Search results for "Underwater"

Delamination and recycling of Archaean crust caused by gravitational instabilities

2013

The volume of Archaean crust preserved at Earth’s surface today is low. Thermodynamic calculations and geodynamic modelling show that the thick, primary crust that would have formed on a much hotter Archaean Earth was denser than the underlying mantle, and would have therefore been recycled back into the mantle as drips.

Innovative experimental approaches applied to the study of ceramics from underwater archaeological excavations

2012

Definition of analytical cleaning procedures for archaeological pottery from underwater environments: The case study of samples from Baia (Naples, So…

2021

Abstract This work is focused on a multidisciplinary study of 13 pottery fragments collected in the submerged archaeological site of Baia (Naples, Italy). Founded by the Romans in the 1st century B.C., this archaeological area represents one of the greatest evidences of Roman architecture and it includes ancient ruins whose structures range from maritime villas and imperial buildings. Several diagnostic tests were carried out in order to characterize the archaeological materials, their structure and properties, as well as the alteration and degradation products. Degradation forms in seawater imply not only a variation in the physico-mechanical and chemical properties of the material but als…

Aportación de nuevas metodologías multitécnica en el estudio y conservación de patrimonio numismático de procedencia subacuática

2019

Este trabajo presenta un estudio del estado de conservación de monedas con base de cobre procedente del Museo Nacional de Arqueología Subacuática. La metodología multitécnica incluye instrumentación convencional como microscopía óptica, espectroscopia FTIR y técnicas avanzadas nanoinvasivas como voltamperometría de micropartículas y haz de iones focalizados-FESEM-EDX. Así se ha podido identificar el tipo de aleación, productos de corrosión, depósitos superficiales y antiguas intervenciones. Cabe señalar la identificación de mecanismos de alteración atípicos como la formación de complejos carboxilados de iones metálicos generados en los procesos electroquímicos de corrosión del metal o aleac…

Performance Analysis of Sweep-Spread Carrier (S2C) Modulation for Underwater Communications

2022

In the last decades, underwater acoustic communications have seen a growing development with a variety of research as well as commercial applications, dealing with channel distortions, multipath and Doppler effects typical underwater channels. A very robust modulation able to guarantee connectivity in harsh environments (where spectral efficient solutions such as OFDM can be prevented) is the so called sweep-spread carrier (S2C) modulation, which is based on the usage of a linearly time-varying carrier. Underwater modems based on S2C modulations have been patented and successfully adopted in real-world deployments. In this paper, we analyze the performance of S2C both in simulation and infi…

Deep conservation of bivalve nacre proteins highlighted by shell matrix proteomics of the Unionoida Elliptio complanata and Villosa lienosa.

2016

The formation of the molluscan shell nacre is regulated to a large extent by a matrix of extracellular macromolecules that are secreted by the shell-forming tissue, the mantle. This so-called ‘calcifying matrix’ is a complex mixture of proteins, glycoproteins and polysaccharides that is assembled and occluded within the mineral phase during the calcification process. Better molecular-level characterization of the substances that regulate nacre formation is still required. Notable advances in expressed tag sequencing of freshwater mussels, such as Elliptio complanata and Villosa lienosa , provide a pre-requisite to further characterize bivalve nacre proteins by a proteomic approach. In this…

Harmonizing circumpolar monitoring of Arctic fox: benefits, opportunities, challenges and recommendations.

2017

Source at http://dx.doi.org/10.1080/17518369.2017.1319602 The biodiversity working group of the Arctic Council has developed pan-Arctic biodiversity monitoring plans to improve our ability to detect, understand and report on long-term change in Arctic biodiversity. The Arctic fox (Vulpes lagopus) was identified as a target of future monitoring because of its circumpolar distribution, ecological importance and reliance on Arctic ecosystems. We provide the first exhaustive survey of contemporary Arctic fox monitoring programmes, describing 34 projects located in eight countries. Monitored populations covered equally the four climate zones of the species’ distribution, and there were large dif…

European Sea Bass (Dicentrarchus labrax) immune status and disease resistance are impaired by arginine dietary supplementation

2015

Infectious diseases and fish feeds management are probably the major expenses in the aquaculture business. Hence, it is a priority to define sustainable strategies which simultaneously avoid therapeutic procedures and reinforce fish immunity. Currently, one preferred approach is the use of immunostimulants which can be supplemented to the fish diets. Arginine is a versatile amino acid with important mechanisms closely related to the immune response. Aiming at finding out how arginine affects the innate immune status or improve disease resistance of European seabass (Dicentrarchus labrax) against vibriosis, fish were fed two arginine-supplemented diets (1% and 2% arginine supplementation). A…

Magmatic gas percolation through the old lava dome of El Misti volcano

2017

International audience; The proximity of the major city of Arequipa to El Misti has focused attention on the hazards posed by the active volcano. Since its last major eruption in the fifteenth century, El Misti has experienced a series of modest phreatic eruptions and fluctuating fumarolic activity. Here, we present the first measurements of the compositions of gas emitted from the lava dome in the summit crater. The gas composition is found to be fairly dry with a H2O/SO2 molar ratio of 32 ± 3, a CO2/SO2 molar ratio of 2.7 ± 0.2, a H2S/SO2 molar ratio of 0.23 ± 0.02 and a H2/SO2 molar ratio of 0.012 ± 0.002. This magmatic gas signature with minimal evidence of hydrothermal or wall rock int…

Metallic nanoparticle enrichment at low temperature, shallow CO2 seeps in Southern Italy

2012

We report on metal enrichment along a natural pH gradient owing to increased CO2 degassing at cold, shallow seeps of Vulcano Island in the Mediterranean Sea, off Sicily. We assessed composition of unfiltered and filtered seawater (<100 nm) along acidic zones ranging between ambient and pH 5, and showed that most seep derived elements are present as nanoclusters which then aggregate into larger colloids while mixing with ambient seawater along a pH gradient. Size and elemental composition of such naturally occurring nanoparticles assessed by modern characterisation methods were in good agreement with the results from conventional analytical methods. We provide analytical evidence for the pre…