarily to argue for their philosophical nature but to illuminate certain influences in the Satires and Epistles that draw on philosophical texts pertaining to conduct and amicitia, and in particular those of Horace's near contemporary, Philodemus.
Reassessing the Standard of Living in the Soviet Union: An Analysis Using Archival and Anthropometric Data
Authors: Brainerd Elizabeth
Published: March 2010

This article uses anthropometric and archival data to reassess the standard of living in the Soviet Union. In the prewar period, the population was small in stature and sensitive to the political and economic upheavals experienced in the country. Significant improvements in child height, adult stature, and infant mortality were recorded from approximately 1945 to 1970. While this period of physical growth was followed by stagnation in heights, the physical growth record of the Soviet population compares favorably with that of other European countries at a similar level of development in this period.
Economic Conditions in Early Modern Bengal: A Contribution to the Divergence Debate
Authors: Roy Tirthankar
Published: March 2010

This article contributes to the debate on relative levels of living in the early modern world by estimating the income and probable range of income growth in Bengal before European colonization. The exercise yields two conclusions, (a) average income in Bengal was significantly smaller than that in contemporary Western Europe, and (b) there is insufficient basis to infer either growth or decline in average income in the eighteenth century.
Particle dynamics in a turbulent particle–gas suspension at high Stokes number. Part 2. The fluctuating-force model
Authors: GOSWAMI PARTHA S. , KUMARAN V.
Published: March 2010

A fluctuating-force model is developed for representing the effect of the turbulent fluid velocity fluctuations on the particle phase in a turbulent gas–solid suspension in the limit of high Stokes number, where the particle relaxation time is large compared with the correlation time for the fluid velocity fluctuations. In the model, a fluctuating force is incorporated in the equation of motion for the particles, and the force distribution is assumed to be an anisotropic Gaussian white noise. It is shown that this is equivalent to incorporating a diffusion term in the Boltzmann equation for the particle velocity distribution functions. The variance of the force distribution, or equivalently the diffusion coefficient in the Boltzmann equation, is related to the time correlation functions for the fluid velocity fluctuations. The fluctuating-force model is applied to the specific case of a Couette flow of a turbulent particle–gas suspension, for which both the fluid and particle velocity distributions were evaluated using direct numerical simulations by Goswami & Kumaran (2010). It is found that the fluctuating-force simulation is able to quantitatively predict the concentration, mean velocity profiles and the mean square velocities, both at relatively low volume fractions, where the viscous relaxation time is small compared with the time between collisions, and at higher volume fractions, where the time between collisions is small compared with the viscous relaxation time. The simulations are also able to predict the velocity distributions in the centre of the Couette, even in cases in which the velocity distribution is very different from a Gaussian distribution.
Transition to turbulence in the boundary layer over a smooth and rough swept plate exposed to free-stream turbulence
Authors: SCHRADER LARS-UVE , AMIN SUBIR , BRANDT LUCA
Published: March 2010

Receptivity, disturbance growth and transition to turbulence of the three-dimensional boundary layer developing on a swept flat plate are studied by means of numerical simulations. The flow is subject to a favourable pressure gradient and represents a model for swept-wing flow downstream of the leading edge and upstream of the pressure minimum of the wing. The boundary layer is perturbed by free-stream turbulence and localized surface roughness with random distribution in the spanwise direction. The intensity of the turbulent free-stream fluctuations ranges from conditions typical for free flight to higher levels usually encountered in turbo-machinery applications. The free-stream turbulence initially excites non-modal streak-like disturbances as in two-dimensional boundary layers, soon evolving into modal instabilities in the form of unsteady crossflow modes. The crossflow modes grow faster than the streaks and dominate the downstream disturbance environment in the layer. The results show that the receptivity mechanism is linear for the disturbance amplitudes under consideration, while the subsequent growth of the primary disturbances rapidly becomes affected by nonlinear saturation in particular for free-stream fluctuations with high intensity. Transition to turbulence occurs in the form of localized turbulent spots randomly appearing in the flow. The main features of the breakdown are presented for the case of travelling crossflow vortices induced by free-stream turbulence. The flow is also receptive to localized roughness strips, exciting stationary crossflow modes. The mode with most efficient receptivity dominates the downstream disturbance environment. When both free-stream fluctuations and wall roughness act on the boundary layer at the same time, transition is dominated by steady crossflow waves unless the incoming turbulence intensity is larger than about 0.5% for roughness amplitudes of about one tenth of the boundary-layer displacement thickness. The results show that a correct prediction of the disturbance behaviour can be obtained considering the receptivity and evolution of individual modes. In addition, we provide an estimate for the amplitudes of the external disturbance sources above which a fully nonlinear receptivity analysis is necessary.
On the transient nature of localized pipe flow turbulence
Authors: AVILA MARC , WILLIS ASHLEY P. , HOF BJÖRN
Published: March 2010

