Home About us Contact
|
Home About us Contact | ||
|
|
||
Various Models (various + models)
Selected AbstractsRegistration of plant protection products in EPPO countries: current status and possible approaches to harmonizationEPPO BULLETIN, Issue 2 2001J. Rüegg A survey concerning registration of plant protection products was carried out in 41 EPPO member countries. Twenty six countries responded and results are summarized in three groups. Various models are discussed which seek to adapt product dosage to the crowns of fruit-tree crops. The tree row volume model (TRV) is favoured by the authors since it can adequately cope with the wide variability of orchards encountered across Europe. It is suggested that experimenters who carry out registration field trials should measure the height and width of the tree crowns and the distance between the tree rows to facilitate comparison of registration trials including residue data. [source] The utility of behavioral models and modules in molecular analyses of social behaviorGENES, BRAIN AND BEHAVIOR, Issue 3 2008Andrew B. Barron It is extremely difficult to trace the causal pathway relating gene products or molecular pathways to the expression of behavior. This is especially true for social behavior, which being dependent on interactions and communication between individuals is even further removed from molecular-level events. In this review, we discuss how behavioral models can aid molecular analyses of social behavior. Various models of behavior exist, each of which suggest strategies to dissect complex behavior into simpler behavioral ,modules.' The resulting modules are easier to relate to neural processes and thus suggest hypotheses for neural and molecular function. Here we discuss how three different models of behavior have facilitated understanding the molecular bases of aspects of social behavior. We discuss the response threshold model and two different approaches to modeling motivation, the state space model and models of reinforcement and reward processing. The examples we have chosen illustrate how models can generate testable hypotheses for neural and molecular function and also how molecular analyses probe the validity of a model of behavior. We do not champion one model over another; rather, our examples illustrate how modeling and molecular analyses can be synergistic in exploring the molecular bases of social behavior. [source] Genes, chromosomes and the development of testicular germ cell tumors of adolescents and adultsGENES, CHROMOSOMES AND CANCER, Issue 7 2008Alan McIntyre Testicular germ cell tumors (TGCTs) of adults and adolescents are thought to be derived from primordial germ cells or gonocytes. TGCTs develop postpuberty from precursor lesions known as intratubular germ cell neoplasia undifferentiated. The tumors can be divided into two groups based on their histology and clinical behavior; seminomas resemble primordial germ cells or gonocytes and nonseminomas resemble embryonic or extraembryonic tissues at various stages of differentiation. The most undifferentiated form of nonseminoma, embryonal carcinoma, resembles embryonic stem cells in terms of morphology and expression profiling, both mRNAs and microRNAs. Evidence supports both environmental factors and genetic predisposition underlying the development of TGCTs. Various models of development have been proposed and are discussed. In TGCTs, gain of material from the short arm of chromosome 12 is invariable: genes from this region include the proto-oncogene KRAS, which has activating mutations in ,10% of tumors or is frequently overexpressed. A number of different approaches to increase the understanding of the development and progression of TGCTs have highlighted the involvement of KIT, RAS/RAF/MAPK, STAT, and PI3K/AKT signaling. We review the role of these signaling pathways in this process and the potential influence of environmental factors in the development of TGCTs. © 2008 Wiley-Liss, Inc. [source] Effectiveness of brief structured interventions on risk factor modification for patients with coronary heart disease: a systematic reviewINTERNATIONAL JOURNAL OF EVIDENCE BASED HEALTHCARE, Issue 4 2007Ritin Fernandez RN MN (Critical care) PhD Candidate Abstract Background, The physical and psychosocial benefits of participation in cardiac rehabilitation following a coronary event have well been established. Despite these benefits there is strong evidence that participation in traditional cardiac rehabilitation programs remains low. Various models of cardiac rehabilitation have been implemented including the use of brief structured interventions to enable modification of coronary risk factors. Objectives, The objective of this review was to determine the effect of brief structured interventions on risk factor modification in patients with coronary heart disease. Search strategy, A literature search was performed using the following databases MEDLINE (1966,2006), CINAHL (1982,2006), EMBASE (1980,current) and up to the Cochrane Controlled Trials Register (Issue 2, 2006 of Cochrane Library). In addition, the reference lists of relevant trials and conference proceedings were also scrutinised. Company representatives, experts and investigators were contacted to elicit further information. Selection criteria, All randomised and quasi-randomised controlled trials that compared the effects of brief structured interventions on risk factor modification in patients with coronary heart disease were considered for inclusion in the review. Data collection and analysis, Eligibility of the trials for inclusion in the review, details of eligible trials and the methodological quality of the trials were assessed independently by two reviewers. Relative risks for dichotomous data and a weighted mean difference for continuous data were calculated with 95% confidence intervals. Where