Good Correspondence (good + correspondence)

Distribution by Scientific Domains

Selected Abstracts

Modern pollen,vegetation relationships in subarctic southern Greenland and the interpretation of fossil pollen data from the Norse landnám

J. Edward Schofield
Abstract Aim, The objective of this paper is to explore the relationships that exist between vegetation and modern pollen rain in the open, largely treeless landscape of subarctic Greenland. The implications of these results for the interpretation of fossil pollen assemblages from the time of the Norse landnám are then examined. Location, The study area is the sheep farming district of Qassiarsuk in the subarctic, subcontinental vegetational and climatic zone of southern Greenland (61° N, 45° W). Between 1000,1500 this region was contained within the Norse Eastern Settlement. Methods, Detrended Correspondence Analysis (DCA) of harmonized plant,pollen data sets is used to compare plant cover in 64 vegetation quadrats with pollen assemblages obtained from moss polsters at matching locations. Presence/absence data are also used to calculate indices of association, over- and under-representation for pollen types. Results, Good correspondence between paired vegetation,pollen samples occurs in many cases, particularly in locations where Salix glauca,Betula glandulosa dwarf shrub heath is dominant, and across herbaceous field boundaries and meadows. Pollen samples are found to be poor at reflecting actual ground cover where ericales or Juniperus communis are the locally dominant shrubs. Dominant or ubiquitous taxa within this landscape (Betula, Salix and Poaceae) are found to be over-represented in pollen assemblages, as are several of the ,weeds' generally accepted as introduced by the Norse settlers. Main conclusions, Due to their over-representation in the pollen rain, many of the Norse apophytes and introductions (e.g. Rumex acetosa and R. acetosella) traditionally used to infer human activity in Greenland should be particularly sensitive indicators for landnám, allowing early detection of Norse activity in fossil assemblages. Pteridophyte spores are found to be disassociated with the ground cover of ferns and clubmosses, but are over-represented in pollen assemblages, indicating extra-local or regional sources and long residence times in soil/sediment profiles for these microfossils. A pollen record for Hordeum -type registered in close proximity to a field containing barley suggests that summer temperatures under the current climatic regime are, at least on occasion, sufficient to allow flowering. [source]

Spatially resolved evaluation of power losses in industrial solar cells by illuminated lock-in thermography

Joerg Isenberg
Abstract The principles of a recently introduced measurement technique for power losses in solar cells, illuminated lock-in thermography (ILT), are reviewed. The main advantage of ILT over dark lock-in Thermography (DLT) is measurement under realistic operational conditions of solar cells. The main focus of this paper is to demonstrate the wide range of applications of ILT in identifying the causes of power losses in solar cells. For this purpose different evaluation methods are presented. A method for the evaluation of improvement potentials within a given cell technology is demonstrated. It is shown that different types of series resistance may be localized. Small areas of recombination losses (e.g., grain boundaries) can routinely be detected, which is not possible in dark lock-in thermography. Good correspondence with light-beam-induced current images is found. A realistic evaluation of the impact of recombination losses on solar cell performance is demonstrated on two examples. Finally, process- or treatment-induced recombination losses are investigated. In summary ILT is shown to be an extremely powerful tool in localizing, identifying and quantifying power losses of solar cells under realistic illumination conditions. Copyright © 2004 John Wiley & Sons, Ltd. [source]

The influence of large convective eddies on the surface-layer turbulence

S. S. Zilitinkevich
Abstract Close to the surface large coherent eddies consisting of plumes and downdraughts cause convergent winds blowing towards the plume axes, which in turn cause wind shears and generation of turbulence. This mechanism strongly enhances the convective heat/mass transfer at the surface and, in contrast to the classical formulation, implies an important role of the surface roughness. In this context we introduce the stability-dependence of the roughness length. The latter is important over very rough surfaces, when the height of the roughness elements becomes comparable with the large-eddy Monin,Obukhov length. A consistent theoretical model covering convective regimes over all types of natural surfaces, from the smooth still sea to the very rough city of Athens, is developed; it is also comprehensively validated against data from measurements at different sites and also through the convective boundary layer. Good correspondence between model results, field observations and large-eddy simulation is achieved over a wide range of surface roughness lengths and convective boundary-layer heights. Copyright © 2007 Royal Meteorological Society [source]

