bluuebunny/crossref_metadata_2025 huggingface dataset:
NONLINEAR TRANSFORMATIONS OF INTEGRATED TIME SERIES:A RECONSIDERATION
Authors: Corradi Valentina
Published: May 2008

Abstract. In this paper I reconsider two of the questions raised by Granger and Hallman (Nonlinear transformations of integrated time series. J. Time Ser. Anal. 12 (1991), 207–24):(i) If Xt is I(1) and Zt=h(Xt), is Zt also I(1)? (ii) Can Xt and h(Xt) be cointegrated? The distinction between I(1) and I(0) processes is replaced by the distinction between long memory and short memory processes, where for short memory I mean strong mixing. By exploiting the fact that random walks (with positive trend component) are martingales (submartingales) and are also first‐order Markov, I show that (a) unbounded convex (concave) and strictly monotonic transformations of random walks are always long memory processes, (b) polynomial, strictly convex (concave) transformations of random walks display a unit root component, but the first differences of such transformations need not be short memory, and (c) Xt and h(Xt), with h an unbounded convex (concave) or strictly monotonic function, can never be cointegrated.
THE RECURSIVE PROPERTY OF THE INVERSE OF THE COVARIANCE MATRIX OF A MOVING‐AVERAGE PROCESS OF GENERAL ORDER
Authors: Haddad John N.
Published: May 2008

Abstract. The inverse of the covariance matrix of a moving‐average process of general order is considered. A recursive relationship between the inverses for any two consecutive orders has been established. Illustrative situations are derived and exact expressions are discussed.
BANDWIDTH SELECTION IN KERNEL SMOOTHING OF TIME SERIES
Authors: Kim Tae Yoon , Cox Dennis D.
Published: May 2008

Abstract. The kernel smoothing method has been considered as a useful tool for identification and prediction in time series models. In practice this method is to be tuned by a smoothing parameter. For selection of the smoothing parameter, Härdle and Vieu (Kernel regression smoothing of time series. J. Time Ser. Anal. 13(1992), 209–32) considered a cross‐validation rule and proved its asymptotic optimality. In this paper we strengthen their result for a wider use of the kernel smoothing of time series.
A GENERALIZED FRACTIONALLY INTEGRATED AUTOREGRESSIVE MOVING‐AVERAGE PROCESS
Authors: Chung Ching‐Fan
Published: May 2008

Abstract. This paper considers the long memory Gegenbauer autoregressive movingaverage (GARMA) process that generalizes the fractionally integrated ARMA (ARFIMA) process to allow for hyperbolic and sinusoidal decay in autocorrelations. We propose the conditional sum of squares method for estimation (which is asymptotically equivalent to the maximum likelihood estimation) and develop the asymptotic theory. Many results are in sharp contrast to those of the ARFIMA model. Simulations are conducted to assess the performance of the proposed estimators in small sample applications. Two applications to the sunspot data and the US inflation rates based on the wholesale price index are provided.
RECURSIVE COMPUTATION OF THE PARAMETERS OF PERIODIC AUTOREGRESSIVE MOVING‐AVERAGE PROCESSES
Authors: Boshnakov Georgi N.
Published: May 2008

Abstract. An algorithm for recursive computation of the parameters of periodic autoregressive moving‐average (ARMA) processes is given. It also provides recursions for stationary multivariate ARMA processes. A procedure for simultaneous estimation of the order and the parameters of a periodic ARMA process is outlined.
ON LOW AND HIGH FREQUENCY ESTIMATION
Authors: Huang Dawei
Published: May 2008

Abstract. Estimating low or high frequencies is usually more difficult than estimating ordinary frequencies. In this paper, we show that the estimation accuracy depends on the combination of frequency, phase and sample size. For the best case, the mean square error can be smaller than the standard asymptotic Cramèr–Rao bound for an unbiased estimator in the Gaussian white noise case. Asymptotic theory for two limit procedures—the frequency changes as sample size increases or the frequency is fixed while the signal to noise ratio (SNR) increases—is established. Simulation shows that this theory is relevant for a wide range of situations which vary from small sample size (10) and high SNR (≥ 4) to large sample size (1000) and low SNR (≥ ‐16).
THIRD‐ORDER ASYMPTOTIC PROPERTIES OF ESTIMATORS IN GAUSSIAN ARMA PROCESSES WITH UNKNOWN MEAN
Authors: Kakizawa Yoshihide
Published: May 2008

Abstract.This paper deals with the third‐order asymptotic theory for Gaussian autoregressive moving‐average (ARMA) processes with unknown meanμ.We are interested in the estimation ofρ= (α1…, αp, β1…, βq), whereα1…,αρandβ1…,βqare the coefficients of the autoregressive part and the moving‐average part, respectively. First, we investigate the third‐order asymptotic optimality of the bias adjusted maximum likelihood estimator (MLE) ofρin the presence of the nuisance parameters μ and s̀2(innovation variance). Next, for a Gaussian AR(1μμ, s̀2), we propose a mean corrected estimator αc1c2of the autoregressive coefficient. We make a comparison between the bias adjusted estimator αc1c2* and the bias adjusted MLE, in terms of their probabilities of concentration around the true value, or equivalently, in terms of their mean squared errors. Finally some numerical studies are provided in order to verify the third‐order asymptotic theory.
RANDOM SAMPLING ESTIMATION FOR ALMOST PERIODICALLY CORRELATED PROCESSES
Authors: Dehay D. , Monsan V.
Published: May 2008