synthesis was inappropriate, trials were considered separately. Main results, Seventeen trials involving a total of 4725 participants were included in the final review: three trials compared the effects of brief structured interventions on diet modification; seven on smoking cessation; and seven on multiple risk factors. Two trials involving 76 patients compared brief structured intervention versus usual care for dietary modification. Although there was a tendency for more participants in the intervention arm to lose weight at the 12-week follow up and achieve target cholesterol levels at the 6-month follow up, these results were not statistically significant. Only one small trial involving 36 patients compared brief structured intervention and extensive intervention for dietary modification and demonstrated a significant reduction in the percentage of energy obtained from fat and saturated fat intake among participants receiving extensive intervention. However, no difference in fish, fruit and vegetable intake between the groups was evident. Six trials involving 2020 patients compared brief structured intervention versus usual care for smoking cessation. There was no difference in the smoking cessation rates at the 3- and 6-week follow up, however, there was evidence of a benefit of brief structured interventions for smoking cessation at the 3-, 6- and 12-month follow up. In the only trial that and compared brief structured intervention and extensive intervention for smoking cessation in 254 participants there was no clear difference of a likelihood of smoking cessation between the two groups. In the seven trials that compared brief structured intervention and usual care for multiple risk factor modification there was evidence of a benefit of the intervention on behavioural changes such as fat intake, weight loss and consequently on reduction in the body mass index, smoking cessation and physical activity among the participants. The findings concerning the effect on blood pressure, blood glucose levels and the lipid profile, however, remain inconclusive. Conclusions, There is suggestive but inconclusive evidence from the trials of a benefit in the use of brief interventions for risk factor modification in patients with coronary heart disease. This review, however, supports the concept that brief interventions for patients with coronary heart disease can have beneficial effects on risk factor modification and consequently on progression of coronary heart disease. Further trials using larger sample sizes need to be undertaken to demonstrate the benefits of brief structured intervention targeted at the modification of single or multiple risk factors. [source] Statistical methods for regular monitoring dataJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 5 2005Michael L. Stein Summary., Meteorological and environmental data that are collected at regular time intervals on a fixed monitoring network can be usefully studied combining ideas from multiple time series and spatial statistics, particularly when there are little or no missing data. This work investigates methods for modelling such data and ways of approximating the associated likelihood functions. Models for processes on the sphere crossed with time are emphasized, especially models that are not fully symmetric in space,time. Two approaches to obtaining such models are described. The first is to consider a rotated version of fully symmetric models for which we have explicit expressions for the covariance function. The second is based on a representation of space,time covariance functions that is spectral in just the time domain and is shown to lead to natural partially nonparametric asymmetric models on the sphere crossed with time. Various models are applied to a data set of daily winds at 11 sites in Ireland over 18 years. Spectral and space,time domain diagnostic procedures are used to assess the quality of the fits. The spectral-in-time modelling approach is shown to yield a good fit to many properties of the data and can be applied in a routine fashion relative to finding elaborate parametric models that describe the space,time dependences of the data about as well. [source] A review of evaluation outcomes of web-based continuing medical educationMEDICAL EDUCATION, Issue 6 2005Vernon R Curran Introduction, The Internet and worldwide web have expanded opportunities for the provision of a flexible, convenient and interactive form of continuing medical education (CME). Larger numbers of doctors are accessing and using the Internet to locate and seek medical information. It has been suggested that a significant proportion of this usage is directly related to questions that arise from patient care. A variety of Internet technologies are being used to provide both asynchronous and synchronous forms of web-based CME. Various models for designing and facilitating web-based CME learning have also been reported. The purpose of this study was to examine the nature and characteristics of the web-based CME evaluative outcomes reported in the peer-reviewed literature. Methods, A search of Medline was undertaken and the level of evaluative outcomes reported was categorised using Kirkpatrick's model for levels of summative evaluation. Results, The results of this analysis revealed that the majority of evaluative research on web-based CME is based on participant satisfaction data. There was limited research demonstrating performance change in clinical practices and there were no studies reported in the literature that demonstrated that web-based CME was effective in influencing patient or health outcomes. Discussion, The findings suggest an important need to examine in greater detail the nature and characteristics of those web-based learning technologies, environments and systems which are most effective in enhancing practice change