bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predictors of Neurocognitive Decline after Carotid Endarterectomy
Authors: Mocco J , Wilson David A. , Komotar Ricardo J. , Zurica Joseph , Mack William J. , Halazun Hadi J. , Hatami Raheleh , Sciacca Robert R. , Connolly E Sander , Heyer Eric J. 
Published: April 2006

Abstract

OBJECTIVE:
Although the incidence of stroke after carotid endarterectomy (CEA) is low (1–3%), approximately 25% of patients experience subtle declines in postoperative neuropsychometric function. No studies have investigated the risk factors for this neurocognitive change. We sought to identify predictors of postoperative neurocognitive dysfunction.

METHODS:
We enrolled 186 CEA patients, with both symptomatic and asymptomatic stenosis, to undergo a battery of neuropsychometric tests preoperatively and on postoperative Days 1 and 30. Neurocognitive dysfunction was defined as a two standard deviation decline in performance compared with a similarly aged control group of lumbar laminectomy patients. Univariate logistic regression was performed for age, sex, obesity, smoking, symptomatology, diabetes mellitus, hypertension, hypercholesterolemia, use of statin medication, previous myocardial infarction, previous CEA, operative side, duration of surgery, duration of carotid cross-clamp, and weight-adjusted doses of midazolam and fentanyl. Variables achieving univariate P&lt;0.10 were included in a multivariate analysis. Data is presented as (odds ratio, 95% confidence interval, P-value).

RESULTS:
Eighteen and 9% of CEA patients were injured on postoperative Days 1 and 30, respectively. Advanced age predicted neurocognitive dysfunction on Days 1 and 30 (1.93 per decade, 1.15–3.25, 0.01; and 2.57 per decade, 1.01–6.51, 0.049, respectively). Additionally, diabetes independently predicted injury on Day 30 (4.26, 1.15–15.79, 0.03).

CONCLUSIONS:
Advanced age and diabetes predispose to neurocognitive dysfunction after CEA. These results are consistent with risk factors for neurocognitive dysfunction after coronary bypass and major stroke after CEA, supporting an underlying ischemic pathophysiology. Further work is necessary to determine the role these neurocognitive deficits may play in appropriately selecting patients for CEA.
Postoperative Radiosurgery for Malignant Spinal Tumors
Authors: Rock Jack P. , Ryu Samuel , Shukairy Mohammad S. , Yin Fang-Fang , Sharif Aktham , Schreiber Faye , Abdulhak Muwaffak , Kim Jae Ho , Rosenblum Mark L. 
Published: April 2006

AbstractOBJECTIVE:Although, as a primary therapy, radiosurgery for spinal tumors is becoming more common in clinical practice and is associated with encouraging clinical results, we wanted to evaluate outcomes after radiosurgery in a series of postoperative patients.METHODS:We examined the medical records of 18 postoperative patients who received radiosurgical treatment to their residual spinal tumors: metastatic carcinoma (10), sarcoma (3), multiple myeloma/plasmacytoma (4), and giant cell tumor (1). Marginal radiosurgical doses ranged from 6 to 16 Gy (mean, 11.4 Gy) prescribed to the 90% isodose line. All regions of the spine received treatment: 2 cervical, 15 thoracic, and 1 lumbosacral. The volume of irradiated spinal elements receiving 30, 50, and 80% of the total dose ranged from 0.51 to 11.05, 0.19 to 6.34, and 0.06 to 1.73 cm3, respectively. Treatment sessions (i.e., patient in to patient out of the room) varied between 20 and 40 minutes. Follow-up ranged from 4 to 36 months (median, 7 mo).RESULTS:Even though significant doses of radiation were delivered to all regions of the spinal cord and nerve roots coincidentally involved in the treatments, only one patient in this series developed progressive symptoms possibly attributable to a toxic effect of the radiosurgery. Of those patients initially presenting with neurological deficits, 92% either remained neurologically stable or improved.CONCLUSION:Our observations suggest that radiosurgery as prescribed in this series of postoperative patients with residual spinal tumor is well-tolerated and associated with little to no significant morbidity.
Surgical Strategies for Recurrent Craniofacial Meningiomas
Authors: Rao Ganesh , Klimo Paul , Jensen Randy L. , MacDonald Joel D. , Couldwell William T. 
Published: April 2006

