Search results for " Sands"
showing 10 items of 10 documents
Bacterial community structure along the subtidal sandy sediment belt of a high Arctic fjord (Kongsfjorden, Svalbard Islands)
2018
Open fjords are subject to contrasting environmental conditions, owing to meltwater glacial inputs, terrestrial runoff, and marine water mass exchanges, which are exacerbated by anthropogenic and climate perturbations. Following a slope-dependent water circulation, the subtidal sandy sediment belt regulates the convergent transport of nutrients downward the fjord depths, and the effective entrapment of suspended particles and microorganisms. In this study, we aimed at testing how glacial and seawater inputs may influence the bacterial community structure of subtidal sand deposits in the Kongsfjorden. Through total and viable cell counting and an amplicon sequencing approach, we found releva…
Mineralogical and chemical variability of fluvial sediments: 1. Bedload sand (Ganga–Brahmaputra, Bangladesh)
2010
This study investigates the natural processes that control concentration of detrital minerals and consequently chemical elements in river sand. The novelty of our approach consists in the systematic integration of detailed textural, petrographical, mineralogical and chemical data, and in the quantitative description and modeling of relationships among mineralogical and chemical variables for each sample and each grain-size class in each sample. Bed sediment in transit in the largest sedimentary system on Earth chiefly consists of fine-grained lithofeldspatho quartzose sand including rich amphibole–epidote–garnet suites, mixed with minor very-fine grained-sand to silt subpopulations containi…
EVOLUZIONE DELLA COMPOSIZIONE GRANULOMETRICA DI SABBIE POMICEE SOTTOPOSTE A COMPRESSIONE 1-D FINO AD ALTE PRESSIONI
2012
Nell’articolo si riportano i risultati di uno studio sperimentale sull’evoluzione della composizione granulometrica di sabbie pomicee sottoposte a compressione 1-D fino a pressioni di 100 MPa. La sperimentazione è stata eseguita su sabbie asciutte con coefficiente di uniformità compreso tra 1.18 e 1.66 e con diametro iniziale dei grani compreso tra 0.18 e 2mm. Il crushing dei grani è significativo per tutte le granulometrie indagate a partire da pressioni efficaci basse (dell’ordine di appena 150 kPa). I risultati della ricerca dimostrano che, anche per queste sabbie dotate di un doppio ordine di pori – intergranulari e intragranulari - esiste una composizione granulometrica limite superior…
Data on phase and chemical compositions of black sands from “El Ostional” beach situated in Mompiche, Ecuador
2020
Abstract Data revealing the phase and chemical compositions of natural black sands from “El Ostional” beach, located in the northern Ecuadorian Pacific coast have been presented. The samples were collected from six points over the shore area of approximately 500 × 40 m2. The data on crystalline phases (iron titanium oxide, orthoclase feldspar and zircon) were determined by X-ray powder diffraction (XRPD), while semi-quantitative chemical analyses of major (Fe and Ti) and trace elements were obtained by X-ray fluorescence spectroscopy (XRF). The phase composition was verified by scanning electron microscopy (SEM), using backscattered electron (BSE) mode and energy dispersive spectroscopy (ED…
Role of particle characteristics in the compression behaviour of gap-graded sands
2019
Abstract The compression in gap-graded mixtures of sands with combined mineralogy has been investigated in recent research, focusing on the key factors that might imply the occurrence of convergent or non-convergent paths in compression (i.e., transitional or non-transitional behaviour). From previous work, the mineralogy of a matrix composed of larger grains seems to determine the possibility of the occurrence of transitional behaviour. Hence, if there is a strong and stiff matrix made of quartz sand particles, which are either larger than or at least of similar size to the other component, then non-convergent compression paths (i.e., transitional behaviour) are likely to occur. As a furth…
Collapsible intact soil stabilisation using non-aqueous polymeric vehicle
2020
Abstract This paper presents the results of an experimental study that had the goal of understanding the effects of treatment with polyethylene glycol (PEG)/nanolime mixtures on collapsible soil behaviour. In a previous study, the use of pure PEG offered a good improvement in the stability of collapsible soil, but the stabilisation effect only lasted for a limited time. To investigate the stabilisation potential of PEG/nanolime systems for collapsible sand, different mixtures were prepared at increasing nanolime weight ratios. The suitability of the stabilised soil was examined on the basis of collapsibility, oedometer, shear, and water vapour permeability tests, and through optical microsc…
ENTREACTO / ENTR?ACTE Un film / A Film Chopin y los Sand, amor a cuatro bandas. Aproximación a la esfera privada de Fryderyk Chopin a partir de la pe…
2021
Two centuries later, the legend Chopin-Sand continues to supply the collective imaginary with vague readings, where historical truthfulness, let alone musical truth, is often contingent on the literary. The much discussed and bellicose romance between the Polish composer and the French novelist, George Sand, tends to some reductionism and evades an obvious reality: Fryderyk Chopin meets George Sand when she was already the mother of two children. This circumstance suggests reformulating certain romantic stereotypes. Jerzy Antczak?s biographical film Pragnienie Mi?o?ci (Chopin: Desire for Love, 2002) does not overlook this detail and makes it one of its narrative axes. The relationship betwe…
The Southeast Asian Lady {Boy}
2021
Singapore, una città-stato dal carattere decisamente cosmopolita, proietta nel mondo un'immagine urbana di frizzante modernità, ricchezza e benessere. All'ombra di potenti landmark architettonici e ai margini di una società opulenta, si nascondono però le condizioni di povertà ed esclusione in cui vive una buona metà della popolazione. Il vero ritratto di Singapore è quindi inciso da una profonda frattura, acuita dalla multietnicità della popolazione. Ed è nell'ambito di questi profondi contrasti, come talvolta può accadere nelle situazioni più estreme, che avvengono straordinari miracoli. Ed ecco che il miracolo è stato compiuto dalla cucina! Nonostante la città sia una delle più care al m…
Unsaturated sand in the stability of the cuesta of the Temple of Hera (Agrigento)
2013
In the Valle dei Templi in Agrigento seven Doric temples stand lengthwise the crest of a rigid calcarenite cuesta over a layer of carbonate sand which lies along a thick stratum of clays. The environment is highly prone to landslides since topplings of calcarenite blocks often occur. The rock slopes are moving back and the slope edge draw near to the foundation of the Temple of Hera Lacinia contributing to increase their perilous condition. To assess the role of unsaturated sands in the instability processes, after the compositional and textural analysis of the material, direct shear tests and oedometer tests have been carried out on sand samples initially at the natural state, with low or …
UNA PROCEDURA AUTOMATIZZATA PER LA DETERMINAZIONE DELLE CARATTERISTICHE MICROSTRUTTURALI DELLE SABBIE MEDIANTE ANALISI DI IMMAGINI DI SEZIONI SOTTILI
2012
È ben noto che il comportamento meccanico microscopico delle sabbie - e in generale dei terreni granulari - trae origine dalle loro caratteristiche microstrutturali, quali, per esempio, il numero di coordinazione dei singoli grani, l’indice di contatto intergranulare (grain contact ratio) e l’indice di addensamento dei grani (packing density index). Appare, quindi, di notevole importanza la determinazione degli indici predetti con alto grado di affidabilità e di ripetibilità. Lo studio dell’assetto dei contatti intergranulari e il calcolo degli indici che lo caratterizzano, viene condotta comunemente su immagini piane dell’insieme di grani mediante esame visuale e restituzione grafica assis…