and ultimately impacting patient and health outcomes. This is particularly important as the Internet grows in popularity as a medium for knowledge transfer. [source] The dynamics of factors affecting the adoption of innovationsTHE JOURNAL OF PRODUCT INNOVATION MANAGEMENT, Issue 6 2002Eric Waarts An abundance of IT innovations are constantly struggling for market acceptance. Various models have been proposed in the literature in order to aid understanding of the principles behind the adoption of IT innovations, but most of them implicitly assume that the factors explaining adoption decisions do not change over time. This study challenges that assumption and adds to the existing literature by investigating the dynamics of the factors influencing adoption. Our general proposition is that the driving factors in adopting innovations will change as the diffusion of the innovation in the market progresses. A large-scale empirical study was carried out among medium-sized companies in a variety of European countries and industries concerning the adoption of enterprise resource planning (ERP) software. The findings strongly indicate that the factors affecting late adoption of ERP differ significantly from the factors explaining early adoption. At early stages of the diffusion process adoption tends to be especially driven by a combination of internal strategic drives and attitudes of the firm together with external forces like industry competition and supplier activities. Later on, the mix of adoption stimulating factors seems to be focusing more on implementation issues such as the scalability of the system, the number of seats and the yearly available budget. The study leads to both new methodological insights and substantive conclusions that also have practical implications. [source] Laboratory Forum: Cavernous Nerve Injury Using Rodent Animal ModelsTHE JOURNAL OF SEXUAL MEDICINE, Issue 8 2008Onder Canguven ABSTRACT Introduction., With the advance of the "nerve sparing" technique in radical pelvic surgeries, medically unaided rates of normal erectile function following surgery have improved. Precise determinations of post-surgery erection recovery, however, continue to be problematic and rates of normal erectile function range from 9% to 86%. It is understood that injury to cavernous nerves (CNs) occurs despite modern modifications of the surgery, although the precise pathophysiologic mechanisms of surgical erectile dysfunction are not completely understood. Aim., To describe the experimental models of CN injury in small rodents, including both survival surgery (CN injury) and non-survival surgery (monitoring of intracavernosal pressure and arterial blood pressure) models. We also summarize studies on experimental procedures relating to these CN injury models and critique techniques according to their advantages and disadvantages. Main Outcome Measure., Data from a peer review literature search on the topic of CN injury in rodent models. Methods., A comprehensive review of the literature was performed using PubMed. "Cavernous nerve injury" and "animal model" were used as search terms, and a manual bibliographic review of cross-referenced items was performed. Results., Assorted molecular, morphological, and physiological changes are measurable after CN injury in rodent models. Conclusion., Various models of CN injury have been applied successfully and offer insights regarding erectile function recovery effects. Canguven O, and Burnett A. Cavernous nerve injury using rodent animal models. J Sex Med 2008;5:1776,1785. [source] Breaking the left,right axis: do nodal parcels pass a signal to the left?BIOESSAYS, Issue 10 2005Dominic Norris In mammals, left,right symmetry is broken by a mechanically driven leftward flow of liquid at the embryonic node (nodal flow). Various models have emerged explaining how this may happen. Work from Tanaka and colleagues1 has provided a new mechanism by which nodal flow may be breaking symmetry. They describe small membrane-bound particles, which they term nodal vesicular parcels (NVPs), that are carried to the left side of the node. In the paper, they argue how signals carried within these parcels may break L,R symmetry. BioEssays 27:991,994, 2005. © 2005 Wiley Periodicals, Inc. [source] A unified model of sigmoid tumour growth based on cell proliferation and quiescenceCELL PROLIFERATION, Issue 6 2007F. Kozusko Objectives: A class of sigmoid functions designated generalized von Bertalanffy, Gompertzian and generalized Logistic has been used to fit tumour growth data. Various models have been proposed to explain the biological significance and foundations of these functions. However, no model has been found to fully explain all three or the relationships between them. Materials and Methods: We propose a simple cancer cell population dynamics model that provides a biological interpretation for these sigmoids' ability to represent tumour growth. Results and Conclusions: We show that the three sigmoids can be derived from the model and are in fact a single solution subject to the continuous variation of parameters describing the decay of the proliferation fraction and/or cell quiescence. We use the model to generate proliferation fraction profiles for each sigmoid and comment on the significance of the differences relative to cell cycle-specific and non-cell cycle-specific therapies. [source] Income Variance Dynamics and HeterogeneityECONOMETRICA, Issue 1 2004Costas Meghir Recent theoretical work has shown the importance of measuring microeconomic uncertainty for models of both general and partial equilibrium under imperfect insurance. In this paper the assumption of i.i.d. income innovations used in previous empirical studies is removed and the focus of the analysis is placed on models for the conditional variance of income shocks, which is related to the measure