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Similar Behaviour (similar + behaviour)
Selected AbstractsThe Reaction of (Bipyridyl)palladium(II) Complexes with Thiourea , Influence of DNA and Other Polyanions on the Rate of ReactionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2005Matteo Cusumano Abstract [Pd(bipy)(py)2](PF6)2 reacts stepwise with excess thiourea to give [Pd(tu)4](PF6)2. The kinetics of the second step, which refers to the replacement of bipyridyl in [Pd(bipy)(tu)2](PF6)2, have been studied in water and in the presence of calf thymus DNA, sodium polyriboadenylate, sodium polyvinylsulfonate or sodium polymetaphosphate at 25 °C and pH = 7 and a fixed sodium chloride concentration. The reaction follows a first order course and a plot of kobs against [thiourea]2 affords a straight line with a small intercept. DNA inhibits the process without altering the rate law. The kobs values decrease systematically on increasing the DNA concentration eventually tending to a limiting value. The values are larger at higher ionic strengths and the other polyanions show similar behaviour. The influence of DNA on the kinetics can be related to steric inhibition caused by noncovalent binding with the complex. Upon interaction with DNA, [Pd(bipy)(tu)2]2+ gives rise to immediate spectroscopic changes in the UV/Vis region as well as induced circular dichroism suggesting that the complex, like similar platinum(II) and palladium(II) species of bipyridyl, intercalates with the double helix. Such a type of interaction hampers the attack of the nucleophile at the metal centre inhibiting the reaction. The decrease in the rate of ligand substitution upon decreasing salt concentration but at a given DNA concentration is due to the influence of ionic strength on the complex,DNA interaction. The reactivity inhibition by single-stranded poly(A), polyvinylsulfonate or polymetaphosphate can be accounted for in terms of self-aggregation of the complex induced by the polyanion. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Material stiffness, branching pattern and soil matric potential affect the pullout resistance of model root systemsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2007S. B. Mickovski Summary Understanding of the detailed mechanisms of how roots anchor in and reinforce soil is complicated by the variability and complexity of both materials. This study controlled material stiffness and architecture of root analogues, by using rubber and wood, and also employed real willow root segments, to investigate the effect on pullout resistance in wet and air-dry sand. The architecture of model roots included either no laterals (tap-root) or a single pair at two different locations (herringbone and dichotomous). During pullout tests, data on load and displacement were recorded. These studies were combined with Particle Image Velocimetry (PIV) image analysis of the model root-soil system at a transparent interface during pullout to increase understanding of mechanical interactions along the root. Model rubber roots with small stiffness had increasing pullout resistance as the branching and the depth of the lateral roots increased. Similarly, with the stiff wooden root models, the models with lateral roots embedded deeper showed greatest resistance. PIV showed that rubber model roots mobilized their interface shear strength progressively whilst rigid roots mobilized it equally and more rapidly over the whole root length. Soil water suction increased the pullout resistance of the roots by increasing the effective stress and soil strength. Separate pullout tests conducted on willow root samples embedded in sand showed similar behaviour to the rigid model roots. These tests also demonstrated the effect of the root curvature and rough interface on the maximum pullout resistance. [source] Characterization of carbonic anhydrase from Neisseria gonorrhoeaeFEBS JOURNAL, Issue 6 2001Björn Elleby We have investigated the steady state and equilibrium kinetic properties of carbonic anhydrase from Neisseria gonorrhoeae (NGCA). Qualitatively, the enzyme shows the same kinetic behaviour as the well studied human carbonic anhydrase II (HCA II). This is reflected in the similar pH dependencies of the kinetic parameters for CO2 hydration and the similar behaviour of the kinetics of 18O exchange between CO2 and water at chemical equilibrium. The pH profile of the turnover number, kcat, can be described as a titration curve with an exceptionally high maximal value of 1.7 × 106 s,1 at alkaline pH and a pKa of 7.2. At pH 9, kcat is buffer dependent in a