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Search Results: 1 - 10 of 677747 matches for " E. A. N. Simonetti "
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Ca-Al Hydrotalcites as Catalysts for Methanolysis and Ethanolysis of Soybean Oil  [PDF]
E. A. N. Simonetti, G. P. Thim, G. G. Cortez
Modern Research in Catalysis (MRC) , 2014, DOI: 10.4236/mrc.2014.34015
Abstract: The use of heterogeneous catalysts in the transesterification reaction of vegetable oils has getting emphasis in recent years, mainly by the alternative of obtaining clean fuel derived from renewable sources. Metal oxide such as MgO or CaO, supported ones like \"\" and zeolites are often applied in transesterification process. Among them, hydrotalcite has shown potential as catalysts on this reaction due to their physicochemical properties, such as: thermal stability, porosity, specific surface area, memory effect, basicity, acidity and anion exchange capacity. This work studies the catalytic performance of the calcium and aluminum based hydrotalcite in the transesterification reaction of soybean oil in methanol and ethanol. The hydrotalcite samples treated at 450?C were impregnated with KOH. The efficiency of impregnated and non- impregnated samples was compared and the non-impregnated one showed the best performance. This property was attributed to the higher availability of active sites used in the transesterification process.
Denied density-dependent seedling recruitment in a fragmented forest does not decrease seedling diversity
VALDIVIA,CARLOS E; SIMONETTI,JAVIER A;
Revista chilena de historia natural , 2011, DOI: 10.4067/S0716-078X2011000200012
Abstract: negative density-dependent relationships in plant communities are currently claimed as an important mechanism for the maintenance of plant diversity. however, anthropogenic perturbations such as forest fragmentation might modify such relationships. we evaluated density-dependent relationships between seed and seedling abundance of a tree assemblage in a fragmented forest for estimating seed-to-seedling transitions and their effects on seedling richness. in continuous forest, two out of four and one out of four species presented significant or a tendency to exhibit negative seedling recruitment which is in agreement with other temperate and tropical forests. in forest fragments (1-6 ha), however, this relationship was uncoupled. seedling richness and diversity, assessed through shannon-wiener index, did not differ between both types of sites. therefore, forest fragmentation negatively affected seedling recruitment by uncoupling seed-to-seedling transitions, but not by diminishing seedling diversity. this leads to considering the role of density-dependent relationships for the maintenance of plant diversity in communities and claims for including forest fragments into conservation programmes.
Denied density-dependent seedling recruitment in a fragmented forest does not decrease seedling diversity El denegado reclutamiento denso-dependiente de plántulas en un bosque fragmentado no disminuye la diversidad de plántulas
CARLOS E VALDIVIA,JAVIER A SIMONETTI
Revista chilena de historia natural , 2011,
Abstract: Negative density-dependent relationships in plant communities are currently claimed as an important mechanism for the maintenance of plant diversity. However, anthropogenic perturbations such as forest fragmentation might modify such relationships. We evaluated density-dependent relationships between seed and seedling abundance of a tree assemblage in a fragmented forest for estimating seed-to-seedling transitions and their effects on seedling richness. In continuous forest, two out of four and one out of four species presented significant or a tendency to exhibit negative seedling recruitment which is in agreement with other temperate and tropical forests. In forest fragments (1-6 ha), however, this relationship was uncoupled. Seedling richness and diversity, assessed through Shannon-Wiener Index, did not differ between both types of sites. Therefore, forest fragmentation negatively affected seedling recruitment by uncoupling seed-to-seedling transitions, but not by diminishing seedling diversity. This leads to considering the role of density-dependent relationships for the maintenance of plant diversity in communities and claims for including forest fragments into conservation programmes. Las relaciones denso-dependientes negativas en las comunidades vegetales son actualmente se aladas como un importante mecanismo para la mantención de la diversidad de plantas. Sin embargo, las perturbaciones antropogénicas como la fragmentación del bosque podrían modificar este tipo de relaciones. Evaluamos las relaciones denso-dependientes entre las abundancias de semillas y plántulas en un ensamble de árboles en un bosque fragmentado para estimar las transiciones de semillas a plántulas y sus efectos sobre la riqueza de plántulas. En el bosque continuo tres de cuatro especies presentaron reclutamientos de plántulas negativos, lo cual se condice con otros bosques templados y tropicales. En los fragmentos de bosque (1-6 ha), no obstante, estas relaciones estuvieron desacopladas. La riqueza y diversidad de plántulas, evaluadas a través del índice de Shannon-Wiener, no difirió entre ambos tipos de sitios. Por lo tanto, la fragmentación del bosque afectó negativamente el reclutamiento de plántulas modificando las transiciones de semilla a plántula, pero no disminuyendo la diversidad de plántulas. Este resultado nos conduce a considerar el rol de las relaciones denso-dependientes en la mantención de la diversidad de plántulas en las comunidades y aboga por incluir los fragmentos de bosque en los programas de conservación.
