bluuebunny/crossref_metadata_2025_split huggingface dataset:
On Distribution-Weighted Partial Least Squares with Diverging Number of Highly Correlated Predictors
Authors: Zhu Li-Ping , Zhu Li-Xing 
Published: February 2009

SummaryBecause highly correlated data arise from many scientific fields, we investigate parameter estimation in a semiparametric regression model with diverging number of predictors that are highly correlated. For this, we first develop a distribution-weighted least squares estimator that can recover directions in the central subspace, then use the distribution-weighted least squares estimator as a seed vector and project it onto a Krylov space by partial least squares to avoid computing the inverse of the covariance of predictors. Thus, distrbution-weighted partial least squares can handle the cases with high dimensional and highly correlated predictors. Furthermore, we also suggest an iterative algorithm for obtaining a better initial value before implementing partial least squares. For theoretical investigation, we obtain strong consistency and asymptotic normality when the dimension p of predictors is of convergence rate O{n1/2/ log (n)} and o(n1/3) respectively where n is the sample size. When there are no other constraints on the covariance of predictors, the rates n1/2 and n1/3 are optimal. We also propose a Bayesian information criterion type of criterion to estimate the dimension of the Krylov space in the partial least squares procedure. Illustrative examples with a real data set and comprehensive simulations demonstrate that the method is robust to non-ellipticity and works well even in ‘small n–large p’ problems.
Splines for Financial Volatility
Authors: Audrino Francesco , Bühlmann Peter 
Published: February 2009

SummaryWe propose a flexible generalized auto-regressive conditional heteroscedasticity type of model for the prediction of volatility in financial time series. The approach relies on the idea of using multivariate B-splines of lagged observations and volatilities. Estimation of such a B-spline basis expansion is constructed within the likelihood framework for non-Gaussian observations. As the dimension of the B-spline basis is large, i.e. many parameters, we use regularized and sparse model fitting with a boosting algorithm. Our method is computationally attractive and feasible for large dimensions. We demonstrate its strong predictive potential for financial volatility on simulated and real data, and also in comparison with other approaches, and we present some supporting asymptotic arguments.
On-Line Expectation–Maximization Algorithm for latent Data Models
Authors: Cappé Olivier , Moulines Eric 
Published: February 2009

SummaryWe propose a generic on-line (also sometimes called adaptive or recursive) version of the expectation–maximization (EM) algorithm applicable to latent variable models of independent observations. Compared with the algorithm of Titterington, this approach is more directly connected to the usual EM algorithm and does not rely on integration with respect to the complete-data distribution. The resulting algorithm is usually simpler and is shown to achieve convergence to the stationary points of the Kullback–Leibler divergence between the marginal distribution of the observation and the model distribution at the optimal rate, i.e. that of the maximum likelihood estimator. In addition, the approach proposed is also suitable for conditional (or regression) models, as illustrated in the case of the mixture of linear regressions model.
Covariance-Regularized Regression and Classification for high Dimensional Problems
Authors: Witten Daniela M. , Tibshirani Robert 
Published: February 2009

SummaryWe propose covariance-regularized regression, a family of methods for prediction in high dimensional settings that uses a shrunken estimate of the inverse covariance matrix of the features to achieve superior prediction. An estimate of the inverse covariance matrix is obtained by maximizing the log-likelihood of the data, under a multivariate normal model, subject to a penalty; it is then used to estimate coefficients for the regression of the response onto the features. We show that ridge regression, the lasso and the elastic net are special cases of covariance-regularized regression, and we demonstrate that certain previously unexplored forms of covariance-regularized regression can outperform existing methods in a range of situations. The covariance-regularized regression framework is extended to generalized linear models and linear discriminant analysis, and is used to analyse gene expression data sets with multiple class and survival outcomes.
Subthalamic deep brain stimulation and impulse control in Parkinson’s disease
Authors: Hälbig T. D. , Tse W. , Frisina P. G. , Baker B. R. , Hollander E. , Shapiro H. , Tagliati M. , Koller W. C. , Olanow C. W. 
Published: February 2009