Influence of dispersion length on leaching calculated with PEARL, PELMO and PRZM for FOCUS groundwater scenarios

Jos JTI Boesten
Abstract Harmonisation of the assessment of pesticide leaching to groundwater for EU registration is desirable to minimise confusion in the decision-making process at EU level. Recently, the FOCUS groundwater scenarios have been developed for three chromatographic models (PEARL, PELMO and PRZM) to increase this harmonisation. This study investigates the role of dispersion parameterisation in explaining the cause of the differences in pesticide leaching calculated by these models. PEARL describes dispersion via a physical parameter, ie the dispersion length. PELMO and PRZM simulate dispersion via a numerical procedure which generates an effective dispersion length equal to 0.5 times the thickness of the numerical compartments. The hypothesis was tested that the difference in the dispersion length input parameter (ie 5 cm for PEARL and about 2.5 cm for PELMO and PRZM) is a major cause of the difference in calculated leaching. It was tested whether results of PEARL calculations with a dispersion length of 2.5 cm corresponded much better to results of PELMO or PRZM than results of PEARL calculations with a dispersion length of 5 cm. This was done by calculations for one substance and all nine FOCUS scenarios and by calculations for a range of substances and two FOCUS scenarios (Châteaudun and Sevilla). All calculations were for winter wheat and an application at 1 day before emergence. Both tests showed that reduction of the dispersion length from 5 to 2.5 cm in PEARL led to a much better correspondence between PEARL and either PELMO or PRZM. Hence the hypothesis was supported. It is likely that harmonisation of the dispersion length in the FOCUS groundwater scenarios would reduce the differences in calculated leaching between PEARL and PELMO or PRZM considerably for part of these scenarios. Published in 2004 for SCI by John Wiley & Sons, Ltd. [source]

Raman spectroscopic and X-ray investigation of stressed states in diamond-like carbon films

R. Krawietz
Abstract The non-destructive characterization of intrinsic stress is very important to evaluate the reliability of devices based on diamond-like carbon (DLC) films. Whereas the only requirement for the X-ray diffraction method is a crystalline state of specimen, Raman spectroscopic stress analysis is restricted to materials showing intensive and sharp Raman peaks. On the other hand, Raman spectroscopy offers the possibility to measure stress profiles with lateral resolution of about 1 micron. The results of stress measurements in DLC films using both X-ray diffraction and Raman spectroscopy are found in very good correspondence. Mean stress in carbon films consisting of very small crystallites on silicon substrates has been determined by measuring and fitting the stress profiles in the substrate near artificial vertical film edges. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Comparison of the modified three-rail shear test and the [(+45°,,45°)]ns tensile test for pure shear fatigue loading of carbon fabric thermoplastics

ABSTRACT The (three)-rail shear test is rarely considered for testing of fibre-reinforced composites under pure shear fatigue loading conditions because of all experimental difficulties. However, in this article, a carbon fabric-reinforced PPS is tested using a modified three-rail shear test setup. The results are compared with [(+45°,,45°)]4s tensile tests with good correspondence. All fatigue experiments were done with R= 0 and the influence of maximum shear stress and frequency is investigated. It can be concluded that an increase in maximum shear stress decreases fatigue lifetime, whereas an increase in frequency increases the lifetime. Before failure, a sudden increase in both temperature and permanent deformation could be detected. Creep tests yielded that the occurring deformation is mainly due to the fatigue loading, rather than due to creep phenomena. [source]

Crustal structure of the Newfoundland rifted continental margin from constrained 3-D gravity inversion

J. Kim Welford
ABSTRACT The rifting history of the Atlantic continental margin of Newfoundland is very complex and so far has been investigated at the crustal scale primarily with the use of 2-D seismic surveys. While informative, the results generated from these surveys cannot easily be interpreted in a regional sense due to their sparse sampling of the margin. A 3-D gravity inversion of the free air data over the Newfoundland margin allows us to generate a 3-D density anomaly model that can be compared with the seismic results and used to gain insight into regions lacking seismic coverage. Results of the gravity inversion show good correspondence with Moho depths from seismic results. A shallowing of the Moho to 12 km depth is resolved on the shelf at the northern edge of the Grand Banks, in a region poorly sampled by other methods. Comparisons between sediment thickness and crustal thickness show deviations from local isostatic compensation in locations which correlate with faults and rifting trends. Such insights must act as constraints for future palaeoreconstructions of North Atlantic rifting. [source]

