XANES, EXAFS, Voltammetric, and Microhardness Studies of Manganese Dioxide-Lead-Lead Dioxide Vitroceramics.

In this work we investigated the electrochemical performances and mechanical behavior of the manganese dioxide-lead dioxide-lead vitreous system. The structural and electrochemical properties of vitroceramics were investigated by the analysis of X-ray diffraction (XRD) spectra, X-ray absorption spectroscopy (XAS), and measurements of cyclic voltammetry and linear sweep voltammetry. The mechanical properties of the studied samples were determined by Vickers hardness values using the indentation method. The analysis of X-ray absorption near edge structure (XANES) data for the L3 edge of the lead and the radial distribution function data for the PbO2 and Pb model indicate the modification of Pb-O interatomic distances by the doping process. The voltammetric study reveals the vitroceramic with x = 90 mol% Pb as the most suitable for application as a lead acid battery electrode.

Advanced zirconia ceramics stabilized with yttria and magnesia: Structure and Vickers microhardness.

The samples 8YSZ containing 70, 75, 80 mol% ZrO2 and other oxides were prepared by. a high temperature solid state reaction process. Using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and spectroscopic methods were evaluated the effect of oxide addition on the properties of yttria-doped zirconia. X-ray data shows the formation of zirconia (Y-doped), YSZ and/or tetragonal zirconia crystalline phases in all samples. IR data indicate the stretching vibrations of the Si-O bonds from tetrahedral [SiO4] units and the stretching vibrations of the Fe-O bonds from [FeO6] structural units, respectively. EPR results indicate the destroying of the local ordering of the Fe+3 ion vicinities situated in the rhombic distorted octahedral geometries by the increasing of ZrO2 content in the host ceramic. The highest values of Vickers hardness were recorded for the ceramics containing 70 and 75 mol% ZrO2. This superior performance can be explained considering the presence of a smaller amount of monoclinic ZrO2 crystalline phase in the ceramic structure. The analysis of the X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) data shows the presence of Fe+2 and Fe+3 ions. In the ceramics with higher ZrO2 contents the iron atoms adopt a randomly structure due to the highly distorted [FeO6] structural units and non-equivalent Fe-O distances in the first coordination shell.

Stabilized zirconia ceramics for dental applications.

The research is aiming to obtain at room temperature a new ceramic material containing partially stabilized zirconia with different oxides after sintering used for dental and other technological purposes. Our research proposes a new method based on the use of stabilized zirconia with other oxides to obtain optimized dental material with a lower cost price and / or improved properties to allow wider use of these products to an increased number of patients in dental offices. X-ray diffraction, SEM analysis. FTIR spectroscopy, UVVis and density measurements were accomplished for the three ceramic systems. The correlation between the microstructure and the spectroscopic properties of zirconium stabilized by FTIR spectroscopy, UV-Vis helps understanding the mechanisms associated with the formation of high (tetragonal and / or cubic) temperature zirconia. Along with the simple, less costly preparation method and high purity of the ceramic products our study offers a highly desirable product for technological applications.

Characteristics and local structure of hafnia-silicate-zirconate ceramic nanomixtures.

Zirconate systems having the composition 3HfO2·15SiO2·xY2O3·(82 - x)ZrO2, where x = 2, 7 and 12 mol% Y2O3, were synthesized by a sol-gel method. The analysis of X-ray diffraction data showed the presence of the t-ZrO2, m-ZrO2, m-HfO2, Y2SiO5 and Y2Si2O7 crystalline phases in a ceramic nanomixture. Spectroscopic data show that the increase of the Y2O3 content of samples determines the increase of the t-ZrO2, m-HfO2 and silicate crystalline phases. Gap energy values decrease almost linearly with increasing Y2O3 content of samples. A detailed study of XANES data does not show a significant difference with increasing Y2O3 content of the samples suggesting an appreciable stability of the hafnium ions +4 oxidation state and their microvicinity. EXAFS results show that the local structure around the Hf cation is similar to that from the monoclinic crystalline HfO2 where the Hf-O coordination number tends to 7. The bond lengths of Hf-O shells show small deviations from ∼2.12 Šand the Hf-metal paths become more structured by increasing the Y2O3 content of the samples.

