Search results for "hell"

Molluscan Shell Proteins: Primary Structure, Origin, and Evolution

2007

In the last few years, the field of molluscan biomineralization has known a tremendous mutation, regarding fundamental concepts on biomineralization regulation as well as regarding the methods of investigation. The most recent advances deal more particularly with the structure of shell biominerals at nanoscale and the identification of an increasing number of shell matrix protein components. Although the matrix is quantitatively a minor constituent in the shell of mollusks (less than 5% w/w), it is, however, the major component that controls different aspects of the shell formation processes: synthesis of transient amorphous minerals and evolution to crystalline phases, choice of the calciu…

Molluscan shell proteins

2004

Abstract The shell secreted by molluscs is one of the most remarkable examples of a matrix-mediated mineralisation performed outside living tissues. The calcifying matrix is a mixture of proteins, glycoproteins, and polysaccharides that precisely self-assemble and control the CaCO 3 polymorph (calcite, aragonite), the size, the shapes of the crystallites, and finally, the texture of the shell. In spite of several biochemical studies, the molecular aspects of the shell building are far from being understood. The present article makes an overview of the most recent molecular data on the proteinaceous components of the shell matrix. These data put into question the classical models of mollusca…

Modeling red coral (Corallium rubrum) and African snail (Helixia aspersa) shell pigments: Raman spectroscopyversusDFT studies

2016

Pigments from red coral (Corallium rubrum) and African snail (Helixia aspersa) shell were studied non-invasively using Raman spectroscopy with 1064-nm laser beam. The two observed bands because of organic pigments confined in biomineralized CaCO3 matrix at about 1500 and 1100 cm−1 were assigned to ν(CC) and ν(C―C), respectively. Both signals originate from polyene(s) of largely unknown structure, containing several conjugated CC bonds. The small peak at 1016 cm−1 in the Raman spectrum of coral pigment was assigned to in-plane ―CH3 rocking or structural deformation of polyene chain because of spatial confinement in the mineral matrix. The organic pigments in red coral and snail shell were pr…

Assessment for the mean value total dressing method: Comparison with coupled cluster including triples methods for BF, NO+, CN+, C2, BeO, NH3, CH2, H…

1997

Limited previous experience with the mean value total dressing (MVTD) method had shown that MVTD energies for closed shell systems are generally better than CCSD(T) ones compared to FCI. The method, previously published as total dressing 2′(td-2′), is based on the single reference intermediate Hamiltonian theory. It is not a CC method but deals in a great part with the same physical effects that CC methods that incorporate amplitudes of triples such as CCSDT or its CCSDT-1n approaches. A number of test calculations comparing to diverse CC methods, as well as FCI and experiment when available, have been performed. The tests concern equilibrium energies in NH3 and CH2, equilibrium energies an…

Valorisation of Cashew Nut Shell Liquid Phenolics in the Synthesis of UV Absorbers

2019

Mixed Ligand Shell Formation upon Catechol Ligand Adsorption on Hydrophobic TiO2 Nanoparticles

2019

Modifying the surfaces of metal oxide nanoparticles (NPs) with monolayers of ligands provides a simple and direct method to generate multifunctional coatings by altering their surface properties. T...

I ‘vasi di Centuripe’: per un approccio integrato

2017

Il contributo intende evidenziare le prospettive di un approccio interdisciplinare integrato allo studio della ceramica policroma “di Centuripe”. Dagli inizi del XX secolo, tale classe ha riscosso ampio apprezzamento per le sue delicate pitture e la ricchezza di ornamenti a rilievo applicati (dipinti e dorati) che abbelliscono i vasi, rendendoli pressoché inutilizzabili nella pratica per scopi funzionali, ma altamente efficaci come doni funerari in antico, e oggi come pezzi di grande impatto per commercianti di antichità e collezionisti moderni. Data la piaga, diffusa fino a tempi recenti, degli scavi clandestini, dei “restauri” arbitrari e delle falsificazioni, i vasi di Centuripe necessit…

Strontium/lithium ratio in aragonitic shells of Cerastoderma edule (Bivalvia) — A new potential temperature proxy for brackish environments

2015

Abstract Quantitative reconstruction of water temperature from shells of bivalve mollusks is still a very challenging task. For example, in highly variable environments such as intertidal zones, shell oxygen isotope values can only provide reliable temperature estimates if the δ18Owater signature during the time of growth is known. Furthermore, trace element-to-calcium ratios such as Sr/Ca or Mg/Ca often do not serve as reliable paleothermometers, because their incorporation into bivalve shells is known to be strongly biologically controlled. Here, we present a potential novel temperature proxy which is based on the Sr/Lishell ratio of the intertidal bivalve Cerastoderma edule. Up to 81% of…

Isotope shifts in natural cerium

2003

High resolution crossed beam resonance fluorescence laser spectroscopy has been performed on an atomic beam of naturally occurring cerium, and isotope shifts have been measured in several transitions. Changes in mean square charge radius, δ〈r 2〉, have been extracted using the King plot technique and show the characteristic increase at the N = 82 neutron shell closure. The measurements form the basis for further investigations of radioactive isotopes and isomers on both sides of the shell closure.

Tropical Temperate Toughs over southern Africa : mechanisms and evolution in response to climate change (2010-2099)

2014

In the Southern Hemisphere, Southern Africa and the south-west Indian Ocean are one of the three preferred regions where interactions between the tropics and midlatitudes develop. This is the South Indian Convergence Zone (SICZ), where northwest-southeast oriented cloud bands form at the synoptic scale (between 3 and 5 days). These bands are mainly found during the austral summer and are commonly referred to as tropical temperate troughs (TTTs). This research aims at improving our knowledge related to TTTs, with a study on the dynamics associated with these systems, and an analysis of their possible evolution during the 21st century.The first part of this thesis aims at identifying favorabl…