Synthetic Peroxides Promote Apoptosis of Cancer Cells by Inhibiting P-Glycoprotein ABCB5

This article discloses a new horizon for the application of peroxides in medical chemistry. Stable cyclic peroxides are demonstrated to have cytotoxic activity against cancer cells; in addition a mechanism of cytotoxic action is proposed. Synthetic bridged 1,2,4,5-tetraoxanes and ozonides were effective against HepG2 cancer cells and some ozonides selectively targeted liver cancer cells (the selectivity indexes for compounds 11 b and 12 a are 8 and 5, respectively). In some cases, tetraoxanes and ozonides were more selective than paclitaxel, artemisinin, and artesunic acid. Annexin V flow-cytometry analysis revealed that the active ozonides 22 a and 23 a induced cell death of HepG2 by apoptosis. Further study showed that compounds 22 a and 23 a exhibited a strong inhibitory effect on P-glycoprotein (P-gp/ABCB5)-overexpressing HepG2 cancer cells. ABCB5 is a key player in the multidrug-resistant phenotype of liver cancer. Peroxides failed to demonstrate a direct correlation between oxidative potential and their biological activity. To our knowledge this is the first time that peroxide diastereoisomers have been found to show stereospecific antimalarial action against the chloroquine-sensitive 3D7 strain of Plasmodium falciparum. Stereoisomeric ozonide 12 b is 11 times more active than stereoisomeric ozonide 12 a (IC₅₀=5.81 vs 65.18 μm ). Current findings mean that ozonides merit further investigation as potential therapeutic agents for drug-resistant hepatocellular carcinoma.     

Local and high-strength joining of transparent glass and glass-ceramics by femtosecond Bessel beam

The creation of robust joint among different materials with notably different coefficients of thermal expansion (CTE) is an urgent task for the development of the engineering, laser technology, and aerospace industry. In this regard, femtosecond laser welding is a promising technique for efficient adhesion-free bonding of transparent materials. This paper reports on the laser welding of laser phosphate glass (CTE = 110 × 10⁻⁷ K⁻¹) and spinel-based glass–ceramic (CTE = 50 × 10⁻⁷ K⁻¹) by the Bessel beam. Dependencies of weld geometric parameters on the pulse energy and scanning speed were investigated, and the laser exposure conditions were optimized for durable welding. The weld joints were tested on shear strength, which was shown to be as record high as up to 147 MPa. Atomic force microscopy, Raman spectroscopy, and elemental analysis were used to investigate the structure and morphology of the weld after its fracture, which revealed the laser-induced amorphization of glass–ceramics and the formation of strong interconnection by laser-driven mutual diffusion of two glassy phases. The results demonstrate the prospects for using femtosecond lasers for efficient industrial welding of a wide range of materials.     

Contribution of the edge effect to physical adsorption in micropores of activated carbons

The adsorption process in activated carbon micropores can be viewed as a two-dimensional condensation on micropore walls at a critical condensation pressure, p_c, which evolves into volume filling. p_c on a surface of micropore walls is calculated in respect to a critical condensation pressure on the reference nonporous surface, p_c^ref. Although theoretical treatment predicts that p_c^ref should be a parameter of adsorption isotherms, experimental isotherm equations are expressed in terms of the bulk saturation pressure, p_s. Experimental values of p_s/p_c^ref for a graphitized carbon black, which is often considered as a model of activated carbon surfaces, range from 37 to 4000 for typical adsorbates and are by no means close to unity. It is proposed that this apparent discrepancy between theory and experiments has its origin in the edge effects: carbon blacks are modeled by semi-infinite slabs, whereas the magnitudes of thickness and diameters of micropore walls are of the order of a nanometre. Factors associated with edge effects reduce the adsorption energies on surfaces of finite particles resulting in shifts of condensation pressures to higher values. For particles with diameters about 1.4 and 1.8 nm, adsorption energies decrease to ≈0.72ε₁*^∞ and ≈0.81ε₁*^∞, respectively, where ε₁*^∞ is the energy of adsorption on an infinite plane, and p_c approaches p_s. This phenomenon substantiates the application of p_s in adsorption equations and the success of the Dubinin equations probably owes much to this fact.     

Effect of Dilution and Porosity on Self-Propagating High-Temperature Synthesis of Silicon Nitride

Self-propagating high-temperature synthesis is a very easy and low-cost method to synthesize Si₃N₄. The nitriding of silicon powder takes place in a self-sustained regime under high pressures of nitrogen with dilution of silicon by Si₃N₄. In this work effects of dilution and green-mixture porosity on combustion velocity and phase content of reaction products are studied. Results are compared with previous work of other authors and different behaviors are found. An explanation of these behaviors is given.     

Raman Spectroscopy of Nanocrystalline Ceria and Zirconia Thin Films

The results of Raman-scattering studies of nanocrystalline CeO₂ and ZrO₂:16% Y (YSZ) thin films are presented. The relationship between the lattice disorder and the form of the Raman spectra is discussed and correlated with the microstructure. It is shown that the Raman line shape results from phonon confinement and spatial correlation effects and yields information about the material nonstoichiometry level.     

New Refractories Developed by the Ukrainian Research Institute of Refractories Named after A.S. Berezhnoy

The article gives an introduction to the Ukrainian Research Institute of Refractories and especially its R D and refractory products for the industries of iron and steel,nonferrous,glass and chemistry etc.     

Self-diffusion of low-generation PAMAM dendrimers with hydroxyl surface groups in solutions: a general regularity

An experimental study of the self-diffusion and nuclear magnetic relaxation of poly(amidoamine) dendrimers with hydroxyl surface groups (PAMAM-OH) dissolved in methanol over a wide range of concentration (?) is reported. It is shown that experimental concentration dependences of PAMAM-OH self-diffusion coefficients (D) can be reduced to the so-called generalized ? dependence. Over macromolecular concentration range studied, the generalized concentration dependence of PAMAM-OH D coincides with analogous curve obtained for poly(allylcarbosilane) dendrimers of high generations. This result confirms the existence of common regularities of the dendritic macromolecule self-diffusion, and their independence of the individual physicochemical and structural properties of dendrimer, solvent, and features of their interactions in the given systems. The concentration dependence of the PAMAM-OH diffusion also exhibits a clear signature of an inflexible molecule.