Abstract. In this paper we study the estimation of the spectral density functions of a continuous‐time parameter almost periodically correlated process from one discrete random‐time sampling. Under mixing hypotheses on the cumulant of the process, we establish the quadratic consistency of this estimator and the rate of convergence.
SPECTRAL MAXIMUM LIKELIHOOD ESTIMATION OF A SIGNAL‐TO‐NOISE RATIO LYING IN THE VICINITY OF ZERO
Authors: Fernández‐Macho F. Javier
Published: May 2008

Abstract. A time series model representing a decomposition into permanent plus transient components contains a deterministic component when the signal‐to‐noise ratio is equal to zero; otherwise, the permanent component is said to be stochastic. This distinction has important consequences in the analysis of economic phenomena. On the other hand, the absence of a stochastic permanent component in residuals from a time series regression may indicate cointegration. This paper considers the frequency domain estimation of the signal‐to‐noise ratio in a representative of the unobserved components model class. The sampling properties of the estimator from the resulting approximate spectral likelihood differ from those observed in the time domain and they vary substantially depending on whether the overall slope must be estimated or not. Further, it is shown that spectral estimates are T‐consistent—instead of T2‐consistent in the time domain. These results may explain some of the differences in estimators from frequency domain approximations to the likelihood and exact maximum likelihood estimators, and may be of use when testing for deterministic trends.
TESTING CHANGE‐POINTS IN THE EXPLOSIVE GAUSSIAN AUTOREGRESSIVE PROCESSES
Authors: Raimondo M.
Published: May 2008

Abstract. A functional limit theorem with a particular function class and topology is derived for non‐ergodic type time series. This limit theorem allows us to study the asymptotic law of the associated likelihood ratio test (LRT) statistic for testing the presence of a change in the covariance parameter in the explosive Gaussian autoregressive model. We show that the level of the LRT cannot be approximated without introducing appropriate normalization. The limit law of a particular weighted likelihood ratio test is examined through a simulation study and is compared with the well‐known Kolmogorov distribution obtained in the stationary case; we conclude that for practical applications when the root is really close to unity one can use the same thresholds as in the stationary case. This procedure is applied to the study of three real time series known to be non‐stationary.
TESTING THE ORDER OF DIFFERENCING IN TIME SERIES REGRESSION
Authors: Saikkonen Pentti , Luukkonen Ritva
Published: May 2008

Abstract.In this paper we develop a test procedure for detecting overdifferencing or a moving‐average unit root in time series regression models with Gaussian autoregressive moving‐average errors. In addition to an intercept term the regressors consist of stable or asymptotically stationary variables and non‐stationary trending variables generated by an integrated process of order 1. The test of the paper is based on the theory of locally best invariant unbiased tests. Its limiting distribution is derived under the null hypothesis and found to be non‐standard but free of unknown nuisance parameters. Asymptotic critical values, which depend on the number of integrated regressors, are obtained by simulation. A limited simulation study is carried out to illustrate the finite sample properties of the test.
ADEQUACY OF ASYMPTOTIC THEORY FOR GOODNESS‐OF‐FIT CRITERIA FOR SPECTRAL DISTRIBUTIONS
Authors: Anderson T. W. , You Linfeng
Published: May 2008

Abstract. Any of the Cramér‐von Mises, Anderson‐Darling, and Kolmogorov‐Smirnov statistics can be used to test the null hypothesis that the standardized spectral distribution of a stationary stochastic process is a specified one. The asymptotic distributions of the criteria have been characterized (Anderson, 1993). They are the same as for probability distributions if the observations are independent (all autocorrelations zero), but are different when there is dependence. In this paper simulation with 10000 replications has been used to determine the distributions of the criteria for samples of size 6, 10, 30 and 100 when the observations are independent. These empirical distributions have been compared with the asymptotic distributions in order to ascertain the sample sizes necessary for using the asymptotic tables. For practical purposes they are 30 for the Cramér‐von Mises and Kolmogorov statistics and over 100 for Anderson‐Darling.
Seniority Profiles in Unionized Workplaces: Do Unions Still have the Edge?*
Authors: Zangelidis Alexandros
Published: May 2008

The focus of this study is to distinguish the different paths seniority earning profiles follow depending on whether the individual is employed in a workplace where trade unions and collective bargaining are present, or not. Within this framework, two propositions are set. In the union sector seniority should be an important determinant of wages, while in the non‐union sector productivity, proxied by occupational experience, should have a key role on earning profiles. The empirical analysis verifies both propositions. Seniority earning profiles appear to be steeper in the union sector, while occupational expertise is estimated to have a more significant role in non‐union jobs.
The Productivity Effects of Internal and External R&D: Evidence from a Dynamic Panel Data Model*
Authors: Lokshin Boris , Belderbos René , Carree Martin
Published: May 2008

We examine the impact of internal and external R&D on labour productivity in a 6‐year panel of Dutch manufacturing firms. We apply a dynamic panel data model that allows for decreasing or increasing returns to scale in internal and external R&D and for economies of scope. We find complementarity between internal and external R&D, with a positive impact of external R&D only evident in case of sufficient internal R&D. These findings confirm the role of internal R&D in enhancing absorptive capacity. The scope economies are accompanied by decreasing returns to scale at high levels of internal and external R&D. The analysis indicates that productivity grows by increasing the share of external R&D in total R&D.
On Structuring Subjective Judgements: originality, Significance and Rigour in RAE2008
Authors: Johnston Ron
Published: May 2008

