Showing papers by "University of Wisconsin-Madison published in 2000"
TL;DR: This review focuses on model predictive control of constrained systems, both linear and nonlinear, and distill from an extensive literature essential principles that ensure stability to present a concise characterization of most of the model predictive controllers that have been proposed in the literature.
8,064 citations
TL;DR: The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a "nanostressing stage" located within a scanning electron microscope and a variety of structures were revealed, such as a nanotube ribbon, a wave pattern, and partial radial collapse.
Abstract: The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a “nanostressing stage” located within a scanning electron microscope. The tensile-loading experiment was prepared and observed entirely within the microscope and was recorded on video. The MWCNTs broke in the outermost layer (“sword-in-sheath” failure), and the tensile strength of this layer ranged from 11 to 63 gigapascals for the set of 19 MWCNTs that were loaded. Analysis of the stress-strain curves for individual MWCNTs indicated that the Young's modulus E of the outermost layer varied from 270 to 950 gigapascals. Transmission electron microscopic examination of the broken nanotube fragments revealed a variety of structures, such as a nanotube ribbon, a wave pattern, and partial radial collapse.
5,011 citations
TL;DR: A dose-response association between sleep-disordered breathing at base line and the presence of hypertension four years later was found that was independent of known confounding factors and suggest that sleep- disordered breathing is likely to be a risk factor for hypertension and consequent cardiovascular morbidity in the general population.
Abstract: Background Sleep-disordered breathing is prevalent in the general population and has been linked to chronically elevated blood pressure in cross-sectional epidemiologic studies. We performed a prospective, population-based study of the association between objectively measured sleep-disordered breathing and hypertension (defined as a laboratory-measured blood pressure of at least 140/90 mm Hg or the use of antihypertensive medications). Methods We analyzed data on sleep-disordered breathing, blood pressure, habitus, and health history at base line and after four years of follow-up in 709 participants of the Wisconsin Sleep Cohort Study (and after eight years of follow-up in the case of 184 of these participants). Participants were assessed overnight by 18-channel polysomnography for sleep-disordered breathing, as defined by the apnea–hypopnea index (the number of episodes of apnea and hypopnea per hour of sleep). The odds ratios for the presence of hypertension at the four-year follow-up study according to...
4,429 citations
TL;DR: In this paper, the authors developed a statistical theory for threshold estimation in the regression context, which is shown to yield asymptotically conservative confidence regions and Monte Carlo simulations are presented to assess the accuracy.
Abstract: .Threshold models have a wide variety of applications in economics. Direct applications include models of separating and multiple equilibria. Other applications include empirical sample splitting when the sample split is based on a continuously-distributed variable such as firm size. In addition, threshold models may be used as a parsimonious strategy for nonparametric function estimation. For example, the threshold autoregressive model .TAR is popular in the nonlinear time series literature. Threshold models also emerge as special cases of more complex statistical frameworks, such as mixture models, switching models, Markov switching models, and smooth transition threshold models. It may be important to understand the statistical properties of threshold models as a preliminary step in the development of statistical tools to handle these more complicated structures. Despite the large number of potential applications, the statistical theory of threshold estimation is undeveloped. It is known that threshold estimates are super-consistent, but a distribution theory useful for testing and inference has yet to be provided. This paper develops a statistical theory for threshold estimation in the regression context. We allow for either cross-section or time series observations. Least squares estimation of the regression parameters is considered. An asymptotic distribution theory . for the regression estimates the threshold and the regression slopes is developed. It is found that the distribution of the threshold estimate is nonstandard. A method to construct asymptotic confidence intervals is developed by inverting the likelihood ratio statistic. It is shown that this yields asymptotically conservative confidence regions. Monte Carlo simulations are presented to assess the accuracy of the asymptotic approximations. The empirical relevance of the theory is illustrated through an application to the multiple . equilibria growth model of Durlauf and Johnson 1995 .
2,353 citations
TL;DR: In this article, a focus on the contextually specific ways in which people act out and recognize identities allows a more dynamic approach than the sometimes overly general and static trio of "race, class, and gender".
