bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regression analysis of incomplete medical cost data
Authors: Lin D. Y. 
Published: March 2003

AbstractThe accumulation of medical cost over time for each subject is an increasing stochastic process defined up to the instant of death. The stochastic structure of this process is complex. In most applications, the process can only be observed at a limited number of time points. Furthermore, the process is subject to right censoring so that it is unobservable after the censoring time. These special features of the medical cost data, especially the presence of death and censoring, pose major challenges in the construction of plausible statistical models and the development of the corresponding inference procedures. In this paper, we propose several classes of regression models which formulate the effects of possibly time‐dependent covariates on the marginal mean of cost accumulation in the presence of death or on the conditional means of cost accumulation given specific survival patterns. We then develop estimating equations for these models by combining the approach of generalized estimating equations for longitudinal data with the inverse probability of censoring weighting technique. The resultant estimators are shown to be consistent and asymptotically normal with simple variance estimators. Simulation studies indicate that the proposed inference procedures behave well in practical situations. An application to data taken from a large cancer study reveals that the Medicare enrollees who are diagnosed with less aggressive ovarian cancer tend to accumulate medical cost at lower rates than those with more aggressive disease, but tend to have higher lifetime costs because they live longer. Copyright © 2003 John Wiley & Sons, Ltd.
Truncated negative binomial mixed regression modelling of ischaemic stroke hospitalizations
Authors: Lee Andy H. , Wang K. , Yau Kelvin K. W. , Somerford Peter J. 
Published: March 2003

AbstractA zero‐truncated negative binomial mixed regression model is presented to analyse overdispersed positive count data. The study is motivated by the determination of pertinent risk factors associated with ischaemic stroke hospitalizations. Random effects are incorporated in the linear predictor to adjust for inter‐hospital variations and the dependency of clustered observations using the generalized linear mixed model approach. The method assists hospital administrators and clinicians to estimate the number of subsequent readmissions based on characteristics of the patient at the index stroke. The findings have important implications on resource usage, rehabilitation planning and management of acute stroke care. Copyright © 2003 John Wiley & Sons, Ltd.
An illustration of the modelling of cost and efficacy data from a clinical trial
Authors: Hahn Seokyung , Whitehead Anne 
Published: March 2003

AbstractHealth care providers, purchasers and policy makers need to make informed decisions regarding the provision of cost‐effective care. When a new health care intervention is to be compared with the current standard, an economic evaluation alongside an evaluation of health benefits provides useful information for the decision making process. We consider the information on cost‐effectiveness which arises from an individual clinical trial comparing the two interventions. Recent methods for conducting a cost‐effectiveness analysis for a clinical trial have focused on the net benefit parameter. The net benefit parameter, a function of costs and health benefits, is positive if the new intervention is cost‐effective compared with the standard. In this paper we describe frequentist and Bayesian approaches to cost‐effectiveness analysis which have been suggested in the literature and apply them to data from a clinical trial comparing laparoscopic surgery with open mesh surgery for the repair of inguinal hernias. We extend the Bayesian model to allow the total cost to be divided into a number of different components. The advantages and disadvantages of the different approaches are discussed. In January 2001, NICE issued guidance on the type of surgery to be used for inguinal hernia repair. We discuss our example in the light of this information. Copyright © 2003 John Wiley & Sons, Ltd.
Regression analysis with multiplicative and time‐varying additive regression coefficients with examples from breast and colon cancer
Authors: Zahl Per‐Henrik 
Published: March 2003