The 2008 United Kingdom Research Assessment Exercise will involve the evaluation of thousands of individual research outputs. The Funding Councils set three criteria for those evaluations – Originality, rigour and significance – and required each output to be placed into a fivefold categorisation of excellence, using absolute rather than relative judgements. The various panels and sub‐panels convened to undertake those evaluations were asked to provide their own interpretations of both the criteria and the categories. This paper analyses those, and finds that they are no less subjective than the generic descriptions provided by the central organisation.
Quality Assurance and Quality Enhancement in Higher Education: Contested Territories?
Authors: Filippakou Ourania , Tapper Ted
Published: May 2008

This paper analyses the unfolding of the quality agenda in England from 1992 to the present. By using two disciplinary approaches, ‘political science’ and ‘social philosophy’, the article traces the recent transition from quality assurance to quality enhancement. How is this development to be explained and how significant is it? Are the concepts of quality assurance and quality enhancement contested territories? The article argues that the undermining of quality assurance was the consequence of the emergence of a different kind of higher education politics in Britain: the shift from a corporatist model to one driven by pressure‐group politics. Furthermore, although theoretically quality enhancement has the potential of a transformative discourse, it is unlikely to unsettle the relative stable structures in which quality assurance functions.
On Process, Progress, Success and Methodology or the Unfolding of the Bologna Process as it Appears to Two Reasonably Benign Observers
Authors: Neave Guy , Amaral Alberto
Published: May 2008

This article examines the Bologna Process from two main perspectives: as a dynamic strategy as well as the unfolding of the methodology employed. It argues that the latter was largely determined by the former. Three phases of development are identified; the first two of which shows that the methodology was largely determined by the need to bestow credibility on the strategy. The third phase, introduced with the recent Ministerial meeting in London in May 2007 suggests that the boundless confidence in the progress achieved at system level has now given way to a new sobriety when attention to progress is translated to institutional level. It concludes that there are excellent grounds for rethinking the basic strategy behind the Bologna Process.
Towards a ‘Post‐Public Era’? Shifting Frames in German and Australian Higher Education Policy
Authors: Pick David
Published: May 2008

Higher education in Germany and Australia is being subject to pressures of market forces, internationalisation and financial constraints. This had led to both systems experiencing significant crisis and change over the past 20 years. In this paper, frame analysis is used to compare the changing policies in each nation and examine the extent to which the landscapes of each system have been transformed. It is found that higher education policy in both nations underwent significant change in the late 1980s and again in the early 2000s, impacting on system structures and institutional forms. There is now evidence of further change occurring in both nations that may mark a transition to a ‘post‐public era’ in higher education. This analysis reveals a degree of convergence in the neo‐liberal policy trajectories of both nations but differences in the rate and nature of the transitions taking place.
Increased Cerebral Vasomotor Reactivity in Migraine With Aura: An Autoregulation Disorder? A Transcranial Doppler and Near-Infrared Spectroscopy Study
Authors: Vernieri F , Tibuzzi F , Pasqualetti P , Altamura C , Palazzo P , Rossini PM , Silvestrini M
Published: May 2008

Migraine with aura (MA) is associated with changes in cerebral blood flow (CBF), whereas the role of cerebral autoregulation is uncertain. This study aimed to evaluate basal CBF, cerebral blood volume (CBV) and vasomotor reactivity (VMR) in MA patients. Twenty-one controls and 16 MA patients (eight with side predominance) underwent simultaneous examination of flow velocity in the middle cerebral arteries by transcranial Doppler (TCD) and of near-infrared spectroscopy (NIRS) parameters [oxygen haemoglobin saturation: oxygen%, and total haemoglobin content (THC)] at rest and after hypercapnia. Cerebral VMR, THC and oxygen% increases were significantly greater on the predominant compared with the non-predominant migraine side, with both sides of patients without side predominance and with controls. These findings suggest altered autoregulation in MA patients, possibly secondary to impaired cerebrovascular autonomic control. Simultaneous TCD and NIRS investigation could represent a non-invasive approach to evaluate cerebral haemodynamics at the cortical and subcortical level.
The Causal Attributions of Teaching Staff Towards Children with Intellectual Disabilities: A Comparison of ‘Vignettes’ Depicting Challenging Behaviour with ‘Real’ Incidents of Challenging Behaviour
Authors: Lucas Victoria L. , Collins Suzanne , Langdon Peter E.
Published: May 2008

Background We examined whether staff attributions, emotions and helping behaviours in reaction to ‘real’ incidents of challenging behaviour (CB) exhibited by children with intellectual disabilities were different from reactions to ‘vignettes’. We also examined whether these reactions are congruent with that predicted by attribution theory.

Methods Using a repeated measures design, 60 staff working with children who have severe intellectual disabilities completed measures of cognition, emotion and helping behaviour in reaction to a ‘real’ incident of CB, and then completed the same measures in reaction to reading a ‘vignette’, that was matched to the ‘real’ incident of CB. There was a 2‐week interval between the completion of measures in response to the ‘real’ incident of CB and the ‘vignette’.

Results Correlational support was found forWeiner’s (1980)cognitive–emotional–action model of helping behaviour for measures completed in reaction to the ‘real’ incident of CB, regarding attributions of control only, but not for the ‘vignette’. There were significant differences between the correlations detected using ‘real’ incidents of CB in comparison to ‘vignettes’. Little evidence was found using both methods to supportWeiner’s (1979)model of achievement motivation.

