Reflectance of Polytetrafluoroethylene (PTFE) for Xenon Scintillation Light

Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet wavelength region (175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Fluoropolymers, namely ETFE, FEP and PFA were also measured

Anti-inflammatory, anti-proliferative and antioxidant profiles of selective cyclooxygenase-2 inhibition as chemoprevention for rat bladder carcinogenesis

PURPOSE: To evaluate the efficacy of a selective cyclooxygenase-2 (COX-2) inhibitor in rat bladder cancer chemoprevention, as well as to assess the relevance of inflammation, proliferation and oxidative stress in tumor growth and in its prevention. RESULTS: The main findings were: (I) the incidence of carcinoma was: control: 0% (0/8); BBN: 65% (13/20); CEL: 0% (0/8) and BBN + CEL: 12.5% (1/8); (II) the mean tumor volume per rat with tumor and per tumor were significantly lower in the BBN + CEL group (21.2 and 5.3 +/- 0.4 mm(3)) vs. BBN (138.5 +/- 7.5 and 112.5 +/- 6.4 mm(3)); (III) the incidence of pre-neoplasic (hyperplasia and dysplasia) and neoplasic (papillary tumors and carcinoma in situ-CIS) lesions were notoriously reduced in the CEL + BBN treatment; (IV) CEL significantly reduced serum TGFbeta1 and CRP and increase TNFalpha and IL-1beta (p < 0.001); (V) CEL reduced MDA formation in serum (p < 0.001) and liver (p < 0.05) and also showed a trend to reduction in kidney. METHODS: Drug treatments were performed during the first 8 w, followed by 12 w for tumor expression/prevention, in the following groups: control-vehicle; carcinogen-0.05% of N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN); celecoxib (CEL)-10 mg/kg/day and preventive CEL + BBN. The bladders were analyzed for number and volume of tumor and nature of urothelium lesions. Serum was assessed for markers of inflammation, proliferation and redox status. CONCLUSIONS: Celecoxib has demonstrated an outstanding inhibitory effect on bladder cancer chemoprevention, which might be due to its expected anti-inflammatory actions, as well as by anti-proliferatory and antioxidant actions. This data supports a pivotal role of cancer chemoprevention strategies based on COX-2 inhibition

A survey of energy loss calculations for heavy ions between 1 and 100 keV

The original Lindhard-Scharff-Schi{\o}tt (LSS) theory and the more recent Tilinin theory for calculating the nuclear and electronic stopping powers of slow heavy ions are compared with predictions from the SRIM code by Ziegler. While little discrepancies are present for the nuclear contribution to the energy loss, large differences are found in the electronic one. When full ion recoil cascade simulations are tested against the elastic neutron scattering data available in the literature, it can be concluded that the LSS theory is the more accurate.Comment: Presented at the 10th International Symposium on Radiation Physics, 17-22 September, 2006, Coimbra, Portugal; style corrections, small change to fig.

A model of the reflection distribution in the vacuum ultra violet region

A reflection model with three components, a specular spike, a specular lobe and a diffuse lobe is discussed. This model was successfully applied to describe reflection of xenon scintillation light (175 nm) by PTFE and other fluoropolymers and can be used for Monte Carlo simulation and analysis of scintillation detectors. The measured data favors a Trowbridge-Reitz distribution function of ellipsoidal micro-surfaces. The intensity of the coherent reflection increases with increasing angle of incidence, as expected, since the surface appears smoother at grazing angles. The total reflectance obtained for PTFE is about 70% for VUV light at normal incidence in vacuum and estimated to be up to 100% in contact with liquid xenon

Estudo de solos do município de Encruzilhada do Sul - RS.

bitstream/item/30598/1/Circular-45.pdf; bitstream/item/30600/1/aptidao-bmp-final.pdf; bitstream/item/30616/1/capacidade-bmp-final.pdf; bitstream/item/30623/1/relevo-bmp-final.pdf; bitstream/item/30634/1/vegetacao-bmp-final.pd

Scintillation efficiency of liquid xenon for nuclear recoils with the energy down to 5 keV

The scintillation efficiency of liquid xenon for nuclear recoils has been measured to be nearly constant in the recoil energy range from 140 keV down to 5 keV. The average ratio of the efficiency for recoils to that for gamma-rays is found to be 0.19+-0.02.Comment: 13 pages, 5 figure

Estudo de solos do município de Esperança do Sul - RS

bitstream/item/30800/1/Circular-49.pdf; bitstream/item/33471/1/aptidao.pdf; bitstream/item/33473/1/vegetacao.pd

Coquetel vegetal: produção de fitomassa e teores de macro e micronutrientes de espécies para adubação verde e/ou cobertura do solo.

A fitomassa produzida por coquetéis vegetais tem influência direta na melhoria das condições do solo contribuindo com a diminuição das perdas de nutrientes por lixiviação e diminuição da erosão; com a manutenção da umidade e melhoria da infiltração, além de colaborar no controle de ervas espontâneas; auxiliam na disponibilização de nutrientes, principalmente as espécies leguminosas, e na melhoria da estruturação do solo pelas gramíneas. Diante do exposto, o presente trabalho teve como objetivo avaliar a produção da fitomassa e os teores de macro e micronutrientes de espécies vegetais para adubação verde e/ou cobertura do solo. A pesquisa foi desenvolvida na Estação Experimental de Agricultura Irrigada da Embrapa Semiárido, em Petrolina, PE. Foram avaliadas 14 espécies vegetais em diferentes opções de coquetéis vegetais que constituíram cinco tratamentos mais o tratamento referência. Os resultados demonstram que o coquetel vegetal é uma alternativa de manejo que contribui para aumentar a biodiversidade (diversificação de espécies) dentro e acima do solo, estabelecendo um ambiente onde as espécies convivem harmoniosamente. Os tratamentos T3 e T4 apresentaram as melhores produções de fitomassa para as condições de solo e clima do Polo Petrolina, PE/Juazeiro, B

NDVI da canola obtido com sensor Green Seeker e calculado a partir de dados hiperespectrais.

Orientador: Genei Antonio Dalmago

LUX Cryogenics and Circulation

We report the effciency of a thermosyphon-based cooling system for a liquid xenon (LXe) time projection chamber (TPC), as well as the effciency of a unique internal heat exchanger with standard gas phase purification using a heated getter, which allows for very high flow purification without requiring large cooling power.Peer Reviewe