5 resultados para Ton
em Biblioteca Digital da Produção Intelectual da Universidade de São Paulo
Resumo:
Mining operations around the world make extensive use of blasthole sampling for short-term planning, which has two undisputed advantages: (1) blastholes are closely spaced providing relatively high sampling density per ton, and (2) there is no additional cost since the blastholes must be drilled anyway. However, blasthole sampling usually presents poor sampling precision, and the inconstant sampling bias caused by particle size and density segregation is an even more serious problem, generally precluding representativeness. One of the main causes of this bias is a highly varying loss of fines, which can lead to both under- and over-estimation of grade depending on the ore type and the gangue. This study validates a new, modified sectorial sampler, designed to reduce the loss of fines and thereby increase sampling accuracy for narrow-diameter blasthole sampling. First results show a significantly improved estimation of gold grade as well as the minimization of the loss of fines.
Resumo:
BACKGROUND: Alkaline sulfite/anthraquinone (ASA) cooking of Pinus radiata and Pinus caribaea wood chips followed by disk refining was used as a pretreatment for the production of low lignified and high fibrillated pulps. The pulps produced with different delignification degrees and refined at different energy inputs (250, 750 and 1600 Wh) were saccharified with cellulases and fermented to ethanol with Saccharomyces cerevisiae using separated hydrolysis and fermentation (SHF) or semi-simultaneous saccharification and fermentation (SSSF) processes. RESULTS: Delignification of ASA pulps was between 25% and 50%, with low glucans losses. Pulp yield was from 70 to 78% for pulps of P. radiata and 60% for the pulp of P. caribaea. Pulps obtained after refining were evaluated in assays of enzymatic hydrolysis. Glucans-to-glucose conversion varied from 20 to 70%, depending on the degree of delignification and fibrillation of the pulps. The best ASA pulp of P. radiata was used in SHF and SSSF experiments of ethanol production. Such experiments produced maximum ethanol concentration of 20 g L-1, which represented roughly90% of glucose conversion and an estimated amount of 260 L ethanol ton(-1) wood. P. caribaea pulp also presented good performance in the enzymatic hydrolysis and fermentation but, due to the low amount of cellulose present, only 140 L ethanol would be obtained from each ton of wood. CONCLUSION: ASA cooking followed by disk refining was shown to be an efficient pretreatment process, which generated a low lignified and high-fibrillated substrate that allowed the production of ethanol from the softwoods with high conversion yields. (C) 2012 Society of Chemical Industry
Resumo:
Prevalence of Toxoplasma gondii infection in 510 free-range (FR) chickens (380 from 33 small farms, and 130 from a slaughter house for FR chickens) from Espirito Santo state, southeastern Brazil, was investigated. Antibodies to T. gondii were sought using commercial indirect haemagglutination (IHAT, Imuno-HAI Toxo (R), Wama Diagnostica, Sao Paulo, Brazil, cut-off 1:16) and the modified agglutination test (MAT, cut-off 1:25) tests. Attempts were made to isolate viable T. gondii from seropositive chickens by bioassay in mice. Pooled samples of brain, heart and quadriceps muscle of one thigh (total 40 g) from 64 chickens with IHAT titers of >= 1:16 were minced, digested in pepsin and bioassayed in mice. Antibodies to T. gondii were found in 40.4% (206/510) FR chickens by IHAT (titer >= 1:16) and 38.8% (198/510) by MAT (titer >= 1:25); concordance between IHAT and MAT was 81.6% (kappa index = 0.614). Viable T. gondii was isolated (designated TgCkBr234-281) from 48 of 64(75%) seropositive (IHAT titers >= 1:32) FR chickens. Most isolates of T. gondii were virulent for mice; 100% of mice inoculated with 44 of 48 isolates died of toxoplasmosis within 30 days post inoculation (p.i). An epidemiological investigation revealed that people living in rural areas have little knowledge about the parasite and about the risk of acquiring it from raw meat. Results indicated that the locally available IHAT was useful for screening of chicken sera for T. gondii antibodies. (C) 2012 Elsevier B.V. All rights reserved.
Resumo:
We investigate standard and non-standard solar neutrino signals in direct dark matter detection experiments. It is well known that even without new physics, scattering of solar neutrinos on nuclei or electrons is an irreducible background for direct dark matter searches, once these experiments reach the ton scale. Here, we entertain the possibility that neutrino interactions are enhanced by new physics, such as new light force carriers (for instance a "dark photon") or neutrino magnetic moments. We consider models with only the three standard neutrino flavors, as well as scenarios with extra sterile neutrinos. We find that low-energy neutrino-electron and neutrino-nucleus scattering rates can be enhanced by several orders of magnitude, potentially enough to explain the event excesses observed in CoGeNT and CRESST. We also investigate temporal modulation in these neutrino signals, which can arise from geometric effects, oscillation physics, non-standard neutrino energy loss, and direction-dependent detection efficiencies. We emphasize that, in addition to providing potential explanations for existing signals, models featuring new physics in the neutrino sector can also be very relevant to future dark matter searches, where, on the one hand, they can be probed and constrained, but on the other hand, their signatures could also be confused with dark matter signals.
Resumo:
This pioneering study characterized the chemical, physical and mineralogical aspects of the Urucum Standard manganese ore typology, and evaluated some of its metallurgical characteristics, such as the main mineral heat decompositions, and the particle disintegration at room temperature and under continuous heating. A one-ton sample of ore was received, homogenized and quartered. Representative samples were collected and characterized with the aid of techniques, such as ICP-AES, XRD, SEM-EDS, BET and OM. Representative samples with particle sizes between 9.5 mm and 15.9 mm were separated to perform tumbling tests at room temperature, and thermogravimetry tests for both air and nitrogen constant flow at different temperatures. After each heating cycle, the mechanical strength of the orewas evaluated by means of screening and tumbling procedures. The Urucum Standard typology was classified as an oxidized anhydrous ore, with a high manganese content (~47%). This typology ismainly composed of cryptomelane and pyrolusite; however there is a significantamount of hematite. The Urucum Standard particles presented low susceptibility to disintegration at room temperature, but as temperature increased, susceptibility increased. No significant differences were observed between the tests done with the air or nitrogen injections.