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Search Results: 1 - 10 of 223844 matches for " R. Foglio "
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Thermodynamic properties of the periodic Anderson model:X-boson treatment
R. Franco,M. S Figueira,M. E Foglio
Physics , 2003, DOI: 10.1103/PhysRevB.68.205108
Abstract: We study the specific dependence of the periodic Anderson Model (PAM) in the limit of $U=\infty$ employing the X-boson treatment in two fifferent regimes of the PAM: the heavy fermion Kondo (HF-K) and the heavy fermion local magnetic regime (HF-LMM). We obtain a multiple peak structure for the specific heat in agreement with experimental results as well as the increase of the electronic effective mass at low temperatures associated with the HF-K regime. The entropy per site at low T tends to zero in the HF-K regime, corresponding to a singlet ground state, and it tends to $k_{B}ln(2)$ in the HF-LMM, corresponding to a doublet ground state at each site. The linear coefficient $\gamma(T)=C_{v}/T$ of the specific heat qualitatively agrees with the experimental results obtained for differents materials in the two regimes considered here.
Thermodynamic potential of the Periodic Anderson Model with the X-boson method: Chain Approximation
R. Franco,M. S. Figueira,M. E. Foglio
Physics , 2001, DOI: 10.1016/S0378-4371(02)00575-7
Abstract: The Periodic Anderson Model (PAM) in the $U\to\infty$ limit has been studied in a previous work employing the cumulant expansion with the hybridization as perturbation (M. S. Figueira, M. E. Foglio and G. G. Martinez, Phys. Rev. B \textbf{50}, 17933 (1994)). When the total number of electrons $N_{t}$ is calculated as a function of the chemical potential $\mu$ in the ``Chain Approximation'' (CHA), there are three values of the chemical potential $\mu$ for each $N_{t}$ in a small interval of $N_{t}$ at low $T$ (M. S Figueira, M. E Foglio, Physica A 208 (1994)). We have recently introduced the ``X-boson'' method, inspired in the slave boson technique of Coleman, that solves the problem of non conservation of probability (completeness) in the CHA as well as removing the spurious phase transitions that appear with the slave boson method in the mean field approximation. In the present paper we show that the X-boson method solves also the problem of the multiple roots of $N_{t}(\mu)$ that appear in the CHA.
X-boson cumulant approach to the periodic Anderson model
R. Franco,M. S. Figueira,M. E. Foglio
Physics , 2001, DOI: 10.1103/PhysRevB.66.045112
Abstract: The Periodic Anderson Model (PAM) can be studied in the infinite U limit by employing the Hubbard X operators to project out the unwanted states. We have already studied this problem employing the cumulant expansion with the hybridization as perturbation, but the probability conservation of the local states (completeness) is not usually satisfied when partial expansions like the Chain Approximation (CHA) are employed. Here we treat the problem by a technique inspired in the mean field approximation of Coleman's slave-bosons method, and we obtain a description that avoids the unwanted phase transition that appears in the mean-field slave-boson method both when the chemical potential is greater than the localized level Ef at low temperatures (T) and for all parameters at intermediate T.
From the Atomic Systems to the Extended Ones: the Hubbard Operators
Foglio, M. E.;
Brazilian Journal of Physics , 1997, DOI: 10.1590/S0103-97331997000400028
Abstract: it is sometimes convenient to emphasize the local aspects of a part of a crystalline system, and use the corresponding localized states to build a basis of the states of the whole system. in many cases it is only a subspace of these local states that is relevant, and the hubbard operators provide a fairly simple way to write the corresponding projected hamiltonian. two examples of this type of treatment are presented int this work. the first is a co2+ impurity in a mgo crystal interacting through a jahn-teller term with the crystal phonons, and it is shown how this interaction affects the electronic raman scattering. the second is the anderson lattice when the local electrons have an infinite coulomb repulsion, and a diagrammatic expansion with cumulants is discussed. we propose a method to obtain approximate green's functions for the anderson lattice that employs the exact solutions of an atomic problem, and the corresponding spectral density of the local electrons is calculated.