saturable manner, suggesting a ping-pong mechanism with buffer as the second substrate. The ratio kcat/Km is dependent on two ionizations with pKa values of 6.4 and 8.2. However, an 18O-exchange assay identified only one ionizable group in the pH profile of kcat/Km with an apparent pKa of 6.5. The results of a kinetic analysis of a His66,Ala variant of the bacterial enzyme suggest that His66 in NGCA has the same function as a proton shuttle as His64 in HCA II. The kinetic defect in the mutant can partially be overcome by certain buffers, such as imidazole and 1,2-dimethylimidazole. The bacterial enzyme shows similar Ki values for the inhibitors NCO,, SCN, and N3, as HCA II, while CN, and the sulfonamide ethoxzolamide are considerably weaker inhibitors of the bacterial enzyme than of HCA II. The absorption spectra of the adducts of Co(II)-substituted NGCA with acetazolamide, NCO,, SCN,, CN, and N3, resemble the corresponding spectra obtained with human Co(II)-isozymes I and II. Measurements of guanidine hydrochloride (GdnHCl)-induced denaturation reveal a sensitivity of the CO2 hydration activity to the reducing agent tris(2-carboxyethyl)phosphine (TCEP). However, the A292/A260 ratio was not affected by the presence of TCEP, and a structural transition at 2.8,2.9 m GdnHCl was observed. [source] An inverse cascade model for self-organized complexity and natural hazardsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2005Gleb Yakovlev SUMMARY The concept of self-organized complexity evolved from the scaling behaviour of several cellular automata models, examples include the sandpile, slider-block and forest-fire models. Each of these systems has a large number of degrees of freedom and shows a power-law frequency-area distribution of avalanches with N,A,, and ,, 1. Actual landslides, earthquakes and forest fires exhibit a similar behaviour. This behaviour can be attributed to an inverse cascade of metastable regions. The metastable regions grow by coalescence which is self-similar and gives power-law scaling. Avalanches sample the distribution of smaller clusters and, at the same time, remove the largest clusters. In this paper we build on earlier work (Gabrielov et al.) and show that the coalescence of clusters in the inverse cascade is identical to the formation of fractal drainage networks. This is shown analytically and demonstrated using simulations of the forest-fire model. [source] Neutron Activation Analysis Applied to the Determination of Heavy Metals and Other Trace Elements in Sediments from Sepetiba Bay (RJ), BrazilGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2-3 2001Fàbio Pellegatti analyse par activation neutronique; métaux lourds; éléments en traces; sédiments marins In this work, instrumental neutron activation analysis (INAA) was applied to the determination of the elements As, Ba, Br, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Nd, Rb, Sc, Sm, Ta, Tb, Th, U, Yb, Zn in twenty eight bottom sediment samples from Sepetiba Bay, Rio de Janeiro, Brazil. With the concentration data obtained, contour maps were prepared, by using Kriging method, to show the spatial distribution of the studied elements in the Bay. The elements Co, Cr, Cs, Fe, Sc, Ta and Zn showed similar behaviour in the sediments, with higher concentrations along the northern coast of the bay, where the fluvial water inputs are concentrated. The distribution of U, rare earth elements and Ba in the Bay indicates that these elements are not deposited as contaminants. Dans ce travail, les éléments suivants, As, Ba, Br, Ce, Co, Cr, Cs, Eu, Fe, Hf, La Lu, Nd, Rb, Sc, Sm, Ta, Tb, Th, U, Yb et Zn ont été analysés par activation neutronique instrumentale dans vingt huit sédiments de fond de la baie de Sepetiba, Rio de Janeiro, Brésil. Par krigeage et à partir des concentrations obtenues, nous avons établi des cartes de la répartition spatiale des éléments étudiés dans la baie. Co, Cr, Cs, Fe, Sc, Ta et Zn ont des comportements similaires dans les sédiments, avec des concentrations plus importantes le long de la côte nord de la baie, oú les apports en eau fluviale sont concentrés. La distribution en U, Terres Rares et Ba indique que ces éléments ne sont pas déposés comme polluants dans la baie. [source] Lipid and protein changes in chilled sea salmon (Pseudopercis semifasciata): effect of previous rosemary extract (Rossmarinus officinalis L.) applicationINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2009Valeria Tironi Summary The aim of this work was to analyse the effect of rosemary extract application (200 and 500 ppm) on lipid oxidation, colour