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1.
R. A. Young M. L. Bartlett S. Spooner P. E. Mackie G. Bonel 《Journal of biological physics》1981,9(1):1-26
Parallel experiments on human tooth enamel with sp.g. >2.95 and synthetic hydroxyapatite have been carried out to study the substitution of CO
3
2–
for OH–, produced at 1000°C in dry CO2, with the complementary use of neutron diffraction, x-ray diffraction, infrared spectroscopy and thermochemical techniques. It was verified that the substitution (i) is CO
3
2–
2(OH– and is completely reversible on specimen exposure to H2O vapor at 1000°C, (ii) takes place with the carbon atom on or near the hexad axis, (ii) places one CO
3
2–
group per unit cell in an ordered fashion and so changes the space group fromP6
3/m to one without a screw axis, (iii) was consistent, by its incompleteness, with the occurrence of substitution of O2– for 2(OH–) in 25 to 40% of the unit cells, (iv) produced similar marked changes in the neutron powder diffraction patterns of both tooth enamel and hydroxyapatite, and (v) took place at a site where only a minor portion of the CO
3
2–
in normal untreated human tooth enamel occurs. From comparative Rietveld analysis results from x-ray and neutron powder diffraction patterns it is suggested that the carbon atom of this A-site CO
3
2–
is near 0,0,0.12 and the CO
3
2–
plane makes an angle of 18° with thec direction.On being heated at 400°C in H2O vapor, tooth enamel retained much of its CO
3
2–
but its a lattice parameter changed from 9.445(3) Å to 9.420(1) Å, essentially that of hydroxyapatite. After once being heated at high temperatures, tooth enamel and hydroxyaptite showed similar responses to various treatments, including carbonation. After heating, more -Ca3(PO4)2 was found in the tooth enamel specimen. Comparative weight change, IR, and other data for tooth enamel and hydroxyapatite heated in He, then in CO2, and then in H2O vapor showed a 20% or more deficiency of structural OH– in the untreated tooth enamel. 相似文献
2.
An X-ray diffraction microanalytical method, in which sample is loaded onto a silver membrane filter, was applied to assess the crystal content in tooth enamel. Each enamel powder was first examined at room temperature, and then examined again at intervals after heating to 200, 400, 600, 800, and 1000 degrees C. The hydroxyapatite composition weight and crystal weight of the samples were derived from the standard calibration curves. The "crystal content ratio" was defined as the ratio of crystal weight to sample weight. The following results were obtained: (1) beta-tricalcium phosphate (beta-TCP) replaced the hydroxyapatite after heating at the high temperatures; (2) the "crystal content ratio" in the tooth enamel increased with the rise in temperature; and (3) the lattice parameters of the enamel apatite and the beta-TCP were changed by the heating. The X-ray diffraction technique has the potential to analyze the crystal content using milligram samples. 相似文献
3.
A novel blue‐emitting Sr3.5Y6.5O2(PO4)1.5(SiO4)4.5:Eu2+ phosphor was synthesized via a solid‐state reaction. Powder X‐ray diffraction (XRD) analysis demonstrated that the Sr3.5Y6.5O2(PO4)1.5(SiO4)4.5 host had a hexagonal crystal structure in the space group P63/m and unit cell parameters a = 9.418 Å, c = 6.900 Å. The as‐prepared phosphor showed a blue emission and all the main emission peaks were located at around 466 nm for different excitation wavelengths of 297, 333 and 391 nm. The temperature dependence of the photoluminescence property was investigated in the range 20–250 °C, and the emission intensity decreased to 71% of the initial value at room temperature on increasing the temperature to 150 °C. According to the classical theory of fluorescent thermal quenching, the activation energy (ΔE) for the thermal quenching luminescence of the as‐prepared Sr3.45Y6.5O2(PO4)1.5(SiO4)4.5:0.05Eu2+ phosphor was determined to be 0.20 eV. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
4.