First determination of the one-proton induced Non-Mesonic Weak Decay width of p-shell Λ-Hypernuclei
M. Agnello,L. Benussi,M. Bertani,H. C. Bhang,G. Bonomi,E. Botta,T. Bressani,S. Bufalino,D. Calvo,P. Camerini,B. Dalena,F. De Mori,G. D Erasmo,A. Feliciello,A. Filippi,H. Fujioka,P. Gianotti,N. Grion,V. Lucherini,S. Marcello,T. Nagae,H. Outa,V. Paticchio,S. Piano,R. Rui,G. Simonetti,A. Zenoni
Physics , 2014, DOI: 10.1016/j.physletb.2014.10.024
Abstract: Previous studies of proton and neutron spectra from Non-Mesonic Weak Decay of eight Lambda-Hypernuclei (A = 5-16) have been revisited. New values of the ratio of the two-nucleon and the one-proton induced decay widths, Gamma_2N/Gamma_p, are obtained from single proton spectra, Gamma_2N/Gamma_p = 0.50 +/- 0.24, and from neutron and proton coincidence spectra, Gamma_2N/Gamma_p = 0.36 +/- 0.14stat +0.05sys -0.04sys , in full agreement with previously published ones. With these values, a method is developed to extract the one-proton induced decay width in units of the free Lambda decay width, Gamma_p/Gamma_Lambda, without resorting to Intra Nuclear Cascade models but by exploiting only experimental data, under the assumption of a linear dependence on A of the Final State Interaction contribution. This is the first systematic determination ever done and it agrees within the errors with recent theoretical calculations.
First observation of the hyper superheavy hydrogen 6ΛH
M. Agnello,L. Benussi,M. Bertani,H. C. Bhang,G. Bonomi,E. Botta,M. Bregant,T. Bressani,S. Bufalino,L. Busso,D. Calvo,P. Camerini,B. Dalena,F. De Mori,G. D'Erasmo,F. L. Fabbri,A. Feliciello,A. Filippi,E. M. Fiore,A. Fontana,H. Fujioka,P. Genova,P. Gianotti,N. Grion,V. Lucherini,S. Marcello,N. Mirfakhrai,F. Moia,O. Morra,T. Nagae,H. Outa,A. Pantaleo,V. Paticchio,S. Piano,R. Rui,G. Simonetti,R. Wheadon,A. Zenoni,A. Gal
Physics , 2012, DOI: 10.1016/j.nuclphysa.2012.02.015
Abstract: Three candidate events of the neutron-rich hypernucleus 6{\Lambda}H were uniquely identified in the FINUDA experiment at DA{\Phi}NE, Frascati, by observing {\pi}+ mesons from the (K-stop,{\pi}+) production reaction on 6Li targets, in coincidence with {\pi}-mesons from 6{\Lambda}H \rightarrow 6He+{\pi}- weak decay. Details of the experiment and the analysis of its data are reported, leading to an estimate of (2.9\pm2.0)\cdot10-6/K- stop for the 6{\Lambda}H production rate times the two-body {\pi}- weak decay branching ratio. The 6{\Lambda}H binding energy with respect to 5H + {\Lambda} was determined jointly from production and decay to be B{\Lambda} = (4.0 \pm 1.1) MeV, assuming that 5H is unbound with respect to 3H + 2n by 1.7 MeV. The binding energy determined from production is higher, in each one of the three events, than that determined from decay, with a difference of (0.98 \pm 0.74) MeV here assigned to the 0+g.s. \rightarrow 1+ excitation. The consequences of this assignment to {\Lambda} hypernuclear dynamics are briefly discussed.