AbstractOBJECTIVE:Recurrent cranial base meningiomas are among the most difficult tumors to treat surgically. Although they are histologically benign, these tumors often invade through the cranial base into the infratemporal and pterygopalatine fossae. We reviewed our experience with these tumors to describe the natural history of these lesions as well as provide a possible treatment paradigm.METHODS:Between 2000 and 2004, seven patients with meningiomas recurring through the cranial base into facial structures were treated at the University of Utah. Five patients were treated with transcranial approaches only, and two were treated with a combination of transcranial and transfacial approaches.RESULTS:The average age of our patients (6 women, 1 man) was 55 years. The original site of tumor was the sphenoid wing in four patients, the middle fossa in two patients, and the left frontal region in one patient. The average interval between the most recent tumor resection and recurrence into the face was 9.9 years. The mean number of resections a patient underwent before invasion into the face was two. All but one patient had adjunctive therapy (including either radiation or chemotherapy) before recurrence into the face.CONCLUSION:Meningiomas that recur into facial structures present a unique treatment challenge. These lesions have a high rate of recurrence once they have invaded through the cranial base. Although combined approaches may be necessary to achieve a gross total resection, these lesions can often be reached using standard transcranial techniques.
Removal of An Orbital Metallic Foreign Body to Facilitate Magnetic Resonance Imaging: Technical Case Report
Authors: Deen H Gordon , Miller David A. , Kostick David A. , Jaeckle Kurt A. 
Published: April 2006

Abstract

OBJECTIVE AND IMPORTANCE:
Magnetic resonance imaging (MRI) is the imaging modality of choice for brain tumors and other lesions of the central nervous system. However, this procedure is contraindicated in patients with orbital metallic foreign bodies. In such cases, the usual clinical strategy is to manage the patient without the benefit of MRI scans and, instead, to rely on less sensitive imaging modalities in particular computed tomographic scanning.

CLINICAL PRESENTATION:
Two patients, one with a posterior fossa mass and one with suspected central nervous system lymphoma, were seen at our institution. MRI scanning was recommended, but had been precluded in both patients by the presence of metal fragments in the orbit.

INTERVENTION:
In each case, the orbital foreign body was successfully localized and removed. Postprocedure computed tomographic scanning confirmed complete removal. MRI scanning was then performed without difficulty. The first patient underwent posterior fossa craniotomy and removal of the tumor, which proved to be a medulloblastoma. The second patient was found to have evidence of lymphoma in the cranial base and meninges and was treated with radiotherapy and systemic and intrathecal chemotherapy. MRI scanning provided superior diagnostic information and spared both patients the risks and discomfort of myelography and exposure to ionizing radiation from multiple computerized tomographic scans.

CONCLUSION:
Two patients with central nervous system tumors underwent removal of a metal fragment in the orbit for the specific purpose of facilitating MRI scans. This is a practical, straightforward concept, which should be considered when MRI scanning is needed for optimal patient management.
Hydroformylation of Monosubstituted Alkenes Catalyzed by W–Rh Bimetallic Complex
Authors: Yamane Motoki , Yukimura Noriaki , Ishiai Hiroshi , Narasaka Koichi 
Published: April 2006

Abstract
By using a heterobimetallic catalyst, (CO)4(PEtPh2)W(μ-PPh2)Rh(CO)(PPh3), chemoselective hydroformylation of monosubstituted alkenes proceeds efficiently at room temperature under atmospheric pressure of CO/H2, without affecting functional groups such as disubstituted alkene moieties, aryl and alkenyl iodide moieties, and hydroxy and carboxy groups.
Assessing the Effects of Human Mixing Patterns on Human Immunodeficiency Virus-1 Interhost Phylogenetics Through Social Network Simulation
Authors: Goodreau Steven M 
Published: April 2006

