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Critical Point (critical + point)
Kinds of Critical Point Selected AbstractsRelationship between substituent effect and aromaticity , Part III: naphthalene as a transmitting moiety for substituent effectJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2007Tadeusz M. Krygowski Abstract Molecular geometry of 10 isomeric nitronaphtholate ions (excluding peri - and ortho -type substituted systems), 1- and 2-naphtholate ions, 1- and 2-nitronaphthalene, meta - and para -nitrophenolate, phenolate, and nitrobenzene were optimized at B3LYP/6-311G** level of approximation. Substituent effect stabilization energy (SESE), geometry-based aromaticity index HOMA, magnetism-based indices NICS, NICS(1), NICS(1)zz, and parameters characterizing Bond Critical Points (BCP) (,, ,2,, ellipticity, ion/cov) of the Bader AIM theory were used to characterize transmitting properties for substituent effect through the naphthalene moiety. It results from our study that the studied systems could be clearly divided into two groups, (i) a para -type group, where the intramolecular charge transfer between the , -electron donating and , -electron accepting substituents can be described by canonical forms with charge separation (as in the case of para -nitrophenolate) and (ii) a meta -type group, where this transfer requires using canonical forms with double charge separation (as in the case of meta -nitrophenolate). Copyright © 2007 John Wiley & Sons, Ltd. [source] Effects of stem canker (Leptosphaeria maculans) and light leaf spot (Pyrenopeziza brassicae) on yield of winter oilseed rape (Brassica napus) in southern EnglandPLANT PATHOLOGY, Issue 4 2000Y. Zhou The relationships between yield loss and incidence or severity of stem canker and light leaf spot in winter oilseed rape were analysed by correlation and regression analyses, using data from experiments at Rothamsted, England in 1992/93, 1994/95 and 1995/96. Growth stages (GS) 6,3/6,4 and 4,0/4,5 were identified as the critical points for relating percentage yield loss to stem canker and light leaf spot (on stems), respectively. Critical point (CP) and area under disease progress curve (AUDPC) models relating percentage yield loss to combined incidence or severity of stem canker and light leaf spot (stems) in each experiment were constructed by linear regression. There were no differences in the CP models for incidence between 1992/93, 1994/95 and 1995/96 experiments, or in the AUDPC models for incidence between 1992/93 and 1994/95 experiments. Therefore, a general CP model relating percentage yield loss (,Y) to combined incidence of stem canker (Si) at GS 6,3/6,4 and light leaf spot (stems) (Li) at GS 4,0/4,5 was constructed using data from the three experiments: ,Y = 0·85 + 0·079Si + 0·065Li (R2 = 43·7%, P < 0·001, 92 df). A general AUDPC model relating ,Y to the AUDPC of combined incidence of stem canker (Sia) from GS 5·7 to GS 6·5 and light leaf spot (stems) (Lia) from GS 4·0 to GS 6·3 was constructed using data from the 1992/93 and 1994/95 experiments: ,Y = 0·07 + 0·00096Sia + 0·0026Lia (R2 = 43·6%, P < 0·001, 68 df). These two general yield-loss models were tested with data from Rothamsted in 1993/94 and Boxworth in 1992/93. The predictive accuracy of the CP model based on combined incidence of stem canker and light leaf spot (stems) was better than that of the AUDPC model. Yield losses predicted by summing the estimates from individual models for incidence of stem canker alone (GS 6,3/6,4) and light leaf spot alone (on leaves at GS 3,3) were greater than observed yield losses in experiments at Rothamsted in 1992/93, 1993/94, 1994/95 and 1995/96 and at Boxworth in 1992/93. [source] Mechanistic hypotheses for nonsynaptic epileptiform activity induction and its transition from the interictal to ictal state,Computational simulationEPILEPSIA, Issue 11 2008Antônio-Carlos G. De Almeida Summary Purpose:, The aim of this work is to study, by means of computational simulations, the induction and sustaining of nonsynaptic epileptiform activity. Methods:, The computational model consists of a network of cellular bodies of neurons and glial cells connected to a three-dimensional (3D) network of juxtaposed extracellular compartments. The extracellular electrodiffusion calculation was used to simulate the extracellular potential. Each cellular body was represented in terms of the transmembrane ionic transports (Na+/K+ pumps, ionic channels, and cotransport mechanisms), the intercellular electrodiffusion through gap-junctions, and the neuronal interaction by electric field and the variation of cellular volume. Results:, The computational model allows simulating the nonsynaptic epileptiform activity and the extracellular potential captured the main feature of the experimental measurements. The simulations of the concomitant ionic fluxes and concentrations can be used to propose the basic mechanisms involved in the induction and sustaining of the activities. Discussion:, The simulations suggest: The bursting induction is mediated by the Cl, Nernst potential overcoming the transmembrane potential in response to