Structural and spectroscopic characterization of 2,2 `-methylenedi-8-quinolinol dihydrochloride dihydrate

The crystal structure of the title compound, a promising ligand for chelatoterapies in the treatment of Alzheimer`s disease, has been determined by single crystal X-ray diffractometry. The compound crystallized in the monoclinic space group C2/c with Z = 4. The dimeric 8-quinolinol molecule is sited on a crystallographic twofold axis passing through the CH(2) carbon atom that links the symmetry related molecular halves, giving rise to a two-bladed propeller-like conformation. The (1)H and (13)C NMR as well as the IFT-IR and Raman spectra of the compound were also recorded and are briefly discussed. Some comparisons with spectra of related species are made. (C) 2008 Elsevier B.V. All rights reserved.

Structural and spectroscopic characterization of poly(styrene sulfonate) films doped with neodymium ions

This work reports the structural and spectroscopy characterization of poly(styrene sulfonate) (PSS) films doped with neodymium (Nd) ions. Nd-PSS films were processed using the acid of poly(styrene sulfonate) - H-PSS and neodymium nitrate - Nd(NO(3))(3); the maximum incorporation of Nd ions in the polymeric matrix was equal 19.3%. The absorption in the UV-Vis-NIR spectral region presents typical electronic transitions of Nd 3, ions, with well resolved peaks. The infrared spectra present the transition bands of PSS with characteristic line shape broadening, and the presence of vibrational modes of N-O groups in the range of 1400-720 cm(-1), prove the permanence of Nd(NO(3))(x), with x = 1, 2 and/or 3. in the H-PSS matrix. UV-Vis site selective photoluminescence data indicate that the incorporation of Nd 31 introduces a blue shift in PSS emission (325-800 nm), decreasing the interaction between adjacent PSS lateral groups (aromatic rings). Nd(3+) reabsorption and energy transfer effects between the PSS matrix and Nd(3+) were also observed. The IR emission of Nd-PSS films at 1076 rim ((4)F(3/2) -> (4)I(11/2)) present constant efficiency, independent on Nd(3+) concentration. The Judd-Ofelt theory was employed to analyze radiative properties. The excitation spectra prove the energy transfer between the polymeric matrix and Nd(3+). Complex impedance data was used to probe relaxation processes during the charge transport within the polymeric matrix. (C) 2008 Elsevier B.V. All rights reserved.

Thermo-optics parameters measurements in photorefractive sillenite Bi(12)SiO(20) crystals by thermal lens technique

The present work reports on the thermo-optical properties of photorefractive sillenite Bi(12)SiO(20) (BSO) crystals obtained by applying the Thermal Lens Spectrometry technique (TLS). This crystals presents one high photorefractive sensitivity in the region blue-green spectra, since the measurements were carried out at two pump beam wavelengths (514.5 nm and 750 nm) to study of the light-induced effects in this material (thermal and/or photorefractive). We determine thermo-optical parameters like thermal diffusivity (D), thermal conductivity (K) and temperature coefficient of the optical path length change (ds/dT) in sillenite crystals. These aspects, for what we know, not was studied in details up to now using the lens spectrometry technique and are very important against of the promising potentiality of applications these crystals in non linear optics, real time holography and optical processing data.

Energy transfer processes in Yb(3+)-Tm(3+) co-doped sodium alumino-phosphate glasses with improved 1.8 mu m emission

Sodium alumino-phosphate glasses co-doped with Yb(3+) and Tm(3+) ions have been prepared with notably low OH(-) content, and characterized from the viewpoint of their spectroscopic properties. In these glasses, Yb(3+) acts as an efficient sensitizer of excitation energy at 0.98 mu m - which can be provided by high power and low cost diode lasers, and subsequently undergoes non-resonant energy transfer to Tm(3+) ions ((2)F(5/2), (3)H(6) --> (2)F(7/2), (3)H(5)). Through this process, the emitting level (3)F(4) is rapidly populated, generating improved emission at 1.8 mu m ((3)F(4) --> (3)H(6)). In order to guarantee the efficiency of such favorable energy transfer, energy losses via multiphonon decay, Yb-Yb radiative trapping, and non- radiative transfer to OH(-) groups were evaluated, and minimized when possible. The dipole - dipole energy transfer microscopic parameters corresponding to Yb(3+) --> Tm(3+), Yb(3+) --> Yb(3+) and Tm(3+) --> Tm(3+) transfers, calculated by the Forster-Dexter model, are C(Yb-Tm) = 2.9 x 10(-40) cm(6) s(-1), C(Yb-Yb) = 42 x 10(-40) cm(6) s(-1) and C(Tm-Tm) = 43 x 10(-40) cm(6) s(-1), respectively.