AbstractGeneticists seeking to understand HIV-1 evolution among human hosts generally assume that hosts represent a panmictic population. Social science research demonstrates that the network patterns over which HIV-1 spreads are highly nonrandom, but the effect of these patterns on the genetic diversity of HIV-1 and other sexually transmitted pathogens has yet to be thoroughly examined. In addition, interhost phylogenetic models rarely account explicitly for genetic diversity arising from intrahost dynamics. This study outlines a graph-theoretic framework (exponential random graph modeling, ERGM) for the estimation, inference, and simulation of dynamic partnership networks. This approach is used to simulate HIV-1 transmission and evolution under eight mixing patterns resembling those observed in empirical human populations, while simultaneously incorporating intrahost viral diversity. Models of parametric growth fit panmictic populations well, yielding estimates of total viral effective population on the order of the product of infected host size and intrahost effective viral population size. Populations exhibiting patterns of nonrandom mixing differ more widely in estimates of effective population size they yield, however, and reconstructions of population dynamics can exhibit severe errors if panmixis is assumed. I discuss implications for HIV-1 phylogenetics and the potential for ERGM to provide a general framework for addressing these issues.
A single server tandem queue
Authors: Nair Sreekantan S. 
Published: April 2006

Avi-Itzhak, Maxwell and Miller (1965) studied a queueing model with a single server serving two service units with alternating priority. Their model explored the possibility of having the alternating priority model treated in this paper with a single server serving alternately between two service units in tandem.Here we study the distribution of busy period, virtual waiting time and queue length and their limiting behavior.
A process with chain dependent growth rate
Authors: Keilson Julian , Rao S. Subba 
Published: April 2006

Additive processes on finite Markov chains have been investigated by Miller ([8], [9]), Keilson and Wishart ([2], [3], [4]) and by Fukushima and Hitsuda [1]. These papers study a two-dimensional Markov Process {X(t), R(t)} whose state space is R1 × {1, 2, ···, R} characterized by the following properties:
(i)R(t) is an irreducible Markov chain on states 1,2, …,R governed by atransition probability matrix Bo = {brs}.(ii)X(t) is a sum of random increments dependent on the chain, i.e., if the ith transition takes the chain from state r to state s, then the increment has the distribution (iii)Nt, is t in discrete time while in the continuous time case Nt, might be an independent Poisson process.
A stochastic model for the formation of a planetary system
Authors: Galley S. J. 
Published: April 2006

SummaryThe stochastic model consists of a two-dimensional random walk with unit steps, each step being a Bernoulli trial. Two sets of possible conditions arising from astronomical theory give rise to two different barriers in the plane of the walk which cause a return to the origin. Another barrier indicates the formation of a planet and also causes a return to the origin. Consideration of the composition of the planets formed at this barrier allows their orbital distances and direction of rotation to be calculated. The predictions of one of the two models were found to be in close agreement with the observed planetary distances and masses in the solar system.
Moments in Markovian systems with lumped states
Authors: Taylor G. C. 
Published: April 2006

In dealing with Markov chains, we are sometimes forced by circumstances to make observations on lumped states. We may wish, however, to deal with a random variable which is a function of the numbers in the various (unlumped) states at various times and whose moments, therefore, will involve the probabilities of transition between the unlumped states.This paper demonstrates that, although these probabilities are immeasurable directly, we can, provided that we restrict our attention to a certain well-defined class of functions as our random variables, reduce all moments and product-moments of such random variables to functions of lumped state probabilities.
Waitingtimes between record observations
Authors: Neuts Marcel F. 
Published: April 2006

If Δrdenotes the waitingtime between the (r− 1)st and therth upper record in a sequence of independent, identically distributed random variables with a continuous distribution, then it is shown that Δrsatisfies the weak law of large numbers and a central limit theorem.This theorem supplements those of Foster and Stuart and Rényi, who investigated the indexVrof therth upper record.Qualitatively the theorems establish the intuitive fact that for higher records, the waitingtime between the last two records outweighs even the total waitingtime for previous records. This explains also why the asymptotic normality of logVris very inadequate for approximation purposes—Barton and Mallows.
Asymptotic probabilities in a critical age-dependent branching process
Authors: Weiner Howard J. 
Published: April 2006