Conclusions The results suggest that the relationships between constructs investigated using ‘vignettes’ is different from that detected when using ‘real’ incidents of CB, which has implications for psychological research that has used ‘vignettes’.
Correlation Analyses Reveal a Substantial Influence of Allelic Gaps on the Investigation of Genetic Diversity of Modern Human Populations with Microsatellites
Authors: Guha S. , Chakraborty R.
Published: May 2008

High intra‐population genetic diversity and multiple measures of genetic variability at STR loci are useful in inferring past evolutionary history. However, STRs, categorized by their repeat motif size, differ in a number of aspects, requiring separate analyses. We analyzed 783 STRs in 36 worldwide populations to examine marker suitability as well as correlations between various measurements, to evaluate the extent of genomic diversity present in modern human populations. The loci were grouped by type and analyzed separately for each population group. Genetic variation defined by gene diversity and allele size variance, shows different trends of variation across four types of STRs. Additionally, there is little variation of genetic diversity, but there is decreased allelic size variance with increasing repeat motifs. A poor correlation between genetic diversity and allelic size variance across loci in all groups for Di‐STRs is probably caused by the presence of allelic size gaps. In contrast, allelic size variance, genetic diversity, and number of alleles are strongly correlated with both tri‐ and tetra‐STRs. The positive correlation of allelic size variance and presence of gaps within the range of allelic sizes in Di‐STRs alone explains these observations. An unexpected high imbalance index (β) at Di‐STRs due to high allelic size variance also supports this assertion.
Genetic Epidemiology of Subclinical Cardiovascular Disease in the Diabetes Heart Study
Authors: Bowden D. W. , Lehtinen A. B. , Ziegler J. T. , Rudock M. E. , Xu J. , Wagenknecht L. E. , Herrington D. M. , Rich S. S. , Freedman B. I. , Carr J. J. , Langefeld C. D.
Published: May 2008

A genome‐wide linkage scan of 357 European American (EA) and 72 African American (AA) pedigrees multiplex for type 2 diabetes mellitus (T2DM) was performed with multipoint nonparametric QTL linkage analysis. Four subclinical measures of cardiovascular disease (CVD): coronary artery (CCP), carotid artery (CarCP), and abdominal aortic calcified plaque (AACP) and carotid artery intima‐media thickness (IMT) were mapped. Analyses were adjusted for age, gender, body mass index, and (if appropriate) ethnicity and diabetes status.

Evidence for linkage was observed in EA T2DM subjects to CarCP near 16p13 (LOD=4.39 at 8.4 cM; P = 0.00001). When all EA subjects were included, the LOD score was 2.52, suggesting an amplification of the linkage by diabetes. Linkage analysis of a principal components measure of vascular calcium (LOD = 3.85 at 9.3 cM on 16p in EA T2DM subjects) and bivariate analysis of CarCP X IMT (LOD = 3.77 at 9.3 cM on 16p in EA T2DM subjects) were consistent with this linkage. In addition, evidence for linkage was observed with CCP near D15S1515 (LOD = 2.34) in EAs. Additional loci on chromosomes 1, 2, 7, 10, 13, and 21 had LODs > 2.0. The identification of trait‐determining polymorphisms underlying these linkages will help delineate risk factors for CVD in T2DM and the general population.
Distribution of zinedin in the rat brain
Authors: Benoist Marion , Baude Agnès , Tasmadjian Armand , Dargent Bénédicte , Kessler Jean‐Pierre , Castets Francis
Published: May 2008

Members of the striatin family are scaffolding proteins involved in numerous signaling pathways principally in neurons. Zinedin is the only member of this protein family for which the brain distribution has not been determined so far. Here, we have validated a specific antibody against zinedin and used this tool to study the localization of zinedin at cellular and sub‐cellular levels in the rat brain. Zinedin is primarily expressed in neurons of the hippocampus, cerebral cortex, olfactory bulb and caudate putamen nucleus. Like other members of the striatin family, zinedin displays a polarized distribution in the somato‐dendritic compartment of neurons and is enriched in dendritic spines. The rostral expression of zinedin as well as its compartmented distribution in dendritic spines may have important implications not only for zinedin function but also in the physiology of dendritic spines of a particular subset of neurons.
Extracellular signal‐regulated kinases (ERK) and protein kinase C (PKC) activities are involved in the modulation of Nur77 and Nor‐1 expression by dopaminergic drugs
Authors: Bourhis Emmanuelle , Maheux Jérôme , Rouillard Claude , Lévesque Daniel
Published: May 2008