Background and purpose:  Experimental studies suggest that deep brain stimulation (DBS) of the subthalamic nucleus (STN) induces impulsivity in patients with Parkinson’s disease (PD). The purpose of this study was to assess various measures of impulse control in PD patients with STN DBS in comparison to patients receiving medical therapy.Methods:  In a cross‐sectional evaluation, 53 consecutively eligible patients were assessed for impulsivity with the Barratt Impulsiveness Scale, for impulse control disorders (ICDs) using the Minnesota Impulsive Disorders Interview, and for obsessive–compulsive symptoms using the Maudsley Obsessional‐Compulsive Inventory.Results:  Independent samples t‐tests revealed that compulsivity scores were not different between DBS patients and patients without DBS. However, impulsivity scores were significantly higher in DBS patients. Additionally, ICDs were observed in 3 of 16 (19%) DBS patients and in 3 of 37 (8%) medically treated patients. No association was found between the use of dopamine agonists and impulsivity in DBS patients.Conclusions:  Our data suggest that screening for impulsivity and ICDs should be performed prior to DBS, and that patients should be monitored for these problems during follow‐up. Prospective trials are needed to confirm the findings of this exploratory study and to elucidate the reasons of a possible induction of impulsivity by STN DBS.
Increased levels of inflammatory chemokines in amyotrophic lateral sclerosis
Authors: Kuhle J. , Lindberg R. L. P. , Regeniter A. , Mehling M. , Steck A. J. , Kappos L. , Czaplinski A. 
Published: February 2009

Background and purpose:  Amyotrophic lateral sclerosis (ALS) is classically assumed to be a neurodegenerative disorder. Inflammation has been observed in CNS tissue in ALS patients. We investigated the expression and prognostic relevance of proinflammatory chemokines in ALS.Methods:  We analyzed nine chemokines, eotaxin, eotaxin‐3, IL‐8, IP‐10, MCP‐1, MCP‐4, macrophage derived chemokine (MDC), macrophage inflammatory protein‐1β (MIP‐1β), and serum thymus and activation‐ regulated chemokine (TARC) in serum and cerebrospinal fluid (CSF) of 20 ALS‐ and 20 non‐inflammatory neurological disease (NIND)‐patients.Results:  MCP‐1 and IL‐8 levels in CSF in ALS were significantly higher than in NIND (1304 pg/ml vs. 1055 pg/ml, P = 0.013 and 22.7 pg/ml vs. 18.6 pg/ml, P = 0.035). The expression of MCP‐1 and IL‐8 were higher in CSF than in serum (P < 0.001). There was a trend towards higher MCP‐1 CSF levels in ALS patients with shorter time between first symptoms and diagnosis (r = −0.407; P = 0.075).Conclusions:  We confirmed previous findings of increased MCP‐1 levels in CSF of ALS patients. Furthermore, increased levels of IL‐8 in CSF suggest a stimulation of a proinflammatory cytokine cascade after microglia activation. We found a tendency for higher MCP‐1 values in patients with a shorter diagnostic delay, who are known to have also a shorter survival. This may suggest an association of higher MCP‐1 levels with rapidly progressing disease.
Diversity in trade union membership: a typology based on the study of a Spanish trade union
Authors: Alós Ramon , Jódar Pere , Martí Joel , Artiles Antonio Martín , Ortiz Luis 
Published: February 2009

ABSTRACTWhile existing literature on the changing nature of trade union membership concentrates on unidimensional differences between members, this article proposes a multidimensional typology, which considers demographic characteristics as well as labour market position and length of union membership. Our results allow the identification of different member profiles; these are significantly associated to differences in employment conditions, work participation, job satisfaction and union activism. In the last section of the article, we discuss the practical implications that these different member profiles may have for union policy and organisation.
What do aqueous geothermometers really tell us?
Authors: FERGUSON G. , GRASBY S. E. , HINDLE S. R. 
Published: February 2009

