Quantum: Einstein,Bohr and the Great Debate About the Nature of Reality,by Manjit Kumar

The history of absolute measurements of gravity is mentioned and the reasons for making absolute measurements are indicated. The principles and main advantages and difficulties of the main method—reversible pendulum, free fall, symmetrical free motion—are discussed and examples of each method are described. Problems of comparison of different determinations and of estimating systematic errors are considered.     

Characterization of self-assembled lamellar thermoresponsive silica-hydrogel nanocomposite films

Mesostructured lamellar nanocomposite films with alternating silica and organic layers containing poly(N-isopropropyl acrylamide) (PNIPAM) were prepared using evaporation-induced self-assembly. A suitable theoretical approach to analyze the small-angle X-ray scattering (SAXS) patterns of oriented lamellar two-phase systems was applied to the SAXS data of films of varying composition, providing details on the self-assembly process, the composition, and the polymerization. In particular, this approach allowed an accurate determination of the thickness of the silica and the organic layer. The applicability of the SAXS approach was carefully tested with simulated data and verified by thermogravimetric analysis (TGA). TGA and (13)C NMR were used to study the polymerization and linkage to the silica matrix. SAXS and time-resolved grazing incidence SAXS revealed that the phase transition of PNIPAM at ca. 32 degrees C leads to a reversible expansion/contraction perpendicular to the layers on a time scale of ca. 30 min.     

Self-directed assembly of photoactive hybrid silicates derived from an azobenzene-bridged silsesquioxane

Hybrid silicate materials derived from organo-bridged silsesquioxane precursors, RO3-Si-R'-Si-OR3, where R and R' are organic ligands, represent a remarkably diverse class of nanocomposites capable of forming both Si-O-Si and Si-C-Si bonds with molecular scale homogeneity. Recently, in an effort to better control their structure and function, surfactant-directed self-assembly or self-directed assembly has been used to synthesize hierarchical organo-bridged polysilsesquioxanes that exhibit order over multiple length scales. Here we report the synthesis and self-directed assembly of an optically active azobenzene-bridged silsesquioxane, 4,4'-bis(3-triethoxysilylpropylureido)azobenzene 1. Hydrogen-bonding interactions between the three active centers of the bis-ureide groups (-NH-CO-NH) combined with pi-pi interactions between the azobenzene groups serve to self-assemble 1 into a highly ordered lamellar mesostructure in which the d-spacing is optically controlled through photoisomerization of the azobenzene moiety before or after assembly.     

Thin-layer chromatography/liquid secondary ion mass spectrometry in the determination of major bile salts in dog bile

Positive and negative ion liquid-state secondary-ion mass spectrometry (LSIMS) was applied to several bile acids and bile salts and their spectra were measured directly from the surface of silica gel thin-layer chromatograms. Such spectra were identical to the LSIMS spectra of the pure compound at the same concentration. Three-dimensional ion images were obtained of a model mixture of cholic, chenodeoxycholic and lithocholic acids in both the positive and negative ion modes. A sample of dog bile was prepared, and the bile acids extracted from it were separated by high-performance TLC; TLC/LSIMS spectra were obtained for sodium taurocholate and sodium taurochenodeoxycholate/taurodeoxycholate, the predominant bile salts present. Quantitative estimates of the analytes were obtained by monitoring the ion intensity for the sample spot and a standard spot that had been developed in parallel on the same TLC plate. The concentration of sodium taurocholate in the bile of this particular dog was found to be 38 mg/ml.     

Water-soluble alkylated bis{4'-(4-pyridyl)-2,2':6',2'-terpyridine}ruthenium(II) complexes for use as photosensitizers in water oxidation: a complementary experimental and TD-DFT investigation

A series of N-alkylated derivatives [RuL(2)][PF(6)](4) has been prepared from [Ru(pytpy)(2)][PF(6)](2) (N-alkyl substituent = 4-cyanobenzyl, 4-nitrobenzyl, ethyl, cyanomethyl, allyl, octyl). Solution NMR spectroscopic, electrochemical and photophysical properties are reported, along with the single crystal structure of [Ru(4)(2)][PF(6)](4)·H(2)O (4 = 4'-(4-(1-ethylpyridinio))-2,2':6',2'-terpyridine). Anion exchange leads to the water-soluble [RuL(2)][HSO(4)](4) salts (N-alkyl substituent = benzyl, 4-cyanobenzyl, 4-nitrobenzyl, ethyl, cyanomethyl, allyl, octyl) and the NMR spectroscopic signatures of pairs of hexafluoridophosphate and hydrogensulfate salts are compared. The change in anion has little effect on the energies of absorptions in the electronic spectra, although for all complexes, decreases in extinction coefficients are observed. The emission spectra and lifetimes for the hexafluoridophosphate and hydrogensulfate salts show similar trends; all exhibit an emission close to 720-730 nm (λ(ex) = 510 nm). For a given ligand, L, the emission lifetime decreases on going from [RuL(2)][PF(6)](4) to [RuL(2)][HSO(4)](4). However, trends are the same for both salts, i.e. the longest lived emitters are observed for N-ethyl, N-octyl and N-benzyl derivatives, and the shortest lived emitters are those containing cyano or nitro groups. Significantly, in the absorption spectra of the complexes, there is little variation in the energy of the MLCT band, suggesting that the character of the ligand orbital involved in the transition contains no character from the N-substituent. We have addressed this by carrying out a complementary DFT and TD-DFT study. Calculated absorption spectra predict a red shift in λ(max) on going from [Ru(pytpy)(2)](2+) to [RuL(2)](4+), and little variation in λ(max) within the series of [RuL(2)](4+) complexes; these results agree with experimental observations. Analysis of the compositions of the MOs involved in the MLCT transitions explain the experimental observations, showing that there is no contribution from orbitals on the N-alkyl substituents, consistent with the fact that the nature of the N-substituents has little influence on the energy of the MLCT band. The theoretical results also reveal satisfactory agreement between calculated and crystallographic data for [Ru(1)(2)](4+) (1 = 4'-(4-(1-benzylpyridinio))-2,2':6',2'-terpyridine) and [Ru(4)(2)](4+).