Abstract: n today's fast changing and interconnected global world, researchers in a variety of areas have come to see identity as an important analytic tool for understanding schools and society. A focus on the contextually specific ways in which people act out and recognize identities allows a more dynamic approach than the sometimes overly general and static trio of "race, class, and gender." However, the term identity has taken on a great many different meanings in the literature. Rather than survey this large literature, I will sketch out but one approach that draws on one consistent strand of that literature. This is not to deny that other, equally useful approaches are possible, based on different selections from the literature.
2,349 citations
TL;DR: This paper demonstrates the benefits of cache sharing, measures the overhead of the existing protocols, and proposes a new protocol called "summary cache", which reduces the number of intercache protocol messages, reduces the bandwidth consumption, and eliminates 30% to 95% of the protocol CPU overhead, all while maintaining almost the same cache hit ratios as ICP.
Abstract: The sharing of caches among Web proxies is an important technique to reduce Web traffic and alleviate network bottlenecks. Nevertheless it is not widely deployed due to the overhead of existing protocols. In this paper we demonstrate the benefits of cache sharing, measure the overhead of the existing protocols, and propose a new protocol called "summary cache". In this new protocol, each proxy keeps a summary of the cache directory of each participating proxy, and checks these summaries for potential hits before sending any queries. Two factors contribute to our protocol's low overhead: the summaries are updated only periodically, and the directory representations are very economical, as low as 8 bits per entry. Using trace-driven simulations and a prototype implementation, we show that, compared to existing protocols such as the Internet cache protocol (ICP), summary cache reduces the number of intercache protocol messages by a factor of 25 to 60, reduces the bandwidth consumption by over 50%, eliminates 30% to 95% of the protocol CPU overhead, all while maintaining almost the same cache hit ratios as ICP. Hence summary cache scales to a large number of proxies. (This paper is a revision of Fan et al. 1998; we add more data and analysis in this version.).
2,174 citations
TL;DR: It is posited that impulsive aggression and violence arise as a consequence of faulty emotion regulation, and the prefrontal cortex receives a major serotonergic projection, which is dysfunctional in individuals who show impulsive violence.
Abstract: Emotion is normally regulated in the human brain by a complex circuit consisting of the orbital frontal cortex, amygdala, anterior cingulate cortex, and several other interconnected regions. There are both genetic and environmental contributions to the structure and function of this circuitry. We posit that impulsive aggression and violence arise as a consequence of faulty emotion regulation. Indeed, the prefrontal cortex receives a major serotonergic projection, which is dysfunctional in individuals who show impulsive violence. Individuals vulnerable to faulty regulation of negative emotion are at risk for violence and aggression. Research on the neural circuitry of emotion regulation suggests new avenues of intervention for such at-risk populations.
1,788 citations
TL;DR: The clonal derivation of two human ES cell lines, H9.1 and H.2, demonstrates the pluripotency of single human ES cells, the maintenance of pluripOTency during an extended period of culture, and the long-term self-renewing properties of cultured human ES Cells.
1,680 citations
TL;DR: The data indicate that clinical and public health programs that result in even modest weight control are likely to be effective in managing SDB and reducing new occurrence of SDB.
Abstract: ContextExcess body weight is positively associated with sleep-disordered breathing
(SDB), a prevalent condition in the US general population. No large study
has been conducted of the longitudinal association between SDB and change
in weight.ObjectiveTo measure the independent longitudinal association between weight change
and change in SDB severity.DesignPopulation-based, prospective cohort study conducted from July 1989
to January 2000.Setting and ParticipantsSix hundred ninety randomly selected employed Wisconsin residents (mean
age at baseline, 46 years; 56% male) who were evaluated twice at 4-year intervals
for SDB.Main Outcome MeasuresPercentage change in the apnea-hypopnea index (AHI; apnea events + hypopnea
events per hour of sleep) and odds of developing moderate-to-severe SDB (defined
by an AHI ≥15 events per hour of sleep), with respect to change in weight.ResultsRelative to stable weight, a 10% weight gain predicted an approximate
32% (95% confidence interval [CI], 20%-45%) increase in the AHI. A 10% weight
loss predicted a 26% (95% CI, 18%-34%) decrease in the AHI. A 10% increase
in weight predicted a 6-fold (95% CI, 2.2-17.0) increase in the odds of developing
moderate-to-severe SDB.ConclusionsOur data indicate that clinical and public health programs that result
in even modest weight control are likely to be effective in managing SDB and
reducing new occurrence of SDB.
