bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variation of frontal and precipitation structure along a cold front
Authors: Browning K. A. , Roberts N. M. 
Published: September 2008

AbstractA diagnostic study is presented to illustrate the sequence of events in which a warm‐conveyor‐belt (WCB) flow is drawn into the circulation of a developing extratropical cyclone and interacts with dry air aloft to produce distinctive precipitation structures. The poleward boundary of the upstream end of the WCB was associated with a classical (ana) cold‐frontal structure. The other end of the WCB flow, closer to the cyclone centre, was overrun by a ‘dry intrusion’ of low wet‐bulb potential temperature air to give a split (kata) cold front. The orientation of the surface cold front (i.e. the WCB boundary) changed significantly between these two parts but the orientation of the surface geostrophic flow within the WCB changed relatively little between the two parts. The surface cold front was characterized in most places by a narrow cold‐frontal rainband composed of shallow line‐convection elements (precipitation cores) aligned nearly parallel to the surface geostrophic flow in the WCB. The changing relationship between the frontal orientation and the direction of the surface flow accounts for the fact that the line‐convection elements occurred end‐to‐end to give almost two‐dimensional line convection along the classical ana part of the cold front, but were non‐aligned and widely spaced along the split cold‐front part.
Dimensional analysis of a convecting atmosphere in equilibrium with external forcing
Authors: Craig George C. 
Published: September 2008

AbstractIt has recently been suggested by Rennó and Ingersoll that certain properties of a convecting atmosphere in equilibrium with external forcing can be predicted by considering the convecting atmosphere as a heat engine. Their argument is modified to express the forcing of convection in terms of a specified cooling of the convective layer. It is found that convective available potential energy and mean convective vertical velocity are independent of the forcing, while the fractional area of the convection increases in proportion with the forcing. These predictions are consistent with recent numerical results from cloud‐ensemble models. Finally, it is shown by a formal dimensional analysis that these conclusions are independent of the details of the thermodynamic formulation.
The role of droplet spectra for cloud radiative properties
Authors: Hatzianastassiou Nikos , Wobrock Wolfram , Flossma Andrea I. 
Published: September 2008

AbstractThe evolution of different types of clouds is simulated with a spectral scavenging and microphysics model, DESCAM, coupled to the dynamics of an ascending and entraining air‐parcel model. the resulting microphysical properties of the cloud are then coupled with a radiative‐transfer model in order to calculate the optical properties, the up‐ and downgoing radiative fluxes, the cloud optical depth, and the cloud albedo. For a stratiform cloud investigated during the North Atlantic Regional Experiment good agreement with the experimental data is obtained. For a medium‐sized convective cloud developing in marine or continental air the calculated cloud optical depth and the cloud albedo are compared with current parametrizations in global circulation models. the largest deviations are observed for cases with a large effective radius, e.g. when the cloud developed precipitation. In general, cloud optical depth and cloud albedo per unit cloud depth decrease with time, caused by the broadening of the cloud‐drop spectrum.
Attribution and its application to mesoscale structure associated with tropopause folds
Authors: Thorpe A. J. 
Published: September 2008

AbstractIt is important in meteorology to be able to establish a link between various features. This link in its strongest form would be referred to as ‘cause‐and‐effect’ but this is extremely difficult to establish for atmospheric flows. A weaker, but nonetheless powerful, link is ‘attribution’ which attempts to provide a way to associate various fundamental features, such as potential‐vorticity anomalies, to weather events involving regions of ascent. Attribution is not new and it is implicit in the way that atmospheric evolution is usually described. In this paper an attempt is made to define more precisely what are the steps and assumptions being made in such a method. These ideas become more concrete by applying them to a simple model of a two‐dimensional front at which there is a tropopause fold. the aim is to find the vertical motion attributable to the descended tropopause fold in an extra‐tropical cyclone. This is the first step in a longer programme of research designed to provide a test of the hypothesis that such a descended tropopause can trigger mesoscale phenomena such as convection and cyclones.
Observer‐based control of block‐triangular discrete time hybrid automata on a partial order
Authors: Del Vecchio Domitilla 
Published: September 2008

AbstractThe safety control problem for the class of discrete time block‐triangular order preserving hybrid automata with imperfect continuous state information is addressed. A dynamic feedback law is constructed in order to guarantee that the continuous state is always outside a bad set. The order preserving properties of the dynamics are exploited to construct state estimation and control algorithms that have linear complexity in the number of variables. Such algorithms adopt an interval abstraction approach, in which sets of interest are represented and propagated only through suitable upper and lower bounds. The proposed algorithms are applied to a collision avoidance problem arising in the context of intelligent transportation. Copyright © 2008 John Wiley & Sons, Ltd.
Measures to assess the prognostic ability of the stratified Cox proportional hazards model
Authors:   The Fibrinogen Studies Collaboration
Published: September 2008

