bluuebunny/crossref_metadata_2025_split huggingface dataset:
YULE‐WALKER ESTIMATES FOR CONTINUOUS‐TIME AUTOREGRESSIVE MODELS
Authors: Hyndman Rob J. 
Published: May 2008

Abstract.I consider continuous‐time autoregressive processes of orderpand develop estimators of the model parameters based on Yule‐Walker type equations. For continuously recorded data, it is shown that these estimators are least squares estimators and have the same asymptotic distribution as maximum likelihood estimators.In practice, though, data can only be observed discretely. For discrete data, I consider approximations to the continuous‐time estimators. It is shown that some of these discrete‐time estimators are asymptotically biased. Alternative estimators based on the autocovariance function are suggested. These are asymptotically unbiased and are a fast alternative to the maximum likelihood estimators described by Jones. They may also be used as starting values for maximum likelihood estimation.
AN OUTLIER TEST FOR TIME SERIES BASED ON A TWO‐SIDED PREDICTOR
Authors: Schmid W. 
Published: May 2008

Abstract.In this paper an outlier test for contaminated autoregressive processes is introduced. The test is based on a comparison of each observation with a predictor using past and future values, a so‐called two‐sided predictor. It is required that an upper bound for the total number of outliers is known.The asymptotic distribution of the test statistic is calculated under the null hypothesis that no outlier is present. The behaviour of the test for finite sample size is investigated by a simulation study. Moreover, the test is compared with several other outlier tests.
SPECTRAL DENSITY ESTIMATION VIA NONLINEAR WAVELET METHODS FOR STATIONARY NON‐GAUSSIAN TIME SERIES
Authors: Neumann Michael H. 
Published: May 2008

Abstract.In the present paper we consider nonlinear wavelet estimators of the spectral densityfof a zero mean, not necessarily Gaussian, stochastic process, which is stationary in the wide sense. It is known in the case of Gaussian regression that these estimators outperform traditional linear methods if the degree of smoothness of the regression function varies considerably over the interval of interest. Such methods are based on a nonlinear treatment of empirical coefficients that arise from an orthonormal series expansion according to a wavelet basis.The main goal of this paper is to transfer these methods to spectral density estimation. This is done by showing the asymptotic normality of certain empirical coefficients based on the tapered periodogram. Using these results we can show the risk equivalence to the Gaussian case for monotone estimators based on such empirical coefficients. The resulting estimator offkeeps all interesting properties such as high spatial adaptivity that are already known for wavelet estimators in the case of Gaussian regression.It turns out that appropriately tuned versions of this estimator attain the optimal uniform rate of convergence of theirL2risk in a wide variety of Besov smoothness classes, including classes where linear estimators (kernel, spline) are not able to attain this rate. Some simulations indicate the usefulness of the new method in cases of high spatial inhomogeneity.
Androgen and gonadotropin patterns differ in HIV‐1‐infected men who develop lipoatrophy during antiretroviral therapy: a case–control study
Authors: Wunder DM , Fux CA , Bersinger NA , Mueller NJ , Hirschel B , Cavassini M , Elzi L , Schmid P , Bernasconi E , Mueller B , Furrer H ,   the Swiss HIV Cohort Study
Published: May 2008

ObjectivesWe compared androgen and gonadotropin values in HIV‐infected men who did and did not develop lipoatrophy on combination antiretroviral therapy (cART).MethodsFrom a population of 136 treatment‐naïve male Caucasians under successful zidovudine/lamivudine‐based cART, the 10 patients developing lipoatrophy (cases) were compared with 87 randomly chosen controls. Plasma levels of free testosterone (fT), dehydroepiandrosterone (DHEA), follicle‐stimulating hormone and luteinizing hormone (LH) were measured at baseline and after 2 years of cART.ResultsAt baseline, 60% of the cases and 71% of the controls showed abnormally low fT values. LH levels were normal or low in 67 and 94% of the patients, respectively, indicating a disturbance of the hypothalamic–pituitary–gonadal axis. fT levels did not significantly change after 2 years of cART. Cases showed a significant increase in LH levels, while controls showed a significant increase in DHEA levels. In a multivariate logistic regression model, lipoatrophy was associated with higher baseline DHEA levels (P=0.04), an increase in LH levels during cART (P=0.001), a lower body mass index and greater age.ConclusionsHypogonadism is present in the majority of HIV‐infected patients. The development of cART‐related lipoatrophy is associated with an increase in LH and a lack of increase in DHEA levels.
Modelling University Governance
Authors: Trakman Leon 
Published: May 2008

