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Extensive Study (extensive + study)
Selected AbstractsEstimation of seismic drift and ductility demands in planar regular X-braced steel framesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2007Theodore L. Karavasilis Abstract This paper summarizes the results of an extensive study on the inelastic seismic response of X-braced steel buildings. More than 100 regular multi-storey tension-compression X-braced steel frames are subjected to an ensemble of 30 ordinary (i.e. without near fault effects) ground motions. The records are scaled to different intensities in order to drive the structures to different levels of inelastic deformation. The statistical analysis of the created response databank indicates that the number of stories, period of vibration, brace slenderness ratio and column stiffness strongly influence the amplitude and heightwise distribution of inelastic deformation. Nonlinear regression analysis is employed in order to derive simple formulae which reflect the aforementioned influences and offer a direct estimation of drift and ductility demands. The uncertainty of this estimation due to the record-to-record variability is discussed in detail. More specifically, given the strength (or behaviour) reduction factor, the proposed formulae provide reliable estimates of the maximum roof displacement, the maximum interstorey drift ratio and the maximum cyclic ductility of the diagonals along the height of the structure. The strength reduction factor refers to the point of the first buckling of the diagonals in the building and thus, pushover analysis and estimation of the overstrength factor are not required. This design-oriented feature enables both the rapid seismic assessment of existing structures and the direct deformation-controlled seismic design of new ones. A comparison of the proposed method with the procedures adopted in current seismic design codes reveals the accuracy and efficiency of the former. Copyright © 2007 John Wiley & Sons, Ltd. [source] Symptomatic Epilepsies Imitating Idiopathic Generalized EpilepsiesEPILEPSIA, Issue 2005Hirokazu Oguni Summary:, The diagnosis of idiopathic generalized epilepsies (IGEs) is not generally difficult if one follows the clinical and electroencephalogram (EEG) definitions of each subsyndrome that constitutes IGEs. In contrast, symptomatic epilepsies develop based on organic brain lesions and are easily diagnosed by the presence of developmental delay, neurologic abnormalities, and a characteristic seizure and EEG pattern. However, in clinical practice, it is sometimes difficult to differentiate IGEs from symptomatic epilepsies, especially when the clinical course from the onset of epilepsy is too short to exhibit typical clinical and EEG findings of either epilepsy type, or when patients with symptomatic epilepsies have atypical features that imitate the clinical characteristics of IGEs. The neurodegenerative or metabolic disorders at times start during the clinical course with epileptic seizures and later show typical neurologic abnormalities. The newly recognized metabolic disorder of glucose transporter type 1 deficiency syndrome (Glut-1 DS) may start with myoclonic seizures at an age of less than 1 year and imitate benign myoclonic epilepsy in infancy early in the clinical course. Progressive myoclonus epilepsies (PMEs) that develop at 1,4 years of age at times imitate epilepsy with myoclonic-astatic seizures with respect to the presence of astatic seizures and an epileptic encephalopathic EEG pattern. In addition, young children with focal cortical dysplasia may also have similar clinical and EEG patterns, although the latter may become localized after treatment. Approximately 15% of patients with juvenile myoclonic epilepsy (JME) are resistant to antiepileptic drugs (AEDs) and may require extensive study to make a differential diagnosis from symptomatic epilepsies. PMEs that develop during adolescence may imitate JME early in the clinical course; however, a detailed history and the differentiation between myoclonic seizures and myoclonus would help to distinguish both conditions. The diagnosis of IGEs is very demanding for patients with atypical features with regard to seizure type, EEG findings, and response to appropriate AEDs. [source] [4+2]/HyBRedOx Approach to C -Naphthyl Glycosides: Failure in the Projuglone Series and Reinvestigation of the HyBRedOx SequenceEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2009Lucie Maingot Abstract C -Naphthyl glycosides displaying a 1,5-difunctionality on the naphthalene ring that can undergo oxidation to bromonaphthoquinone are key intermediates in the synthesis of natural C -aryl glycoside analogues. In this area, sugar-modified derivatives are of specific interest, but their synthesis is challenging. The de novo access to such compounds has been investigated through a [4+2] heterocycloaddition route, previously validated in a model series. For this purpose, two new dienophiles, conveniently protected at the phenolic positions, were synthesized. From an extensive study of their reactivity towards a range of 4-hetero-substituted ("prosugar") heterodienes, the expected heteroadducts were stereoselectively obtained in acceptable yields. Application of the hydroboration/reduction/oxidation sequence did not afford the target C -glycosides from the reduced adducts. The negative effect of the conformational bias of the substrate on this tandem reaction is discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Understanding the binding properties of an unusual metal-binding protein , a study of bacterial frataxinFEBS JOURNAL, Issue 16 2007Chiara Pastore Deficiency of the small mitochondrial protein frataxin causes Friedreich's ataxia, a severe neurodegenerative pathology. Frataxin, which has been highly conserved throughout evolution, is thought to be involved in, among other processes, Fe,S cluster formation. Independent evidence shows that it binds iron directly, although with very distinct features and low affinity. Here, we have carried out an extensive study of the binding properties of CyaY, the bacterial ortholog of frataxin, to different divalent and trivalent cations, using NMR and X-ray crystallography. We demonstrate that the protein has low cation specificity and contains multiple binding sites able to chelate divalent and trivalent metals with low affinity. Binding does not involve cavities or pockets, but exposed glutamates and aspartates, which are residues that are unusual for iron chelation when not assisted by histidines and/or cysteines. We have related how such an ability to bind cations on a relatively large area through an electrostatic mechanism could be a valuable asset for protein function. [source] Generic Strategy of Preparing Fluorescent Conjugated-Polymer-Loaded Poly(DL -lactide- co -Glycolide) Nanoparticles for Targeted Cell ImagingADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Kai Li Abstract A general strategy for the preparation of highly fluorescent poly(DL-lactide- co -glycolide) (PLGA) nanoparticles (NPs) loaded with conjugated polymers (CPs) is reported. The process involves encapsulation of organic-soluble CPs with PLGA using a modified solvent extraction/evaporation technique. The obtained NPs are stable in aqueous media with biocompatible and functionalizable surfaces. In addition, fluorescent properties of the CP-loaded PLGA NPs (CPL NPs) could be fine-tuned by loading different types of CPs into the PLGA matrix. Four types of CPL NPs are prepared with a volume-average hydrodynamic diameter ranging from 243 to 272,nm. The application of CPL NPs for bio-imaging is demonstrated through incubation with MCF-7 breast cancer cells. Confocal laser scanning microscopy studies reveal that the CPL NPs are internalized in cytoplasm around the nuclei with intense fluorescence. After conjugation with folic acid, cellular uptake of the surface-functionalized CPL NPs is greatly enhanced via receptor-mediated endocytosis by MCF-7 breast cancer cells, as compared to that for NIH/3T3 fibroblast cells, which indicates a selective targeting effect of the folate-functionalized CPL NPs in cellular imaging. The merits of CPL NPs, such as low cytotoxicity, high fluorescence, good photostability, and feasible surface functionalization, will inspire extensive study of CPL NPs as a new generation of probes for specific biological imaging and detection. [source] Association and aggregation analysis using kin-cohort designs with applications to genotype and family history data from the Washington Ashkenazi StudyGENETIC EPIDEMIOLOGY, Issue 2 2001Nilanjan Chatterjee Abstract When a rare inherited mutation in a disease gene, such as BRCA1, is found through extensive study of high-risk families, it is critical to estimate not only age-specific penetrance of the disease associated with the mutation, but also the residual effect of family history once the mutation is taken into account. The kin-cohort design, a cross-sectional survey of a suitable population that collects DNA and family history data, provides an efficient alternative to cohort or case-control designs for estimating age-specific penetrance in a population not selected because of high familial risk. In this report, we develop a method for analyzing kin-cohort data that simultaneously estimate the age-specific cumulative risk of the disease among the carriers and non-carriers of the mutations and the gene-adjusted residual familial aggregation or correlation of the disease. We employ a semiparametric modeling approach, where the marginal cumulative risks corresponding to the carriers and non-carriers are treated non-parametrically and the residual familial aggregation is described parametrically by a class of bivariate failure time models known as copula models. A simple and robust two-stage method is developed for estimation. We apply the method to data from the Washington Ashkenazi Study [Struewing et al., 1997, N Engl J Med 336:1401,1408] to study the residual effect of family history on the risk of breast cancer among non-carriers and carriers of specific BRCA1/BRCA2 germline mutations. We find that positive history of a single first-degree relative significantly increases risk of the non-carriers (RR = 2.0, 95% CI = 1.6,2.6) but has little or no effect on the carriers. Genet. Epidemiol. 