Molecular and Biochemical Basis of Fluoroquinolones-Induced Phototoxicity—The Study of Antioxidant System in Human Melanocytes Exposed to UV-A Radiation

Phototoxicity of fluoroquinolones is connected with oxidative stress induction. Lomefloxacin (8-halogenated derivative) is considered the most phototoxic fluoroquinolone and moxifloxacin (8-methoxy derivative) the least. Melanin pigment may protect cells from oxidative damage. On the other hand, fluoroquinolone–melanin binding may lead to accumulation of drugs and increase their toxicity to skin. The study aimed to examine the antioxidant defense system status in normal melanocytes treated with lomefloxacin and moxifloxacin and exposed to UV-A radiation. The obtained results demonstrated that UV-A radiation enhanced only the lomefloxacin-induced cytotoxic effect in tested cells. It was found that fluoroquinolones alone and with UV-A radiation decreased superoxide dismutase (SOD) activity and SOD1 expression. UV-A radiation enhanced the impact of moxifloxacin on hydrogen peroxide-scavenging enzymes. In turn, lomefloxacin alone increased the activity and the expression of catalase (CAT) and glutathione peroxidase (GPx), whereas UV-A radiation significantly modified the effects of drugs on these enzymes. Taken together, both analyzed fluoroquinolones induced oxidative stress in melanocytes, however, the molecular and biochemical studies indicated the miscellaneous mechanisms for the tested drugs. The variability in phototoxic potential between lomefloxacin and moxifloxacin may result from different effects on the antioxidant enzymes.     

Iron‐Catalyzed Annulation of 1,2‐Diamines and Diazodicarbonyls for Diverse and Polyfunctionalized Quinoxalines,Pyrazines, and Benzoquinoxalines in Water

A novel and facile iron‐catalyzed tandem annulation of o‐phenylenediamines and diazocarbonyls in water for the construction of polyfunctionalized quinoxalines has been developed. The key strategy includes the one‐pot domino N−H insertion, cyclization, and oxidation reactions. This protocol offers a safe and mild synthetic approach to access a variety of quinoxaline derivatives in high yields. This methodology also allows the formation of biologically interesting pyrazines and benzoquinoxalines.

     

Self‐aggregation behavior of amphiphilic polyaspartamide derivatives containing cholesterol moieties

Biodegradable amphiphilic copolymers were successfully synthesized by the conjugation of various densities of hydrophobic biocompatible cholesterol (Chol) moieties onto poly(2‐hydroxyethyl aspartamide) and poly(N‐isopropylaminoethyl‐co‐2‐hydroxyethyl aspartamide). These were obtained from polysuccinimde, the thermal polycondensation product of L‐aspartic acid, via a ring‐opening reaction with multifunctional pendant groups, including ethanolamine and N‐isopropylethylenediamine (NIPEDA). Copolymers containing 5–30 mol % Chol showed self‐aggregation behavior in aqueous solution, as evidenced by the dynamic light scattering measurement of their particle size distribution. The average particle size of these copolymers increased linearly with increasing Chol content. Moreover, the presence of secondary amine groups in the poly(2‐hydroxyethyl aspartamide)–NIPEDA system made the conjugation more efficient; however, these also seemed to accelerate the degradation of the copolymers in an aqueous medium. The degradation behavior and pH dependence of the particle size of these copolymers in aqueous solution were also examined. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

烧结温度对La_(0.6)Ca_(0.4)MnO_3结构、磁性和磁致热效应的影响(英文)

研究了烧结温度对La0.6Ca0.4MnO3的结构、磁转变和磁熵的影响。观察表明,该化合物属于具有Pnma空间群的斜方晶系结构,不含任何杂质。研究烧结温度对居里温度(TC)的影响,发现提高烧结温度,TC稍有增大。磁致热效应研究显示,随着烧结温度的变化,磁熵会发生显著的变化。在外加磁场为3 T、烧结温度为1300°C时,相对冷却能(RCP)为89 J/kg。因此,该化合物可以考虑作为在室温附近或低于室温的潜在磁制冷材料。     

Accelerated engineering design optimization using successive matrix inversion method

In a design optimization procedure, many repeated system analyses are conducted to evaluate certain performances of successively modified structural designs. To alleviate the high computational cost of structural reanalysis, an augmented preconditioner is introduced by using the successive matrix inversion (SMI) method. The SMI method, as an exact matrix solver, is successively applied to an iterative procedure to accelerate the solution convergence by improving the numerical condition of the reanalysis system. In this work, a new iterative technique, the binomial series iterative (BSI) method, is developed from the binomial series expansion by using the same concept as SMI. As a combined iterative (CI) method, SMI is incorporated in the procedure of BSI. The CI method, combined with SMI, shows sufficient efficiency and robustness through a stable iterative behaviour due to simple and straightforward computations in the iterative procedure. Published in 2005 by John Wiley & Sons, Ltd.     

Gas-phase synthesis of AlN powders from AlCl3-NH3-N2

Aluminium nitride powders were synthesized by the gas-phase reaction of AlCl₃-NH₃-N₂ system. The yield of AlN powders from AlCl₃ and their crystallinity increased as the reaction temperature and the mole ratio of NH₃/AlCl₃ were increased. AlN powders were also formed outside the reactor and their crystallinity was amorphous. The yield of AlN powders was as high as 80% when the reactor temperature was 1000 °C and the mole ratio of NH₃/AlCl₃ was 8. Most of the HCl by-product was recovered as NH₄Cl outside the reactor. Powder characteristics, such as shape, size distribution and crystallinity, were also studied.     

A Dynamic Packet Recovery Mechanism for Realtime Service in Mobile Computing Environments

This paper analyzes the characteristics of packet losses in mobile computing environments based on the Gilbert model and then describes a mechanism that can recover the lost audio packets using redundant data. Using information periodically reported by a receiver, the sender dynamically adjusts the amount and offset values of redundant data with the constraint of minimizing the bandwidth consumption of wireless links. Since mobile computing environments can be often characterized by frequent and consecutive packet losses, loss recovery mechanisms need to deal efficiently with both random and consecutive packet losses. To achieve this, the suggested mechanism uses relatively large, discontinuous exponential offset values. That gives the same effect as using both the sequential and interleaving redundant information. To verify the effectiveness of the mechanism, we extended and implemented RTP/RTCP and applications. The experimental results show that our mechanism, with an exponential offset, achieves a remarkably low complete packet loss rate and adapts dynamically to the fluctuation of the packet loss pattern in mobile computing environments.     

Preparation and characterization of polyacrylamide cryogels produced from a high‐molecular‐weight precursor. II. The influence of the molecular weight of the polymeric precursor

Polyacrylamide gels and cryogels were prepared by the crosslinking reaction of polyacrylamide (a polymeric precursor) with glutaric aldehyde (a crosslinking agent) in liquid and moderately frozen aqueous media, respectively. Polymeric precursors of different viscosity‐ averagemolecular weights (0.3, 1, 3, and 9 MDa) were used. The molecular weight of the precursors, as well as the reaction temperature and concentration of the crosslinking agent, exerted a pronounced influence on the efficiency of gelation (gel fraction yield) and on the properties (swelling capability) and structural peculiarities of the resulting gels (reference samples) and cryogels. The highest efficacy was inherent in the cryotropic gelation process when the polymeric precursor had a molecular weight of about 3 MDa, whereas the implementation of polyacrylamides of lower (0.3 or 1 MDa) or higher (9 MDa) molecular weights diminished the gel formation efficiency. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008