Raman Spectroscopy of Natural Bone and Synthetic Apatites

Abstract

Raman spectroscopy of natural bones and hydroxyapatites is described. In addition, how Raman spectroscopy has proved crucial in providing baseline data for the modification of synthetic apatite powders that are routinely used now as bone replacement materials is explained. It is important to understand the chemical structural properties of natural bone. Bone consists of two primary components: an inorganic or mineral phase, which is mainly a carbonated form of a nanoscale crystalline calcium phosphate, closely resembling hydroxyapatite, and an organic phase, which is composed largely of type I collagen fibers. Other constituents of bone tissue include water and organic molecules such as glycosaminoglycans, glycoproteins, lipids, and peptides. Ions such as sodium, magnesium, fluoride, and citrate are also present, as well as hydrogenophosphate. Hence, the mineral phase in bone may be characterized essentially as nonstoichiometric substituted apatite. Such a distinction is important in the development of synthetic calcium phosphates for application as skeletal implants. An understanding of bone function and its interfacial relationship to an implant clearly depends on the associated structure and composition. Therefore, it is essential to fully understand the chemical composition of bone, and Raman spectroscopy is an excellent technique for such an analysis.     

Three new [XC(O)NH]P(O)[N(CH2C6H5)2]2 phosphoric triamides (X = CClF2, 3‐F‐C6H4 and 3,5‐F2‐C6H3): a database analysis of tertiary N‐atom geometry in compounds with a C(O)NHP(O)[N]2 core

In the phosphoric triamides N,N,N′,N′‐tetrabenzyl‐N′′‐(2‐chloro‐2,2‐difluoroacetyl)phosphoric triamide, C₃₀H₂₉ClF₂N₃O₂P, (I), N,N,N′,N′‐tetrabenzyl‐N′′‐(3‐fluorobenzoyl)phosphoric triamide, C₃₅H₃₃FN₃O₂P, (II), and N,N,N′,N′‐tetrabenzyl‐N′′‐(3,5‐difluorobenzoyl)phosphoric triamide, C₃₅H₃₂F₂N₃O₂P, (III), the tertiary N atoms of the dibenzylamido groups have sp² character with minimal deviation from planarity. The sums of the three bond angles about the N atoms in (I)–(III) deviate by less than 8° from the planar value of 360°. The geometries of the tertiary N atoms in all phosphoric triamides with C(O)NHP(O)[N]₂ skeletons deposited in the Cambridge Structural Database [CSD; Allen (2002). Acta Cryst. B 58 , 380–388] have been examined and the bond‐angle sums at the two tertiary N atoms (SUM1 and SUM2) and the parameter ΔSUM (= SUM1 − SUM2) considered. It was found that in compounds with a considerable ΔSUM value, the more pyramidal N atoms are usually oriented so that the corresponding lone electron pair is anti with respect to the P=O group. In (I), (II) and (III), the phosphoryl and carbonyl groups, separated by an N atom, are anti with respect to each other. In the C(O)NHP(O) fragment of (I)–(III), the P—N bond is longer and the O—P—N angle is contracted compared with the other two P—N bonds and the O—P—N angles in the molecules. These effects are also seen in analogous compounds deposited in the CSD. Compounds with [C(O)NH]P(O)[N]X (X≠ N), such as compounds with a [C(O)NH]P(O)[N][O] skeleton, have not been considered here. Also, compounds with a [C(O)NH]₂P(O)[N] fragment have not been reported to date. In the crystal structures of all three title compounds, adjacent molecules are linked via pairs of P=O...H—N hydrogen bonds, forming dimers with C_i symmetry.     

A RANS simulation toward the effect of turbulence and cavitation on spray propagation and combustion characteristics

A multidimensional computational fluid dynamic code was developed and integrated with probability density function combustion model to give the detailed account of multiphase fluid flow. The vapor phase within injector domain is treated with Reynolds-averaged Navier–Stokes technique. A new parameter is proposed which is an index of plane-cut spray propagation and takes into account two parameters of spray penetration length and cone angle at the same time. It was found that spray propagation factor (SPI) tends to increase at lower r/d ratios, although the spray penetration tends to decrease. The results of SPI obtained by empirical correlation of Hay and Jones were compared with the simulation computation as a function of respective r/d ratio. Based on the results of this study, the spray distribution on plane area has proportional correlation with heat release amount, NO _x emission mass fraction, and soot concentration reduction. Higher cavitation is attributed to the sharp edge of nozzle entrance, yielding better liquid jet disintegration and smaller spray droplet that reduces soot mass fraction of late combustion process. In order to have better insight of cavitation phenomenon, turbulence magnitude in nozzle and combustion chamber was acquired and depicted along with spray velocity.     

Effects of Mg substitution on the structural and magnetic properties of Co_(0.5)Ni_(0.5-x)Mg_xFe_2O_4 nanoparticle ferrites

In this study, nanocrystalline Co–Ni–Mg ferrite powders with composition Co_(0.5)Ni_(0.5-x)Mg_xFe_2O_4 are successfully synthesized by the co-precipitation method. A systematic investigation on the structural, morphological and magnetic properties of un-doped and Mg-doped Co–Ni ferrite nanoparticles is carried out. The prepared samples are characterized using x-ray diffraction(XRD) analysis, Fourier transform infrared spectroscopy(FTIR), field emission scanning electron microscopy(FESEM), and vibrating sample magnetometry(VSM). The XRD analyses of the synthesized samples confirm the formation of single-phase cubic spinel structures with crystallite sizes in a range of ~ 32 nm to ~ 36 nm. The lattice constant increases with increasing Mg content. FESEM images show that the synthesized samples are homogeneous with a uniformly distributed grain. The results of IR spectroscopy analysis indicate the formation of functional groups of spinel ferrite in the co-precipitation process. By increasing Mg2+substitution, room temperature magnetic measurement shows that maximum magnetization and coercivity increase from ~ 57.35 emu/g to~ 61.49 emu/g and ~ 603.26 Oe to~ 684.11 Oe(1 Oe = 79.5775 A·m-1), respectively. The higher values of magnetization Ms and Mr suggest that the optimum composition is Co_(0.5)N_(i0.4)Mg_(0.1)Fe_2O_4 that can be applied to high-density recording media and microwave devices.     

