Search results for "shell"
showing 10 items of 748 documents
Effect of organic matrices on the determination of the trace element chemistry (Mg, Sr, Mg/Ca, Sr/Ca) of aragonitic bivalve shells (<i>Arctica …
2010
The element chemistry of biogenic carbonates can provide important data on past environments. However, the Sr/Ca and Mg/Ca ratios as well as the Mg and Sr concentrations of biological carbonates, especially aragonitic bivalves often depart from apparent thermodynamic equilibrium. When measured in situ by means of LA-ICP-MS, the Mg concentration is often substantially enriched (two- to threefold) near the organic-rich, annual growth lines. To test the hypothesis that some organic components exert a major influence on the skeletal metal content, the element chemistry of different shell components (insoluble organic matrix, IOM; dissolved CaCO3 and soluble organics, SOM) of Arctica islandica w…
Vibrios isolated from the cultured manila clam (Ruditapes philippinarum): numerical taxonomy and antibacterial activities.
2002
Aims: A numerical taxonomic study of halophilic Vibrio isolated from healthy and brown ring disease (BRD) affected manila clams (Ruditapes philippinarum), harvested from the Atlantic coast of south-western Spain, was performed. Methods and Results: Characterization of 123 presumptive Vibrio spp. was carried out using 94 phenotypic tests. Simple matching and Jaccard similarity coefficients were used for numerical analysis. Cluster analysis by the unweighted pair group method with arithmetic averages yielded 15 phena defined at 0.81 similarity. Large phena corresponded to Vibrio tubiashii, V. splendidus biotype I and V. harveyi (phena 1, 5 and 9, respectively). The species V. splendidus bioty…
ASSESSING MERCURY POLLUTION USING BLACK STORK EGGSHELLS
2021
Female birds whose bodies contain environmental contaminants produce eggs with shells that are likewise contaminated, making bird eggshells appropriate indicators for monitoring environmental toxins. Common contaminants include organic mercury compounds, especially methylmercury, which are known to bioaccumulate and biomagnify in the food chain. Black storks (Ciconia nigra) predominantly consume fish and are thus at risk for high mercury intake. In this study, we used eggshells of black storks as a proxy to reconstruct the concentration levels and distribution of mercury, a well-known toxic element, in various parts of Latvia. Preliminary analyses have shown that deposition levels of mercur…
Precise branching ratios to unbound 12C states from 12N and 12B β-decays
2009
6 pages, 2 tables, 4 figures.--PACS nrs.: 21.45.-v; 23.40.-s; 27.20.+n; 21.60.De.--Printed version published Aug 3, 2009
Graphical user interface for serial protocols through a USB link
2012
In this work, a graphical user interface to communicate with three common serial protocols is presented. With one tool, the user may be able to control several evaluation boards from different manufacturers or evaluate and program integrated circuits of complex board prototypes. It provides a user-friendly interface to communicate with several chips using the USB port. The program has been used for the first stages in the qualification process of electronic boards for the Advanced GAmma Tracking Array (AGATA).
Generation and Oligomerization of N-Ferrocenyl Ketenimines via Open-Shell Intermediates
2016
In the presence of oxidant (Ag[SbF6]) and base, N-ferrocenyl thioamide Fc-NHC(S)CH3 (H-1; Fc = Fe(η5-C5H5)(η5-C5H4)) converts in an unexpected multistep reaction sequence to a novel N,S-heterocyclic ring, which initiates an oligomerization reaction. Key intermediates toward the resulting complicated material are Ag6(1)6 silver clusters of the anionic N,S-chelating ligand 1− and EPR-active piano stool complexes resulting from ring-slipped cyclopentadienyl ligands, as well as electrophilic N-ferrocenyl ketenimine Fc-N═C═CH2 (2) and its ferrocenium cation 2•+ formed by hydrosulfide elimination. Mechanistic insight is achieved using X-ray diffraction and mass spectrometry, as well as EPR and NM…
Variety of size and form of GRM2 bacterial microcompartment particles
2021
Bacterial microcompartments (BMCs) are bacterial organelles involved in enzymatic processes, such as carbon fixation, choline, ethanolamine and propanediol degradation, and others. Formed of a semi‐permeable protein shell and an enzymatic core, they can enhance enzyme performance and protect the cell from harmful intermediates. With the ability to encapsulate non‐native enzymes, BMCs show high potential for applied use. For this goal, a detailed look into shell form variability is significant to predict shell adaptability. Here we present four novel 3D cryo‐EM maps of recombinant Klebsiella pneumoniae GRM2 BMC shell particles with the resolution in range of 9 to 22 Å and nine novel 2D class…
Synthesis of gold nanotubes with variable wall thicknesses
2013
We report the synthesis of gold nanotubes with variable wall thicknesses that is accomplished by the deposition of sacrificial hydrophobic polymer cores followed by gold shells within an anodic aluminum oxide template. We demonstrate that by varying polymer core hydrophobicity, the resulting gold shell thickness can be varied. There are two requirements for gold shell formation: (1) the polymer core must be able to be electrodeposited into a tubular (as opposed to wire-like) structure, and (2) the polymer must be hydrophobic, such that it collapses upon exposure to an aqueous solution. An array of gold nanotubes has variable plasmonic properties and can function as a surface enhanced Raman …
Atomistic Simulations of Functional Au_{144}(SR)_{60} Gold Nanoparticles in Aqueous Environment
2012
Charged monolayer-protected gold nanoparticles (AuNPs) have been studied in aqueous solution by performing atomistic molecular dynamics simulations at physiological temperature (310 K). Particular attention has been paid to electrostatic properties that modulate the formation of a complex comprised of the nanoparticle together with surrounding ions and water. We focus on Au-144 nanoparticles that comprise a nearly spherical Au core (diameter similar to 2 nm), a passivating Au-S interface, and functionalized alkanethiol chains. Cationic and anionic AuNPs have been modeled with amine and carboxyl terminal groups and Cl-/Na+ counterions, respectively. The radial distribution functions show tha…
Photoiodocarboxylation of Activated C═C Double Bonds with CO2 and Lithium Iodide
2018
The photolysis at 254 nm of lithium iodide and olefins 1 carrying an electron-withdrawing Z-substituent in CO2-saturated (1 bar) anhydrous acetonitrile at room temperature produces the atom efficient and transition metal-free photoiodocarboxylation of the C═C double bond. The reaction proceeds well for terminal olefins 1 to form the new C-I and C-C σ-bonds at the α and β-positions of the Z-substituent, respectively, and is strongly inhibited by polar protic solvents or additives. The experimental results suggest that the reaction channels through the radical anion [CO2•-] in acetonitrile, yet involves different intermediates in aqueous medium. The stabilizing ion-quadrupole and electron don…