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Evaluation of the bactericidal and trypanocidal activities of triterpenes isola...
Abreu,Viviane G. C.; Takahashi,Jacqueline A.; Duarte,Lucienir P.; Piló-Veloso,Dorila; Junior,Policarpo A. S.; Alves,Rosana O.; Romanha,Alvaro J.The phytochemical investigation on the aereal parts of Lychnophora pinaster Mart., Asteraceae, was carried to isolation of triterpenes. 3-O-Acetyl-lupeol (1), 3-O-acetyl-pseudotaraxasterol (2), and 3-O-acetyl-α-amyrin (3) were isolated from hexanic extract and 4,4-dimethyl-cholesta-22,24-dien-5-ol (4), α-amyrin (5), and lupeol (6) were isolated from hexanic/dichlorometanic extract of the leaves. Compo...
Neutron capture cross section measurements for nuclear astrophysics at CERN n_TOF
Abbondanno, U.; Aerts, G.; Alvarez-Velarde, F.; Álvarez-Pol, H.; Andriamonje, S.; Andrzejewski, J.; Badurek, G.; Baumann, P.; Becvár, F.; Benlliure, J.A series of neutron capture cross section measurements of interest to nuclear astrophysics have been recently performed at n_TOF, the neutron spallation source operating at CERN. The low repetition frequency of the proton beam driver, the extremely high instantaneous neutron flux, and the low background conditions in the experimental area are optimal for capture cross section measurements on low-mass or radioac...
A low-mass neutron flux monitor for the n _TOF facility at CERN
Mastinu,P. F.; Abbondanno,U.; Aerts,G.; Alvarez,H.; Andriamonje,S.; Angelopoulos,A.; Assimakopoulos,P.; Bacri,C.O.; Badurek,G.; Baumann,P.; Becvár,F.A small-mass system has been developed for monitoring the flux of neutrons with energy up to 1 MeV at the new time-of-flight facility at CERN, n_TOF. The monitor is based on a thin Mylar foil with a 6Li deposit, placed in the neutron beam, and an array of Silicon detectors, placed outside the beam, for detecting the products of the 6Li(n, alpha)³H reaction. The small amount of material on the beam ensures a min...
Measurement of the refractive index and attenuation length of liquid xenon for ...
Solovov, V. N.; Chepel, V.; Lopes, M. I.; Hitachi, A.; Marques, R. Ferreira; Policarpo, A. J. P. L.The attenuation length and refractive index of liquid xenon for its intrinsic scintillation light ([lambda]=178 nm) have been measured in a single experiment. The value obtained for the attenuation length is 364±18 mm. The refractive index is found to be 1.69±0.02. Both values were measured at a temperature of 170±1 K. ; http://www.sciencedirect.com/science/article/B6TJM-49J93GG-5/1/7efa40cf2d4dc7beeee408098...
Performance of an optical readout GEM-based TPC
Margato, L. M. S.; Fraga, F. A. F.; Fetal, S. T. G.; Fraga, M. M. F. R.; Balau, E. F. S.; Blanco, A.; Marques, R. Ferreira; Policarpo, A. J. P. LWe report on the operation of a GEM-based small TPC using an optical readout. The detector was operated with a mixture of Ar+CF4 using 5.48 MeV alpha particles obtained from a 241Am source and the GEM scintillation was concurrently read by a CCD camera and a photomultiplier. Precision collimators were used to define the track orientation. Qualitative results on the accuracy of the track angle, length and charge...
Progress in timing Resistive Plate Chambers
Blanco, A.; Carolino, N.; Correia, C. M. B. A.; Ferreira-Marques, R.; Fonte, P.; Gobbi, A.; González-Díaz, D.; Lopes, M. I.; Lopes, L.; Macedo, M. P.Timing RPCs are Resistive Plate Chambers made with glass and metal electrodes separated by precision spacers. Typical gas gaps are a few hundred micrometers wide. Such counters were introduced in 1999 and have since reached timing accuracies below 50 ps [sigma] with efficiencies above 99% for MIPs. Applications in high-energy physics have already taken place with several more under study. ; http://www.scienc...
A large area timing RPC prototype for ion collisions in the HADES spectrometer
Alvarez Pol, H.; Alves, R.; Blanco, A.; Carolino, N.; Eschke, J.; Ferreira-Marques, R.; Fonte, P.; Garzón, J. A.; González Díaz, D.; Pereira, A.We present a resistive plate chamber (RPC) prototype for time-of-flight measurements over large areas and at high occupancies, minimizing the inter-channel cross-talk. ; http://www.sciencedirect.com/science/article/B6TJM-4D75GPD-9/1/a6fe40c114a867a0f98e2fec0f133503
Development of high-rate timing RPCs
Lopes, L.; Marques, R. Ferreira; Fonte, P.; Pereira, A.; Peskov, V.; Policarpo, A.For many applications of RPCs to time-of-flight counters in heavy ion experiments the expansion to much higher values of the counting rate capability, so far limited to around 2 kHz/cm2 is of fundamental importance. To address this issue we developed single-gap timing RPCs with resistive electrodes made from a commercially available plastic material. Tests performed in photon beams yielded a time resolution aro...
Performance of shielded timing RPCs in a 12C fragmentation experiment
Alvarez Pol, H.; Alves, R.; Blanco, A.; Carolino, N.; Eschke, J.; Ferreira-Marques, R.; Fonte, P.; Garzón, J. A.; González Díaz, D.; Pereira, A.We show the feasibility of large area timing RPC detectors for experiments dealing with fragmentation-like primary interactions and/or high detector multiplicities, without significative degradation of the detector capabilities. The tested prototype is constituted by three independent cells placed into grounded aluminium boxes, which reduce the cross-talk to the level of 0.4%. Each box consists of a 4-gap glass...
A study of ageing in timing RPCs
Lopes, L.; Ferreira-Marques, R.; Fonte, P.; Piedade, A. P.; Policarpo, A.The present study concerns the search for ageing effects in 0.3 mm gap timing RPCs. Counters were made with glass and aluminium electrodes and kept under a continuous gas flow of tetrafluorethane with 10% sulphur hexafluoride, 5% isobutane and water at 10% relative humidity. After 500 days of operation at the saturation current an accumulated charge of 800 mC was collected, equivalent to over 8 years of continu...
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