AbstractRegression analysis may be used to simplify the representation of mortality rates when there are many significant prognostic covariates or to adjust for confounding effects. The principal request of the regression model in this range of use is to have unbiased parameter estimates. A model with constant multiplicative and time‐varying additive regression coefficients is discussed. The model allows some covariate effects to be multiplicative while allowing others to have a time‐varying additive effect. Thus, it is a mix of classical Cox regression and Aalen's additive risk model. A major characteristic of cancer mortality rates, in contrast to general mortality rates, is that hazard rates, after a potentially initial increase, decrease, although not always tending to zero. Cancer diseases, like breast and colon cancer, have significantly increased cause‐specific mortality rates even 20 years after diagnosis. Another major feature in cancer survival analysis is that many covariate effects are time‐varying. Some covariate effects, like age at diagnosis, may only be significant for a limited time after diagnosis. Furthermore, some treatment procedures may initially decrease the mortality, while the long‐term effect may be opposite. A third issue is that average covariate effects are very often not multiplicative. Estimation is carried out iteratively; the cumulative additive regression functions are estimated non‐parametrically using a least‐squares method and the multiplicative parameters are estimated from the partial likelihood. The method is applied on 3201 female breast cancer and 1372 male colon cancer patients. Copyright © 2003 John Wiley & Sons, Ltd.
Integrating science and management through collaborative learning and better information management
Authors: Bosch O. J. H. , Ross A. H. , Beeton R. J. S. 
Published: March 2003

AbstractAchieving more sustainable land and water use depends on high‐quality information and its improved use. In other words, better linkages are needed between science and management. Since many stakeholders with different relationships to the natural resources are inevitably involved, we suggest that collaborative learning environments and improved information management are prerequisites for integrating science and management. Case studies that deal with resource management issues are presented that illustrate the creation of collaborative learning environments through systems analyses with communities, and an integration of scientific and experiential knowledge of components of the system. This new knowledge needs to be captured and made accessible through innovative information management systems designed collaboratively with users, in forms which fit the users' ‘mental models’ of how their systems work. A model for linking science and resource management more effectively is suggested. This model entails systems thinking in a collaborative learning environment, and processes to help convergence of views and value systems, and make scientists and different kinds of managers aware of their interdependence. Adaptive management provides a mechanism for applying and refining scientists' and managers' knowledge. Copyright © 2003 John Wiley & Sons, Ltd.
Dopamine transporter gene, response to methylphenidate and cerebral blood flow in attention‐deficit/hyperactivity disorder: A pilot study
Authors: Rohde Luis A. , Roman Tatiana , Szobot Claudia , Cunha Renato D. , Hutz Mara H. , Biederman Joseph 
Published: March 2003

AbstractThe homozygosity of the 10‐repeat allele at dopamine transporter gene (DAT1) seems to be associated with a poor response to methylphenidate (MPH) in children with attention‐deficit/hyperactivity disorder (ADHD). This pilot study aimed to simultaneously assess polymorphisms at DAT1, response to MPH, and neuroimaging. Only ADHD children with at least a moderate response to MPH were included. Significantly higher regional cerebral blood flows assessed by single photon emission computerized tomography (SPECT) were detected in medial frontal and left basal ganglia areas in children with homozygosity for the 10‐repeat allele at DAT1 gene (n = 4) than in children without this genotype (n = 4) (P < 0.05). These findings provide a preliminary connection between pharmacogenetics and neurobiological investigations on stimulant treatment of ADHD. Synapse 48:87–89, 2003. © 2003 Wiley‐Liss, Inc.
Behavioral and subthalamic effects of combining a fetal ventral mesencephalic transplant in striatum with an electrolytic lesion of the entopeduncular nucleus in the rat with a unilateral 6‐OHDA lesion of substantia nigra
Authors: Olds M.E. , Jacques D.B. , Kopyov O. 
Published: March 2003

