Structural Characterization of Aniline-Bentonite Composite by FTIR,DTA/TG,and PXRD Analyses and BET Measurement

ABSTRACT

The aniline species incorporated into the acid-activated bentonite matrices leads to the decay of the skeletal stretches centered at 1041 cm^?1 and the rise of new features in the phenyl ring frequency region, 1700–1400 cm^?1, demonstrates clearly the influence of the acid activation on the Lewis sites necessary for coordination of aniline to bentonite. The exothermic DTA features at 507, 684, and 725°C indicate the release of both the clusters and the decomposed fragments of the aniline-clay composite, and the highly stable carbonaceous residue, respectively. The basal difference by ～1.0 nm and the much smaller surface area (33.8 m²/g) than that of the nonintercalated bentonite (129.2 m²/g) prove the presence of the tilted aniline species between the interlamellar grooves of the bentonite framework.     

Complex networks and banking systems supervision

Comprehensive and thorough supervision of all banking institutions under a Central Bank’s regulatory control has become necessary as recent banking crises show. Promptly identifying bank distress and contagion issues is of great importance to the regulators. This paper proposes a methodology that can be used additionally to the standard methods of bank supervision or the new ones proposed to be implemented. By this, one can reveal the degree of banks’ connectedness and thus identify “core” instead of just “big” banks. Core banks are central in the network in the sense that they are shown to be crucial for network supervision. Core banks can be used as gauges of bank distress over a sub-network and promptly raise a red flag so that the central bank can effectively and swiftly focus on the corresponding neighborhood of financial institutions. In this paper we demonstrate the proposed scheme using as an example the asset returns variable. The method may and should be used with alternative variables as well.     

Market efficiency of Brazilian exchange rate: Evidence from variance ratio statistics and technical trading rules

This study utilizes the variance ratio test to examine the behavior of Brazilian exchange rate. We show that adjustments for multiple tests and a bootstrap methodology must be employed in order to avoid size distortions. We propose a block bootstrap scheme and show that it has much nicer properties than the traditional Chow–Denning [Chow, K.V., Denning, K.C., 1993. A simple multiple variance ratio test. Journal of Econometrics 58 (3), 385–401] multiple variance ratio tests. Overall, the method proposed in the paper provides evidence refuting the random walk behavior for the Brazilian exchange rate for long investment horizon, but consistent with the random walk hypothesis for short-run horizon. Additionally, we also test for the predictive power of variable moving average (VMA) and trading range break (TRB) technical rules and find evidence of forecasting ability for these rules. Nonetheless, the excess return that can be obtained from such rules is not significant, suggesting that such predictability is not economically significant.     

Researches on pyrazoles LII. IR Spectra and lactim-lactam tautomerism of pyrazolopyridones

The IR spectra of the previously synthesized pyrazolo[3,4-b]- and pyrazolo [4, 5-b] pyridones are investigated. From analysis of the IR spectra of the pyrazolopyridones themselves, and of complexes with heavy metal salts, as well as of some model compounds, conclusions are drawn regarding their lactam structure.     

Study of the reaction νp → μ+pπ−

We present data on the reaction $\text{ν}\text{p → μ}{}^{\mathrm{+}}\text{pπ}{}^{\mathrm{?}}$ from an exposure of the Fermilab 15 ft hydrogen bubble chamber. The channel cross section for $\text{5}\text{GeV}\text{< E}{}_{\mathrm{<mtext>\nu </mtext>}}\text{< 70}\text{GeV and}\text{M(}\text{p}\text{π}{}^{\mathrm{?}}\text{) < 1.9}\text{GeV is}\text{σ = (27 ± 5) × 10}{}^{\mathrm{?40}}\text{cm}{}^2$. This cross section is dominated by the $\text{I =}\text{1}\text{2}$ production amplitude.     

MeV proton generation and efficiency from an intense laser irradiated foil

The proton energy distribution generated from the interaction of an intense (Iλ² ≈ 10²⁰ W/cm² μm²) short-pulse (100 fs) laser with a thin foil is investigated using energy resolved measurements and 2D collisional PIC-hybrid simulations. The measured absolute proton spectrum is well matched by a 1.7 MeV exponential function for energies <11 MeV. The proton conversion efficiency from hot electrons ≈6%. Simulations predict a strong radial dependence on the maximum proton energy and on the radial extent of 12 Å hydrocarbon depletion region. C and O ions in the hydrocarbon layer gain significant energies, limiting the efficiency to the protons. The efficiency scaling for ion mixtures is derived using a simple model, and is shown to strongly depend on the cooling rate of the hot electrons. Simulations using hydrogen-rich, layered targets predict much higher efficiencies.     