1,655 citations
TL;DR: High-resolution transmission electron microscopy of biomineralization products of iron-oxidizing bacteria revealed an alternative coarsening mechanism in which adjacent 2- to 3-nanometer particles aggregate and rotate so their structures adopt parallel orientations in three dimensions.
Abstract: Crystals are generally considered to grow by attachment of ions to inorganic surfaces or organic templates. High-resolution transmission electron microscopy of biomineralization products of iron-oxidizing bacteria revealed an alternative coarsening mechanism in which adjacent 2- to 3-nanometer particles aggregate and rotate so their structures adopt parallel orientations in three dimensions. Crystal growth is accomplished by eliminating water molecules at interfaces and forming iron-oxygen bonds. Self-assembly occurs at multiple sites, leading to a coarser, polycrystalline material. Point defects (from surface-adsorbed impurities), dislocations, and slabs of structurally distinct material are created as a consequence of this growth mechanism and can dramatically impact subsequent reactivity.
1,620 citations
TL;DR: In this article, the authors argue that the polarization of individual interest, extrinsic and intrinsic motivation, and performance and mastery goals must be reconsidered, and they urge educators and researchers to recognize the potential additional benefits of externally triggered situational interest, intrinsic motivation and performance goals.
Abstract: Interests and goals have been identified as two important motivational variables that impact individuals' academic performances, yet little is known about how best to utilize these variables to enhance childrens' learning. We first review recent developments in the two areas and then examine the connection between interests and goals. We argue that the polarization of situational and individual interest, extrinsic and intrinsic motivation, and performance and mastery goals must be reconsidered. In addition, although we acknowledge the positive effects of individual interest, intrinsic motivation, and the adoption of mastery goals, we urge educators and researchers to recognize the potential additional benefits of externally triggered situational interest, extrinsic motivation, and performance goals. Only by dealing with the multidimensional nature of motivational forces will we be able to help our academically unmotivated children.
TL;DR: In the Southern Great Plains 1997 Hydrology Experiment, four different types of eddy-covariance systems were set up side-by-side and all of them under-measured sensible and latent heat fluxes by similar amounts.
TL;DR: Analysis of Period gene expression in the suprachiasmatic nucleus (SCN) indicates that these behavioral phenotypes arise from loss of circadian function at the molecular level, and provides genetic evidence that MOP3 is the bona fide heterodimeric partner of mCLOCK.
TL;DR: In this paper, the impact of particle size on phase stability and phase transformation during growth of nanocrystalline aggregates was investigated using titania (TiO2) samples consisting of anatase and brookite.
Abstract: To understand the impact of particle size on phase stability and phase transformation during growth of nanocrystalline aggregates we conducted experiments using titania (TiO2) samples consisting of nanocrystalline anatase (46.7 wt %, 5.1 nm) and brookite (53.3 wt %, 8.1 nm). Reactions were studied isochronally at reaction times of 2 h in the temperature range 598−1023 K and isothermally at 723, 853, and 973 K by X-ray diffraction (XRD). A numerical deconvolution method was developed to separate overlapping XRD peaks, and an analytical method for determining phase contents of anatase, brookite, and rutile from XRD data was established. Results show that, in contrast to previous studies, anatase in our samples transforms to brookite and/or rutile before brookite transforms to rutile. Thermodynamic and kinetic analyses further support this conclusion. For general titania samples, the transformation sequence among anatase and brookite depends on the initial particle sizes of anatase and brookite, since partic...
TL;DR: Biotechnological modifications of ethylene synthesis and of sensitivity to ethylene are promising methods to prevent spoilage of agricultural products such as fruits, whose ripening is induced by ethylene.
Abstract: ▪ Abstract Ethylene regulates a multitude of plant processes, ranging from seed germination to organ senescence. Of particular economic importance is the role of ethylene as an inducer of fruit rip...
TL;DR: In this paper, the authors review the original and emergent conceptualizations of opportunism and illustrate them using actual industry cases and develop a conceptual framework of governance strategies that can be used to manage different forms of opportunisms.