AbstractBehavioral and electrophysiological methods were used to determine whether a transplant of dopamine‐rich fetal tissue in striatum combined with an electrolytic lesion of the entopeduncular nucleus have additive effects in the unilaterally lesioned rat model for Parkinson's disease. The subjects were rats with the left substantia nigra lesioned with 6‐hydroxydopamine (6‐OHDA) and responding to systemic amphetamine with rotation toward the side of the lesion (ipsilateral rotation). The motor response to amphetamine was fractionated into six aspects, half reflecting the unilateral deafferentation in striatum and half representing those aspects of the response evoked in normal rats. After collection of baseline values, 25 rotators received a transplant of fetal ventral mesencephalic tissue in the left striatum and 20 received a transplant and, at the same time, an electrolytic lesion of the left entopeduncular nucleus. Testing for the motor response to amphetamine resumed after 4 weeks of recovery and continued at weekly intervals for 5 weeks. Upon completion of these tests, each rotator was implanted with multiple electrodes in the subthalamic nucleus. After recovery, multiunit responses to amphetamine and apomorphine were recorded from several electrodes in parallel during the motor response to the drugs. In rotators with transplant only, treatment with amphetamine evoked oral stereotypy and an attenuated ipsilateral rotation response. In rotators with combined transplant and entopeduncular lesion, ipsilateral rotation did not change or increased. Subthalamic responses to amphetamine and apomorphine were larger in rotators with combined transplant and entopeduncular lesion than in rotators with transplant alone. These findings indicate that the combination of transplant and pallidotomy in the 6‐OHDA rat model for parkinsonism does not lead to additive benefits, an effect that may have been due to the nonselectivity of the electrolytic damage and/or of the lesion extending beyond the entopeduncular nucleus into the lateral hypothalamus. Synapse 48:90–99, 2003. © 2003 Wiley‐Liss, Inc.
Differential effects of atypical and typical antipsychotic drugs on N‐methyl‐D‐aspartate‐ and electrically evoked responses in the pyramidal cells of the rat medial prefrontal cortex
Authors: Ninan Ipe , Jardemark Kent E. , Wang Rex Y. 
Published: March 2003

AbstractIn the present study, we have demonstrated that atypical antipsychotic drugs (APDs, e.g., clozapine, olanzapine, risperidone, and quetiapine) and atypical APD candidates (e.g., M100907 and Y‐931) share a common property in facilitating responses evoked by electrical stimulation of the forceps minor and by N‐methyl‐D‐aspartate (NMDA), but not (±)‐α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA), in pyramidal cells of the medial prefrontal cortex (mPFC). The concentrations of these drugs to exert their action are in a clinically relevant range. Although haloperidol has shown a considerably smaller potentiation of NMDA‐evoked current at 50 and 100 nM, it consistently depressed the AMPA‐induced current. Chlorpromazine and loxapine failed to modulate significantly NMDA‐ or AMPA‐induced current in the pyramidal cells. Moreover, haloperidol and loxapine demonstrated depression of excitatory postsynaptic currents, whereas chlorpromazine did not show any effect. These findings combined indicate that atypical, but not typical, APDs augment glutamatergic neurotransmission in pyramidal cells of the mPFC. We propose that the beneficial effect of atypical APDs in cognitive dysfunction and negative symptoms in schizophrenia is due to their ability to enhance glutamatergic neurotransmission in the PFC and functionally related limbic structures. Our results further suggest the possible use of glutamatergic neurotransmission in the mPFC as a model for screening and studying the action of potential atypical APDs. Synapse 48:66–79, 2003. © 2003 Wiley‐Liss, Inc.
Different brain kinetics of two sigma1 receptor ligands, [3H](+)‐pentazocine and [11C]SA4503, by P‐glycoprotein modulation
Authors: Kawamura Kazunori , Kobayashi Tadayuki , Matsuno Kiyoshi , Ishiwata Kiichi 
Published: March 2003

AbstractWe compared the brain kinetics of radiolabeled (+)‐pentazocine and SA4503, which have a high and selective affinity for sigma1 receptors. Brain uptake of [11C]SA4503 was high after intravenous injection followed by a gradual decrease in mice, whereas that of [3H](+)‐pentazocine rapidly decreased. The brain uptake of the two radioligands was dose‐dependently reduced, but the reduction of [3H](+)‐pentazocine was found at higher doses. Percentages of the saturable binding of [3H](+)‐pentazocine was much lower than that of [11C]SA4503. The brain uptake of [3H](+)‐pentazocine was greatly blocked by SA4503 at a dose of 2 μmol/kg, while that of [11C]SA4503 was blocked by (+)‐pentazocine at a dose of 20 μmol/kg and over. When mice were treated with cyclosporin A, a P‐glycoprotein modulator, the uptake of [3H](+)‐pentazocine was enhanced, but that of [11C]SA4503 was not. Under control and P‐glycoprotein‐modulated conditions, the brain uptake of both radioligands was reduced by haloperidol, another representative sigma receptor ligand, to a different extent. We concluded that the P‐glycoprotein modulation resulted in the different brain kinetics of the two radioligands. The radiolabeled SA4503 is suitable as an in vivo probe, but radiolabeled (+)‐pentazocine is not. Synapse 48:80–86, 2003. © 2003 Wiley‐Liss, Inc.
Country factor differentials as determinants of FDI flow to China
Authors: Zhao Hongxin 
Published: March 2003