An empirical model of carbon fluxes in Russian tundra

Dmitri G. Zamolodchikov
Summary This study presents an empirical model based on a GIS approach, which was constructed to estimate the large-scale carbon fluxes over the entire Russian tundra zone. The model has four main blocks: (i) the computer map of tundra landscapes; (ii) data base of long-term weather records; (iii) the submodel of phytomass seasonal dynamics; and (iv) the submodel of carbon fluxes. The model uses exclusively original in situ diurnal CO2 flux chamber measurements (423 sample plots) conducted during six field seasons (1993,98). The research sites represent the main tundra biome landscapes (arctic, typical, south shrub and mountain tundras) in the latitudinal diapason of 65,74°N and longitudinal profile of 63°E,172°W. The greatest possible diversity of major ecosystem types within the different landscapes was investigated. The majority of the phytomass data used was obtained from the same sample plots. The submodel of carbon fluxes has two dependent [GPP, Gross Respiration (GR)] and several input variables (air temperature, PAR, aboveground phytomass components). The model demonstrates a good correspondence with other independent regional and biome estimates and carbon flux seasonal patterns. The annual GPP of Russian tundra zone for the area of 235 × 106 ha was estimated as ,485.8 ± 34.6 × 106 tC, GR as +474.2 ± 35.0 × 106 tC, and NF as ,11.6 ± 40.8 × 106 tC, which possibly corresponds to an equilibrium state of carbon balance during the climatic period studied (the first half of the 20th century). The results advocate that simple regression-based models are useful for extrapolating carbon fluxes from small to large spatial scales. [source]

Reliability and validity of the Junior Temperament and Character Inventory

Klaus Schmeck
Abstract The Junior Temperament and Character Inventory (JTCI) was developed to assess the temperament (,novelty seeking', ,harm avoidance', ,reward dependence', ,persistence') and character (,self-directedness', ,cooperativeness', ,self-transcendence') dimensions of Cloninger's biosocial model of personality in children and adolescents. The psychometric properties of the JTCI are presented. We used the German version of JTCI in a clinical sample of 188 adolescent psychiatric patients (aged 12 to 18 years) and in a non-referred sample of 706 German adolescents of the same age range. Aspects of reliability and validity are discussed. We subjected the JTCI to confirmatory factor analysis and were able to replicate the temperament and character scales of the original TCI. The internal consistency of the scales was satisfactory with the exception of ,reward dependence' and ,persistence'. Construct validity was supported by good correspondence of JTCI dimensions with related constructs. Psychometric properties of the German version of JTCI are very promising. Results yield strong support for Cloninger's psychobiological theory. Copyright © 2001 Whurr Publishers Ltd. [source]

Studies on glass transition temperature of mono and bilayer protein films plasticized by glycerol and olive oil

Babak Ghanbarzadeh
Abstract Thermomechanical and thermal properties of whey protein, maize prolamin protein (zein), and the laminated whey protein,zein films were studied. The dynamic mechanical (thermal) analysis (DMTA) results showed that the single zein film had higher Tg than single whey protein and zein,whey laminated films. The shift in the Tg values of films from 31.2°C in whey protein film and 88.5°C in the zein film to 82.8°C in the laminated whey protein,zein films may be implied some interaction formation between the two polymers. The small tan , peaks were observed at ,50°C in zein,glycerol films and at ,22.37°C in the whey protein films and can be related to ,-relaxation phenomena or presence of glycerol rich region in polymer matrix. Zein-olive oil and zein,whey protein,olive oil films showed tan , peaks corresponded the Tg values at 113.8, and 92.4°C, respectively. Thus, replacing of glycerol with olive oil in film composition increased Tg. A good correspondence was obtained when DSC results were compared with the tan , peaks in DMTA measurements. DSC thermograms suggested that plasticizers and biopolymers remained a homogeneous material throughout the cooling and heating cycle. The results showed that Tg of zein,glycerol films predicted by Couchman and Karasz equation is very close to value obtained by DSC experiments. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Role of Citrobacter amalonaticus and Citrobacter farmeri in dissimilatory perchlorate reduction