Let Z(t) denote the number of cells alive at time t in a critical Bellman-Harris age-dependent branching process, that is, where the mean number of offspring per parent is one. A comparison method is used to show for k ≧ 1, and a high-order moment condition on G(t), where G(t) is the cell lifetime distribution, that lim t→∞t2P[Z(t) = k] = ak > 0, where {ak} are constants.The method is also applied to the total progeny in the critical process.
More bounds on the expectation of a convex function of a random variable
Authors: A. Ben-Tal , Hochman E. 
Published: April 2006

Jensen gave a lower bound to Eρ(T), where ρ is a convex function of the random vector T. Madansky has obtained an upper bound via the theory of moment spaces of multivariate distributions. In particular, Madansky's upper bound is given explicitly when the components of T are independent random variables. For this case, lower and upper bounds are obtained in the paper, which uses additional information on T rather than its mean (mainly its expected absolute deviation about the mean) and hence gets closer to Eρ(T).The importance of having improved bounds is illustrated through a nonlinear programming problem with stochastic objective function, known as the “wait and see” problem.
Correlation structure of teletraffic measurements from randomly-scanned calls arrival data
Authors: Lee P. A. 
Published: April 2006

In teletraffic measurements, a call arrival process is commonly studied using a method with time-uniform or periodic scanning. The information recorded is the number of calls arrived between the scannings, from which data the number of scans between two successive calls is obtained. These later numbers are used as a measure of the interarrival times.For an exponential call arrival process, except in the case of Poisson scanning, all other scanning schemes yield the number of scans which are not independent in any two interarrival intervals. By treating the problem as an interaction of two stationary stochastic point processes, we determine the exact joint probability distribution of the number of scans in two adjacent and non-adjacent interarrival intervals. An explicit expression for the correlation coefficient is also obtained.
The probabilistic significance of the rate matrix in matrix-geometric invariant vectors
Authors: Neuts Marcel F. 
Published: April 2006

Many queueing models have embedded Markov chains, whose invariant probability vector is of a (modified) matrix-geometric form. The rate matrixRis shown to have the following probabilistic interpretation:The elementRvjis the expected number of visits to the state (i+ 1,j), before the first return to the seti= {(i, 1), …,(i, m)}, in a chain starting in the state (i,v).
Convergence to equilibrium in a traffic model with restricted passing
Authors: Unkelbach Hans Dieter 
Published: April 2006

A road traffic model with restricted passing, formulated by Newell (1966), is described by conditional cluster point processes and analytically handled by generating functionals of point processes.The traffic distributions in either space or time are in equilibrium, if the fast cars form a Poisson process with constant intensity combined with Poisson-distributed queues behind the slow cars (Brill (1971)). It is shown that this state of equilibrium is stable, which means that this state will be reached asymptotically for general initial traffic distributions. Furthermore the queues behind the slow cars dissolve asymptotically like independent Poisson processes with diminishing rate, also independent of the process of non-queuing cars. To get these results limit theorems for conditional cluster point processes are formulated.
Inference for general Ising models
Authors: Pickard David K. 
Published: April 2006

In previous papers (1976), (1977a), (1979) limit theorems were obtained for the classical Ising model, and these provided the basis for asymptotic inference. The present paper extends these results to more general Ising models.In two and more dimensions, likelihood inference for the thermodynamic parameters (i.e. the interaction energies) is effectively impossible. The problem is that the error in locating critical and/or confidence regions is as large as their diameters. To remedy this requires more accurate characterizations of the partition functions, but these seem unlikely to be forthcoming. Besag's coding estimators for these parameters are inverse hyperbolic tangents of the roots of simultaneous polynomial equations and hence avoid such location errors. However, little is yet known about their sampling characteristics. Finally, likelihood inference for lattice averages (an alternative parametrization) is straightforward from the limit theorems.
A service model in which the server is required to search for customers
Authors: Neuts Marcel F. , Ramalhoto M. F. 
Published: April 2006

