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Search Results: 1 - 10 of 457217 matches for " J. R.;Prado-Franceschi "
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Journal of Venomous Animals and Toxins , 2002, DOI: 10.1590/S0104-79302002000100008
Abstract: snake venoms frequently vary in composition. in this work, we compared the neurotoxic and myotoxic activities of 16 lots of bothrops neuwiedii venoms from different regions of brazil, using chick biventer cervicis preparations. the neuromuscular blockade varied from 2% to 100% after 120 min incubation with venoms (50 mg/ml). in all cases, this blockade was irreversible and concentration-dependent; at low concentrations (10-20 mg/ml), 15 of the 16 venom lots failed to abolish responses to acetylcholine (110 mm), but blocked responses to kcl (13.4 mm), and induced contracture. at 5-20 mg/ml, the most active venom totally blocked twitch-tension without affecting responses to acetylcholine and kcl. polyacrylamide gel electrophoresis for basic proteins showed that the most active samples contained a band that was absent in the less active venoms. these results indicate that there may be considerable intraspecific variation in the neurotoxic activity of b. neuwiedii venoms, whereas myotoxic activity is less variable.
Rabbit antivenom efficacy against myotoxic and neurotoxic activities of Bothrops jararacussu venom and bothropstoxin-I
Oshima-Franco, Y.;Leite, G. B.;Valério, A. A.;Hyslop, S.;Andriao-Escarso, S.;Giglio, J. R.;Prado-Franceschi, J.;Cruz-H?fling, M. A.;Rodrigues-Simioni, L.;
Journal of Venomous Animals and Toxins , 2002, DOI: 10.1590/S0104-79302002000200004
Abstract: bothrops jararacussu venom and its major toxin bothropstoxin-i (bthtx-i) possess myotoxic and neurotoxic properties. the efficacy of a rabbit antivenom raised against b. jararacussu venom in the neutralization of physiological, biochemical, and morphological changes induced by the venom and its major toxin bthtx-i was studied in mouse isolated phrenic nerve-diaphragm (pnd) and extensor digitorum longus (edl) preparations. the times required for 50% neuromuscular blockade in pnd and edl preparations for venom were 70+11.5 (s.e.m., n=5) min and 58+8 (n=16) (50 m g/ml), and for bthtx-i 31+6 (n=3) min and 30+3 (n=5) min (20 m g/ml), respectively. after 120 min incubation, creatine kinase (ck) concentrations in solution containing the edl preparations were 3464+346 u/l after exposure to venom (50 m g/ml, n=5) and 3422+135 u/l to bthtx-i (20m g/ml, n=4), respectively. rabbit antivenom dose-dependently neutralized venom and toxin-induced neuromuscular blockade in both preparations and effectively prevented venom and toxin-induced ck release from edl. histological analysis showed that rabbit antivenom neutralized morphological damage caused by b. jararacussu venom and bthtx-i in edl preparations. these results indicate that rabbit antivenom effectively neutralized the biological activities of b. jararacussu venom and bthtx-i.
J. Prado-Franceschi,C.A. Flores,S.E. Moreno,J.C. Cogo
Journal of Venomous Animals and Toxins , 1997, DOI: 10.1590/s0104-79301997000200011
Electrical control of g-factors in a few-hole silicon nanowire MOSFET
B. Voisin,R. Maurand,S. Barraud,M. Vinet,X. Jehl,M. Sanquer,J. Renard,S. De Franceschi
Physics , 2015, DOI: 10.1021/acs.nanolett.5b02920
Abstract: Hole spins in silicon represent a promising yet barely explored direction for solid-state quantum computation, possibly combining long spin coherence, resulting from a reduced hyperfine interaction, and fast electrically driven qubit manipulation. Here we show that a silicon-nanowire field-effect transistor based on state-of-the-art silicon-on-insulator technology can be operated as a few-hole quantum dot. A detailed magnetotransport study of the first accessible hole reveals a g-factor with unexpectedly strong anisotropy and gate dependence. We infer that these two characteristics could enable an electrically-driven g-tensor-modulation spin resonance with Rabi frequencies exceeding several hundred MHz.
Kondo effect out of equilibrium in a mesoscopic device
S. De Franceschi,R. Hanson,W. G. van der Wiel,J. M. Elzerman,J. J. Wijpkema,T. Fujisawa,S. Tarucha,L. P. Kouwenhoven
Physics , 2002,
Abstract: We study the non-equilibrium regime of the Kondo effect in a quantum dot laterally coupled to a narrow wire. We observe a split Kondo resonance when a finite bias voltage is imposed across the wire. The splitting is attributed to the creation of a double-step Fermi distribution function in the wire. Kondo correlations are strongly suppressed when the voltage across the wire exceeds the Kondo temperature. A perpendicular magnetic field enables us to selectively control the coupling between the dot and the two Fermi seas in the wire. Already at fields of order 0.1 T only the Kondo resonance associated with the strongly coupled reservoir survives.
El bosque del escarpe occidental del rio Parana (Argentina): composicion floristica y estructura
Prado, Darién E;Franceschi, Eduardo A;Bianchi, Marta B;
Acta Botanica Brasilica , 1989, DOI: 10.1590/S0102-33061989000300010
Abstract: the western limit of the alluvial plains of the river parana in argentina presents a pronounced scarp, above the level of floodings. the vegetation, a semideciduos subtropical forest of amazonian origin, was analyzed using the point-centred quarter method. the parameters relative frequency, relative density, relative dominance and importance value index for each species are provided, together with a brief structural description. the floristic composition is compared with similar forests elsewhere in argentina and brazil.