Secular trend of head and face shape in adult population of Vojvodina (Serbia).

BACKGROUND: Different populations show variation in the pattern of change in craniofacial dimensions over time. Earlier studies of craniofacial traits in the Republic of Serbia were carried out, without any particular reference to secular changes. AIM: The aim of the study is to determine possible changes in craniofacial dimensions among the adult population of Vojvodina (Serbia) during a 33 year period. SUBJECTS AND METHODS: The findings of the study are based on the comparison of data from two cross-sectional surveys. The earlier research was conducted in 1975 (n = 2600) and the second from 2001-2006 (n = 4504). Four craniofacial dimensions and body height were analysed. RESULTS: In terms of the head dimensions, head length in males has increased substantially, while head breadth has decreased in both sexes. The total change in the cephalic index is 0.58 (males) and 0.48 (females) units per decade. Morphological face height has substantially increased, while face breadth has decreased in both sexes over this period. The total change in the facial index per decade is 0.75 units in males and 0.98 in females. CONCLUSION: The results point to a trend of head and face shape remodelling toward a narrower head and more elongated face, consistent with ongoing dolichocephalisation.

The network modifier and former role of the bismuth ions in the bismuth-lead-germanate glasses.

The present work is focused on the enhancement of network former environment in lead-germanate glasses by bismuth ions doping. A series of bismuth-lead-germanate glasses with the xBi2O3·(100-x)[7GeO2·3PbO] composition glass where 0≤x≤30 mol% Bi2O3 were synthesized by melt-quenching method. The FTIR, UV-VIS spectroscopy and cyclic voltammetry were conducted on these samples to evaluate the doping effect of structure of the host matrix network. Our results indicate that direct incorporation of Bi2O3 into the lead-germanate network modifies the lead-germanate network and the internal structure of glass network is rearranged. The structural flexibility of the lead-germanate network is possible due to its incapacity to accommodate with the excess of oxygen atoms and the creation of bridging oxygen ions. Optical gap energy and refractive index were obtained as a function of Bi2O3 content. Gap energy values decrease as Bi2O3 content increased from 0 to 10 mol%. Further increase of Bi2O3 concentration beyond 10 mol% increased the gap energy values. These behaviors of the glass system can be explained by two mechanisms: (i) for x≤10 mol% Bi2O3--increase of degree of disorder of the host matrix because Bi2O3 is network modifier and (ii) for x>10 mol%--Bi2O3 acts as a network former. Cyclic voltammetry measurements using the glass system with 10Bi2O3·90[7GeO2·3PbO] composition as working electrode show the mobility of the lead ions, in agreement with UV-VIS data.

Validation of the chronic liver disease questionnaire in Serbian patients.

