bluuebunny/crossref_metadata_2025 huggingface dataset:
Sortir de la classe pour enrichir les savoirs sur l'environnement
Authors: Bailet André , Clavel Françoise , Maglione Anne
Published: June 2010

Salir de la clase para enriquecer los conocimientos sobre el medio.

Podemos elegir el espacio exterior para instruir los alumnos ? Los docentes del colegio, habiendo llevado a menudo sus alumnos fuera de la clase, intentan una reflexión sobre ese sujeto : Fuera de la escuela, los problemas encontrados son complejos, las realidades diversas y las personas diferentes Podemos ver, escuchar, tocar una aproximación sensible del medio. Los aprendizajes se organizan de otra manera que en un cuadro escolar, ponen en juego en todos los participantes aptitudes diversificadas en un contexto donde las disciplinas son llevadas a funcionar de una manera coordenada. Sumergidos en ese "Vivir otra cosa" los alumnos van a encontrar un cierto numero de situaciones en el terreno y luego en la explotación en la clase, que les va a permitir entre otras cosas aprender en ciencias.
Population
Authors: Develay Michel , Ginsburger-Vogel Yvette
Published: June 2010

Population.

The natural populations which make up the elementary structure studied by researchers in ecology are seldom taken into consideration in our teaching : when talking about population in didactical situations, we generally mean a group of individuals of the same species, and the functional implications of the concept are not apparent.

An analysis of the conceptual field shows the complexity of this concept which finds its place in an evolutionist perspective, even if the genetic dimension is not dwelt upon. It is clear moreover that the mastery of the concept's constituent elements entails a more effective understanding of classroom situations in which it is implicitely referred to. In particular all the problems of interactions and equilibrium are clarified and structured when considered in terms of populations dynamics.

Rich and complex, the concept of population constitutes an important level of integration in modern evolutive biology.
Milieu
Authors: Drouin Anne-Marie , Astolfi Jean-Pierre
Published: June 2010

Le concept de Milieu présente la particularité d'être présent de façon implicite dans de nombreux textes scientifiques sans faire l'objet d'une définition précise. Lorsqu'il est employé, on constate une large variabilité de significations, que l'on peut souvent rattacher aux stades successifs de son élaboration historique.

De même, en situation didactique, l'emploi du mot milieu est beaucoup plus fréquent que les séances de classe où sa construction comme concept est travaillée précisément.

On essaiera, après une analyse de contenu de cette notion, de caractériser les obstacles auxquels sa construction se heurte et ¡es étapes possibles de son appropriation. On étudiera en fonction de cette grille de lecture quelques exemples de séances de classe, et l'on proposera de situer les étapes de construction mises en oeuvre.
Relations alimentaires
Authors: Peterfalvi Brigitte , Rumelhard Guy , Vérin Anne
Published: June 2010

Relaciones alimenticias.

La noción de "relaciones alimenticias" es una entrucijada para multiples conceptos. A su nivel de formulación mas simple, se trata de una relación constatada o afirmada entre dos individuos vivantes.

A los niveles de formulación mas elevados, nosotros tenemos conceptos que buscan a modelizar, a representar conjuntos de relaciones de un punto de vista cada vez diferente.

Las palabras mismas, cadena, red, flujo, ciclo se proyectan en una figuración, una imagen que es necesario sobrepasar definiendo el contenido conceptual preciso al cual ellos se refieren.

La dificultad aquí es doble :

- las palabras "relaciones alimenticias" son vaciás. Son un objeto de estudio y lo que se estudia son : sea los factores que juegan sobre estas relaciones, sea las maneras por las cuáles estas relaciones se organizan y evolucionan.

- nada mas frecuente que un estudio de cadena alimenticia a la escuela primaria o al colegio cuando queremos abordar el ecosistema.

La situaciones de clase que llevan sobre este conjunto de conceptos son numerosas pero conducen a adquisiciones puntuales y diversas. Como precisar las organizaciones conceptuales que es posible de construir ?
Echanges thermiques
Authors: Agabra Jacqueline
Published: June 2010

Cet article s'inscrit dans le cadre d'une recherche plus large sur l'enseignement de l'énergie, à l'école élémentaire, dans les collèges et dans les lycées. On y trouvera une tentative d'utilisation de l'analyse historigue et épistémologigue du concept de chaleur pour mieux comprendre les représentations des enfants, mais aussi, en s'appuyant sur les travaux des enseignants du groupe de recherche réalisés en classe, des propositions d'objectifs et d'activités tenant compte des difficultés rencontrées au cours de la construction du concept.
La conservation, un grand principe
Authors: Trellu Jean-Louis , Toussaint Jacques
Published: June 2010

Cette réflexion met en évidence les difficultés rencontrées lors de la genèse d'un concept comme celui d'énergie, tant au plan épistémologigue que pédagogigue : quels sont les cheminements possibles, les obstacles à franchir ou contourner par les élèves dans un tel réseau multi-sémantigue et peut-on en préciser les noeuds ?

Par des essais de clarification et d'analyse de situations de classe à mettre en oeuvre, dont le mot énergie serait le pôle central, on tente de montrer des méthodes d'approche en terme de transferts et de conservation, d'un concept intégrateur d'un champ disciplinaire.
La vitesse au cours moyen
Authors: Canal Jean-Loup
Published: June 2010

Tout enfant, dès son jeune âge, est confronté à la "vitesse" et se donne une représentation de cette grandeur. Mais cette grandeur est complexe et ne peut se construire seule car elle dépend de deux autres, la distance et le temps. Elle se trouve au carrefour d'une foule de difficultés complexes de toutes sortes.