The dopamine system is the main target of antipsychotic and psychostimulant drugs. These drugs induce intracellular events that culminate in the transcription of immediate early genes, such as c‐fos. Another class of transcription factors, namely, the nuclear receptor subgroup called Nurs (Nur77, Nurr1 and Nor‐1), has recently been associated with behavioral and biochemical effects mediated by dopamine. However, the signaling cascade leading to modulation of Nur mRNA levels in the brain has never been investigated. In the present study, we explore in vivo using specific kinase inhibitors the role of mitogen‐associated and extracellular signal‐regulated kinases (MEK) and protein kinase C (PKC) in the modulation of Nur expression induced by dopamine receptor drugs. Modulation of Nur77 expression by a dopamine D2 receptor antagonist is associated with MEK and PKC activities, whereas only the PKC activity participates in the modulation of Nor‐1 expression. Both MEK and PKC activities also participate in the modulation of Nur77 mRNA levels induced by dopamine receptor agonists, whereas a selective MEK activity is associated with the modulation of Nor‐1 mRNA levels. Interestingly, modulation of dopamine drug‐induced locomotor activities by kinase inhibitors is in accordance with the effects on Nur77, but not Nor‐1, expression. Taken together, the results indicate that signaling events leading to modulation of Nur77 and Nor‐1 expression following dopamine receptor interacting drugs are distinct. Considering that orphan nuclear receptors of the Nur subgroup display an important ligand‐independent constitutive activity, characterization of the signaling cascades involved in the regulation of their expression represents an important step for understanding their role in dopamine system physiology and pathophysiology.
Adaptation to chronic MG132 reduces oxidative toxicity by a CuZnSOD‐dependent mechanism
Authors: Leak Rehana K. , Zigmond Michael J. , Liou Anthony K. F.
Published: May 2008

To study whether and how cells adapt to chronic cellular stress, we exposed PC12 cells to the proteasome inhibitor MG132 (0.1 μM) for 2 weeks and longer. This treatment reduced chymotrypsin‐like proteasome activity by 47% and was associated with protection against both 6‐hydroxydopamine (6‐OHDA; 100 μM) and higher dose MG132 (40 μM). Protection developed slowly over the course of the first 2 weeks of exposure and was chronic thereafter. There was no change in total GSH levels after MG132. Buthionine sulfoximine (100 μM) reduced GSH levels by 60%, but exacerbated 6‐OHDA toxicity to the same extent in both MG132‐treated and control cells and failed to reduce MG132‐induced protection. Chronic MG132 resulted in elevated antioxidant proteins CuZn superoxide dismutase (SOD; +55%), MnSOD (+21%), and catalase (+15%), as well as chaperone heat‐shock protein 70 (+42%). Examination of SOD enzyme activity revealed higher levels of CuZnSOD (+40%), with no change in MnSOD. We further assessed the mechanism of protection by reducing CuZnSOD levels with two independent siRNA sequences, both of which successfully attenuated protection against 6‐OHDA. Previous reports suggested that artificial over‐expression of CuZnSOD in dopaminergic cells is protective. Our data complement such observations, revealing that dopaminergic cells are also able to use endogenous CuZnSOD in self‐defensive adaptations to chronic stress, and that they can even do so in the face of extensive GSH loss.
Megalin is a receptor for albumin in astrocytes and is required for the synthesis of the neurotrophic factor oleic acid
Authors: Bento‐Abreu André , Velasco Ana , Polo‐Hernández Erica , Pérez‐Reyes Pedro Luis , Tabernero Arantxa , Medina José M.
Published: May 2008

We have previously shown that the uptake and transcytosis of albumin in astrocytes promote the synthesis of the neurotrophic factor oleic acid. Although the mechanism by which albumin induces oleic acid synthesis is well known, the mechanism of albumin uptake in astrocytes remains unknown. In this work, we found that astrocytes express megalin, an endocytic receptor for multiple ligands including albumin. In addition, when the activity of megalin is blocked by specific antibodies or by silencing megalin with specific siRNA, albumin binding and internalization is strongly reduced indicating that megalin is required for albumin binding and internalization in the astrocyte. Since the uptake of albumin in astrocytes aims at synthesizing the neurotrophic factor oleic acid, we tested the ability of megalin‐silenced astrocytes to synthesize and release oleic acid in the presence of albumin. Our results showed that the amount of oleic acid found in the extracellular medium of megalin‐silenced astrocytes was strongly reduced as compared with their controls. Together, the results of this work indicate that megalin is a receptor for albumin in astrocytes and is required for the synthesis of the neurotrophic factor oleic acid. Consequently, the possible involvement of albumin in the holoprosencephalic syndrome observed in megalin‐deficient mice is suggested.
Stem Cell Review Series: Aging of the skeletal muscle stem cell niche
Authors: Gopinath Suchitra D. , Rando Thomas A.
Published: May 2008

Declining stem cell function during aging contributes to impaired tissue function. Muscle‐specific stem cells (‘satellite cells’) are responsible for generating new muscle in response to injury in the adult. However, aged muscle displays a significant reduction in regenerative abilities and an increased susceptibility to age‐related pathologies. This review describes components of the satellite cell niche and addresses how age‐related changes in these components impinge on satellite cell function. In particular, we review changes in the key niche elements, the myofiber and the basal lamina that are in intimate contact with satellite cells. We address how these elements are influenced by factors secreted by interstitial cells, cells of the immune system, and cells associated with the vasculature, all of which change with age. In addition, we consider more distant sources of influence on the satellite cell niche that change with age, such as neural‐mediated trophic factors and electrical activity and systemic factors present in the circulation. A better understanding of the niche elements and their influence on the satellite cell will facilitate the development of therapeutic interventions aimed at improving satellite cell activity and ultimately tissue response to injury in aged individuals.
Stacking the Deck: Idling and Reactivation of Capacity in Offshore Drilling
Authors: Corts Kenneth S.
Published: May 2008