Abstract: Much of the recent literature on interfirm relationships has focused on strategies for controlling opportunism. Somewhat surprisingly, little attention has been paid in this literature to the opportunism construct itself. Specifically, prior research has failed to recognize the different types of behavior that are hidden behind the general opportunism label. As a consequence, the knowledge of strategies for managing opportunism remains incomplete. The authors review the original and emergent conceptualizations of opportunism and illustrate them using actual industry cases. The authors also develop a conceptual framework of governance strategies that can be used to manage different forms of opportunism.
TL;DR: Data indicate that GDNF delivery using a lentiviral vector system can prevent nigrostriatal degeneration and induce regeneration in primate models of PD and might be a viable therapeutic strategy for PD patients.
Abstract: Lentiviral delivery of glial cell line-derived neurotrophic factor (lenti-GDNF) was tested for its trophic effects upon degenerating nigrostriatal neurons in nonhuman primate models of Parkinson's disease (PD). We injected lenti-GDNF into the striatum and substantia nigra of nonlesioned aged rhesus monkeys or young adult rhesus monkeys treated 1 week prior with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Extensive GDNF expression with anterograde and retrograde transport was seen in all animals. In aged monkeys, lenti-GDNF augmented dopaminergic function. In MPTP-treated monkeys, lenti-GDNF reversed functional deficits and completely prevented nigrostriatal degeneration. Additionally, lenti-GDNF injections to intact rhesus monkeys revealed long-term gene expression (8 months). In MPTP-treated monkeys, lenti-GDNF treatment reversed motor deficits in a hand-reach task. These data indicate that GDNF delivery using a lentiviral vector system can prevent nigrostriatal degeneration and induce regeneration in primate models of PD and might be a viable therapeutic strategy for PD patients.
TL;DR: This review highlights the analysis of those protein‐protein interactions that involve proline residues, the biochemistry of proline, and current drug discovery efforts based on proline peptidomimetics.
Abstract: Acommon focus among molecular and cellular biologists is the identification of proteins that interact with each other. Yeast two-hybrid, cDNA expression library screening, and coimmunoprecipitation experiments are powerful methods for identifying novel proteins that bind to one's favorite protein for the purpose of learning more regarding its cellular function. These same techniques, coupled with truncation and mutagenesis experiments, have been used to define the region of interaction between pairs of proteins. One conclusion from this work is that many interactions occur over short regions, often less than 10 amino acids in length within one protein. For example, mapping studies and 3-dimensional analyses of antigen-antibody interactions have revealed that epitopes are typically 4-7 residues long (1). Other examples include protein-interaction modules, such as Src homology (SH) 2 and 3 domains, phosphotyrosine binding domains (PTB), postsynaptic density/disc-large/ZO1 (PDZ) domains, WW domains, Eps15 homology (EH) domains, and 14-3-3 proteins that typically recognize linear regions of 3-9 amino acids. Each of these domains has been the subject of recent reviews published elsewhere (2 3 4 5 6 7). Among the primary structures of many ligands for protein-protein interactions, the amino acid proline is critical. In particular, SH3, WW, and several new protein-interaction domains prefer ligand sequences that are proline-rich. In addition, even though ligands for EH domains and 14-3-3 domains are not proline-rich, they do include a single proline residue. This review highlights the analysis of those protein-protein interactions that involve proline residues, the biochemistry of proline, and current drug discovery efforts based on proline peptidomimetics.-Kay, B. K., Williamson, M. P., Sudol, M. The importance of being proline: the interaction of proline-rich motifs in signaling proteins with their cognate domains.
TL;DR: Phylogenetic analysis of 16S rRNA gene sequences recovered from one of the libraries indicates that the BAC libraries contain DNA from a wide diversity of microbial phyla, including sequences from diverse taxa such as the low-G+C, gram-positive Acidobacterium,Cytophagales, and Proteobacteria.