AbstractMany measures have been proposed to summarize the prognostic ability of the Cox proportional hazards (CPH) survival model, although none is universally accepted for general use. By contrast, little work has been done to summarize the prognostic ability of the stratified CPH model; such measures would be useful in analyses of individual participant data from multiple studies, data from multi‐centre studies, and in single study analysis where stratification is used to avoid making assumptions of proportional hazards. We have chosen three measures developed for the unstratified CPH model (Schemper and Henderson's 𝒱 , Harrell's C‐index and Royston and Sauerbrei's 𝒟), adapted them for use with the stratified CPH model and demonstrated how their values can be represented over time. Although each of these measures is promising in principle, we found the measure of explained variation 𝒱 very difficult to apply when data are combined from several studies with differing durations of participant follow‐up. The two other measures considered, 𝒟 and the C‐index, were more applicable under such circumstances. We illustrate the methods using individual participant data from several prospective epidemiological studies of chronic disease outcomes. Copyright © 2008 John Wiley & Sons, Ltd.
Joint analysis of multiple longitudinal outcomes: Application of a latent class model
Authors: Putter Hein , Vos Tineke , de Haes Hanneke , van Houwelingen Hans 
Published: September 2008

AbstractWe address the problem of joint analysis of more than one series of longitudinal measurements. The typical way of approaching this problem is as a joint mixed effects model for the two outcomes. Apart from the large number of parameters needed to specify such a model, perhaps the biggest drawback of this approach is the difficulty in interpreting the results of the model, particularly when the main interest is in the relation between the two longitudinal outcomes. Here we propose an alternative approach to this problem. We use a latent class joint model for the longitudinal outcomes in order to reduce the dimensionality of the problem. We then use a two‐stage estimation procedure to estimate the parameters in this model. In the first stage, the latent classes, their probabilities and the mean and covariance structure are estimated based on the longitudinal data of the first outcome. In the second stage, we study the relation between the latent classes and patient characteristics and the other outcome(s). We apply the method to data from 195 consecutive lung cancer patients in two outpatient clinics of lung diseases in The Hague, and we study the relation between denial and longitudinal health measures. Our approach clearly revealed an interesting phenomenon: although no difference between classes could be detected for objective measures of health, patients in classes representing higher levels of denial consistently scored significantly higher in subjective measures of health. Copyright © 2008 John Wiley & Sons, Ltd.
System dynamics as model‐based theory building
Authors: Schwaninger Markus , Grösser Stefan 
Published: September 2008

AbstractThis paper introduces model‐based theory building as a feature of system dynamics (SD) with large potential. It presents a systemic approach to actualizing that potential, thereby opening up a new perspective on theory building in the social sciences. The question addressed is if and how SD enables the construction of high‐quality theories. This contribution is based on field experiment type projects which have been focused on model‐based theory building, specifically the construction of a middle‐range theory—not a general one. The process of model building and validation is analysed from a theory‐building perspective. The resulting theory is evaluated by means of a set of criteria for high‐quality theories. As a conclusion, the insights thus gained are presented and condensed in a tentative set of heuristic principles for model‐based theory building. Copyright © 2008 John Wiley & Sons, Ltd.
System of system failures: Meta methodology for IT engineering safety
Authors: Nakamura Takafumi , Kijima Kyoich 
Published: September 2008

AbstractA meta methodology for holistically examining system failures is proposed, for the purpose of preventing further occurrence of these failures. Such a meta methodology should promote double loop learning to change mental models. It should have three key features to promote double loop learning, and the proposed methodology provides them. These features are (1) a common language for understanding system failures, (2) complementary methodological features to accommodate multiple participants in achieving engineering safety and (3) inclusion of the dynamic aspects of system failures in order to avoid the introduction of side effects by quick fixes. An application example in IT engineering demonstrates that the proposed meta methodology overcomes the shortcomings of current methodologies. The example also shows that the meta methodology proactively promotes double loop learning from previous system failures. Copyright © 2008 John Wiley & Sons, Ltd.
Blood pressure estimation in the human fetal descending aorta
Authors: Struijk P. C. , Mathews V. J. , Loupas T. , Stewart P. A. , Clark E. B. , Steegers E. A. P. , Wladimiroff J. W. 
Published: September 2008