and protein modifications during the chilled storage (1.0 ± 0.7 °C) of sea salmon (Pseudopercis semifasciata). Lipid oxidation and ,3-22:6 fatty acid content modification were prevented by the addition of rosemary extract. Analysis of interaction between lipid oxidation products and proteins by fluorescence showed no relationship between their temporal changes in the aqueous phase and the lipid oxidation evolution since a similar behaviour was observed in both absence and presence of antioxidant. Protein extractability, sodium dodecyl sulphate-polyacrylamide gel electrophoresis, differential scanning calorimetry and lysine content determinations revealed no differences between muscle untreated or treated with rosemary. Fluorescent compounds evolution in organic phase would be in relation with the appearance of lipid oxidation products. In addition, rosemary extract partially prevented the loss of red colour in chilled muscle. Although protein alterations could not be prevented, rosemary extract shows to be a promissory antioxidant in sea salmon muscle. [source] Differences in polymeric proteins among grains in spring wheat spikesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2006A Andersson Abstract A uniform amount and size distribution of polymeric proteins within grains in a spike might determine the stability of wheat quality. Two cultivars were grown to maturity in solution culture in a climate chamber. Nitrogen (N) in the form of nitrate was added daily and replaced with 15N before harvest. Plants were harvested during grain development. Protein composition and relationships of labelled N in grains from different spikelets within the spike were determined. Higher percentages of large unextractable polymeric proteins (%-LUPP) and total unextractable polymeric proteins (%-TUPP) were found in the lower- and uppermost spikelets in the spike compared with the middle ones for cv. WL, but not for cv. Sport. Both cultivars showed variations in the percentage of large unextractable monomeric proteins (%-LUMP) and total SDS-extractable protein (Tote) in the spikelets within the spike. The amount of total SDS-unextractable protein (Totu) did not vary for either of the cultivars. The spikelets within the spike showing high and low %-LUMP and Tote at maturity showed a similar behaviour shortly after flowering in cv. WL, but not in cv. Sport. The N concentration of SDS and sonicated extracts varied along the spikelets of the spike for both cultivars. The atom-% excess 15N decreased in cv. Sport SDS-extractable and -unextractable proteins and cv. WL albumins + globulins, gliadins and glutenins from grains at different spikelet positions along the spike. Copyright © 2005 Society of Chemical Industry [source] Nonlinear modelling of periodic threshold autoregressions using TsmarsJOURNAL OF TIME SERIES ANALYSIS, Issue 4 2002PETER A. W. LEWIS We present new methods for modelling nonlinear threshold-type autoregressive behaviour in periodically correlated time series. The methods are illustrated using a series of average monthly flows of the Fraser River in British Columbia. Commonly used nonlinearity tests of the river flow data in each month indicate nonlinear behaviour in certain months. The periodic nonlinear correlation structure is modelled nonparametrically using TSMARS, a time series version of Friedman's extended multivariate adaptive regression splines (MARS) algorithm, which allows for categorical predictor variables. We discuss two methods of using the computational algorithm in TSMARS for modelling and fitting periodically correlated data. The first method applies the algorithm to data from each period separately. The second method models data from all periods simultaneously by incorporating an additional predictor variable to distinguish different behaviour in different periods, and allows for coalescing of data from periods with similar behaviour. The models obtained using TSMARS provide better short-term forecasts for the Fraser River data than a corresponding linear periodic AR model. [source] Functional specialization and differential regulation of short-chain carboxylic acid transporters in the pathogen Candida albicansMOLECULAR MICROBIOLOGY, Issue 6 2010Neide Vieira Summary The major fungal pathogen Candida albicans has the metabolic flexibility to assimilate a wide range of nutrients in its human host. Previous studies have suggested that C. albicans can encounter glucose-poor microenvironments during infection and that the ability to use alternative non-fermentable carbon sources contributes to its virulence. JEN1 encodes a