Mechanism of interaction among nanocrystalline carbonate-substituted hydroxyapatite and polar amino-acids for the biomimetic composite technology: Spectroscopic and structural study

This study investigated changes in the interaction of B-type non-stoichiometric nanocrystalline carbonate-substituted hydroxyapatite (nano-CHAP) with polar amino acids (AA) with respect to CHAP-AA linking. Molecular vibrational spectroscopy revealed for the first time that the surface interaction of polar amino acids with defective nano-CHAP is determined not only by the charge state of AA but can be mediated by a foreign ion conjugated with the lateral bonds of amino acids. Understanding this mechanism of CHAP-AA interaction is required for the development of the new generation of dental biomimetic materials based on HAP as well as for their qualitative integration with the amino acid matrix of the dental tissues. © 2020Russian Foundation for Basic Research, RFBR: MK-419.2019.2, 18-29-11008The study was performed under support of Russian Foundation for Basic Research (RFBR) grant №18-29-11008 mk and grant of the President of Russian Federation №MK-419.2019.2

Raman and XANES Spectroscopic Study of the Influence of Coordination Atomic and Molecular Environments in Biomimetic Composite Materials Integrated with Dental Tissue

In this work, for the first time, the influence of the coordination environment as well as Ca and P atomic states on biomimetic composites integrated with dental tissue was investigated. Bioinspired dental composites were synthesised based on nanocrystalline calcium carbonate-substituted hydroxyap-atite (Formula presented) (nano-cHAp) obtained from a biogenic source and a set of po-lar amino acids that modelled the organic matrix. Biomimetic composites, as well as natural dental tissue samples, were investigated using Raman spectromicroscopy and synchrotron X-ray absorption near edge structure (XANES) spectroscopy. Molecular structure and energy structure studies revealed several important features related to the different calcium atomic environments. It was shown that biomimetic composites created in order to reproduce the physicochemical properties of dental tissue provide good imitation of molecular and electron energetic properties, including the carbonate anion CO32− and the atomic Ca/P ratio in nanocrystals. The features of the molecular structure of biomimetic composites are inherited from the nano-cHAp (to a greater extent) and the amino acid cocktail used for their creation, and are caused by the ratio between the mineral and organic components, which is similar to the composition of natural enamel and dentine. In this case, violation of the nano-cHAp stoichiometry, which is the mineral basis of the natural and bioinspired composites, as well as the inclusion of different molecular groups in the nano-cHAp lattice, do not affect the coordination environment of phosphorus atoms. The differences observed in the molecular and electron energetic structures of the natural enamel and dentine and the imitation of their properties by biomimetic materials are caused by rearrangement in the local environment of the calcium atoms in the HAp crystal lattice. The surface of the nano-cHAp crystals in the natural enamel and dentine involved in the formation of bonds with the organic matrix is character-ised by the coordination environment of the calcium atom, corresponding to its location in the CaI posi-tion—that is, bound through common oxygen atoms with PO4 tetrahedrons. At the same time, on the surface of nano-cHAp crystals in bioinspired dental materials, the calcium atom is characteristically lo-cated in the CaII position, bound to the hydroxyl OH group. The features detected in the atomic and molecular coordination environment in nano-cHAp play a fundamental role in recreating a biomimetic dental composite of the natural organomineral interaction in mineralised tissue and will help to find an optimal way to integrate the dental biocomposite with natural tissue. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This work was supported by a grant from the Russian Science Foundation, grant number 21-75-10005; The access to scientific equipment and methodology was provided under support of the Ministry of Science and Higher Education of Russia, Agreement N 075-15-2021-1351

Development of a Visualisation Approach for Analysing Incipient and Clinically Unrecorded Enamel Fissure Caries Using Laser-Induced Contrast Imaging, MicroRaman Spectroscopy and Biomimetic Composites: A Pilot Study

This pilot study presents a practical approach to detecting and visualising the initial forms of caries that are not clinically registered. The use of a laser-induced contrast visualisation (LICV) technique was shown to provide detection of the originating caries based on the separation of emissions from sound tissue, areas with destroyed tissue and regions of bacterial invasion. Adding microRaman spectroscopy to the measuring system enables reliable detection of the transformation of the organic–mineral component in the dental tissue and the spread of bacterial microflora in the affected region. Further laboratory and clinical studies of the comprehensive use of LICV and microRaman spectroscopy enable data extension on the application of this approach for accurate determination of the boundaries in the changed dental tissue as a result of initial caries. The obtained data has the potential to develop an effective preventive medical diagnostic approach and as a result, further personalised medical treatment can be specified. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 21-15-00026; Ministry of Science and Higher Education of the Russian Federation: N 075-15-2021-1351Funding: This work was funded by a grant from the Russian Science Foundation, grant number 21-15-00026. The access to scientific equipment and methodology was provided under support from the Ministry of Science and Higher Education of Russia, agreement N 075-15-2021-1351

Engineering of biomimetic mineralized layer formed on the surface of natural dental enamel

