Statistical treatment of grain-size curves and empirical distributions: densities as compositions?

The preceding two editions of CoDaWork included talks on the possible considerationof densities as infinite compositions: Egozcue and D´ıaz-Barrero (2003) extended theEuclidean structure of the simplex to a Hilbert space structure of the set of densitieswithin a bounded interval, and van den Boogaart (2005) generalized this to the setof densities bounded by an arbitrary reference density. From the many variations ofthe Hilbert structures available, we work with three cases. For bounded variables, abasis derived from Legendre polynomials is used. For variables with a lower bound, westandardize them with respect to an exponential distribution and express their densitiesas coordinates in a basis derived from Laguerre polynomials. Finally, for unboundedvariables, a normal distribution is used as reference, and coordinates are obtained withrespect to a Hermite-polynomials-based basis.To get the coordinates, several approaches can be considered. A numerical accuracyproblem occurs if one estimates the coordinates directly by using discretized scalarproducts. Thus we propose to use a weighted linear regression approach, where all k-order polynomials are used as predictand variables and weights are proportional to thereference density. Finally, for the case of 2-order Hermite polinomials (normal reference)and 1-order Laguerre polinomials (exponential), one can also derive the coordinatesfrom their relationships to the classical mean and variance.Apart of these theoretical issues, this contribution focuses on the application of thistheory to two main problems in sedimentary geology: the comparison of several grainsize distributions, and the comparison among different rocks of the empirical distribution of a property measured on a batch of individual grains from the same rock orsediment, like their composition

Immigració francesa i repressió a la Catalunya del segle XVI: alguns exemples del Comtat d'Empúries

Aquest estudi pretén ser una petita aportació al coneixement del fenomen immigratori francès a la comarca de l' Alt Empordà durant els segles XVI-XVII. L' objectiu principal és donar a conèixer alguns exemples de la magnitud i les característiques d’aquest flux migratori en l’àmbit concret del Comtat d’Empúries, per després, introduir el tema del control i de la repressió que les autoritats catalanes i emporitanes varen exercir sobre aquesta immigració francesa, en particular, durant les dècades centrals del segle XVI

Els professionals de la sanitat a la Catalunya de mitjan segle XIX

Dissertació sobre els professionals de la sanitat a la Catalunya de mitjan segle XIX

La freqüentació dels parcs naturals a Catalunya

This article offers a series of reflections and proposals concerning the visitors usage of Catalonia's Natural Parks. The basis of these affirmations is the analysis of the parks which exist at the present in Catalonia, as well as the study of the current legislation in Catalonia and in Spain. Although the article deals exclusively with protected natural areas, it must be remembered that people's recreational activities affect the entire natural environment. It is therefore necessary to extend planning to the impact of such activities in all natural areas. The author proposes as a possible solution a hierarchy of leisure zones in natural spaces, divided into three different levels: Municipal Parks, Regional Parks as well as Natural and National Parks

La història de Catalunya a Talteüll

L' any 1992, aprofitant les Olimpíades de Barcelona, és l'any en què a Talteüll hi tenen també lloc diferents esdeveniments com la inauguració del nou Museu de Prehistòria de Talteüll i la realilzació d'un cicle de conferències sobre la història de Catalunya

Els Atles comarcals de Catalunya: un producte innovador per a uns continguts tradicionals

La present comunicació pretén ressenyar l’aportació dels Atles comarcals de Catalunya al coneixement del nostre territori com una obra no només de caire acadèmic sinó també divulgatiu i aplicat. En primer lloc, es constata la filiació de l’obra al llegat de la geografia clàssica catalana i a les aportacions tradicionals —monografies i les obres generals― que han disseccionat el país des de l’òptica comarcal. En segon lloc, es detalla el seu procés de concepció i elaboració. Finalment, es destaquen les innovacions que el nou format CD-Rom i les possibilitats d’interacció cartogràfica amb servidors externs suposen en el sentit d’innovació respecte de les aportacions anteriors

Spatial Analysis of Cell Composition Data

A version of Matheron’s discrete Gaussian model is applied to cell composition data.The examples are for map patterns of felsic metavolcanics in two different areas. Q-Qplots of the model for cell values representing proportion of 10 km x 10 km cell areaunderlain by this rock type are approximately linear, and the line of best fit can be usedto estimate the parameters of the model. It is also shown that felsic metavolcanics in theAbitibi area of the Canadian Shield can be modeled as a fractal