Abstract: Recent progress in molecular microbial ecology has revealed that traditional culturing methods fail to represent the scope of microbial diversity in nature, since only a small proportion of viable microorganisms in a sample are recovered by culturing techniques. To develop methods to investigate the full extent of microbial diversity, we used a bacterial artificial chromosome (BAC) vector to construct libraries of genomic DNA isolated directly from soil (termed metagenomic libraries). To date, we have constructed two such libraries, which contain more than 1 Gbp of DNA. Phylogenetic analysis of 16S rRNA gene sequences recovered from one of the libraries indicates that the BAC libraries contain DNA from a wide diversity of microbial phyla, including sequences from diverse taxa such as the low-G1C, gram-positive Acidobacterium, Cytophagales, and Proteobacteria. Initial screening of the libraries in Escherichia coli identified several clones that express heterologous genes from the inserts, confirming that the BAC vector can be used to maintain, express, and analyze environmental DNA. The phenotypes expressed by these clones include antibacterial, lipase, amylase, nuclease, and hemolytic activities. Metagenomic libraries are a powerful tool for exploring soil microbial diversity, providing access to the genetic information of uncultured soil microorganisms. Such libraries will be the basis of new initiatives to conduct genomic studies that link phylogenetic and functional information about the microbiota of environments dominated by microorganisms that are refractory to cultivation. The biosphere is dominated by microorganisms (32), yet most microbes in nature have not been studied. Traditional methods for culturing microorganisms limit analysis to those that grow under laboratory conditions (14, 25). The recent surge of research in molecular microbial ecology provides compelling evidence for the existence of many novel types of microorganisms in the environment in numbers and varieties that dwarf those of the comparatively few microorganisms amenable to laboratory cultivation (7, 13, 31). Corroboration comes from estimates of DNA complexity and the discovery of many unique 16S rRNA gene sequences from numerous environmental sources (8, 10, 28). Collectively, the genomes of the total microbiota found in nature, which we termed the metagenome (11), contain vastly more genetic information than is contained in the culturable subset. Given the profound utility and importance of microorganisms to all biological systems, methods are needed to access the wealth of information within the metagenome. Cloning large fragments of DNA isolated directly from microbes in natural environments provides a method to access soil metagenomic DNA. Previously, we investigated the use of the bacterial artificial chromosome (BAC) vector to express Bacillus cereus genomic DNA (20). The advantage of BAC vectors is that they maintain very large DNA inserts (greater than 100 kb) stably in Escherichia coli (23), facilitating the cloning of large fragments of DNA. Our results demonstrated that expression of heterologous DNA from B. cereus in an E. coli BAC system was detectable at a reasonable frequency (20), validating the idea that the low-copy BAC vector (one to two per cell) (23) could be used to express foreign DNA from foreign promoters in E. coli. Here we describe the construction and initial screening of two BAC libraries made with DNA isolated directly from soil. We found detectable levels of several biochemical activities from BAC library clones. Sequence analysis of selected BAC plasmids encoding such activities and of 16S rRNA genes in one of the libraries confirms the novelty of the genomic information cloned in our libraries. The results show that DNA extracted directly from soil is a valuable source of new genetic information and is accessible by using BAC libraries. Our results demonstrate that both traditional and functional genomics of uncultured microorganisms can be carried out by this approach and that screening of metagenome libraries for activities or gene sequences can provide a basis for conducting genomic analyses of uncultured microorganisms.
University of Wisconsin-Madison1, United States Geological Survey2, Virginia Tech3, Rissho University4, Great Lakes Institute of Management5, University of Colorado Boulder6, Florida State University College of Arts and Sciences7, Finnish Environment Institute8, National Water Research Institute9, University at Buffalo10, State Hydrological Institute11
TL;DR: Interannual variability in both freeze and breakup dates has increased since 1950 and a few longer time series reveal reduced ice cover (a warming trend) beginning as early as the 16th century, with increasing rates of change after about 1850.
Abstract: Freeze and breakup dates of ice on lakes and rivers provide consistent evidence of later freezing and earlier breakup around the Northern Hemisphere from 1846 to 1995. Over these 150 years, changes in freeze dates averaged 5.8 days per 100 years later, and changes in breakup dates averaged 6.5 days per 100 years earlier; these translate to increasing air temperatures of about 1.2°C per 100 years. Interannual variability in both freeze and breakup dates has increased since 1950. A few longer time series reveal reduced ice cover (a warming trend) beginning as early as the 16th century, with increasing rates of change after about 1850.
TL;DR: Among decision tree algorithms with univariate splits, C4.5, IND-CART, and QUEST have the best combinations of error rate and speed, but C 4.5 tends to produce trees with twice as many leaves as those fromIND-Cart and QUEST.
