Silver Nanoparticles Enhance Thermoluminescence and Photoluminescence Response in Li2B4O7 Glass Doped with Dy3+ and Yb3.

Lithium borate glass matrices doped with Dy3+ and Yb3+, containing silver nanoparticles in different concentrations are synthesized and characterized in this work. The Scanning Transmission Electron Microscopy confirms formation of silver nanoparticles in the samples. Absorption spectra of the samples show the presence of a broadband spectrum associated due to the surface plasmon effect of the silver nanoparticles. A strong surface plasmon band bellow 400 nm appears after the annealing process, due to the formation of silver nanoparticles with radius of 5-15 nm. The transition peaks of Dy3+ are also observed at 386, 446, 798, 917, 1088, 1265 and 1669 nm. Additionally, a large peak at 976 nm belonging to the absorption band corresponding to the Yb3+ is observed. Emission spectra under 406 nm pumping show two prominent bands at 506 and 590 nm belonging to the Dy3+ transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2, respectively. The fluorescence in the 480 nm and 525 nm spectral ranges enhanced with the silver nanoparticles contained in the samples. Is the first time, the luminescence studies of the lithium borate matrix doped with Dy3+ and Yb3+ containing silver nanoparticles is done. The basic parameters defining the lasing-amplifying potential of the glass matrices as a function of silver nanoparticles concentration are calculated. The Thermoluminescence response to UV irradiation also exhibits significant enhancement with the increment of silver nanoparticles in the samples.

Thermoluminescent characterization of HfO2:Tb3+ synthesized by hydrothermal route.

Thermo and photoluminescent properties of nanoparticles (NPs) of hafnium oxide (HfO2), both intrinsic and doped with terbium (Tb(3+)) are reported. The NPs of HfO2 were synthesized by hydrothermal route, using hafnium tetrachloride (HfCl4) and terbium chloride hexahydrated (TbCl3∙6H2O) as precursors and sodium hydroxide (NaOH) to adjust the pH. Deionized water was used as solvent in all cases. The synthesis was carried out at different dopant concentrations from 0 to 20 at% of terbium with respect to the amount of hafnium in the precursor solution. The temperature of hydrothermal treatment was 200 °C and 80 min of reaction time. X-ray diffraction results show that at terbium concentrations higher than 15 at% the HfO2 nanoparticles have a crystalline structure corresponding to the tetragonal phase. Thermoluminescent (TL) characterization was performed after 5 min irradiation of the samples with ultraviolet light of 200 nm wavelength. The highest TL emission was observed on samples with 7 at% of Tb, with the TL peak centered at 128 °C. Thermoluminescence analysis shows behavior associated with second-order kinetics with activation energy of 0.49 eV. Photoluminescent spectrum present the characteristics (5)D4→(7)FJ (J=3-6) terbium ion electronic transitions lines centered on 489 nm, 543 nm, 584 nm and 622 nm.

Concentration of DL-PCBs in fish from market of Parma city (north Italy): estimated human intake.

The concentrations of 12 congeners of non-ortho and mono-ortho dioxin-like polychlorinated biphenyls (ΣDL-PCB) were measured in 30 fish samples from Parma markets by GC/MS technique. The samples were randomly purchased, choosing the species commonly found in supermarkets. The concentration of DL-PCBs estimated remained under the fixed Italian limit of 4 pg g(-1)ww WHO-TEQ (World Health Organization-Toxic Equivalent) in the major part of the samples, so the situation seems to be not at a level sufficient to pose a risk to human health of the Parma population. The medium daily intake for DL-PCBs for Italian consumers (Parma) was also estimated. This value generally resulted minor than 2 pg g(-1) ww WHO-TEQ kg(-1) body weight, exceeding only in four cases: eel, smooth hound, starry smooth hound and tuna.

The relaxation induced by S-nitroso-glutathione and S-nitroso-N-acetylcysteine in rat aorta is not related to nitric oxide production.

S-nitroso-glutathione (GSNO) and S-nitroso-N-acetylcysteine (NACysNO) are nitrosothiols that release nitric oxide (NO) and mimic the effects of endogenous NO. This study investigated the relaxation induced by GSNO and NACysNO in rat aorta and the relation between relaxation and NO formation. Both compounds at concentrations from 10(-9) M to 10(-4) M relaxed the rat aorta in a concentration-dependent manner. However, NO production depended on the concentration of nitrosothiols present and was detected only above 100 microM GSNO or NACysNO. To determine whether K+ channels are involved in the relaxation induced by nitrosothiols, the contractions were induced with KCl at concentrations of 30, 60, or 90 mM. The concentration-effect curves for the relaxation induced by nitrosothiols were shifted to the right for all the K+ concentrations compared with aortas precontracted with phenylephrine. These results indicate the participation of K+ channels in the relaxation induced by GSNO and NACysNO. A selective inhibitor of soluble guanylyl cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, significantly inhibited the relaxation induced by the nitrosothiols. The relaxation induced by GSNO and NACysNO was inhibited by the K+ channel blockers glibenclamide, selective K(ATP) channels, and apamin, selective for low-conductance Ca2+-activated K+ channels in rat aorta, but was not inhibited by charybdotoxin, a potent and selective Ca2+-activated K+ channel blocker, or by 4-aminopyridine, a voltage-gated K+ channel blocker. These results indicate that relaxation induced by GSNO and NACysNO is partially due to activation of K(ATP) channels and partially due to activation of low-conductance Ca2+-activated K+ channels. However, the ability of the nitrosothiol compounds to overcome the inhibitory effect of high extracellular K+ concentrations suggests another mechanism of relaxation contributing to the nitrosothiol response. The most intriguing finding is that relaxation is not related to the NO produced in rat aorta.

