Distribution by Scientific Domains
Distribution within Medical Sciences

Terms modified by Classical

  • classical antiquity
  • classical approach
  • classical biological control
  • classical concept
  • classical conditioning
  • classical example
  • classical feature
  • classical force field
  • classical form
  • classical formulation
  • classical hodgkin lymphoma
  • classical hydrogen bond
  • classical limit
  • classical method
  • classical methods
  • classical model
  • classical models
  • classical molecular dynamics
  • classical molecular dynamics simulation
  • classical music
  • classical notion
  • classical pathway
  • classical period
  • classical problem
  • classical procedure
  • classical result
  • classical risk factor
  • classical role
  • classical solution
  • classical symptom
  • classical system
  • classical techniques
  • classical test
  • classical test theory
  • classical text
  • classical theory
  • classical thermodynamics
  • classical tool
  • classical tradition
  • classical treatment
  • classical view

  • Selected Abstracts

    Classical versus relational approaches to understanding controls on a contract with independent GPs in South Africa

    HEALTH ECONOMICS, Issue 12 2003
    Natasha Palmer
    Abstract Contracts have played a central role in public sector reforms in developed countries over the last decade, and research increasingly highlights their varied nature. In low and middle income countries the use of contracts is encouraged but little attention has been paid to features of the setting that may influence their operation. A qualitative case study was used to examine different dimensions of a contract with private GPs in South Africa. Features of the contract are compared with the notions of classical and relational contracts. Formal aspects of the contract such as design, monitoring and resort to sanctions were found to offer little control over its outcome. The relational rather than classical model of contracting offered a more meaningful framework of analysis, with social and institutional factors found to play an important role. In particular, the individual nature of GP practices highlighted the role played by individual motivation where a contract exercised little formal control. Due to the similarity of factors likely to be present, results are argued to be relevant in many other LMIC settings, and policy-makers considering contracts for clinical services are advised to consider the possibility of experiencing a similar outcome. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Classical and alternative pathway complement activation are not required for reactive systemic AA amyloid deposition in mice

    IMMUNOLOGY, Issue 2 2004
    Winston L. Hutchinson
    Summary During induction of reactive systemic amyloid A protein (AA) amyloidosis in mice, either by chronic inflammation or by severe acute inflammation following injection of amyloid enhancing factor, the earliest deposits form in a perifollicular distribution in the spleen. Because the splenic follicular localization of immune complexes and of the scrapie agent are both complement dependent in mice, we investigated the possible complement dependence of AA amyloid deposition. In preliminary experiments, substantial depletion of circulating C3 by cobra venom factor had little effect on experimental amyloid deposition. More importantly, mice with targeted deletion of the genes for C1q or for both factor B and C2, and therefore unable to sustain activation, respectively, of either the classical complement pathway or both the classical and alternative pathways, showed amyloid deposition similar to wild type controls. Complement activation by either the classical or alternative pathways is thus not apparently necessary for the experimental induction of systemic AA amyloid in mice. [source]

    Classical and advanced multilayered plate elements based upon PVD and RMVT.

    Part 2: Numerical implementations
    Abstract This paper presents numerical evaluations related to the multilayered plate elements which were proposed in the companion paper (Part 1). Two-dimensional modellings with linear and higher-order (up to fourth order) expansion in the z -plate/layer thickness direction have been implemented for both displacements and transverse stresses. Layer-wise as well as equivalent single-layer modellings are considered on both frameworks of the principle of virtual displacements and Reissner mixed variational theorem. Such a variety has led to the implementation of 22 plate theories. As far as finite element approximation is concerned, three quadrilaters have been considered (four-, eight- and nine-noded plate elements). As a result, 22×3 different finite plate elements have been compared in the present analysis. The automatic procedure described in Part 1, which made extensive use of indicial notations, has herein been referred to in the considered computer implementations. An assessment has been made as far as convergence rates, numerical integrations and comparison to correspondent closed-form solutions are concerned. Extensive comparison to early and recently available results has been made for sample problems related to laminated and sandwich structures. Classical formulations, full mixed, hybrid, as well as three-dimensional solutions have been considered in such a comparison. Numerical substantiation of the importance of the fulfilment of zig-zag effects and interlaminar equilibria is given. The superiority of RMVT formulated finite elements over those related to PVD has been concluded. Two test cases are proposed as ,desk-beds' to establish the accuracy of the several theories. Results related to all the developed theories are presented for the first test case. The second test case, which is related to sandwich plates, restricts the comparison to the most significant implemented finite elements. It is proposed to refer to these test cases to establish the accuracy of existing or new higher-order, refined or improved finite elements for multilayered plate analyses. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Design of Robust Control Systems from Classical to Modern Practical Approaches, Krieger Publishing Co., Malabar, FL 32950, ISBN 1-57524-143-9, 2001.