Avalia??o preliminar da atividade antimicrobiana do extrato de erva-mate (Ilex paraguariensis A. St. - Hil.) obtido por extra??o com CO2 supercrítico
Carelli, G;Macedo, S.M.D;Valduga, A.T;Corazza, M.L;Oliveira, J.V;Franceschi, E;Vidal, R;Jaskulski, M.R;
Revista Brasileira de Plantas Medicinais , 2011, DOI: 10.1590/S1516-05722011000100016
Abstract: ilex paraguariensis a. st. - hil. ("erva mate") is a tree of the aquifoliaceae family, native to the south region of south america and of great cultural and economic importance for the three states of the south region of brazil. the present study aimed to determine the antimicrobial potential of "erva mate" extract obtained by supercritical fluid against some microorganism strains. the leaves of ilex paraguariensis were collected in the north region of rio grande do sul state. the crude extract of dehydrated plant was obtained by supercritical fluid extraction, using carbon dioxide (co2) as solvent. the extract mother solution (100 mg ml-1) was diluted (50; 25; 12, 5; 6.25 mg ml-1) for antimicrobial activity evaluation, by means of disk diffusion method on müeller-hinton agar, against strains of acinetobacter baumannii (atcc 19606), escherichia coli (atcc 25922), pseudomonas aeruginosa (atcc 27853), staphylococcus aureus (atcc 25923) and enterococcus faecalis (atcc 29212). the analyses were done in triplicate, using as negative control sterile disk without impregnation and as positive control, commercial antibiotic disks according to the bacterial species. after 16-24h incubation at 35oc, the diameters of inhibition zones were measured. antimicrobial activity was observed against s. aureus (inhibition zones between 7 and 18 mm) and p. aeruginosa (inhibition zones between 6 and 11 mm), both at the concentrations of 100 mg ml-1 to 25 mg ml-1. the extract of ilex paraguariensis obtained by supercritical fluid presented antimicrobial activity against s. aureus and p. aeruginosa.
Quantum Computing with Electron Spins in Quantum Dots
L. M. K. Vandersypen,R. Hanson,L. H. Willems van Beveren,J. M. Elzerman,J. S. Greidanus,S. De Franceschi,L. P. Kouwenhoven
Physics , 2002,
Abstract: We present a set of concrete and realistic ideas for the implementation of a small-scale quantum computer using electron spins in lateral GaAs/AlGaAs quantum dots. Initialization is based on leads in the quantum Hall regime with tunable spin-polarization. Read-out hinges on spin-to-charge conversion via spin-selective tunneling to or from the leads, followed by measurement of the number of electron charges on the dot via a charge detector. Single-qubit manipulation relies on a microfabricated wire located close to the quantum dot, and two-qubit interactions are controlled via the tunnel barrier connecting the respective quantum dots. Based on these ideas, we have begun a series of experiments in order to demonstrate unitary control and to measure the coherence time of individual electron spins in quantum dots.
Few-Electron Quantum Dot Circuit with Integrated Charge Read-Out
J. M. Elzerman,R. Hanson,J. S. Greidanus,L. H. Willems van Beveren,S. De Franceschi,L. M. K. Vandersypen,S. Tarucha,L. P. Kouwenhoven
Physics , 2002, DOI: 10.1103/PhysRevB.67.161308
Abstract: We report on the realization of a few-electron double quantum dot defined in a two-dimensional electron gas by means of surface gates on top of a GaAs/AlGaAs heterostructure. Two quantum point contacts (QPCs) are placed in the vicinity of the double quantum dot and serve as charge detectors. These enable determination of the number of conduction electrons on each dot. This number can be reduced to zero while still allowing transport measurements through the double dot. Microwave radiation is used to pump an electron from one dot to the other by absorption of a single photon. The experiments demonstrate that this quantum dot circuit can serve as a good starting point for a scalable spin-qubit system.
Applying boron to coconut palm plants: effects on the soil, on the plant nutritional status and on productivity boron to coconut palm trees
J. Z Moura,R.M Prado,R.N Benvindo,L Chaves Alencar
Journal of Soil Science and Plant Nutrition , 2013,
Abstract: Boron, one of the micronutrients frequently found in low levels in tropical soils affects nutrition and productivity of coconut palm trees essentially cultivated in tropical climates. The objective of this research study was to evaluate the effect of boron on the nutritional status of the plant and its productivity when artificially applied to the culture soil. The experiment was carried out in a four year old, artificially irrigated, dwarf coconut palm orchard in Brazil, between January, 2005 and October, 2006. The soil was a red yellow Latosol (B: 0.18 mg dm-3). The treatments consisted in the application of five boron dosages: zero, 1, 2, 4, and 6 kg ha-1. In the field, the treatments were arranged according to a completely randomized block design, with four replications. Boron (borax) dosages were applied in equal halves directly into the soil in the months of January and February of 2005. Boron concentration in the soil and plant and plant productivity were evaluated. The higher palm tree production was associated to levels of 0.6mg dm-3 of B in the soil and 23.5mg kg-1 in leaves. Ninety five percent of palm trees maximum production was obtained with the use of a boron dosage of 2,1kg ha-1.
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