of risk emphasized by the theory. We first discriminate amongst various models of earnings determination that separate income shocks into idiosyncratic transitory and permanent components. We allow for education- and time-specific differences in the stochastic process for earnings and for measurement error. The conditional variance of the income shocks is modelled as a parsimonious ARCH process with both observable and unobserved heterogeneity. The empirical analysis is conducted on data drawn from the 1967,1992 Panel Study of Income Dynamics. We find strong evidence of sizeable ARCH effects as well as evidence of unobserved heterogeneity in the variances. [source] Pimecrolimus , an anti-inflammatory drug targeting the skinEXPERIMENTAL DERMATOLOGY, Issue 12 2004M. Grassberger Abstract:, Pimecrolimus is the most recent member of calcineurin inhibitors available for the therapy for inflammatory skin diseases. It targets T-cells and mast cells and inhibits the production and release of cytokines and other inflammatory mediators, as well as the expression of signals essential for the activation of inflammatory T-lymphocytes. Pimecrolimus has a cell-selective mode of action. In contrast to corticosteroids, it does not affect, e.g., Langerhans'cells/dendritic cells (LC/DC), as demonstrated in vitro with human monocyte-derived DC and in vivo with epidermal LC in mice, nor human primary fibroblasts. As shown in vitro with human skin and by comparison of clinical pharmacokinetic data from patients with atopic dermatitis, pimecrolimus permeates less through skin than tacrolimus and much less than corticosteroids. It, thus, has a lower potential for transcutaneous resorption after topical administration, resulting in a lower risk of systemic effects. Pimecrolimus has high anti-inflammatory activity in animal models of skin inflammation, including a model reflecting neurogenic inflammation, but a more favourable balance of anti-inflammatory vs. immunosuppressive activity than tacrolimus. Pimecrolimus does not affect sensitization in a murine model of allergic contact dermatitis and has a lower potency in various models of immunosuppression after systemic administration, compared to tacrolimus. In conclusion, the results of preclinical studies show that pimecrolimus has a selective pharmacological profile, suited for effective and safe treatment for inflammatory skin diseases. [source] An investigation into time domain Doppler modelling using the TLM numerical methodINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2007I. J. G. Scott Abstract The effects observed by a moving source and stationary receiver, or conversely stationary source and moving receiver are well known to physicists. The Doppler effect as it is commonly known is recognized as a perceived change in frequency of the incident signal upon the receiver, caused by the motion of either the source or receiver with respect to the stationary component, occurring in both electromagnetic (transverse) and acoustic (longitudinal) waves. This paper will primarily focus on the acoustic Doppler effect in the time domain, simulating a variety of scenarios using transmission line matrix (TLM) modelling in which the effect can be observed, proceeding to compare the accuracy of the various models generated. A new technique to allow arbitrary placement of boundaries of a TLM mesh will also be introduced and analysed allowing accurate placement of the moving walls within the simulation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Evidence-based practice and health visiting: the need for theoretical underpinnings for evaluationJOURNAL OF ADVANCED NURSING, Issue 6 2000Ruth Elkan BA(Hons) Evidence-based practice and health visiting: the need for theoretical underpinnings for evaluation In this paper we argue that evidence-based practice, which is being introduced throughout the British National Health Service to make decisions about the allocation of limited resources, provides a welcome opportunity for health visitors to demonstrate their efficacy, skills and professionalism. However, the paper argues that to view health visiting as evidence-based is not to reduce health visiting merely to a technology through which scientific solutions are applied to social problems. Rather, health visiting needs to be viewed as a political movement, based on a particular model of society, which shapes the goals which health visitors pursue and influences the strategies they adopt to achieve their goals. The paper describes various models of health visiting as a way of showing how the goals of health visiting are always framed within a particular set of assumptions and causal explanations. The paper then turns to look at the issue of evaluating health visiting services. It is argued that evaluation should properly take account of the models which shape health visitors' goals and intervention strategies, and in turn, health visitors need to be explicit about the theoretical frameworks underpinning their interventions. Finally, it is argued that health visitors' knowledge and understanding of a range of models of society enables them to move between the various models to choose the most appropriate and effective means of intervention. Hence it is concluded that the emphasis on evidence-based practice provides health visitors with a valuable opportunity to show that their unique, professional skills and understanding are the preconditions for effective intervention. [source] NF- ,B in liver diseases: a target for drug therapyJOURNAL OF APPLIED TOXICOLOGY, Issue 2 2009Pablo Muriel Abstract There are five nuclear factor- ,B (NF- ,B) transcription factors with important roles in innate immunity, liver inflammation, fibrosis and apoptosis prevention. Several inhibitors of NF- ,B, like caffeic acid, captopril, curcumin, pyrrolidine dithiocarbamate, resveratrol, silymarin