C'est au cours moyen deuxième année (10-11 ans) que nous nous intéresserons Ici, classe où traditionnellement est abordée l'étude mathématique de la vitesse. La vitesse est posée a priori comme une évidence : c'est le résultat du quotient de la distance par la durée mise pour la parcourir. Le raccourci est effrayant et le résultat évident : seule une minorité d'élèves intègre cette définition. Le mécanisme étant monté, d'autres élèves l'utilisent sans comprendre, d'autres se bloquent.
Sur la notion de contrat didactique
Authors: Drouin Anne-Marie
Published: June 2010

Las nociones de contrato y de transposición didácticas son actualmente centrales en didáctica de las matemáticas. En que medida son especificas en ese dominio ? Cuales son las adaptaciones necesarias para poder transplantarlas a otras asignaturas o disciplinas. Sin pretender dar una respuesta elaborada, el texto siguiente tiene en cuenta las discusiones y comentarios en el seno del equipo INRP (Institut National de Recherche Pédagogique) responsable en Ciencias Experimentales.
Le développement de la pensée scientifique (orientation biologique) chez les enfants de 6 à 14 ans
Authors: Lalanne Jacques
Published: June 2010

Cet article reprend les grandes lignes d’une thèse de 3ème cycle qui se situe délibérément dans une approche constructiviste des concepts, en référence à Piaget. L'analyse du développement de la pensée scientifique s'inscrit dans une préoccupation systémique : un ensemble de systèmes constitue un tout en mouvement mais détermine pourtant différents états d’équilibre que l'on peut apprécier et décrire. Cela est particulièrement net pour les niveaux de formulation de concepts qui sont ici exposés.
Le modèle en questions
Authors: Drouin Anne-Marie
Published: June 2010

The model in question.

Is a single concept hidden behind the many different uses of the term "model" or must we be content to accept its heterogeneity ? The following text gives an account of the discussion of this question at a seminar. A single closed definition is not the end envisaged in this study, but an attempt is made to find coherence among contradictions. Some characteristics pointed out in the study are illustrated by the analysis of a biology model.
Modélisation et astronomie
Authors: Pierrard Marie-Anne
Published: June 2010

Modélisation and astronomy.

Astronomy is a particularly suitable field for modelisation. What sort of models can primary school children achieve ? A series of activities in "Cours Moyen" (9-11 or 12) are here analysed, providing an opportunity to assess the areas in which children have been able to modelize, and how far they have advanced in it.
Optimal estimation of the surface fluxes of methyl chloride using a 3-D global chemical transport model
Authors: Xiao X. , Prinn R. G. , Fraser P. J. , Simmonds P. G. , Weiss R. F. , O'Doherty S. , Miller B. R. , Salameh P. K. , Harth C. M. , Krummel P. B. , Porter L. W. , Mühle J. , Greally B. R. , Cunnold D. , Wang R. , Montzka S. A. , Elkins J. W. , Dutton G. S. , Thompson T. M. , Butler J. H. , Hall B. D. , Reimann S. , Vollmer M. K. , Stordal F. , Lunder C. , Maione M. , Arduini J. , Yokouchi Y.
Published: June 2010

Abstract. Methyl chloride (CH3Cl) is a chlorine-containing trace gas in the atmosphere contributing significantly to stratospheric ozone depletion. Large uncertainties in estimates of its source and sink magnitudes and temporal and spatial variations currently exist. GEIA inventories and other bottom-up emission estimates are used to construct a priori maps of the surface fluxes of CH3Cl. The Model of Atmospheric Transport and Chemistry (MATCH), driven by NCEP interannually varying meteorological data, is then used to simulate CH3Cl mole fractions and quantify the time series of sensitivities of the mole fractions at each measurement site to the surface fluxes of various regional and global sources and sinks. We then implement the Kalman filter (with the unit pulse response method) to estimate the surface fluxes on regional/global scales with monthly resolution from January 2000 to December 2004. High frequency observations from the AGAGE, SOGE, NIES, and NOAA/ESRL HATS in situ networks and low frequency observations from the NOAA/ESRL HATS flask network are used to constrain the source and sink magnitudes. The inversion results indicate global total emissions around 4100 ± 470 Gg yr−1 with very large emissions of 2200 ± 390 Gg yr−1 from tropical plants, which turn out to be the largest single source in the CH3Cl budget. Relative to their a priori annual estimates, the inversion increases global annual fungal and tropical emissions, and reduces the global oceanic source. The inversion implies greater seasonal and interannual oscillations of the natural sources and sink of CH3Cl compared to the a priori. The inversion also reflects the strong effects of the 2002/2003 globally widespread heat waves and droughts on global emissions from tropical plants, biomass burning and salt marshes, and on the soil sink.
A critical look at spatial scale choices in satellite-based aerosol indirect effect studies
Authors: Grandey B. S. , Stier P.
Published: June 2010