monocarboxylate transporter in C. albicans and we show that its paralogue, JEN2, encodes a novel dicarboxylate plasma membrane transporter, subjected to glucose repression. A strain deleted in both genes lost the ability to transport lactic, malic and succinic acids by a mediated mechanism and it displayed a growth defect on these substrates. Although no significant morphogenetic or virulence defects were found in the double mutant strain, both JEN1 and JEN2 were strongly induced during infection. Jen1-GFP (green fluorescent protein) and Jen2-GFP were upregulated following the phagocytosis of C. albicans cells by neutrophils and macrophages, displaying similar behaviour to an Icl1-GFP fusion. In the murine model of systemic candidiasis approximately 20,25% of C. albicans cells infecting the kidney expressed Jen1-GFP and Jen2-GFP. Our data suggest that Jen1 and Jen2 are expressed in glucose-poor niches within the host, and that these short-chain carboxylic acid transporters may be important in the early stages of infection. [source] The sizes of disc galaxies in intermediate-redshift clustersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2007S. P. Bamford ABSTRACT We examine how the location of star formation within disc galaxies depends on environment at intermediate redshift. This is achieved by comparing emission-line (rem) and rest-frame B -band (rB) scalelengths for matched samples of 50 field and 19 cluster, star-forming, disc galaxies, with 0.25 ,z, 1.0 and MB,,19.5 mag. We find that at a given rB the majority of our cluster galaxies have rem smaller than those in the field, by 25 per cent on average. These results are compared with studies of local galaxies, which find a very similar behaviour. From the relations of rem and rB versus B -band absolute magnitude (MB) we infer that the difference between the intermediate- z cluster and field samples is mostly attributable to variation in rem at a given MB, while the rB versus MB relation is similar for the two samples. [source] Monitoring cytotoxic tumour treatment response by diffusion magnetic resonance imaging and proton spectroscopyNMR IN BIOMEDICINE, Issue 1 2002Risto A. Kauppinen Abstract Exposure of tumours to anti-cancer drugs, gene or radiation therapy consistently leads to an increase in water diffusion in the cases expressing favourable treatment response. The diffusion change coincides cytotoxic cell eradication and precedes volume reduction in drug or gene therapy-treated experimental tumours. Interestingly, the recent studies from human brain tumour patients undergoing chemotherapy show similar behaviour of diffusion, suggesting important application for MRI in patient management. In this review observations from diffusion MRI and MRS in the tumours during cytotoxic treatment are summarized and the cellular mechanisms affecting molecular mobility are discussed in the light of tissue microenvironmental and microdynamic changes. Copyright © 2002 John Wiley & Sons, Ltd. [source] Behaviour of sulcotrione and mesotrione in two soilsPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 1 2008Hanène Chaabane Abstract The behaviour of sulcotrione, a recently introduced triketone herbicide, in various soil types was studied under laboratory conditions. In particular, degradation and sorption processes were examined on Ghent and Perpignan soils. Kinetics showed that the degradation of sulcotrione was influenced by biotic and/or abiotic factors. Half-lives ranged between 45 and 65 days. Among the degradation compounds identified were 1,3-cyclohexanedione (CHD) and 2-chloro-4-mesyl benzoic acid (CMBA), previously described as hydrolysis products, and, under special conditions, a derivative of phenylheptanoic acid (PHD). This new degradation product suggested that sulcotrione could follow two possible pathways in the soil, as in water. During the sorption study, a moderate retention of sulcotrione and CMBA relative to CHD and PHD, which were highly adsorbed whatever the soil type, was reported. Experiments carried out under the same conditions for sulcotrione and mesotrione, another triketone herbicide recommended in maize culture, made it possible to compare the two triketones and to conclude that they exhibited relatively similar behaviour in the soil, i.e. that their leaching potential needs to be properly addressed and risks evaluated. Copyright © 2007 Society of Chemical Industry [source] Structural study of NaNO2 embedded into porous glassPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007E. Rysiakiewicz-Pasek Abstract Temperature-dependent Raman study of NaNO2 