21:123,138, 2001. © 2001 Wiley-Liss, Inc. [source] Enhanced Light-Harvesting and Photocatalytic Properties in Morph -TiO2 from Green-Leaf BiotemplatesADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Xufan Li Abstract The unique structure of green leaves endows them with an extremely high light-harvesting efficiency. In this work, green leaves are applied as biotemplates to synthesize morph -TiO2. The structural features favorable for light harvesting from the macro- to the nanoscale are replicated in morph -TiO2 through a two-step infiltration process and the N contained in the original leaves is self-doped into the resulting samples. The absorbance intensities within the visible-light range of morph -TiO2 derived from different leaves increase by 103,258% and the band-gap-absorption onsets at the edge of the UV and visible-light range show a red-shift of 25,100,nm compared to those in TiO2 without the template. The photocatalytic activity of morph -TiO2 is also improved, as proven by an electron paramagnetic resonance (EPR) study and degradation of rhodamine dye under irradiation with UV and visible light. The present work, as a new strategy, is of far-reaching significance in learning from nature, driving us to make full use of the most-abundant resources and structure-introduced functions endowed by nature, opening up possibilities for extensive study of the physical and chemical properties of morph -structured oxides and extending their potential for use in applications such as solar cells, photocatalysts, photoelectrical devices, and photoinduced sensors. [source] Chiral and Achiral Crystal StructuresHELVETICA CHIMICA ACTA, Issue 4 2003Howard An extensive study and analysis of the concepts, classification, presentation, and nomenclature of chirality and lack of chirality in crystal structures and their constituents is presented. Oriented crystal structures are classified. The chirality rules for existence of molecular crystal structures are examined and the relation to segmentation and latent symmetry highlighted. The nomenclature of chirality and related terms, and the relationship of chirality to optical activity is covered. The uses and limitations of the Euclidean normalizer are treated. An improved glossary of terms is included. [source] Breeding biology and success of the Bearded Vulture Gypaetus barbatus in the eastern PyreneesIBIS, Issue 2 2003Antoni Margalida We present data from an extensive study of Bearded Vulture Gypaetus barbatus breeding biology in the Pyrenees from 1992 to 1999. Average laying date was 6 January (range 11 December to 12 February, n = 69) with no significant differences between years. Eighty per cent of clutches were of two eggs (n = 20) and average incubation was 54 days (range 52,56, n = 14). Hatching occurred on average between 21 February and 3 March (range 5 February,7 April) and the first and last chicks fledged in 21,27 May and 20 July, respectively. The average chick age at fledging was 123 days (range 103,133, n = 20). Bearded Vulture density increased significantly during the study period. Breeding success and productivity declined apparently as a consequence of the increase in the percentage of breeding failures during incubation and chick rearing, most during the hatching period. The factors that may determine breeding failure and the decline in breeding performance are analysed and management recommendations for more effective conservation measures are discussed. [source] Principles and applications of control in quantum systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 15 2005Hideo Mabuchi Abstract We describe in this article some key themes that emerged during a Caltech/AFOSR Workshop on ,Principles and Applications of Control in Quantum Systems' (PRACQSYS), held 21,24 August 2004 at the California Institute of Technology. This workshop brought together engineers, physicists and applied mathematicians to construct an overview of new challenges that arise when applying constitutive methods of control theory to nanoscale systems whose behaviour is manifestly quantum. Its primary conclusions were that the number of experimentally accessible quantum control systems is steadily growing (with a variety of motivating applications), that appropriate formal perspectives enable straightforward application of the essential ideas of classical control to quantum systems, and that quantum control motivates extensive study of model classes that have previously received scant consideration. Copyright © 2005 John Wiley & Sons, Ltd. [source] Solution theory model for thermophysical properties of refrigerant/lubricant mixturesAICHE JOURNAL, Issue 12 2009Albeiro Restrepo Abstract A general model for predicting the thermophysical properties of refrigerant/lubricant mixtures has been developed based on applicable theory for the excess Gibbs energy of nonideal solutions. In our approach, flexible thermodynamic forms are chosen to describe the properties of both the gas and liquid phases of refrigerant/lubricant mixtures. After an extensive study of models for describing nonideal liquid effects, the Wohl [3]-suffix equations, which have been extensively used in the analysis of hydrocarbon mixtures, have been developed into a general form applicable to mixtures where one component is a polyolester or alkylbenzene lubricant. We have developed a nonideal solution computer code, based on the Wohl model that predicts dew point or bubble point conditions over a wide range of composition and temperature and includes the calculation of the enthalpy and entropy of refrigerant/lubricant mixtures. Our present analysis includes the thermodynamic properties of an ideal solution mixture and the corrections due to nonideal solution behavior. These nonideal solution corrections are based on analysis of the excess Gibbs energy of the mixture. We find that these nonideal solution corrections are small (<4%) for most refrigerant/lubricant mixtures, except at very low temperatures. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Blanching and long-term freezing affect various bioactive compounds of vegetables in different waysJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2003Riitta Puupponen-Pimiä Abstract An extensive study on the effects of blanching/freezing and long-term freezer storage on various bioactive compounds of more than 20 commonly used vegetables was performed. Effects were strongly plant species-dependent. Contents of dietary fibre components either were not affected or increased slightly. Minerals in general were also stable, but some losses of soluble minerals by leaching were observed. Phenolic antioxidants and vitamins were clearly more sensitive. Significant losses (20,30%) of antioxidant activity and total phenolics were detected in many vegetables. A qualitative HPLC profiling method for phenolic antioxidants was developed which proved to be very useful when evaluating the complex behaviour of phenolics during food processing. Up to one-third of vitamin C contents were lost during blanching, and further slight losses were detected during storage. Folic acid turned out to be very sensitive to blanching, with more than half of the vitamin being lost, but was stable during freezer storage. Carotenoids and sterols were not affected by blanching or freezer storage. The usefulness of the applied screening methods for evaluation of the effects of processing on vegetables is shown. Copyright © 2003 Society of Chemical Industry [source] An extensive study of dynamical friction in dwarf galaxies: the role of stars, dark matter, halo profiles and MONDMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006F. J. Sánchez-Salcedo ABSTRACT We investigate the in-spiralling time-scales of globular clusters (GCs) in dwarf spheroidal (dSph) and dwarf elliptical (dE) galaxies, due to dynamical friction (DF). We address the problem of these time-scales having been variously estimated in the literature as much shorter than a Hubble time. Using self-consistent two-component (dark matter and stars) models, we explore mechanisms which may yield extended DF time-scales in such systems in order to explain why dwarf galaxies often show GC systems. As a general rule, dark matter and stars both give a comparable contribution to the dynamical drag. By exploring various possibilities for their gravitational make-up, it is shown that these studies help to constrain the parameters of the dark matter haloes in these galaxies, as well as to test alternatives to dark matter. Under the assumption of a dark halo having a central density core with a typical King core radius somewhat larger than the observed stellar core radius, DF time-scales are naturally extended upwards of a Hubble time. Cuspy dark haloes yield time-scales ,4.5 Gyr, for any dark halo parameters in accordance with observations of stellar line-of-sight velocity dispersion in dSph galaxies. We confirm, after a detailed formulation of the DF problem under the alternative hypothesis of modified Newtonian dynamics (MOND) and in the lack of any dark matter, that due to the enhanced dynamical drag of the stars, the DF time-scales in MOND would be extremely short. Taking the well-measured structural parameters of the Fornax dSph and its GC system as a case study, we conclude that requiring DF time-scales comparable to the Hubble time strongly favours dark haloes with a central core. [source] Comparison of device performance and measured transport parameters in widely-varying Cu(In,Ga) (Se,S) solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2006I. L. Repins Abstract We report the results of an extensive study employing numerous methods to characterize carrier transport within copper indium gallium sulfoselenide (CIGSS) photovoltaic devices, whose absorber layers were fabricated by diverse process methods in multiple laboratories. This collection of samples exhibits a wide variation of morphologies, compositions, and solar power conversion efficiencies. An extensive characterization of transport properties is reported here,including those derived from capacitance,voltage, admittance spectroscopy, deep level transient spectroscopy, time-resolved photoluminescence, Auger emission profiling, Hall effect, and drive level capacitance profiling. Data from each