the extracellular [K+] increase. The burst onset is characterized by a critical point defined by the instant when the Na+ influx through its permeable ionic channels overcomes the Na+/K+ pump electrogenic current. The burst finalization is defined by another critical point, when the electrogenic current of the Na+/K+ pump overcomes its influx through the channels. [source] A wedding in the family: home making in a global kin networkGLOBAL NETWORKS, Issue 3 2002Karen Fog Olwig Rituals such as weddings and funerals are significant for transnational family networks as events where scattered relatives meet and validate shared kinship and common origins. They are particularly important when taking place at a family ,home' that has been a centre of social and economic relations and locus of emotional attachment. This article analyses a wedding on a Caribbean island involving a large global family network, which occurred at a critical point in the family's history. It became an occasion when members asserted their notions of belonging rooted in the ,home', not just as members of a common kin group, but as persons whose life trajectories had involved them in different social, economic and geographical contexts. Individually they had dissimilar interpretations and expectations of their place in the home, and these were played out at the wedding. The gathering allowed a display of family solidarity, but was also a site where differing views of individuals' contribution to the global household were expressed, and rights to belong in the family home and, by implication, the island were contested. [source] Comparison of pharyngoesophageal segment pressure in total laryngectomy patients with and without pharyngeal neurectomyHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 8 2003Ahmet Köyba, lu MD Abstract Background. To compare pharyngoesophageal segment (PES) pressure values in total laryngectomy patients with and without pharyngeal neurectomy (PN) in the early postoperative period. Methods. Forty-five previously untreated laryngeal carcinoma patients were enrolled into this prospective randomized study. Twenty of them underwent total laryngectomy with PN, and 25 underwent total laryngectomy without PN. PES pressures were measured on the tenth postoperative day with a four-channel catheter. Results. Average PES pressures in patients with and without pharyngeal neurectomy were 12.82 ± 6.11 mmHg and 17.40 ± .72 mmHg respectively (p < .05). When compared with the critical point of 20 mmHg that is closely related to voice attainment in the group without pharyngeal neurectomy, 10 (40%) patients had pressure levels greater than 20 mmHg and in the other group only 1 (5%) patient had a pressure level greater than 20 mmHg. The difference between the groups with pressure levels greater than 20 mmHg was found to be statistically significant (p < .05). Conclusions. Pharyngeal neurectomy results in a statistically significant decrease of PES pressures in total laryngectomy patients. © 2003 Wiley Periodicals, Inc. Head Neck 25: 617,623, 2003 [source] The Republics of Ideas: Venice, Florence and the Defence of Liberty, 1525,1530HISTORY, Issue 279 2000Stephen D. Bowd The sixteenth century has often been regarded as a crucial period in the history of political events in Italy, and in the history of political ideas. The contributions of Florence and Venice to this process have long been acknowledged. Florentine admiration for the Venetian political system reflected internal political instability in the former city. The evidence for Venetian-Florentine contacts, and for a Venetian concern or admiration for Florence has been less noted. This article aims to show that there is evidence that Venetian concern for the defence of republican liberty after 1525 was allied to an awareness of Florentine political events and their significance for Venetian political practices. This awareness was stimulated by the pressure of imperial intervention on the peninsula after 1525. Florence and Venice were allies under the treaty of Cognac, and diplomats in both cities articulated a concern for republican libertas in Italy and an antipathy towards imperial rule. The work of Gasparo Contarini can be placed in this context, and as a result the critical point in the development of his arguments about Venetian political stability can be placed in the 1520s rather than in the years around 1509. The politics and political ideas of both cities were therefore developed in a wider context than has hitherto been supposed. [source] A note on transaction costs and the interpretation of dividend drop-off ratiosACCOUNTING & FINANCE, Issue 3 2001Graham Partington In a recent edition of this Journal, Bartholdy and Brown (1999) presented an analysis of the ex-dividend share price behaviour of shares listed on the New Zealand Stock Exchange. The authors conclude that their results are consistent with the tax clientele effect (driven by long-term investors) and that there is little or no support for the short-term trading hypothesis. Our purpose is to highlight the importance of transaction costs in analyses such as Bartholdy and Brown's. We