Abstract: Twenty-two decision tree, nine statistical, and two neural network algorithms are compared on thirty-two datasets in terms of classification accuracy, training time, and (in the case of trees) number of leaves. Classification accuracy is measured by mean error rate and mean rank of error rate. Both criteria place a statistical, spline-based, algorithm called POLYCLSSS at the top, although it is not statistically significantly different from twenty other algorithms. Another statistical algorithm, logistic regression, is second with respect to the two accuracy criteria. The most accurate decision tree algorithm is QUEST with linear splits, which ranks fourth and fifth, respectively. Although spline-based statistical algorithms tend to have good accuracy, they also require relatively long training times. POLYCLASS, for example, is third last in terms of median training time. It often requires hours of training compared to seconds for other algorithms. The QUEST and logistic regression algorithms are substantially faster. Among decision tree algorithms with univariate splits, C4.5, IND-CART, and QUEST have the best combinations of error rate and speed. But C4.5 tends to produce trees with twice as many leaves as those from IND-CART and QUEST.
16 May 2000
TL;DR: The design of NiagaraCQ system is presented, some experimental results on the system's performance and scalability are given and other techniques including incremental evaluation of continuous queries, use of both pull and push models for detecting heterogeneous data source changes, and memory caching are employed.
Abstract: Continuous queries are persistent queries that allow users to receive new results when they become available. While continuous query systems can transform a passive web into an active environment, they need to be able to support millions of queries due to the scale of the Internet. No existing systems have achieved this level of scalability. NiagaraCQ addresses this problem by grouping continuous queries based on the observation that many web queries share similar structures. Grouped queries can share the common computation, tend to fit in memory and can reduce the I/O cost significantly. Furthermore, grouping on selection predicates can eliminate a large number of unnecessary query invocations. Our grouping technique is distinguished from previous group optimization approaches in the following ways. First, we use an incremental group optimization strategy with dynamic re-grouping. New queries are added to existing query groups, without having to regroup already installed queries. Second, we use a query-split scheme that requires minimal changes to a general-purpose query engine. Third, NiagaraCQ groups both change-based and timer-based queries in a uniform way. To insure that NiagaraCQ is scalable, we have also employed other techniques including incremental evaluation of continuous queries, use of both pull and push models for detecting heterogeneous data source changes, and memory caching. This paper presents the design of NiagaraCQ system and gives some experimental results on the system's performance and scalability.
TL;DR: Several factors, such as smoking, caffeine use, and multivitamin use, could be studied for preventive or therapeutic efficacy in a population-based cohort to examine risk factors for the prevalence of dry eye syndrome.
Abstract: Objective To examine risk factors for the prevalence of dry eye syndrome in a population-based cohort. Methods The prevalence of dry eye was determined by history at the second examination (1993-1995) of the Beaver Dam Eye Study cohort (N = 3722). Results The cohort was aged 48 to 91 years (mean ± SD, 65 ± 10 years) and 43% male. The overall prevalence of dry eye was 14.4%. Prevalence varied from 8.4% in subjects younger than 60 years to 19.0% in those older than 80 years ( P P Conclusion The results suggest several factors, such as smoking, caffeine use, and multivitamin use, could be studied for preventive or therapeutic efficacy.
TL;DR: The concepts are introduced, a framework in which the critical issues can be expressed and analyzed are provided, and it is pointed out how MPC allows practitioners to address the trade-offs that must be considered in implementing a control technology.
Abstract: The paper provides a reasonably accessible and self-contained tutorial exposition on model predictive control (MPC). It is aimed at readers with control expertise, particularly practitioners, who wish to broaden their perspective in the MPC area of control technology. We introduce the concepts, provide a framework in which the critical issues can be expressed and analyzed, and point out how MPC allows practitioners to address the trade-offs that must be considered in implementing a control technology.
TL;DR: Caloric restriction, which retards the ageing process in mammals, selectively attenuated the age-associated induction of genes encoding inflammatory and stress responses, which resulted in a gene-expression profile indicative of an inflammatory response, oxidative stress and reduced neurotrophic support in both brain regions.