and thalidomide, have demonstrated antinecrotic, anticholestatic, antifibrotic and anticancer activities in the liver. A link between inflammation and hepatocellular carcinoma through the NF- ,B pathway has been observed, providing ample experimental support for the tumor-promoting function of NF- ,B in various models of cancer. NF- ,B has been associated with the induction of proinflammatory gene expression and has attracted interest as a target for the treatment of inflammatory disease. However, despite much attention being focused on the deleterious effects of NF- ,B, activation of this factor during the resolution of inflammation is associated with the production of antiinflammatory molecules like interleukin (IL)-10 and the onset of apoptosis. This suggests that NF- ,B has an antiinflammatory role in vivo involving the regulation of the resolution of inflammation. Also, NF- ,B promotes liver regeneration by upregulating IL-6 and other molecules like hepatocyte growth factor. It has been postulated that the beneficial properties of NF- ,B are due to p50 homodimers, whose activation prevents cholestatic and chronic liver injury. More basic understanding on the function of the diverse NF- ,B factors is urgently needed in different physiological and pathological conditions, because depending on the subunit composition of the dimmer, the disease and the stage of the illness, inhibition of the factor may result in a beneficial or in a deleterious response. Copyright © 2008 John Wiley & Sons, Ltd. [source] Consequences of altered eicosanoid patterns for nociceptive processing in mPGES-1-deficient miceJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 2 2008Christian Brenneis Abstract Cyclooxygenase-2 (COX-2)-dependent prostaglandin (PG) E2 synthesis in the spinal cord plays a major role in the development of inflammatory hyperalgesia and allodynia. Microsomal PGE2 synthase-1 (mPGES-1) isomerizes COX-2-derived PGH2 to PGE2. Here, we evaluated the effect of mPGES-1-deficiency on the noci-ceptive behavior in various models of nociception that depend on PGE2 synthesis. Surprisingly, in the COX-2-dependent zymosan-evoked hyperalgesia model, the nociceptive behavior was not reduced in mPGES-1-deficient mice despite a marked decrease of the spinal PGE2 synthesis. Similarly, the nociceptive behavior was unaltered in mPGES-1-deficient mice in the formalin test. Importantly, spinal cords and primary spinal cord cells derived from mPGES-1-deficient mice showed a redirection of the PGE2 synthesis to PGD2, PGF2, and 6-keto-PGF1, (stable metabolite of PGI2). Since the latter prostaglandins serve also as mediators of noci-ception they may compensate the loss of PGE2 synthesis in mPGES-1-deficient mice. [source] The burgeoning field of statistical phylogeographyJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2004L. L. Knowles Abstract In the newly emerging field of statistical phylogeography, consideration of the stochastic nature of genetic processes and explicit reference to theoretical expectations under various models has dramatically transformed how historical processes are studied. Rather than being restricted to ad hoc explanations for observed patterns of genetic variation, assessments about the underlying evolutionary processes are now based on statistical tests of various hypotheses, as well as estimates of the parameters specified by the models. A wide range of demographical and biogeographical processes can be accommodated by these new analytical approaches, providing biologically more realistic models. Because of these advances, statistical phylogeography can provide unprecedented insights about a species' history, including decisive information about the factors that shape patterns of genetic variation, species distributions, and speciation. However, to improve our understanding of such processes, a critical examination and appreciation of the inherent difficulties of historical inference and challenges specific to testing phylogeographical hypotheses are essential. As the field of statistical phylogeography continues to take shape many difficulties have been resolved. Nonetheless, careful attention to the complexities of testing historical hypotheses and further theoretical developments are essential to improving the accuracy of our conclusions about a species' history. [source] Bananas and petrol: further evidence on the forecasting accuracy of the ABS ,headline' and ,underlying' rates of inflationJOURNAL OF FORECASTING, Issue 6 2010Liam J. A. Lenten Abstract In the light of the still topical nature of ,bananas and petrol' being blamed for driving much of the inflationary pressures in Australia in recent times, the ,headline' and ,underlying' rates of inflation are scrutinised in terms of forecasting accuracy. A general structural time-series modelling strategy is applied to estimate models for alternative types of Consumer Price Index (CPI) measures. From this, out-of-sample forecasts are generated from the various models. The underlying forecasts are subsequently adjusted to facilitate comparison. The Ashley, Granger and Schmalensee (1980) test is then performed to determine whether there is a statistically significant difference between the root mean square errors of the models. The results lend weight to the recent findings of Song (2005) that forecasting models using underlying rates are not systematically inferior to those based on the headline rate. In fact, strong evidence is found that underlying measures produce superior forecasts. Copyright © 2009 John Wiley & Sons, Ltd. [source] AN EVALUATION OF THE AVAILABLE TECHNIQUES FOR ESTIMATING MISSING FECAL COLIFORM DATA,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2004Ashu Jain ABSTRACT: This paper presents the findings of a study aimed at evaluating the available techniques for estimating missing fecal