Abstract. Analysing satellite datasets over large regions may introduce spurious relationships between aerosol and cloud properties due to spatial variations in aerosol type, cloud regime and synoptic regime climatologies. Using MODerate resolution Imaging Spectroradiometer data, we calculate relationships between aerosol optical depth τa, derived liquid cloud droplet effective number concentration Ne and liquid cloud droplet effective radius re at different spatial scales. Generally, positive values of dlnNe dlnτa are found for ocean regions, whilst negative values occur for many land regions. The spatial distribution of dlnre dlnτa shows approximately the opposite pattern, with generally postive values for land regions and negative values for ocean regions. We find that for region sizes larger than 4°×4°, spurious spatial variations in retrieved cloud and aerosol properties can introduce widespread significant errors to calculations of dlnNe dlnτa and dlnre dlnτa . For regions on the scale of 60°×60°, these methodological errors may lead to an overestimate in global cloud albedo effect radiative forcing of order 80%.
Downscaling, parameterization, decomposition, compression: a perspective from the multiresolution analysis
Authors: Yano J.-I.
Published: June 2010

Abstract. Geophysical models in general, and atmospheric models more specifically, are always limited in spatial resolutions. Due to this limitation, we face with two different needs. The first is a need for knowing (or "downscaling") more spatial details (e.g., precipitation distribution) than having model simulations for practical applications, such as hydrological modelling. The second is a need for "parameterizing" the subgrid-scale physical processes in order to represent the feedbacks of these processes on to the resolved scales (e.g., the convective heating rate). The present article begins by remarking that it is essential to consider the downscaling and parametrization as an "inverse" of each other: downscaling seeks a detail of the subgrid-scale processes, then the parameterization seeks an integrated effect of the former into the resolved scales. A consideration on why those two closely-related operations are traditionally treated separately, gives insights of the fundamental limitations of the current downscalings and parameterizations. The multiresolution analysis (such as those based on wavelet) provides an important conceptual framework for developing a unified formulation for the downscaling and parameterization. In the vocabulary of multiresolution analysis, these two operations may be considered as types of decompression and compression. A new type of a subgrid-scale representation scheme, NAM-SCA (nonhydrostatic anelastic model with segmentally-constant approximation), is introduced under this framework.
Car MAX-DOAS measurements around entire cities: quantification of NOx emissions from the cities of Mannheim and Ludwigshafen (Germany)
Authors: Ibrahim O. , Shaiganfar R. , Sinreich R. , Stein T. , Platt U. , Wagner T.
Published: June 2010

Abstract. We present car Multi-Axis (MAX-) DOAS observations of tropospheric NO2 carried out on circles around the cities of Mannheim and Ludwigshafen (Germany) on 24 August 2006. Together with information on wind speed and direction, the total emissions of the encircled source(s) are quantified from these measurements. In contrast to recent similar studies based on zenith scattered sun light (elevation angle of 90°), we use a MAX-DOAS instrument mounted on a car, which observes scattered sun light under different elevation angles (here 45°, and 90°). Compared to simple zenith sky observations, MAX-DOAS observations have higher sensitivity and reduced uncertainty, and avoid systematic offsets in the determination of the vertically integrated trace gas concentration. The determination of the absolute value of the integrated tropospheric trace gas concentrations is especially important for the calculation of absolute trace gas fluxes through arbitrary transects. However, even if emission sources are completely surrounded, systematic offsets in the measured vertically integrated trace gas concentration can lead to errors in the determined total emissions, especially for observations around extended areas. In this study we discuss and quantify different error sources. In most cases, the largest error source is the variability and imperfect knowledge of the wind field. In addition – depending on the trace species observed - also chemical transformations between the emission sources and the measurement location have to be considered. For that purpose we use local observations within the encircled area to quantify and/or correct these errors. From our observations we derive a total NOx emission from the Mannheim/Ludwigshafen area of (7.4±1.8)×1024 molec/sec, which if assumed to be constant throughout the year would correspond to a total emission of 17 830±4340 t/yr (calculated with the mass of NO2 t/yr, consistent with existing emission estimates. From our observations it is also possible to separately determine the average influx into the Mannheim/Ludwigshafen area (5.4±0.9×1024 molec/sec or 13 010±2170 t/yr) and the average outflux (12.8±1.8×1024 molec/sec or 13 010±4340 t/yr).
Shelf erosion and submarine river canyons: implications for deep-sea oxygenation and ocean productivity during glaciation
Authors: Tsandev I. , Rabouille C. , Slomp C. P. , Van Cappellen P.
Published: June 2010

Abstract. The areal exposure of continental shelves during glacial sea level lowering enhanced the transfer of erodible reactive organic matter to the open ocean. Sea level fall also activated submarine canyons thereby allowing large rivers to deposit their particulate load, via gravity flows, directly in the deep-sea. Here, we analyze the effects of shelf erosion and particulate matter re-routing to the open ocean during interglacial to glacial transitions, using a coupled model of the marine phosphorus, organic carbon and oxygen cycles. The results indicate that shelf erosion and submarine canyon formation may significantly lower deep-sea oxygen levels, by up to 25%, during sea level low stands, mainly due to the supply of new material from the shelves, and to a lesser extent due to particulate organic matter bypassing the coastal zone. Our simulations imply that deep-sea oxygen levels can drop significantly if eroded shelf material is deposited to the seafloor. Thus the glacial ocean's oxygen content could have been significantly lower than during interglacial stages. Primary production, organic carbon burial and dissolved phosphorus inventories are all affected by the erosion and rerouting mechanisms. However, re-routing of the continental and eroded shelf material to the deep-sea has the effect of decoupling deep-sea oxygen demand from primary productivity in the open ocean. P burial is also not affected showing a disconnection between the biogeochemical cycles in the water column and the P burial record.
Evolution of the spherical cavity radius generated around a subsurface drip emitter
Authors: Gil M. , Rodríguez-Sinobas L. , Sánchez R. , Juana L.
Published: June 2010