AIM: To translate into Serbian and to investigate the validity of the cross-culturally adapted the chronic liver disease questionnaire (CLDQ). METHODS: The questionnaire was validated in 103 consecutive CLD patients treated between October 2009 and October 2010 at the Clinic for Gastroenterology, Clinical Centre of Serbia, Belgrade (Serbia). Exclusion criteria were: age < 18 years, psychiatric disorders, acute complications of CLD (acute liver failure, variceal bleeding, and spontaneous bacterial peritonitis), hepatic encephalopathy (grade > 2) and liver transplantation. Evaluation of the CLDQ was done based on the following parameters: (1) acceptance is shown by the proportion of missing items; (2) internal reliabilities were assessed for multiple item scales by using Cronbach alpha coefficient; and (3) in order to assess whether the allocation of items in the domain corresponds to their distribution in the original questionnaire (construction validity), an exploratory factor analysis was conducted. Discriminatory validity was determined by comparing the corresponding CLDQ score/sub-score in patients with different severity of the diseases. RESULTS: The Serbian version of CLDQ questionnaire completed 98% patients. Proportion of missing items was 0.06%. The total time needed to fill the questionnaire was ranged from 8 to 15 min. Assistance in completing the questionnaire required 4.8% patients, while 2.9% needed help in reading, and 1.9% involved writing assistance. The mean age of the selected patients was 53.8 ± 12.9 years and 54.4% were men. Average CLDQ score was 4.62 ± 1.11. Cronbach's alpha for the whole scale was 0.93. Reliability for all domains was above 0.70, except for the domain "Activity" (0.49). The exploratory factor analysis model revealed 6 factors with eigenvalue of greater than 1, explaining 69.7% of cumulative variance. The majority of the items (66%) in the Serbian version of the CLDQ presented the highest loading weight in the domain assigned by the CLDQ developers: "Fatigue" (5/5), "Emotional function" (6/8), "Worry" (5/5), "Abdominal symptoms" (0/3), "Activity" (0/3), "Systemic symptoms" (3/5). The scales "Fatigue" and "Worry" fully corresponded to the original. The factor analysis also revealed that the factors "Activity" and "Abdominal symptoms" could not be replicated, and two new domains "Sleep" and "Nutrition" were established. Analysis of the CLDQ score/sub-score distribution according to disease severity demonstrated that patients without cirrhosis had lower total CLDQ score (4.86 ± 1.05) than those with cirrhosis Child's C (4.31 ± 0.97). Statistically significant difference was detected for the domains "Abdominal symptoms" [F (3) = 5.818, P = 0.001] and "Fatigue" [F (3) = 3.39, P = 0.021]. Post hoc analysis revealed that patients with liver cirrhosis Child's C had significantly lower sub-score "Abdominal symptoms" than patients without cirrhosis or liver cirrhosis Child's A or B. For domain "Fatigue", patients with cirrhosis Child's C had significantly lower score, than non-cirrhotic patients. CONCLUSION: The Serbian version of CLDQ is well accepted and represents a valid and reliable instrument in Serbian sample of CLD patients.

Effect of aluminum oxide codoping on copper-lead-germanate glasses.

Glasses from xCuO⋅(100-x)[7GeO(2)⋅3PbO(2)⋅0.05Al(2)O(3)] system where x=0, 1, 5, 10, 20 and 30 mol% CuO were studied by FT-IR, UV-VIS and ESR spectroscopy in order to obtain information about the structural correlations and the relationship between structure and optical properties in these materials. The analyses of these IR spectra reveal that the accommodation of the network with the excess of oxygen ions is possible by the depolymerization of the germanate network in shorter chains, especially ortho- and/or pyrogermanate structural units. UV-VIS absorption spectrum of the sample with x=1% CuO begins with a rising absorption band situated at about 250 nm. This band can be assigned to the GeOGe wrong bonds such as the Ge(+2) centers. Optical study is performed to calculate the refractive index and optical band gap using UV-VIS spectra in the wavelength range 250-1,000 nm. The increase in optical band is explained on the basis of the average bond energy of the system and the number of non-bridging oxygen ions. ESR spectra of CuO substituted samples are characterized by broad peaks probably because of the formation of Cu(+2)-Ge(+2) exchange pairs which are weakly coupled though the oxygen atom.

Structural study of ternary iron-lead-germanate glass ceramics.