    Yossi Chait Dr.
    No abstract is available for this article. [source]

    Theorizing Diaspora: Perspectives on "Classical" and "Contemporary" Diaspora

    Michele Reis
    Cohen (1997) employed the term "classical" diaspora in reference to the Jews. Indeed, a vast corpus of work recognizes the Jewish people as examples of quintessential diasporic groups. However, a broader conceptualization of the term diaspora allows for the inclusion of immigrant communities that would be otherwise sidelined in the conventional literature on diaspora. This study is therefore a departure from the traditional diasporic literature, which tends to use the Jewish Diaspora as the archetype. It favours, rather, the classification of three principal broad historical waves in which the Jewish Diaspora can be interpreted as part of a classical period. The historicizing of diasporization for the purpose of this paper is achieved by an empirical discussion of the three major historical waves that influenced the diasporic process throughout the world: the Classical Period, the Modern Period, and the Contemporary or Late-modern Period. The paper discusses these three critical phases in the following manner: first, reference is made to the Classical Period, which is associated primarily with ancient diaspora and ancient Greece. The second historical phase analyses diaspora in relation to the Modern Period, which can be interpreted as a central historical fact of slavery and colonization. This section can be further subdivided into three large phases: (1) the expansion of European capital (1500,1814), (2) the Industrial Revolution (1815,1914), and (3) the Interwar Period (1914,1945). The final major period of diasporization can be considered a Contemporary or Late-modern phenomenon. It refers to the period immediately after World War II to the present day, specifying the case of the Hispanics in the United States as one key example. The paper outlines some aspects of the impact of the Latin American diaspora on the United States, from a socio-economic and politico-cultural point of view. While the Modern and Late-modern periods are undoubtedly the most critical for an understanding of diaspora in a modern, globalized context, for the purpose of this paper, more emphasis is placed on the latter period, which illustrates the progressive effect of globalization on the phenomenon of diasporization. The second period, the Modern Phase is not examined in this paper, as the focus is on a comparative analysis of the early Classical Period and the Contemporary or Late-modern Period. The incorporation of diaspora as a unit of analysis in the field of international relations has been largely neglected by both recent and critical scholarship on the subject matter. While a growing number of studies focus on the increasing phenomenon of diasporic communities, from the vantage of social sciences, the issue of diaspora appears to be inadequately addressed or ignored altogether. Certain key factors present themselves as limitations to the understanding of the concept, as well as its relevance to the field of international relations and the social sciences as a whole. This paper is meant to clarify some aspects of the definition of diaspora by critiquing the theories in the conventional literature, exposing the lacunae in terms of interpretation of diaspora and in the final analysis, establishing a historiography that may be useful in comparing certain features of "classical" diaspora and "contemporary" diaspora. The latter part of the paper is intended to provide illustrations of a contemporary diasporic community, using the example of Hispanics in the United States. [source]

    Classical and modern heuristics for the vehicle routing problem

    G. Laporte
    Abstract This article is a survey of heuristics for the Vehicle Routing Problem. It is divided into two parts: classical and modern heuristics. The first part contains well-known schemes such as, the savings method, the sweep algorithm and various two-phase approaches. The second part is devoted to tabu search heuristics which have proved to be the most successful metaheuristic approach. Comparative computational results are presented. [source]

    The Blalock-Taussig Shunt

    Shi-Min Yuan M.D.
    This warrants us a zest in making a comprehensive survey on this subject. Methods: Articles were extensively retrieved from the MEDLINE database of National Library of Medicine USA if the abstract contained information relevant to the B-T shunt in terms of the conduit options, modified surgical techniques, surgical indications, short- and long-term results, complications, and prognosis. Further retrieval was undertaken by manually searching the reference list of relevant papers. Results: Classical or modified B-T shunts, either on ipsilateral or contralateral side to the aortic arch, can be performed on patients of any age with minimum postoperative complications and low operative mortality. Expended polytetrafluoroethylene has gained satisfactory long-term patency rate in the construction of the modified B-T shunt. Excellent pulmonary artery growth was observed in the patients with a modified B-T shunt, and it has shown superb prognosis over the classic with regard to hemodynamics, patency rate, and survival. Conclusions: The modified B-T shunt that was developed on basis of the classic fashion remains the preferable palliative procedure aiming at enhancing pulmonary blood flow for neonates and infants with complicated cyanotic congenital heart defects. The modified B-T shunt is technically simpler with less dissection, and blood flow to the respective arm is not jeopardized. It has been proved to be of low risk, excellent palliation, and is associated with excellent pulmonary artery growth, has become the most effective palliative shunt procedure of today. [source]

    Playing with bone and fat

    Jeffrey M. Gimble
    Abstract The relationship between bone and fat formation within the bone marrow microenvironment is complex and remains an area of active investigation. Classical in vitro and in vivo studies strongly support an inverse relationship between the commitment of bone marrow-derived mesenchymal stem cells or stromal cells to the adipoctye and osteoblast lineage pathways. In this review, we focus on the recent literature exploring the mechanisms underlying these differentiation events and discuss their implications relevant to osteoporosis and regenerative medicine. J. Cell. Biochem. 98: 251,266, 2006. © 2006 Wiley-Liss, Inc. [source]