Cyclocreatine, an anticancer and neuroprotective agent. Spectroscopic, structural and theoretical study

The structural, spectroscopic and theoretical study of cyclocreatine (1-carboxymethyl-2-iminoimidazolidine, CyCre) has been performed prompted by the biological relevance of the molecule and its potential role as a ligand in biometalic compounds. The crystal structure of CyCre has been determined by X-ray diffraction methods. The compound crystallizes as a zwitterion in the monoclinic system, space group P2(1)/c. The crystal is further stabilized by a network of N-H center dot center dot center dot O bonds. Infrared and Raman spectra of the solid, electronic spectra of aqueous solutions at different pH values and (1)H and (13)C NMR spectra have been recorded and analyzed. Band assignments were accomplished with the help of theoretical calculations. Optimized molecular geometries, harmonic vibrational frequencies and molecular electrostatic potentials were calculated using methods based on the density functional theory. (C) 2010 Elsevier B.V. All rights reserved.

Bayesian estimation of regression parameters in elliptical measurement error models

The main object of this paper is to discuss the Bayes estimation of the regression coefficients in the elliptically distributed simple regression model with measurement errors. The posterior distribution for the line parameters is obtained in a closed form, considering the following: the ratio of the error variances is known, informative prior distribution for the error variance, and non-informative prior distributions for the regression coefficients and for the incidental parameters. We proved that the posterior distribution of the regression coefficients has at most two real modes. Situations with a single mode are more likely than those with two modes, especially in large samples. The precision of the modal estimators is studied by deriving the Hessian matrix, which although complicated can be computed numerically. The posterior mean is estimated by using the Gibbs sampling algorithm and approximations by normal distributions. The results are applied to a real data set and connections with results in the literature are reported. (C) 2011 Elsevier B.V. All rights reserved.

Cardiovascular Disease Parameters in Periodontitis

Background: Recently, there has been an increasing in the impact of oral health on atherosclerosis and subsequent cardiovascular disease. The aim of this study is to investigate the association between chronic periodontitis and cardiovascular risk markers. Methods: Forty patients with periodontitis and 40 healthy gender-, body mass index-, and age-matched individuals were compared by measuring total cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides, levels of cytokines, antibodies against oxidized low-density lipoprotein, thiobarbituric acid reactive substances, total and differential white blood cell counts, and the non-linear index of refraction. Results: The levels of triglycerides and high-density lipoprotein in periodontitis patients were significantly higher and lower, respectively (P=0.002 and P=0.0126), compared to controls. Total cholesterol, low-density lipoprotein, and lipid peroxide levels were the same in both groups (P = 0.2943, P = 0.1284, and P = 0.067, respectively). Interleukin (IL)-6 and -8, antibodies against oxidized low-density lipoprotein, and leukocyte and neutrophil counts were significantly higher in periodontitis patients (P<0.05). The value of the non-linear index of refraction of low-density lipoprotein solutions was higher in the controls (P = 0.015) compared to individuals with periodontitis. Conclusion: Our results confirmed and further strengthened the suggested association between coronary artery disease and periodontitis. J Periodontol 2009;80:378-388.