Characterization of the calcium biomineral in the radular teeth of Chiton pelliserpentis 总被引:2,自引:0,他引:2
The radula in a group of molluscan invertebrates, the chitons (Polyplacophora), is a ribbon-like apparatus used for feeding and which bears a series of distinctive mineralized teeth called the major lateral teeth. While some chiton species deposit only iron biominerals in these teeth, many others deposit both iron and calcium. In this study, the calcium biomineral in the teeth of one of the latter types of species, the Australian east-coast chiton, Chiton pelliserpentis, has been isolated and examined for the first time. Spectroscopic and crystallographic techniques have identified the biomineral as a carbonate-substituted apatite with significant fluoride substitution also likely. Fourier-transform infrared and laser Raman spectroscopy indicated that the carbonate content was less than that of either bovine tibia cortical bone or human tooth enamel. X-ray diffraction analysis showed the biomineral to be poorly crystalline due to small crystal size and appreciable anionic substitution. The lattice parameters were calculated to be a=9.382?Å and c=6.883?Å, which are suggestive of a fluorapatite material. It is postulated that structural and biochemical differences in the tooth organic matrix of different chiton species will ultimately determine if the teeth become partly calcified or iron mineralized only. 相似文献
5.
Tooth enamel samples from molar teeth of camel were prepared using a combined procedure of mechanical and chemical tooth treatment. Based on electron paramagnetic resonance (EPR) spectroscopy, the dose response of tooth enamel samples was examined and compared to that of human enamel. The EPR dose response of the tooth enamel samples was obtained through irradiation to gamma doses from 1 Gy up to 100 kGy. It was found that the radiation-induced EPR signal increased linearly with gamma dose for all studied tooth enamel samples, up to about 15 kGy. At higher doses, the dose response curve leveled off. The results revealed that the location of the native signal of camel tooth enamel was similar to that of enamel from human molars at 2.00644, but different from that of enamel from cows and goats. In addition, the peak-to-peak width (ΔH pp) for human and camel molar teeth was similar. It was also found that the response of camel enamel to gamma radiation was 36% lower than that of human enamel. In conclusion, the results indicate the suitability of camel teeth for retrospective gamma dosimetry. 相似文献
6.
Ce3+/Eu2+ co‐doped Na3Ca6(PO4)5 phosphors were prepared using a combustion‐assisted synthesis method. X‐Ray powder diffraction (XRD) analysis confirmed the formation of a Na3Ca6(PO4)5 crystal phase. Na3Ca6(PO4)5:Eu2+ phosphors have an efficient bluish‐green emission band that peaks at 489 nm, whereas Ce3+‐doped Na3Ca6(PO4)5 showed a bright emission band at 391 nm. Analysis of the experimental results suggests that enhancement of the Eu2+ emission intensity in co‐doped Na3Ca6(PO4)5:Eu2+,Ce3+ phosphors is due to a resonance‐type energy transfer from Ce3+ to Eu2+ ions, which is predominantly governed by an exchange interaction mechanism. These results indicate that Ce3+/Eu2+ co‐doped Na3Ca6(PO4)5 is potentially useful as a highly efficient, bluish‐green emitting, UV‐convertible phosphor for white‐light‐emitting diodes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
7.
Ping Li 《Inorganica chimica acta》2011,378(1):323-325
A novel mixture cations templated indium phosphates, Li(C2N2H10)[In2(HPO4)3(PO4)], has been synthesized under mild hydrothermal conditions and characterized by elemental analysis and FT-IR spectrum. The crystal structure of title compound was determined by single crystal X-ray diffraction data. It belongs to monoclinic, space group P2/n with unit cell dimension a = 9.4692(13) Å, b = 9.1622(12) Å, c = 9.7063(14) Å, β = 117.5620(10)°. Its structure is characterized as a three-dimensional open-framework with 8-membered ring channels along a axis, where the inorganic lithium cation and organic double-protonated ethylenediamine cation are located and interact with the framework both electrostatically and via hydrogen bonds of N-H?O. 相似文献
8.
