Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.2.42 (DTA)
 1,693 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this study the following commercial products were thermo-analysed (TG, DTG, DTA): reabsorbable Dac Blu, non reabsorbable Dac Blu, non reabsorbable atomized Dac Blu, non reabsorbable thin Dac Blu, reabsorbable Biocoral 450, non reabsorbable thin Dac Blu, reabsorbable Biocoral 450, Calcitite 2040-12, Orthogel, Apagen, BTF 65, Calcitite 4060-2, Osprogel, Bio-Oss, Biostite, Osprovit, Merck Hydroxiapatite. The apparatus utilized was a Setaram TAG 24, in a symmetrical set up, which gave the TG, DTG and DTA analysis simultaneously. The analysis of all the materials were performed in correct operative conditions. The thermo analyses gave useful information about the thermal stability of the samples. The TG analysis gave the data relative to the percentage of weight loss due to the volatile substances in the samples (H2Oass C, OH-, CO2). The DTG graph made it possible to establish the presence of carbonate apatite and/or hydroxyapatite or the absence of both the substances. Finally, DTA and DTG analyses allowed show the presence of various organic substances. These data were very useful to characterize the examined materials and confirmed the extreme importance and sensibility of this method.
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PMID:[The thermal analysis of mineral-based biomaterials used in dentistry. 5]. 778 11

The infrared and Raman spectra of the title compound were recorded and are briefly discussed on the basis of its structural characteristics. Its thermal behaviour was investigated by means of TG and DTA measurements. Several dissolution tests were also performed. The results support the potential usefulness of this double carbonate as a useful compound for Zn(II) supplementation.
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PMID:Na2Zn3(CO3)4.3H2O: a potentially useful compound for zinc supplementation. 1036 77

This study of the thermal decomposition kinetics of various average diameter nano-particles of calcium carbonate by means of TG-DTA ( thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters; their pseudo-active energy (a); and that the top-temperature of decomposition T(p) decreases gently in the scope of micron-sized diameter, but decreases sharply when the average diameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reactions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both E(a) and T(p) to decline sharply with the decrease of the average diameter of nano-particles.
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PMID:Study on the thermal decomposition kinetics of nano-sized calcium carbonate. 1276 94

Many organisms from a wide variety of taxa produce amorphous calcium carbonate (ACC), despite the fact that it is inherently unstable and relatively soluble in its pure state. These properties also make it difficult to detect and characterize ACC. Raman spectroscopy is a particularly useful method for investigating ACC because the sample can be examined wet, and extended X-ray absorption fine structure (EXAFS) analysis can provide detailed information on the short-range order. Other methods for characterizing ACC include infrared spectroscopy, thermogravimetric analysis and differential thermal analysis (TGA and DTA), transmission electron microscopy (TEM), and electron and X-ray diffraction. Because of the difficulties involved, we suspect that ACC is far more widely distributed than is presently known, and a comparison of EXAFS spectra shows that different biogenic ACC phases have different short-range order structures. We also suspect that ACC fulfils many different functions, including as a transient precursor phase during the formation of crystalline calcium carbonate.
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PMID:Biologically formed amorphous calcium carbonate. 1295

Hydrotalcite-like compounds (HTlcs) containing Mg(2+), Al(3+), and Ce(3+) in the hydroxide layer and with carbonate as charge-balancing anion have been prepared by a co-precipitation (at constant pH) method. The Al/Ce ratio in the final product depends on the concentration in the initial solution. The crystallinity of the layered materials decreases with the increase in cerium content, probably, due to the distortions introduced by the large difference in the ionic radii of the cations. All the synthesized materials were characterized by XRD, FT-IR spectroscopy and TG/DTA. The textural properties were determined from low-temperature nitrogen adsorption-desorption measurements.
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PMID:Preparation and characterization of Mg-Al hydrotalcite-like compounds containing cerium. 1678 Aug 59