Interactions between grain size and composition of sediments: two examples

Two contrasting case studies of sediment and detrital mineral composition are investigated in order to outline interactions between chemical composition and grain size. Modern glacial sediments exhibit a strong dependence of the two parameters due to the preferential enrichment of mafic minerals, especially biotite, in the fine-grained fractions. On the other hand, the composition of detrital heavy minerals (here: rutile) appears to be not systematically related to grain-size, but is strongly controlled by location, i.e. the petrology of the source rocks of detrital grains. This supports the use of rutile as a well-suited tracer mineral for provenance studies. The results further suggest that (i) interpretations derived from whole-rock sediment geochemistry should be flanked by grain-size observations, and (ii) a more sound statistical evaluation of these interactions require the development of new tailor-made statistical tools to deal with such so-called two-way compositions

Benet Sanxes Galindo, pintor i poeta del segle XVI a Catalunya

Estudi de l’obra de Benet Sanxes Galindo, conegut en castellà com Benito Sánchez Galindo. Poeta i pintor del s. XVI, ha estat poc conegut i estudiat. L’autor aprofita per fer un repàs de les obres que l’han tractat. L’article s’emmarca en un número monogràfic amb el títol “Miscel•lània d’homenatge a Modest Prats”

Una Nova dimensió de la xarxa de les ciutats a Catalunya: Les àrees de cohesió

L’article parteix de la hipòtesi de l’existència d'un nou concepte de ciutat. Aquesta ha passat de ser d'una naturalesa nodal o focal a ser-ho de funcionament, de concepte i percepció difusos. L'objectiu principal és determinar l’amplitud d'aquesta ciutat, utilitzant com a paràmetre principal la mobilitat laboral obligada. Es parla de ciutat real, d’àrees de cohesió a Catalunya, i de ciutats reals estructuradores del territori català

Mosques, sants i política a la Catalunya moderna. L’episodi del setge de 1653

Repàs de les posteriors referències en documents d’arxiu al miracle de les mosques als setges de Girona

A Log-linear model of grain size influence on the geochemistry of sediments

Sediment composition is mainly controlled by the nature of the source rock(s), and chemical (weathering) and physical processes (mechanical crushing, abrasion, hydrodynamic sorting) during alteration and transport. Although the factors controlling these processes are conceptually well understood, detailed quantification of compositional changes induced by a single process are rare, as are examples where the effects of several processes can be distinguished. The present study was designed to characterize the role of mechanical crushing and sorting in the absence of chemical weathering. Twenty sediment samples were taken from Alpine glaciers that erode almost pure granitoid lithologies. For each sample, 11 grain-size fractions from granules to clay (ø grades &-1 to &9) were separated, and each fraction was analysed for its chemical composition.The presence of clear steps in the box-plots of all parts (in adequate ilr and clr scales) against ø is assumed to be explained by typical crystal size ranges for the relevant mineral phases. These scatter plots and the biplot suggest a splitting of the full grain size range into three groups: coarser than ø=4 (comparatively rich in SiO2, Na2O, K2O, Al2O3, and dominated by “felsic” minerals like quartz and feldspar), finer than ø=8 (comparatively rich in TiO2, MnO, MgO, Fe2O3, mostly related to “mafic” sheet silicates like biotite and chlorite), and intermediate grains sizes (4≤ø &8; comparatively rich in P2O5 and CaO, related to apatite, some feldspar).To further test the absence of chemical weathering, the observed compositions were regressed against three explanatory variables: a trend on grain size in ø scale, a step function for ø≥4, and another for ø≥8. The original hypothesis was that the trend could be identified with weathering effects, whereas each step function would highlight those minerals with biggest characteristic size at its lower end. Results suggest that this assumption is reasonable for the step function, but that besides weathering some other factors (different mechanical behavior of minerals) have also an important contribution to the trend.Key words: sediment, geochemistry, grain size, regression, step function

Una Proposta d’organització turística del territori: El cas de Catalunya

A la vista dels buits acadèmics detectats, aquest estudi té per objectiu la configuració del mapa de clústers turístics de Catalunya, a partir dels seus productes turístics, tant pel que fa a l’existència actual com al potencial desenvolupament de noves sinèrgies entre els existents, a partir de nous criteris d’organització de l’oferta, fonamentalment per atendre a les noves motivacions de la demanda.Ens fem la pregunta:¿Es poden trobar criteris per al desenvolupament de les destinacions turístiques que permeabilitzin les estructures administratives actuals, i prioritzin criteris de producte, mercat o demanda i d’empresa, garantint la màxima competitivitat i sostenibilitat dels productes turístics resultants?