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71.
Fernando P. Carvalho João M. Oliveira M. Malta M. Eugénia Lemos 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(1):119-125
During the past century extensive uranium mining took place in Portugal for radium and uranium production. One such uranium mine was the Boco Mine, in operation during the 1960s and 70s. Mining waste and open pits were left uncovered since mine closure. During the nineties a quarry for sand extraction was operated in the same site and water from a local stream was extensively used in sand sieving. Downstream the mine area, agriculture soil is used for cattle grazing. Water from the stream, water wells, soil, pasture and sheep meat were now analyzed for radionuclides of uranium natural series. The U-series radionuclide 226Ra was generally the highest in concentrations especially in soil, pasture, and in internal organs of sheep. 226Ra concentrations were 1,093 ± 96 Bq/kg (dry weight, dw) in soil, 43 ± 3 Bq/kg (dw) in pasture, and 193 ± 84 mBq/kg (wet weight, ww) in muscle tissue of sheep. Other sheep internal organs displayed much higher 226Ra concentrations, such as the brain and kidneys with 1,850 ± 613 mBq/kg (ww) and 6,043 ± 6,023 mBq/kg (ww), respectively. Results of analyses of tissue samples from sheep grown in a comparison area were 2 to 16 times lower, depending on the organ. Absorbed radiation doses for internal organs were computed and may exceed 5.2 mGy/y in the case of kidneys, near three times higher than in animals from the reference area, but below the threshold for biological effects. Radionuclide transfer in the terrestrial food chain and radiation exposure of the human population is discussed. 相似文献
72.
Vnia S. F. Muralha Sara Canaveira Jos Miro Susana Coentro Teresa Morna Carlo Stefano Salerno 《Journal of Raman spectroscopy : JRS》2015,46(5):483-492
For the first time, 18th‐century glass mosaics from the Capela de São João Baptista (Chapel of St. John the Baptist, Lisbon) were analysed by Raman microscopy (RM). This masterpiece in baroque mosaic art had one of its major contributors the most famous glassmaker in Rome, Alessio Mattioli. Mattioli was celebrated because of the opacity of his mosaics and the astonishing number of hues he was able to produce for mosaic decorating Saint Peter's Basilica in Rome. This study had two goals in mind: (1) characterising the materials involved in the manufacture of these glass mosaics and (2) lengthening the understanding of what was left of Mattioli's glassmaking records. As expected the mosaics presented a high ratio of crystalline phases, making RM the ideal technique for non‐destructive analysis. The mosaics contained a white ‘background’ or opacifier added identified as Ca2Sb2O7. The yellow tesserae are opacified with lead antimonate (Pb2Sb2O7) and ternary oxides, structures related to lead antimonate but with other ions entering the position of Sb4+ (namely Sn4+). Those ternary oxides are pervasive in most colours, admixed with other colorants. The red, orange, pink and brown colours were accomplished with cuprous oxide (Cu2O) and admixed with a ternary oxide to create the latter three colours. The red copper‐based colours were made according to the procedure to make a ruby copper glass and with the exception of the red colour; all mosaics exhibited a dark layer on each side of the mosaic, named scorzetta. This layer is the outcome of an oxidation reaction because of a quick cooling process and is composed of CuO. Finally the blue and green colours are accomplished with cobalt oxide and copper oxide, respectively, and the purple/black colour with manganese oxide. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
73.