Abstract: Ageing of the brain leads to impairments in cognitive and motor skills, and is the major risk factor for several common neurological disorders such as Alzheimer disease (AD) and Parkinson disease (PD). Recent studies suggest that normal brain ageing is associated with subtle morphological and functional alterations in specific neuronal circuits, as opposed to large-scale neuronal loss1. In fact, ageing of the central nervous system in diverse mammalian species shares many features, such as atrophy of pyramidal neurons, synaptic atrophy, decrease of striatal dopamine receptors, accumulation of fluorescent pigments, cytoskeletal abnormalities, and reactive astrocytes and microglia2. To provide the first global analysis of brain ageing at the molecular level, we used oligonucleotide arrays representing 6,347 genes to determine the gene-expression profile of the ageing neocortex and cerebellum in mice. Ageing resulted in a gene-expression profile indicative of an inflammatory response, oxidative stress and reduced neurotrophic support in both brain regions. At the transcriptional level, brain ageing in mice displays parallels with human neurodegenerative disorders. Caloric restriction, which retards the ageing process in mammals, selectively attenuated the age-associated induction of genes encoding inflammatory and stress responses.
TL;DR: In this paper, a new power transformation family is introduced for reducing skewness and approximate normality. But the power transformation is not suitable for the real line. And the large-sample properties of the transformation are investigated in the contect of a single random sample.
Abstract: SUMMARY We introduce a new power transformation family which is well defined on the whole real line and which is appropriate for reducing skewness and to approximate normality. It has properties similar to those of the Box-Cox transformation for positive variables. The large-sample properties of the transformation are investigated in the contect of a single random sample.
TL;DR: Fossilized fungal hyphae and spores from the Ordovician of Wisconsin strongly resemble modern arbuscular mycorrhizal fungi (Glomales, Zygomycetes), indicating that Glomales-like fungi were present at a time when the land flora most likely only consisted of plants on the bryophytic level.
Abstract: Fossilized fungal hyphae and spores from the Ordovician of Wisconsin (with an age of about 460 million years) strongly resemble modern arbuscular mycorrhizal fungi (Glomales, Zygomycetes). These fossils indicate that Glomales-like fungi were present at a time when the land flora most likely only consisted of plants on the bryophytic level. Thus, these fungi may have played a crucial role in facilitating the colonization of land by plants, and the fossils support molecular estimates of fungal phylogeny that place the origin of the major groups of terrestrial fungi (Ascomycota, Basidiomycota, and Glomales) around 600 million years ago.
TL;DR: In this article, the authors examined a class of continuous-time models that incorporate jumps in returns and volatility, in addition to diffusive stochastic volatility, and developed a likelihood-based estimation strategy and provided estimates of model parameters, spot volatility, jump times and jump sizes using both S&P 500 and Nasdaq 100 index returns.
Abstract: This paper examines a class of continuous-time models that incorporate jumps in returns and volatility, in addition to diffusive stochastic volatility. We develop a likelihood-based estimation strategy and provide estimates of model parameters, spot volatility, jump times and jump sizes using both S&P 500 and Nasdaq 100 index returns. Estimates of jumps times, jump sizes and volatility are particularly useful for disentangling the dynamic effects of these factors during periods of market stress, such as those in 1987, 1997 and 1998. Using both formal and informal diagnostics, we find strong evidence for jumps in volatility, even after accounting for jumps in returns. We use implied volatility curves computed from option prices to judge the economic differences between the models. Finally, we evaluate the impact of estimation risk on option prices and find that the uncertainty in estimating the parameters and the spot volatility has important, though very different, effects on option prices.
TL;DR: It is demonstrated that PKA-dependent processing of vertebrate Gli3 in developing limb similarly generates a potent repressor in a manner antagonized by apparent long-range signaling from posteriorly localized Sonic hedgehog protein.
TL;DR: The bacterial SOS response to unusual levels of DNA damage has been recognized and studied for several decades, but pathways for re-establishing inactivated replication forks under normal growth conditions have received far less attention.
Abstract: The bacterial SOS response to unusual levels of DNA damage has been recognized and studied for several decades. Pathways for re-establishing inactivated replication forks under normal growth conditions have received far less attention. In bacteria growing aerobically in the absence of SOS-inducing conditions, many replication forks encounter DNA damage, leading to inactivation. The pathways for fork reactivation involve the homologous recombination systems, are nonmutagenic, and integrate almost every aspect of DNA metabolism. On a frequency-of-use basis, these pathways represent the main function of bacterial DNA recombination systems, as well as the main function of a number of other enzymatic systems that are associated with replication and site-specific recombination.