AbstractThe application of chemical geothermometry to shallow groundwaters or spring discharge assumes that there is minimal mixing or re‐equilibration of water as it travels from depth to the surface. In this study, we examine the potential for mixing and re‐equilibration by examining heat and fluid flow along crustal‐scale faults in tectonic geothermal systems. Numerical modeling results indicate that maximum in situ temperatures could be under‐predicted by up to 30% due to mixing of fluids that enter the fault at different depths. This, coupled with the depression of isotherms by downward groundwater flow in the hanging wall, could cause underestimates of maximum circulation depth of greater than 80% in extreme cases. Kinetics does not favor re‐equilibration in the shallower portions of faults due to low temperatures and higher fluid velocities. However, in areas of deeper circulation or higher heat flow such reactions are possible.
Management measures to control a feline leukemia virus outbreak in the endangered Iberian lynx
Authors: López G. , López‐Parra M. , Fernández L. , Martínez‐Granados C. , Martínez F. , Meli M. L. , Gil‐Sánchez J. M. , Viqueira N. , Díaz‐Portero M. A. , Cadenas R. , Lutz H. , Vargas A. , Simón M. A. 
Published: February 2009

AbstractThe feline leukemia virus (FeLV) is a retrovirus that affects domestic cats all over the world. Its pathogenic effects generally include anemia, immunosuppression or tumors. Dissemination over populations is linked to cat sociality, because the virus is transmitted by direct contact. Although the domestic cat is its common host, FeLV infection has also been described in some wild felids. In the Iberian lynxLynx pardinus, some sporadic FeLV infection cases have been reported since 1994, but an outbreak with the involvement of several animals has never been described until now. During spring 2007, an FeLV outbreak hit the Doñana (SW Spain) population. The infection rapidly spread throughout the densest subpopulation throughout Doñana. Infected animals showed very acute anemic disease, most of them dying in <6 months. To avoid FeLV dissemination, a control program was carried out that included removal of viremic lynxes, vaccination of negative individuals and reduction of the feral cat population. The program was implemented both in Doñana and in Sierra Morena populations. In Doñana, around 80% of the total lynx population and 90% of the outbreak focus subpopulation were evaluated. Seven out of the 12 infected individuals found died and two reverted to latency; the remaining viremic animals have been kept in captivity. The outbreak appears to have been successfully confined to the subpopulation where the virus appeared and no more cases have been found since August 2007. In the larger Sierra Morena population, 8% of the lynx population was surveyed. Thirty‐four uninfected Iberian lynxes were vaccinated at least once. The FeLV prevalence was found to be 27% in the Doñana population and 0% in the Sierra Morena population.
Anti‐amnesic properties of (±)‐PPCC, a novel sigma receptor ligand, on cognitive dysfunction induced by selective cholinergic lesion in rats
Authors: Antonini Vuokko , Prezzavento Orazio , Coradazzi Marino , Marrazzo Agostino , Ronsisvalle Simone , Arena Emanuela , Leanza Giampiero 
Published: February 2009

J. Neurochem. (2009)109, 744–754.AbstractPrevious studies have reported that selective sigma‐1 agonists may improve cognitive abilities in experimental animals possibly via a cholinergic mechanism. However, the issue of a direct action on to sigma‐1 receptors in memory‐related brain areas has been much less investigated. The newly synthetised compound methyl(1R,2S/1S,2R)‐2‐[4‐hydroxy‐4‐phenylpiperidin‐1‐yl)methyl]‐1‐(4‐methylphenyl) cyclopropanecarboxylate [(±)‐PPCC] has recently been shown to possess high affinity for the sigma‐1 receptor where it specifically acts as an agonist. Here, the functional effects of (±)‐PPCC were investigated in rat models of mild or severe cognitive dysfunction based on a sub‐total (≤ 70–80%) or complete (≥ 90–95%) central cholinergic depletion induced by different doses of the selective immunotoxin 192 IgG‐saporin injected intraventricularly. At 5–6 weeks post‐surgery, the lesioned animals exhibited dose‐dependent deficits in reference memory, as assessed using the Morris water maze task, whereas working memory abilities, evaluated using the radial arm water maze task, appeared equally impaired in the two dose groups. Daily treatment with (±)‐PPCC significantly improved both reference and working memory performance in all lesioned animals but it did not affect intact or sham‐lesioned subjects. In a separate test, treatment with (±)‐PPCC reversed the learning deficits induced by the muscarinic receptor antagonist atropine sulphate in both control and mild‐lesioned rats. The effect was blocked in lesioned, but not normal animals by pre‐treatment with the sigma‐1 antagonistN‐[2‐(3,4‐dichlorophenyl)ethyl]‐N‐methyl‐2‐(dimethylamino)ethylamine. The results suggest that (±)‐PPCC may efficiently ameliorate perturbed cognitive abilities, and that these anti‐amnesic effects most probably occur via a direct interaction of the compound with sigma‐1 receptors.
Enriched environment protects the nigrostriatal dopaminergic system and induces astroglial reaction in the 6‐OHDA rat model of Parkinson’s disease
Authors: Anastasía Agustín , Torre Luciana , De Erausquin Gabriel A. , Mascó Daniel H. 
Published: February 2009

