1,027 research outputs found
Produtividade estacional, melhoramento e manejo de pastagens na Ilha de Marajó.
bitstream/item/57747/1/CPATU-ComTec51.pd
Electroanalysis of Heavy Metals in the Cork of Quercus Suber
This will enable Pb(II) determination optimisation, regarding environmental aspects of
the perpetuation of Quercus suber Montado (similar to Forest). It will also allow a more
profound toxicological quality control of corks (barks). These two last referred aspects
are very related ones, once accepted that the more advanced could the certification of
the quality patterns of corks (barks) be, more will be the sustainability of Quercus suber
ecosystem. Which we believe can be done, amongst other vectors, by studying such an
important environmental issue as heavy metals. It is shown that Pb(II) quantification in
the cork (bark) of Quercus suber tree (Cork Oak) is possible, using Differential Pulse
Anodic Stripping Voltammetry (DPASV). The samples digestion was made in a
mixture of H2O2 and HNO3 1:8, in a closed recipient at approximately 90 ºC. The
measures were made in NaCl 0.1 M, using a Hanging Mercury Drop Electrode, a
Glassy-Carbon Rod Counter Electrode, and an Ag/AgCl/KCl 3M reference electrode,
after a 180 s deposition step. The results have shown the determination of a coherent
stripping potential of -0.405 V (SD=0.0005 V), and a fine linear adjustment after the
standard addition method (R2 = 0.997). They have also revealed the interest of further
studies. The need to test other electroanalysis requisites was understood, and imposed
by the proof of the complex nature of the matrix
THE IMPORTANCE OF THE CORK (BARK) OF QUERCUS SUBER IN THE
The recent absence of Lead element as catalyst in internal explosion motors, being an extremely
important action for the stop of this environmental aggression, has no effect in the minimization of the
harm this element does in the positions where its deposition now lays. The impact of the ubiquity of
pollution, in this case Lead pollution, needs to have monitoring tools. The greatest of the tools one can
have is the analysis of the content of a strong indicator. One that stands for a long time in one place, for
which it is able to receive the marks of the analyte passage. Quercus suber (Cork Oak) tree is such a case.
Having a life expectation ranging from 200 to 500 years (depending on the cork extraction intensity) and
with a capability of regeneration of its cork coverture, it concentrates the amounts of Lead, with which it
had contacted through its life, in successive layers, corresponding, the larger ones, to the high
temperatures season, and the thinner ones to the low temperatures season. So, the analysis of the content
of the element in a layer of cork with a given amount of years in the tree, will be a good estimator of how
the content of Lead as evolved in the area. And a correct distribution of sampling trees will show much
more about a greater area. The possibility of choosing years by choosing layers of cork, and the fact that
the sampling will not harm the tree, if properly done, make this procedure a novel and powerful tool in
the monitorization of the dispersion of heavy metals in areas populated by Quercus suber, as it is the case
of big areas in Portugal, the great of the greatest in everything related with this tree, namely
economically, and, in general, in the area of the Mediterranean basin. This paper announces how the
electroanalytical determination of Pb(II) by Differential Pulse Anodic Stripping Voltammetry (DPASV),
recently done in the Department of Chemistry of the University of Évora, already accepted for publication
in Portugaliae Electrochimica Acta, has proven to allow a deeper insight into the previously discussed
problematic
Endovascular Therapy of Pseudoaneurysm and Arteriovenous Fistula in a Renal Graft
A 31 year old male Caucasian received a
renal cadaveric allograft. Reconstruction of an inferior polar artery was corrected pre-implantation. Delayed graft function occurred leading to dialysis support for one month. Graft biopsies(days 7, 15) showed acute tubular necrosis(ATN) and no rejection. Serial ultrasound (US), performed on average weekly, were compatible with ATN. On day 31, Doppler US and a CAT scan suggested for the first time a
pseudoaneurysm adjacent to the implantation
of the graft artery on the external iliac artery. For clinical and technical reasons, arteriography was only performed on day 67, when serum creatinine was 3.3 mg/dl. It showed a large pseudoaneurysm with an arteriovenous fistula to the right common iliac vein. Compression of the right external iliac artery was clear. In an attempt to close the arteriovenous fistula, the communication with the pseudoaneurysm was
embolised with gelfoam and metallic coils with partial success. One week later, by right femoral approach a covered wallstent was placed immediately below the origin of the graft artery.Subsequent Doppler US and arteriography con-firmed closure of the communication with thepseudoaneurysm and of the arteriovenous fistula. The calibre of the right external iliac artery was then normal. By month 18, serum creatinine is stable at 2.1 mg/dl.
We can only speculate on the origin of thepseudoaneurysm and of the AV fistula, whichwere not evident until one month post-transplantation. Backtable surgery was performed on thepolar not the main graft artery. Invasive angiography was irreplaceable in this unusual clinical situation
Melhoramento e manejo de pastagens na Ilha de Marajó: resultados e informações práticas.
bitstream/item/60052/1/Miscelanea-6.pd
Elementos limitantes à produção de pastagens nativas consorciadas com leguminosas na Ilha de Marajó.
bitstream/item/32036/1/CPATU-BP119.pd
Avaliação da adubação nitrogenada em rebrota de sorgo forrageiro na região central de Minas Gerais.
A cortiça como sonda ambiental de metais pesados – um serviço sócio-ambiental prestado por montados de sobro e sobreirais
A longevidade do sobreiro e a capacidade que a cortiça amadia tem de crescer construindo camadas anuais extremamente bem individualizáveis permitiu criar a hipótese de correlação entre as marcas químicas deixadas em cada camada de crescimento e as características ambientais do local onde o sobreiro vegeta. Isto permitiria a construção de séries de novénios de distribuição espacial e temporal da característica que se pretenda estudar. Há nisto algumas semelhanças com abordagens dendrométricas, sendo que estas tendem a ser muito mais agressivas. Foi objectivo deste trabalho que numa fase inicial do estudo se procedesse à criação de uma maneira credível de fazer a quantificação de chumbo (II) no felema da cortiça recorrendo a uma técnica de análise química nunca antes utilizada para este efeito – a voltametria. A escolha deste método da análise química moderna resulta do conhecimento das vantagens competitivas que tem sobre outros, quando aquele é aplicável, como se demonstra ser o caso. A metodologia utilizada começou por exigir a recolha de uma porção de cortiça de um sobreiro escolhido ao acaso, de maneira a encontrar o material cortiça como se encontra na árvore. No momento não se consideram possíveis correlações biogeográficas mas tão somente o material propriamente dito. Tendo sido possível fazer a quantificação indicada, estão em curso os estudos necessários à verificação da hipótese que dá o mote a este trabalho de investigação centrado no sobreiro do montado e do sobreiral, sendo que a principal conclusão a retirar é que a possibilidade de utilização do sobreiro como indicador da qualidade ambiental do local, neste caso quanto ao teor em Pb(II), é mais um serviço prestável (pelo ecossistema que orbita em torno do sobreiro) às populações humanas da área da bacia mediterrânica ocidental. O futuro uso da voltametria como forma de, determinando a concentração do metal em causa em cada camada da cortiça de sobreiros dispersos na área onde vegetam, poder obter-se uma estimativa dos teores médios desses metais nos locais frequentemente caracterizados pela presença daquela árvore, poderá vir a ser muito interessante para um conhecimento mais profundo desta realidade
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