    New Shade Guide for Evaluation of Tooth Whitening,Colorimetric Study

    ABSTRACT Statement of the Problem:, Available shade guides lack colorimetric uniformity, which compromises the validity of visual evaluation of tooth whitening efficacy. Purpose:, The objective of this study was to perform a colorimetric analysis of a new shade guide designed primarily for the visual evaluation of tooth whitening efficacy and to compare this shade guide with two commercial shade guides. Materials and Methods:, Color ranges and color distribution of three shade guides (prototype of the new Vita Bleachedguide 3D-Master [BG, Vita Zahnfabrik, Bad Säckingen, Germany], value scale of Vitapan Classical [VC, Vita], and color-ordered Trubyte Bioform porcelain shade guide [TB, Dentsply International, York, PA, USA]) were analyzed (N=3). A circular area (d=1.7 mm) on the middle of the labial surface of the tab, excluding the cervical portion, was measured with a spectroradiometer (D65, 2). Whiteness and yellowness indices were computed. Data were analyzed by analysis of variance and Fisher's PLSD test at a 0.05 level of significance. Results:, The range of color difference (,E*) from the lightest to the darkest tab was 33.8 (BG), 17.1 (VC), and 23.2 (TB). Mean values of ,E* among pairs of adjacent tabs were 3.0 (BG), 4.2 (VC), and 3.3 (TB). BG exhibited the highest R2 values between color coordinate pairs and between whiteness and yellowness indices with the respective color coordinates. Conclusions:, BG exhibited the widest color range and had the most consistent color distribution as compared with the two commercial products. Extension of the lightness range of BG toward higher L* values (bleach shades) was confirmed. CLINICAL SIGNIFICANCE A dental shade guide that is colorimetrically uniform might increase the reliability of visual comparisons of tooth whitening efficacy, whereas the inclusion of realistic bleaching shades in the shade guide will complement contemporary esthetic dentistry. (J Esthet Restor Dent 19:276,283, 2007) [source]

    Ecological specialization correlates with genotypic differentiation in sympatric host-populations of the pea aphid

    Abstract The pea aphid, Acyrthosiphon pisum, encompasses distinct host races specialized on various Fabaceae species, but the extent of genetic divergence associated with ecological specialization varies greatly depending on plant and geographic origins of aphid populations. Here, we studied the genetic structure of French sympatric pea aphid populations collected on perennial (pea and faba bean) and annual (alfalfa and red clover) hosts using 14 microsatellite loci. Classical and Bayesian population genetics analyses consistently identified genetic clusters mostly related to plant origin: the pea/faba bean cluster was highly divergent from the red clover and the alfalfa ones, indicating they represent different stages along the continuum of genetic differentiation. Some genotypes were assigned to a cluster differing from the one expected from their plant origin while others exhibited intermediate genetic characteristics. These results suggest incomplete barriers to gene flow. However, this limited gene flow seems insufficient to prevent ecological specialization and genetic differentiation in sympatry. [source]

    Ferrocenyl-functionalized long chain branched polydienes

    Frederik Wurm
    Abstract A convenient two-step approach for the synthesis of ferrocenyl-functionalized long chain branched polydienes, based on both butadiene and isoprene, respectively, is presented. Classical living anionic polymerization was used to synthesize different ABn type poly(diene) macromonomers with moderate molecular weights between 1700 and 3200 g/mol and narrow polydispersity. Quantitative end-capping with chlorodimethylsilane resulted in the desired ABn macromonomer structures. In the ensuing Pt-catalyzed hydrosilylation polyaddition, branched, functionalized polydienes were obtained by a concurrent ABn + AR type of copolymerization with mono- and difunctional ferrocenyl silanes (fcSiMe2H or fc2SiMeH). Molecular weights of the branched polymers were in the range of 10,000 to 44,000 g/mol (SEC/MALLS). Because of the large number of functional end groups, high loading with ferrocene units up to 63 wt % of ferrocene was achieved. Detailed studies showed full conversion of the functional silanes and incorporation into the branched polymer. Further studies using DSC, TGA, and cyclovoltammetry (CV) measurements have been performed. Electrochemical studies demonstrated different electrochemical properties for fcSiMe2 - and fc2SiMe-units. The CVs of polymers modified with diferrocenylsilane units exhibit the pattern of communicating ferrocenyl sites with two distinct, separate oxidation waves. The polymers were also deposited on an electrode surface and the electrodes investigated via CV, showing formation of electroactive films with promising results for the use of the materials in biosensors. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2518,2529, 2009 [source]

    Holocene climate change in the eastern Mediterranean region: a comparison of stable isotope and pollen data from Lake Gölhisar, southwest Turkey,