AbstractTwentieth century governance models used in public universities are subject to increasing doubt across the English‐speaking world. Governments question if public universities are being efficiently governed; if their boards of trustees are adequately fulfilling their trust obligations towards multiple stakeholders; and if collegial models of governance are working in increasingly complex educational environments. With declining public funding for tertiary education, growing international competition among institutions of higher learning in our information age and worrisome evidence of dysfunctional governance, critics question if established governance structures are able to meet these and other challenges. Some insist that members of faculty are most suited to govern public universities because they appreciate the vision and mission of the university. Others demand that boards of governors be skilled in financial matters and drawn primarily from corporate life. Yet others call for governance based on trust and confidence between those who govern and those who are governed. The article evaluates competing trends in models of university governance in the United Kingdom, the British Commonwealth and the United States. Arguing against a one‐size‐fits‐all model, it sets out specific factors to consider in reforming governance models to meet the demands of our times.
Meanings and Experiences of Menstruation: Perceptions of Institutionalized Women with an Intellectual Disability
Authors: Chou Yueh‐Ching , Lu Zxy‐Yann Jane , Wang Frank T. Y. , Lan Chang‐Fu , Lin Li‐Chan 
Published: May 2008

Background:  No studies have ever been conducted concerning menstrual experiences among women with an intellectual disability in Taiwan.Materials and Methods:  An in‐depth interview was conducted at three public institutions and perceptions and experiences regarding menstruation were elicited from 55 women aged 21–65 years.Results:  The participants knew about menstrual blood and could recognize the experiences of period pain and its link to femininity. The women’s management of menstruation played a big part in their institutionalized life, where they had relatively limited choice and autonomy. Positive feelings towards the menstrual cycle were experienced by some participants; however, many had negative attitudes towards sexual activities or parenting, even though they knew the association between menstruation and pregnancy.Conclusions:  Although these women’s experiences of perimenstrual symptoms are quite similar to those of women without intellectual disability, their menstrual management, interpretations and attitudes to menses are influenced by their institutional life and by the society at large.
Temperature perception and signal transduction in plants
Authors: Penfield Steven 
Published: May 2008

SummaryPlants can show remarkable responses to small changes in temperature, yet one of the great unknowns in plant science is how that temperature signal is perceived. The identity of the early components of the temperature signal transduction pathway also remains a mystery. To understand the consequences of anthropogenic environmental change we will have to learn much more about the basic biology of how plants sense temperature. Recent advances show that many known plant‐temperature responses share common signalling components, and suggest ways in which these might be linked to form a plant temperature signalling network.

Contents

Summary
615

I.
Introduction
616

II.
Plant acclimatization to cold
616

III.
The acquisition of thermotolerance
617

IV.
Abscisic acid and extreme temperature responses
617

V.
Altering plant fatty acid composition affects plant tolerance to temperature extremes
617

VI.
Temperature regulates the protein stability of fatty acid desaturases
618

VII.
Membrane fluidity and temperature sensing
618

VIII.
The role of gibberellin in temperature‐regulated growth
619

IX.
Temperature‐regulated GA synthesis controls seed germination
619

X.
Temperature regulates auxin levels to control plant growth rhythms
620

XI.
The circadian clock: temperature entrainment and compensation
620

XII.
Temperature regulates flowering time independently of GA synthesis
621

XIII.
Temperature‐responsive periods control annual growth in trees
621

XIV.
Temperature response pathways share common signalling components
622

XV.
Flowering time regulators with roles in cold acclimatization
623

XVI.
A general role for the circadian clock in temperature signal transduction
623

XVII.
Cytosolic calcium may integrate temperature and circadian signalling
624

XVIII.
The role of phytochrome signalling in temperature responses
624

XIX.
Conclusions
625

References
625
Cell cycle‐driven neuronal apoptosis specifically linked to amyloid peptide Aβ1–42 exposure is not exacerbated in a mouse model of presenilin‐1 familial Alzheimer’s disease
Authors: Malik Bilal , Currais Antonio , Soriano Salvador 
Published: May 2008

