Characterizations of symmetric distributions based on Rényi entropy

It is proved that the equality of Rényi entropies of upper and lower order statistics as well as upper and lower k-records is a characteristic property of symmetric distributions. Also, for Farlie-Gumbel-Morgenstern (FGM) family, it is shown that under some conditions the equality of entropies of concomitants of upper and lower order statistics as well as concomitants of upper and lower record values is a characteristic property for the uniform distribution.     

Solubilization of naproxen using N-methyl-2-pyrrolidone or ethanol and β-cyclodextrin

Solubility trend of naproxen in the presence of 5 and 10 mM of β-CD was measured at 298.2 K and compared with solubility profiles in the absence of β-CD for water + cosolvent mixtures. The saturated solutions of the given volume fractions were reached using shake-flask method, and then the solubility values were measured by UV spectrophotometric method at 256 nm. Afterwards, the experimental solubility data points of naproxen in water + ethanol (EtOH) and water + N-methyl-2-pyrrolidone with and without β-cyclodextrin (β-CD) were correlated with Jouyban–Acree model. Calculation results revealed that the back-calculated solubilities were in good agreement with the corresponding experimental values. By applying the correlated equations, one can rapidly predict the solubility of naproxen in all solvent compositions.     

Binding of distamycin A to UV-damaged DNA

We have found that distamycin A can bind to DNA duplexes containing the (6-4) photoproduct, one of the major UV lesions in DNA, despite the changes, caused by photoproduct formation, in both the chemical structure of the base moiety and the local tertiary structure of the helix. A 20-mer duplex containing the target site, AATT.AATT, was designed, and then one of the TT sequences was changed to the (6-4) photoproduct. Distamycin binding to the photoproduct-containing duplex was detected by CD spectroscopy, whereas specific binding did not occur when the TT site was changed to a cyclobutane pyrimidine dimer, another type of UV lesion. Distamycin binding was analyzed in detail using 14-mer duplexes. Curve fitting of the CD titration data and induced CD difference spectra revealed that the binding stoichiometry changed from 1:1 to 2:1 with photoproduct formation. Melting curves of the drug-DNA complexes also supported this stoichiometry.     

Metal–organic framework-based mixed-matrix membranes for gas separation: An overview

Mixed-matrix membranes (MMMs) have been studied widely in the field of gas separation due to their potential to overcome performance barriers found in traditional polymeric membranes. Most polymeric membranes exhibit a trade-off between permeation and selectivity, which has limited their development in many challenging separation applications. One solution to this issue utilizes the introduction of fillers into the polymer matrix to produce MMMs. Out of the many different fillers, metal–organic frameworks stand out as a promising candidate due to their highly tunable structure, molecular sieving effect, and superior compatibility with the polymer matrix. This review will provide an in-depth look into the basic mechanisms of MMMs for gas separation and different approaches to model the permeation of gases through the membrane. In addition, challenges facing the field and recent research trends for MMMs will be discussed as well as their many applications for different gas separations. Finally, some insight on the future direction for MMMs will be covered, focusing on many intriguing opportunities and challenges that must be further explored to advance this technology.     

Fe3O4 Nanoparticles as an Efficient and Magnetically Recoverable Catalyst for Friedel–Crafts Acylation Reaction in Solvent-Free Conditions

Application of Fe₃O₄ nanoparticles (NPs) as a robust, very efficient, and magnetically recoverable catalyst was investigated in Friedel–Crafts acylation (FCA) of ferrocene and aromatic compounds. This reaction was performed with acid chlorides in solvent-free conditions at room temperature. The catalyst was easily separated by an external magnetic field from the reaction mixture. The separated catalyst was recycled for several consecutive runs without appreciable loss of its catalytic activity.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Osmotic and activity coefficients in the binary solutions of 1-butyl-3-methylimidazolium chloride and bromide in methanol or ethanol at T = 298.15 K from isopiestic measurements

Osmotic coefficients of the binary solutions of two room-temperature ionic liquids (1-butyl-3-methylimidazolium chloride and bromide) in methanol and ethanol have been measured at T = 298.15 K by the isopiestic method. The experimental osmotic coefficient data have been correlated using a forth-order polynomial in terms of (molality)^0.5, with both, ion interaction model of Pitzer and electrolyte non-random two liquid (e-NRTL) model of Chen. The values of vapor pressures of above-mentioned solutions have been calculated from the osmotic coefficients. The model parameters fitted to the experimental osmotic coefficients have been used for prediction of the mean ionic activity coefficients of those ionic liquids in methanol and ethanol.     

Analysis of five HMG-CoA reductase inhibitors-- atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin: pharmacological, pharmacokinetic and analytical overview and development of a new method for use in pharmaceutical formulations analysis and in vitro metabolism studies

A specific, accurate, precise and reproducible high-performance liquid chromatographic (HPLC) method was developed and validated for the simultaneous quantitation of five 3-hydroxy-3-methyglutaryl coenzyme A (HMG-CoA) reductase inhibitors, viz. atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin, in pharmaceutical formulations and extended the application to in vitro metabolism studies of these statins. Ternary gradient elution at a flow rate of 1 mL/min was employed on an Intertisl ODS 3V column (4.6 x 250 mm, 5 microm) at ambient temperature. The mobile phase consisted of 0.01 m ammonium acetate (pH 5.0), acetonitrile and methanol. Theophylline was used as an internal standard (IS). The HMG-CoA reductase inhibitors and their metabolites were monitored at a wavelength of 237 nm. Drugs were found to be 89.6-105.6% of their label's claim in the pharmaceutical formulations. For in vitro metabolism studies the reaction mixtures were extracted with simple liquid-liquid extraction using ethyl acetate. Baseline separation of statins and their metabolites along with IS free from endogenous interferences was achieved. Nominal retention times of IS, atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin were 7.5, 17.2, 21.6, 28.5, 33.5 and 35.5 min, respectively. The proposed method is simple, selective and could be applicable for routine analysis of HMG-CoA reductase inhibitors in pharmaceutical preparations as well as in vitro metabolism studies.     

Weak gravity conjecture from conformal field theory: a challenge from hyperscaling violating and Kerr-Newman-AdS black holes

We search for a possible relationship between weak gravity conjecture (WGC) and conformal field theory (CFT) in hyperscaling violating and Kerr-Newman-AdS black holes. We deal with the critical points of the black hole systems using the correlation function introduced in CFT and discuss WGC conditions using the imaginary part of the energy obtained from the critical points and their poles. Under the assumptions \begin{document}$ z=1 $\end{document}, \begin{document}$ d=1 $\end{document}, and \begin{document}$ \theta\rightarrow0^{-} $\end{document}, we link WGC to hyperscaling violating black holes owing to the existence of \begin{document}$ r_{H} $\end{document} values larger and smaller than one. For the second black hole system, we study the conditions of WGC for Kerr-Newman-AdS black holes using rotation and radius parameters. Then, we show that the conditions of WGC are satisfied when the charged particle near the hyperscaling violating and Kerr-Newman black holes is \begin{document}$ \frac{1}{a} $\end{document} with a ratio \begin{document}$ \frac{a}{\ell}\ll 1 $\end{document}.