The effect of Eu3+ concentration on the Y2O3 host lattice obtained from citrate precursors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dynamics of meso and thermo citrate synthases with implicit solvation

The dynamics of hydration of meso and thermo citrate synthases has been investigated using the EEF1 methodology implemented with the CHARNM program. The native enzymes are composed of two identical subunits, each divided into a small and large domain. The dynamics behavior of both enzymes at 30 degrees C and 60 degrees C has been compared. The results of simulations show that during the hydration process, each subunit follows a different pathway of hydration, in spite of the identical sequence. The hydrated structures were compared with the crystalline structure, and the root mean square deviation (RMSD) of each residue along the trajectory was calculated. The regions with larger and smaller mobility were identified. In particular, helices belonging to the small domain are more mobile than those of the large domain. In contrast, the residues that constitute the active site show a much lower displacement compared with the crystalline structure. Hydration free energy calculations point out that Thermoplasma acidophilum citrate synthase (TCS) is more stable than chicken citrate synthase (CCS), at high temperatures. Such result has been ascribed to the higher number of superficial charges in the thermophilic homologue, which stabilizes the enzyme, while the mesophilic homologue denatures. These results are in accord with the experimental found that TCS keeps activity at temperatures farther apart from the catalysis regular temperature than the CCS. (c) 2005 Wiley Periodicals, Inc.

Anticaries effect of dentifrices with calcium citrate and sodium trimetaphosphate

Because of the growing concerns regarding fluoride ingestion by young children and dental fluorosis, it is necessary to develop new dentifrices. Objective: The aim of this study was to evaluate the effect of dentifrices with calcium citrate (Cacit) and sodium trimetaphosphate (TMP) on enamel demineralization. Material and Methods: Enamel blocks (n=70), previously selected through surface hardness analysis, were submitted to daily treatment with dentifrices diluted in artificial saliva and to a pH-cycling model. The fluoride concentration in dentifrices was 0, 250, 450, 550, 1,000 and 1,100 mu g F/g. Crest (TM) was used as a positive control (1,100 mu g F/g). Cacit (0.25%) and TMP (0.25%) were added to dentifrices with 450 and 1,000 mu g F/g. Surface hardness was measured again and integrated loss of subsurface hardness and fluoride concentration in enamel were calculated. Parametric and correlation tests were used to determine difference (p<0.05) and dose-response relationship between treatments. Results: The addition of Cacit and TMP did not provide a higher fluoride concentration in enamel, however it reduced (p<0.05) mineral loss when compared to other dentifrices; the dentifrice with Cacit and TMP and a low fluoride concentration presented similar results when compared to a dentifrice with 1,100 mu g F/g (p>0.05). Conclusions: Dentifrices with 450 and 1,000 mu g F/g, Cacit and TMP were as effective as a gold standard one.

Effects of neonatal clomiphene citrate on fertility and sexual behavior in male rats

In order to investigate the participation of estrogen during the period of brain sexual differentiation, male rats were treated with clomiphene citrate in the neonatal phase. Fertility and sexual behavior were assessed during adult life. Sexual maturation, body weight, and wet weight of the testes were unchanged. Although the adult male rats treated with clomiphene in the neonatal phase presented a significant reduction in the frequency of mounts, 90% of these rats were able to mate with normal females, which became pregnant. However, these females exhibited a significantly increased number of pre- and post-implantation losses. When these adult male rats were castrated and received estrogen, 60% presented female sexual behavior (receptive behavior and acceptance of mount). Thus, treatment of pups with clomiphene immediately after birth has a long-term effect on the reproductive physiology and sexual behavior of male rats. (C) 2002 Elsevier B.V. All rights reserved.

Structural and magnetic characterization of MnxZn1-xFe2O4 (x=0.2; 0.35; 0.65; 0.8; 1.0) ferrites obtained by the citrate precursor method

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of citrate ions on the electrochemical behaviour of low-carbon steel in borate buffer solutions

The electrochemical behaviour of cold-rolled low carbon steel was studied on both active and passive potential regions in borate buffer solutions with and without the addition of sodium citrate (NaCit). In the active region anodic charges increased significantly and RCT values decreased with citrate, due to the formation of soluble complexes. In the passive potential region the film formed at +0.4 V in borate buffer solution with and without 0.010 M NaCit is probably enriched by Fe3O4 oxide, while films formed at +0.8 V are probably enriched by gamma-Fe2O3. The equivalent circuit [R-s(R(CT)Q)] fitted all experimental impedance data. (C) 2003 Elsevier Ltd. All rights reserved.

Diclofenac Abatement using Modified Solar Photo-Fenton Process with Ammonium Iron(III) Citrate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Y2O3:Eu3+ (5 mol%) with Ag nanoparticles prepared by citrate precursor

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evidence of hetero-epitaxial growth of Pb(Mg1/3Nb2/3)O-3 on the BaTiO3 seed particles of a citrate solution

Citrate solution was employed in preparing Pb(Mg1/3Nb1/3)O-3 (PMN) powder from polymeric precursors. BaTiO3 particles of 600 nm average size were used as seed for growing PMN. X-ray diffraction (XRD) indicated the presence of both, pyrochlore Pb6Nb6MgO22 (P6N) and perovskite phases. Transmission electron microscopy (TEM) observations indicated that only the PMN phase has hetero-epitaxially grown on the BaTiO3 seed particles. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Physicochemical properties of sildenafil citrate (Viagra) and sildenafil base

Sildenafil citrate (Viagra) [I] and sildenafil base [II] are easily and unequivocally characterized by a set of physicochemical methods that include X-ray diffractometry, infrared spectroscopy, and thermal analysis. Monoclinic lattice constants: [I]: a = 26.98 Angstrom; b = 11.95 Angstrom; c = 16.68 Angstrom; beta = 106.97degrees. [II]: a = 8.66 Angstrom; b = 34.27 Angstrom; c = 8.93 Angstrom; beta = 96.63'. Both compounds decompose at 189.4degreesC [I] and 251.9degreesC [II]. Densities and refractive indices are given. (C) 2003 Wiley-Liss, Inc.