J. Neurochem. (2009) 109, 755–765.AbstractEnriched environment (EE) is neuroprotective in several animal models of neurodegeneration. It stimulates the expression of trophic factors and modifies the astrocyte cell population which has been said to exert neuroprotective effects. We have investigated the effects of EE on 6‐hydroxydopamine (6‐OHDA)‐induced neuronal death after unilateral administration to the medial forebrain bundle, which reaches 85–95% of dopaminergic neurons in the substantia nigra after 3 weeks. Continuous exposure to EE 3 weeks before and after 6‐OHDA injection prevents neuronal death (assessed by tyrosine hydroxylase staining), protects the nigrostriatal pathway (assessed by Fluorogold retrograde labeling) and reduces motor impairment. Four days after 6‐OHDA injection, EE was associated with a marked increase in glial fibrillary acidic protein staining and prevented neuronal death (assessed by Fluoro Jade‐B) but not partial loss of tyrosine hydroxylase staining in the anterior substantia nigra. These results robustly demonstrate that EE preserves the entire nigrostriatal system against 6‐OHDA‐induced toxicity, and suggests that an early post‐lesion astrocytic reaction may participate in the neuroprotective mechanism.
Surveillance protocols for management of invasive plants: modelling Chilean needle grass (Nassella neesiana) in Australia
Authors: Fox J. C. , Buckley Y. M. , Panetta F. D. , Bourgoin J. , Pullar D. 
Published: February 2009

AbstractAim  To develop a surveillance support model that enables prediction of areas susceptible to invasion, comparative analysis of surveillance methods and intensity and assessment of eradication feasibility. To apply the model to identify surveillance protocols for generalized invasion scenarios and for evaluating surveillance and control for a context‐specific plant invasion.Location  Australia.Methods  We integrate a spatially explicit simulation model, including plant demography and dispersal vectors, within a Geographical Information System. We use the model to identify effective surveillance protocols using simulations of generalized plant life‐forms spreading via different dispersal mechanisms in real landscapes. We then parameterize the surveillance support model for Chilean needle grass [CNG; Nassella neesiana (Trin. & Rupr.) Barkworth], a highly invasive tussock grass, which is an eradication target in south‐eastern Queensland, Australia.Results  General surveillance protocols that can guide rapid response surveillance were identified; suitable habitat that is susceptible to invasion through particular dispersal syndromes should be targeted for surveillance using an adaptive seek‐and‐destroy method. The search radius of the adaptive method should be based on maximum expected dispersal distances. Protocols were used to define a surveillance strategy for CNG, but simulations indicated that despite effective and targeted surveillance, eradication is implausible at current intensities.Main conclusions  Several important surveillance protocols emerged and simulations indicated that effectiveness can be increased if they are followed in rapid response surveillance. If sufficient data are available, the surveillance support model should be parameterized to target areas susceptible to invasion and determine whether surveillance is effective and eradication is feasible. We discovered that for CNG, regardless of a carefully designed surveillance strategy, eradication is implausible at current intensities of surveillance and control and these efforts should be doubled if they are to be successful. This is crucial information in the face of environmentally and economically damaging invasive species and large, expensive and potentially ineffective control programmes.
Contrasted impacts of climate change on stream fish assemblages along an environmental gradient
Authors: Buisson Laëtitia , Grenouillet Gaël 
Published: February 2009