The onset of shear flow turbulence is characterized by turbulent patches bounded by regions of laminar flow. At low Reynolds numbers localized turbulence relaminarizes, raising the question of whether it is transient in nature or becomes sustained at a critical threshold. We present extensive numerical simulations and a detailed statistical analysis of the lifetime data, in order to shed light on the sources of the discrepancies present in the literature. The results are in excellent quantitative agreement with recent experiments and show that turbulent lifetimes increase super-exponentially with Reynolds number. In addition, we provide evidence for a lower bound below which there are no meta-stable characteristics of the transients, i.e. the relaminarization process is no longer memoryless.
Parameter regimes for slow, intermediate and fast MHD shocks
Authors: DELMONT P. , KEPPENS R.
Published: March 2010

We investigate under which parameter regimes the magnetohydrodynamic (MHD) Rankine–Hugoniot conditions, which describe discontinuous solutions to the MHD equations, allow for slow, intermediate and fast shocks. We derive limiting values for the upstream and downstream shock parameters for which shocks of a given shock-type can occur. We revisit this classical topic in nonlinear MHD dynamics, augmenting the recent time reversal duality finding by in the usual shock frame parametrization.
Theory of particle diffusion in electrostatic turbulent plasma using extended direct-interaction approximation
Authors: TAGUCHI M.
Published: March 2010

The theory of particle diffusion in an electrostatic turbulent plasma is formulated by applying the direct-interaction approximation (DIA) to subensemble-averaged functions instead of conventional ensemble-averaged ones. This theory approximately incorporates the Lagrangian description into the DIA through decorrelation trajectories. The running diffusion coefficient is shown to be calculated by solving a nonlinear ordinary differential equation together with an equation for decorrelation trajectories and by averaging initial conditions at the starting point of trajectories.
A mathematical model of an oil and gas field development process
Authors: ATKINSON C. , ISANGULOV R.
Published: March 2010

A mathematical model of the development of an oil and gas field is presented. The field development process is treated as sequential in nature. Completion of a well and its production are considered to be random processes. The model uses results from renewal theory where the completion of a well and failure to produce economical amount of oil or gas are analogous to the failure of a component. In principle, the theory described can give the complete probability distribution associated with a field development. Explicit expressions are given for the expected value and variance of the number of completed wells.
The State and Violence
Authors: Hartzell Caroline
Published: March 2010

Violence and Social Orders: A Conceptual Framework for Interpreting Recorded Human History (Cambridge 2009) offers a theory of the evolution of the modern state and an even more ambitious framework “for interpreting recorded human history.” The book raises fundamental questions about the political structuring of violence, the functions of the rule of law, and the establishment and maintenance of political order. In doing so, it speaks to a range of political scientists from a variety of methodological and subfield perspectives. We have thus invited four prominent political science scholars of violence and politics to comment on the book: Jack Snyder, Caroline Hartzell, Jean Bethke Elshtain, and Larry Diamond.
The State and Violence
Authors: Elshtain Jean Bethke
Published: March 2010

Violence and Social Orders: A Conceptual Framework for Interpreting Recorded Human History (Cambridge 2009) offers a theory of the evolution of the modern state and an even more ambitious framework “for interpreting recorded human history.” The book raises fundamental questions about the political structuring of violence, the functions of the rule of law, and the establishment and maintenance of political order. In doing so, it speaks to a range of political scientists from a variety of methodological and subfield perspectives. We have thus invited four prominent political science scholars of violence and politics to comment on the book: Jack Snyder, Caroline Hartzell, Jean Bethke Elshtain, and Larry Diamond.
Response to Graciana del Castillo's review of After War: The Political Economy of Exporting Democracy
Authors: Coyne Christopher J.
Published: March 2010

I would like to thank Graciana del Castillo for her remarks regarding After War. I will focus my response on what del Castillo finds to be the major shortcoming of my book—the main policy implication. In After War, I conclude that current approaches to reconstruction, which typically rely on military occupation, are more likely to fail than to succeed. This outcome is not due to a lack of planning, effort, or political will, but is instead is the result of the array of incentives and constraints limiting what occupiers and policymakers can rationally design and implement in foreign societies. In considering alternative strategies for exporting the ideas, values, and beliefs underpinning liberal democracy, I argue that the U.S. should assume a default position of military non-intervention and free trade (unilateral if necessary). Del Castillo is sympathetic to this position as a “preventive measure,” but does not seem convinced of its suitability as a primary strategy. For example, she points out that offering trade preferences to the Taliban following 9/11 would hardly have brought liberalism to Afghanistan. I agree. However, I do not think this point undercuts my argument for a default position of free trade and non-intervention. Let me clarify why I believe this to be the case.
The State and Violence
Authors: Diamond Larry
Published: March 2010