Reaction of (acetonitrile)-nona(carbonyl)-di-manganese and tri-iso-propyl phosphite provided the new phosphite compound [Mn2(CO)9L]. The product was fully characterized and the molecular structure was determined by single crystal X-ray diffraction. This represents the first structural analysis of a di-manganese carbonyl compound containing phosphite ligands. In addition, this compound displays a rare example of an equatorially substituted di-manganese carbonyl compound. 相似文献
9.
Fluorophosphates from Solid‐State Synthesis and Electrochemical Ion Exchange: NaVPO4F or Na3V2(PO4)2F3?
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Long Li Youlong Xu Xiaofei Sun Rui Chang Yuan Zhang Xiaona Zhang Ju Li 《Liver Transplantation》2018,8(24)
Vanadium‐based fluorophosphates are promising sodium‐ion battery cathode materials. Different phases of NaVPO4F and Na3V2(PO4)2F3 are reported in the literature. However, experiments in this work suggest that there could be confusions about the single‐phase NaVPO4F in solid‐state synthesis. Here, systematic investigation of the mechanism underlying structural and compositional evolution of solid‐state synthesis (NaF:VPO4 = 1:1) is determined by in situ and ex situ X‐ray diffraction and electrochemical measurements. Three reactions—3NaF + 3VPO4 → Na3V2(PO4)2F3 + VPO4 (up to 500 °C), Na3V2(PO4)2F3 + VPO4 → Na3V2(PO4)3 + VF3↑ (600–800 °C), and 2Na3V2(PO4)3 → 2(VO)2P2O7 + Na4P2O7 + amorphous products (above 800 °C)—are validated by in situ XRD and thermogravimetric analysis/differential scanning calorimetry. None of the products reported in this work is consistent with single‐phase NaVPO4F at any temperature. It is speculated that the assignments of I4/mmm and C2/c NaVPO4F from solid‐state synthesis are incorrect, which are instead multiphase mixtures of Le Meins' Na3V2(PO4)2F3, unreacted VPO4, and hexagonal Na3V2(PO4)3. Liquid‐electrolyte‐based electrochemical ion exchange of LiVPO4F produces a tavorite NaVPO4F structure, which is very different from Le Meins' family of Na3Al2(PO4)2F3 polymorphs. 相似文献
10.
Greg Brewer Stephen Drucker Jaymee Girard Charles Grisham Ekk Sinn 《Inorganica chimica acta》1984,89(2):105-111
The title compound, Co(NH3)5PO4, prepared by a modified literature procedure, was used to study the inhibition of Na+-K+ ATPase and to serve as a structural model for ML4(nucleotide) complexes. The structure was determined by single crystal X-ray diffraction techniques. The crystals are monoclinic, space group P21/n, a = 8.638(3), b = 14.517(2), c = 9.145(2) Å, and β = 112.71(2)°. The structure, solved by the heavy atom method to an R value of 3.3% for 1924 reflections, consists of a slightly distorted octahedron with the cobalt bound to the five amines and a monodentate phosphate. Solution structural data is taken from 31P NMR measurements. From comparison with other metal phosphate complexes it is concluded that multiple monodentate coordination of a di- or triphosphate closely resembles the coordination of a monophosphate This is based on the similarity of the MO bond angle which is 129.6° in the present example. 相似文献
11.
Ding-Bang Xiong Lubomir D. Gulay Hao-Hong Chen Jing-Tai Zhao 《Inorganica chimica acta》2009,362(9):3013-3018
A new compound Gd4(H2O)5(HPO3)6 (1) was isolated from the reaction of gadolinium chloride GdCl3 · nH2O with H3PO3 under hydrothermal conditions. The crystal structure was solved by means of single-crystal X-ray diffraction. The structure is composed of parallel gadolinium-oxygen polyhedra chains connected by phosphite ions, and shows three-dimensional (3D) open-framework with eight-membered ring (8MR) channels. The structure is different from its counterpart Eu2(H2O)2.5(PO3H)3 due to the effect of lanthanide contraction. The intensive intrinsic UV emission of this compound at λmax = 312 nm comes from the spin-forbidden 6P7/2 → 8S7/2 f-f transition of the Gd3+ ions. No magnetic order was observed for this compound. 相似文献
12.