Nirmala Bardiya
The article deals with the novel physiological function of dissimilatory perchlorate reduction by strains JB101 and JB109 isolated from a laboratory-enriched mixed consortium originating from a sewage treatment facility. The biochemical and physiological data of the strains showed good correspondence with members of the family Enterobacteriaceae. The partial 16S rDNA sequence of the strains JB101 and JB109 had similarity of 99.8% to Citrobacter amalonaticus and 98% to Citrobacter farmeri, respectively. The results inferred the possibility of Citrobacter spp. to form an important group of dissimilatory perchlorate reducers among the , subclass of Proteobacteria, since the majority of the perchlorate reducers belong to two monophyletic groups, Dechloromonas and Dechlorosoma in , subclass. The perchlorate-grown Citrobacter strains preferred perchlorate to nitrate as an electron acceptor unlike most of the reported dissimilatory perchlorate reducers. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Lipase-catalyzed ethanolysis of soybean oil in a solvent-free system using central composite design and response surface methodology

Rafael Costa Rodrigues
Abstract BACKGROUND: In this work we describe the synthesis of ethyl esters, commonly known as biodiesel, using refined soybean oil and ethanol in a solvent-free system catalyzed by lipase from Thermomyces lanuginosus. Central composite design and response surface methodology (RSM) were employed to optimize the biodiesel synthesis parameters, which were: reaction time, temperature, substrate molar ratio, enzyme content, and added water, measured as percentage of yield conversion. RESULTS: The optimal conditions obtained were: temperature, 31.5 °C; reaction time, 7 h; substrate molar ratio, 7.5:1 ethanol:soybean oil; enzyme content, 15% (g enzyme g,1 oil); added water, 4% (g water g,1 oil). The experimental yield conversion obtained under these conditions was 96%, which is very close to the maximum predicted value of 94.4%. The reaction time-course at the optimal values indicated that 5 h was necessary to obtain high yield conversions. CONCLUSION: A high yield conversion was obtained under the optimized conditions, with relative low enzyme content and short time. Comparison of predicted and experimental values showed good correspondence, implying that the empirical model derived from RSM can be used to adequately describe the relationship between the reaction parameters and the response (yield conversion) in lipase-catalyzed biodiesel synthesis. Copyright © 2008 Society of Chemical Industry [source]

On a test bench for studying lubrication in a spherical bearing: simulations and experimental validation

N.P. Belfiore
In this paper a test bench dedicated to the analysis of a lubricated spherical pair is presented. The experimental set-up has been used to validate a numerical code that has been developed by the authors in order to simulate a complex lubricated spherical pair that affects the reliability of a novel continuous variable transmission (CVT). The test bench is modular and can be adapted to other lubricated pairs, either cylindrical or spherical. The stand is equipped with an I/O control card and allows the on-line acquisition of some important parameters. As for the numerical code, the finite-difference method has been used to solve the indirect problem in the lubricated spherical pad, under the condition of hydrodynamic regime, with externally pressurized inlets. Two simulators are needed since the physical properties of the test bench and the real system are different. The one that simulates the behavior of the spherical pair in the test stand has been used to ascertain the numeric approach prediction capability. Indeed, the experimental tests gave results which are in very good correspondence with the numerical predictions. Hence, the second simulator, which has been tailored on the particular spherical pair the CVT is equipped with, gained reliability in predicting the behavior of the real system under different load and speed conditions. These predictions have been useful in achieving new insights into the novel CVT, which, under this new light, has been criticized by making the point that its range of application in automotive is, at the actual state of the art, rather limited, in spite of a high intrinsic complexity. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Larval habitats and seasonal abundance of Culicoides biting midges found in association with sheep in northern Sardinia, Italy