Violence and Social Orders: A Conceptual Framework for Interpreting Recorded Human History (Cambridge 2009) offers a theory of the evolution of the modern state and an even more ambitious framework “for interpreting recorded human history.” The book raises fundamental questions about the political structuring of violence, the functions of the rule of law, and the establishment and maintenance of political order. In doing so, it speaks to a range of political scientists from a variety of methodological and subfield perspectives. We have thus invited four prominent political science scholars of violence and politics to comment on the book: Jack Snyder, Caroline Hartzell, Jean Bethke Elshtain, and Larry Diamond.
It Takes a State: A Policy Feedback Model of Women's Political Representation
Authors: McDonagh Eileen
Published: March 2010

American women attain more professional success in medicine, business, and higher education than do most of their counterparts around the world. An enduring puzzle is, therefore, why the US lags so far behind other countries when it comes to women's political representation. In 2008, women held only 16.8 percent of seats in the House of Representatives, a proportion that ranks America lower than 83 other countries. This article addresses this conundrum. It establishes that equal rights alone are insufficient to ensure equal access to political office. Also necessary are public policies representing maternal traits that voters associate with women. Such policies have feedback effects that teach voters that the maternal traits attributed to women represent strengths not only in the private sphere of the home but also in the public sphere of the state. Most other democracies now have such policies in place, but the United States lacks such policies, which accounts for its laggard status with regard to the political representation of women.
Feminism's Quest for Common Desires
Authors: Marso Lori J.
Published: March 2010

One attraction of “choice” feminism has been its refusal to judge the diverse desires of women. Yet for feminism to retain its political vision as a quest for social justice, we must continue difficult conversations concerning how acting on our individual desires impacts the lives of others. In this essay, I argue that feminists can acknowledge women's diverse desires while forging a meaningful feminist community. I make this argument by considering feminism's relationship to time, and particularly how women's diverse desires are read in each moment in time. If we abandon the generational model, wherein each new generation of feminists improves upon the last, for a genealogical perspective where women recognize our feminist origins and empathize with the diverse struggles of other women, we might reaffirm social justice for the community as central to feminist politics. To articulate this possibility, I turn to the work of Simone de Beauvoir to explain her discovery of how her embodiment as a woman and her relationship to femininity becomes a way of grounding a feminist politics. Recognizing the “demands of femininity” in other women's lives allows us to affirm feminist community while retaining the capacity to make judgments that realize social justice as a feminist goal.
Rebuilding War-Torn States: The Challenge of Post-Conflict Economic Reconstruction, by Graciana Del Castillo
Authors: Coyne Christopher J.
Published: March 2010

In this book, Graciana Del Castillo draws on theory, her own experiences as senior economist in the Cabinet of the United Nations secretary-general and as an International Monetary Fund staffer, and qualitative case studies to critically reconsider the challenges of postconflict economic reconstruction. The core argument is as follows. Countries making the shift from war to peace face a multipronged transition in the economic, legal, political, social, and security sectors. Given this multifaceted transition, economic reconstruction is fundamentally different from the “development as usual” approach taken by the international community to address typical socioeconomic challenges faced by peaceful developing countries. Instead, economic reconstruction in postconflict countries is a “development plus” challenge, meaning that these countries face the same challenges as other developing countries plus the added challenge of achieving reconciliation and peace. Del Castillo concludes that many post–Cold War reconstruction efforts have failed because of the development as usual approach to reconstruction, a lack of comprehensive planning, insufficient aid and assistance, and the inadequacies of international organizations (e.g., the United Nations and international financial institutions) in dealing with the challenges of reconstruction.
Global Gender Inquality and the Empowerment of Women
Authors: Moghadam Valentine M.
Published: March 2010

Half the Sky: Turning Oppression into Opportunity for Women Worldwideis a powerful journalistic account of the oppression of women worldwide, and of the ways that some women and men have struggle against this oppression and discovered new forms of economic empowerment. The book—in its eleventh printing in less than a year, and with testimonials from the likes of Angelina Jolie and George Clooney—is also a publishing sensation.Half the Skybrings much attention to an important and timely topic, and it creatively combines narrative, analysis, and policy prescriptions, and so we invited three prominent scholars of gender inequality and development to reflect on the book's strengths and weaknesses: Ayelet Shachar, Uma Narayan, and Valentine M. Moghadam.
Precise Li abundances in metal-poor stars: depletion in the Spite plateau
Authors: Meléndez J. , Casagrande L. , Ramírez I. , Asplund M.
Published: March 2010