confined within porous glass with a pore size of 46 nm has been performed. It is demonstrated that the bandwidths and frequencies of the Raman bands as a function of temperature show similar behaviour, but not identical, as those observed for bulk NaNO2. This result indicates that the first-order phase transition mechanism is only slightly modified by embedding NaNO2 into the porous glass. It seems that formation of "premelted state" is not significant in the studied material, at least up to 40-50 K above Tc. At higher temperatures, however, a significant increase of bandwidth of the 1326 cm,1 band is observed, which could indicate appearance of "premelted" state. The dielectric measurements are consistent with this view since they show large increase of dielectric permittivity above 480 K, well below the NaNO2 melting temperature (554 K). (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Angular switching of the linear polarization of the emission in InGaAs microcavitiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2005A. Amo Abstract The angular dependence of the degree of linear polarization of the emission is presented for an InGaAs microcavity at several detunings. For emission angles (, ) close to the growth direction, polarizations as high as +80% for lower branch polaritons at negative detuning are found. This polarization degree abruptly switches to negative values (up to ,90%) for emission angles outside a narrow cone of about ±2º. A similar behaviour, with smaller values of the polarization, is found at 0 and positive detunings. The relation between these effects and cavity birefringence is discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparative Studies on Mo,Cr,N and Al,Cr,N Coatings Obtained by PVD Dual Magnetron SputteringPLASMA PROCESSES AND POLYMERS, Issue S1 2009Yacine Benlatreche Abstract Recently, several studies have shown that the addition of a secondary element likes Al, Si, etc. to nitride and carbide binary systems such as Ti,N and Cr,N improved their structural and mechanical properties and also their thermal stability. In this study, we realized a comparison between the effects of aluminium or molybdenum addition on the properties of the Cr,N system. The (Cr,Al)N and (Cr,Mo)N films were deposited by RF dual magnetron sputtering. To control the aluminium and molybdenum contents in (Cr,Al)N and in (Cr,Mo)N films, respectively, we modified the Cr, Al and Mo target bias. The structural, morphological and composition analyses of the deposited films were carried out using X-ray diffraction (XRD) and SEM equipped with an energy dispersive spectroscopy (EDS) microanalysis. The variation of the residual stresses with the Al and Mo contents has been studied using the Newton's rings method. The obtained Al contents in (Cr,Al)N deposited films varied between 0 and 51,at.% while the Mo contents in (Cr,Mo)N layers varied between 0 and 42,at.%. A morphological change from amorphous to columnar films has been observed with the addition of Al in the case of (Cr,Al)N coatings, while all the (Cr,Mo)N films presented a columnar structure. The residual stresses of the (Cr,Mo)N coatings are higher than the (Cr,Al)N ones but they exhibited a similar behaviour for both coatings. [source] Hydrodynamic investigation of bubble-column reactors: effect of column configurationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010Abid Akhtar Abstract Bubble-column reactors are quite popular in the chemical, biochemical and petrochemical industries due to their relatively simple construction, favourable heat and mass transfer properties and low operating cost. Among the various design parameters, column geometry (configuration) has a significant impact on the overall throughput. In this study, an experimental investigation of the bubble-column configuration on its hydrodynamics has been conducted with three different sizes of the column (ID = 10,45 cm). A comparison in terms of the overall gas holdup as well as localised bubble properties is performed using the four-point optical technique and hydrodynamic similarities/dissimilarities are discussed. The study showed that the overall gas holdup was a function of the gas flow rate. For the range of gas velocity investigated (9.5,22.3 cm3/ min), the smaller column had 50,60% more holdup than the bigger column. Localised bubble properties exhibited similar behaviour (i.e. higher values for the smaller column). A comparative study of L/D illustrated an invariant behaviour at a high value of L/D (>5.5). A low L/D (,1.5), however, showed a prominent influence on hydrodynamics. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Comparing methods of determining addition in presbyopesCLINICAL AND EXPERIMENTAL OPTOMETRY, Issue 3 2008Beatriz Antona BSc Background:, The use of plus lenses to compensate for the reduction in the range of accommodation associated with presbyopia, brings the near point of accommodation to a comfortable distance for near visual tasks. Our aim was to compare the tentative near addition determined using the most common procedures with the final addition prescribed in presbyopic patients. Methods:, Sixty-nine healthy subjects with a mean age of 51.0 years (range 40 to 60 years) were studied. Tentative near additions were determined using seven different techniques: dynamic retinoscopy, amplitude of accommodation (AA), age-expected addition, binocular fused cross-cylinder with and without myopisation, near duochrome, and balance of negative and positive relative accommodation. The power of the addition was then refined to arrive at the final addition. Results:, The mean tentative near additions were higher than the final addition for every procedure except for the fused cross-cylinder without initial myopisation and age-expected addition methods. These biases were small in clinical terms (less than 0.25 D) with the exception of the AA procedure (0.34 D). The intervals between the 95% limits of agreement differed substantially and were always higher than ±0.50 D. Conclusions:, All the techniques used displayed similar behaviour and provided a tentative addition close to the final addition. Due to the wide agreement intervals observed, the likelihood of error is high and supports the idea that any tentative addition has to be adjusted according to the particular needs of each patient. Among the methods examined here, we would recommend the age-expected procedure, as this technique produced results that correlated best with the final addition. [source] Testing the accuracy of synthetic stellar librariesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007Lucimara P. Martins ABSTRACT One of the main ingredients of stellar population synthesis models is a library of stellar spectra. Both empirical and theoretical libraries are used for this purpose, and the question about which one is preferable is still debated in the literature. Empirical and theoretical libraries are being improved significantly over the years, and many libraries have become available lately. However, it is not clear in the literature what are the advantages of using each of these new libraries, and how far behind models are compared to observations. Here we compare in detail some of the major theoretical libraries available in the literature with observations, aiming at detecting weaknesses and strengths from the stellar population modelling point of view. Our test is twofold: we compared model predictions and observations for broad-band colours and for high-resolution spectral features. Concerning the broad-band colours, we measured the stellar colour given by three recent sets of model atmospheres and flux distributions, and compared them with a recent UBVRIJHK calibration which is mostly based on empirical data. We found that the models can reproduce with reasonable accuracy the stellar colours for a fair interval in effective temperatures and gravities. The exceptions are (1) the U,B colour, where the models are typically redder than the observations, and (2) the very cool stars in general (V,K, 3). Castelli & Kurucz is the set of models that best reproduce the bluest colours (U,B, B,V) while Gustafsson et al. and Brott & Hauschildt more accurately predict the visual colours. The three sets of models perform in a similar way for the infrared colours. Concerning the high-resolution spectral features, we measured 35 spectral indices defined in the literature on three high-resolution synthetic libraries, and compared them with the observed measurements given by three empirical libraries. The measured indices cover the wavelength range from ,3500 to ,8700 Å. We found that the direct comparison between models and observations is not a simple task, given the uncertainties in parameter determinations of empirical libraries. Taking that aside, we found that in general the three libraries present similar behaviours and systematic deviations. For stars with Teff, 7000 K, the library by Coelho et al.is the one with best average performance. We detect that lists of atomic and molecular line opacities still need improvement, specially in the blue region of the spectrum, and for the cool stars (Teff, 4500 K). [source] | |||||||||||||||||||