argue that their results have an alternative interpretation because their analysis excludes the impact of transaction costs. We extend their model to include transaction costs and show that their results are not necessarily inconsistent with the short-term trading hypothesis. A critical point of our analysis is that, in the presence of transaction costs, the equilibrium drop-off ratio for dividend strip traders will be less than one, and, in some cases, can be less than the equilibrium drop-off ratio for long-term investors. [source] The role of the preBCR, the interleukin-7 receptor, and homotypic interactions during B-cell developmentIMMUNOLOGICAL REVIEWS, Issue 1 2000Angela Stoddart Summary: Considerable progress has been made in defining intermediate stages in the process leading from stem cells to mature B cells. Cell-bound and secreted molecules direct the progression through these stages and regulate the selection of clones from which the immune repertoire emerges. In fact, a myriad of signals derived from B-cell progenitors themselves and the microenvironment in which they develop direct the differentiation process. These signals are provided by B-cell antigen receptors (BCR) and their surrogates, and by adhesion and cytokine receptors. The co-operation of these receptors to control survival, expansion, and differentiation of early B-cell progenitors is the topic of this review. Specifically, we will summarize recent findings from our laboratory demonstrating that preBCR expression lowers the threshold for interleukin (IL)-7 responsiveness. How signals initiated by these receptors may intersect at this critical point of B-cell selection will be discussed. At the stage following IL-7 responsiveness we have shown that interactions between B-cell progenitors themselves promote their differentiation to immunoglobulin-secreting B cells. We propose that one function of stromal cells, known to be central to B lymphopoiesis, is to promote critical preB,preB homotypic interactions and ensuing signals. [source] Modelling of hygro-thermal behaviour and damage of concrete at temperature above the critical point of waterINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2002D. Gawin Abstract In this paper, a model for the analysis of the behaviour of concrete at temperature largely exceeding critical point of water, is presented. In this temperature range liquid phase, i.e. capillary phase, and gas phase cannot be distinguished and only the latter exists. Consequently, capillary pressure has no more physical meaning above this point and liquid water is present only as physically adsorbed water. In this work, we give a different physical interpretation to the capillary pressure and use it still for the description of the hygrometric state of concrete in the zone, where temperature exceeds the critical point of water. Considerable thermal dilatation of the liquid water and the real behaviour of water vapour close to critical temperature are taken into account. Moreover, a special switching procedure in order to avoid the Stefan-like problem, which subsequently arises, is described and employed in the calculations. Finally, several numerical examples demonstrating the robustness of the adopted solution have been shown. Copyright © 2002 John Wiley & Sons, Ltd. [source] Broad tumor spectrum in a mouse model of multiple endocrine neoplasia type 1INTERNATIONAL JOURNAL OF CANCER, Issue 2 2007Kelly A. Loffler Abstract Multiple endocrine neoplasia type 1 (MEN1) is an inherited cancer predisposition syndrome typified by development of tumors in parathyroid, pituitary and endocrine pancreas, as well as less common sites including both endocrine and nonendocrine organs. Deletion or mutation of the tumor suppressor gene MEN1 on chromosome 11 has been identified in many cases of MEN1 as well as in sporadic tumors. The molecular biology of menin, the protein encoded by MEN1, remains poorly understood. Here we describe a mouse model of MEN1 in which tumors were seen in pancreatic islets, pituitary, thyroid and parathyroid, adrenal glands, testes and ovaries. The observed tumor spectrum therefore includes types commonly seen in MEN1 patients and additional types. Pancreatic pathology was most common, evident in over 80% of animals, while other tumor types developed with lower frequency and generally later onset. Tumors of multiple endocrine organs were observed frequently, but progression to carcinoma and metastasis were not evident. Tumors in all sites showed loss of heterozygosity at the Men1 locus, though the frequency in testicular tumors was only 36%, indicating that a different molecular mechanism of tumorigenesis occurs in those Leydig tumors that do not show loss of the normal Men1 allele. Menin expression was below the level of detection in ovary, thyroid and testis, but loss of nuclear menin immunoreactivity was observed uniformly in all pancreatic islet adenomas and in some hyperplastic islet cells, suggesting that complete loss of Men1 is a critical point in islet tumor progression in this model. © 2006 Wiley-Liss, Inc. [source] Theoretical study on the mechanism of reaction between 