coliform (FC) data on a temporal basis. The techniques investigated include: linear and nonlinear regression analysis and interpolation functions, and the use of artificial neural networks (ANNs). In all, seven interpolation, two regression, and one ANN model structures were investigated. This paper also investigates the validity of a hypothesis that estimating missing FC data by developing different models using different data corresponding to different dynamics associated with different trends in the FC data may result in a better model performance. The FC data (counts/100 ml) derived from the North Fork of the Kentucky River in Kentucky were employed to calibrate and validate various models. The performance of various models was evaluated using a wide variety of standard statistical measures. The results obtained in this study are able to demonstrate that the ANNs can be preferred over the conventional techniques in estimating missing FC data in a watershed. The regression technique was not found suitable in estimating missing FC data on a temporal basis. Further, it has been found that it is possible to achieve a better model performance by first decomposing the whole data set into different categories corresponding to different dynamics and then developing separate models for separate categories rather than developing a single model for the composite data set. [source] Joint projections of temperature and precipitation change from multiple climate models: a hierarchical Bayesian approachJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2009Claudia Tebaldi Summary., Posterior distributions for the joint projections of future temperature and precipitation trends and changes are derived by applying a Bayesian hierachical model to a rich data set of simulated climate from general circulation models. The simulations that are analysed here constitute the future projections on which the Intergovernmental Panel on Climate Change based its recent summary report on the future of our planet's climate, albeit without any sophisticated statistical handling of the data. Here we quantify the uncertainty that is represented by the variable results of the various models and their limited ability to represent the observed climate both at global and at regional scales. We do so in a Bayesian framework, by estimating posterior distributions of the climate change signals in terms of trends or differences between future and current periods, and we fully characterize the uncertain nature of a suite of other parameters, like biases, correlation terms and model-specific precisions. Besides presenting our results in terms of posterior distributions of the climate signals, we offer as an alternative representation of the uncertainties in climate change projections the use of the posterior predictive distribution of a new model's projections. The results from our analysis can find straightforward applications in impact studies, which necessitate not only best guesses but also a full representation of the uncertainty in climate change projections. For water resource and crop models, for example, it is vital to use joint projections of temperature and precipitation to represent the characteristics of future climate best, and our statistical analysis delivers just that. [source] Cross-validation Criteria for Setar Model SelectionJOURNAL OF TIME SERIES ANALYSIS, Issue 3 2001Jan G. De Gooijer Three cross-validation criteria, denoted by respectively C, Cc, and Cu, are proposed for selecting the orders of a self-exciting threshold autoregressive (SETAR) model when both the delay and the threshold value are unknown. The derivation of C is within a natural cross-validation framework. The criterion Cc is similar in spirit as AICc, a bias-corrected version of AIC for SETAR model selection introduced by Wong and Li (1998). The criterion Cu is a variant of Cc having a similar poperty as AICu, a model selection proposed by McQuarrie et al. (1997) for linear models. In a Monte Carlo study, the performance of each of the criteria C, Cc, Cu, AIC, AICc, AICu, and BIC is investigated in detail for various models and various sample sizes. It will be shown that Cu consistently outperforms all other criteria when the sample size is moderate to large. [source] Investigation of structure and dynamics in the sodium metallocenes CpNa and CpNa·THF via solid-state NMR, X-ray diffraction and computational modellingMAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2007Cory M. Widdifield Abstract Solid-state 23Na NMR spectra of two organometallic complexes, cyclopentadienylsodium (CpNa) and the tetrahydrofuran (THF) solvate of CpNa (CpNa·THF), are presented. Analytical simulations of experimental spectra and calculated 23Na electric-field gradient (EFG) tensors confirm that both complexes are present in microcrystalline samples of CpNa recrystallized from THF. For the solvate, 23Na NMR experiments at 9.4 T and 11.7 T elucidate sodium chemical shielding (CS) tensor parameters, and establish that the EFG and CS tensor frames are non-coincident. Single-crystal X-ray diffraction (XRD) experiments are used to determine the crystal structure of CpNa·THF: Cmca (a = 9.3242(15) Å, b = 20.611(3) Å, c = 9.8236(14) Å, , = , = , = 90° , V = 1887.9(5)Å3, Z = 8). For CpNa, 23Na NMR data acquired at multiple field strengths establish sodium CS tensor parameters more precisely than in previous reports. Variable-temperature (VT) powder XRD (pXRD) experiments determine the temperature dependence of the CpNa unit cell parameters. The combination of 23Na quadrupolar NMR parameters, pXRD data and calculations of 23Na EFG tensors is used to examine various models of dynamic motion in the solid state. It is proposed that the sodium atom in CpNa undergoes an anisotropic, temperature-dependent, low frequency motion within the ab crystallographic plane, in