Hypertext Linking as a Model of Expert Indexing

The position of this paper is that hypertext environments provide a new domain in which to explore the cognitive processes of indexing and classification and that the study of hypertext links allows the classification researcher to test the adequacy of current indexing theory. The process of linking segments of text in a hypertext system is a process similar to development of classes and term relations in the indexing process. However. linking methods can allow for linking without articulating the nature of the relationship: two segments may be connected on an intuitive basis rather than on the basis of a stated relationship between segments. Exploration of these "intuitive" links may suggest new approaches to indexing, that is, alternative facets, or connections among text segments, that contrast to current indexing languages

Self-interaction chromatography as a tool for optimizing conditions for membrane protein crystallization

The second virial coefficient, or B value, is a measurement of how well a protein interacts with itself in solution. These interactions can lead to protein crystallization or precipitation, depending on their strength, with a narrow range of B values (the `crystallization slot') being known to promote crystallization. A convenient method of determining the B value is by self-interaction chromatography. This paper describes how the light-harvesting complex 1-reaction centre core complex from Allochromatium vinosum yielded single straight-edged crystals after iterative cycles of self-interaction chromatography and crystallization. This process allowed the rapid screening of small molecules and detergents as crystallization additives. Here, a description is given of how self-interaction chromatography has been utilized to improve the crystallization conditions of a membrane protein

Influence du pH sur les propriétés des sols : l'essai de longue durée des 42 parcelles à Versailles

