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71.
72.
MCLUST is a software package for model-based clustering, density estimation
and discriminant analysis interfaced to the S-PLUS commercial software and the R language.
It implements parameterized Gaussian hierarchical clustering algorithms and the
EM algorithm for parameterized Gaussian mixture models with the possible addition of a
Poisson noise term. Also included are functions that combine hierarchical clustering, EM
and the Bayesian Information Criterion (BIC) in comprehensive strategies for clustering,
density estimation, and discriminant analysis. MCLUST provides functionality for displaying
and visualizing clustering and classification results. A web page with related links can
be found at . 相似文献
73.
Chris Brooks 《Journal of forecasting》1998,17(1):59-80
This paper explores a number of statistical models for predicting the daily stock return volatility of an aggregate of all stocks traded on the NYSE. An application of linear and non-linear Granger causality tests highlights evidence of bidirectional causality, although the relationship is stronger from volatility to volume than the other way around. The out-of-sample forecasting performance of various linear, GARCH, EGARCH, GJR and neural network models of volatility are evaluated and compared. The models are also augmented by the addition of a measure of lagged volume to form more general ex-ante forecasting models. The results indicate that augmenting models of volatility with measures of lagged volume leads only to very modest improvements, if any, in forecasting performance. © 1998 John Wiley & Sons, Ltd. 相似文献
74.
Todd JA Walker NM Cooper JD Smyth DJ Downes K Plagnol V Bailey R Nejentsev S Field SF Payne F Lowe CE Szeszko JS Hafler JP Zeitels L Yang JH Vella A Nutland S Stevens HE Schuilenburg H Coleman G Maisuria M Meadows W Smink LJ Healy B Burren OS Lam AA Ovington NR Allen J Adlem E Leung HT Wallace C Howson JM Guja C Ionescu-Tîrgovişte C;Genetics of Type Diabetes in Finland Simmonds MJ Heward JM Gough SC;Wellcome Trust Case Control Consortium Dunger DB Wicker LS Clayton DG 《Nature genetics》2007,39(7):857-864
The Wellcome Trust Case Control Consortium (WTCCC) primary genome-wide association (GWA) scan on seven diseases, including the multifactorial autoimmune disease type 1 diabetes (T1D), shows associations at P < 5 x 10(-7) between T1D and six chromosome regions: 12q24, 12q13, 16p13, 18p11, 12p13 and 4q27. Here, we attempted to validate these and six other top findings in 4,000 individuals with T1D, 5,000 controls and 2,997 family trios independent of the WTCCC study. We confirmed unequivocally the associations of 12q24, 12q13, 16p13 and 18p11 (P(follow-up) 相似文献
75.
76.
Apolipoprotein-mediated pathways of lipid antigen presentation 总被引:1,自引:0,他引:1
van den Elzen P Garg S León L Brigl M Leadbetter EA Gumperz JE Dascher CC Cheng TY Sacks FM Illarionov PA Besra GS Kent SC Moody DB Brenner MB 《Nature》2005,437(7060):906-910
Peptide antigens are presented to T cells by major histocompatibility complex (MHC) molecules, with endogenous peptides presented by MHC class I and exogenous peptides presented by MHC class II. In contrast to the MHC system, CD1 molecules bind lipid antigens that are presented at the antigen-presenting cell (APC) surface to lipid antigen-reactive T cells. Because CD1 molecules survey endocytic compartments, it is self-evident that they encounter antigens from extracellular sources. However, the mechanisms of exogenous lipid antigen delivery to CD1-antigen-loading compartments are not known. Serum apolipoproteins are mediators of extracellular lipid transport for metabolic needs. Here we define the pathways mediating markedly efficient exogenous lipid antigen delivery by apolipoproteins to achieve T-cell activation. Apolipoprotein E binds lipid antigens and delivers them by receptor-mediated uptake into endosomal compartments containing CD1 in APCs. Apolipoprotein E mediates the presentation of serum-borne lipid antigens and can be secreted by APCs as a mechanism to survey the local environment to capture antigens or to transfer microbial lipids from infected cells to bystander APCs. Thus, the immune system has co-opted a component of lipid metabolism to develop immunological responses to lipid antigens. 相似文献
77.