Between January 2005 and December 2006, the larval habitats and seasonal abundances of 21 species of Culicoides (Diptera: Ceratopogonidae) found in association with livestock on a farm in northern Sardinia were studied. Culicoides were collected using two light traps (one placed in a sheep shed and the other near water ponds) and reared from mud collected in and along the margins of a small and a large water pond. The mammalophilic Culicoides imicola Kieffer and Culicoides newsteadi Austen were the most prevalent (>95%) of 20 species in the sheep shed, whereas the ornithophilic Culicoides univittatus Vimmer, Culicoides sahariensis Kieffer, Culicoides festivipennis Kieffer, Culicoides circumscriptus Kieffer and Culicoides cataneii Clastrier were most abundant in the traps set at the ponds (73%) and in 16 species of Culicoides reared from laboratory-maintained mud samples retrieved from three microhabitats (a non-vegetated pond shoreline, 20 cm above a pond shoreline, the shoreline of a secondary, permanently inundated, grass-covered pool). The species reared most abundantly from along the pond shoreline were C. festivipennis, C. circumscriptus and C. sahariensis, whereas those most prevalent at the grassed pool were C. cataneii and C. festivipennis. C. imicola was found to breed preferentially in mud 20 cm above the pond shoreline, whereas C. newsteadi was restricted almost entirely to the grassed pool, which had a high organic matter content. Using the light trap and adult emergence data, the seasonal abundance patterns of the eight species of Culicoides were determined. In general, there was good correspondence between light trap catches and emergence trends. Well-defined emergence peaks indicate four or five generations for C. festivipennis and C. circumscriptus and three generations for C. cataneii, C. newsteadi and Culicoides jumineri Callot & Kremer. The emergence trends for C. imicola and C. sahariensis were unimodal, but, because they stretched over several months, indicated that a number of overlapping generations had occurred. Adults of C. imicola were reared and captured only sporadically in the first half of the year, gradually building to a peak in autumn. Conversely, C. newsteadi was reared throughout the year and displayed three clearly defined peaks (in winter, spring and autumn); captures of C. newsteadi in the light traps peaked in May,June and again to a lesser extent in autumn. In Sardinia the late seasonal peak in the abundance of C. imicola occurs in synchrony with outbreaks of bluetongue (BT) in sheep, which is consistent with earlier findings elsewhere in the Mediterranean basin and in Africa that it is the principal vector of bluetongue virus (BTV). Although the status of C. newsteadi as a vector of BTV is not known, its low-level presence in winter and heightened abundances in spring may provide a pathway along which the virus can overwinter. [source]

Radiative torques: analytical model and basic properties

A. Lazarian
ABSTRACT We attempt to get a physical insight into grain alignment processes by studying basic properties of radiative torques (RATs). For this purpose we consider a simple toy model of a helical grain that reproduces well the basic features of RATs. The model grain consists of a spheroidal body with a mirror attached at an angle to it. Being very simple, the model allows analytical description of RATs that act upon it. We show a good correspondence of RATs obtained for this model and those of irregular grains calculated by ddscat. Our analysis of the role of different torque components for grain alignment reveals that one of the three RAT components does not affect the alignment, but induces only for grain precession. The other two components provide a generic alignment with grain long axes perpendicular to the radiation direction, if the radiation dominates the grain precession, and perpendicular to magnetic field, otherwise. The latter coincides with the famous predictions of the Davis,Greenstein process, but our model does not invoke paramagnetic relaxation. In fact, we identify a narrow range of angles between the radiation beam and the magnetic field, for which the alignment is opposite to the Davis,Greenstein predictions. This range is likely to vanish, however, in the presence of thermal wobbling of grains. In addition, we find that a substantial part of grains subjected to RATs gets aligned with low angular momentum, which testifies that most of the grains in diffuse interstellar medium do not rotate fast, that is, rotate with thermal or even subthermal velocities. This tendency of RATs to decrease grain angular velocity as a result of the RAT alignment decreases the degree of polarization, by decreasing the degree of internal alignment, that is, the alignment of angular momentum with the grain axes. For the radiation-dominated environments, we find that the alignment can take place on the time-scale much shorter than the time of gaseous damping of grain rotation. This effect makes grains a more reliable tracer of magnetic fields. In addition, we study a self-similar scaling of RATs as a function of ,/aeff. We show that the self-similarity is useful for studying grain alignment by a broad spectrum of radiation, that is, interstellar radiation field. [source]

Infrared spectrum of potassium-cationized triethylphosphate generated using tandem mass spectrometry and infrared multiple photon dissociation

