The Hubbard model on a complete graph: exact analytical results

We derive the analytical expression of the ground state of the Hubbard model with unconstrained hopping at half filling and for arbitrary lattice sites.     

Fuzzy logic, continuity and effectiveness

 It is shown the complete equivalence between the theory of continuous (enumeration) fuzzy closure operators and the theory of (effective) fuzzy deduction systems in Hilbert style. Moreover, it is proven that any truth-functional semantics whose connectives are interpreted in [0,1] by continuous functions is axiomatizable by a fuzzy deduction system (but not by an effective fuzzy deduction system, in general). Received: 15 February 2001 / Revised version: 31 May 2001 / Published online: 12 July 2002     

On {J^{PC}=0^{--}} exotic glueball

The mass spectrum of the gluonium with \({J^{PC}=0^{--}}\) is examined in three bottom-up AdS/QCD models. The results are used to identify several production and decay modes useful for searching this state. Moreover, the properties of such glueball in a hot and dense quark medium are discussed.     

A reliable high-performance liquid chromatography with ultraviolet detection for the determination of sulfonamides in honey

The sulfonamides are stable chemotherapeutics used against the bacterial disease affecting bees, known as American foulbrood (Bacillus larvae), so their residues could appear in the honey of treated bees. Their presence at a concentration above the limit value is a potential hazard to human health. Brazilian authorities have included in the National regulatory monitoring program, the control of the three most widely used sulfonamides in honey production, i.e., sulfathiazole, sulfamethazine and sulfadimethoxine. A method for the determination of residual sulfonamides in honey, using sulfapyridine as an internal standard has been developed, optimized and validated. Some changes were implemented on current available methodologies for the analysis of sulfonamides in honey in order to adopt such procedures to Brazilian honey samples. Sulfonamides were extracted from honey with dichloromethane after dissolution with 30% sodium chloride, and cleaned up with solid phase extraction on Florisil columns. The eluate was analyzed by high-performance liquid chromatography with ultraviolet detection. The limit of detection was determined at 3 μg kg⁻¹, 4 μg kg⁻¹ and 5 μg kg⁻¹ for sulfathiazole, sulfamethazine and sulfadimethoxine, respectively with average recoveries of 61.0% for sulfathiazole; 94.5% for sulfamethazine and 86.0% for sulfadimethoxine at the 100 μg kg⁻¹ level. As the final step of validation procedure, the analysts were submitted to a blind spiked sample prepared by the quality assurance officer which results were successfully obtained regarding recovery and deviations.     

A novel palladium-catalyzed dicarbonylation process leading to coumarins

A novel approach to coumarin derivatives has been developed starting from readily available 2-(1-hydroxyprop-2-ynyl)phenols, based on an unprecedented palladium-catalyzed dicarbonylation process. Reactions were carried out in the presence of catalytic amounts of PdI2 in conjunction with an excess of KI in MeOH as the solvent at room temperature and under 90 atm of CO to give 3-[(methoxycarbonyl)methyl]coumarins in good to high isolated yields (62-87%).     

Structural, photophysical, and photochemical characterization of 9-anthracenecarboxylate-hydrotalcite nanocomposites: evidence of a reversible light-driven reaction

ZnAl hydrotalcites containing increasing amounts of 9-anthracenecarboxylate anion (9AC) have been obtained via an anion-exchange procedure. In particular, intercalated and/or surface-exchanged samples were prepared to study the effect of the chromophore packing on their photophysical and photochemical behavior. Surface-exchanged samples were obtained by equilibrating the carbonate form of the ZnAl hydrotalcite with dilute solutions of 9AC. The nitrate form of the ZnAl hydrotalcite was instead chosen for the preparation of intercalation compounds. The maximum loading of 9AC was found to be 44% of the anion-exchange capacity. The obtained nanostructured materials were characterized by chemical and thermal analysis and X-ray powder diffractometry and studied for their photophysical and photochemical properties. The absorption and emission spectra of the materials revealed the formation of 9AC aggregates. The time-resolved fluorescence properties of the hybrid materials were investigated in bulk and under space-resolved conditions. The fluorescence decays appeared to be quite complex and were affected by the microenvironment and the experimental conditions. Generally, a shortening of the main fluorescence decay component was observed with increasing matrix loading, thus suggesting the occurrence of nonradiative processes in competition with fluorescence at high chromophore concentrations. Indeed, the occurrence of an electron-transfer process to water molecules, which led to the formation of 9AC radical, was observed spectrophotometrically in the sample with high 9AC loading. The electron-transfer process was completely reversible under air-equilibrated conditions.     

Secondary metabolism of olive secoiridoids. New microcomponents detected in drupes by electrospray ionization and high-resolution tandem mass spectrometry

Olive drupe tissues have been selected as a possible source of information about the secondary metabolism of oleaceae secoiridoids. The structures of a number of new microcomponents, detected and isolated by a combined high-performance liquid chromatography (HPLC)-fraction collector/ultraviolet electrospray ionization mass spectrometry (UV/ESI-MS) apparatus, can be inferred from the data obtained by high-resolution tandem mass spectrometry in a QqTOF instrument. Some of them (1, 2, 3 and 4) are closely correlated to oleuropein. Others, such as neo-nuzhenide (5) and 2'-hydroxyoleuropein (6), typical of other oleaceae families, have never been found in olive tissues.     

The role of an integration identity in the analysis of the Cauchy-Leray transform

The purpose of this paper is to complement the results by Lanzani and Stein(2017) by showing the dense definability of the Cauchy-Leray transform for the domains that give the counter-examples of Lanzani and Stein(2017), where L~p-boundedness is shown to fail when either the "near" C~2 boundary regularity, or the strong C-linear convexity assumption is dropped.     

On Nested Chain Decompositions of Normalized Matching Posets of Rank 3

In 1975, J. Griggs conjectured that a normalized matching rank-unimodal poset possesses a nested chain decomposition. This elegant conjecture remains open even for posets of rank 3. Recently, Hsu, Logan, and Shahriari have made progress by developing techniques that produce nested chain decompositions for posets with certain rank numbers. As a demonstration of their methods, they prove that the conjecture is true for all rank 3 posets of width at most 7. In this paper, we present new general techniques for creating nested chain decompositions, and, as a corollary, we demonstrate the validity of the conjecture for all rank 3 posets of width at most 11.