The influence of ARIMA-GARCH parameters in feed forward neural networks prediction

The objective of this article is to find out the influence of the parameters of the ARIMA-GARCH models in the prediction of artificial neural networks (ANN) of the feed forward type, trained with the Levenberg-Marquardt algorithm, through Monte Carlo simulations. The paper presents a study of the relationship between ANN performance and ARIMA-GARCH model parameters, i.e. the fact that depending on the stationarity and other parameters of the time series, the ANN structure should be selected differently. Neural networks have been widely used to predict time series and their capacity for dealing with non-linearities is a normally outstanding advantage. However, the values of the parameters of the models of generalized autoregressive conditional heteroscedasticity have an influence on ANN prediction performance. The combination of the values of the GARCH parameters with the ARIMA autoregressive terms also implies in ANN performance variation. Combining the parameters of the ARIMA-GARCH models and changing the ANN`s topologies, we used the Theil inequality coefficient to measure the prediction of the feed forward ANN.

Sodium Tungstate on Some Biochemical Parameters of the Parotid Salivary Gland of Streptozotocin-Induced Diabetic Rats: A Short-Term Study

Several studies have shown the antidiabetic properties of sodium tungstate. In this study, we evaluated some biochemical parameters of the parotid salivary gland of streptozotocin-induced diabetic rats treated with sodium tungstate solution (2 mg/ml). The studied groups were: untreated control (UC), treated control (TC), untreated diabetic (UD), and treated diabetic (TD). After 2 and 6 weeks of treatment, parotid gland was removed and total protein and sialic acid (free and total) concentration and amylase and peroxidase activities were determined. Data were compared by variance analysis and Tukey test (p < 0.05). The sodium tungstate treatment modestly decreased the glycemia of streptozotocin-induced diabetic rats. At week 2 of the study, parotid gland of diabetic rats presented a reduction of total protein concentration (55%) and an increase of amylase (120%) and peroxidase (160%) activities, free (150%) and total (170%) sialic acid concentration. No alteration in the evaluated parameters at week 6 of the study was observed. Sodium tungstate presented no significant effect in parotid gland. Our results suggest that diabetes causes initial modification in biochemical composition of parotid. However, this gland showed a recovery capacity after 6 week of the experimental time. Sodium tungstate has no effect in peripheral tissues, such as salivary glands.

Does the neuromotor abnormality type affect the salivary parameters in individuals with cerebral palsy?

Background: Previous studies reported alterations in salivary flow rate and biochemical parameters of saliva in cerebral palsy (CP) individuals; however, none of these considered the type of neuromotor abnormality among CP individuals, thus it remains unclear whether the different anatomical and extended regions of the brain lesions responsible for the neurological damage in CP might include disruption of the regulatory mechanism of saliva secretion as part of the encephalopathy. The aim of this study was to evaluate salivary flow rate, pH and buffer capacity in saliva of individuals with CP, aged 3-16 years, with spastic neuromotor abnormality type and clinical patterns of involvement. Methods: Sixty-seven individuals with CP spasticity movement disorder, were divided in two groups according to age (3-8- and 9-16-years-old) and compared with 35 sibling volunteers with no neurological damage, divided in two groups according to age (3-8- and 9-16-years-old). Whole saliva was collected under slight suction and pH and buffer capacity were determined using a digital pHmeter. Buffer capacity was measured by titration using 0.01N HCL, and flow rate was calculated in ml/min. Results: In both age groups studied, whole saliva flow rate, pH and buffer capacity were significantly lower in the spastic CP group (P < 0.05). The clinical patterns of involvement did not influence the studied parameters. Conclusion: These findings show that individuals with spastic cerebral palsy present lower salivary flow rate, pH and buffer capacity that can increase the risk of oral disease in this population.

Spectroscopic and theoretical studies of some N-methoxy-N-methyl-2-[(4 `-substituted) phenylsulfonyl]propanamides