Glass ceramics with the composition xFe(2)O(3)·(100-x)[7GeO(2)·3PbO(2)] where 0≤x≤60 mol% were obtained and studied using XRD, FTIR and UV-vis spectroscopy investigations. Heat treatment of glass samples at 400°C for 8 h led to the formation of α, γ-PbGe(4)O(9), Pb(3)Fe(2)Ge(4)O(14) and PbO(1.44) crystalline phases. The content of these crystalline phases depends of Fe(2)O(3) concentration. FTIR spectroscopy data suggest that the lead ions have a pronounced affinity towards [GeO(5)] structural units containing non-bridging oxygens and [FeO(4)] anions producing formation of the Pb(3)Fe(2)Ge(4)O(14) crystalline phase. The introduction of low concentrations of Fe(2)O(3) into the host matrix results in the formation of new absorption UV bands between 320 and 450 nm. These bands arise from to the d-d transitions of the Fe(+3) ions. The light absorption in the range from 250 to 600 nm increases with increasing iron oxide content in matrix network, accompanied with the changes on color from white to brown yellow and darker brown.

Dinuclear manganese centers in the manganese-lead-tellurate glasses.

FTIR, UV-VIS and EPR spectra of manganese doped lead-tellurate glasses with composition xMnO·(100-x)[4TeO2·PbO2] where x=0, 1, 5, 10, 20, 30, 40mol% have been studied. The FTIR spectra show the formation of the Mn-O-Pb and Mn-O-Te bridging bonds by increasing of MnO concentration. The UV-VIS spectra show the Mn(+3) species exhibit pronounced absorption, which masks the Mn(+2) spin-forbidden absorption bands when Mn(+2) ions are in high concentrations in these glasses. The EPR spectra exhibit resonance signals characteristic of Mn(+2) ions. The resonance signal located at g≈2 is due to Mn(+2) ions in an environment close to octahedral symmetry, whereas the resonance at g≈4.3 and 3.3 are attributed to the rhombic surroundings of the Mn(+2) ions. The increase in the MnO content gives rise to absorption at g≈2.4 and the paramagnetic ions are involved in dinuclear manganese centers.

Role of serotonin in development of esophageal and gastric fundal varices.

AIM: to determine the effect of free serotonin concentrations in plasma on development of esophageal and gastric fundal varices. METHODS: this prospective study included 33 patients with liver cirrhosis and 24 healthy controls. Ultrasonography and measurement of serotonin concentration in plasma were carried out in both groups of subjects. The upper fiber panendoscopy was performed only in patients with liver cirrhosis. RESULTS: the mean plasma free serotonin levels were much higher in liver cirrhosis patients than in healthy controls (219.0 ± 24.2 nmol/L vs 65.4 ± 18.7 nmol/L, P < 0.0001). There was no significant correlation between serotonin concentration in plasma and the size of the esophageal varices according to Spearman coefficient of correlation (r(s) = -0.217, P > 0.05). However, the correlation of plasma serotonin concentration and gastric fundal varices was highly significant (r(s) = -0.601, P < 0.01). CONCLUSION: free serotonin is significant in pathogenesis of portal hypertension especially in development of fundal varices, indicating the clinical value of serotonergic receptor blockers in these patients.

Structural properties of molybdenum-lead-borate glasses.

Glasses and glass ceramics in the system xMoO3·(100 - x)[3B2O3·PbO] with 0 ≤ x ≤ 30 mol% have been prepared from melt quenching method and characterized by means of X-ray diffraction, FTIR, UV-VIS and EPR spectroscopy. We have examined and analyzed the effects of systematic molybdenum ions intercalation on lead-borate glasses and glass ceramics with interesting results. The observations present in these mechanisms show the lead ions bonded ionic have a strong affinity towards [BO3] units containing non-bridging oxygens and [MoO4]²â» molybdate units. The pronounced affinity towards molybdate anions yields the formation of the PbMoO4 crystalline phase. Then, the excess of oxygen can be supported into the glass network by the formation of [MoO6] and [Mo2O7] structural units. Pb²(+) ions with 6s² configuration show strong absorption in the ultraviolet due to parity allowed s²-sp transition and yield an absorption band centered at about 310 nm. The changes in the features of the absorption bands centered at about 310 nm can be explained as a consequence of the appearance of additional absorption shoulder due to photoinduced color centers in the glass such as the formation of borate-molybdate and lead-molybdate paramagnetic defect centers in the glasses. The concentration of molybdenum ions influences the shape and width of the EPR signals located at g ∼ 1.86, 1.91 and 5.19. The microenvironment of molybdenum ions in glasses is expected to have mainly sixfold coordination. However, there is a possibility of reduction of a part of molybdenum ions from the Mo6(+) to the Mo5(+) and Mo4(+) to the Mo³(+) states.