    Warren J. Eastwood
    Abstract Stable isotope and pollen data from Gölhisar Gölü, a small intramontane lake located in southwest Turkey, provide complementary records of Holocene climate change. Modern oxygen and hydrogen isotope water data are used as a means of comparing present-day isotope composition of the lake water to the past oxygen isotope composition of the lake water as calculated from 18O/16O ratios in calcite precipitated in the summer months. Despite the lake system being chemically dilute, the modern isotope data clearly establish that the lake water is evaporated in relation to its spring input, suggesting that the palaeo data can be interpreted primarily in terms of changing precipitation/evaporation ratios. ,18O and ,13C values from authigenic calcite through the Holocene show predominantly negative values indicating climatic conditions wetter than today. Particularly notable are low (depleted) isotope values during the earliest Holocene (ca. 10,600,8800 cal. yr. BP), a period for which pollen data imply drier conditions than at present. This divergence between pollen-inferred and stable isotope palaeoclimate data is found in other east Mediterranean lake sediment records, and suggests that vegetation may have taken several millennia to reach climatic equilibrium at the start of the Holocene. Isotopic fluctuations during the early-to-mid Holocene (8800,5100 cal. yr. BP) suggest oscillations between aridity and humidity. Higher ,18O and ,13C values for the second half of the Holocene indicate generally drier conditions than during the period before ca.5100 cal. yr BP although there is some evidence for increased humidity coinciding with pollen evidence for increasing human impact and intensification of agriculture, notably during the so-called Bey,ehir Occupation Phase (Classical and early Byzantine periods). The modern trend towards aridity started about 1300 yr ago. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Classical and Impulse Stochastic Control of the Exchange Rate Using Interest Rates and Reserves

    Abel Cadenillas
    We consider the problem of a Central Bank that wants the exchange rate to be as close as possible to a given target, and in order to do that uses both the interest rate level and interventions in the foreign exchange market. We model this as a mixed classical-impulse stochastic control problem, and provide for the first time a solution to that kind of problem. We give examples of solutions that allow us to perform an interesting economic analysis of the optimal strategy of the Central Bank. [source]

    Classical and Neoclassical Indeterminacy in One-shot Versus Ongoing Equilibria

    METROECONOMICA, Issue 3 2002
    Michael Mandler
    I analyze two connections between neoclassical and classical economics. First, I consider the indeterminacy that arises for both schools: in the neoclassical theories of overlapping generations and of factor pricing and in Sraffa's price theory. Neoclassical indeterminacy occurs only in environments where relative prices can change through time; otherwise, determinacy obtains. Although these results challenge the Sraffian position on indeterminacy, the classical principle that current economic activity is embedded in the past proves to be a powerful insight: it establishes the robustness of factor-price indeterminacy and casts doubt on the importance of overlapping-generations indeterminacy. Second, I argue that recent claims that capital-theoretic paradoxes arise in intertemporal general equilibrium modes, not just in aggregative theory, cannot be validated. [source]

    Burgstaller on the Common Core of Classical and Walrasian Economics

    METROECONOMICA, Issue 2 2001
    Fabio Petri
    First page of article [source]

    Classical and contemporary Italy in Roger Ascham's The Scholemaster (1570)

    Melanie Ord
    This article seeks to show that a consideration of the use of Italy in Roger Ascham's The Scholemaster (1570) is illuminated by a study of the structural progression of book 1 (from educational methodologies, to a declamation against courtly vices, to an objection to travel to Italy). Specifically, it argues that the final section on Italy is conceived as a threat to those pedagogical and moral ideals of order, discipline and discrimination outlined in earlier sections; and that this closing statement forcibly demonstrates, and gives particular expression to, Ascham's humanist commitment to maintaining such well-schooled qualities against pernicious contemporary influences. Attention directed to the range of concerns addressed in the text also points to Ascham's conflicted use of Italy. For whilst his humanist educative project accompanies a concern to privilege the moral and cultural influences of classical over contemporary Italy, his national project of literary acculturation (witnessed in such things as his objection to courtly versifying) involves an attempt to conflate, rather than to distinguish, specific Italian identities. [source]

    A full-factor multivariate GARCH model

    I. D. Vrontos
    A new multivariate time series model with time varying conditional variances and covariances is presented and analysed. A complete analysis of the proposed model is presented consisting of parameter estimation, model selection and volatility prediction. Classical and Bayesian techniques are used for the estimation of the model parameters. It turns out that the construction of our proposed model allows easy maximum likelihood estimation and construction of well-mixing Markov chain Monte Carlo (MCMC) algorithms. Bayesian model selection is addressed using MCMC model composition. The problem of accounting for model uncertainty is considered using Bayesian model averaging. We provide implementation details and illustrations using daily rates of return on eight stocks of the US market. [source]

    Synthetic Strategy of Nonreducing Iterative Polyketide Synthases and the Origin of the Classical "Starter-Unit Effect"