technique were examined for correlation with device performance, and those providing indicators of related properties were compared to determine which techniques and interpretations provide credible values for transport properties. Although these transport properties are not sufficient to predict all aspects of current-voltage characteristics, we have identified specific physical and transport characterization methods that can be combined using a model-based analysis algorithm to provide a quantitative prediction of voltage loss within the absorber. The approach has potential as a tool to optimize and understand device performance irrespective of the specific process used to fabricate the CIGSS absorber layer. Copyright © 2005 John Wiley & Sons, Ltd. [source] Learning Organizations in the Public Sector?PUBLIC ADMINISTRATION REVIEW, Issue 1 2003A Study of Police Agencies Employing Information, Technology to Advance Knowledge In an attempt to reap the purported benefits that "knowledge workers" bring to organizations, many police departments have shifted to a community problem,oriented policing philosophy. Rather than focusing on enforcement and incarceration, this philosophy is based on the dissemination of information to promote a proactive, preventative approach to reduce crime and disorder. In keeping with much of the contemporary literature on the "learning organization" (sometimes called the "knowledge organization"), police departments hope to deter crime through the knowledge benefits that derive from information and its associated technologies. With goals to stimulate productivity, performance, and effectiveness, police departments across the country are employing information technology to turn police officers into problem solvers and to leverage their intellectual capital to preempt crime and neighborhood deterioration. Many public and private organizations are striving to change their operations toward this same concept of the knowledge worker. Information technology is often touted as a vehicle for capturing, tracking, sorting, and providing information to advance knowledge, thus leading to improvements in service,delivery efforts. Based on an extensive study of police departments that have attempted to implement a knowledge,worker paradigm (supported by information technology initiatives), this research explores the feasibility, effectiveness, and limitations of information and technology in promoting the learning organization in the public sector. [source] Influence of population stratification on population-based marker-disease association analysisANNALS OF HUMAN GENETICS, Issue 4 2010Tengfei Li Summary Population-based genetic association analysis may suffer from the failure to control for confounders such as population stratification (PS). There has been extensive study on the influence of PS on candidate gene-disease association analysis, but much less attention has been paid to its influence on marker-disease association analysis. In this paper, we focus on the Pearson ,2 test and the trend test for marker-disease association analysis. The mean and variance of the test statistics are derived under presence of PS, so that the power and inflated type I error rate can be evaluated. It is shown that the bias and the variance distortion are not zero in the presence of both PS and penetrance heterogeneity (PH). Unlike candidate gene-disease association analysis, when PS is present, the bias is not zero no matter whether PH is present or not. This work generalises the published results, where only the fully recessive penetrance model is considered and only the bias is calculated. It is shown that candidate gene-disease association analysis can be treated as a special case of marker-disease association analysis. Consequently, our results extend previous studies on candidate gene-disease association analysis. A simulation study confirms the theoretical findings. [source] The geometry of coexistenceBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2000PRIYANGA AMARASEKARE Understanding the processes that maintain diversity has been the focus of extensive study, yet there is much that has not been integrated into a cohesive framework. First, there is a separation of perspective. Ecological and evolutionary approaches to diversity have progressed in largely parallel directions. Second, there is a separation of emphasis. In both ecology and population genetics, classical theories favour local explanations with emphasis on population dynamics and selection within populations, while contemporary theories favour spatial explanations, with emphasis on population structure and interactions among populations. What is lacking is a comparative approach that evaluates the relative importance of local and spatial processes in maintaining genetic and ecological diversity. I present a framework for diversity maintenance that emphasizes the comparative approach. I use a well-known but little-used mathematical approach, the perturbation theorem for dynamical systems, to identify key points of contact between ecological and population genetic theories of coexistence. These connections provide for a synthesis