Dual role of the six-coordinated molybdenum and lead ions in novel of photochromic properties of the molybdenum-lead-borate glasses.

Transparent glasses were prepared by conventional melting-quenching method in the xMoO(3).(100-x)[3B(2)O(3).PbO] system where 0

Infrared spectroscopic and DFT investigations of the vanadate-tellurate glasses structures.

Vanadate-tellurate vitreous systems with composition (1-x)TeO(2).xV(2)O(5) where x=0.3 and 0.4 have been prepared by the conventional melt-quench method. The structural aspects have been investigated using FTIR spectroscopy and the density functional theory (DFT) calculations. The present study provides the interesting information concerning devitrification behavior of the vanadate-tellurate vitreous system which occur Te(2)V(2)O(9) crystalline phase. The structure of the heat-treated glasses was found to consist mainly of rings containing [TeO(3)], [TeO(4)], [VO(4)] and some [VO(5)] structural units.

Toward modeling phosphate tellurate glasses: the devitrification and addition of gadolinium ions behavior.

Glasses in the xGd2O3 x (100 - x)[7TeO2 x 3P2O5] system with 0 < or = x < or = 20 mol % have been prepared using the melt quenching method. The influence of gadolinium ions on structural behavior of the phosphate tellurate glass has been investigated using infrared spectroscopy and density functional theory (DFT) calculations. The addition of gadolinium ions into the host glass matrix leads to an increase of the glass network polymerization due to the replacement of P-O-P bonds by the more resistant P-O-Te bonds having as result the improvement of the chemical durability of the glass. The structural evolution of the studied glasses with the gradual increase of the gadolinium oxide content up to 20 mol % could be explained by considering that the excess of oxygen may be accommodated by the conversion of some orthophosphate structural units into metaphosphate or/and pyrophosphate units. X-ray diffraction and IR spectra revealed that heat treatment of the samples also causes an increase of the glass network polymerization for heat treatment times, t, up to 36 h, while for 36 h > t > or = 48 h showed a drastic structural modification which lead to the apparition of the Te4P2O13 crystalline phase. DFT calculations show that tellurium atoms occupy two different sites in the proposed model. In the first case the tellurium atom is coordinated with four oxygen atoms giving a trigonal bipyramide arrangement, while in the second case the tellurium atom is coordinated with three O atoms. The calculated IR absorption spectrum of the proposed model for phosphotellurite glasses is in good agreement with the experimental absorption data.

Unusual duodenal presentation of leishmaniasis.

This case report describes an atypical case of duodenal leishmaniasis in an elderly patient not infected with human immunodeficiency virus. Investigation of this 84 year old woman with a constitutional syndrome and dysphagia revealed anaemia of chronic disorder, a high erythrocyte sedimentation rate, and polyclonal hypergammaglobulinaemia. Abdominal ultrasonography revealed thickening of the stomach wall, which was seen to be inflamed during gastroscopy. Duodenal histology revealed numerous leishmania amastigotes within macrophages. This was confirmed by bone marrow biopsy and leishmania serology. This case report stresses the importance of atypical symptoms and the unusual location of visceral leishmaniasis, not only in immunodepressed patients, but also in elderly immunocompetent patients.

Linfadenopatías generalizadas y síndrome constitucional en una anciana de 94 años / Generalised lymphadenopathies and constitutional syndrome in a 94-year-old woman

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