Evidence for 6ΛH
M. Agnello,L. Benussi,M. Bertani,H. C. Bhang,G. Bonomi,E. Botta,M. Bregant,T. Bressani,S. Bufalino,L. Busso,D. Calvo,P. Camerini,B. Dalena,F. De Mori,G. D'Erasmo,F. L. Fabbri,A. Feliciello,A. Filippi,E. M. Fiore,A. Fontana,H. Fujioka,P. Genova,P. Gianotti,N. Grion,V. Lucherini,S. Marcello,N. Mirfakhrai,F. Moia,O. Morra,T. Nagae,H. Outa,A. Pantaleo,V. Paticchio,S. Piano,R. Rui,G. Simonetti,R. Wheadon,A. Zenoni,A. Gal
Physics , 2011, DOI: 10.1103/PhysRevLett.108.042501
Abstract: Evidence for the neutron-rich hypernucleus 6{\Lambda}H is presented from the FINUDA experiment at DA{\Phi}NE, Frascati, studying ({\pi}+, {\pi}-) pairs in coincidence from the K- +6Li \rightarrow 6 H+{\pi}+ production reaction followed by 6{\Lambda}H \rightarrow 6He + {\pi}- weak decay. The production rate of 6{\Lambda}H undergoing this two-body {\pi}- decay is determined to be (2.9\pm2.0)\cdot10-6/K-. Its binding energy, evaluated jointly from production and decay, is B{\Lambda}(6{\Lambda}H) = (4.0\pm1.1) MeV with respect to 5H+{\Lambda}. A systematic difference of (0.98 \pm 0.74) MeV between B{\Lambda} values derived separately from decay and from production is tentatively assigned to the 6{\Lambda}H 0+g.s. \rightarrow 1+ excitation.
Search for the neutron-rich hypernucleus 9ΛHe
M. Agnello,L. Benussi,M. Bertani,H. C. Bhang,G. Bonomi,E. Botta,M. Bregant,T. Bressani,S. Bufalino,L. Busso,D. Calvo,P. Camerini,B. Dalena,F. De Mori,G. D Erasmo,F. L. Fabbri,A. Feliciello,A. Filippi,E. M. Fiore,A. Fontana,H. Fujioka,P. Genova,P. Gianotti,N. Grion,V. Lucherini,S. Marcello,N. Mirfakhrai,F. Moia,O. Morra,T. Nagae,H. Outa,A. Pantaleo,V. Paticchio,S. Piano,R. Rui,G. Simonetti,R. Wheadon A. Zenoni,A. Gal
Physics , 2012, DOI: 10.1103/PhysRevC.86.057301
Abstract: Search for the neutron-rich hypernucleus 9LHe is reported by the FINUDA experiment at DAFNE, INFN-LNF, studying (pi+, pi-) pairs in coincidence from the K-stop + 9Be --> 9LHe + pi+ production reaction followed by 9LHe --> 9Li + pi- weak decay. An upper limit of the production rate of 9LHe undergoing this two-body pi- decay is determined to be (2.3 +/- 1.9) 10-6/K-stop at 90% confidence level.