of several important concepts: population structure (source-sink versus extinction-colonization), spatial heterogeneity (intrinsic versus extrinsic) in fitness and competitive ability, and temporal scales over which local and spatial processes influence diversity. This framework ties together a large and diverse body of theory and data from ecology and population genetics. It yields comparative predictions that can serve as guidelines in biodiversity management. [source] Combined treatment with vitamin E and colchicine in the early stages of Peyronie's diseaseBJU INTERNATIONAL, Issue 6 2003R.M. Prieto Castro Objective To assess the effectiveness of the combination of colchicine and vitamin E (which has anti-fibrotic, anti-mitotic and anti-inflammatory effects) in modifying the early stages of Peyronie's disease, by evaluating pain relief, correction of deformities and plaque size. Patients and methods In all, 45 patients were divided into two groups and treated from January 1998 to November 2001. Their mean (range) age was 53.4 (40,62) years, the time from onset of the disease < 6 months and they had penile deformity of < 30°; no patient had erectile dysfunction. Twenty-two patients were given ibuprofen 400 mg/day for 6 months, whilst 23 received a combination of vitamin E 600 mg/day plus colchicine 1 mg every 12 h. Pain, plaque size and penile deformity were assessed at 6 months. Results There were no statistically significant differences between the groups at baseline in age, time from onset of the disease until the initial evaluation or plaque size. Although the proportion of patients reporting pain relief was higher amongst those receiving colchicine plus vitamin E (91% vs 68%) this was not significantly different, but differences in plaque size and penile curvature were significant. Conclusions The use of colchicine plus vitamin E during the early stages of Peyronie's disease (time from onset < 6 months) in patients with penile curvature of < 30° and no erectile dysfunction is an effective and well-tolerated way to stabilize the disease. A more extensive study is needed, comparing these results with other oral therapies. [source] Progress, Public Health, and Power: Foucault and the Homemakers' Clubs of Saskatchewan,CANADIAN REVIEW OF SOCIOLOGY/REVUE CANADIENNE DE SOCIOLOGIE, Issue 3 2008SCOTT McLEAN De 1911 à 1979, les Homemakers' Clubs de la Saskatchewan ont mobilisé et suivi une étude et une action à grande échelle dans le domaine de la santé publique. Cet article examine comment ces clubs ont poussé des femmes à lutter pour avancer et les ont encouragées à considérer de telles luttes comme étant fondamentales pour bâtir leur propre identité. Les techniques utilisées comprenaient des encouragements à partager des buts, à faire leurs de tels buts, à structurer leur démarche, à rendre compte de leurs pensées et de leurs actions, à récompenser certaines conduites et à lier ces dernières à des causes convaincantes sur le plan émotif. En s'insérant dans un cadre conceptuel foucaldien, cet article apporte une contribution à la compréhension sociologique de la gouvernance et de la formation du sujet. From 1911 to 1979, the Homemakers' Clubs of Saskatchewan mobilized and monitored extensive study and action in the field of public health. This article explores how these clubs exhorted women to strive for progress, and encouraged women to internalize such striving as fundamental to their own identities. The techniques used included encouraging commitment to shared goals, making such goals personal, structuring action, requiring women to report their thoughts and actions, rewarding certain behaviors, and linking those behaviors with emotionally compelling causes. Rooted in a Foucauldian conceptual framework, this article contributes to the sociological understanding of subject formation and governance. [source] Ionic Liquids for Propene-Propane SeparationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2010V. Mokrushin Abstract This paper presents an extensive study on the feasibility of ionic liquids (IL) for the extractive distillation of propene-propane mixtures. A new experimental method for express screening of non-volatile entrainers was elaborated. A series of ILs and their mixtures were screened at ambient temperature and low pressures. The screening results show that every tested IL turns a low boiler propene into a high boiler and the alkene-to-alkane separation factor can be as low as 0.28. The solubility and separation efficiency can be tuned by adjusting the chemical structures of the ions forming the IL. It was found that shortening of the alkyl substituents of the imidazolium ions leads to a decrease in capacity and to an increase in the separation factor. Interestingly, ILs containing nitrile functionalities in either the cation or the anion showed, in our experiments, enhanced separation ability combined with still good capacities. From our thermodynamic measurements, [EMIM][[B(CN)4] was proved to be the most promising candidate. Binary mixtures of ILs were also tested and resulted in separation factors and capacities between the values for the individual ILs. For the most