Search results for "TLA"
showing 10 items of 1764 documents
Development of a performance threshold approach for identifying the management options for stabilisation/solidification of lead polluted soils
2014
Two soils spiked with lead at different rates were stabilised/solidified using Portland cement and fy ash at different soil:binder ratios, and tested for their setting time, unconfined compressive strength, leachability and durability. A performance threshold approach was used in order to identify optimal management options for the products of the S/S treatment. Results show that soil texture, percentage of binders and lead concentration play an important part in the treatment, significantly influencing the performance of the resulting products in terms of curing, compressive strength and durability. Pb soil concentrations higher than 15000 mg kg-1 were found to heavily reduce the applicab…
SHORT-TERM PROCESSES OF RADIONUCLIDE IMMOBILIZATION IN CEMENT - A CHEMICAL APPROACH
1992
Abstract The ions released in solution by the constituents of cement (principally silicate, aluminate, OH and Ca ions) can combine with the anions and cations from nuclear wastes present in the mixing water to give very insoluble compounds that can fix these ions in the concrete matrix. In order to understand some of the particular physico-chemical processes involved in cement hydration in the presence of analogue elements, tricalcium silicate (C 3 S) was used instead of cement, which is too complex a mixture. It was found that the salt of a chemical analogue, a lanthanide salt, showed some accelerating effects when present in dilute amounts but resulted in large accelerating effects on QS …
Retention of alkali ions by hydrated low-pH cements: Mechanism and Na+/K+ selectivity
2013
Low-pH cements, also referred to as low-alkalinity cements, can be designed by replacing significant amounts of Portland cement by pozzolanic materials. Their pore solution is characterized by a pH near 11, and an alkali concentration much lower than that of Portland cement. This work investigates the retention of sodium and potassium by a hydrated low-pH cement comprising 60% Portland cement and 40% silica fume. It is shown that sorption of potassium is higher than that of sodium and mainly results from counterion charge balancing of the C-S-H negative surface charge. To explain the greater retention of potassium compared to sodium, it is postulated that potassium, unlike sodium, may enter…
A fatal iatrogenic right vertebral injury after transoral odontoidectomy and posterior cervical stabilization for a type II odontoid fracture.
2014
Abstract The authors present a singular case of an iatrogenic right vertebral artery injury, involving a 67 year-old man, who reported a type II odontoid fracture (Anderson and D'Alonzo Classification) and posterior atlantoaxial dislocation following a road traffic accident. A small injury involving the right vertebral artery occurred as a consequence of transoral odontoidectomy and posterior cervical stabilization. It was caused by bone spicules of spinal origin and their presence was confirmed by the histological section of the right vertebral artery at the level of C1–C2. The case confirms how iatrogenic vertebral artery injuries during cervical spine surgery may be potentially lethal, e…
Allelopathic effects of microcystin-LR on the germination, growth and metabolism of five charophyte species and a submerged angiosperm
2013
Abstract Microcystins (MCs) are produced by cyanobacteria in aquatic environments and adversely affect macrophytes at very high concentrations. However, the effects of MC on macrophytes at concentrations of environmental relevance are largely unknown. The main objective of this study was to analyze the allelopathic effects of MC-LR at natural concentrations (1, 8 and 16 μgMC-LR/L) on five charophyte species ( Chara aspera , C. baltica , C. hispida , C. vulgaris and Nitella hyalina ) and the angiosperm Myriophyllum spicatum . Macrophyte specimens were obtained from a restored area located in Albufera de Valencia Natural Park, a protected coastal Mediterranean wetland. Two different experimen…
Charophytes for description and monitoring of inland waters in Sicily
2017
The island of Sicily, in the center of the Mediterranean basin, is a well-known biodiversity hotspot (Médail & Quézel, 1997). Unfortunately, the knowledge of its charophyte flora is absolutely unsatisfactory. The few available data derive from some scattered phytosociological works and some articles published more than 100 years ago. According to the last national synthesis (Bazzichelli & Abdelahad, 2009) a total of 19 Charophytes species should occur in the island, distributed in 4 genera: Chara L. (11), Nitella Agardh (5), Tolypella (A. Braun) A. Braun (2) and Lamprothamnium J. Groves (1). However an updated list of the species occurring in the island, together with their distribu…
Insights into the evolutionary history of the subfamily orthotrichoideae (Orthotrichaceae, Bryophyta): new and former supra-specific taxa so far obsc…
2021
Mosses of the subfamily Orthotrichoideae represent one of the main components of the cryptogam epiphytic communities in temperate areas. During the last two decades, this taxonomical group has undergone an extensive revision that has led to its rearrangement at the generic level. However, their phylogenetic relationships and inferences on the evolutionary patterns that have driven the present diversity have little advanced. In this study, we present a dated molecular phylogenetic reconstruction at the subfamily level, including 130 samples that represent the 12 genera currently recognized within the subfamily, and the analysis of four molecular markers: ITS2, rps4, trnG, and trnL-F. We also…
Variable exposure and immunological response to Lyme disease Borrelia among North Atlantic seabird species.
2008
Colonial seabirds often breed in large aggregations. These individuals can be exposed to parasitism by the tick Ixodes uriae , but little is known about the circulation of pathogens carried by this ectoparasite, including Lyme disease Borrelia . Here we investigated the prevalence of antibodies (Ab) against Borrelia burgdorferi sensu lato in seabird species sampled at eight locations across the North Atlantic. Using enzyme-linked immunosorbent assay tests, we found that the prevalence of anti- Borrelia Ab in adult seabirds was 39.6% on average (over 444 individuals), but that it varied among colonies and species. Common guillemots showed higher seroprevalence (77.1%±5.9) than black-legged …
Epibiota of juvenile Hawksbill Sea Turtles Eretmochelys imbricata stranded in the coast of Rocha Department, Uruguay
2016
The hawksbill turtle (Eretmochelys imbricata) is the most threatened sea turtle species in the world. An important aspect of the biology of sea turtles is the study of colonizing fauna, i.e., their epibiota. The aim of this study is a taxonomic determination on the epibiota found on 4 hawksbills turtles stranded in 2009 and 2011 on the coast of Rocha Department, Uruguay. The epibiota was composed by algae from the class Phaeophyceae (Sphacelaria sp. and Hincksia mitchelliae) and invertebrates from the classes Cirripedia (Platylepas hexastylos, Chelonibia testudinaria and Amphibalanus improvisus) and Hirudinea (Ozobranchus margoi), with greater predominance of P. hexastylos cirripeds (n= 365…
Multitemporal Monitoring of Plant Area Index in the Valencia Rice District with PocketLAI
2016
Leaf area index (LAI) is a key biophysical parameter used to determine foliage cover and crop growth in environmental studies in order to assess crop yield. Frequently, plant canopy analyzers (LAI-2000) and digital cameras for hemispherical photography (DHP) are used for indirect effective plant area index (PAI(eff)) estimates. Nevertheless, these instruments are expensive and have the disadvantages of low portability and maintenance. Recently, a smartphone app called PocketLAI was presented and tested for acquiring PAI(eff) measurements. It was used during an entire rice season for indirect PAI(eff) estimations and for deriving reference high-resolution PAI(eff) maps. Ground PAI(eff) value…