The hydration of tricalcium silicate (C(3)S) in the presence of heavy metal is very important to cement-based solidification/stabilisation (s/s) of waste. In this work, tricalcium silicate pastes and aqueous suspensions doped with nitrate salts of Zn(2+), Pb(2+), Cu(2+) and Cr(3+) were examined at different ages by X-ray powder diffraction (XRD), thermal analysis (DTA/TG) and (29)Si solid-state magic angle spinning/nuclear magnetic resonance (MAS/NMR). It was found that heavy metal doping accelerated C(3)S hydration, even though Zn(2+) doping exhibited a severe retardation effect at an early period of time of C(3)S hydration. Heavy metals retarded the precipitation of portlandite due to the reduction of pH resulted from the hydrolysis of heavy metal ions during C(3)S hydration. The contents of portlandite in the control, Cr(3+)-doped, Cu(2+)-doped, Pb(2+)-doped and Zn(2+)-doped C(3)S pastes aged 28 days were 16.7, 5.5, 5.5, 5.5, and <0.7%, respectively. Heavy metals co-precipitated with calcium as double hydroxides such as (Ca(2)Cr(OH)(7).3H(2)O, Ca(2)(OH)(4)4Cu(OH)(2).2H(2)O and CaZn(2)(OH)(6).2H(2)O). These compounds were identified as crystalline phases in heavy metal doping C(3)S suspensions and amorphous phases in heavy metal doping C(3)S pastes. (29)Si NMR data confirmed that heavy metals promoted the polymerisation of C-S-H gel in 1-year-old of C(3)S pastes. The average numbers of Si in C-S-H gel for the Zn(2+)-doped, Cu(2+)-doped, Cr(3+)-doped, control, and Pb(2+)-doped C(3)S pastes were 5.86, 5.11, 3.66, 3.62, and 3.52. And the corresponding Ca/Si ratios were 1.36, 1.41, 1.56, 1.57 and 1.56, respectively. This study also revealed that the presence of heavy metal facilitated the formation of calcium carbonate during C(3)S hydration process in the presence of carbon dioxide.
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PMID:Characterisation of products of tricalcium silicate hydration in the presence of heavy metals. 1741 62

Zinc titanate powders were prepared from Ti(SO4)2, Zn(NO3)2 x (6)H2O and (NH4)2CO3 by the method of direct precipitation. The effects of reaction conditions on the structure of zinc titanate were studied. The sample was analyzed by means of XRD and TG-DTA. The structure of zinc titanate was affected by the reaction subsequence of the formation of titanic acid and zinc carbonate. In the reaction system where titanic acid was generated earlier, collision reaction occurred between the generated zinc carbonate molecule and the surrounding titanic acid molecule. When titanic acid was generated earlier and precipitant (NH4)2CO3 was sufficient, Zn2Ti3O8 was obtained because of the sufficient collision reaction and superfluous titanic acid. In the reaction system where zinc carbonate was generated earlier, collision reaction occurred between the generated titanic acid molecule and the surrounding zinc carbonate molecule. When zinc carbonate was generated earlier and precipitant (NH4)2CO3 was sufficient, Zn2TiO4 was obtained because of the sufficient collision reaction and superfluous zinc carbonate. In addition, the kinds and structure of the production were affected by the dosage of precipitant and the reaction temperature. Zn2Ti3O8 or Zn2TiO4 could be obtained easier when using more precipitant or higher reaction temperature which could cause more sufficient collision reaction. ZnTiO3 could be obtained under the conditions of less precipitant and lower reaction temperature.
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PMID:[Study on X-ray powder diffraction of various structured zinc titanate prepared by the method of direct precipitation]. 1765 30