Abstract. The emitter discharge in subsurface drip irrigation can be affected by soil properties. A positive pressure develops at the emitter outlet where a spherical cavity is assumed to form. In steady-state conditions, the pressure in the soil relates to soil hydraulic properties, the emitter discharge, and the cavity radius. This pressure in the soil is very sensitive to the cavity radius. In this paper, the development of the cavity around the emitter outlet was measured for various emitter discharges in laboratory tests carried out in containers with uniform loamy soils. A trend between soil pressure and emitter discharge was established that illustrates the performance of buried emitters in the field. Its application to the prediction of water distribution in subsurface drip irrigation units and its effect on the estimation of irrigation performance are also shown.
A fast stratospheric chemistry solver: the E4CHEM submodel for the atmospheric chemistry global circulation model EMAC
Authors: Baumgaertner A. J. G. , Jöckel P. , Steil B. , Tost H. , Sander R.
Published: June 2010

Abstract. The atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC) and the atmospheric chemistry box model CAABA are extended by a computationally very efficient submodel for atmospheric chemistry, E4CHEM. It focuses on stratospheric chemistry but also includes background tropospheric chemistry. It is based on the chemistry of MAECHAM4-CHEM and is intended to serve as a simple and fast alternative to the flexible but also computationally more demanding submodel MECCA. In a model setup with E4CHEM, EMAC is now also suitable for simulations of longer time scales. The reaction mechanism contains basic O3, CH4, CO, HOx, NOx, and ClOx gas phase chemistry. In addition, E4CHEM includes optional fast routines for heterogeneous reactions on sulphate aerosols and polar stratospheric clouds (substituting the existing submodels PSC and HETCHEM), and scavenging (substituting the existing submodel SCAV). We describe the implementation of E4CHEM into the MESSy structure of CAABA and EMAC. For some species the steady state in the box model differs by up to 100% when compared to results from CAABA/MECCA due to different reaction rates. After an update of the reaction rates in E4CHEM the mixing ratios in both boxmodel and 3-D model simulations are in satisfactory agreement with the results from a simulation where MECCA with a similar chemistry scheme was employed. Finally, a comparison against a simulation with a more complex and already evaluated chemical mechanism is presented in order to discuss shortcomings associated with the simplification of the chemical mechanism.
Prediction of snowmelt derived streamflow in a wetland dominated prairie basin
Authors: Fang X. , Pomeroy J. W. , Westbrook C. J. , Guo X. , Minke A. G. , Brown T.
Published: June 2010

Abstract. The Cold Regions Hydrological Modelling platform (CRHM) was used to create a prairie hydrological model for Smith Creek Research Basin (~400 km2), east-central Saskatchewan, Canada. Physically based modules were sequentially linked in CRHM to simulate snow processes, frozen soils, variable contributing area and wetland storage and runoff generation. Five "representative basins" (RBs) were defined and each was divided into seven hydrological response units (HRUs): fallow, stubble, grassland, river channel, open water, woodland, and wetland. Model parameters were estimated using field survey data, LiDAR digital elevation model (DEM), SPOT 5 satellite imageries, stream network and wetland inventory GIS data. Model simulations were conducted for 2007/2008 and 2008/2009. No calibration was performed. The model performance in predicting snowpack, soil moisture and streamflow was evaluated against field observations. Root mean square differences (RMSD) between simulation and observations ranged from 1.7 to 25.2 mm and from 4.3 to 22.4 mm for the simulated snow accumulation in 2007/2008 and 2008/2009, respectively, with higher RMSD in grassland, river channel, and open water HRUs. Spring volumetric soil moisture was reasonably predicted compared to a point observation in a grassland area, with RMSD of 0.011 and 0.009 for 2008 and 2009 simulations, respectively. The model was able to capture the timing and magnitude of peak spring basin discharge, but it underestimated the cumulative volume of basin discharge by 32% and 56% in spring 2008 and 2009, respectively. The results suggest prediction of Canadian Prairie basin snow hydrology is possible with no calibration if physically based models are used with physically meaningful model parameters that are derived from high resolution geospatial data.
Nonextensive analysis of crustal seismicity in Taiwan
Authors: Telesca L. , Chen C.-C.
Published: June 2010

Abstract. Using the Taiwan Central Weather Bureau earthquake catalogue, the crustal seismicity of Taiwan was analyzed by means of a nonextensive approach. The time span of the analyzed catalogue is from 1 January 1990 to 30 November 2007, and only earthquakes with magnitude M≥2.0 were considered. Our findings reveal that the nonextensive statistics furnishes a very good prediction of the cumulative magnitude distribution of crustal seismicity in Taiwan, even if the aftershocks are removed, indicating that the approach is robust for clustered as well as declustered seismicity.
Complementary nature of surface and atmospheric parameters associated with Haiti earthquake of 12 January 2010
Authors: Singh Ramesh P. ,   Waseem Mehdi,   Manish Sharma
Published: June 2010

Abstract. The present paper describes surface (surface air temperature) and atmospheric parameters (relative humidity, surface latent heat flux) over the epicenter (18°27´25´´ N 72°31´59´´ W) of Haiti earthquake of 12 January 2010. Our analysis shows pronounced changes in surface and atmospheric parameters few days prior to the main earthquake event. Changes in relative humidity are found from the surface up to an altitude of 500 hPa clearly show atmospheric perturbations associated with the earthquake event. The purpose of this paper is to show complementary nature of the changes observed in surface, atmospheric and meteorological parameters. The total ozone concentration is found to be lowest on the day of earthquake and afterwards found to be increased within a week of earthquake. The present results show existence of coupling between lithosphere-atmosphere associated with the deadly Haiti earthquake.
Radon signals at the Roded site, southern Israel
Authors: Steinitz G. , Piatibratova O.
Published: June 2010

Abstract. Temporal variations of radon in the geological environment (upper crust) are frequent and recognized as unique in terms of the signals encountered and for the lack of substantial and generally applicable explanations. The phenomena observed at the Roded site, located in arid southern Israel, emphasize this situation. Monitoring of radon during more than 10 years is carried out in massive meta-diorite of the Precambrian basement block of Roded. Measurement is conducted using an alpha detector at a resolution of 15-min, lowered in a borehole at a depth of 9 m, within a PVC casing to that depth. Systematic temporal variation patterns, manifesting large relative signals are composed of sub-daily (SDR) radon, multi-day (MD) and annual (AR) signals. The overall variation in dominated by the intense SDR signals which occur in some days, and may vary from background levels (5 counts or less) to peak values (attaining >1000 counts) and back to background in an interval of 6 to 12 h. Intervals of up to several tens of days without significant SDR signals interchange with times of intense daily occurrences of such signals. Their occurrence indicates very fast variations of radiation from radon at the point of measurement. The peak times, within the diurnal 24-h cycle of SDR signals occur preferentially in the interval of 14–16 h (UT+2). Spectral analysis indicates: (a) A diurnal periodicity composed of a primary 24-h and a secondary 12-h periodicity, which are attributed to the solar tide constituents S1 and S2. Tidal constituents indicative for gravity tide (O1, M2) are lacking; (b) An annual periodicity. A compound relation among the diurnal and annual periodicity is indicated by: (a) Wavelet (CWT) analysis showing an overall annual structure with a modulation of the S1 and S2 periodicities; (b) FFT analysis using consecutive 21.3-day long time intervals shows that the amplitudes of S1 and S2 vary in an annual pattern, with relatively high values in summer. The phase of S1 and S2 and S3 shows a systematic multi-year variation. Existing frames of reference of geophysical processes cannot explain the highly systematic phenomena. It is suggested that the significant signatures of the periodic phenomena and their modulations are reflecting a direct link with solar radiation tide.
Brazilian baccharis toxins: Livestock poisoning and the isolation of macrocyclic trichothecene glucosides
Authors: Jarvis Bruce B. , Wang Shengjun , Cox Christopher , Rao M. Madhusudana , Philip Valsa , Varaschin Mary S. , Barros Claudio S.
Published: June 2010

Samples of the toxic Brazilian plant, Baccharis coridifolia, which is reponsible for numerous cases of livestock poisoning in southern Brazil and Argentina, were collected during the growing season, and the toxicities in calves of the plant materials were correlated with the levels of macrocyclic trichothecenes present. Female plants in flower were considerably more toxic than male plants or plants not in flower. Plants not in flower were of intermediate toxicity The female plants in flower typically contained 5–10 times the levels of toxins as were found in the male plants. In addition, six new glucosides of the macrocyclic trichothecenes were isolated and characterized. The most prominent glucosides, those of roridins A and E, were found in high levels in the female plants.
Effect of an unknown toxin isolated from dinophysis sp.‐contaminated French mussels, on the electrical and mechanical activity of frog heart
Authors: Sauviat Martin‐Pierre , Vernoux Jean‐Paul , Le Baut Claire Marcaillou , Bansard Stéphane , Hamelin Magali
Published: June 2010

The effects of an unknown toxin, isolated along with okadaic acid from the hepatopancreas of French mussels contaminated by Dinophysis sp., producing ataxia, neurologic symptoms, bradycardia, arythmias, electrocardiographic changes, and cardiac arrest, have been studied in terms of the electrical and mechanical activity of frog atrial heart muscle. The toxin, in a dose‐dependent manner, decreased the amplitude of the stimulated peak tension of isolated fibers. The toxin (1–36 μg/ml) did not modify the membrane resting potential but decreased the amplitude of the plateau and shortened the duration of the action potential. The toxin inhibited the Cd‐sensitive L‐type Ca current and increased a 4‐aminopyridine‐sensitive outward current in voltage‐clamped cardiac myocytes. The data show that the cardiac effect of the toxin is markedly different from that of okadaic acid.
Comparison of detection methods for trichothecenes produced by fusarium sporotrichioides on fodder and grains at different air humidities
Authors: Nikulin Marjo , Lappalainen Sanna , Pasanen Anna‐Liisa , Laamanen Ilona , Veijalainen Pirjo , Berg Seija , Hintikka Eeva‐Liisa
Published: June 2010