3-hydroxy-3-methyl-2-butanone and malononitrile catalyzed by magnesium ethoxideINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2009Lin-Sen Heng The mechanism of reaction between 3-hydroxy-3-methyl-2-butanone and malononitrile for the synthesis of 2-dicyanomethylene-4,5,5-trimethyl-2,5-dihydrofuran-3-carbonitrile catalyzed by magnesium ethoxide was investigated by density functional theory (DFT). The geometries and the frequencies of reactants, intermediates, transition states, and products were calculated at the B3LYP/6,31G(d) level. The vibration analysis and the IRC analysis demonstrated the authenticity of transition states, and the reaction processes were confirmed by the changes of charge density at bond-forming critical point. The results indicated that magnesium ethoxide is an effective catalyst in the synthesis of 2-dicyanomethylene-4,5,5-trimethyl-2,5-dihydrofuran-3-carbonitrile from malononitrile and 3-hydroxy-3-methyl-2-butanone. The activation energy of reaction with magnesium ethoxide decreased by 102.37 kJ mol,1 compared with that of the reaction without it. The mechanism of reaction with catalyst magnesium ethoxide differs from that of reaction without it. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 227,235, 2009 [source] Performance and exergetic analysis of vapor compression refrigeration system with an internal heat exchanger using a hydrocarbon, isobutane (R600a)INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2008Ahmet Kabul Abstract Hydrocarbons (HCs) are excellent refrigerants in many ways such as energy efficiency, critical point, solubility, transport and heat transfer properties, but they are also flammable, which causes the need for changes in standards, production and product. There are increasing number of scientists and engineers who believe that an alternative solution, which has been overlooked, may be provided by using HCs. The main objective of this study is to perform energy and exergy analyses for a vapor compression refrigeration system with an internal heat exchanger using a HC, isobutene (R600a). For a refrigeration capacity of 1 kW and cold chamber temperature of 0°C, energy and exergy balances are taken into account to determine the performance of the refrigeration system. Energy and exergy fluxes are determined, and irreversibility rates are calculated for every component of the system. It is seen that the compressor has the highest irreversibility rate, and the heat exchanger has the lowest. Also from the result of the analysis, it is found that condenser and evaporator temperatures have strong effects on energetic and exergetic performances of the system such as coefficient of performance (COP), efficiency ratio (,), exergetic efficiency (,) and irreversibility rate. Copyright © 2008 John Wiley & Sons, Ltd. [source] Exergetic efficiency and options for improving sewage sludge gasification in supercritical waterINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2007Edgar Gasafi Abstract The present article deals with an exergy analysis of a process under development for the gasification of biomass in supercritical water (supercritical water gasification, SCWG). This process is aimed at generating hydrogen out of the biogenic feedstock sewage sludge. The principle of the process is based on making use of the modifications of specific physical and chemical properties of water above the critical point (T=374°C, p=221 bar). These properties allow for a nearly complete conversion of the organic substance contained in the feed material into energy-rich fuel gases, containing hydrogen, carbon dioxide and methane. Based on a steady-state model of the process, exergy flow rates are calculated for all components and a detailed exergy analysis is performed. From the exergetic variables, options to improve the individual plant components as well as the overall plant are derived. The components with the highest proportion of exergy destruction in the complete process are identified and possibilities of improving them and the complete system in order to increase the overall efficiency are demonstrated. The combustion chamber necessary for heat supply is found to be the component with the highest proportion of exergy destruction of the complete plant. Moreover, the components of air preheater, reactor contribute significantly to the exergy destruction of the complete system. Copyright © 2006 John Wiley & Sons, Ltd. [source] HTSC cuprate phase diagram using a modified Boson,Fermion,Gossamer model describing competing orders, a quantum critical point and possible resonance complexINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2009Richard H. Squire Abstract There has been considerable effort expended toward understanding high temperature superconductors (HTSC), and more specifically the cuprate phase diagram as a function of doping level. Yet, the only agreement seems to be that HTSC is an example of a strongly correlated material where Coulomb repulsion plays a major role. This manuscript proposes a model based on a Feshbach resonance pairing mechanism and competing orders. An initial BCS-type superconductivity at high