Search results for " suction"
showing 10 items of 15 documents
Importance of meteorological variables for aeroplankton dispersal in an urban environment
2016
Passive wind dispersal is one of the major mechanisms through which organisms disperse and colonize new areas. The detailed comprehension of which factors affect this process may help to preserve its efficiency for years to come. This is especially important in the current context of climate change, which may seriously alter weather regimes that drive dispersal, and is crucial in urban contexts, where biodiversity is dramatically threatened by pollution and fragmentation of natural patches. Despite its interest, the analysis of factors affecting aeroplankton dispersal in urban environments is rare in literature. We sampled aeroplankton community uninterruptedly every 4 hours from 17th May t…
Waste activated sludge dewaterability: comparative evaluation of sludge derived from CAS and MBR systems
2016
Nowadays, sludge dewatering is one of the greatest operational cost to wastewater treatment cycle. Specifically, 1t of fresh sludge to be disposed is composed, on average, by 0.25 - 0.30t of suspended solids, with an average cost for treatment and disposal around 280 - 470 €/t of suspended solids. Despite several technologies have been developed with the focus to reduce also the specific sludge production, still mechanical dewatering represents a crucial step to limit the amount of sludge to be disposed. Many physical–chemical parameters influence the sludge dewaterability: floc structure, particle size, bound water content, surface charge and hydrophobicity, Extracellular Polymeric Substan…
The open metastable structure of a collapsible sand: fabric and bonding
2015
This paper deals with the compositional and textural characteristics determining open metastable structures in the pleistocenic sand outcropping in the Agrigento district (Sicily). The aim of the study was to individuate the bonding types occurring between grains that could generate matric suction phenomena. The composition and microfabric were characterised by means of granulometry, porosimetry, permeability, optical and ESEM-EDS microscopy, thermogravimetry and XR diffractometry, electric conductivity, and ionic chromatography. The data thus acquired show that the skeleton of the sand is constituted mostly by bioclasts and microfossils, calcite and quartz monocrystalline grains. Moreover,…
Generalized effective stress concept for saturated active clays
2021
Experimental evidence shows that changes in pore-water chemistry can significantly affect the mechanical behavior of saturated active clays. Despite this evidence, how the chemical composition of the pore water can be considered in effective stress definition is questionable. This paper develops the concept of generalized effective stress for active clays. To this end, physicochemical studies on water–clay mineral interactions are used to clearly define the different types of ions and water present in an active clay. In particular, the presence of both movable and non-movable ions within the liquid water is highlighted. Taking this into account, thermodynamic and geochemistry principles ar…
TRANSCRANIAL DIRECT CURRENT STIMULATION ENHANCES SUCKING OF A LIQUID BOLUS IN HEALTHY HUMANS
2014
Abstract Background Transcranial direct current stimulation (tDCS) is a non-invasive technique used for modulating cortical excitability in vivo in humans. Here we evaluated the effect of tDCS on behavioral and electrophysiological aspects of physiological sucking and swallowing. Methods Twelve healthy subjects underwent three tDCS sessions (anodal, cathodal and sham stimulation) on separate days in a double-blind randomized order. The active electrode was placed over the right swallowing motor cortex. Repeated sucking and swallowing acts were performed at baseline and at 15 and 60 min after each tDCS session and the mean liquid bolus volume ingested at each time point was measured. We also…
An experimental and constitutive investigation on the chemo-mechanical behaviour of a clay
2013
Engineering issues for which the understanding of the chemo-mechanical behaviour of soils is relevant include wellbore stability problems, the salinification of groundwater, and nuclear waste storage. However, despite the vast number of situations in which couplings between chemistry and mechanics occur, the available constitutive models rely on limited experimental evidence. This paper presents the results of an experimental programme on the chemo-mechanical behaviour of a non-swelling illite. The osmotic suction is controlled through the ion concentration of sodium chloride in the pore water. Stress paths include mechanical loading at a constant osmotic suction, and an increasing osmotic …
Role of Stress History on the Swelling-Shrinkage Behavior of Compacted Scaly Clay
2022
Compacted scaly clays are complex geomaterials widely used for the realization of dam cores and waste dump liners. This research aims to investigate the swelling/shrinkage behavior of these geomaterials subjected in an oedometric cell to complex hydromechanical stress paths, including different sequences of cyclic variations of suction and stress. Microstructure investigations, based on scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) techniques, highlighted the microstructural characteristics of the material, which are the distinctive microfabric features (particles assemblages and scales) and the double-porosity networks, where micro- and macropores coexist. More…
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 …
The role of slabs and oceanic plate geometry in the net rotation of the lithosphere, trench motions, and slab return flow
2012
[1] Absolute plate motion models with respect to a deep mantle reference frame (e.g., hot spots) typically contain some net rotation (NR) of the lithosphere. Global mantle flow models for the present-day plate setting reproduce similarly oriented NRs but with amplitudes significantly smaller than those found in some high NR Pacific hot spot reference frames. It is therefore important to understand the mechanisms of NR excitation, which we attempt here with two-dimensional cylindrical models of an idealized Pacific domain. We study the influence of slab properties, oceanic ridge position, continental keels, and a weak asthenospheric layer on NR and trench migration. Fast slab return flow dev…
Wound drainages in total hip arthroplasty: to use or not to use? Review of the literature on current practice.
2013
Aim of this study is to analyze data reported in literature concerning the efficacy of using wound low-vacuum suction drainages in orthopedic surgery after total hip arthroplasty. We analyzed studies concerning the use of drainages in prosthetic hip replacement surgery, performing our research through Pubmed, Cochrane database and Google Scholar, and selecting the ones evaluating the following parameters: bleeding, the need for blood transfusions, number or reinforcement of post-operative medications, length of hospitalization, functional results, periprosthetic and surgical wound infection, post-operative hematoma. Our review did not show any demonstrated advantage from the use of wound dr…