Search results for "Diffraction"
showing 10 items of 1584 documents
Middle Palaeolithic flint procurement in Central Mediterranean Iberia: IMplications for human mobility.
2014
Different flint types from the Middle Palaeolithic site of Abrigo de la Quebrada (Chelva, Valencia) are characterized, both macro- and microscopically, and compared with types found at other localities in the region. Although procurement predominantly concerned the immediate vicinity of sites, our results show the presence of the same types in assemblages separated by distances of up to 120 km. The long distances involved are suggestive of a pattern of North-South mobility of human groups along the coastline of central Mediterranean Iberia.
Microstructure and phase composition of bronze Montefortino helmets discovered Mediterranean seabed to explain an unusual corrosion
2021
AbstractTwo Monterfortino helmets, recovered in the Mediterranean seabed, show unusual features with respect to the more common helmets of the same period and found in underwater environments. Hence, they were investigated by a multi-analytical approach, which allowed us to identify the compounds constituting the helmets and to make some considerations about their metallurgy, although all the metal was converted to degradation products. The helmets, originally made in bronze, have maintained their original shape because of copper sulphides formation. The observed differences in composition between the two helmets were attributed to the position modification, of one of them, into the seabed …
ChemInform Abstract: Crystal Structures of New Ternary Compounds in RE-Pt-Pb and RE-Au-Pb Systems (RE = Rare Earth Metal).
2012
Abstract The crystal structures of the compounds RE 2 Pt 2 Pb (RE = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; Mo 2 FeB 2 structure type, space group P 4/ mbm , Pearson code tP10 ), REPtPb (RE = La, Ce, Pr, Nd, Sm; ZrNiAl structure type, space group P 6 ¯ 2 m , Pearson code hP9 ), RE 2 Au 2 Pb (RE = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; Er 2 Au 2 Sn structure type, space group P 4 2 / mnm , Pearson code tP20 ) and REAuPb (RE = Tm, Yb and Lu) were determined using X-ray powder diffraction.
Synthesis, characterization, crystal structures and in vitro antistaphylococcal activity of organotin(IV) derivatives with 5,7-disubstituted-1,2,4-tr…
2011
Abstract New organotin(IV) complexes of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine ( dbtp ) and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine ( dptp ) with 1:1 and/or 1:2 stoichiometry were synthesized and investigated by X-ray diffraction, FT-IR and 119 Sn Mossbauer in the solid state and by 1 H and 13 C NMR spectroscopy, in solution. Moreover, the crystal and molecular structures of Et 2 SnCl 2 (dbtp) 2 and Ph 2 SnCl 2 (EtOH) 2 (dptp) 2 are reported. The complexes contain hexacoordinated tin atoms: in Et 2 SnCl 2 (dbtp) 2 two 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine molecules coordinate classically the tin atom through N(3) atom and the coordination around the tin atom shows a …
Self-imaging properties of a periodic microlens array: versatile array illuminator realization
1994
Abstract The general features of the wavefield diffracted by a microlens array are described. The transversal periodicity of both a refractive and a diffractive periodic microlens array allows to obtain a set of replicas of the focal intensity distribution along the optical axis of the system, with different multiplicity. The result is applied for implementing a versatile optical array illuminator, with a variable density of bright spots at the output plane. Some experimental results of the procedure are shown.
Upgrading a brightfield optical microscope into a robust numerically advanced interference-based phase imager
2019
The approach to convert a brightfield microscope into an interference-based versatile quantitative phase imaging unit is presented. It employs partially coherent illumination and diffraction grating. Enhanced interferogram bio-phase retrieval is performed by two-shot numerically-robust Hilbert-Huang method.
Analytical and mineralogical studies of ore and impurities from a chromite mineral using X-ray analysis, electrochemical and microscopy techniques
2007
A wide analytical study of South African chromite ore, material with high interest in ceramic industry, has been carried out. With this purpose, an accurate chemical identification and mineralogical characterization of the mineral and the gangue have been performed using X-ray fluorescence (XRF), voltammetry, X-ray diffraction (XRD), light microscopy (LM), and scanning electron microscopy (SEM/EDX). The elemental composition of the sample (ore and gangue) has been obtained by XRF. The voltammetric analysis has allowed to demonstrate that iron in the sample was as Fe(II). The main compound of the chromite ore was a spinel (magnesiochromite ferroan), identified by XRD from the sample, which c…
Stable amorphous calcium carbonate is the main component of the calcium storage structures of the crustacean Orchestia cavimana.
2002
Amorphous calcium carbonate (ACC) is the least stable form of the six known phases of calcium carbonate. It is, however, produced and stabilized by a variety of organisms. In this study we examined calcium storage structures from the terrestrial crustacean Orchestia cavimana, in order to better understand their formation mode and function. By using X-ray diffraction, infrared and Raman spectroscopy, thermal analysis and elemental analysis, we determined that the mineral comprising these storage structures is amorphous calcium carbonate with small amounts of amorphous calcium phosphate (5%). We suggest that the use of amorphous calcium carbonate might be advantageous for these storage struct…
The route to protein aggregate superstructures: Particulates and amyloid-like spherulites.
2015
AbstractDepending on external conditions, native proteins may change their structure and undergo different association routes leading to a large scale polymorphism of the aggregates. This feature has been widely observed but is not fully understood yet. This review focuses on morphologies, physico-chemical properties and mechanisms of formation of amyloid structures and protein superstructures. In particular, the main focus will be on protein particulates and amyloid-like spherulites, briefly summarizing possible experimental methods of analysis. Moreover, we will highlight the role of protein conformational changes and dominant forces in driving association together with their connection w…
Structure of an outer surface lipoprotein BBA64 from the Lyme disease agent Borrelia burgdorferi which is critical to ensure infection after a tick b…
2013
Lyme disease is a tick-borne infection caused by the transmission of Borrelia burgdorferi from infected Ixodes ticks to a mammalian host during the blood meal. Previous studies have shown that the expression of B. burgdorferi surface-localized lipoproteins, which include BBA64, is up-regulated during the process of tick feeding. Although the exact function of BBA64 is not known, this lipoprotein is critical for the transmission of the spirochete from the tick salivary glands to the mammalian organism after a tick bite. Since the mechanism of development of the disease and the functions of the surface lipoproteins associated with borreliosis are still poorly understood, the crystal structur…