The analysis of the IR carbonyl band of the N-methoxy-N-methyl-2-[(4`-substituted)phenyisulfonyI]propanamides Y-PhSO(2)CH(Me)C(O)N(OMe)Me (Y = OMe 1, Me 2, H 3, Cl 4, NO(2) 5), supported by HF/6-31G(d,p) calculations of 3,, indicated the existence of two gauche conformers (g(1) and g(2)), the g, conformer being the most stable and the least polar one (in gas phase and in solution). Both conformers are present in solution of the non polar solvent (CCl(4)) for 1-5 and in solution of the more polar solvents (CHCl(3)) for 1. 4, 5 and (CH(2)Cl(2)) for 5, while only the g(1) conformer is present in solution of the most polar solvent (CH(3)CN) for 1-5. The g, and g2 conformers correspond to the enantiomeric pairs of diastereomers (diast(1) and diast(2)) whose relative configurations are [C(3)(R)N(R)]/[C(3)(s)N(s)] and [C(3)(R)N(s)]/[C(3)(s)N(R)], respectively. The computed carbonyl frequencies for g(1) (diast(1)) and g(2) (diast(2)) stereoisomers of3 match well the experimental values. The NBO analysis, for 3 shows the important role of the orbital interactions in conformer stabilization and the overall balance of these interactions corroborates that the g, conformer is more stable than the 92 one. The observed abnormal solvent effect on the relative intensities of the carbonyl doublet components is attributed to the molecular crowding in the g2 conformer which hinders its solvation in comparison to the g, conformer (diast(1)). X-ray single crystal analysis performed for 3 shows the existence Of two 92, and g(1b) conformers of diastereomers (diast2, and diast(1b)) whose absolute configurations are [C(3)(R)N(s)] and [C(3)(R)N(R)], respectively. The larger population and. thus, the larger stabilization of the g(2), conformer over the gib form in the crystals may be associated with a larger energy gain deriving from dipole moment coupling in the former conformer along with a series of C-H center dot center dot center dot O electrostatic and hydrogen bond interactions, (C) 2009 Elsevier B.V. All rights reserved.

Spectroscopic evidences of the presence of hydrogenated species on the surface of copper during CO(2) electroreduction at low cathodic potentials

Carbon dioxide electroreduction on copper electrode was studied by surface enhanced Raman scattering (SERS) in K(2)SO(4) aqueous solutions with different pH values. CO(2) was bubbled into the solution at 0 V vs. Ag/AgCl, i.e., on an oxidized copper surface. In acidic solutions (pH around 2.5), at -0.2 V, bands indicative of the presence of ethylene on the electrode surface were detected. Although ethylene is knowledgably a product of CO(2) electroreduction on copper, it was not experimentally identified on the electrode`s surface at such a low cathodic potential in prior works. In solutions with pH around 2.5, CO bands were not observed, suggesting that hydrocarbons could be formed by a pathway that does not occur via adsorbed CO. In solutions with higher pHs, a complex spectral pattern, between 800 and 1700 cm(-1), was observed at approximately -0.4 V. The observed spectrum closely resembles those reported in the literature for adsorption of monocarboxylic acids with small chains. The spectral features indicate the presence of a structure containing a double C=C bond. a carboxyl group, and C-H bonds on the electrode`s surface. SERS spectra obtained in CO-saturated solution are also presented. However, in this case, no SERS bands were observed in the region between 800 and 1700 cm(-1) at low cathodic potentials. (c) 2009 Elsevier B.V. All rights reserved.

Structural parameters of polyacrylamide hydrogels obtained by the Equilibrium Swelling Theory

In this paper, the synthesis and structural characterization of a series of polyacrylamide hydrogels with different degrees of reticulation are reported. Although the Equilibrium Swelling Theory was recognized as a simple and reliable tool for the determination of structural hydrogels network parameters like equilibrium degree of swelling, cross-link ratio and mesh size, this is the first application of this methodology for polyacrylamide hydrogels. By changing the total monomer content in the synthesis solution (%T) from 5 to 30%, at a fixed value of cross-linker content in the total monomer amount (%C) of 5%, the final parameter obtained, the mesh size, can be tuned from 2 to 0.3 nm. It was also possible to change the mesh size (0.19-0.35) by varying %C from 5 to 12% (at %T = 20%). Scanning Electron Microscopy images for the most different formulations are shown and corroborate data obtained from the theory. (c) 2008 Elsevier Ltd. All rights reserved.