Study of some two-body non-mesonic decays of $^4_Λ$He and $^5_Λ$He
FINUDA Collaboration,M. Agnello,L. Benussi,M. Bertani,H. C. Bhang,G. Bonomi,E. Botta,M. Bregant,T. Bressani,S. Bufalino,L. Busso,D. Calvo,P. Camerini,B. Dalena,F. De Mori,G. D'Erasmo,F. L. Fabbri,A. Feliciello,A. Filippi,E. M. Fiore,A. Fontana,H. Fujioka,P. Genova,P. Gianotti,N. Grion,V. Lucherini,S. Marcello,N. Mirfakhrai,F. Moia,O. Morra,T. Nagae,H. Outa,A. Pantaleo,V. Paticchio,S. Piano,R. Rui,G. Simonetti,R. Wheadon,A. Zenoni
Physics , 2010,
Abstract: The Non-Mesonic (NM) decay of $^4_\Lambda{\mathrm{He}}$ and $^5_\Lambda{\mathrm{He}}$ in two-body channels has been studied by the FINUDA Collaboration. Two-body NM decays of hypernuclei are rare and the existing observations and theoretical calculations are scarce. The $^4_\Lambda{\mathrm{He}}\rightarrow d+d,\; p+t$ decay channels simultaneously observed by FINUDA on several nuclei are compared: the $pt$ channel is the dominant one. The decay yields for the two decay channels are assessed for the first time: they are $(1.37\pm 0.37)\times 10^{-5}/K^-_{stop}$ and $(8.3\pm 1.0)\times 10^{-5}/K^-_{stop}$, respectively. Due to the capability of FINUDA of identifying $^5_\Lambda{\mathrm{He}}$ hypernuclei, a few $^5_\Lambda{\mathrm{He}}\rightarrow d+t$ decay events have also been observed. The branching ratio for this decay channel has been measured for the first time: $(3.0\pm 2.3)\times 10^{-3}$.
Direct experimental evidence of the weak $Λn p \rightarrow n n p$ hypernucleus decay
M. Agnello,L. Benussi,M. Bertani,H. C. Bhang,G. Bonomi,E. Botta,M. Bregant,T. Bressani,S. Bufalino,L. Busso,D. Calvo,P. Camerini,B. Dalena,F. De Mori,G. D'Erasmo,F. L. Fabbri,A. Feliciello,A. Filippi,E. M. Fiore,A. Fontana,H. Fujioka,P. Genova,P. Gianotti,N. Grion,V. Lucherini,S. Marcello,N. Mirfakhrai,F. Moia,O. Morra,T. Nagae,H. Outa,A. Pantaleo,V. Paticchio,S. Paino,R. Rui,G. Simonetti,R. Wheadon,A. Zenoni
Physics , 2011,
Abstract: A direct experimental evidence of the occurrence of the weak reaction $\Lambda np\rightarrow nnp$ in nuclei has been obtained by the FINUDA experiment. Three events have been found that can be attributed to $^{7}_{\Lambda}$Li and $^{9}_{\Lambda}$Be two nucleon-induced non mesonic weak decays. The kinematic analysis of such events is presented here.
An improved determination of the two--nucleon induced non mesonic weak decay of $Λ$-hypernuclei
M. Agnello,L. Benussi,M. Bertani,H. C. Bhang,G. Bonomi,E. Botta,M. Bregant,T. Bressani,S. Bufalino,L. Busso,D. Calvo,P. Camerini,B. Dalena,F. De mori,G. D'erasmo,F. L. Fabbri,A. Feliciello,A. Filippi,E. M. Fiore,H. Fujioka,P. Genova,P. Gianotti,N. Grion,V. Lucherini,S. Marcello,N. Mirfakhrai,F. Moia,P. Montagna,O. Morra,T. Nagae,H. Outa,A. Pantaleo,V. Paticchio,S. Piano,R. Rui,G. Simonetti,R. Wheadon,A. Zenoni,G. Garbarino
Physics , 2011,
Abstract: The decay of $\Lambda$-hypernuclei without pion emission, known as Non Mesonic Weak Decay (NMWD), gives an effective tool to investigate $\Delta$S=1 four-baryon interactions. It was theoretically suggested that the two-nucleon induced mechanism could play a substantial role in reproducing the observed NMWD decay rates and nucleon spectra, but at present no direct evidence of such a mechanism has been obtained. The FINUDA experiment, exploiting the possibility to detect both charged and neutral particles coming from the hypernucleus decay, has allowed us to deduce the relative weight of the two nucleon induced decay rate to the total NMWD rate. The value of $\Gamma_{2N}$/$\Gamma_{NMWD}$=0.24$\pm$${0.03_{stat}}^{+0.03_{sys}}_{{-{0.02_{sys}}}}$ has been deduced, with an error reduced by a factor more than two compared with the previous assessment.
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