AbstractWe have shown previously that β‐catenin and cyclin D1 are up‐regulated in cortical neurons from homozygous mice carrying the familial Alzheimer’s disease (FAD) presenilin‐1 M146V mutation in a knock‐in model (PS1 KIM146V mice), leading to cell cycle‐associated apoptosis. Here, we have aimed to determine (i) whether this phenotype is present in heterozygous PS1 KIM146V mice, which reflects more accurately the PS1 FAD condition in humans and (ii) whether Aβ1–42, which is invariably present in the PS1 FAD brain and is thought to affect neuronal cell cycle kinetics, may contribute to the abnormal cell cycle/cell death phenotype seen in PS1 KIM146V mice. We demonstrate that cell cycle‐linked apoptosis occurs in heterozygous PS1 KIM146V post‐mitotic neurons. In addition, there is a significant Aβ‐associated increase in cell cycle and cell death that is not further modified by the PS1 KIM146V mutation. Our results are consistent with a cell cycle‐associated neurodegeneration model in the PS1 FAD brain in which the loss of PS1‐dependent β‐catenin regulatory function is sufficient to commit susceptible neurons to an abortive cell cycle, and may act synergistically with the Aβ cytotoxic challenge present in the PS1 FAD brain to expand the neuronal population susceptible to cell cycle‐driven apoptosis.
Regulation of neural progenitor cell motility by ceramide and potential implications for mouse brain development
Authors: Wang Guanghu , Krishnamurthy Kannan , Chiang Ying‐Wei , Dasgupta Somsankar , Bieberich Erhard 
Published: May 2008

AbstractWe provide evidence that the sphingolipid ceramide, in addition to its pro‐apoptotic function, regulates neural progenitor (NP) motility in vitro and brain development in vivo. Ceramide (N‐palmitoyl d‐erythro sphingosine and N‐oleoyl d‐erythro sphingosine) and the ceramide analog N‐oleoyl serinol (S18) stimulate migration of NPs in scratch (wounding) migration assays. Sphingolipid depletion by inhibition of de novo ceramide biosynthesis, or ceramide inactivation using an anti‐ceramide antibody, obliterates NP motility, which is restored by ceramide or S18. These results suggest that ceramide is crucial for NP motility. Wounding of the NP monolayer activates neutral sphingomyelinase indicating that ceramide is generated from sphingomyelin. In membrane processes, ceramide is co‐distributed with its binding partner atypical protein kinase C ζ/λ (aPKC), and Cdc42, α/β‐tubulin, and β‐catenin, three proteins involved in aPKC‐dependent regulation of cell polarity and motility. Sphingolipid depletion by myriocin prevents membrane translocation of aPKC and Cdc42, which is restored by ceramide or S18. These results suggest that ceramide‐mediated membrane association of aPKC/Cdc42 is important for NP motility. In vivo, sphingolipid depletion leads to ectopic localization of mitotic or post‐mitotic neural cells in the embryonic brain, while S18 restores the normal brain organization. In summary, our study provides novel evidence that ceramide is critical for NP motility and polarity in vitro and in vivo.
Extracellular levels of brain aspartate, glutamate and GABA during an inhibitory avoidance response in the rat
Authors: Ballini Chiara , Corte Laura Della , Pazzagli Marta , Colivicchi Maria Alessandra , Pepeu Giancarlo , Tipton Keith F. , Giovannini Maria Grazia 
Published: May 2008

AbstractThe extracellular levels of aspartate, glutamate and GABA were measured by microdialysis, coupled with an HPLC method, in rat prefrontal cortex (mPFC) and ventral hippocampus (VH) before and during the performance of a step‐down inhibitory task. The basal levels of glutamate were about 50% higher than those of aspartate, and GABA levels were about 20‐folds smaller than those of the excitatory amino acids. There were no significant differences in the basal levels of any of the three amino acids between the two brain regions. The extracellular levels of aspartate increased during acquisition and recall trials in both VH and mPFC, whereas those of glutamate increased in the VH during acquisition only. A significant increase in GABA levels was also detected during acquisition but only in the mPFC. The neuronal origin of the increased extracellular levels of aspartate, glutamate and GABA was demonstrated by administering tetrodotoxin directly into the mPFC or VH by reverse dialysis. These findings, together with previous evidence from our and other laboratories, indicate a differential release of aspartate and glutamate from excitatory neurons during the performance of behavioral responses, and therefore, distinct roles for the two excitatory amino acids should be envisaged.
Markers of cellular senescence in zero hour biopsies predict outcome in renal transplantation
Authors: Koppelstaetter Christian , Schratzberger Gabriele , Perco Paul , Hofer Johannes , Mark Walter , Öllinger Robert , Oberbauer Rainer , Schwarz Christoph , Mitterbauer Christa , Kainz Alexander , Karkoszka Henryk , Wiecek Andrzej , Mayer Bernd , Mayer Gert 
Published: May 2008