Spectroscopic investigation of the interactions between emeraldine base polyaniline and Eu(III) ions

The interactions of emeraldine base form of polyaniline (EB-PANI) and Eu(III) ions in 1-methyl-2-pyrrolidinone (NMP) solution and in films have been investigated by UV-vis-NIR, resonance Raman. luminescence and electron paramagnetic resonance (EPR) spectroscopies. These spectroscopic techniques allowed to characterize quinone and semiquinone segments in the polymeric chains. and the oxidation state of europium ions in Eu-PANI samples. For high values of Eu(III)/N molar ratio (24/1) the presence of a weak polaronic absorption band at 980 nm in UV-vis-NIR spectrum and the observation of bands at 1330 and 1378 (nu(center dot)(C-N+)) cm(-1) due to emeraldine salt in the Raman spectrum at 1064 nm indicate a low doping degree. Oxidation of EB-PANI to pernigraniline base (PB-PANI) occurs in diluted solutions. The experimental data showed that the solvent plays an important role on the nature of formed species. The narrow EPR signal at g = 2.006 (line width 8G) confirms the presence of PANI radical cations in Eu-PANI film. The absence of broad signal characteristic of Eu(II) in EPR spectrum suggested that europium ions are primarily at Eu(III) oxidation state. The luminescence spectra of Eu-PANI film presented emission bands at 405 and 418 nm assigned to PANI moieties and bands at 594,615 and 701 nm assigned to (5)D(0) -> (7)F(J) (J = 1, 2 and 4, respectively) transitions of Eu(III). EPR and photoluminescence data confirm that europium ions are mainly in Eu(III) oxidation state in Eu(III)/PANI films. (C) 2008 Elsevier B.V. All rights reserved.

Spectroscopic and theoretical studies of some N-methoxy-N-methyl-2-[(4 `-substituted) phenylthio]propanamides

The analysis of the IR carbonyl band of the N-methoxy-N-methyl-2-[(4`-substituted)phenylthio]propanamides Y-PhSCH(Me)C(O)N(OMe)Me (Y=OMe 1, Me 2, H 3, Cl 4, NO(2) 5), supported by B3LYP/cc-pVDZ calculations of 3, indicated the existence of two gauche conformers (g(1) and g(2)), the g(1) conformer being the more stable and the less polar one (in gas phase and in solution). Both conformers are present in solution of the polar solvents (CH(2)Cl(2) and CH(3)CN) for 1-5 and in solution of the less polar solvent (CHCl(3)) for 1-4, while only the g(1) conformer is present in solution of non polar solvents (n-C(6)H(14) and CCl(4)) and in solution of CHCl(3) for 5. NBO analysis shows that both the sigma(C-S) -> pi*(C=O) (hyperconjugative) and the pi(C=O) -> sigma*(C-S) orbital interactions contribute almost to the same extent for the stabilization of g(1) and g(2) conformers. The pi*(C=O) -> sigma*(C-S), n(S) -> pi*(C=O) and the n(S) -> pi*(C=O) orbital interactions stabilize more the g(1) conformer than the g(2) one. Moreover, the suitable geometry of the g(1) conformer leads to its stabilization through the LP(O2) -> sigma*(C8-H11) orbital interaction (hydrogen bond) along with the strong O([CO])(delta-) center dot center dot center dot H([O-Ph])(delta+) electrostatic interaction. On the other hand, the appropriate geometry of the g(2) conformer leads to its stabilization by the LP(O22) -> sigma*(C9-H13) orbital interaction (hydrogen bond) along with the weak O([OMe])(delta-) center dot center dot center dot H([o`-Ph])(delta+) electrostatic static interaction. As for the 4`-nitro derivative 5 the ortho-phenyl hydrogen atom becomes more acidic, leading to a stronger O([CO])(delta-) center dot center dot center dot H([o-Ph])(delta+) interaction and, thus, into a larger stabilization of the g(1) conformer in the whole series. This trend is responsible for the unique IR carbonyl band in CHCl(3) solution of 5. The larger occupancy of the pi*(C=O) orbital of the g(1) conformer relative to that of the g(2) conformer, along with the O([CO])(delta-) center dot center dot center dot H([o-Ph])(delta+) electrostatic interaction (hydrogen bond) justifies the lower carbonyl frequency of the g(1) conformer with respect to the g(2) one, in gas phase and in solution. (C) 2008 Elsevier B.V. All rights reserved.