We present Li abundances for 73 stars in the metallicity range −3.5 < [Fe/H] < −1.0 using improved IRFM temperatures (Casagrande et al. 2009) with precise E(B-V) values obtained mostly from interstellar NaI D lines, and high-quality equivalent widths (σEW ~ 3%). At all metallicities we uncover a fine-structure in the Li abundances of Spite plateau stars, which we trace to Li depletion that depends on both metallicity and mass. Models including atomic diffusion and turbulent mixing seem to reproduce the observed Li depletion assuming a primordial Li abundance ALi = 2.64 dex (MARCS models) or 2.72 (Kurucz overshooting models), in good agreement with current predictions (ALi = 2.72) from standard BBN.
Detailed analyses of three neutron-capture-rich carbon-enhanced metal-poor stars
Authors: Behara N. T. , Bonifacio P. , Ludwig H.-G. , Sbordone L. , González Hernández J. I. , Caffau E.
Published: March 2010

Approximately 20% of very metal-poor stars ([Fe/H] < −2.0) are strongly enhanced in carbon ([C/Fe] > +1.0). Such stars are referred to as carbon-enhanced metal-poor (CEMP) stars. We present a chemical abundance analysis based on high resolution spectra acquired with UVES at the VLT of three dwarf CEMP stars: SDSS J1349-0229, SDSS J0912+0216 and SDSS J1036+1212. These very metal-poor stars, with [Fe/H] < −2.5, were selected from our ongoing survey of extremely metal-poor dwarf candidates from the SDSS.

Among these CEMPs, SDSS J1349-0229 has been identified as a carbon star ([C/O] > +1.0). First and second peak s-process elements, as well as second peak r-process elements have been detected in all stars. In addition, elements from the third r-process peak were detected in one of the stars, SDSS J1036+1212. We present the abundance results of these stars in the context of neutron-capture nucleosynthesis theories.
The 9th Magnitude CEMP star BD+44°493: Origin of its Carbon Excess and Beryllium Abundance
Authors: Ito Hiroko , Aoki Wako , Honda Satoshi , Beers Timothy C. , Tominaga Nozomu
Published: March 2010

We performed a chemical abundance analysis of the very bright (V = 9.1) carbon-enhanced metal-poor (CEMP) star BD+44°493, which is the first star found with metallicity [Fe/H] < −3.5 and an apparent magnitude V < 12. The star is classified as a CEMP-no” subgiant, and its abundance pattern implies that a first-generation faint supernova is the most likely origin of its carbon excess. We set an very low upper limit on this star's beryllium abundance, which demonstrates that high C and O abundances do not necessarily imply high Be abundances.
Chemical abundances in planetary nebulae in three different galaxies
Authors: Peña Miriam
Published: March 2010

We analyze the PNe chemical behavior in three different galaxies, two dwarf irregulars and one spiral. Different behaviors are found. In the very low metallicity galaxy NGC 3109, PNe analyzed appear 0.39 dex O-richer than HII regions, while Ar/H ratio is, in average, 0.15 dex poorer. We interpret this as an evidence of significant O dredge-up in these LIMS, born in a very low metallicity environment. In NGC 6822, with a present metallicity 12+log O/H=8.06, two PN populations were found. A young one, with abundances similar to those in HII regions and an old population, with metallicities a factor of two lower. In this case no strong evidence for O dredge-up in LIMS is found. Therefore, metallicities lower than 12+log O/H =7.7 are required for an efficient O dredge-up. From our preliminary analysis of the abundances of PNe in NGC 300 we find that they are similar to the abundances in HII regions. Apparently, the PNe analyzed belong to a young population. Very similar abundance gradients, with galactocentric distance, are found for HII regions and for PNe.
Can we trust elemental abundances derived in late-type giants with the classical 1D stellar atmosphere models?
Authors: Kučinskas A. , Dobrovolskas V. , Ivanauskas A. , Ludwig H.-G. , Caffau E. , Blaževičius K. , Klevas J. , Prakapavičius D.
Published: March 2010

We compare the abundances of various chemical species as derived with 3D hydrodynamical and classical 1D stellar atmosphere codes in a late-type giant characterized by Teff =3640 K, log g = 1.0, [M/H]= 0.0. For this particular set of atmospheric parameters the 3D–1D abundance differences are generally small for neutral atoms and molecules but they may reach up to 0.3–0.4 dex in case of ions. The 3D–1D differences generally become increasingly more negative at higher excitation potentials and are typically largest in the optical wavelength range. Their sign can be both positive and negative, and depends on the excitation potential and wavelength of a given spectral line. While our results obtained with this particular late-type giant model suggest that 1D stellar atmosphere models may be safe to use with neutral atoms and molecules, care should be taken if they are exploited with ions.