Gary S. Groenewold
Tandem mass spectrometry and wavelength-selective infrared photodissociation were used to generate an infrared spectrum of gas-phase triethylphosphate cationized by attachment of K+. Prominent absorptions were observed in the region of 900 to 1300,cm,1 that are characteristic of phosphate PO and POR stretches. The relative positions and intensities of the IR absorptions were reproduced well by density functional theory (DFT) calculations performed using the B3LYP functional and the 6-31+G(d), 6-311+G(d,p) and 6-311++G(3df,2pd) basis sets. Because of good correspondence between experiment and theory for the cation, DFT was then used to generate a theoretical spectrum for neutral triethylphosphate, which in turn accurately reproduces the IR spectrum of the neat liquid when solvent effects are included in the calculations. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Screening of chondrogenic factors with a real-time fluorescence-monitoring cell line ATDC5-C2ER: Identification of sorting nexin 19 as a novel factor

Akinori Kan
Objective To establish a cell culture system for noninvasive and real-time monitoring of chondrogenic differentiation in order to screen for chondrogenic factors. Methods The optimum reporter construct transfected into chondrogenic ATDC5 cells was selected by a luciferase reporter assay and fluorescence analysis during cultures with insulin. The established cell line was validated according to its fluorescence following stimulation with SOX proteins, bone morphogenetic protein 2 (BMP-2), or transforming growth factor , (TGF,) and was compared with the level of messenger RNA for COL2A1 as well as with the degree of Alcian blue staining. Screening of chondrogenic factors was performed by expression cloning using a retroviral expression library prepared from human tracheal cartilage. The expression pattern of the identified molecule was examined by in situ hybridization and immunohistochemistry. Functional analysis was performed by transfection of the identified gene, the small interfering RNA, and the mutated gene. Results We established an ATDC5 cell line with 4 repeats of a highly conserved enhancer ligated to a COL2A1 basal promoter and the DsRed2 reporter (ATDC5-C2ER). Fluorescence was induced under the stimulations with SOX proteins, BMP-2, or TGF,, showing good correspondence to the chondrogenic markers. Screening using the ATDC5-C2ER system identified several chondrogenic factors, including sorting nexin 19 (SNX19). SNX19 was expressed in the limb cartilage of mouse embryos and in the degraded cartilage of adult mouse knee joints during osteoarthritis progression. The gain-of-function and loss-of-function analyses revealed a potent chondrogenic activity of SNX19. Conclusion We established the ATDC5-C2ER system for efficient monitoring of chondrogenic differentiation by fluorescence analysis, and we identified a novel chondrogenic factor (SNX19) using this system. This system will be useful for elucidating the molecular network of chondrogenic differentiation. [source]

SCT reaction kinetics model and diffusion for p.c. combustion in TGA

Pei-Fang Fu
Abstract Recently, the process of char burnout is extensively concerned. Global model used widely cannot predict the extent of char burnout at the later burning stage. For the need of predicting the burnout degree in industrial pulverized coal (p.c.) fired furnace by making use of the experimental data from such as thermogravimetry analysis (TGA) and drop tube furnace, based on the simple collision theory (SCT) of chemical reaction kinetics, the SCT model is educed. The p.c. combustion is considered as the results of strike and oxidation of oxygen molecules on the surface of p.c. particles, and the frequency of effective strike was determined by Boltzmann factor. Strike and oxidation occur on the oxygen accessible specific surface area (OASA). Chemical regime controlled is at temperature below 1200 K, and molecules diffusion regime controlled is at the temperature above 1600 K, at which OASA corresponds to the specific surface area with pore diameter more than 38 nm of p.c particles in coal-fired boiler. The OASA of p.c. particles increases with the char burning, for the particles swells, shrinks and cracks. The burning rates calculated based on SCT model have shown good correspondence with experimental data reported. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Seasonal and interannual variability of Siberian river discharge in the Laptev Sea inferred from stable isotopes in modern bivalves