AbstractObjectivesThe objectives of this study were to estimate fetal blood pressure non‐invasively from two‐dimensional color Doppler‐derived aortic blood flow and diameter waveforms, and to compare the results with invasively derived human fetal blood pressures available from the literature.MethodsAortic pressures were calculated from digitally recorded color Doppler cineloops of the fetal descending aorta by applying the Womersley model in combination with the two‐element Windkessel model, assuming constant pulse wave velocity during the second half of pregnancy. The results were compared with invasively derived human fetal blood pressures obtained from the literature.ResultsIn 21 normal pregnancies the estimated mean aortic pressure regression line increased linearly from 28 mmHg at 20 weeks of gestation to 45 mmHg at 40 weeks of gestation. The pulse pressure based on the regression line increased linearly from 21 mmHg at 20 weeks of gestation to 29 mmHg at 40 weeks of gestation. The aortic compliance exhibited a log linear relationship with the gestational age and a statistically significant eightfold increase was observed between 20 and 40 weeks. The aortic downstream peripheral resistance exhibited an exponentially decaying relationship across the same gestational age range. Non‐invasively derived aortic systolic and diastolic aortic pressures were comparable with previously reported invasively derived systolic and diastolic umbilical arterial pressures; however, the mean pressures differed significantly from those reported in the umbilical artery in a separate study. The aortic systolic pressures calculated in this study were significantly higher than invasively derived left ventricular systolic pressures that have been previously reported in the literature.ConclusionsThis study demonstrates the feasibility of estimating arterial blood pressure in the human fetus. The method described is of potential use in assessing fetal blood pressure non‐invasively, particularly for studying relative changes with time. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Cervical length and maternal factors in expectantly managed prolonged pregnancy: prediction of onset of labor and mode of delivery
Authors: Rao A. , Celik E. , Poggi S. , Poon L. , Nicolaides K. H. 
Published: September 2008

AbstractObjectiveTo examine the value of combining cervical length and maternal characteristics in a prolonged‐pregnancy clinic in the prediction of the probability of firstly, spontaneous onset of labor within the subsequent 10 days and secondly, the need for Cesarean section.MethodsThis was a prospective study of women with singleton pregnancies attending an ultrasound‐based prolonged‐pregnancy clinic at 40 + 4 to 41 + 6 weeks of gestation. The policy was to delay induction of labor by 7–10 days unless there was evidence of a specific medical or obstetric indication or the mother wanted earlier delivery. The measurement of cervical length was not given to the obstetrician, midwife or patient. Regression analysis was used to determine which of the following factors had a significant contribution in predicting induction of labor: maternal age, body mass index (BMI), ethnic origin, parity and cervical length. Regression analysis was also used to determine which of the factors amongst the maternal characteristics, onset of labor and cervical length provided significant prediction of Cesarean section.ResultsWe examined 2316 pregnancies but we excluded from further analysis 452 (19.5%) cases because iatrogenic delivery was carried out within the subsequent 6 days, including 427 cases of induction of labor (340 at the request of the mother and 87 for medical indications) and 25 cases of Cesarean section. In the remaining 1864 cases there was spontaneous onset of labor and delivery within 10 days in 1536 (82.4%) and induction of labor in 7–10 days in 328 (17.6%). The rate of Cesarean section was 15.2% (233 of 1536) in those with spontaneous onset of labor and 36.0% (118 of 328) in those whose labor was induced. Regression analysis demonstrated that in the prediction of induction of labor there were significant contributions from cervical length, BMI, parity and gestational age, and in the prediction of Cesarean section there were significant contributions from onset of labor, cervical length, BMI, parity and ethnicity.ConclusionUltrasonographic measurement of cervical length at 41 weeks together with maternal factors can define the patient‐specific probability of spontaneous onset of labor in the subsequent week and the risk of Cesarean section. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Maternal serum inhibin‐A and activin‐A levels in the first trimester of pregnancies developing pre‐eclampsia
Authors: Spencer K. , Cowans N. J. , Nicolaides K. H. 
Published: September 2008

AbstractObjectiveTo evaluate whether measurement of maternal serum inhibin‐A and activin‐A at 11 + 0 to 13 + 6 weeks of gestation, alone or in combination with second‐trimester uterine artery pulsatility measured by Doppler velocimetry, is useful in predicting those women who will develop pre‐eclampsia.MethodsThis was a nested case‐control study of pre‐eclampsia cases with controls matched for gestational age and storage time for the maternal serum. Samples were collected as part of a first‐trimester prenatal chromosomal anomaly screening program. Activin‐A and inhibin‐A were measured using a commercial enzyme‐linked immunosorbent assay and the clinical outcomes were blinded to the operator. All the patients underwent uterine artery Doppler flow velocimetry to measure the mean pulsatility index at 22–24 weeks' gestation.ResultsIn total there were 64 cases with pre‐eclampsia, with 34 delivering prior to 35 weeks of gestation. The control group included 240 cases. In the control group the levels of activin‐A and inhibin‐A did not change across the narrow gestational window and the median levels were 2.16 ng/mL and 231.13 pg/mL, respectively. In the pre‐eclamptic group levels of activin‐A and inhibin‐A were significantly increased, at 2.52 ng/mL and 286.64 pg/mL (1.24 multiples of the median (MoM) and 1.17 MoM, respectively). There was no difference in the median MoM in those delivering prior to 35 weeks and those delivering later. At cut‐offs of the 90th centile of normal, activin‐A and inhibin‐A levels would have identified 20% and 35%, respectively, of cases that would develop pre‐eclampsia. When combined with uterine artery Doppler, activin‐A measurement could have increased the detection rate from 55% to 63% and inhibin‐A measurement could have increased it to 68% at a 5% false positive rate.ConclusionAlthough increased in the first trimester, levels of activin‐A and inhibin‐A are probably too low to make a significant contribution to screening for pre‐eclampsia at this time. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Low‐dose aspirin reduces uteroplacental vascular impedance in early and mid gestation in IVF and ICSI patients: a randomized, placebo‐controlled double‐blind study
Authors: Haapsamo M. , Martikainen H. , Räsänen J. 
Published: September 2008

AbstractObjectiveTo determine whether low‐dose aspirin improves uteroplacental hemodynamics in unselected in‐vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) subjects when medication is started concomitantly with controlled ovarian hyperstimulation.MethodsThirty‐seven pregnant women who had undergone IVF/ICSI and had been randomized to receive 100 mg aspirin (n = 17) or placebo (n = 20) daily, started concomitantly with controlled ovarian hyperstimulation, were included in this study. Doppler ultrasound examination was performed at 6, 10, 13 and 18 weeks' gestation. Uterine artery (UtA) pulsatility index (PI) was calculated and bilateral UtA notching was noted. Subplacental arcuate artery PI was obtained at 6 and 10 weeks' gestation. Umbilical artery (UA) PI and mean velocity were calculated at 10, 13 and 18 weeks' gestation. In the aspirin group there was one early pregnancy miscarriage, and one patient discontinued the study medication owing to early pregnancy bleeding. A total of 15 women in the aspirin group and 20 women in the placebo group underwent the complete ultrasound protocol.ResultsAt 6 weeks' gestation, arcuate artery PI and at 18 weeks' gestation, UtA PI were lower (P < 0.05) in the aspirin group than in the placebo group. At 18 weeks' gestation, bilateral UtA notching tended to be more common in the placebo group (40%) than in the aspirin group (13%) (P = 0.06). UA PI and mean velocity did not differ significantly between the groups.ConclusionLow‐dose aspirin reduces uteroplacental vascular impedance in early and mid pregnancy in unselected IVF/ICSI subjects when medication is started concomitantly with controlled ovarian hyperstimulation. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Hub‐polling‐based IEEE 802.11 PCF with integrated QoS differentiation
Authors: Liqiang Zhao , Jie Zhang , Hailin Zhang 
Published: September 2008

AbstractIEEE 802.11 is one of the most influential wireless LAN (WLAN) standards. Point coordination function (PCF) is its medium access control (MAC) protocol with real‐time traffic (rt‐traffic) quality‐of‐service (QoS) guarantees. In PCF, it is very likely that non‐real‐time traffic (nrt‐traffic) will use the contention free period (CFP) that should be dedicated to traffic having higher priority such as rt‐traffic. Therefore, a modified PCF protocol called MPCF, which is based on hub polling and an integrated QoS differentiation, is presented in this paper. With the integrated QoS differentiation, MPCF can prioritize bandwidth requests according to service classes and QoS requirements. With hub polling, MPCF can reduce the bandwidth for control frames and improve the network throughput. A simple and accurate analytical model is derived and presented in this paper to calculate the system throughput of MPCF. Simulation results show that MPCF protocol is much better than PCF in terms of system capacity and rt‐traffic QoS guarantees. Copyright © 2008 John Wiley & Sons, Ltd.
A review of wind project financing structures in the USA
Authors: Bolinger Mark , Harper John , Karcher Matt 
Published: September 2008

AbstractThe rapid pace of wind power development in the USA over the last decade has outstripped the ability of most project developers to provide adequate equity capital and to make efficient use of project‐related tax benefits. In response, the sector has created novel project financing structures that feature varying combinations of equity capital from project developers and third‐party tax‐oriented investors and, in some cases, commercial debt. While their origins stem from variations in the financial capacity and business objectives of wind project developers, as well as the risk tolerances and objectives of equity and debt providers, each structure is, at its core, designed to manage project risk and to allocate federal tax incentives to those entities that can use them most efficiently. This paper surveys the six principal financing structures through which most new utility‐scale wind projects (excluding utility‐owned projects) in the USA have been financed from 1999 to the present. These structures include simple balance sheet finance, several varieties of all‐equity special allocation partnership ‘flip’ structures and two leveraged structures. In addition to describing each structure's mechanics, the paper also discusses its rationale for use, the types of investors that find it appealing and why, and its relative frequency of use in the market. The paper concludes with a generalized summary of how a developer might choose one structure over another. Copyright © 2008 US Government Work.