Silver nanoparticles obtained with a glucose modified siloxane surfactant

Journal of Nanoparticle Research - Silver nanoparticles were obtained in aqueous medium, at room temperature, by redox reactions, with or without glucose, in the presence of a glucose-containing...     

The application of the boundary element method to the magnetohydrodynamic duct flow

A boundary element method is developed in order to investigate the flow of viscous, incompressible, electrically conducting fluids in cylindrical ducts having arbitrary cross-sections. The numerical results obtained for the circular duct with insulating wall are very close to the results obtained by means of analytical formulas.     

Hexachlorantimonate(V) mit Nitroverbindungen als Liganden, 1. Mitt.: Komplexverbindungen mit einwertigen Metallen

Hexachloroantimonates with nitroderivatives as ligands on the cations are formed in a double complexation reaction of a mono-valent metal chloride (LiCl, NaCl, KCl, CuCl) with SbCl₅, and a nitroderivativeL (nitromethane, nitrobenzene, α-nitronaphthalene). Solid complexes of the typeML(SbCl₆) andML ₂(SbCl₆) were isolated. Synthesis, analytical results andi.r. spectra are discussed.     

Nuclear stopping in Au+Au collisions at square root of S(NN)=200 GeV

Transverse momentum spectra and rapidity densities, dN/dy, of protons, antiprotons, and net protons (p-p) from central (0%-5%) Au+Au collisions at square root of S(NN)=200 GeV were measured with the BRAHMS experiment within the rapidity range 0相似文献   

Rapidity dependence of antiproton-to-proton ratios in Au+Au collisions at square root of (sNN) = 130 GeV

Measurements, with the BRAHMS detector, of the antiproton-to-proton ratio at midrapidities and forward rapidities, are presented for Au+Au reactions at square root of [s(NN)] = 130 GeV, and for three different collision centralities. For collisions in the 0%-40% centrality range, we find N(&pmacr;)/N(p) = 0.64+/-0.04((stat))+/-0.06((syst)) at y approximately 0, 0.66+/-0.03+/-0.06 at y approximately 0.7, and 0.41+/-0.04+/-0.06 at y approximately 2. The ratios are found to be nearly independent of collision centrality and transverse momentum. The antiproton and proton rapidity densities vary differently with rapidity, and indicate a significant degree of collision transparency, although a net-baryon free midrapidity plateau (Bjorken limit) is not yet reached.     

Chiral organic contact ion pairs in metal-free catalytic asymmetric allylic substitutions

Chiral contact ion-pair catalysis with particular focus on metal-free processes is gaining in interest. As a result, new perspectives are opened, and highly stereoselective transformations, traditionally performed under metal catalysis, can be realized. Herein, we report the development of an unprecedented asymmetric Br?nsted acid-catalyzed allylic alkylation. The concept relies on chiral contact ion-pair catalysis, in which the chiral organic counteranion of an allylic carbocation induces high enantioselectivities and allows access to biologically relevant chromenes in good yields and with excellent enantioselection.     

Structure and dynamics of photosystem II light-harvesting complex revealed by high-resolution FTICR mass spectrometric proteome analysis

Structure and dynamics of membrane-bound light-harvesting pigment-protein complexes (LHCs), which collect and transmit light energy for photosynthesis and thereby play an essential role in the regulation of photosynthesis and photoprotection, were identified and characterized using high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LHCs from photosystem II (LHCII) were isolated from the thylakoid membrane of Arabidopsis thaliana leaves after light stress treatment using sucrose density gradient centrifugation, and separated by gel-filtration into LHCII subcomplexes. Using reversed-phase high-performance liquid chromatography and two-dimensional (2D) gel electrophoresis, the LHCII proteins, Lhcb1-6 and fibrillins, were efficiently separated and identified by FTICR-MS. Some of the LHCII subcomplexes were shown to migrate from photosystem II to photosystem I as a result of short-term adaptation to changes in light intensity. In the mobile LHCII subcomplexes, decreased levels of fibrillins and a modified composition of LHCII protein isoforms were identified compared to the tightly bound LHCII subcomplexes. In addition, FTICR-MS analysis revealed several oxidative modifications of LHCII proteins. A number of protein spots in 2D gels were found to contain a mixture of proteins, illustrating the feasibility of high-resolution mass spectrometry to identify proteins that remain unseparated in 2D gels even upon extended pH gradients.     

Theoretical study of β and γ-cyclodextrins inclusion complexes with nineteen atropisomeric polychlorobiphenyls

Inclusion complexes of β and γ-cyclodextrins (CDs), chirally selective macrocycles, with 19 atropisomeric polychlorinated biphenyls (PCBs), stable at physiological temperatures, were studied by molecular mechanics optimized potential for liquid simulations and semi-empirical quantum AM1 methods. Bimodal manual docking, geometry optimization and single point calculations were done. PCB:CD complex formation was studied considering two ways of entry in the large base of CD cavity: with biphenyl C1–C1′ bond axis of PCBs oriented parallel and anti-parallel with the CD trunk height axis. A distance dependent dielectric constant was used to account for the solvent effect. The values of complexation and binding energies were calculated, confirming the existence of a specific van der Waals (vdW) type interaction. β and/or γ-CD chiral recognition of the 19 atropisomeric PCBs, is described by means of the complexation and binding energy values. The binding energy is a better discriminator of PCBs enantiomers than complexation energy considering the average energy differences between (+) and (?) PCB:β/γ-CD complexes. The chromatographic elution order of several PCB enantiomers from literature was correlated with the complexation and binding energies. The molecular modeling of inclusion complexes is recommended to be used as enantiomer identification tool in correlation with chromatographic data.     

Ultrasound influence upon calcium carbonate precipitation on bacterial cellulose membranes

The effect of ultrasonic irradiation (40 kHz) on the calcium carbonate deposition on bacterial cellulose membranes was investigated using calcium chloride (CaCl₂) and sodium carbonate (Na₂CO₃) as starting reactants. The composite materials containing bacterial cellulose-calcium carbonate were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and color measurements. The polymorphs of calcium carbonate that were deposited on bacterial cellulose membranes in the presence or in the absence of ultrasonic irradiation were calcite and vaterite. The morphology of the obtained crystals was influenced by the concentration of starting solutions and by the presence of ultrasonic irradiation. In the presence of ultrasonic irradiation the obtained crystals were bigger and in a larger variety of shapes than in the absence of ultrasounds: from cubes of calcite to spherical and flower-like vaterite particles. Bacterial cellulose could be a good matrix for obtaining different types of calcium carbonate crystals.