Degradation of the herbicide tebuthiuron using solar photo-Fenton process and ferric citrate complex at circumneutral pH

The influence of pH on the degradation of the herbicide tebuthiuron (TBH) was investigated using in situ generated Fe(III)-citrate complexes (Fe:cit) submitted to the photo-Fenton process under solar irradiation. Using Fe:cit in a wide pH range (2.5-7.5), 100-78% TBH oxidation was achieved respectively from a UV dose of 2.0 J cm(-2) (15 min). Moreover, the oxidation of TBH obtained in the presence of Fe:cit at pH 6.0 was higher than that obtained using Fe(NO3)3 at pH 2.5. A similar behavior is observed for the removal of total organic carbon (TOC) in TBH solutions. In the presence of Fe:cit, 20% and 85% of TOC was removed at pH 7.5 and 2.5, respectively, after 7.5 J cm-2 irradiation, while no mineralization was observed employing Fe(NO3)(3) for the same UV dose. Using Fe(NO3)(3), mineralization was observed only after 11 J cm-2 (8%). A higher mineralization rate was obtained with Fe(NO3)(3) only when a concentration three times higher was employed at pH 2.5. Besides the high efficiency of TBH degradation observed using the ferric citrate complex in the solar photo-Fenton process, it also offers the advantage of application at a pH of up to 7.5. (c) 2007 Elsevier B.V. All rights reserved.

Protective effect of safranine on the mitochondrial damage induced by Fe(II)citrate: Comparative study with trifluoperazine

In this study, we show that safranine at the concentrations usually employed as a probe of mitochondrial membrane potential significantly protects against the oxidative damage of mitochondria induced by Fe(II)citrate. The effect of safranine was illustrated by experiments showing that this dye strongly inhibits both production of thiobarbituric acid-reactive substances and membrane potential decrease when energized mitochondria were exposed to Fe(II)citrate in the presence of Ca 2+ ions. Similar results were obtained with the lipophylic compound trifluoperazine. It is proposed that, like trifluoperazine, safranine decreases the rate of lipid peroxidation due to its insertion in the membrane altering the physical state of the lipid phase.

Structure and properties of donor doped barium titanate prepared by citrate process

Niobium doped barium titanate was prepared using two procedures. First, doped barium titanate was prepared starting from citrate solutions of all components and second, pure barium titanate powder was obtained from the citrate solutions and after that doped. Besides niobium, a small amount of manganese, as acceptor dopant was added. Phase composition, crystal structure, microstructure and dielectric properties were reported. The influence of powder processing on the properties of niobium doped barium titanate was analysed. The grain growth and the concentration of dopants on the dielectric properties were considered. © 2002 Taylor & Francis.

Effect of Nb on barium titanate prepared from citrate solutions

The influence of the addition of dopants on the microstructure development and electrical properties of BaTiO3 doped with 0.2, 0.4, 0.6, 0.8 mol% of Nb and 0.01 mol% of Mn based compounds was studied. Doped barium titanate was prepared using the polymeric precursor method from citrate solutions. The powders calcined at 700°C for 4 hours were analysed by infrared (IR) spectroscopy to verify the presence of carbonates, and by X-ray diffraction (XRD) for phase formation. The phase composition, microstructure and dielectric properties show a strong dependence on the amount of added niobium.

Therapeutic response of benzodiazepine, orphenadrine citrate and occlusal splint association in TMD pain

Loss of function, muscle inflammation, and pain are some of the signs and symptoms of temporomandibular dysfunction (TMD). Pharmacological strategies to minimize the clinical manifestation of these disorders often focus on blocking or inhibiting the pain-causing symptom. Resources such as muscle-relaxants, anxiety-relief drugs, and splint therapy are often used to reduce muscular hyperactivity related to TMD muscle pain. This study compares the effect of a randomly ordered association of occlusal splint therapy (S), nonsteroid anti-inflammatory with a muscle-relaxant drug (orphenadrine citrate) (O), and an anxiety-relief drug (benzodiazepine) (B), to ease painful TMD muscle symptoms. Clinical and anamnestic analyses were recorded in accordance with the Helkimo TMD index and applied before and after treatments. Twenty-one group two Helkimo TMD adult female patients were treated, all of whom were subjected to the three random therapeutic associations proposed: SBO, BOS, and OSB. The same operator applied the three specific associations over a period of 21 days in the proposed sequence, seven days for each therapy. The results show that all the groups presented the best results in terms of relief from pain after the therapeutic association (28.5% showed a decrease and 47.6% showed an absence of symptoms). No significant difference was observed among association therapeutic protocols. Copyright © 2003 by CHROMA, Inc.