doping is suppressed in the two particle channel by a localized preformed pair (PP) (Nozieres and Schmitt-Rink, J Low Temp Phys, 1985, 59, 980) (circular density wave) creating a quantum critical point. As doping continues to diminish, the PP then participates in a Feshbach resonance complex that creates a new electron (hole) pair that delocalizes and constitutes HTSC and the characteristic dome (Squire and March, Int J Quantum Chem, 2007, 107, 3013; 2008, 108, 2819). The resonant nature of the new pair contributes to its short coherence length. The model we propose also suggests an explanation (and necessity) for an experimentally observed correlated lattice that could restrict energy dissipation to enable the resonant Cooper pair to move over several correlation lengths, or essentially free. The PP density wave is responsible for the pseudogap as it appears as a "localized superconductor" since its density of states and quasiparticle spectrum are similar to those of a superconductor (Peierls,Fröhlich theory), but with no phase coherence between the PP. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Intramolecular proton transfer induced by divalent alkali earth metal cation in the gas stateINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4 2003Hongqi Ai Abstract Interactions between divalent alkali earth metal (DAEM) ions M (MBe, Mg, Ca, Sr, Ba) and the second stable glycine conformer in the gas phase, which can transfer into the ground-state glycine-M2+ (except the glycine,Be2+) among each corresponding isomers when these divalent metal ions are bound, are studied at the hybrid three-parameter B3LYP level with three different basis sets. Proton transfers from the hydroxyl to the amino nitrogen of the glycine without energy barriers have been first observed in the gas phase in these glycine,M2+ systems. The interaction between the glycine and these DAEM ions except beryllium and magnesium ion only create an amino hydrogen pointing to the original hydroxyl due to their weaker interaction relative to those divalent transition metal (DTM) ion-bound glycine derivatives, being obviously different from that between the glycine and DTM ions, in which two amino hydrogens point to the original hydroxyl oxygen when these metal-chelated glycine derivatives are produced. The interaction energy between the glycine and divalent magnesium would be the boundary of one or two amino hydrogens pointing to the hydrogyl oxygen, i.e., the ,170.3 kcal/mol of binding energy is a critical point. Similar intramolecular proton transfer has also been predicted for those DTM ion-chelated glycine systems; however, that in the gas state has not been observed in the monovalent metal ion-coordinated glycine systems. The binding energy between some monovalent TM ion and the glycine is similar to that of the glycine,Ba2+, which has the lowest binding strength among these DAEM,ion chelated glycine complexes. The difference among them only lies in the larger electrostatic and polarized effects in the latter, which favor the stability of the zwitterionic glycine form in the gas phase. According to these observations, we predict that the zwitterionic glycine would exist in the field of two positive charges in the gas phase. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 205,214, 2003 [source] A comparative study of the relationship between pension plans and individual savings in Asian countries from an institutional point of viewINTERNATIONAL JOURNAL OF SOCIAL WELFARE, Issue 4 2010Mann Hyung Hur Hur MH. A comparative study of the relationship between pension plans and individual savings in Asian countries from an institutional point of view Int J Soc Welfare 2010: 19: 379,389 © 2009 The Author, Journal compilation © 2009 Blackwell Publishing Ltd and the International Journal of Social Welfare. This study identifies various saving plans used as alternative pension plans in Asian countries and examines the extent to which these saving plans contribute to their pension schemes. Data were collected from six Asian countries: China, Hong Kong, Japan, Korea, Singapore and Taiwan. The comparison concentrates on an examination of differences and similarities in individual countries' privately managed pension schemes and saving plans. This study suggests that a pension system does not have to be a privately managed plan to encourage individual savings. A critical point for individual savings was avoiding a defined benefit plan. On the basis of these findings, a typology of relationships between second and third pillars and provident funds and incentive systems for individual savings was developed. [source] Critical opalescence points to thermodynamic instability: relevance to small-angle X-ray scattering of resorcinol,formaldehyde gel formation at low pHJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2008Cedric J. Gommes During the formation at low pH of resorcinol,formaldehyde gels with a structure in the micrometre range, small-angle X-ray scattering exhibits a non-monotonic intensity variation as a function of reaction time. The data are analyzed in terms of scattering by statistical fluctuations of