Growth and toxin production of a highly toxic strain of Fusarium sporotrichioides Sherb. were studied on oat and wheat grains and on straw under experimental conditions, in which relative humidity (RH) of air was regulated. The materials were incubated at three different RH levels at a range of 84–100%. F. sporotrichioides grew well on oat and wheat grains at RH 97–100% but grew less well at RH 84–88% and on straw. Toxin production was measured with three biological toxicity tests (cytotoxicity test, dermotoxicity test, and yeast cell toxicity test), with chemical analysis, and T‐2 ELISA assay. Cytotoxicity and production of trichothecene mycotoxins were detected in all the samples incubated at all three RH levels. On oat and wheat grains, T‐2 toxin, neosolaniol, and diacetoxyscirpenol were found, and on straw T‐2 toxin, HT‐2 toxin, neosolaniol, and T‐2 tetraol were determined. In the T‐2 ELISA assay, all material samples were found to contain T‐2 toxin. The cytotoxicity test was the most sensitive method for detecting biological toxicity of samples inoculated with fungus. The T‐2 ELISA assay and chemical analysis were about equally sensitive to detect T‐2 toxin in samples.
Effects of the naturally occurring arginine analogues indospicine and canavanine on nitric oxide mediated functions in aortic endothelium and peritoneal macrophages
Authors: Pass Michael A. , Arab Hossein , Pollitt Sandra , Hegarty Mervan P.
Published: June 2010

The ability of the naturally occurring non‐protein toxic amino acids indospicine and canavanine to inhibit nitric oxide synthesis was tested in isolated rat aorta and cultured rat peritoneal macrophages. Both compounds inhibited acetylcholine induced relaxation of rat aorta contracted with noradrenaline, a process mediated by nitric oxide generated in vascular endothelium. Nitric oxide is generated in vascular endothelium from arginine by a constitutive nitric oxide synthase. Indospicine and canavanine also increased superoxide mediated reduction of cytochrome c by phorbol mynstate acetate stimulated rat peritoneal macrophages. The increase in superoxide under these conditions was due to decreased nitric oxide synthesis. Macrophage synthesis of nitric oxide is mediated by an inducible form of nitric oxide synthase. It is concluded that indospicine and canavanine are inhibitors of constitutive and inducible nitric oxide synthases and it is suggested that the toxicity associated with these compounds could be related to this activity.
Microcystin levels during 1992–95 for lakes sagami and tsukui‐japan
Authors: Tsuji Kiyomi , Setsuda Setsuko , Watanuki Tomohiko , Kondo Fumio , Nakazawa Hiroyuki , Suzuki Makoto , Harada Ken‐Ichi
Published: June 2010

Toxic cyanobacterial blooms have been frequently observed in Lakes Sagami and Tsukui, Kanagawa Prefecture, Japan, which are used as drinking and recreational water sources. As the first step toward the control and removal of cyanobacterial toxins, the present study evaluated the microcystin level in these lakes. Our established method using HPLC and LC/MS to pursue trace amounts of microcystins was applied to the determination of microcystins within cyanobacteria cells and in water. We could determine precisely the intracellular and extracellular microcystin level in the water environment during 1992–95. Microcystins RR, LR, and YR were detected at 0.02–2.64 μg/L in cell‐free water and at 0.02–378 μg/L in the cells. Although there were many cases in which microcystin concentrations in the cells exceeded the proposed guideline level (1 μg/L), there was only one example of this happening in cell‐free water samples. Because the present monitoring indicted that the amount of microcystins detected in water was much less than that estimated in cells, the release of microcystins from the cells and their stability in lake water were examined in the dark. The resulting toxins persisted at the same concentration level for 14 days and the microcystin concentrations steadily declined, showing that biodegradation using aquatic natural bacterial flora is an effective detoxification process under natural conditions.
Ultrastructural changes in the alveolar cells of rats injected with Cerastes cerastes cerastes venom
Authors: Fares Nagui Hassan , El‐Aal A. Abd
Published: June 2010

Ultrastructural changes in the alveolar tissue of rats intraperitoneally injected with the Cerastes cerastes cerastes venom were studied in 2 different experimental groups. In the first group, each rat was given 0.73 mg/Kg as a single dose and sacrificed after 24 hours. In the second group, each rat was given a daily dose of 0.42 mg/Kg for 7 days and sacrificed 24 hours after the last injection. Proliferative changes were seen in type II alveolar cells, fibroblasts, lymphocytes, and macrophages. Type II alveolar cells of the lungs developed a large number of surfactant granules. In the 24‐hour‐envenomated rats, type I alveolar cells displayed swollen nuclei and masses of dilated endoplasmic reticulum. In the 7‐day‐treated rats, several plasma cells, adjacent interstitial cells as well as alveolar brush cells, with their characteristic short microvilli, were detected. Large masses of collagen and elastic fibers were also located in the vicinity of the alveolar brush cells and type II alveolar cells. These histopathological changes may be attributed to the body‐immune response and possibly to the development of hyperplasia due to venom‐induced trauma. Nat. Toxins 5:208–221, 1997. © 1998 Wiley‐Liss, Inc.
Perforated Sheets Exhibiting Negative Poisson's Ratios
Authors: Grima Joseph N. , Gatt Ruben
Published: June 2010

Sheets made from readily available conventional materials containing diamond or star shaped perforations are shown to exhibit various Poisson's ratio values which could also be negative (auxetic). This behavior may be exhibited in both tension and compression and can be explained through models based on “rotating rigid units.” This provides an easy manner for the manufacture of auxetic or conventional systems at any scale which can be tailor made to exhibit particular values of the Poisson's ratio.
Microstructural Analysis of the Reinforced Al‐Cu5mgti/Tib2 5 wt % Alloy for Investment Casting Applications
Authors: Egizabal Pedro , García de Cortazar Maider , Douin Joël , Torregaray Amaia , Lahaye Michel , Vincent Cécil , Silvain Jean‐Frangois
Published: June 2010

