Search results for "Spectroscopy"
showing 10 items of 10293 documents
Hydration Chemistry of Cement Studied by Near Infrared Spectroscopy
2018
Cement is a complex mixture of inorganic compounds which mainly composed of calcium silicates and calcium aluminates. Cement is mixed with water to form concrete. During the mixing calcium silicate hydrate (CSH) and calcium hydroxide are formed. The ratio of water/cement (w/c ratio) is important to obtain a mixture that gives optimum strength to the concrete. In this work, three different cement samples were mixed with water in four different ratios, including 0.35, 0.40, 0.45 and 0.55, respectively. The hydration process of cement was investigated by using near infrared (NIR) spectroscopy over a period of 28 days. The combination frequency of OH stretching and bending of water molecules gi…
Natural fluorapatite as a raw material for Portland clinker
2018
Abstract The present work focuses on the mineralogy and the reactivity of clinkers made from the integration of natural fluorapatite in the raw meals with percentages ranging from 0 up to15%. The samples were characterized by infrared spectrometry, X-ray diffraction and microscopy techniques. The distribution of phosphorous and fluorine into clinkers minerals was determined by MEB/EDS mapping. The mineralogical composition was determined by XRD/Rietveld and the samples reactivity followed by isothermal microcalorimetry. It has been found that fluorine stabilizes C3S and β-C2S which still are found with high levels of P2O5. Cements obtained from up to 8% natural fluorapatite incorporation st…
Quantitative Determination of Calcium Hydroxide by using Near Infrared Spectroscopy
2018
Calcium hydroxide (CH) is a by-product from hydration reaction of cement along with calcium silicate hydrate (C-S-H) gel. It helps to protect the steel reinforcements in concrete structures from corrosion process due to carbonation. The presence of calcium hydroxide provides a basic environment (pH˃10) that induces the formation of passive oxide film and keeps steel structures from corrosion. The detection and quantification of calcium hydroxide in concrete structures are important to understand the nature and state of the steel structures in concretes. In this research work, the variation of calcium hydroxide to calcium silicate ratios in cement were measured by using near-infrared spectro…
MTA HP Repair stimulates in vitro an homogeneous calcium phosphate phase coating deposition
2019
Background To study the mineralization capacity in vitro of the bioceramic endodontic material MTA HP Repair. Material and methods Bioactivity evaluation in vitro was carried out, by soaking processed cement disk in simulated body fluid (SBF) during 168 h. The cement surface was studied by Fourier transform infrared spectroscopy (FT-IR), field emission gun scanning electron microscopy (FEG-SEM) and energy dispersive X-ray analysis (EDX). Release to the SBF media of ionic degradation products was monitored using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Results FT-IR showed increasing formation of phosphate phase bands at 1097, 960, 607 and 570 cm-1 with prolonged SB…
Physicochemical parameters - hydration performance relationship of the new endodontic cement MTA Repair HP
2019
Background To characterize the chemical composition and textural parameters of the MTA Repair HP precursor powder and their influence to hydration performance. Material and methods Un-hydrated precursor material was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), laser diffraction (LD), N2 physisorption and field emission gun scanning electron microscopy (FEG-SEM). Setting time was assessed according to ASTM specification C 266. Hydrated material was analysed by XRD, FT-IR, energy dispersive X-ray (EDX) analysis and FEG-SEM. Results Ca3SiO5 and Ca2SiO4, in addition to CaWO4 as radiopacifier are the main compositional phase…
The MC3 receptor binding affinity of melanocortins correlates with the nitric oxide production inhibition in mice brain inflammation model
2006
Melanocortins possess strong anti-inflammatory effects acting in the central nervous system via inhibition of the production of nitric oxide (NO) during brain inflammation. To shed more light into the role of melanocortin (MC) receptor subtypes involved we synthesized and evaluated some novel peptides, modified in the melanocyte-stimulating hormone (MSH) core structure, natural MCs and known MC receptor selective peptides - MS05, MS06. Since the study included both selective, high affinity binders and the novel peptides, it was possible to do the correlation analysis of binding activities and the NO induction-related anti-inflammatory effect of the peptides. beta-MSH, gamma1-MSH, gamma2-MSH…
Bidirectional Control between Cholesterol Shuttle and Purine Signal at the Central Nervous System.
2022
Recent studies have highlighted the mechanisms controlling the formation of cerebral cholesterol, which is synthesized in situ primarily by astrocytes, where it is loaded onto apolipoproteins and delivered to neurons and oligodendrocytes through interactions with specific lipoprotein receptors. The “cholesterol shuttle” is influenced by numerous proteins or carbohydrates, which mainly modulate the lipoprotein receptor activity, function and signaling. These molecules, provided with enzymatic/proteolytic activity leading to the formation of peptide fragments of different sizes and specific sequences, could be also responsible for machinery malfunctions, which are associated with neurological…
Development of new centrifuges for fast solvent extraction of transactinide elements
1995
The H-0.3 liquid-liquid centrifuge applied for rapid and efficient separation of two liquid phases, and the HG-0.1 gas-liquid centrifuge used to separate the gas phase stemming from a gas jet transportation system and the liquid phase, have been further improved. New centrifuges have been produced of PEEK, a plastic material, which makes them resistant to most aqueous and organic solutions. The performance with respect to time behavior and phase purity is comparable to the titanium centrifuges used so far. The H-0.3 centrifuge has been applied to solvent extraction studies of Zr, Nb, Mo, Hf, Ta, W and Pa from HF solutions into tri-n-octylamine.
Coprecipitation synthesis of Nd:YAG nanopowders II: the effect of Nd dopant addition the on Luminescence Properties
2009
Abstract Nanopowders of Yttrium Aluminium Garnet (Y3Al5O12, YAG) doped with neodymium (Nd:YAG, 0.2–24.0 at.%) were prepared using the co-precipitation method followed by an annealing treatment up to 950 °C. For a concentration of neodymium lower than 3.2 at.% the materials were found constituted by the garnet phase according to X-ray diffraction investigations. However, at higher neodymium loading the hexagonal and monoclinic forms of yttrium aluminium oxides were found together with the garnet phase. For Nd quantity lower than 0.8% the luminescence emission spectra appear to be nearly the same, indicating that in the examined range of composition the immediate surrounding of the emitting N…
Bond strength of lithium disilicate after cleaning methods of the remaining hydrofluoric acid
2020
Background Complex implant treatments have steadily increased within implant prosthodontics. Based on the lower implant mobility, implant impressions need high accuracy in the model transfer to receive a high passive fit within the final prosthodontic restoration. To analyze the accurate 3-dimensional (3D) inter-implant-positions, a reference point is indispensable. However, there is no reference in the patients mouth, so the aim of the present study was to develop a new method based on a custom-made-measuring-aid (CMA) to assess the inter implant dimensions (InID) in patients. Material and Methods Initially an implant master model (IMM/patient equivalent) was digitized by computed tomograp…