polymer concentration, the amplitude of which is maximal close to the critical point for phase separation between polymer and solvent. The data do not carry any morphological information, but they unambiguously show that the driving force of the gel formation is a thermodynamic instability of the polymerizing solution. [source] New techniques for indexing: N-TREOR in EXPOJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2000Angela Altomare Indexing of a powder diffraction pattern is still a critical point in procedures aiming at solving crystal structures from powder data. New code has been associated to the program TREOR90 in order to define an efficient peak search procedure, to modify the crystallographic decisions coded into TREOR90 to make it more exhaustive, to refine the selected unit cell automatically, and to make the entire procedure user friendly, via a graphical interface. The new program, called N-TREOR, has been integrated into the package EXPO to create a suite of programs able to provide a structural model from the analysis of the experimental pattern. N-TREOR is also available as a stand-alone program. [source] The Results of Probe Technique for Transatrial Repair of Tetralogy of FallotJOURNAL OF CARDIAC SURGERY, Issue 6 2002Ahmet Turan Yilmaz M.D. The most critical point in transatrial repair of TOF is infundibular dissection. Right atrial approach provides better surgical exposure for parietal extension of the infundibular septum when compared to a right ventricular approach. However, it is not always easy to determine the localization and amount of muscle bundles to be resected and this surgical maneuver requires experience. Methods: Nineteen patients were reviewed who had repair of isolated TOF by this technique from 1993 to 2001. The mean age of patients was 5 ± 2 years . Transatrial-transpulmonary approach was performed for all patients. To make the infundibular muscle-bundle resection easier and to determine the localization and amount of muscle bundle to be resected, we placed a Hegar dilator into the right ventricle through pulmonary arteriotomy. The muscle bundles between the dilator and the anterior leaflet annulus of the tricuspid valve were totally excised until the intraventricular part of the dilator and pulmonary annulus became completely visible. The area between the Hegar dilator and the margins of the ventricular septal defect (VSD) was left untouched. None of the patients had transannular patch. Tricuspid valve detachment in order to improve the exposure was done in 11 patients. All patients were followed up in our clinic at regular six-month intervals by echocardiography. Results: There was no early or late mortality nor reoperation for residual VSD or residual right ventricle (RV) outflow obstruction. All patients were in NYHA class I. RV on the echocardiography was spared late dilatation and had a good late functional status. Eighteen patients had no or mild pulmonary regurgitation. One patient who had undergone tricuspid anterior leaflet detachment showed mild tricuspid insufficiency. Conclusions: On the basis of hemodynamic outcomes, this procedure for elective repair of TOF in selected cases gives excellent early and mid-term results.(J Card Surg 2002;17:490-494) [source] Inspirations and aspirations of exemplarian action researchJOURNAL OF COMMUNITY & APPLIED SOCIAL PSYCHOLOGY, Issue 6 2003Harry Coenen Abstract As a methodology aimed to focus social scientific theorizing on actual social problems and examine new directions and guidelines for emancipation and empowerment, action research is based on a joint learning process of researchers and researched. The model of exemplarian action research tries to capture how this learning process can develop in practice. Before describing this model and its emancipatory aspirations, the authors sketch the theoretical inspirations of the model of exemplarian action research. They then go on to focus on the relationship between researcher and the researched party, particularly on the principles of reciprocal adequacy and explicitness which are necessary both from an epistemologically and critical point of view. The article concludes by outlining some aspects in which exemplarian action research can be distinguished from pragmatic action research and by emphasizing that it does not stand for a post-modern position, but for a reflexive attitude that hopes to contribute to bringing us beyond a half-modern society. Copyright © 2003 John Wiley & Sons, Ltd. [source] EXTRACTION YIELD OF SOLUBLE PROTEIN AND MICROSTRUCTURE OF SOYBEAN AFFECTED BY MICROWAVE HEATINGJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2006IL CHOI ABSTRACT A laboratory-scale microwave (MW)-assisted extraction system was constructed and compared with a conventional shaking water bath regarding the extraction of soluble proteins in soybeans. Dynamic reaction was monitored by response surface methodology in the MW-assisted extraction system. The yield of soluble protein increased until either temperature (T) or water/solid (W/S) ratio reached an optimum point (60.1C, 12.6 mL/g), and then decreased with further increase of T