Synthesis,crystal structure,spectroscopy, thermal properties and carbonic anhydrase activities of new metal(II) complexes with mefenamic acid and picoline derivatives

The mononuclear six metal(II) complexes ([Co(mef)₂(3-pic)₂(CH₃OH)₂] (1), [Ni(mef)₂(3-pic)₂(CH₃OH)₂] (2), [Cu(mef)₂(3-pic)₂] (3), [Co(mef)₂(4-pic)₂] (4), [Ni(mef)₂(4-pic)₂] (5), and [Cu(mef)₂(4-pic)₂] (6) with mefenamic acid and picoline ligands were synthesized, characterized, and their carbonic anhydrase inhibitory activities were evaluated. The six complexes were characterized by elemental analysis, FT-IR spectroscopy, and thermal analyses. The crystal structures of 1, 3, and 6 were determined by X-ray crystallography. The complexes have octahedral geometry. In 1, the mefenamato ligand behaved as monodentate whereas in 3 and 6, the mefenamato ligand acted as a bidentate ligand. Complexes 3 and 6 consist of the mefenamate and 4-picoline ligands. In 1, unlike the other complexes, methanol acted as a ligand and was involved in the coordination. Carbonic anhydrase I and II isoenzymes were purified from human erythrocytes. The in vitro effects of mefenamic acid, 3-picoline, 4-picoline, and the six metal(II) complexes on these isoenzymes were evaluated.     

Phenanthroline Cu(II)-bentonite composite characterization

Summary The penetration of the phenanthroline ligand into the interlayer space of the Cu-bentonite results in the formation of Cu(Phen)₃-bentonite composite. The expansion of the d₀₀₁ basal spacing of the Cu-Bent from 14.24 to 17.7 Å on intercalation and the colour change indicate the cation immobilized dimeric ligand species’ presence, which are thermally stable up to 315°C. The shift to higher frequency of the ring vibrations resulted from the π interactions is associated with the linkage of the tilted monomers to the smectite layers at elevated temperatures. The OH stretches and the bending peaks decrease in the intensity in parallel with an easy exchange between the water groups and the aromatic backboned ligands at room temperature.     

SDS (sodium dodecyl sulfate) effect on the autoxidation of the Glossoscolex paulistus giant extracellular hemoglobin: kinetic studies at pH 7.0 and 9.0

The effect of the anionic surfactant sodium dodecyl sulfate (SDS) on the autoxidation process of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) is addressed in the present work. The complex oligomeric assembly of hemoglobin subunits may influence the autoxidation rate and the exponential decay behavior. Kinetic studies were developed using UV-vis measurements at 415 nm. These spectroscopic measurements are analyzed at two pH values, 7.0 and 9.0, where the hemoglobin presents different oligomeric assembly. At pH 7.0 a high stability of the native form of the oxy-hemoglobin is observed, while at pH 9.0 an intense dissociation of the oligomer is promoted by alkalization. This difference is evident by comparison of the rate constants in the absence of surfactant: at pH 7.0 the kinetics presents a mono-exponential behavior with a rate constant of 0.27 x 10(-4)s(-1) while at pH 9.0 a bi-exponential behavior was observed with rate constant increase to 7 x 10(-4)s(-1) (fast process) and 1 x 10(-4)s(-1) (slow process). In the autoxidation induced by SDS two factors affect significantly the process rate, namely, the oligomeric arrangement of the hemoglobin and the strength of the interaction between SDS and HbGp. At pH 7.0, for SDS concentrations up to 0.3mM, a mono-exponential behavior was observed, showing rate constants around 0.4 x 10(-4)s(-1), which suggest that the hemoglobin still maintains the more compact structure observed at this pH for the native protein. In the SDS concentration range 0.75-1.0mM, the mono-exponential process changes into a bi-exponential behavior with rate constants varying from 48 x 10(-4) up to 99 x 10(-4)s(-1) for the fast process and from 1.7 x 10(-4) up to 3.7 x 10(-4)s(-1) for the slow process, suggesting hemoglobin dissociation. At pH 9.0, a bi-exponential decay is observed for all studied SDS concentration range, presenting rate constants from 11.0 x 10(-4) up to 179 x 10(-4)s(-1) for the fast process and from 1.0 x 10(-4) up to 8 x 10(4)s(-1) for the slow process probably due to hemoglobin dissociation, which is already present in the absence of surfactant. At pH 7.0, the highly packed native protein structure should inhibit the autoxidation process, but the SDS/HbGp interaction is more intense as compared to pH 9.0, due to the acid pI value, promoting oligomeric dissociation. So, the autoxidation process is regulated at pH 7.0 by the interaction with SDS, which triggers oligomeric dissociation and increase of autoxidation rate. At pH 9.0, the autoxidation process should be very fast, probably due to the oligomeric dissociation, which is already present in the absence of surfactant. At alkaline pH, the interaction with SDS seems be weaker than at pH 7.0. This behavior at pH 7.0 can be observed through the higher autoxidation rate for the faster chains and it is associated to the acid pI of the giant extracellular hemoglobins.