'n Praktiese benadering tot die samestelling van 'n tweerigtingvakwoordeboek met Afrikaans en Italiaans as taalpaar
F de Foglio
Lexikos , 2002,
Abstract: Deur die tempo van globalisering op handelsgebied ontstaan daar toenemend 'n behoefte aan tweerigtingvakwoordeboeke. Afrikaans is een van die hooftale in Suid-Afrika, en die landbousektor van die land is oorwegend Afrikaanssprekend. Aangesien een van die outeurs Italiaanssprekend is, by vertaling betrokke is en die leemte aan 'n tweerigtingvakwoordeboek Afrikaans en Italiaans ervaar het, is kriteria bepaal vir die samestelling van so 'n vakwoordeboek op die gebied van die landbou-ekonomie tussen Afrikaans, 'n Germaanse taal, en Italiaans, 'n Romaanse taal. In agtereenvolgende afdelings word die algemene kriteria vir die samestelling van so 'n woordeboek uiteengesit. Daarbenewens word voorafgaande werk wat verrig moet word, bespreek, asook die keuring van materiaal. Ten slotte word, aan die hand van gepaste voorbeelde, die leksikografiese beginsels toegepas. 'n Bylaag wat uit twintig lemmas bestaan, dien as voorbeeld van hoe so 'n vakwoordeboek daar behoort uit te sien. Sleutelwoorde: afrikaans, italiaans, leksikografie, terminografie, terminologie, tweerigting, tweetalig, vakleksikografie, vakwoordeboek, woordeboek.
From the Atomic Systems to the Extended Ones: the Hubbard Operators
Foglio M. E.
Brazilian Journal of Physics , 1997,
Abstract: It is sometimes convenient to emphasize the local aspects of a part of a crystalline system, and use the corresponding localized states to build a basis of the states of the whole system. In many cases it is only a subspace of these local states that is relevant, and the Hubbard operators provide a fairly simple way to write the corresponding projected Hamiltonian. Two examples of this type of treatment are presented int this work. The first is a Co2+ impurity in a MgO crystal interacting through a Jahn-Teller term with the crystal phonons, and it is shown how this interaction affects the electronic Raman scattering. The second is the Anderson lattice when the local electrons have an infinite Coulomb repulsion, and a diagrammatic expansion with cumulants is discussed. We propose a method to obtain approximate Green's functions for the Anderson lattice that employs the exact solutions of an atomic problem, and the corresponding spectral density of the local electrons is calculated.
In vitro degradation of linamarin by microorganisms isolated from cassava wastewater treatment lagoons
Vasconcellos, S. P;Cereda, M. P.;Cagnon, J. R.;Foglio, M.A.;Rodrigues, R.A.;Manfio, G. P.;Oliveira, V. M.;
Brazilian Journal of Microbiology , 2009, DOI: 10.1590/S1517-83822009000400019
Abstract: this study aimed at isolating and characterizing of microorganisms able to use linamarin as sole carbon source. thirty one microbial strains were isolated from manipueira, a liquid effluent of cassava processing factories. among these strains, bacillus licheniformis (isolate 2_2) and rhodotorulla glutinis (isolate l1) were able to degrade 71% and 95% of added linamarin, respectively, within 7 days, showing high biodegradation activity and great potential for detoxification of cassava processing wastewaters.
Study of Co2+ in different crystal field environments
Foglio, M. E.;Barberis, G. E.;
Brazilian Journal of Physics , 2006, DOI: 10.1590/S0103-97332006000100010
Abstract: we consider the esr of co2+ in different environments: in an regular octahedron (co2+ in a mgo crystal), in a deformed octahedron (co2+ in single crystals and powder samples of nh4nipo4.6h2o) or in a trigonal bipyramid (co2+ in powders of co2(oh)po4 and co2(oh)aso4). we study the effect of the non-cubic crystal fields in the esr of co2+ in the deformed octahedron, by employing the normal modes of this structure to simplify the systematic study of the effect of these fields. a similar study was done for the deformed trigonal bipiramid, and it was necessary to derive the normal modes of this complex that are relevant to our problem.