Independent drilling contractors own all offshore drilling rigs, which they lease to oil and gas companies for use in their pursuit of their exploration and development plans. Oil and gas companies' demand for these rigs can vary quickly and dramatically in response to changes in the world market for oil and natural gas. As a result, drilling contractors often try to manage excess capacity by idling rigs (known in the industry as “stacking” a rig), reactivating them when demand recovers. This paper examines these decisions over the course of a price cycle in 1998–2000 to investigate the role of firm and rig heterogeneity in determining drillers' decisions about idling and reactivating capacity.
The Implications of Trade Credit for Bank Monitoring: Suggestive Evidence from Japan
Authors: Miwa Yoshiro , Ramseyer J. Mark
Published: May 2008

Firms in modern developed economies borrow from both banks and trade partners. Using Japanese manufacturing data from the 1960s, we estimate the price of trade credit, and explore some of the ways firms choose between the credit and bank loans. We find that firms of all sizes borrow heavily from their trade partners, and at implicit rates that track the explicit rates banks would charge. They borrow from banks when they anticipate needing money for relatively long periods; they turn to trade partners when they face short‐term unexpected exigencies. This apparent contrast in the term structures follows, we suggest, from the fundamentally different way bankers and trade partners cut default risk. Because bankers seldom know their borrowers' industries first hand, they rely on formal legal protection (like security interests). Because trade partners know the industry well, they reduce risk by monitoring their borrowers closely instead. Because the costs to creating legal mechanisms are heavily front‐loaded, bankers focus on long‐term debt; because the costs of monitoring debtors are ongoing, trade creditors do not. Apparently, banks monitor less than we have thought.
Technology Adoption with Multiple Alternative Designs and the Option to Wait
Authors: Cabral Luís , Dezső Cristian
Published: May 2008

Technology adoption is one the most important elements of a firm's strategy. In this paper, we address an essential, yet largely overlooked, question: What should a firm do when faced with several alternative proprietary designs of a new technology? In our base case we assume there are two technology designs, each described by an independent stochastic process of technology evolution. We show that, in equilibrium, a buyer chooses the leading technology design as soon as the discounted payoff from doing so is positive. When the option value of waiting is very high, it is jointly optimal to delay adoption. But because sellers cannot commit not to extract all of the buyer's future rents, inefficiently early adoption takes place. Strategies that improve commitment to low future license fees, such as increasing the number of competitors or cross‐licensing, may alleviate the hold up problem. Although previous research stressed the benefit of such commitments in terms of increasing the rate of technology adoption, we present a class of cases when the benefit from commitment is efficiently to delay adoption.
On Some Procedures of Forming a Multipartner Alliance
Authors: De Ridder Annelies , Rusinowska Agnieszka
Published: May 2008

In the article, we study two different ways of forming multipartner alliances between firms with the central idea that procedure is an important factor in multipartner alliance formation. In the first procedure, an alliance is formed simultaneously, while in the second procedure (step‐by‐step) members are added one by one. In the model we present, each firm is assumed to have a multidimensional maneuvering space, which consists of all alliance positions acceptable to the firm, and an ideal position in this space. Alliances will form between the firms whose maneuvering spaces overlap. The results of the analysis confirm that procedure is an important factor in multipartner alliance formation. Nevertheless, if ideal positions of firms are acceptable to all alliance partners, then the result of alliance formation does not depend on procedure. In addition, it is shown that it can be disadvantageous to be a first mover. Finally, we are able to provide sufficient conditions under which one procedure is preferred in a three‐partner case. More specifically, a firm with its ideal position acceptable to the two other firms may prefer the simultaneous procedure to being a late mover if (1) there is a certain balance in the firms' degree of flexibility and their power and (2) if the agreed alliance position of the two other firms is acceptable to the firm in question.
Hemolytic transfusion reactions after administration of intravenous immune (gamma) globulin: a case series analysis
Authors: Daw Zohra , Padmore Ruth , Neurath Doris , Cober Nancy , Tokessy Melanie , Desjardins Diane , Olberg Bernhard , Tinmouth Alan , Giulivi Antonio
Published: May 2008

BACKGROUND: This case series summarizes our observations of hemolytic reactions after the administration of large amounts of intravenous immune (gamma) globulin (IVIG).

STUDY DESIGN AND METHODS: Cases of hemolysis were identified by a decrease in hemoglobin not otherwise explained following IVIG administration.

RESULTS: Sixteen cases were identified over a 2½‐year period at the Ottawa Hospital of approximately 1000 patients receiving IVIG (1.6%). Characteristics of these patients include a large dose of IVIG, female sex, non‐O blood group, and underlying inflammatory state.

CONCLUSIONS: Significant hemolysis may occur after the administration of large doses of IVIG. A two‐step mechanism of hemolysis is proposed, sensitization by ABO isohemagglutinins followed by phagocytosis by activated macrophages. A simple protocol to facilitate the early detection of such cases is presented.
Can a Coherent Risk Measure Be Too Subadditive?
Authors: Dhaene J. , Laeven R. J. A. , Vanduffel S. , Darkiewicz G. , Goovaerts M. J.
Published: May 2008

Abstract

We consider the problem of determining appropriate solvency capital requirements for an insurance company or a financial institution. We demonstrate that the subadditivity condition that is often imposed on solvency capital principles can lead to the undesirable situation where the shortfall risk increases by a merger. We propose to complement the subadditivity condition by a regulator's condition. We find that for an explicitly specified confidence level, the Value‐at‐Risk satisfies the regulator's condition and is the “most efficient” capital requirement in the sense that it minimizes some reasonable cost function. Within the class of concave distortion risk measures, of which the elements, in contrast to the Value‐at‐Risk, exhibit the subadditivity property, we find that, again for an explicitly specified confidence level, the Tail‐Value‐at‐Risk is the optimal capital requirement satisfying the regulator's condition.
The Role of Internal Capital Markets in Financial Intermediaries: Evidence From Insurer Groups
Authors: Powell Lawrence S. , Sommer David W. , Eckles David L.
Published: May 2008