Les pratiques de fertilisation et d'amendement peuvent contribuer à modifier profondément les propriétés des sols. Ceci est mis en évidence par le dispositif des 42 parcelles de l'INRA à Versailles qui reçoit chaque année les mêmes traitements depuis 1929. Il présente l'originalité d'être en jachère nue. Les résultats reportés ici reposent sur 16 traitements que nous comparons à une parcelle témoin. Le sol est à caractère limoneux avec 14 à 22 % d'argile. Le pH, la capacité d'échange au pH du sol (CECsol), et les cations échangeables ont été mesurés. Des mesures de porosité, de rétention de l'eau à différents potentiels de l'eau ont été effectuées.Des variations considérables de pH sont observées. Les engrais ammoniacaux conduisent à des parcelles très acides (pH 3,5 à 5,0), à faible CECsol, essentiellement saturée par des cations aluminium. Dans les parcelles chaulées ou recevant des amendements basiques, le pH est tamponné à 8,2 par les carbonates. La CECsol double du sol acide au sol chaulé où elle est majoritairement saturée par du calcium échangeable. Avec les sels neutres (par exemple KCl, NaNO3) le pH n'a pas changé et pour le témoin il a légèrement baissé. Des observations de terrain montrent que ces différents états physico-chimiques sont en relation avec les états de surface du sol et influencent la porosité du sol en profondeur.Ainsi dans les sols des régions tempérées la CECsol peut doubler dans un domaine très restreint de pH (6,0 à 7,5), orientant fortement les propriétés physiques des sols.In temperate regions, soil acidification is a real problem. The pH change causes transformations of both the chemical and physical properties of the soil. The 42 experimental plots at the Institut national de Recherche agronomique (INRA) in Versailles, France, were created in 1929. Since that time, each plot has received either fertiliser or amendments (Table 1). There are ten reference plots that have not been treated. Plots were dug up twice a year and left fallow. The results corresponding to 17 plots, 16 treated and one reference plot, are presented in this paper. The samples were collected in 1999 and compared to the 1929 soil reference. The pH was measured in water (AFNOR 1994), the cation exchange capacity (CEC) was determined at pH 7.0 (AFNOR 1994, CEC7) and at the soil pH by the cobaltihexamine method (Ciesielski and Steckermann 1997, CECsoil). Exchangeable cations (Ca2+, Mg2+, K+ and Na+) were measured after cobaltihexamine extraction and exchangeable aluminium by the KCl method (McLean, 1965). Water retention measurements were carried out with an apparatus developed by Tessier and Berrier (1979) and AFNOR (1996) at -10 kPa, with the Richards pressure plate cell at -1.6 kPa (Richards 1948) and with a controlled hygrometry dessicator at -107 MPa (Tessier 1984).The average pH of the reference plot collected in 1929 was close to 6.3. In 1999, pH values ranged between 3.5 and 8.2. For plots treated with ammonium fertilisers the pH ranged from 3.5 to 5.5. In contrast, plots with basic treatment or liming had a soil pH that was close to 8.2 and was equilibrated with carbonates. Intermediate pH values (from 5.5 to 7.5) were obtained for plots treated with neutral salts such as KCl or NaNO3, or with superphosphate.The cation exchange capacity in soils at the reference pH (7.0) demonstrated variations in soil composition. For example, the CEC7 varied with clay content as a function of depth or with organic matter loss or gain due to lying fallow or to manure application. When the CEC was measured at soil pH (CECsoil), strong differences were observed. Two groups of plots can be differentiated in 1999. One ranged between 11 and 16 cmol+/kg; this range corresponded to plots with amendments or with fertilisers containing bases. A lower range of CECsoil values (below 11 cmol+ /kg) was obtained with ammonium fertilisers. It is important to note that between pH=6.0 and pH=7.5 the CECsoil doubled.Six months after digging, the surface state of the soil was variable. Thick crusts dominated in acidic conditions, whereas the presence of dispersing cations (K+, Na+), and a smooth surface was present in soil treated with amendments. In the soil profile, bulk density increased with acidity and sodium or potassium cation concentrations. At -10 kPa, water retention measurements demonstrated that bulk density and sampling depth were linked with water retention: the higher the bulk density, the lower the water retention. At -1.6 MPa, water retention was correlated to the amount of clay and organic matter content. We also showed that the exchangeable calcium content and CECsoil influence water retention. At -107 MPa, water retention depends on pH as well as the CECsoil and exchangeable cation concentration.The main purpose of this study was to show that after 70 years, plots subjected to intensive fertilisation or amendments and lying fallow (i.e., without organic matter restitution), have dramatically different soil properties. The first indicator of this evolution was pH. Ammonium fertilisers produced very acid plots (pH 3.5 to 5.0). In the presence of neutral salts (e.g., KCl, NaNO3) and in the reference plot, the pH had decreased a little. In liming or basic treatment plots, the pH is controlled at 8.2 by carbonates. The second important factor to consider is the cation exchange capacity value. When measured at a reference pH (pH=7.0), the CEC7 reflects the natural components present in a soil, but doesn't consider the influence of physico-chemical factors that operate in the native soil. After 70 years without organic restitution, the soil has lost approximately half of its original organic matter content, and as a result the exchangeable sites were approximately 2 cmol+ /kg.The effective CEC at soil pH demonstrates the influence of pH on variable charges due to mineral constituents and organic matter. Plots with ammonium fertilisers have a low cation exchange capacity. Fertilisers with sodium and potassium cations have increased the exchangeable sodium (up to 11% of the CECsoil) or potassium (18%) respectively. The cation exchange capacity doubled in going from acidic plots to liming plots, and in the latter the CEC is mainly saturated with exchangeable calcium.In situ plot observations show that soil physico-chemical properties strongly influence not only soil surface state, but also soil profile porosity. Both acidification and dispersing cations are factors in soil degradation, whereas high pH values and calcium as the exchangeable cation produce strong structure stability and high porosity. It is also interesting to note that the CECsoil can double between pH=6.0 and pH=7.5, thus influencing the physical properties of the soil. Comparing CEC7 and CECsoil facilitates the prediction of the effects of fertilisation and amendments on soil properties. The cation exchange capacity at soil pH can be used as an excellent indicator of soil quality