Alterations of calcium uptake in renovascular hypertensive rat aorta: functional assessment with thapsigargin.

1. The aim of this study was to test the hypothesis that impaired calcium (Ca2+) recycling by sarcoplasmic reticulum (SR) Ca2+-ATPase takes place in aortae from 1 kidney-1 clip (1K-1C) hypertensive rats. 2. The contractile response elicited when Ca2+ is released from the SR with phenylephrine and caffeine in Ca2+-free Krebs solution was greater in 1K-1C than in 1K rat aorta. In the arteries submitted to intracellular Ca2+ store depletion and reloading, this response was not different between 1K-1C and 1K rat aortae. Thapsigargin decreased the phasic contractile responses to phenylephrine in 1K and 1K-1C rat aortae and increased the tone that developed during the refilling period in 1K-1C rat aortae. 3. Our data support the hypothesis that the 1K-1C rat aorta has defective intracellular Ca2+ regulation that may be implicated in an inadequate SR buffering ability.

Increased contractile response induced with ouabain is abolished by thapsigargin in aorta of renal hypertensive rats.

1. The aim of the present study was to test in vitro if the increased contractile effect of phenylephrine and KCl, observed after the addition of ouabain in renal hypertensive rat aorta, is mediated by Ca2+ accumulated on the sarcoplasmic reticulum. 2. In aortas of one kidney (1K) rats, ouabain did not modify the concentration-effect curves stimulated with phenylephrine and KCl. 3. Contractile responses stimulated with phenylephrine and KCl were potentiated by ouabain in one kidney--one clip (1K-1C) aortas, and preincubation with thapsigargin abolished the increasing effect of ouabain on these contractions. 4. The addition of thapsigargin before phenylephrine and KCl did not modify the contractile response to phenylephrine and KCl or the resting vascular tone during the time incubation. 5. In the presence of ouabain, thapsigargin significantly increased the vascular tone only in 1K-1C rat aortas. 6. Increased intracellular Na+ concentration as a consequence of Na(+)-K(+)-ATPase inhibition induces increased accumulation of Ca2+ inside the sarcoplasmic reticulum in 1K-1C rat aortas. The differential effects in renal hypertensive and normotensive aortas suggest a possible role of this mechanism in modulating cytosolic Ca2+ in renal hypertension.

Seguimiento epidemiológico del colera en la provincia del Chimborazo

Se realizó un seguimiento epidemiológico del cólera a nivel provincial y nacional desde el inicio de la epidemia hasta el 31 de diciembre de 1991. A nivel país hasta el 30 de mayo de 1991 afectó a 19 provincias con 20.188 casos, de los cuales 342 fallecimiento, con una incidencia de 2.1 x 1.000 habitantes y una tasa de letalidad de 1.7 x cada 100 enfermos. A nivel provincial se confirmó el primer caso, el 4 de abril en el Cantón Colta, Pulucate (Santo Tomás) y hasta el 31 de Diciembre de 1991 se presentaron un total de 3.211 casos reportados y 108 defunciones, con una tasa de letalidad de 3 por cada 100 enfermos; el período promedio de incubación fue de 3 días, con una fuente de contagio inicial, un medio común de origen alimentario. La mayoría de los casos 71 por ciento fue en el grupo de mayores de 15 años y 29 por ciento en menores de 15 años; afectando por igual a ambos sexos. Las provincias de mayor letalidad: Chimborazo, Cotopaxi, Bolivar, Imbabura y Loja. Los picos máximos de incidencia del cólera en Chimborazo fueron en: abril, junio y noviembre, coincidiendo con la tendencia presentada a nivel nacional. En Chimborazo Los cantones afectados por la epidemia fueron: el Cantón Riobamba, seguido del Cantón Colta. Del Análisis de las tasas de incidencia del colera, con el índice de deterioro, aparentemente no existe una relación estadisticamente significativa, la cual puede explicarse por una realidad provincial que esconde las diferencias cantonales. La letalidad del colera por provincias en relación con los índices de deterioro muestran una analogía que está en relación con la falta de servicios básicos.

[Coverage and quality of the registration of perinatal deaths occurring in health institutions in the Federal District]. / Cobertura y calidad del registro de defunciones perinatales ocurridas en instituciones de salud del Distrito Federal.

"This paper presents the results of the first direct attempt at evaluating the coverage of the perinatal death registration in the Distrito Federal [of Mexico]; this study is based on the information gathered from 574 deaths which took place in 23 hospitals in the Distrito Federal during a three month period in 1984. Both the causes of the failure to register many of these deaths and the quality of the information presented in perinatal death certificates are pointed out and discussed here. According to the evidence analyzed, it is clear that underregistration in the Distrito Federal is extremely marked.... The paper suggests the possibility of establishing a hospital registration system which would keep a record of both deaths and births. It also stresses the need for establishing rules to detect fetal deaths plus the need for unifying criteria regarding the definition of 'live birth'." (SUMMARY IN ENG)