Abstract

We exploit the transparency of internal capital markets (ICMs) within insurance groups to investigate the activity and efficiency of ICMs within insurance groups. Specifically, we compare the relationship between internal capital transfers and investment to that between capital from other sources and investment. The ability to track the actual ICM transactions allows for more direct analysis of ICM activity than most previous studies. Consistent with theory, we find evidence that ICMs play a significant role in the investment behavior of affiliated insurers. We then use these detailed data to execute a more direct test of ICM efficiency than currently exists in the literature. Consistent with ICM efficiency, results suggest that capital is allocated to subsidiaries with the best expected performance.
Complex Electrograms Within the Coronary Sinus: Time‐ and Frequency‐Domain Characteristics, Effects of Antral Pulmonary Vein Isolation, and Relationship to Clinical Outcome in Patients with Paroxysmal and Persistent Atrial Fibrillation
Authors: YOSHIDA KENTARO , ULFARSSON MAGNUS , TADA HIROSHI , CHUGH AMAN , GOOD ERIC , KUHNE MICHAEL , CRAWFORD THOMAS , SARRAZIN JEAN F. , CHALFOUN NAGIB , WELLS DARRYL , JONGNARANGSIN KRIT , PELOSI FRANK , BOGUN FRANK , MORADY FRED , ORAL HAKAN
Published: May 2008

Background:
The mechanistic and clinical significance of complex fractionated atrial electrograms (CFAE) in the coronary sinus (CS) has been unclear.

Methods and Results:
Antral pulmonary vein isolation (APVI) was performed in 77 patients with paroxysmal (32) or persistent AF (45). CS electrograms recorded for 60 seconds before and after APVI were analyzed in the time‐ and frequency‐domains. Dominant frequency (DF), complexity index (CI: change in polarity of depolarization), and fractionation index (FI: change in direction of depolarization slope) were determined. Before APVI, there was no difference in DF, CI, or FI between paroxysmal and persistent AF. APVI resulted in a significant decrease in DF, CI, and FI in all patients. Baseline CI (43 ± 13/s vs 54 ± 14/s, P = 0.03) and FI (64 ± 23/s vs 87 ± 30/s, P = 0.02) were lower in patients with paroxysmal AF who had AF terminated by ablation than who did not. At 10 ± 2 months, 69% of patients with paroxysmal AF and 49% of patients with persistent AF were free from AF after single ablation. Baseline CI was higher among patients with paroxysmal AF who had AF after APVI (56 ± 20/s vs 44 ± 10/s, P = 0.03). In patients with persistent AF, there was a larger decrease in DF after APVI among patients who remained free from AF (13 ± 11% vs 7 ± 9%, P < 0.05).

Conclusions:
Complexity of CS electrograms may reflect drivers of AF that perpetuate paroxysmal AF after APVI. In persistent AF, the extent to which APVI decreases DF in the CS correlates with efficacy, suggesting that DF identifies patients who may require additional ablation beyond APVI.
Challenges to the Diagnosis, Evaluation, Treatment, and Management of Clustered Cardiometabolic Risk Factors
Authors: Bakris George , Fonseca Vivian , Foody JoAnne
Published: May 2008

A panel was convened on January 10, 2007, to discuss the challenges to the diagnosis, evaluation, treatment, and management of clustered cardiometabolic risk factors. George Bakris, MD, Professor of Medicine, University of Chicago, Chicago, IL, moderated the panel. Vivian Fonseca, MD, Tulane University Health Science Center, New Orleans, LA, and JoAnne Foody, MD, Harvard School of Medicine, Boston, MA, participated in the discussion. This expert panel discussion was supported by and each author received an honorarium from Merck & Co, Inc, and Sanofi‐Aventis for time and effort spent participating in the discussion and reviewing the transcript for important intellectual content before publication. The authors maintained full control of the discussion and the resulting content of this article.
Apoptosis‐related mitochondrial dysfunction defines human monocyte‐derived dendritic cells with impaired immuno‐stimulatory capacities
Authors: Castera Laurent , Hatzfeld‐Charbonnier Anne Sophie , Ballot Caroline , Charbonnel Florence , Dhuiege Edith , Velu Thierry , Formstecher Pierre , Mortier Laurent , Marchetti Philippe
Published: May 2008