G. Micera L. Strinna Erre F. Cariati D.A. Clemente A. Marzotto M.Biagini Cingi 《Inorganica chimica acta》1985,109(2):135-139
The crystal and molecular structure of the complex [UO2(DHB)2(H2O)2]·8H2O (DHB = 2,6-di- hydroxybenzoato) has been determined from single- crystal X-ray analysis and refined to a final R value of 0.033 for 3620 observed reflections. The complex crystallizes in the monoclinic system, space group C2/m, with a = 6.704(3), b = 20.171(6), c = 9.454(4) Å and Z = 2. The coordination about the uranyl group, which is linear, involves two bidentate carboxylate groups and two water molecules in trans positions giving rise to an irregular hexagonal bipyramid. Intra- molecular hydrogen bonds between phenolic and carboxylate groups forming six-membered rings allow the molecule to be nearly planar. Spectroscopic (IR, NMR and electronic absorption) data and thermal properties of the compound are also reported. 相似文献
13.
Benazzi S Fornai C Bayle P Coquerelle M Kullmer O Mallegni F Weber GW 《Journal of human evolution》2011,61(3):320-326
Traditional morphometric approaches for taxonomic assignment of Neanderthal and modern human dental remains are mainly characterized by caliper measurements of tooth crowns. Several studies have recently described differences in dental tissue proportions and enamel thickness between Neanderthal and modern human teeth. At least for the lower second deciduous molar (dm2), a three-dimensional lateral relative enamel thickness index has been proposed for separating the two taxa. This index has the advantage over other measurements of being applicable to worn teeth because it ignores the occlusal aspect of the crown. Nevertheless, a comparative evaluation of traditional crown dimensions and lateral dental tissue proportion measurements for taxonomic assignment of Neanderthal and modern human dm2s has not yet been performed.In this study, we compare various parameters gathered from the lateral aspects of the crown. These parameters include crown diameters, height of the lateral wall of the crown (lateral crown height = LCH), lateral enamel thickness, and dentine volume of the lateral wall, including the volume of the coronal pulp chamber (lateral dentine plus pulp volume = LDPV), in a 3D digital sample of Neanderthal and modern human dm2s to evaluate their utility in separating the two taxa.The LDPV and the LCH allow us to discriminate between Neanderthals and modern humans with 88.5% and 92.3% accuracy, respectively. Though our results confirm that Neanderthal dm2s have lower relative enamel thickness (RET) index compared with modern humans (p = 0.005), only 70% of the specimens were correctly classified on the basis of the RET index. We also emphasize that results of the lateral enamel thickness method depend on the magnitude of the interproximal wear. Accordingly, we suggest using the LCH or the LDPV to discriminate between Neanderthal and modern human dm2s. These parameters are more independent of interproximal wear and loss of lateral enamel. 相似文献
14.
Tong Ren Damon A. Parrish Jeffrey R. Deschamps Guo-Lin Xu Martin H. Moore Steven K. Pollack A.P. Sattelberger 《Inorganica chimica acta》2004,357(4):1313-1316
The reaction between Os2(OAc)4Cl2 and Hap (Hap is 2-anilinopyridine) under prolonged refluxing conditions resulted in a new Os2(III) compound, Os2(ap)4Cl2 (1). The molecular structure of 1 was determined from a single crystal X-ray diffraction study, which revealed an Os-Os bond length of 2.396[1] Å, and a cis-(2,2) arrangement of the ap ligands. Also reported are magnetic, electrochemical and spectroscopic properties of 1. 相似文献
15.