La mobilité des patients et les modèles de création de demande : le cas du Québec

Dans ce texte nous analysons les conséquences de l’inégalité dans la distribution des ressources médicales sur l’utilisation des interventions chirurgicales électives en tenant compte de la mobilité des patients. Après avoir présenté un modèle théorique qui permet d’analyser l’influence de la mobilité des patients dans un marché privé d’interventions chirurgicales, nous adaptons ce modèle à un contexte d’assurance-maladie généralisée. Dans la partie empirique de notre travail nous discutons brièvement des principaux résultats que l’on retrouve dans la littérature et nous présentons quelques résultats empiriques préliminaires en utilisant des données du Québec.In this paper, we analyse the effects of the inequality in the distribution ofmedical resources on the use of elective surgeries taking into account the mobilityof the patients between geographical areas. In the first part of the paper, wepresent a theoretical model which analyses the effects of patients' mobility on aprivate market of chirurgical services and, then, we adapt this model to a regime ofpublic health insurance. In the empirical part of the paper, we discuss shortly themain results in the literature and we present some preliminary results using datafrom the province of Quebec

Thickness-dependent thermal properties of amorphous insulating thin films measured by photoreflectance microscopy

In this work, we report on the measurement of the thermal conductivity of thin insulating films of SiO2 obtained by thermal oxidation, and Al2O3 grown by atomic layer deposition (ALD), both on Si wafers. We used photoreflectance microscopy to determine the thermal properties of the films as a function of thickness in the 2 nm to 1000 nm range. The effective thermal conductivity of the Al2O3 layer is shown to decrease with thickness down to 70% for the thinnest layers. The data were analyzed upon considering that the change in the effective thermal conductivity corresponds to an intrinsic thermal conductivity associated to an additional interfacial thermal resistance. The intrinsic conductivity and interfacial thermal resistance of SiO2 were found to be equal to 0.95 W/m·K and 5.1 × 10− 9 m2K/W respectively; those of Al2O3 were found to be 1.56 W/m·K and 4.3 × 10− 9 m2K/W

La mobilité des patients et les modèles de création de demande : le cas du Québec

In this paper, we analyse the effects of the inequality in the distribution of medical resources on the use of elective surgeries taking into account the mobility of the patients between geographical areas. In the first part of the paper, we present a theoretical model which analyses the effects of patients' mobility on a private market of chirurgical services and, then, we adapt this model to a regime of public health insurance. In the empirical part of the paper, we discuss shortly the main results in the literature and we present some preliminary results using data from the province of Quebec. Dans ce texte nous analysons les conséquences de l’inégalité dans la distribution des ressources médicales sur l’utilisation des interventions chirurgicales électives en tenant compte de la mobilité des patients. Après avoir présenté un modèle théorique qui permet d’analyser l’influence de la mobilité des patients dans un marché privé d’interventions chirurgicales, nous adaptons ce modèle à un contexte d’assurance-maladie généralisée. Dans la partie empirique de notre travail nous discutons brièvement des principaux résultats que l’on retrouve dans la littérature et nous présentons quelques résultats empiriques préliminaires en utilisant des données du Québec.

Évolution de la concentration en protozoaires et en ammoniaque de fermentations ruminales avec un substrat supplémenté en extraits de plantes à saponines

Yucca schidigera et Quillaja saponaria sont des plantes à saponines (PAS) utilisées en alimentation des ruminants pour optimiser la gestion de l’ammoniaque (NH3) dans le rumen, en particulier lorsque les rations sont riches en azote soluble (e.g. mise à l’herbe, manque d’énergie). Les données sur d’autres PAS sont rares bien que ces métabolites secondaires amphiphiles sont présentes dans beaucoup de végétaux. L’objectif de ce travail était de déterminer in vitro l’effet d’extraits de plantes à saponines sur l’évolution du nombre de protozoaires et sur la concentration en NH3 du fluide ruminal