Substance P (Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2) may be used as a neurotransmitter by certain primary afferent neurones, particularly those carrying pain impulses. Substance P-like immunoreactivity has been localised to the cell bodies of one population of dorsal root ganglion neurones by immunocytochemistry. It is contained in vesicles in the central terminals of these neurones, and has also been demonstrated in the peripheral terminals. As axons and terminals have very little capacity for peptide biosynthesis, it is possible that substance P is synthesised and packaged in the perikaryon and transported to the terminals by an axoplasmic transport process. Consistent with this is the finding that substance P accumulates proximal to a ligature placed on the dorsal root. There has, however, been no direct demonstration of the biosynthesis of substance P in the nervous system. We report here that rat dorsal root ganglia incorporate 35S-methionine into substance P, characterised as authentic by immunoprecipitation followed by HPLC. There is a delay of 1-2 h between addition of label and its incorporation into substance P. Synthesis is blocked by cycloheximde suggesting that, in dorsal root ganglia, substance P is synthesised by a conventional ribosomal process. Synthesis of substance P is reduced by some 90% in ganglia from rats treated neonatally with capsaicin, a drug which is thought to destroy a population of primary afferent neurones. 相似文献
78.
Shaw C 《Population trends》2002,(107):5-13
The 2000-based national population projections, carried out by the Government Actuary at the request of the Registrars General, show the population of the United Kingdom rising from 59.8 million in 2000 to nearly 65 million by 2025. Longer-term projections suggest the population will peak at nearly 66 million around 2040 and then gradually start to fall. The population will become gradually older with the median age expected to rise from 37.4 years in 2000 to 42.4 years by 2025. In 2000, there were 1.3 million (12 per cent) more children aged under 16, than people of state pensionable age. However, by 2007, the population of state pensionable age is projected to exceed the number of children. 相似文献
79.
Shaw C 《Population trends》2002,(109):15-26
Interest has been growing steadily in understanding the impact of the inherent uncertainty in the national population projections. As a result, the Government Acturay's Department has recently produced the most extensive set of official variant projections ever published in the United Kingdom. These include 'standard' variants based on alternative high and low assumptions for future fertility, life expectancy and net migration and also a number of 'special case scenarios.' All of these variants have been produced at both UK and individual country level. This article describes the full range of variant projections available from the 2000-based national projections and summaries some of the key results for both the UK and the individual countries. 相似文献
80.
Carlton JM Angiuoli SV Suh BB Kooij TW Pertea M Silva JC Ermolaeva MD Allen JE Selengut JD Koo HL Peterson JD Pop M Kosack DS Shumway MF Bidwell SL Shallom SJ van Aken SE Riedmuller SB Feldblyum TV Cho JK Quackenbush J Sedegah M Shoaibi A Cummings LM Florens L Yates JR Raine JD Sinden RE Harris MA Cunningham DA Preiser PR Bergman LW Vaidya AB van Lin LH Janse CJ Waters AP Smith HO White OR Salzberg SL Venter JC Fraser CM Hoffman SL Gardner MJ Carucci DJ 《Nature》2002,419(6906):512-519
Species of malaria parasite that infect rodents have long been used as models for malaria disease research. Here we report the whole-genome shotgun sequence of one species, Plasmodium yoelii yoelii, and comparative studies with the genome of the human malaria parasite Plasmodium falciparum clone 3D7. A synteny map of 2,212 P. y. yoelii contiguous DNA sequences (contigs) aligned to 14 P. falciparum chromosomes reveals marked conservation of gene synteny within the body of each chromosome. Of about 5,300 P. falciparum genes, more than 3,300 P. y. yoelii orthologues of predominantly metabolic function were identified. Over 800 copies of a variant antigen gene located in subtelomeric regions were found. This is the first genome sequence of a model eukaryotic parasite, and it provides insight into the use of such systems in the modelling of Plasmodium biology and disease. 相似文献