The death of dendritic cells (DCs) can potentially influence immune responses by affecting the duration of DC stimulation of lymphocytes. Here, we report that cultured mature monocyte‐derived DCs manifest early mitochondrial damage (i.e. within 24 hrs), characterized by mitochondrial membrane potential (ψΔm) disruption and mitochondrial release of pro‐apoptotic factors, followed by reactive oxygen species (ROS) production and activation of caspases. Afterwards, DCs with mitochondrial alterations are condemned to undergo apoptosis and necrosis. Macroarray analysis results (validated by real time quantitative‐PCR (QRT‐PCR) and immunoblotting), showed up‐regulation of the pro‐apoptotic member of the Bcl‐2 family, Bim, while expression of several anti‐apoptotic molecules was down‐regulated. Importantly, pre‐apoptotic DCs (characterized by a low Δψm) showed a modified phenotype, with down‐regulation.of HLA‐DR and of the co‐stimulatory molecules CD80 and CD86. Moreover, sorted viable low ψΔm DCs were unable to activate allogeneic T cells, indicating that pre‐apoptotic DCs have already lost some of their immuno‐stimulatory capabilities long before any detectable signs of death occur. Perturbations to mitochondrial respiration with rotenone identified the same modifications to DC immune functions. These data indicate a strong requirement for mitochondrial integrity for the immuno‐stimulatory capacities of DC. Determining ΔΨm could be a useful parameter to select ‘fully’ functional DCs for anti‐tumour vaccines.
Increasing experimental approaches in stream trout research – 1987–2006
Authors: Northcote T. G. , Lobón‐Cerviá J.
Published: May 2008

Abstract – This review of stream trout research literature for the 1987–2006 period covered >1300 papers dealing with 22 relevant topics, when compared with <400 papers on 18 topics in the previous one (1967–1986). The percentage of experimental approaches here quantified for both research reviews was 18% in the 1967–1976 period, increased to 21% in 1977–1986, to 39% in 1987–1996, and up to 43% in 1997–2006. Particular journals in the recent two decadal period published high percentages of experimental papers (The Journal of Animal EcologyandCanadian Journal of Fisheries and Aquatic Sciences; 62.9% and 62.4%, respectively), others, intermediate percentages (Nordic Journal of Fisheries Research,Transactions of the American Fisheries Society,North American Journal of Fisheries ManagementandEcology of Freshwater Fish: 44.1%, 42.4%, 40.5%, and 35.6%, respectively); the remainder covered ≤33%. Research papers on stream ‘trouts’ published over the last two decades were classified into 22 subject areas for nine major journals separately and combined for 55 other journals. Subject areas dealing with the biology and ecology of trout redds, egg development, alevin emergence and onto fry and parr were the most heavily reported in nine major journals, as well as in all other journals combined. Habitat characteristics and cover use by trout were the next. Atlantic salmon and brown trout were the species with highest publication coverage in nearly all subject areas, with low coverage for all salvelinid (charr) species except brook charr. Research on Atlantic salmon in the UK used experimental approaches in nearly 60% of publications and in mid to high 30% for those on Atlantic salmon and brown trout in Scandinavian countries. Consideration is given to future research needs for stream trouts.
Neonatal resuscitation after severe asphyxia – a critical evaluation of 177 Swedish cases
Authors: Berglund Sophie , Norman Mikael , Grunewald Charlotta , Pettersson Hans , Cnattingius Sven
Published: May 2008

Aim: To evaluate neonatal resuscitation of infants born with severe asphyxia.

Method: All case records of the 472 claims for financial compensation due to suspected medical malpractice in conjunction with childbirth in Sweden between 1990 and 2005 were scrutinized. Inclusion criteria were: gestational age ≥33 completed weeks, planned vaginal onset of delivery, a reactive CTG at onset of labour, neonatal asphyxia (defined as metabolic acidosis {pH of < 7.05 and/or a base excess of < –12}), or an Apgar score <7 at 5 min. It was assessed that 177 infants suffered from cerebral palsy or early death due to severe asphyxia presumably caused by malpractice around labour.

Results: Median Apgar score at 5 min was 3, indicating that all infants needed immediate and extensive resuscitation. There was insufficient adherence to guidelines concerning neonatal resuscitation, including delayed initiation of excessive resuscitation in 19 infants, lack of satisfactory ventilation in 79 infants, and untimely interruption of resuscitation in 38 infants.

Conclusions: Compliance with guidelines for resuscitation of severely asphyctic newborn may be improved, especially concerning ventilation and prompt paging for skilled personnel in cases of imminent asphyxia. Documentation of neonatal resuscitation must be improved to enable reliable evaluation.
Visual screening versus transcutaneous bilirubinometry for predischarge jaundice assessment
Authors: Kaplan Michael , Shchors Irena , Algur Nurit , Bromiker Ruben , Schimmel Michael S , Hammerman Cathy
Published: May 2008

Objective: Comparison of visual screening with transcutaneous bilirubinometry (TcB) in identifying neonates with plasma total bilirubin (PTB) ≥75th percentile.

Design: In 100 paired readings PTB was 34 ± 24 μmol/L higher than the TcB counterpart. A TcB reading of 154 μmol/L was therefore regarded as equivalent to a PTB of 188 μmol/L, corresponding to the 75th percentile at 48 h. Predischarge, all newborns were evaluated for jaundice, first by visual inspection and then transcutaneously. PTB was ordered as indicated by visual assessment or if the TcB reading was ≥154 μmol/L.

Results: Of 346 newborns tested, 25 (7.2%) had a PTB concentration ≥75th percentile. Forty‐nine had PTB determinations based on TcB compared with 83 by visual assessment. However, a similar number of affected newborns was identified by each method (21/25 (84%) by visual screening vs. 18/25 (72%) by TcB). PTB concentrations of those who had been chosen by TcB were higher than those selected visually (202 ± 24 μmol/L vs. 186 ± 31 μmol/L).

Conclusions: A practical method for predischarge detection of neonates with plasma total bilirubin concentration ≥ 75th percentile, implementing transcutaneous bilirubinometry, is described. The transcutaneous technique required fewer blood tests than visual assessment for similar yield.