Mazhar Hamid Muhammad Mazhar Fiaz Ahmad Gabriele Kociok-Kohn 《Inorganica chimica acta》2008,361(1):188-194
The high nuclearity zinc complex, Zn6(OAc)8(μ-OH)2(dmae)2(dmaeH)2 (1) (OAc = acetate and dmaeH = N,N′-dimethylaminoethanol), having a low decomposition temperature and sufficiently high solubility in non-polar solvents, was synthesized by a simple chemical technique in high yield and analyzed by melting point, elemental analysis, FTIR, NMR, single crystal X-ray crystallography and thermal analysis. Aerosol-assisted chemical vapor deposition technique was used to deposit a high-quality thin film with good adhesion to the glass substrate at relatively low temperature (320 °C). Scanning electron microscopy of the film shows clearly distinct crystallites of uniform shape with 2.4-2.9 μm size. Powder X-ray diffraction measurements have indicated the deposition of a crystalline phase of hexagonal ZnO with space group P63mc. 相似文献
16.
Thomas G. H. Diekwisch Brett J. Berman Steven Gentner Harold C. Slavkin 《Cell and tissue research》1995,279(1):149-167
During epithelial-mesenchymal interactions associated with mammalian tooth development, epithelially-derived and mesenchymally-derived extracellular matrix molecules form a discrete dentine-enamel junction. The developmental and molecular processes required to form this junction are not known. To address this problem we designed studies to test the hypothesis that ectodermally-derived epithelial cells synthesize and secrete enamel proteins which function to nucleate and regulate the growth of enamel calcium phosphate crystals. Initial enamel crystals were detected separate from the adiacent dentine. Electron-microprobe analyses revealed that early enamel crystals were octacalciumphosphate or tricalciumphosphate rather than hydroxyapatite. Thereafter, enamel crystals became confluent with the adjacent, albeit significantly smaller hydroxyapatite crystals associated with mineralized dentine. Therefore, we interpret our data to indicate that de novo enamel crystal nucleation and growth are independent from the mineralization processes characterized for dentine. We further argue that gene expression of enamel protein appears to have a constitutive function during early enamel formation and that supramolecular aggregates of amelogenin and enamelin provide the microenvironment for the nucleation and crystal growth of the initial enamel matrix. 相似文献
17.
Padmini Ramaswamy 《Inorganica chimica acta》2011,372(1):136-144
Five new open-framework compounds of gallium have been synthesized by hydrothermal methods and their structures determined by single crystal X-ray diffraction studies. The compounds, [C8N4H26][Ga6F4(PO4)6], I, [C5N3H11][Ga3F2(PO4)3]·H2O, II, [C6N3H19][Ga4(C2O4)(PO4)4(H2PO4)]·2H2O, III, [Ga2F3(HPO4)(PO4)]·2H3O, IV, and [C3N2H5]2[Ga4(H2O)3(HPO3)7], V, possess three-dimensional structures. All the compounds are formed by the connectivity between the Ga polyhedra and phosphite/phosphate units. The observation of SBU-6 (I and II) and spiro-5 (IV) secondary building units (SBUs) are noteworthy. The flexibility of the formation of gallium phosphate frameworks has been established by the isolation of two related structures (I and II) from the same SBU units but different organic amines. Some of the present structures have close resemblance to the gallium phosphate phases known earlier. The compounds have been characterized by CHN analysis, powder XRD, IR, and TGA. 相似文献
18.
