The influence of pH on the alternate multi-layered adsorption of macrocations and macroanions on colloidal spheres

The -potential and thickness of the alternate multiple adsorption layers of macrocations and macroanions on the surfaces of colloidal spheres in suspension were measured at pH values ranging from 2.8 to 10.8 via electrophoretic light-scattering measurements. Colloidal silica spheres (110 nm in diameter) were used. The macrocations used were poly(4-vinyl-N-n-butyl pyridinium bromide) (C4PVP, a strongly basic macroion) and poly (allylamine) (PAL, which is weakly basic). Sodium poly(styrene sulfonate) (NaPSS, strongly acidic) and sodium polyacrylate (NaPAA, weakly acidic) were used as macroanions. The macrocations were added first in all of the experiments. The alternate adsorption of C4PVP and NaPSS takes place for a wide range of pH values, between 2.8 and 8.7. For C4PVP + NaPAA systems, alternate layers are formed only at neutral pH values and within three to six layers. Multiple adsorption phenomena are observed at acidic and neutral pH values for PAL + NaPSS and PAL + NaPAA systems, respectively. These results strongly support the theory that the synchronous delicate balancing of the electrostatic interactions among the macrocations, the macroanions, and the colloidal spheres is important for the alternate multiple adsorption.     

Focusing coherent soft-x-ray radiation to a micrometer spot size with an intensity of 10(14) W/cm2

We investigate the focusability of intense coherent soft-x-ray radiation generated by high-order harmonic conversion. The 27th-harmonic wave at 29.6 nm is focused by an off-axis parabolic mirror with a SiC/Mg multilayer coating. Focal-spot images are observed from the visible fluorescence induced by the soft-x-ray photons on a Ce:YAG scintillator. We demonstrate focusing of the soft-x-ray beam to a 1-microm spot size with a peak intensity of 1 x 10(14) W/cm2, which is to our knowledge the highest ever reported in the soft-x-ray region.     

Facile preparation of a new BINAP-based building block, 5,5'-diiodoBINAP, and its synthetic application

[reaction: see text] Bis(pyridine)iodonium tetrafluoroborate was successfully used for regioselective iodination of BINAP dioxide to give 5,5'-diiodoBINAP dioxide in an excellent yield of 92%, with no observed formation of 4,4'-diiodoBINAP dioxide. A Sonogashira cross-coupling reaction with 5,5'-diiodoBINAP dioxide gave the desired bis(trimethylsilylethynyl) product in 86% yield. The resulting 5,5'-disubstituted BINAP dioxides were reduced to the corresponding phosphines, which were used as chiral ligands for rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid to 2-cyclohexenone to give 3-phenylcyclohexanone in excellent yield with high enantioselectivity.     

Momentum distribution of 15B fragments from the breakup of 17B

The two-neutron removal cross section (sigma(-2n)) and the longitudinal momentum distribution of 15B fragments from the breakup of 17B on 9Be were measured at 70A MeV. The distribution in the projectile rest frame is characterized by a FWHM of 80+/-10 MeV/c for 15B. The sigma(-2n) is found to be 0.22+/-0.05 b. A Glauber-type analysis of the data provides clear evidence of a two-neutron halo structure in 17B.     

EFFECTS OF DEMETHYLCHLORTETRACYCLINE PHOTOTOXICITY ON THE STRUCTURE and FUNCTIONS OF RAT LIVER MITOCHONDRIA

The phototoxic effects of demethylchlortetracycline (DMCT) with UVA radiation on isolated rat liver mitochondria were studied. DMCT at concentration of 21.5 microM with 5.53 x 10(-2) J cm-3 of UVA was found to be a potent uncoupler of oxidative phosphorylation. DMCT alone also uncoupled mitochondria but at higher concentrations (105 microM). ATPase activity was remarkably induced in mitochondria exposed to DMCT (21.5 microM) plus UVA (120% of DNP-stimulated ATPase activity). Content of ATP in such mitochondria when measured after addition of ADP was much smaller than that in control mitochondria. Ultrastructurally, mitochondria treated either with DMCT (21.5 microM) or with UVA alone stayed in the condensed configuration. On the other hand, uncoupled mitochondria treated with DMCT plus UVA became swollen and were changed into the orthodox configuration.