BOREAS, Issue 2 2003
Stable oxygen and carbon isotope profiles from modern bivalve shells were investigated in order to reconstruct short-term hydrographical changes in the river-shelf system of the Laptev Sea. Oxygen isotopic profiles obtained from the aragonitic species Astarte borealis exhibit amplitude cycles interpreted as annual hydrographical cycles. These records reflect the strong contrast between summer and winter bottom water conditions in the Laptev Sea. The seasonal variations in ,18O are mainly controlled by the riverine freshwater discharge during summer with 0.5, per salinity unit. Corrected for a defined species-dependent fractionation offset of -0.37,, time-dependent salinity records were reconstructed from these ,18O profiles. They indicate a good correspondence to seasonal hydrographic changes and synoptical data. Persistent trends with shell growth towards more negative ,13C values are observed in all specimens and appear to be related to metabolic changes of the bivalves during ontogeny. In contrast, short-term fluctuations are likely linked to seasonal variabilities of the river water outflow patterns and enhanced phytoplankton productivity during summer. This is corroborated by a clear watermass-related distinction of the various ,13C records made on the basis of water depth and distance from the riverine source. [source]

Prediction of Tyrosinase Inhibition Activity Using Atom-Based Bilinear Indices

CHEMMEDCHEM, Issue 4 2007
Yovani Marrero-Ponce Prof.
Abstract A set of novel atom-based molecular fingerprints is proposed based on a bilinear map similar to that defined in linear algebra. These molecular descriptors (MDs) are proposed as a new means of molecular parametrization easily calculated from 2D molecular information. The nonstochastic and stochastic molecular indices match molecular structure provided by molecular topology by using the kth nonstochastic and stochastic graph-theoretical electronic-density matrices, Mk and Sk, respectively. Thus, the kth nonstochastic and stochastic bilinear indices are calculated using Mk and Sk as matrix operators of bilinear transformations. Chemical information is coded by using different pair combinations of atomic weightings (mass, polarizability, vdW volume, and electronegativity). The results of QSAR studies of tyrosinase inhibitors using the new MDs and linear discriminant analysis (LDA) demonstrate the ability of the bilinear indices in testing biological properties. A database of 246 structurally diverse tyrosinase inhibitors was assembled. An inactive set of 412 drugs with other clinical uses was used; both active and inactive sets were processed by hierarchical and partitional cluster analyses to design training and predicting sets. Twelve LDA-based QSAR models were obtained, the first six using the nonstochastic total and local bilinear indices and the last six with the stochastic MDs. The discriminant models were applied; globally good classifications of 99.58 and 89.96,% were observed for the best nonstochastic and stochastic bilinear indices models in the training set along with high Matthews correlation coefficients (C) of 0.99 and 0.79, respectively, in the learning set. External prediction sets used to validate the models obtained were correctly classified, with accuracies of 100 and 87.78,%, respectively, yielding C values of 1.00 and 0.73. This subset contains 180 active and inactive compounds not considered to fit the models. A simulated virtual screen demonstrated this approach in searching tyrosinase inhibitors from compounds never considered in either training or predicting series. These fitted models permitted the selection of new cycloartane compounds isolated from herbal plants as new tyrosinase inhibitors. A good correspondence between theoretical and experimental inhibitory effects on tyrosinase was observed; compound CA6 (IC50=1.32,,M) showed higher activity than the reference compounds kojic acid (IC50=16.67,,M) and L -mimosine (IC50=3.68,,M). [source]

Highlight of a compensation effect between filler morphology and loading on dynamic properties of filled rubbers

Franck Sosson
Abstract This investigation highlighted the equivalence between carbon black (CB) loading and structure influences on dynamic mechanical properties in the linear behavior of several filled synthetic rubber compounds. Different morphologies (specific surface area and structure) of CB incorporated at different loadings were formulated to modulate the filler-rubber matrix interphase content, usually named "tightly bound rubber." Both reinforcement level and tightly bound rubber content were measured on each compound by dynamic mechanical analysis (DMTA) and by Soxhlet extraction and thermogravimetry (TGA) respectively. Then, a systematic description of their evolution was made against CB loading and morphology. These evolutions were attributed to the hydrodynamic effect which could be evaluated by the effective filler volume fraction. A new parameter , is defined, representing the effective filler volume fraction for each compound and it was calculated on the basis of experimental parameters. Results show good correspondences between , included both the hydrodynamic effects of the filled carbon black rubbers and dynamic mechanical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]