contrast with previous models. Copyright © 2007 John Wiley & Sons, Ltd. [source] Monitoring the non-specific interactions of catechin through diffusion measurements based on pulsed-field gradientsMAGNETIC RESONANCE IN CHEMISTRY, Issue 13 2002C. Monteiro Abstract The self-association of aqueous catechin as a function of concentration was monitored through variations in 1H chemical shifts, proton T1 and T2 data and translational diffusion coefficients obtained with the pulsed-field gradient spin-echo method. The latter approach is very efficient and it is not restricted to aromatic compounds. Equilibrium constants were estimated for various models of self-association and the apparent enthalpy of dissociation was measured with isothermal titration calorimetry. Comparison of the latter parameter with thermodynamic data reported for various types of non-specific interactions suggests that such phenomena could be studied using this approach. Copyright © 2002 John Wiley & Sons, Ltd. [source] Curcumin and its analogues: Potential anticancer agentsMEDICINAL RESEARCH REVIEWS, Issue 5 2010Dinesh Kumar Agrawal Abstract This review chronicles the exploration of the curcumin in terms of development of analogues for the anticancer activity over the last century. Curcumin is a natural phytochemical obtained from dried root and rhizome of Turmeric (Curcuma Longa). It has been shown to interfere with multiple cell signaling pathways, including apoptosis (activation of caspases and downregulation of antiapoptotic gene products), proliferation (HER-2, EGFR, and AP-1), angiogenesis (VEGF), and inflammation (NF-,B, TNF, IL-6, IL-1, COX-2, and 5-LOX). In the last decade it has been much explored and various synthetic analogues have been prepared and evaluated for various pharmacological activities. Most of the analogues have shown very good anticancer activity in various models and various cell lines. However, some analogues have also shown antioxidant, anti-HIV, antimutagenic, antiangiogenic, antimalarial, antitubercular, antiandrogenic, COX inhibitory activities. Few analogues have shown very potent results and may be considered as clinical candidates for the development of future anticancer agent. This review contains 728 curcumin analogues and covers the literature from 1815 to mid 2009 and 93 references are cited. © 2009 Wiley Periodicals, Inc. Med Res Rev, 30, No. 5, 818,860, 2010 [source] Microvascular Thrombosis Models in Venules and Arterioles In VivoMICROCIRCULATION, Issue 3 2005ROLANDO E. RUMBAUT MD ABSTRACT Platelets are intimately involved in hemostasis and thrombosis. Under physiological conditions, circulating platelets do not interact with microvascular walls. However, in response to microvascular injury, platelet adhesion and subsequent thrombus formation may be observed in venules and arterioles in vivo. Numerous intravital video microscopy techniques have been described to induce and monitor the formation of microvascular thrombi. The mechanisms of microvascular injury vary widely among different models. Some models induce platelet activation with minimal effects on endothelium, others induce endothelial inflammation or injury, while other models lead to thrombus formation associated with endothelial denudation. The molecular mechanisms mediating platelet,vessel wall adhesive interactions differ among various models. In some instances, differences in responses between venules and arterioles are described that cannot be explained solely by hemodynamic factors. Several models for induction of microvascular thrombosis in vivo are outlined in this review, with a focus on the mechanisms of injury and thrombus formation, as well as on differences in responses between venules and arterioles. Recognizing these characteristics should help investigators select an appropriate model for studying microvascular thrombosis in vivo. [source] Experimental Models To Investigate Inflammatory Processes in Chronic Venous InsufficiencyMICROCIRCULATION, Issue S1 2000RONALD J. KORTHUIS ABSTRACT Chronic venous insufficiency (CVI) is characterized by leukocyte adhesion and infiltration, venous hypertension and dilatation, and valvular dysfunction. The fact that activated white cells can direct a powerful cytotoxic arsenal at parenchymal cells following their extravasation into the tissues led to the original proposal that leukocytes may play a causative role in the pathogenesis of venous disease. A large body of subsequent work indicates that white blood cells are indeed activated in CVI. However, identification of the factors responsible for initiating leukosequestration and activation in such disorders and determination of whether these activated cells then contribute to the progression of venous disease have been hampered by the lack of appropriate animal models that accurately mimic the human condition. Tantalizing evidence suggesting that cyclical periods of ischemia and reperfusion (I/R) may occur in diseased regions of the skin is beginning to accumulate. As is the case with CVI, leukocyte infiltration is a prominent feature in I/R and activated neutrophils play a causative role in the reperfusion component of tissue injury via the targeted release of reactive oxygen metabolites and hydrolytic enzymes. In light of these considerations, many investigators have suggested that examining the mechanisms of I/R injury in skin and skeletal muscle, where ischemia is produced by arterial occlusion, may provide a relevant model for studying the pathogenesis of CVI. Others have suggested that venous occlusion may represent a more appropriate model, as this approach also produces the venous hypertension that is characteristic of the disease. The purpose of this review is to summarize the evidence pointing to the involvement of I/R and venous hypertension as causative factors in CVI-induced leukocyte recruitment. In addition, we will describe the evidence in favor of the view that white blood cells contribute to the pathogenesis of CVI. Finally, we will describe several different experimental models that have been used to examine the role of I/R-induced microvascular dysfunction as it may pertain to the development of CVI, together with a discussion of the relative advantages and limitations of the various models. [source] Scale-dependent galaxy bias in the Sloan Digital Sky Survey as a function of luminosity and colourMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009James G. Cresswell ABSTRACT It has been known for a long time that the clustering of galaxies changes as a function of galaxy type. This galaxy bias acts as a hindrance to the extraction of cosmological information from the galaxy power spectrum or correlation function. Theoretical arguments show that a change in the amplitude of the clustering between galaxies and mass on large scales is unavoidable, but cosmological information can be easily extracted from the shape of the power spectrum or correlation function if this bias is independent of scale. Scale-dependent bias is generally small on large scales, k < 0.1 h Mpc,1, but on smaller scales can affect the recovery of ,mh from the measured shape of the clustering signal, and have a small effect on the Baryon Acoustic Oscillations. In this paper, we investigate the transition from scale-independent to scale-dependent galaxy bias as a function of galaxy population. We use the Sloan Digital Sky Survey Data Release 5 sample to fit various models, which attempt to parametrize the turn-off from scale-independent behaviour. For blue galaxies, we find that the strength of the turn-off is strongly dependent on galaxy luminosity, with stronger scale-dependent bias on larger scales for more luminous galaxies. For red galaxies, the scale dependence is a weaker function of luminosity. Such trends need to be modelled in order to optimally extract the information available in future surveys, and can help with the design of such surveys. [source] Toroidal magnetic fields in type II superconducting neutron starsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2008T. Akgün ABSTRACT We determine constraints on the form of axisymmetric toroidal magnetic fields dictated by hydrostatic balance in a type II superconducting neutron star with a barotropic equation of state. Using Lagrangian perturbation theory, we find the quadrupolar distortions due to such fields for various models of neutron stars with type II superconducting and normal regions. We find that the star becomes prolate and can be sufficiently distorted to display precession with a period of the order of years. We also study the stability of such fields using an energy principle, which allows us to extend the stability criteria established by R. J. Tayler for normal conductors to more general media with magnetic free energy that depends on density and magnetic induction, such as type II superconductors. We also derive the growth rate and instability conditions for a specific instability of type II superconductors, first discussed by P. Muzikar, C. J. Pethick and P. H. Roberts, using a local analysis based on perturbations around a uniform background. [source] Variability in active galactic nuclei: confrontation of models with observationsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2002M.R.S. Hawkins The variability of active galactic nuclei (AGN) has long held the promise of shedding light on their detailed structure, and possibly other astrophysical phenomena. Different emission mechanisms lead to different patterns of variability in flux, which are in principle easily distinguishable. Recent predictions for the expected spectrum of variations for various models are now in such a form that they can be compared with the observed statistical properties of AGN light curves from large-scale monitoring programmes. In this paper, we use the results of a long-term monitoring programme of a large sample of quasars and Seyfert galaxies, as well as individual light curves from the literature, to distinguish between the various model predictions. The results favour a model based on accretion disc instability over the starburst model, where the variation comes from a succession of supernova bursts, but it also appears that much of the observed variation in quasars is due to gravitational microlensing. [source] WEAK AND STRONG SUSTAINABILITY, ENVIRONMENTAL CONSERVATION AND ECONOMIC GROWTHNATURAL RESOURCE MODELING, Issue 3 2006WERNER HEDIGER ABSTRACT. To investigate the role of explicit and implicit assumptions in different models of weak and strong sustain-ability, the Solow/Hartwick model of intergenerational equity with nonrenewable resources is gradually extended to include renewable resources, endogenous technical progress, and stock pollution. This reveals the fundamental role of endogenous technical progress for sustainable development, the inconsistency of implicit sustainability assumptions in various models, as well as the existence of a Hartwick rule for Daly's steady-state economy. Moreover, it shows that the concepts of Solow sustainability and strong sustainability coincide as a special case of weak sustainability. The latter integrates economic and environmental concerns and aims at maintaining the welfare potential of an economy over time. It does not rule out economic growth by assumption. Rather, the analysis shows that environmental conservation and economic growth can be compatible with each other, without jeopardizing social welfare. Finally, the analysis shows that the discussion of sustain-ability models cannot be restricted to the explicit differences that are usually pointed out by their authors and commentators. Rather, implicit assumptions must be made explicit. [source] | ||||||||||||||||||||||||||||