or W/S ratio. In addition, the yield of soluble protein increased with time within a range of 30 min, and no critical point was observed. The molecular mass of soluble protein was distributed from 19.3 to 81.3 kDa estimated by sodium dodecyl sulfate,polyacrylamide gel electrophoresis. Scanning electron microscopy showed the destruction of the microstructure of soybean cells, which increased the extraction of soluble soy protein. [source] Determination of cubic equation of state parameters for pure fluids from first principle solvation calculationsAICHE JOURNAL, Issue 8 2008Chieh-Ming Hsieh Abstract A new method for estimation of parameters in cubic equations of state from ab initio solvation calculations is presented. In this method, the temperature-dependent interaction parameter a(T) is determined from the attractive component of solvation free energy, whereas the volume parameter b is assumed to be that of solvation cavity. This method requires only element-specific parameters, i.e., atomic radius and dispersion coefficient, and nine universal parameters for electrostatic and hydrogen-bonding interactions. The equations of state (EOS) parameters so determined allow the description of the complete fluid phase diagram, including the critical point. We have examined this method using the Peng,Robinson EOS for 392 compounds and achieved an accuracy of 43% in vapor pressure, 17% in liquid density, 5.4% in critical temperature, 11% in critical pressure, and 4% in critical volume. This method is, in principle, applicable to any chemical species and is especially useful for those whose experimental data are not available. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Oestrogen Regulates the Expression and Function of Dopamine Transporters in Astrocytes of the Nigrostriatal SystemJOURNAL OF NEUROENDOCRINOLOGY, Issue 9 2007S. Karakaya Dopamine is actively and specifically eliminated from the extracellular space by astrocytes and neurones through dopamine transporters (DAT) and, afterwards, either recycled into vesicles or metabolised. The availability of dopamine reflects a critical point in the regulation of dopamine activity within the nigrostriatal circuit under normal and pathological conditions. From previous studies, we know that oestrogen regulates the efficacy of dopaminergic neurones at the synaptic level and improves dopamine function during Parkinson's disease. Accordingly, we investigated the contribution of local astroglial for extracellular dopamine elimination and the impact of oestrogen on DAT expression and activity. Using neonatal striatal and midbrain astrocyte cultures, we could demonstrate that astrocytes possess a specific dopamine uptake machinery and express DAT at considerable levels. The application of 17,-oestradiol decreased the expression of DAT by 80% and 60% in midbrain and striatal astroglia cultures, respectively. The unspecific dopamine transporters (OCT3, VMAT2) were not detected in astroglia. Functionally, oestrogen exposure inhibited the clearance of dopamine from the extracellular space by 45% and 35% compared to controls in midbrain and striatal astroglia, respectively. The effect on DAT expression and activity was completely antagonised by the oestrogen receptor antagonist ICI 182 780. In conclusion, our data suggest that the positive reinforcement of dopamine transmission under physiological conditions and the alleviative impact of oestrogen under pathological conditions may be the result of a decline in DAT expression and therefore delayed dopamine uptake by astroglia. [source] Solution technique for pure-component phase equilibria near the critical pointAICHE JOURNAL, Issue 4 2006L. N. Stapley Abstract An iterative technique is presented for determining pure-component phase equilibrium that essentially does not depend on initiation. The technique uses both the real and the complex conjugate root information obtained from the analytical solution to cubic equations of state to extend substantially the domain of convergence. The technique is robust and effective close to the critical point. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Sufficiency proof of (V,Vc)3 = 0 at the critical pointAICHE JOURNAL, Issue 5 2001Vicente N. Hernandez-Valencia No abstract is available for this article. [source] Reliable computation of mixture critical pointsAICHE JOURNAL, Issue 1 2001Benito A. Stradi The determination of critical points of mixtures is important for both practical and theoretical reasons in modeling phase behavior, especially at high pressure. This article presents the first completely reliable method for locating all the critical points of a given mixture. The method also verifies the nonexistence of a critical point if a mixture of a given composition does not have one. The methodology used is based on interval analysis, in particular an interval Newton/generalized bisection algorithm providing a mathematical and computational guarantee that all mixture critical points are located. The procedure is initialization-independent and thus requires no a priori knowledge of the number of mixture critical points or their approximate locations. The