    CHEMBIOCHEM, Issue 7 2008
    Jason M. Crawford Dr.
    Getting started: The starter-unit effect in fungal polyketides stems from starter unit:acyl-carrier protein transacylase (SAT) domains found in nonreducing polyketide synthases (PKSs). Dissection of the PKSs involved in the production of naphthopyrone YWA1, tetrahydroxynaphthalene, cercosporin, and bikaverin revealed that their SAT domains had high selectivity for acetyl-CoA (see figure); this provides a biochemical rationale for this classically observed effect. [source]

    Decreased drug-cue-induced attentional bias in individuals with treated and untreated drug dependence

    Simona Gardini
    Objective: The present study investigated the attentional bias induced by drug-related stimuli in active abusers; abstinent abusers on opioid substitution therapy; and abstinent drug-dependent patients in recovery on a community-based non-pharmacological therapy programme. Drug-dependent groups included both cocaine and heroin abusers. Methods: Classical and emotional Stroop tasks were used to test all drug-dependent patients and controls with no history of addiction. Response times were recorded. An interference effect was obtained by comparing the congruent and incongruent conditions in the classical Stroop version. An attentional bias towards drug cues was derived by comparing latencies in the neutral and emotional conditions of the emotional Stroop. Results: No between-group differences were found in the classical Stroop. In the emotional Stroop, active drug-dependent patients showed higher attentional bias (i.e. longer response times to drug-related words) than any of the other three groups. Conclusion: The attentional bias induced by drug cues in patients with addiction disorder might change depending on the patients' clinical status. All treated patients, whether on opioid substitution therapy or on community therapy, showed less attentional bias towards drug-related stimuli than active drug users, although the observed smaller bias was most likely induced by therapy acting through different mechanisms. Although drug-cues response is influenced by other multiple variables, e.g. motivation, craving, classical conditioning and substance availability, these data lend support to the hypothesis that treatment might contribute to decrease the attentional bias towards drug cues, which seems to play a critical role in achieving a positive outcome in the treatment of addiction. [source]

    ChemInform Abstract: Synthesis, Antifolate, and Antitumor Activities of Classical and Nonclassical 2-Amino-4-oxo-5-substituted-pyrrolo[2,3-d]pyrimidines.

    CHEMINFORM, Issue 38 2001
    Alleem Gangjee
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Electronic Structure and Bonding in Neutral and Dianionic Boradiphospholes: R,BC2P2R2 (R=H, tBu, R,=H, Ph)

    Dandamudi Usharani
    Abstract Classical and non-classical isomers of both neutral and dianionic BC2P2H3 species, which are isolobal to Cp+ and Cp,, are studied at both B3LYP/6-311++G(d,p) and G3B3 levels of theory. The global minimum structure given by B3LYP/6-311++G(d,p) for BC2P2H3 is based on a vinylcyclopropenyl-type structure, whereas BC2P2H32, has a planar aromatic cyclopentadienyl-ion-like structure. However, at the G3B3 level, there are three low-energy isomers for BC2P2H3: 1),tricyclopentane, 2),nido and 3),vinylcyclopropenyl-type structures, all within 1.7,kcal,mol,1 of each other. On the contrary, for the dianionic species the cyclic planar structure is still the minimum. In comparison to the isolobal Cp+ and HnCnP5,n+ isomers, BC2P2H3 shows a competition between ,-delocalised vinylcyclopropenyl- and cluster-type structures (nido and tricyclopentane). Substitution of H on C by tBu, and H on B by Ph, in BC2P2H3 increases the energy difference between the low-lying isomers, giving the lowest energy structure as a tricyclopentane type. Similar substitution in BC2P2H32, merely favours different positional isomers of the cyclic planar geometry, as observed in 1),isoelectronic neutral heterodiphospholes EtBu2C2P2 (E=S, Se, Te), 2),monoanionic heterophospholyl rings EtBu2C2P2 (E=P,, As,, Sb,) and 3),polyphospholyl rings anions tBu5,nCnP5,n (n=0,5). The principal factors that affect the stability of three-, four-, and five-membered ring and acyclic geometrical and positional isomers of neutral and dianionic BC2P2H3 isomers appear to be: 1),relative bond strengths, 2),availability of electrons for the empty 2p boron orbital and 3),steric effects of the tBu groups in the HBC2P2tBu2 systems. [source]

    Analysis of Classical and Quantum Paths for Deprotonation of Methylamine by Methylamine Dehydrogenase