Jingyang Wang Yan Wang Dong‐Hwa Seo Tan Shi Shouping Chen Yaosen Tian Haegyeom Kim Gerbrand Ceder 《Liver Transplantation》2020,10(10)
Over the last decade, Na‐ion batteries have been extensively studied as low‐cost alternatives to Li‐ion batteries for large‐scale grid storage applications; however, the development of high‐energy positive electrodes remains a major challenge. Materials with a polyanionic framework, such as Na superionic conductor (NASICON)‐structured cathodes with formula NaxM2(PO4)3, have attracted considerable attention because of their stable 3D crystal structure and high operating potential. Herein, a novel NASICON‐type compound, Na4MnCr(PO4)3, is reported as a promising cathode material for Na‐ion batteries that deliver a high specific capacity of 130 mAh g?1 during discharge utilizing high‐voltage Mn2+/3+ (3.5 V), Mn3+/4+ (4.0 V), and Cr3+/4+ (4.35 V) transition metal redox. In addition, Na4MnCr(PO4)3 exhibits a high rate capability (97 mAh g?1 at 5 C) and excellent all‐temperature performance. In situ X‐ray diffraction and synchrotron X‐ray diffraction analyses reveal reversible structural evolution for both charge and discharge. 相似文献
19.
The permanent tooth plates of the Australian lungfish, Neoceratodus forsteri, are covered by enamel that develops initially in a similar manner to that of other vertebrates. As the enamel layer matures, it acquires several unusual characteristics. It has radially oriented protoprismatic structures with the long axes of the protoprisms perpendicular to the enamel surface. Protoprisms can be defined as aggregations of hydroxyapatite crystals that lack the highly ordered arrangement of the rods of mammalian enamel but are not without a specific structure of their own. The protoprisms are arranged in layers of variable thickness that are deposited sequentially as the tooth plate grows. They may be confined to the separate layers, or may cross the boundary between each layer. Crystals within the protoprisms are long and thin with hydroxyapatite c-axis dimensions of between 30 and 350 nm, and with typical a-b axis dimensions of 5-10 nm. The hydroxyapatite crystals of lungfish enamel have no centre dark lines of octacalcium phosphate, an unusual character among vertebrates. As each crystal develops, arrays of atoms may change direction, and regions exist where dislocations and extra lattice planes are inserted into the long crystal. The resulting hydroxyapatite crystal is not straight, and has a rough surface. The crystals are arranged in tangled structures with their crystallographic c-axes closely aligned with the long axis of the protoprism. Lungfish enamel differs from the enamel of higher vertebrates in that the hydroxyapatite crystals are of different shape, and, in mature enamel, the protoprisms remain as protoprisms and do not develop into the conventional prismatic structures characteristic of mammalian enamel. 相似文献
20.
Justyna Rewak-Soroczynska Nicole Nowak Sara Targonska Agata Piecuch Rafal J. Wiglusz 《Current issues in molecular biology》2022,44(12):6229
Nanosized silicate-substituted hydroxyapatites, characterized by the general formula Ca9.8−x−nSrnZnx(PO4)6−y(SiO4)y(OH)2 (where: n = 0.2 [mol%]; x = 0.5–3.5 [mol%]; y = 4–5 [mol%]), co-doped with Zn2+ and Sr2+ ions, were synthesized with the help of a microwave-assisted hydrothermal technique. The structural properties were determined using XRD (X-ray powder diffraction) and Fourier-transformed infrared spectroscopy (FT-IR). The morphology, size and shape of biomaterials were detected using scanning electron microscopy techniques (SEM). The reference strains of Klebsiella pneumoniae, Escherichia coli and Pseudomonas aeruginosa were used to assess bacterial survivability and the impact on biofilm formation in the presence of nanosilicate-substituted strontium-hydroxyapatites. Safety evaluation was also performed using the standard cytotoxicity test (MTT) and hemolysis assay. Moreover, the mutagenic potential of the materials was assessed (Ames test). The obtained results suggest the dose-dependent antibacterial activity of nanomaterials, especially observed for samples doped with 3.5 mol% Zn2+ ions. Moreover, the modification with five SiO4 groups enhanced the antibacterial effect; however, a rise in the toxicity was observed as well. No harmful activity was detected in the hemolysis assay as well as in the mutagenic assay (Ames test). 相似文献