promising candidates, also autoclave measurements at elevated temperatures and pressures were carried out. These experiments indicate that the separation ability decreases with growing temperature and loading. In general, our study definitely proves the high potential of ILs to act as entrainers in the extractive distillation of propene-propane mixtures or for the separation of any other low-boiling alkene-alkane mixture. [source] Exploring the Relation between Amplification and Binding in Dynamic Combinatorial Libraries of Macrocyclic Synthetic Receptors in WaterCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2008Peter Abstract Herein we describe an extensive study of the response of a set of closely related dynamic combinatorial libraries (DCLs) of macrocyclic receptors to the introduction of a focused range of guest molecules. We have determined the amplification of two sets of diastereomeric receptors induced by a series of neutral and cationic guests, including biologically relevant compounds such as acetylcholine and morphine. The host,guest binding affinities were investigated using isothermal titration calorimetry. The resulting dataset enabled a detailed analysis of the relationship between the amplification of selected receptors and host,guest Gibbs binding energies, giving insight into the factors affecting the design, simulation and interpretation of DCL experiments. In particular, two questions were addressed: Is amplification by a given guest selective for the best receptor? And does the best guest induce the largest amplification of a given receptor? Our experimental results and computer simulations showed that the relative levels of amplification of hosts by a guest are well-correlated with their relative affinities, and simulations have confirmed previous observations that amplification can be selective for the best receptor when only modest amounts of guest are used. In contrast, the correlation between guest binding and the extent of amplification of a given receptor across a wide range of guests tends to be poorer, because every guest has its own unique set of affinities for competing receptors in the DCL. This implies that the results of screening a DCL for selective receptors by comparing the response of the mixture to two different guests should be interpreted with caution. DCLs are complex mixtures in which all compounds are connected through a set of equilibria. Obtaining quantitative information about all host,guest binding constants from such systems will require the explicit and simultaneous consideration of all of the main equilibria within a DCL. [source] Stimulatory and inhibitory epitopes in the T cell responses of mice to Der p 1CLINICAL & EXPERIMENTAL ALLERGY, Issue 6 2002A. G. Jarnicki Summary Background The responses of mice to the mite allergen Der p 1 have been used to study the mechanisms of allergic sensitization and the development of new types of immunotherapy. Many of the studies require a knowledge of the T cell epitopes, and because Der p 1 is polymorphic, the effect of natural amino acid substitution in the allergen. The intranasal administration of peptides containing T cell epitopes can induce a mucosal tolerance but it is not known if the major activity is limited to stimulatory peptides and if, as found for autoimmunity, some epitopes are not inhibitory. Objective To determine and compare the sequences of Der p 1 which contain stimulatory epitopes for the high responding H-2b and H-2q mice and the sequences which induce tolerance by intranasal administration of peptides. Methods T cell responses of mice immunized with Der p 1 were measured by in vitro T cell stimulation assays so an extensive study of epitope recognition and intranasal tolerance could be made. Synthetic peptides were used to examine the stimulatory and inhibitory ability of all Der p 1 sequences and to map the major H-2b epitope in detail. This included the effect of the common polymorphic amino acid 124 substitution found within this epitope. Results Three and two regions, respectively, were found to contain stimulatory T cell epitopes for H-2b and H-2q mice. The peptides in these regions were also the most active at inducing intranasal tolerance for the responding haplotype. The correspondence between inhibitory and stimulatory peptides was maintained for the fine mapping of the major H-2b epitope. This was found about a core region of 118,126 which was overlapping but separate to a consensus sequence for the binding of endogeneous peptides. Peptides with alanine at the naturally polymorphic residue 124 stimulated and inhibited responses to Der p 1 more effectively, while peptides with the valine 124 variant were immunogenic but poorly cross-reactive. Conclusions The intranasal administration of peptides representing each of five epitopes recognized by two strains of mice were able to induce mucosal tolerance and the major tolerizing activity was limited to these epitopes. The position of the core major epitope for C57 mice, which differs from a previously predicted epitope, and its specificity for the natural alanine 124 variant is described. [source] | |||||||||||||||||||