    CHEMPHYSCHEM, Issue 12 2007
    Kara E. Ranaghan
    Abstract The hydrogen-transfer reaction catalysed by methylamine dehydrogenase (MADH) with methylamine (MA) as substrate is a good model system for studies of proton tunnelling in enzyme reactions,an area of great current interest,for which atomistic simulations will be vital. Here, we present a detailed analysis of the key deprotonation step of the MADH/MA reaction and compare the results with experimental observations. Moreover, we compare this reaction with the related aromatic amine dehydrogenase (AADH) reaction with tryptamine, recently studied by us, and identify possible causes for the differences observed in the measured kinetic isotope effects (KIEs) of the two systems. We have used combined quantum mechanics/molecular mechanics (QM/MM) techniques in molecular dynamics simulations and variational transition state theory with multidimensional tunnelling calculations averaged over an ensemble of paths. The results reveal important mechanistic complexity. We calculate activation barriers and KIEs for the two possible proton transfers identified,to either of the carboxylate oxygen atoms of the catalytic base (Asp428,),and analyse the contributions of quantum effects. The activation barriers and tunnelling contributions for the two possible proton transfers are similar and lead to a phenomenological activation free energy of 16.5±0.9 kcal,mol,1 for transfer to either oxygen (PM3-CHARMM calculations applying PM3-SRP specific reaction parameters), in good agreement with the experimental value of 14.4 kcal,mol,1. In contrast, for the AADH system, transfer to the equivalent OD1 was found to be preferred. The structures of the enzyme complexes during reaction are analysed in detail. The hydrogen bond of Thr474,(MADH)/Thr172,(AADH) to the catalytic carboxylate group and the nonconserved active site residue Tyr471,(MADH)/Phe169,(AADH) are identified as important factors in determining the preferred oxygen acceptor. The protein environment has a significant effect on the reaction energetics and hence on tunnelling contributions and KIEs. These environmental effects, and the related clearly different preferences for the two carboxylate oxygen atoms (with different KIEs) in MADH/MA and AADH/tryptamine, are possible causes of the differences observed in the KIEs between these two important enzyme reactions. [source]

    Backbone-Only Protein Solution Structures with a Combination of Classical and Paramagnetism-Based Constraints: A Method that Can Be Scaled to Large Molecules

    CHEMPHYSCHEM, Issue 6 2004
    Renato Barbieri Dr.
    Abstract Herein, it is shown that a medium-resolution solution structure of a protein can be obtained with the sole assignment of the protein backbone and backbone-related constraints if a derivative with a firmly bound paramagnetic metal is available. The proof-of-concept is provided on calbindin D9k, a calcium binding protein in which one of the two calcium ions can be selectively substituted by a paramagnetic lanthanide ion. The constraints used are HN (and H,) nuclear Overhauser effects (NOEs), hydrogen bonds, dihedral angle constraints from chemical shifts, and the following paramagnetism-based constraints: 1) pseudocontact shifts, acquired by substituting one (or more) lanthanide(s) in the C-terminal calcium binding site; 2) NHN residual dipolar couplings due to self-orientation induced by the paramagnetic lanthanide(s); 3) cross-correlations between the Curie and internuclear dipole,dipole interactions; and 4) paramagnetism-induced relaxation rate enhancements. An upper distance limit for internuclear distances between any two backbone atoms was also given according to the molecular weight of the protein. For this purpose, the paramagnetism-based constraints were collectively implemented in the program CYANA for solution structure determinations, similarly to what was previously done for the program DYANA. The method is intrinsically suitable for large molecular weight proteins. [source]

    Long-term outcome of classical 21-hydroxylase deficiency: diagnosis, complications and quality of life

    ACTA PAEDIATRICA, Issue 2 2000
    J Jääskeläinen
    A nationwide search of patients with classical 21-hydroxylase deficiency (21-OHD) was performed in Finland to determine the long-term outcome of the disease. In total, 108 patients were found. Fifty-four patients (50%, 31F, 23M) had deficiency of a salt-wasting form and another 54 (50%, 29F, 25M) had a simple virilizing form of 21-OHD. A significant number of severe complications suggestive of glucocorticoid deficiency was found. There were five deaths (4.6% of all) possibly connected with cortisol deficiency. Ten additional patients (9.3% of all) had been acutely admitted 14 times in all due to symptoms of glucocorticoid deficiency. These symptoms included sudden loss of consciousness, convulsions and severe fatigue. Afterwards, permanent neurological defects were detected in two of these patients. Finally, a cross-sectional study was carried out to establish an estimate of the long-term outcome of the disease. Thirty-two (55%) of the 58 patients aged 16 y or more participated in this study. The patient group did not differ from the general Finnish population in terms of education. Three of the patients (5%) had retired prematurely. Surprisingly, the patients felt that their health-related quality of life, as reported in the RAND-36 questionnaire, was better than that of the general Finnish population (p= 0.023). However, as a significant number of all patients did not participate in this study, the quality of life evaluation results must be interpreted with caution. In conclusion, a significant number of complications was found among patients treated for classical 21-OHD. Nevertheless, the disease has a favourable outcome in terms of quality of life. [source]