Customers enter a pool according to a Poisson process and wait there to be found and processed by a single server. The service times of successive items are independent and have a common general distribution. Successive services are separated by seek phases during which the server searches for the next customer. The search process is Markovian and the probability of locating a customer in (t, t + dt) is proportional to the number of customers in the pool at time t. Various stationary probability distributions for this model are obtained in explicit forms well-suited for numerical computation.Under the assumption of exponential service times, corresponding results are obtained for the case where customers may escape from the pool.
The limiting properties of population distributions with particular application to manpower planning
Authors: Woodward Mark 
Published: April 2006

A model for predicting expected-value population distributions is developed, assuming that all movements are Markovian and time-homogeneous. Each individual is classified by the amount of time he has spent in the population and by which of a number of classes, of an unspecified nature, he inhabits. The limiting properties of the population distribution are derived, and, in particular, conditions for convergence to a stable distribution are given.Some discussion of the relevance of the theory to practical applications is given, primarily to manpower planning when recruitment occurs purely to maintain a specified overall population size.
Job search: the continuous case
Authors: Zuckerman Dror 
Published: April 2006

In this paper we examine a continuous model of job search. An individual is seeking employment continuously over time. There is a search cost of c monetary units per unit time. Job offers are received randomly over time according to a renewal process. The wage offers are assumed to be positive, independent and identically distributed random variables. The only decision the searcher must make is when to stop searching and accept an offer. The objective is to determine a stopping rule that is optimal under the following optimality criteria:
(a)maximum expected net return,(b)maximum expected discounted net return.We investigate the case in which the stream of job offers is determined by a Poisson process. We show that under the two optimality criteria defined above an optimal stopping rule is determined by a single critical value ξ. The optimal strategy is to accept the first job offer that exceeds ξ. In the second part of the article, the search model in which offers are received according to a general renewal process is examined.
The exact and asymptotic formulas for the state probabilities in simple epidemics with m kinds of susceptibles
Authors: Lacayo H. , Langberg Naftali A. 
Published: April 2006

A population of susceptible individuals partitioned into m groups and exposed to a contagious disease is considered.The progress of this simple epidemic is modeled by an m -dimensional stochastic process, whose components are the number of infective individuals in the respective groups at time t. Exact and approximate formulas for the joint and marginal state probabilities are obtained.
Stochastic models and field trials
Authors: Bartlett M. S. 
Published: April 2006

A survey of the development of statistical techniques of field experimentation refers to the unified approach of R. A. Fisher, in which analysis and design were closely linked. Randomization of treatment positions bypassed the need for a precise stochastic model, but sometimes at the cost of diminished accuracy.Alternative covariance methods associated with the name of J. S. Papadakis, taking note of the yields of neighbouring plots, have stimulated much research in recent years. The results to date suggest that, while improved accuracy can often be achieved, the assessment of accuracy is more dependent on the stochastic model. Robust methods for such assessment still need to be finalized; with these alternative methods a closer link between analysis and design is also advocated.
Smooth first-passage densities for one-dimensional diffusions
Authors: Pauwels E. J. 
Published: April 2006

The purpose of this paper is to show that smoothness conditions on the diffusion and drift coefficient of a one-dimensional stochastic differential equation imply the existence and smoothness of a first-passage density.In order to be able to prove this, we shall show that Brownian motion conditioned to first hit a point at a specified time has the same distribution as a Bessel (3)-process with changed time scale.
Point-process models with linearly parametrized intensity for application to earthquake data
Authors: Ogata Yosihiko , Katsura Koichi 
Published: April 2006

It is demonstrated that linear parametrization of the conditional intensity provides systematic classes of flexible models which are reasonably useful for calculating maximum likelihoods. To exemplify the modelling, seismic activity around Canberra is decomposed into components of evolutionary trend, clustering and periodicity. The causal relationship between earthquake sequences from two seismic regions is also analysed for a certain Japanese earthquake data set.Some technical aspects of the modelling and calculations are described.