SummaryAlthough chronological donor age is the most potent predictor of long‐term outcome after renal transplantation, it does not incorporate individual differences of the aging‐process itself. We therefore hypothesized that an estimate of biological organ age as derived from markers of cellular senescence in zero hour biopsies would be of higher predictive value. Telomere length and mRNA expression levels of the cell cycle inhibitors CDKN2A (p16INK4a) and CDKN1A (p21WAF1) were assessed in pre‐implantation biopsies of 54 patients and the association of these and various other clinical parameters with serum creatinine after 1 year was determined. In a linear regression analysis, CDKN2A turned out to be the best single predictor followed by donor age and telomere length. A multiple linear regression analysis revealed that the combination of CDKN2A values and donor age yielded even higher predictive values for serum creatinine 1 year after transplantation. We conclude that the molecular aging marker CDKN2A in combination with chronological donor age predict renal allograft function after 1 year significantly better than chronological donor age alone.
Experimental Health Insurance Estimates for Low‐Income and Demographic Groups by State
Authors: O'Hara Brett 
Published: May 2008

Objective. To assess the quality of new modeled estimates of health insurance based on a federal survey.Data Sources/Study Setting. The study uses data from the Annual Social and Economic Supplements to the Current Population Survey (CPS ASEC), calendar years 2001–2003. Health insurance estimates for low‐income populations are analyzed.Study Design. To assess a method for making estimates for uninsured low‐income persons, survey estimates of low‐income children are compared with modeled estimates. Inferences can be drawn from this comparison and the method is extended to account for demographic groups.Data Collection. Data for 2001–2002 CPS ASEC were self‐tabulated for low‐income children aged 0–17. A special tabulation of the CPS ASEC was used to categorize the numbers of uninsured by age, race, sex, and Hispanic origin by low income at the state level. This special tabulation was the underlying data for the model.Principal Findings. The modeled estimates reduce the variance and margin of error substantially compared with the survey estimates.Conclusions. These health insurance estimates are credible and increase the precision for the low‐income uninsured population. They have broad uses for policy makers and program administrators who focus on the uninsured in special populations.
Feasibility of routine individual donation testing for West Nile virus RNA during epidemic season using the investigational Roche cobas TaqScreen West Nile virus test and cobas s 201 system prototype
Authors: Galel Susan A. , Webster Jan , Roa Lurimer 
Published: May 2008

BACKGROUND: Minipool (MP) screening for West Nile virus (WNV) RNA may fail to detect presumptive viremic donations (PVDs) detectable by individual donation screening (IDS). Most blood centers switch collection regions to IDS when PVD detection by MP screening reaches a certain frequency. Use of IDS for all donations during WNV season was assessed during a clinical trial of the Roche cobas TaqScreen WNV test. Also evaluated was whether PVD detection reliably identifies regions that should be targeted for IDS.STUDY DESIGN AND METHODS: Test results, deviation reports, and service records were reviewed for 13.5 weeks of IDS in 2006 and 11.5 weeks of IDS in 2007. Numbers of PVDs and clinical WNV cases were obtained from public health and AABB Web sites and regional donor centers.RESULTS: Approximately 1000 donations were tested per week divided in six test runs. Each run required 1.2 shifts of technologists plus volunteers. A total of 7.2 percent of samples were initially unreportable in 2006 and 4.8 percent in 2007. Of 26,952 donations screened by IDS, none were reactive for WNV. A comparison of PVD and clinical case reports indicates that PVD detection in areas with intermediate or high clinical case prevalence may not reach commonly used criteria for triggering testing to IDS.CONCLUSION: Seasonal IDS was feasible using the cobas TaqScreen WNV test on the s 201, although staffing was impacted and a relatively high number of samples required retesting because of error messages. Seasonal IDS utilizing this highly specific assay may be a reasonable alternative to IDS triggered by regional PVD detection.
Detection of bacteria in stored red cell products using a culture‐based bacterial detection system
Authors: Chen Cyndi L. , Yu Jing‐Chen , Holme Stein , Jacobs Michael R. , Yomtovian Roslyn , McDonald Carl P. 
Published: May 2008