    Metapopulation Extinction Risk under Spatially Autocorrelated Disturbance

    patrón espacial de perturbación; simulaciones espacialmente explícitas; SLOSS; umbral de extinción Abstract:,Recent extinction models generally show that spatial aggregation of habitat reduces overall extinction risk because sites emptied by local extinction are more rapidly recolonized. We extended such an investigation to include spatial structure in the disturbance regime. A spatially explicit metapopulation model was developed with a wide range of dispersal distances. The degree of aggregation of both habitat and disturbance pattern could be varied from a random distribution, through the intermediate case of a fractal distribution, all the way to complete aggregation (single block). Increasing spatial aggregation of disturbance generally increased extinction risk. The relative risk faced by populations in different landscapes varied greatly, depending on the disturbance regime. With random disturbance, the spatial aggregation of habitat reduced extinction risk, as in earlier studies. Where disturbance was spatially autocorrelated, however, this advantage was eliminated or reversed because populations in aggregated habitats are at risk of mass extinction from coarse-scale disturbance events. The effects of spatial patterns on extinction risk tended to be reduced by long-distance dispersal. Given the high levels of spatial correlation in natural and anthropogenic disturbance processes, population vulnerability may be greatly underestimated both by classical (nonspatial) models and by those that consider spatial structure in habitat alone. Resumen:,Los modelos recientes de extinción generalmente muestran que la agregación espacial de hábitat reduce el riesgo de extinción debido a una recolonización más rápida de sitios vacíos por extinción local. Extendimos la investigación para incluir la estructura espacial en el régimen de perturbación. Desarrollamos un modelo metapoblacional espacialmente explícito en el que el patrón espacial tanto del hábitat como de los regímenes de perturbación podía variar aleatoriamente de fractal a completamente agregado (bloque) y con una amplia gama de distancias de dispersión. El incremento de la agregación espacial de la perturbación generalmente incrementó el riesgo de extinción. El riesgo relativo que enfrentan poblaciones en paisajes diferentes fue muy variable, dependiendo del régimen de perturbación. Con perturbación aleatoria, la agregación espacial de hábitat redujo el riesgo de extinción, como en estudios anteriores. Sin embargo, cuando la perturbación estaba autocorrelacionada espacialmente, esta ventaja se eliminaba o invertía debido a que las poblaciones en hábitats agregados están en riesgo de extinción masiva por eventos perturbadores a escala gruesa. Los efectos de patrones espaciales sobre el riesgo de extinción tendieron a reducirse por la dispersión de larga distancia. Debido a los altos niveles de correlación espacial en los procesos naturales y humanos de perturbación, la vulnerabilidad puede estar enormemente subestimada tanto por modelos clásicos (no espaciales) como por los que sólo consideran la estructura espacial del habitat. Los modelos que consideran la estructura espacial del hábitat solo subestiman el riesgo en comparación con modelos que consideran la estructura especial de la perturbación. [source]

    Hypernetted Chain Calculations for Two-Component Plasmas

    V. Schwarz
    Abstract We have performed HNC calculations for dense beryllium plasma as studied experimentally using x-ray Thomson scattering, recently. We treated non-equilibrium situations with different electron and ion temperatures which are relevant in pump-probe experiments on ultra-short time scales. To consider quantum effects adequately, we used effective pair potentials to describe the interactions. Results are compared with classical as well as quantum corrected Debye model calculations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Equilibrium and growth shapes of crystals: how do they differ and why should we care?

    Robert F. SekerkaArticle first published online: 15 MAR 200
    Abstract Since the death of Prof. Dr. Jan Czochralski nearly 50 years ago, crystals grown by the Czochralski method have increased remarkably in size and perfection, resulting today in the industrial production of silicon crystals about 30 cm in diameter and two meters in length. The Czochralski method is of great technological and economic importance for semiconductors and optical crystals. Over this same time period, there have been equally dramatic improvements in our theoretical understanding of crystal growth morphology. Today we can compute complex crystal growth shapes from robust models that reproduce most of the features and phenomena observed experimentally. We should care about this because it is likely to result in the development of powerful and economical design tools to enable future progress. Crystal growth morphology results from an interplay of crystallographic anisotropy and growth kinetics by means of interfacial processes and long-range transport. The equilibrium shape of a crystal results from minimizing its anisotropic surface free energy under the constraint of constant volume; it is given by the classical Wulff construction but can also be represented by an analytical formula based on the ,-vector formalism of Hoffman and Cahn. We now have analytic criteria for missing orientations (sharp corners or edges) on the equilibrium shape, both in two (classical) and three (new) dimensions. Crystals that grow under the control of interfacial kinetic processes tend asymptotically toward a "kinetic Wulff shape", the analogue of the Wulff shape, except it is based on the anisotropic interfacial kinetic coefficient. If it were not for long range transport, crystals would presumably nucleate with their equilibrium shape and then evolve toward their "kinetic Wulff shape". Allowing for long range transport leads to morphological instabilities on the scale of the geometric mean of a transport length (typically a diffusivity divided by the growth speed) and a capillary length (of the order of atomic dimensions). Resulting crystal growth shapes can be cellular or dendritic, but can also exhibit corners and facets related to the underlying crystallographic anisotropy. Within the last decade, powerful phase field models, based on a diffuse interface, have been used to treat simultaneously all of the above phenomena. Computed morphologies can exhibit cells, dendrites and facets, and the geometry of isotherms and isoconcentrates can also be determined. Results of such computations are illustrated in both two and three dimensions. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Ring chromosome 20 syndrome with intractable epilepsy