On matching LTB and Vaidya spacetimes through a null hypersurface

In this work the matching of a LTB interior solution representing dust matter to the Vaidya exterior solution describing null fluid through a null hypersurface is studied. Different cases in which one is able to smoothly match these two solutions to Einstein equations along a null hypesurface are discussed.     

Color center production by femtosecond-pulse laser irradiation in fluoride crystals

Color centers are lattice vacancy defects trapping electrons or holes. They are easily created in single crystals by irradiation with ionizing radiation. We report the production of color centers in LiF and LiYF₄ single crystals by ultrashort high-intensity laser pulses (60 fs, 12.5 GW). An intensity threshold for color center creation of 1.9 and 2 TW/cm² was determined in YLF and LiF, respectively, which is slightly smaller than the continuum generation threshold. Due to the high energy density of the coherent radiation of the focused laser beam, we were able to identify a large amount of F centers, which gave rise to aggregates such as F₂, F ₂ ⁺ , and F ₃ ⁺ . The proposed mechanism of formation is based on multiphoton excitation, which also produces short-lived F ₂ ⁺ centers. It is also shown that it is possible to write tracks in the LiF crystals with dimensional control.     

Experimental investigation on the effect of natural gas premixed ratio on combustion and emissions in an IDI engine

Journal of Thermal Analysis and Calorimetry - Usage of natural gas in an internal combustion engine that has different combustion technologies is considered a possible solution to reduce engine...     

Thermal-exergetic behavior of a vertical double-tube heat exchanger with bubble injection

The use of air bubbles as a heat transfer improvement technique for heat exchangers has been proposed by some researchers. The vertical motion of tiny bubbles because of density difference with liquid provides extra vibration, eddies, turbulences, and consequently further heat transfer rate. The variety of affected parameters, such as injection method, air mass flow rate, bubbles size, number of perforations that forms bubbles, etc., has added to the complexity of this phenomena so that any change in the said parameters significantly influences the thermal-exergetic behavior of the heat exchanger. The quality and quantity of the impact of bubbles on the thermal performance of heat exchangers are different for any type of them. Moreover, each type of heat exchanger requires a specific injection method depending on the heat exchanger structure. In the present research, an injection way is proposed for vertical double-tube heat exchangers, and the effect of bubbles on thermal-exergetic characteristics is experimentally studied and discussed, which have not been performed before. Nondimensional exergy destruction, number of heat transfer units, and effectiveness are the main evaluated parameters in the present paper. Results showed a significant thermal improvement of the heat exchanger under the bubble injection.     

Pharmacophore-Based Virtual Screening,Quantum Mechanics Calculations,and Molecular Dynamics Simulation Approaches Identified Potential Natural Antiviral Drug Candidates against MERS-CoV S1-NTD

Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly infectious zoonotic virus first reported into the human population in September 2012 on the Arabian Peninsula. The virus causes severe and often lethal respiratory illness in humans with an unusually high fatality rate. The N-terminal domain (NTD) of receptor-binding S1 subunit of coronavirus spike (S) proteins can recognize a variety of host protein and mediates entry into human host cells. Blocking the entry by targeting the S1-NTD of the virus can facilitate the development of effective antiviral drug candidates against the pathogen. Therefore, the study has been designed to identify effective antiviral drug candidates against the MERS-CoV by targeting S1-NTD. Initially, a structure-based pharmacophore model (SBPM) to the active site (AS) cavity of the S1-NTD has been generated, followed by pharmacophore-based virtual screening of 11,295 natural compounds. Hits generated through the pharmacophore-based virtual screening have re-ranked by molecular docking and further evaluated through the ADMET properties. The compounds with the best ADME and toxicity properties have been retrieved, and a quantum mechanical (QM) based density-functional theory (DFT) has been performed to optimize the geometry of the selected compounds. Three optimized natural compounds, namely Taiwanhomoflavone B (Amb23604132), 2,3-Dihydrohinokiflavone (Amb23604659), and Sophoricoside (Amb1153724), have exhibited substantial docking energy >−9.00 kcal/mol, where analysis of frontier molecular orbital (FMO) theory found the low chemical reactivity correspondence to the bioactivity of the compounds. Molecular dynamics (MD) simulation confirmed the stability of the selected natural compound to the binding site of the protein. Additionally, molecular mechanics generalized born surface area (MM/GBSA) predicted the good value of binding free energies (ΔG bind) of the compounds to the desired protein. Convincingly, all the results support the potentiality of the selected compounds as natural antiviral candidates against the MERS-CoV S1-NTD.     

Displacement-Based Experimental Stress Analysis of a Circularly-Perforated Asymmetrical Isotropic Structure

This paper demonstrates the ability to determine the individual full-field components of stress, strain and displacement in finite asymmetrical engineering structures from recorded values of a single displacement component while not necessitating differentiation of the measured displacement data; a process which can be ill-conditioned and adversely influenced by data noise and quality. While the present approach of processing recorded displacements with a stress function is not new, previous cases have been restricted to symmetrical scenarios. Full-field displacements are measured here using the digital image correlation (DIC) method. As well as satisfying load equilibrium, the experimental results agree with those predicted using the finite element method (FEM).