BACKGROUND: The Pall eBDS uses oxygen consumption as a surrogate marker for bacterial detection in platelet (PLT) products. This article describes the evaluation of eBDS to detect bacterial contamination in inoculated fresh and stored leukoreduced red cell (RBC) units.STUDY DESIGN AND METHODS: Field studies were conducted at three sites to establish eBDS pouch incubation time and the pass/fail threshold. RBC units were inoculated with each of 12 bacterial species known to cause sepsis at target inocula of either 1 to 15 or 100 colony‐forming units (CFUs) per mL. Units were mixed and stored at 2 to 6°C. Samples were taken for culture and eBDS testing weekly from 0 hour to 42 days and incubated for 35°C for 24 to 30, 48, and 72 hours, followed by measurement of percent oxygen content.RESULTS: The studies showed growth of five bacterial species (including Yersinia enterocolitica) in RBC units, while seven bacterial species showed no growth or autosterilized. A pass/fail oxygen threshold of 14.4 percent was determined based on results from noninoculated controls (n = 633) and from inoculated samples (n = 884) after 48 hours of incubation. Detection was 100 percent at all sampling times during refrigerated storage with both 48 and 72 hours of pouch incubation.CONCLUSION: With incubation of eBDS pouches for 48 and 72 hours, 100 percent detection was obtained in 884 samples with bacterial levels of at least 1 CFU per mL, and no false‐positive samples were obtained. Based on the bacterial growth patterns, RBC units may be sampled 1 to 3 days after collection for optimal efficacy and read after 48 to 72 hours of incubation of the eBDS sample pouches at 35°C. The Pall eBDS is suited for detection of typical bacterial contaminants in fresh and stored RBCs.
Recovery of hemoglobin mass after blood donation
Authors: Pottgiesser Torben , Specker Wolfgang , Umhau Markus , Dickhuth Hans‐Hermann , Roecker Kai , Schumacher Yorck O. 
Published: May 2008

BACKGROUND: Blood donation plays an important role in every health care system. Measurement of hemoglobin (Hb) concentration or hematocrit to assess hematologic recovery after donation may not adequately reflect the true amount of blood as they are affected by plasma volume fluctuations. Instead, total Hb mass (tHb) is the variable of choice and can be determined in routine clinical practice. Therefore, the purpose was to investigate the recovery of tHb after standard blood donation.STUDY DESIGN AND METHODS: The optimized CO rebreathing method was used for evaluation of tHb before and after 1‐unit (erythrocyte concentrate) standard blood donation in 29 male volunteers (30 ± 10 years, 181 ± 7 cm, 76.6 ± 11.2 kg). Subsequently, tHb measurements were performed in regular intervals until one of two termination criteria was met.RESULTS: After donation of approximately 550 mL of whole blood, the lost amount of tHb of 75 ± 15 g (8.8 ± 1.9%) was recovered after a mean of 36 ± 11 days (range, 20‐59 days).CONCLUSIONS: The results of this study confirm the minimal, recommended donation intervals (56 days for men) as adequate when, for the first time, judged upon by tHb as a direct marker of hematologic recovery.
CAPM and Option Pricing With Elliptically Contoured Distributions
Authors: Hamada Mahmoud , Valdez Emiliano A. 
Published: May 2008

AbstractThis article offers an alternative proof of the capital asset pricing model (CAPM) when asset returns follow a multivariate elliptical distribution. Empirical studies continue to demonstrate the inappropriateness of the normality assumption for modeling asset returns. The class of elliptically contoured distributions, which includes the more familiar Normal distribution, provides flexibility in modeling the thickness of tails associated with the possibility that asset returns take extreme values with nonnegligible probabilities. As summarized in this article, this class preserves several properties of the Normal distribution. Within this framework, we prove a new version of Stein's lemma for this class of distributions and use this result to derive the CAPM when returns are elliptical. Furthermore, using the probability distortion function approach based on the dual utility theory of choice under uncertainty, we also derive an explicit form solution to call option prices when the underlying is log‐elliptically distributed. The Black–Scholes call option price is a special case of this general result when the underlying is log‐normally distributed.