The paper describes the influence of 5 wt % titanium diboride (TiB2) particles on the microstructure of an Al‐Cu alloy produced by plaster casting process. The elaboration route leads to a composite material with 1% of in situ TiB2 particles and 4% ex situ of TiB2 particles. The comparison of the reinforced alloy with the corresponding non‐reinforced counterpart makes clear that the presence of TiB2 particles has a large influence in the observed microstructure. The presence of TiB2 particles decreases the grain sizes and the porosity level. It is also found that TiB2 particles play an important role in the precipitation events of Al2Cu precipitates that are formed during solidification at the TiB2/aluminum matrix interfaces.
Multilayer Amorphous‐Si‐B‐C‐N/γ‐Al2O3/α‐Al2O3 Membranes for Hydrogen Purification
Authors: Prasad Ravi Mohan , Iwamoto Yuji , Riedel Ralf , Gurlo Aleksander
Published: June 2010

The hydrogen and carbon monoxide separation is an important step in the hydrogen production process. If H2 can be selectively removed from the product side during hydrogen production in membrane reactors, then it would be possible to achieve complete CO conversion in a single‐step under high temperature conditions. In the present work, the multilayer amorphous‐Si‐B‐C‐N/γ‐Al2O3/α‐Al2O3 membranes with gradient porosity have been realized and assessed with respect to the thermal stability, geometry of pore space and H2/CO permeance. The α‐Al2O3 support has a bimodal pore‐size distribution of about 0.64 and 0.045 µm being macroporous and the intermediate γ‐Al2O3 layer—deposited from boehmite colloidal dispersion—has an average pore‐size of 8 nm being mesoporous. The results obtained by the N2‐adsorption method indicate a decrease in the volume of micropores—0.35 vs. 0.75 cm3 g−1—and a smaller pore size −6.8 vs. 7.4 Å—in membranes with the intermediate mesoporous γ‐Al2O3 layer if compared to those without. The three times Si‐B‐C‐N coated multilayer membranes show higher H2/CO permselectivities of about 10.5 and the H2 permeance of about 1.05 × 10−8 mol m−2 s−1 Pa−1. If compared to the state of the art of microporous membranes, the multilayer Si‐B‐C‐N/γ‐Al2O3/α‐Al2O3 membranes are appeared to be interesting candidates for hydrogen separation because of their tunable nature and high‐temperature and high‐pressure stability.
Integrated batch‐to‐batch and nonlinear model predictive control for polymorphic transformation in pharmaceutical crystallization
Authors: Hermanto Martin Wijaya , Braatz Richard D. , Chiu Min‐Sen
Published: June 2010

Polymorphism, a phenomenon in which a substance can have more than one crystal form, is a frequently encountered phenomenon in pharmaceutical compounds. Different polymorphs can have very different physical properties such as crystal shape, solubility, hardness, color, melting point, and chemical reactivity, so that it is important to ensure consistent production of the desired polymorph. In this study, an integrated batch‐to‐batch and nonlinear model predictive control (B2B‐NMPC) strategy based on a hybrid model is developed for the polymorphic transformation ofL‐glutamic acid from the metastable α‐form to the stable β‐form crystals. The hybrid model comprising of a nominal first‐principles model and a correction factor based on an updated PLS model is used to predict the process variables and final product quality. At each sampling instance during a batch, extended predictive self‐adaptive control (EPSAC) is employed as a NMPC technique to calculate the control action by using the current hybrid model as a predictor. At the end of the batch, the PLS model is updated by utilizing the measurements from the batch and the above procedure is repeated to obtain new control actions for the next batch. In a simulation study using a previously reported model for a polymorphic crystallization with experimentally determined parameters, the proposed B2B‐NMPC control strategy produces better performance, where it satisfies all the state constraints and produces faster and smoother convergence, than the standard batch‐to‐batch strategy. © 2010 American Institute of Chemical Engineers AIChE J, 2011
Mikrotröpfchen in Mikrofluidiksystemen: eine Technik für Entdeckungen in der Chemie und Biologie
Authors: Theberge Ashleigh B. , Courtois Fabienne , Schaerli Yolanda , Fischlechner Martin , Abell Chris , Hollfelder Florian , Huck Wilhelm T. S.
Published: June 2010

Mikrotröpfchen in Mikrofluidiksystemen bieten zahlreiche Möglichkeiten für die chemische und biologische Forschung. Sie ermöglichen die isolierte Betrachtung von Spezies oder Reaktionen, sie sind monodispers und daher für quantitative Studien geeignet, sie können für Studien in extrem kleinen Volumina sowie an einzelnen Zellen oder einzelnen Molekülen eingesetzt werden, und sie sind für Hochdurchsatzexperimente geeignet. Dieser Aufsatz analysiert die Bedeutung dieser Eigenschaften im Hinblick auf neue biologische und chemische Experimente, wobei jüngste Fortschritte bei der Entwicklung von Apparaturen vorgestellt, aber auch verbleibende technologische Herausforderungen angesprochen werden. Anhand von Beispielen wird gezeigt, welche Vorteile die Kompartimentierung, die Monodispersität der Tröpfchen, die Betrachtung einzelner Moleküle und der hohe Durchsatz in Experimenten gebracht haben, die ohne den Einsatz von Mikrofluidiksystemen kaum möglich gewesen wären.
Ab Initio Thermochemistry of Solid‐State Materials
Authors: Stoffel Ralf Peter , Wessel Claudia , Lumey Marck‐Willem , Dronskowski Richard
Published: June 2010

In this contribution we introduce an electronic‐structure‐theory‐based approach to a quantum‐chemical thermochemistry of solids. We first deal with local and collective atomic displacements and explain how to calculate these. The fundamental importance of the phonons, their dispersion relations, their experimental determination as well as their calculation is elucidated, followed by the systematic construction of the thermodynamic potentials on this basis. Subsequently, we provide an introduction for practical computation as well as a critical analysis of the level of accuracy obtainable. We then show how different solid‐state chemistry problems can be solved using this approach. Among these are the calculation of activation energies in perovskite‐like oxides, but we also consider the use of theoretical vibrational frequencies for determining crystal structures. The pressure and temperature polymorphism of elemental tin which has often been classically described is also treated, and we energetically classify the metastable oxynitrides of tantalum. We also demonstrate, using the case of high‐temperature superconductors, that such calculations may be used for an independent evaluation of thermochemical data of unsatisfactory accuracy. Finally, we show the present limits and the future challenges of the theory.
Crystallization and melting behavior of HDPE in HDPE/teak wood flour composites and their correlation with mechanical properties
Authors: Sewda Kamini , Maiti S. N.
Published: June 2010

The nonisothermal crystallization behavior and melting characteristics of high‐density polyethylene (HDPE) in HDPE/teak wood flour (TWF) composites have been studied by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) methods. Composite formulations of HDPE/TWF were prepared by varying the volume fraction (ϕf) of TWF (filler) from 0 to 0.32. Various crystallization parameters evaluated from the DSC exotherms were used to study the nonisothermal crystallization behavior. The melting temperature (Tm) and crystallization temperature (Tp) of the composites were slightly higher than those of the neat HDPE. The enthalpy of melting and crystallization (%) decrease with increase in the filler content. Because the nonpolar polymer HDPE and polar TWF are incompatible, to enhance the phase interaction maleic anhydride grafted HDPE (HDPE‐g‐MAH) was used as a coupling agent. A shift in the crystallization and melting peak temperatures toward the higher temperature side and broadening of the crystallization peak (increased crystallite size distribution) were observed whereas crystallinity of HDPE declines with increase in ϕf in both DSC and WAXD. Linear correlations were obtained between crystallization parameters and tensile and impact strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Preparation and characterization of complex gel of type I collagen and aluminosilicate containing imogolite nanofibers
Authors: Nakano Asuka , Teramoto Naozumi , Chen Guoping , Miura Yoshiko , Shibata Mitsuhiro
Published: June 2010

Complex gel materials of Type I collagen and aluminosilicate containing imogolite nanofibers were prepared as opaque gel by mixing an acidic fine dispersion of aluminosilicate with an acidic solution of collagen. The product was stained blue by Coomassie Brilliant Blue (CBB), indicating that the gel contained collagen. A white sponge was obtained after lyophilization of the complex gel. Elemental analysis revealed that the complex contains C, H, N, Al, and Si atoms; and the compositional ratio of aluminosilicate/collagen (w/w) was calculated as 0.75 for the complex gel when aluminosilicate was mixed with an equal quantity of collagen. Transmission electron microscope (TEM) observation showed that aluminosilicate nanofibers were homogeneously distributed in the collagen matrix. The thermogravimetric analysis (TGA) curve of the complex was not a simple summation of each components, and especially, the weight loss step corresponding to detachment of the adsorbed water observed in aluminosilicate became difficult to distinguish, suggesting that the adsorbed water was removed in the complexation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
A morphological view of the sodium 4,4′‐distyrylbiphenyl sulfonate fluorescent brightness distribution on regenerated cellulose fibers
Authors: Iamazaki Eduardo T. , Pereira‐Da‐Silva Marcelo A. , Carvalho Antonio J. F. , Romero Rafaelle B. , Gonçalves Maria C. , Atvars Teresa D. Z.
Published: June 2010

Evidence of the sorption of the whitening agent sodium 4,4′‐distyrylbiphenyl sulfonate in the presence of the anionic surfactant sodium dodecylsulfate or the cationic surfactant dodecyl trimethyl ammonium chloride on regenerated cellulose fibers is given by several microscopy techniques. Scanning electron microscopy provided images of the cylindrical fibers with dimensions of 3.5 cm (length) and 13.3 μm (thickness), with empty cores of 1 μm diameter and a smooth surface. Atomic force microscopy showed a fiber surface with disoriented nanometric domains using both tapping‐mode height and phase image modes. Atomic force microscopy also showed that the whitening agent and surfactant molecules were sorbed onto the fiber surface, in agreement with the adsolubilization sorption model. Transmission electron microscopy showed fibers with nanometric parallel cylinders, surrounded by holes where the fluorescent whitening molecules accumulated. On the basis of these techniques, we conclude that the sorption process occurs preferentially on the fiber surface in contact with the water solution, and under saturated conditions, the whitening agent penetrates into the pores and are simultaneously sorbed on the pore walls bulk, forming molecular aggregates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010