'n Praktiese benadering tot die samestelling van 'n tweerigtingvakwoordeboek met Afrikaans en Italiaans as taalpaar
F. de Foglio,H.J. Lubbe
Lexikos , 2011, DOI: 10.5788/12--764
Abstract: Opsomming: Deur die tempo van globalisering op handelsgebied ontstaan daar toenemend 'n behoefte aan tweerigtingvakwoordeboeke. Afrikaans is een van die hooftale in Suid-Afrika, en die landbousektor van die land is oorwegend Afrikaanssprekend. Aangesien een van die outeurs Italiaanssprekend is, by vertaling betrokke is en die leemte aan 'n tweerigtingvakwoordeboek Afrikaans en Italiaans ervaar het, is kriteria bepaal vir die samestelling van so 'n vakwoordeboek op die gebied van die landbou-ekonomie tussen Afrikaans, 'n Germaanse taal, en Italiaans, 'n Romaanse taal. In agtereenvolgende afdelings word die algemene kriteria vir die samestelling van so 'n woordeboek uiteengesit. Daarbenewens word voorafgaande werk wat verrig moet word, bespreek, asook die keuring van materiaal. Ten slotte word, aan die hand van gepaste voorbeelde, die leksikografiese beginsels toegepas. 'n Bylaag wat uit twintig lemmas bestaan, dien as voorbeeld van hoe so 'n vakwoordeboek daar behoort uit te sien. Sleutelwoorde: AFRIKAANS, ITALIAANS, LEKSIKOGRAFIE, TERMINOGRAFIE, TERMINOLOGIE, TWEERIGTING, TWEETALIG, VAKLEKSIKOGRAFIE, VAKWOORDEBOEK, WOORDEBOEK. Abstract: A Practical Approach to the Compilation of a Bi-directional Technical Dictionary with Afrikaans and Italian as Language Pair. Due to rapid globalisation in the commercial sphere, there is an ever-increasing need for the compilation of bilingual technical dictionaries. Afrikaans is one of the principal languages in South Africa, and the agricultural sector of the country is predominantly Afrikaans-speaking. Since one of the authors is Italianspeaking, is involved in translation, and has experienced the need for a bi-directional technical dictionary Afrikaans and Italian, criteria were determined for the compiling of such a technical dictionary in the field of agricultural economics between Afrikaans, a Germanic language, and Italian, a Romance language. In subsequent sections, the general criteria for compiling such a dictionary are outlined. In addition, the work that must precede this process is discussed, as is the selection of material. In conclusion, employing appropriate examples, the lexicographical principles are applied. An appendix comprising twenty entries serves as an example of what such a technical dictionary should look like. Keywords: AFRIKAANS, BI-DIRECTIONAL, BILINGUAL, DICTIONARY, ITALIAN, LEXICOGRAPHY, LEXICOGRAPHY FOR SPECIAL PURPOSES, TECHNICAL DICTIONARY, TERMINOGRAPHY, TERMINOLOGY.
Study of Co2+ in different crystal field environments
Foglio M. E.,Barberis G. E.
Brazilian Journal of Physics , 2006,
Abstract: We consider the ESR of Co2+ in different environments: in an regular octahedron (Co2+ in a MgO crystal), in a deformed octahedron (Co2+ in single crystals and powder samples of NH4NiPO4.6H2O) or in a trigonal bipyramid (Co2+ in powders of Co2(OH)PO4 and Co2(OH)AsO4). We study the effect of the non-cubic crystal fields in the ESR of Co2+ in the deformed octahedron, by employing the normal modes of this structure to simplify the systematic study of the effect of these fields. A similar study was done for the deformed trigonal bipiramid, and it was necessary to derive the normal modes of this complex that are relevant to our problem.
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