technique is illustrated using several example problems involving cubic equation-of-state models; however, the technique is for general purpose and can be applied in connection with other thermodynamic models. [source] Hydrogen bonding strength,measures based on geometric and topological parameters,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2004awomir Janusz Grabowski Abstract Different methods of estimating H-bond strength are presented. The studies are based on the results of MP2/6,311++G** calculations and the binding energies are corrected for the basis set superposition error (BSSE). The wavefunctions were further applied to localize bond critical points and ring critical points. The characteristics based on the Bader theory are also applied as indicators and measures of hydrogen bonding. This study compares samples of different compounds. The H-bond strength measures such as the proton,acceptor distance (H···Y), the length of the proton donating bond, the electron density at H···Y bond critical point, the H-bond energy and others are analysed. The case of the intramolecular hydrogen bonding is also analysed, and its special characteristics are given. Copyright © 2003 John Wiley & Sons, Ltd. [source] Thermodynamic Properties and Phase Diagram for the System MoO2,TiO2JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2008K. Thomas Jacob The activity of molybdenum dioxide (MoO2) in the MoO2,TiO2 solid solutions was measured at 1600 K using a solid-state cell incorporating yttria-doped thoria as the electrolyte. For two compositions, the emf was also measured as a function of temperature. The cell was designed such that the emf is directly related to the activity of MoO2 in the solid solution. The results show monotonic variation of activity with composition, suggesting a complete range of solid solutions between the end members and the occurrence of MoO2 with a tetragonal structure at 1600 K. A large positive deviation from Raoult's law was found. Excess Gibbs energy of mixing is an asymmetric function of composition and can be represented by the subregular solution model of Hardy as follows The temperature dependence of the emf for two compositions is reasonably consistent with ideal entropy of mixing. A miscibility gap is indicated at a lower temperature with the critical point characterized by Tc (K)=1560 and. Recent studies indicate that MoO2 undergoes a transition from a monoclinic to tetragonal structure at 1533 K with a transition entropy of 9.91 J·(mol·K),1. The solid solubility of TiO2 with rutile structure in MoO2 with a monoclinic structure is negligible. These features give rise to a eutectoid reaction at 1412 K. The topology of the computed phase diagram differs significantly from that suggested by Pejryd. [source] Characterization of Ethylene Copolymers with Liquid Chromatography and Melt Rheology MethodsMACROMOLECULAR SYMPOSIA, Issue 1 2009Yefim Brun Abstract Summary: Melt rheology and polymer chromatography methods were applied to characterize molecular heterogeneities in products of free radical copolymerization of ethylene with methyl acrylate and vinyl acetate comonomers performed in continuously stirred tank and tubular reactors. We found that the ethylene,vinyl acetate copolymers made in both reactors had similar linear viscoelastic properties typical to branched products of the high pressure process. But the ethylene,methyl acrylate copolymers obtained in the tubular reactor had unusually high melt viscosity at low shear rate and much lower onset of shear thinning despite the narrower molecular weight distribution and the lower overall amount of long-chain branches compare to their autoclave counterparts with similar average molecular weight and chemical composition. Using interaction polymer chromatography method called gradient elution at critical point of adsorption we found that ethylene-acrylate copolymers from the tubular reactor had very broad chemical composition distribution, which was consistent with a significant difference in reactivity ratios between ethylene and acrylate comonomers. Such chemical composition heterogeneity can be a reason for the observed unusual rheological properties of these copolymers. [source] Solubility islands for polymer blends , a new option to homogenize incompatible polymers?MACROMOLECULAR SYMPOSIA, Issue 1 2003Attila R. Imre Abstract Experimental results of liquid-liquid phase equilibrium in a polydisperse blend of two polyalkylsiloxane are presented here. The UCST has an unusual pressure dependence: pressure induced miscibility at moderate pressures and pressure induced immiscibility at higher pressures, above a double critical point. The cloud point curve has two maxima in (concentration, temperature) as well as in (concentration, pressure) space. Approaching the double critical point, the high and low pressure branches of the cloud point curve merge and in a certain stage of this merging, they form a miscibility island located inside the two-phase region. Islands of this kind can give us a new tool to mix virtually immiscible blends. [source] | ||||||||||||||||||||||||||||||||||||||||||||||