AbstractGiven the large size and rapid growth of foreign direct investment (FDI) in China, a systematic
analysis of the connection between FDI and the characteristics of source countries provides clearer insights
into the roles of home‐country factors in the vast but still fast‐growing foreign investment in
China. Unlike the existing mainstream studies of FDI in China, this analysis focuses on the effects of
country‐factor differentials (between investing countries and China) on the FDI flow to China.
Based on data from 21 source countries over a period of 17 years, this paper examines the impacts of eight
variables in three sets of country factors, namely market conditions, risk, and financial factors. The
statistical results show that, while the market‐condition variables and the high values of source country
currencies positively influenced the flow of FDI to China, the relatively high costs of capital borrowing and
political and operational risks in China inhibited the flow of FDI. © 2003 Wiley Periodicals, Inc.
Arsenic, lead, and other trace elements in soils contaminated with pesticide residues at the Hanford site (USA)
Authors: Yokel Jerry , Delistraty Damon A. 
Published: March 2003

AbstractThe primary purpose of this study was to characterize arsenic (As) and lead (Pb) concentrations in former orchard soils contaminated with lead arsenate pesticides at the Hanford site in Washington state (USA). Surface samples (n = 31) were collected from former orchard soils (in cultivation during the pre‐Hanford period) at five locations at the 100 Areas and at one location at the Old Hanford Townsite (OHT). Another set of samples (n = 17) was collected over a soil depth interval of 10–50 cm at the four locations with the highest As and Pb surface concentrations. All samples were analyzed for 22 trace elements (including As and Pb) with inductively coupled plasma–atomic emission spectrometry (ICP–AES). The mean, standard deviation, and range for As in the surface soils were 30, 61, and 2.9–270 mg/kg dry wt, respectively. The corresponding statistics for Pb were 220, 460, and 6.5–1900 mg/kg dry wt, respectively. As and Pb concentrations in the surface soils were positively and significantly correlated (r = 0.91, Bonferroni p < 0.05). Descriptive statistics and bivariate correlations were also computed for other trace elements. As and Pb mean concentrations in the surface soils each differed significantly (p < 0.05) among Hanford locations, with the highest concentrations at the 100‐H and 100‐F Areas. Although both As and Pb mean concentrations decreased with soil depth, regression and correlation coefficients only, for Pb significantly differed from zero (b = −0.0372, r = −0.805, Bonferroni p < 0.05). Compared with data in the literature As and Pb concentrations found in this study exceeded background levels but were typical of orchard soils. Furthermore, mean As and Pb soil concentrations were in the range of various toxicological benchmarks derived for protection of human and ecological receptors. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 104–114, 2003
Three‐dimensional ultrasound fetal lung volume measurement: a systematic study comparing the multiplanar method with the rotational (VOCAL) technique
Authors: Kalache K. D. , Espinoza J. , Chaiworapongsa T. , Londono J. , Schoen M. L. , Treadwell M. C. , Lee W. , Romero R. 
Published: March 2003

AbstractObjectivesThis study was designed to compare a conventional multiplanar technique for three‐dimensional (3D) ultrasound measurement of fetal lung volume with a rotational method using VOCAL™ (Virtual Organ Computer‐aided AnaLysis).MethodsThirty‐two fetuses with a variety of conditions at risk for pulmonary hypoplasia were studied. 3D volume data sets of the fetal lungs were acquired using a commercially available ultrasound system. The right and left lung volumes were calculated separately using VOCAL and the multiplanar technique. The level of agreement between two independent observers in categorizing the 3D volume data set as measurable or non‐measurable was determined. The interobserver and intermethod variabilities were also evaluated for both methods.ResultsThe intermethod variability was excellent (correlation r = 0.93 and r = 0.96 for the left and right lung, respectively), and there was substantial agreement between the results of both approaches (limits of agreement − 4.4 to 8.9 and − 3.4 to 4.8 mL for the right and left lung, respectively). Fetal lung estimation with VOCAL had a significantly higher interobserver variability than the multiplanar technique. Interobserver agreement in categorizing lung volume data sets as measurable or non‐measurable was lower when VOCAL was used.ConclusionFetal lung volume measurements can be undertaken interchangeably using the multiplanar technique or the rotational method with VOCAL. However, the latter was less reproducible (lower degree of agreement and significantly higher interobserver variability) than the former. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Regression modeling of motion with endpoint constraints
Authors: Faraway Julian 
Published: March 2003