The problem of engineering a biomimetic mineralized layer on the surface of native dental tissue (bio-template) was considered in our work. The formation of the mineralized layer on a biotemplate is achieved with the use of nanocrystalline carbonate-substituted calcium hydroxyapatite (HAp), calcium alkali, and a complex of polyfunctional organic and polar amino acids. By applying the set of structural and spectroscopic methods of analysis we have confirmed the formation of a mineralized biomimetic HAp layer on the surface of bio-template with properties resembling those of natural hard tissue. The thickness of the biomimetic mineralized layer varies from 300 to 500 nm, while the direction of some ncHAp nanocrystals coincides with that of the apatite crystals in the enamel. We also demonstrated that the engineered mineralized HAp layer was characterized by homogeneous micromorphology and enhanced nanohardness in the region of the enamel rods exceeding those of native enamel. The development of a strategy for biomimetic engineering and a technique for enamel surface pre-treatment to enable tissue mineralization has huge potential in dental applications. © 2022 The AuthorsRussian Science Foundation, RSF: 21-75-10005; Ministry of Science and Higher Education of the Russian Federation: N 075-15-2021-1351This work was funded by the Russian Science Foundation , grant number 21-75-10005 ;The access to scientific equipment and methodology was provided under support of the Ministry of Science and Higher Education of Russia, Agreement N 075-15-2021-1351

Interferometry of Direct Photons in Central 280Pb+208Pb Collisions at 158A GeV

Two-particle correlations of direct photons were measured in central 208Pb+208Pb collisions at 158 AGeV. The invariant interferometric radii were extracted for 100<K_T<300 MeV/c and compared to radii extracted from charged pion correlations. The yield of soft direct photons, K_T<300 MeV/c, was extracted from the correlation strength and compared to theoretical calculations.Comment: 5 pages, 4 figure

Systematics of Inclusive Photon Production in 158 AGeV Pb Induced Reactions on Ni, Nb, and Pb Targets

The multiplicity of inclusive photons has been measured on an event-by-event basis for 158 AGeV Pb induced reactions on Ni, Nb, and Pb targets. The systematics of the pseudorapidity densities at midrapidity (rho_max) and the width of the pseudorapidity distributions have been studied for varying centralities for these collisions. A power law fit to the photon yield as a function of the number of participating nucleons gives a value of 1.13+-0.03 for the exponent. The mean transverse momentum, , of photons determined from the ratio of the measured electromagnetic transverse energy and photon multiplicity, remains almost constant with increasing rho_max. Results are compared with model predictions.Comment: 16 pages including 4 figure

Scaling of Particle and Transverse Energy Production in 208Pb+208Pb collisions at 158 A GeV

Transverse energy, charged particle pseudorapidity distributions and photon transverse momentum spectra have been studied as a function of the number of participants (N_{part}) and the number of binary nucleon-nucleon collisions (N_{coll}) in 158 A GeV Pb+Pb collisions over a wide impact parameter range. A scaling of the transverse energy pseudorapidity density at midrapidity as N_{part}^{1.08 \pm 0.06} and N_{coll}^{0.83 \pm 0.05} is observed. For the charged particle pseudorapidity density at midrapidity we find a scaling as N_{part}^{1.07 \pm 0.04} and N_{coll}^{0.82 \pm 0.03}. This faster than linear scaling with N_{part} indicates a violation of the naive Wounded Nucleon Model.Comment: 13 pages, 16 figures, submitted to European Physical Journal C (revised results for scaling exponents

ОФЭК/КТ в диагностике эктопированной аденомы паращитовидной железы (случай из практики)

Case study: a parathyroid tumor ectopic to the mediastinum. The diagnostic capabilities and advantages of the 99mТс-sestamibi SPECT/CT hybrid method in the preoperative localization of abnormally located parathyroma are demonstrated.Случай из практики: опухоль паращитовидной железы, эктопированная в средостение. Продемонстрированы диагностические возможности и преимущества гибридного метода ОФЭКТ/КТ с 99mТс-технетрилом в предоперационной локализации аномально расположенной паратиромы

Flow Measurements via Two-particle Azimuthal Correlations in Au + Au Collisions at sqrt(s_NN) = 130 GeV

Two particle azimuthal correlation functions are presented for charged hadrons produced in Au + Au collisions at RHIC sqrt(s_NN) = 130 GeV. The measurements permit determination of elliptic flow without event-by-event estimation of the reaction plane. The extracted elliptic flow values v_2 show significant sensitivity to both the collision centrality and the transverse momenta of emitted hadrons, suggesting rapid thermalization and relatively strong velocity fields. When scaled by the eccentricity of the collision zone, epsilon, the scaled elliptic flow shows little or no dependence on centrality for charged hadrons with relatively low p_T. A breakdown of this epsilon scaling is observed for charged hadrons with p_T > 1.0 GeV/c for the most central collisions.Comment: 6 pages, RevTeX 3, 4 figures, 307 authors, submitted to Phys. Rev. Lett. on 11 April 2002. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (will be made) publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm