Search results for "Spectroscopy"

Crystallized nano-sized alpha-tricalcium phosphate from amorphous calcium phosphate: microstructure, cementation and cell response

2015

New insight on the conversion of amorphous calcium phosphate (ACP) to nano-sized alpha tricalcium phosphate (α-TCP) provides a faster pathway to calcium phosphate bone cements. In this work, synthesized ACP powders were treated with either water or ethanol, dried, crystallized between 700 and 800 °C, and then cooled at different cooling rates. Particle size was measured in a scanning electron microscope, but crystallite size calculated by Rietveld analysis. Phase composition and bonding in the crystallized powder was assessed by x-ray diffraction and Fourier-transform infrared spectroscopy. Results showed that 50 nm sized α-TCP formed after crystallization of lyophilized powders. Water trea…

X-Ray Diffraction and Multifrequency EPR Study of Radiation-Induced Room Temperature Stable Radicals in Octacalcium Phosphate.

2020

Octacalcium phosphate (OCP) {Ca8H2(PO4)6×5H2O] has attracted increasing attention over the last decade as a transient intermediate to the biogenic apatite for bone engineering and in studies involving the processes of pathological calcification. In this work, OCP powders obtained by hydrolysis of dicalcium phosphate dehydrate were subjected to X- and γ-ray irradiation and studied by means of stationary and pulsed electron paramagnetic resonance at 9, 36 and 94 GHz microwave frequencies. Several types of paramagnetic centers were observed in the investigated samples. Their spectroscopic parameters (components of the g and hyperfine tensors) were determined. Based on the extracted parameters,…

Galvanic deposition and characterization of brushite/hydroxyapatite coatings on 316L stainless steel

2016

In this work, brushite and brushite/hydroxyapatite (BS, CaHPO4·H2O; HA, Ca10(PO4)6(OH)2) coatings were deposited on 316L stainless steel (316LSS) from a solution containing Ca(NO3)2·4H2O and NH4H2PO4 by a displacement reaction based on a galvanic contact, where zinc acts as sacrificial anode. Driving force for the cementation reaction arises from the difference in the electrochemical standard potentials of two different metallic materials (316LSS and Zn) immersed in an electrolyte, so forming a galvanic contact leading to the deposition of BS/HA on nobler metal. We found that temperature and deposition time affect coating features (morphology, structure, and composition). Deposits were char…

Direct determination of calcium, magnesium, sodium, potassium and iron in infant formulas by atomic spectroscopy. Comparison with dry and wet digesti…

1995

An optimization and comparison of three atomic absorption spectroscopic methods for measuring Ca, Mg, Na, K and Fe contents of infant formulas are carried out. The first method is a direct measure of a sample dispersion in water. The second method involves a previous wet digestion (HNO3 + H2O2) in a microwave oven. And finally a dry mineralization at 450 °C is assayed. In order to measure Ca and Mg lanthanum at 0.4% concentration and in the case of Na and K cesium at 0.1% were added. The analytical parameters of the three methods assayed were determined. Results obtained show that the three studied methods are accurace and reliable and no significant difference among them at a probability l…

2020

Endoplasmic reticulum (ER) calcium homeostasis plays an essential role in cellular calcium signaling, intra-ER protein chaperoning and maturation, as well as in the interaction of the ER with other organelles. Calcium is accumulated in the ER by sarco/endoplasmic reticulum calcium ATPases (SERCA enzymes) that generate by active, ATP-dependent transport, a several thousand-fold calcium ion concentration gradient between the cytosol (low nanomolar) and the ER lumen (high micromolar). SERCA enzymes are coded by three genes that by alternative splicing give rise to several isoforms, which can display isoform-specific calcium transport characteristics. SERCA expression levels and isoenzyme compo…

Calibration transfer in chemiluminescence analysis

2001

Abstract Direct standardization (DS) and piecewise direct standardization (PDS) methods are applied to multivariate standardization of chemiluminescence signals using PLS model as the calibration model. The linear concentration interval of the chemiluminescence determination was determined. This interval was located using univariate robust calibration by least median of squares (LMS) method. The linear calibration model was corroborated by conventional least-squares method. The standardization subset and window size were optimized by means of the prediction residual error sum of squares. Several instrumental sources of variability have been studied: the detection cell, instrument, batch ver…

Application of integrative cloud point extraction and concentration for the analysis of polyphenols and alkaloids in mulberry leaves

2018

Abstract A simple and efficient method based on cloud point extraction and concentration combined with high performance liquid chromatography was developed for the simultaneous separation and determination of five target compounds (deoxynojirimycin, chlorogenic acid, rutin, isoquercitrin and astragalin) in mulberry leaves samples. Firstly, to obtain a high extraction rate, the ultrasound assisted extraction was developed on acid modified Triton X-114 system. Under the optimal conditions, the total maximum extraction yields of five target compounds reached 20.80 mg/g, which was superior to conventional solvent extraction. After the cloud point extraction and concentration, the HPLC analysis …

Chemometrics as a Tool of Origin Determination of Polish Monofloral and Multifloral Honeys

2014

The aim of this study was to evaluate the application of chemometrics studies to determine the botanical origin of Polish monofloral honeys using NMR spectroscopy. Aqueous extracts of six kinds of honeys, namely, heather (Calluna vulgaris L.), buckwheat (Fagopyrum esculentum L), lime (Tilia L), rape (Brassica napus L. var. napus), acacia (Acacia Mill.), and multifloral ones, were analyzed. Multivariate chemometric data analysis was performed using principal component analysis (PCA) and orthogonal partial least-squares discriminant analysis (OPLS-DA). Chemometric analysis supported by pollen analysis revealed the incorrect classification of acacia honeys by the producers. Characteristic moti…

Temozolomide and radiotherapy antitumor efficacy evaluation with magnetic resonance imaging and proton magnetic resonance spectroscopy in human gliom…

2008

International audience

Reinvestigation of the synthesis and evaluation of [N-methyl-11C]vorozole, a radiotracer targeting cytochrome P450 aromatase

2009

Abstract Introduction We reinvestigated the synthesis of [ N -methyl- 11 C]vorozole, a radiotracer for aromatase, and discovered the presence of an N -methyl isomer which was not removed in the original purification method. Herein we report the preparation and positron emission tomography (PET) studies of pure [ N -methyl- 11 C]vorozole. Methods Norvorozole was alkylated with [ 11 C]methyl iodide as previously described and also with unlabeled methyl iodide. A high-performance liquid chromatography (HPLC) method was developed to separate the regioisomers. Nuclear magnetic resonance (NMR) spectroscopy ( 13 C and 2D-nuclear Overhauser effect spectroscopy NMR) was used to identify and assign s…