AbstractA statistical model is described for the prediction of reaching motions using motion capture data on a variety of individuals performing reaches to a range of targets. The modeling approach allows for various inputs such as the stature, age and the location of the target to be specified and then computes the predicted trajectories of the kinematic chains of body markers necessary to place an object exactly at the specified target. Functional regression methods for modeling time‐varying angles and other quantities as well as trajectories are described. A new parameterization of posture is described that facilitates the satisfaction of specific endpoints such as placing an object at a target. The methodology is illustrated with an application to two‐handed standing lifts. Copyright © 2003 John Wiley & Sons, Ltd.
Modelling of Offshore Wind Turbine Wakes with the Wind Farm Program FLaP
Authors: Lange Bernhard , Waldl Hans‐Peter , Guerrero Algert Gil , Heinemann Detlev , Barthelmie Rebecca J. 
Published: March 2003

AbstractThe wind farm layout program FLaP estimates the wind speed at any point in a wind farm and the power output of the turbines. The ambient flow conditions and the properties of the turbines and the farm are used as input. The core of the program is an axisymmetric wake model describing the wake behind one rotor. Here an approach based on the simplified Reynolds equation with eddy viscosity closure is chosen. The single‐wake model is combined with a model for the vertical wind speed profile and a wind farm model, which takes care of the interaction of all wakes in a wind farm. The wake model has been extended to improve the description of wake development in offshore conditions, especially the low ambient turbulence and the effect of atmospheric stability. Model results are compared with measurements from the Danish offshore wind farm Vindeby. Vertical wake profiles and mean turbulence intensities in the wake are compared for single‐, double‐ and quintuple‐wake cases with different mean wind speed, turbulence intensity and atmospheric stability. It is found that within the measurement uncertainties the results of the wake model compare well with the measurements for the most important ambient conditions. The effect of the low turbulence intensity offshore on the wake development is modelled well for Vindeby wind farm. Deviations are found when atmospheric stability deviates from near‐neutral conditions. For stable atmospheric conditions both the free vertical wind speed profile and the wake profile are not modelled satisfactorily. Copyright © 2003 John Wiley & Sons, Ltd.
Proteome analysis of recombinant xylose‐fermenting Saccharomyces cerevisiae
Authors: Salusjärvi Laura , Poutanen Marjo , Pitkänen Juha‐Pekka , Koivistoinen Heini , Aristidou Aristos , Kalkkinen Nisse , Ruohonen Laura , Penttilä Merja 
Published: March 2003

AbstractIntroduction of an active xylose utilization pathway into Saccharomyces cerevisiae, which does not naturally ferment pentose sugars, is likely to have a major impact on the overall cellular metabolism as the carbon introduced to the cells will now flow through the pentose phosphate pathway. The metabolic responses in the recombinant xylose‐fermenting S. cerevisiae were studied at the proteome level by comparative two‐dimensional gel electrophoresis of cellular proteins within a pH range of 3–10. Glucose‐limited chemostat cultivations and corresponding chemostat cultivations performed in media containing xylose as the major carbon source were compared. The cultivations were studied in aerobic and anaerobic metabolic steady states and in addition at time points 5, 30 and 60 min after the switch‐off of oxygen supply. We identified 22 proteins having a significant abundance difference on xylose compared to glucose, and 12 proteins that responded to change from aerobic to anaerobic conditions on both carbon sources. On xylose in all conditions studied, major changes were seen in the abundance of alcohol dehydrogenase 2 (Adh2p), acetaldehyde dehydrogenases 4 and 6 (Ald4p and Ald6p), and DL‐glycerol 3‐phosphatase (Gpp1p). Our results give indications of altered metabolic fluxes especially in the acetate and glycerol pathways in cells growing on xylose compared to glucose. Copyright © 2003 John Wiley & Sons, Ltd.