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Contradictory Conclusions (contradictory + conclusion)
Selected AbstractsHexafluoroisopropanol as size exclusion chromatography mobile phase for Polyamide 6JOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2004Raniero Mendichi Abstract The present study deals with the use of hexafluoroisopropanol (HFIP) as size exclusion chromatography (SEC) mobile phase for polyamide 6 (PA6). Contradictory conclusions relating to the use of HFIP as SEC mobile phase for polyamides are found in the literature. By using a multi-detector SEC apparatus equipped with on-line viscometer and multi-angle light scattering we have studied the chromatographic artifacts and the validity of the universal calibration (UC) in HFIP for different PA6 samples (hydrolytic and anionic, monofunctional or bifunctional activator). Appropriate SEC columns and optimized experimental conditions allow most of the chromatographic artifacts to be avoided, even in neat HFIP. The use of a salt in the mobile phase, namely 0.01 M tetraethylammonium nitrate (TEAN), slightly increases the elution volume for both PA6 and PMMA polymers. Under the right conditions, the UC substantially holds for PA6. The validity of the UC is not linked to the presence of TEAN in the mobile phase. With some PA6 samples, namely those anionically synthesized using a bifunctional activator, aggregation becomes a problem and the molar mass in neat HFIP is overestimated. Addition of TEAN prevents any aggregation of the above anionically synthesized PA6. In contrast, the use of a different salt, namely potassium trifluoroacetate, increases the extent of aggregation. [source] Bootstrap-based bandwidth choice for log-periodogram regressionJOURNAL OF TIME SERIES ANALYSIS, Issue 6 2009Josu Arteche Abstract., The choice of the bandwidth in the local log-periodogram regression is of crucial importance for estimation of the memory parameter of a long memory time series. Different choices may give rise to completely different estimates, which may lead to contradictory conclusions, for example about the stationarity of the series. We propose here a data-driven bandwidth selection strategy that is based on minimizing a bootstrap approximation of the mean-squared error (MSE). Its behaviour is compared with other existing techniques for optimal bandwidth selection in a MSE sense, revealing its better performance in a wider class of models. The empirical applicability of the proposed strategy is shown with two examples: the widely analysed in a long memory context Nile river annual minimum levels and the input gas rate series of Box and Jenkins. [source] Blockade of CCR4 in a humanized model of asthma reveals a critical role for DC-derived CCL17 and CCL22 in attracting Th2 cells and inducing airway inflammationALLERGY, Issue 7 2009F. Perros Background:, As Th2 type lymphocytes orchestrate the cardinal features of allergic asthma, inhibiting their recruitment to the lungs could be of therapeutic benefit. Although human Th2 cells express the CCR4 chemokine receptor and increased production of CCR4 ligands has been found in asthmatic airways, studies in animals have reached contradictory conclusions on whether blocking this pathway would be beneficial. Objective:, As a lack of efficacy might be due to differences between mouse and man, we readdressed this question using a humanized severe combined immunodeficiency model of asthma. Methods:, Mice received peripheral blood mononuclear cells from house dust mite (HDM) allergic asthmatic patients and then underwent bronchial challenge with HDM. Results:, This resulted in marked allergic inflammation and bronchial hyper-reactivity. Administration of CCR4 blocking antibody abolished the airway eosinophilia, goblet cell hyperplasia, IgE synthesis and bronchial hyperreactivity. In this chimeric system, human CD11c+ dendritic cells (DCs) were the predominant source of CCR4 ligands, suggesting that DC-derived chemokines attract Th2 cells. In separate experiments using human DCs, in vitro exposure to HDM of DCs from HDM allergic patients but not healthy controls caused CCL17 and CCL22 release that resulted in chemoattraction of polarized human Th2 cells in a CCR4-dependent way. Conclusions:, Taken together, our data provide proof of concept that CCR4 blockade inhibits the salient features of asthma and justify further clinical development of CCR4 antagonists for this disease. [source] Microwaves in Heterogeneous Gas-Phase Catalysis: Experimental and Numerical ApproachesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2009T. Durka Abstract This review paper focuses on the effects of microwave irradiation on heterogeneous gas phase catalytic reaction systems. Both experimental and modeling approaches are discussed. The currently available methods for temperature measurements in the microwave heating of solid particles are critically examined. The existence of microwave-created temperature gradients in beds of solid particles is discussed. The not fully established mechanism of catalyst (nano)particle heating and imperfect temperature measurement techniques implicate that different effects are often observed and contradictory conclusions are drawn. For further progress here, the development of accurate and possibly non-invasive techniques for local temperature measurements under microwave irradiation is needed. [source] | ||||||||||