AbstractAim  To investigate the potential impacts of climate change on stream fish assemblages in terms of species and biological trait diversity, composition and similarity.Location  One‐thousand one‐hundred and ten stream sections in France.Methods  We predicted the future potential distribution of 35 common stream fish species facing changes in temperature and precipitation regime. Seven different species distribution models were applied and a consensus forecast was produced to limit uncertainty between single‐models. The potential impacts of climate change on fish assemblages were assessed using both species and biological trait approaches. We then addressed the spatial distribution of potential impacts along the upstream–downstream gradient.Results  Overall, climate change was predicted to result in an increase in species and trait diversity. Species and trait composition of the fish assemblages were also projected to be highly modified. Changes in assemblages’ diversity and composition differed strongly along the upstream–downstream gradient, with upstream and midstream assemblages more modified than downstream assemblages. We also predicted a global increase in species and trait similarity between pairwise assemblages indicating a future species and trait homogenization of fish assemblages. Nevertheless, we found that upstream assemblages would differentiate, whereas midstream and downstream assemblages would homogenize. Our results suggested that colonization could be the main driver of the predicted homogenization, while local extinctions could result in assemblage differentiation.Main conclusions  This study demonstrated that climate change could lead to contrasted impacts on fish assemblage structure and diversity depending on the position along the upstream–downstream gradient. These results could have important implications in terms of ecosystem monitoring as they could be useful in establishing areas that would need conservation prioritization.
Antegrade pulsatile arterial‐like flow in human limb veins at increased intravascular pressure
Authors: Kölegård Roger , Eiken Ola 
Published: February 2009

SummaryAim: The purpose was to study the effects of moderately to markedly increased local intravascular pressures on the flow characteristics in human limb veins.Methods: The subject was either seated inside a pressure chamber with one arm slipped through a hole in the chamber door (n = 7) or positioned supine with a lower leg extended to the outside (n = 15). By increasing chamber pressure, transmural pressure in the vessels of the test limb was increased up to +150 mmHg for the arm and +240 mmHg for the leg. Venous flow profiles and arterial flow and vessel diameters were measured with ultrasonographic/Doppler techniques. The arm vessels were studied before and during blocking of the blood flow (BBF) through the hand.Results: Antegrade, pulsatile, arterial‐like flow were observed at high distending pressures in the brachial and radial veins in all subjects and in ∼50% of the subjects also in the cephalic vein and posterior tibial veins. In five of seven subjects, blood flow in the brachial vein remained pulsatile even during BBF.Conclusion: That pulsatile flow was observed in all veins may suggest that moderately to markedly elevated intravascular pressures induce propagation of pulse waves from the arteries via the capillaries to the veins, and/or induce considerable arteriovenous shunting, by forcing open arteriovenous anastomoses.
Assessing the Effects of Maternal Symptoms and Homelessness on the Mental Health Problems in their Children
Authors: Harpaz‐Rotem Ilan , Rosenheck Robert A. , Desai Rani 
Published: February 2009

Objective:  This study examines the longitudinal association between measures of child well being and maternal posttraumatic stress disorder symptoms, homelessness, substance abuse, and other psychiatric conditions.Method:  A sample of 142 mothers who were veterans of the US armed forces were assessed at program entry and every three months thereafter for one year. A repeated‐measures with mixed‐effects analytic strategy was used to assess the association of children’s mental health, school enrolment and attendance with measures of maternal psychiatric symptoms and homelessness.Results:  Significant associations between mothers’ psychiatric symptoms and child well‐being were identified. However, the multivariable mixed‐models suggest that increased depression and anxiety symptoms among children were associated primarily with mothers’ PTSD, and not depression, symptoms.Conclusions:  These findings provide evidence of an association between maternal and child mental health and may suggest that treating maternal PTSD symptoms may also benefit children, regardless of whether the child was also exposed to the traumatic experience.
INVESTORS ADJUST EXPECTATIONS AROUND SELL‐SIDE ANALYST REVISIONS IN IPO RECOMMENDATIONS
Authors: Bagchee Deepika 
Published: February 2009

AbstractIn this article I compare investor response to sell‐side analyst recommendation revisions of initial public offering (IPO) firms in the first three years after issue with that of a benchmark control sample of firms that have been public longer. I test whether investors in IPO firms adjust their initially optimistic expectations as information about new issues is released and uncertainty is resolved. In support of my hypothesis that investors adjust expectations downward, I find abnormally negative returns around analyst revisions of IPO firm recommendations. Additionally, I find the effect of analyst revisions on long‐run performance of IPO firms is economically significant.