The mechanism for the decomposition of hydrotalcite remains unsolved. Controlled rate thermal analysis enables this decomposition pathway to be explored. Hydrotalcites containing carbonate, vanadate and molybdate were prepared by coprecipitation. The resulting materials were characterised by XRD, simultaneous TG-DTG-DTA and controlled rate thermal analysis (CRTA) to determine the stability and thermal decomposition pathway of the synthesised hydrotalcites. For the carbonate intercalated hydrotalcite dehydration takes place in three steps two of which are quasi-isothermal and one non-isothermal. Dehydroxylation and decarbonation occur separately over the 235-330 and 330-370 degrees C temperature range. A second non-isothermal decarbonation step is observed in the 371-541 degrees C range. In comparison the mixed carbonate-vanadate and carbonate-molybdate hydrotalcites show two dehydration steps and the dehydroxylation and decarbonation occur simultaneously. The observation of three dehydration steps is used to support the model of water molecules in three structurally distinct environments in the hydrotalcite interlayer. CRTA technology provides a mechanism for the decomposition of hydrotalcites.
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PMID:Mechanism for hydrotalcite decomposition: a controlled rate thermal analysis study. 1799 79

Lattice and surface impurity reactions and structural changes induced by them in slightly carbonated hydroxyapatite (SCHA) treated at 25-1100 degrees C were comprehensively studied. The SCHA was processed by a conventional wet synthesis at a high possible temperature(96 degrees C) using ammonium containing parent reagents. IR-spectroscopy, XRD, TG-DTA technique and mass spectrometric thermal analysis (MSTA) were employed for characterization of the samples. NH4+ with H3O+ in cationic-and CO3(2-) (A- and B-positions) with HPO4(2-) in anionic sites, and H2O, CO3(2-)(HCO3(-)) NO3(-), NxHy on the surface of particles were found and considered as impurity groups. Complicated changes in lattice constants of theSCHA stepwise annealed in air (for 2 h) were revealed; the changes were associated with reactions of the impurity groups. Filling the hexed sites with hydroxyl ions above 500 degrees C was shown to happen partly due to lattice reactions but was mainly owing to hydrolysis of the SCHA by water molecules in air. Decomposition of CO3(2-) groups proceeded through both thermal destruction and reactions with some of the impurity ions. The decarbonation in A-sites occurred at much lower temperatures (450-600 degrees C) than in B-sites (700-950 degrees C) and was first revealed to happen in two stages: due to an impurity reaction around 500 degrees C, and then through thermal destruction at 570 degrees C. A redistribution of CO3(2-) ions, decreasing in amount on the whole, was observed upon annealing above 500 degrees C. To avoid possible erroneous conclusions from TG-data, a sensitive method was shown to be required for monitoring gaseous decomposition products (such as the MSTA in this study), in case several impurity groups were present in a SCHA.
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PMID:Thermal impurity reactions and structural changes in slightly carbonated hydroxyapatite. 1927 49

ZnFe- and MgFe-LDHs were prepared by the anion exchange method, with the aim of adsorption of the ascorbic acid from the aqueous solutions by ion exchange process between anionic derivatives in LDH (Cl) and the anionic vitamin. This leads to successful intercalation of the vitamin into gallery space of LDH that offers a new route to safe preservation of bioactivity as well as controlled release. The prepared LDHs were characterized by XRD, TG-DTA and FT-IR spectroscopy. Adsorption of the ascorbic acid by the LDH under investigation was studied in terms of pH value, amount of LDH, contact time, VC (ascorbate) concentration and chemical composition of the host materials. The results indicate the relatively fast adsorption of the anionic vitamin by ZnFe-LDH-Cl and MgFe-Cl-LDH; reaches the equilibrium in 60 min. The shapes of the adsorption isotherms suggest specific interaction and high affinity. The batch kinetics of ascorbic acid adsorption onto ZnFe-Cl and MgFe-Cl-LDHs were studied. Furthermore, their release behaviors are also examined by spontaneous deintercalation with carbonate anion.
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PMID:Inorganic layered double hydroxides as ascorbic acid (vitamin C) delivery system--intercalation and their controlled release properties. 1950 14


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