We report on an accurate intensity calibration method for low wavenumber Raman spectroscopy. It uses the rotational Raman spectrum of N2. The intensity distributions in the rotational Raman spectra of diatomic molecules are theoretically well established. They can be used as primary intensity standards for intensity calibration. The intensity ratios of the Stokes and anti‐Stokes transitions originating from the same rotational levels are not affected by thermal population. Taking the effect of rotation–vibration interactions appropriately into account, we are able to calculate these intensity ratios theoretically. The comparison between the observed and calculated ratios of the N2 pure rotational spectrum provides an accurate relative sensitivity curve (error ~5 × 10−4) in the wavenumber region of −150 to 150 cm−1. We determine the temperature of water solely from the low wavenumber Raman spectra, using a thus calibrated spectrometer. The Raman temperature shows an excellent agreement with the thermocouple temperature, with only 0.5 K difference. The present calibration technique will be highly useful in many applications of low wavenumber quantitative Raman spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
74.
do Nascimento Ticiano Gomes Borges Arthur Luy Tavares Ferreira de Almeida Lara Mendes Ribeiro Êurica Adélia Nogueira Silva Fernanda Geny Calheiros da Costa Silva Valdemir do Nascimento Prata Ana Paula Basílio-Júnior Irinaldo Diniz Goulart Marília Oliveira Fonseca Morilla Demetrius Peireira de Freitas Johnnatan Duarte Aragão Cícero Flávio Soares 《Journal of Thermal Analysis and Calorimetry》2022,147(21):11949-11963
Journal of Thermal Analysis and Calorimetry - This work prepared and characterized microcapsule of Uncaria tomentosa (UT) in order to standardize a spray-dryer Uncaria tomentosa extract. The UT... 相似文献
75.
We numerically calculate the conductivity sigma of an undoped graphene sheet (size L) in the limit of a vanishingly small lattice constant. We demonstrate one-parameter scaling for random impurity scattering and determine the scaling function beta(sigma)=dlnsigma/dlnL. Contrary to a recent prediction, the scaling flow has no fixed point (beta>0) for conductivities up to and beyond the symplectic metal-insulator transition. Instead, the data support an alternative scaling flow for which the conductivity at the Dirac point increases logarithmically with sample size in the absence of intervalley scattering--without reaching a scale-invariant limit. 相似文献
76.
We study the low-lying baryon spectrum (up to 2.2 GeV) provided by experiments and different quark models using statistical tools which allow us to postulate the existence of missing levels in spectra. We confirm that the experimental spectrum is compatible with random matrix theory, the paradigmatic model of quantum chaos, and we find that the quark models are more similar to a Poisson distribution, which is not compatible with what should be expected in a correlated spectrum. From our analysis it stems that the spectral fluctuation properties of quark-model spectra are incompatible with experimental data. This result can be used to enlighten the problem of missing resonances. 相似文献
77.
Paiva GS Pavão AC Alpes de Vasconcelos E Mendes O da Silva EF 《Physical review letters》2007,98(4):048501
We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation. 相似文献
78.
79.
de Souza EA Neves CA de Oliveira Campos LA Zanuncio JC Serrão JE 《Micron (Oxford, England : 1993)》2007,38(5):471-477
The effect of mating delay on the ovary structure of virgin queens of Melipona quadrifasciata anthidioides (Hymenoptera: Apidae) was investigated. Virgin queens 15, 20, 25 and 30 days old were dissected to analyze their degree of ovary degeneration. To verify whether the degeneration would cause permanent sterility, virgin queens of the same ages (15, 20, 25 and 30 days) were mated and accompanied for at least 14 days to verify whether there was physogastry and then dissected. The ovaries were analyzed by histology, histochemical tests and TUNEL to verify programmed cell death. The results showed that mating delay interrupted oogenesis preventing vitellogenesis. Mating delay results in ovary degeneration which increased with queen age. However, even when there was ovariole degeneration, 25-day-old virgin queens after mating presented normal ovariole activation. 相似文献
80.
A. N. Kornienko S. G. Pil’o V. M. Prokopenko V. S. Brovarets 《Russian Journal of General Chemistry》2014,84(6):1186-1189
Chlorination of 2-aryl-5-benzylsulfanyl-1,3-oxazole-4-carbonitrile in aqueous acetic acid at 50–60°C afforded new 2-aryl-5-chloro-1,3-oxazole-4-carboxamides. The reactivity of the chlorine atom with respect to the N-, O-, and S-nucleophiles was investigated. 相似文献