    Asude Alpman MD
    Ring chromosome 20 (r[20]) syndrome is characterized by mild to moderate learning disability*, behavioural disorders, epilepsy, and various dysmorphic features. Although still considered rare, r(20) syndrome is being increasingly diagnosed. More than 30 cases have been described in the literature since 1976. Here we report an additional case of a 14-year-old male with r(20). He had moderate to severe learning disability and epileptic seizures manifesting at about 18 months of age. During the 13 years' follow-up period he showed intractable epileptic seizures, behavioural disorders, and mild dysmorphological features including microcephaly, strabismus, micrognathia, down-slanting eyelids, and ear abnormalities. Frequent episodes of atypical absence or non-convulsive status associated with electroencephalogram changes were seen in follow-up. He was treated with several classical and new antiepileptic drugs, including intravenous immunoglobulin, corticotropin, and vagal nerve stimulation, with unsuccessful control of seizures. Finally, surgical treatment (corpus callosotomy) was performed at the age of 13 years; severity of tonic seizures was diminished, but frequency was unchanged. Although his behavioural problems, e.g. hyperactivity, were mild in early childhood they became more severe when he was 11 years old. Aggressiveness, compulsiveness with self-injury, and panic attacks developed at the age of 13 years, and were more pronounced after callosotomy. This case report provides the first description of deterioration in psychological situation in patients with r(20) intractable epilepsy. The patient was diagnosed with r(20) syndrome after 13 years of clinical follow-up. Karyotype analysis should, therefore, be performed in every patient with intractable epilepsy of unknown aetiology. [source]

    Non-alcoholic fatty liver disease, the metabolic syndrome and the risk of cardiovascular disease: the plot thickens

    DIABETIC MEDICINE, Issue 1 2007
    G. Targher
    Abstract Non-alcoholic fatty liver disease (NAFLD) affects a substantial proportion of the general population and is frequently associated with many features of the metabolic syndrome (MetS). Currently, the importance of NAFLD and its relationship with the MetS is being increasingly recognized, and this has stimulated an interest in the possible role of NAFLD in the development of atherosclerosis. Recent studies have reported the association of NAFLD with multiple classical and non-classical risk factors for cardiovascular disease (CVD). Moreover, there is a strong association between the severity of liver histopathology in NAFLD patients and greater carotid artery intima-media thickness and plaque, and lower endothelial flow-mediated vasodilation (as markers of subclinical atherosclerosis) independent of obesity and other MetS components. Finally, it has recently been demonstrated that NAFLD is associated with an increased risk of all-cause death and predicts future CVD events independently of other prognostic factors, including MetS components. Overall, therefore, the evidence from these recent studies strongly emphasizes the importance of assessing the global CVD risk in patients with NAFLD. Moreover, these novel findings suggest a more complex picture and raise the possibility that NAFLD, as a component of the MetS, might not only be a marker but also an early mediator of CVD. [source]

    Cytohistologic correlations in schwannomas (neurilemmomas), including "ancient," cellular, and epithelioid variants

    Jerzy Klijanienko M.D.
    Abstract Schwannoma accounts for one of the most common benign mesenchymal neoplasms of soft tissues. Although it is well defined in the cytology literature, particular histologic subtypes such as "ancient," cellular and epitheliod variants could be a source of diagnostic difficulties. We have reviewed cytology aspirates and corresponding histologic sections from 34 schwannomas diagnosed at Institut Curie. Histologically, 24 cases were classic, 5 were "ancient," 4 were cellular, and 1 was epithelioid schwannomas. No example of melanotic schwannoma was recorded. Original cytologic diagnosis was schwannoma in 13 (38.2%) cases, benign soft tissue tumor in 11 (32.4%), pleomorphic adenoma in 2 (6%) cases, angioma in 1 (2.9%) case, nodular fasciitis in 1 (2.9%) case, suspicious in 3 (8.8%) cases, and not satisfactory in 3 (8.8%) cases. There were no major differences between classical, "ancient," cellular, and epithelioid variants on cytology smears. Myxoid stroma, mast cells, and intranuclear inclusions were limited to classical subtype. Similarly, cyto-nuclear atypia was more frequent in classical subtype than in other subtypes. Schwannoma should be differentiated from well-differentiated malignant peripheral nerve sheath tumor, neurofibroma, and pleomorphic adenoma, in the last instance particularly for head and neck lesions. Diagn. Cytopathol. 2006;34:517,522. © 2006 Wiley-Liss, Inc. [source]