Refractive index distribution measurements by means of spectrally-resolved white-light interferometry

A new procedure to measure the spatial distribution of the refractive index in transparent media is presented. It is based on the spectral analysis of optical interferograms obtained from a wide, continuous-spectrum light source. The method yields fairly high precision (up to 10^-8) in the measurements of local values of differential refractive index, Δn (Δn=n−n_ref), along a line in the sample. By means of a CCD TV-camera linked to a microcomputer, fast recording and automatic data processing are achieved. As an application, we present an experimental study of a thermal gradient in a liquid sample.     

Understanding STM images and EELS spectra of oxides with strongly correlated electrons: a comparison of nickel and uranium oxides

Using a theoretical approach combining the local spin density approximation (LSDA) of density functional theory and the Hubbard U term (LSDA + U), we analyse the connection between the experimentally observed electron energy loss spectra and elevated temperature scanning tunnelling images of surfaces of semiconducting nickel monoxide NiO and uranium dioxide UO2. We show that a combination of electron energy loss spectroscopy, atomic-resolution tunnelling imaging and first-principles ab initio calculations provides a powerful tool for studying electronic and structural properties of surfaces of transition metal and actinide oxides.     

Kinetic salt effects in the bromide oxidation by bromate

The kinetic salt effect on the oxidation of bromide ion by bromate have been studied. It is concluded that the salt effects are the result of ion-solvent interactions and seem to be connected not only to the strength of these interactions, as measured by the lowering of solvent activity, but also by the structural characteristics of ion-solvent interactions. This conclusion is based on the use of Pitzer's treatment to estimate the activity coefficients.     

Primary photochemical processes of the phototoxic neuroleptic cyamemazine: a study by laser flash photolysis and steady-state irradiation

The photophysical and photochemical properties of the UV-A-absorbing phototoxic drug cyamemazine (CMZ) (2-cyano-10-(3-[dimethylamino]-2-methyl-propyl)-phenothiazine) have been investigated in neutral buffered aqueous solutions. The transient absorbances of the hydrated electrons, of the first excited triplet state (3CMZ*) with a characteristic absorption band peaking at 420 nm and of the radical cation (*CMZ+) (maximum absorbance at 500 nm) have been observed by 355 nm laser flash spectroscopy of deaerated solutions. All these transient species are formed by monophotonic processes and react with oxygen. Bimolecular reaction rate constants of *CMZ+ and 3CMZ* with O2 are 2 x 10(7) M(-1) s(-1) and 4 x 10(9) M(-1) s(-1), respectively. The 3CMZ* reacts only sluggishly (reaction rate constant, 9 x 10(6) M(-1) s(-1)) with tryptophan chosen as a Type-I photodynamic substrate. Steady-state irradiations with 365 nm light demonstrate that CMZ is rapidly photolyzed (quantum yield, 0.04) in O2-saturated solutions leading to oxidation of the sulfur atom and of the side-chain nitrogen of CMZ. This photoproduct (2-cyano-10-(3-[dimethylamino, N-oxide]-2-methyl-propyl)-5-oxide-phenothiazine), is a good Type-I and Type-II photodynamic photosensitizer producing singlet oxygen in high yield (approximately 0.45) and could play a major role in the phototoxicity of CMZ.     

Strictly positive definite functions in

We give a sufficient condition for strictly positive definiteness in . The result is based on the question how sparse subsets of can be to guarantee linear independence of the exponentials.     

Guest‐Induced Structural Transformations in a Porous Halogen‐Bonded Framework

Structural evidence obtained from in situ X‐ray diffraction shows that halogen bonding is responsible for the formation of a dynamic porous molecular solid. This material is surprisingly robust and undergoes reversible switching of its pore volume by activation or by exposure to a series of gases of different sizes and shapes. Volumetric gas sorption and pressure‐gradient differential scanning calorimetry (P‐DSC) data provide further mechanistic insight into the breathing behavior.     

Formation of polypyrrole chains in alumina and chromia-pillared layered phosphates

The reaction of gaseous pyrrole (pyr) with Cu²⁺ exchanged alumina- and chromia-pillared -tin and -zirconium phosphates has been investigated. Preliminary exchange with Cu²⁺ reveals differences in ordering in the two types of oxide-pillared materials, ascribed to differences in precursor insertion during their preparation. In both oxide-pillared types, the pyr rapidly polymerises in the pores (not on the surface). Optical spectra and XPS evidence point to the presence of more than one type of pyr polymer, and hence of a porous system. The optical properties are typical of mixed neutral and bipolaron states with the presence of low-oxidation level polypyrrole. Based on similarities in optical properties with zeolite analogues, it is suggested that the starting materials contain porous systems similar to both zeolite-Y and mordenite present together. As for zeolite-Y and mordenite analogues, the materials have negligible conductances ( < 10^{–9 –1} cm^–1), which is ascribed to the presence of only short polymeric pyr units.     

MOLECULAR BASIS OF DRUG PHOTOTOXICITY: PHOTOSENSITIZED CELL DAMAGE BY THE MAJOR PHOTOPRODUCT OF TIAPROFENIC ACID

Abstract Tiaprofenic acid is a photosensitizing nonsteroidal anti-inflammatory drug, whose major photoproduct (decarboxytiaprofenic acid) is also a potent photosensitizer. Because of the lack of the carboxylate moiety, this photoproduct is more lipophilic and might bind more efficiently to cell membranes, thereby causing phototoxic damage. To verify the feasibility of this hypothesis, we have prepared the ³H-labeled analogs of tiaprofenic acid and its photoproduct and examined the binding, persistence and phototoxicity of the photoproduct using poorly metabolizing (fibroblasts) and actively metabolizing cells (hepatocytes). The photoproduct of tiaprofenic acid accumulates in both cell types as it is formed. Upon removal of the photoproduct from the culture medium, it rapidly disappears from hepatocytes but not from fibroblasts. Consequently, irradiation of fibroblasts previously incubated with the photoproduct and kept in culture in the dark for 20 h results in generalized cell damage while this effect is not observed in hepatocytes. Because of its long persistence in poorly metabolizing skin cells and its reluctance to photobleaching, the formation of this photoproduct in skin may be of relevance to explain the in vivo phototoxicity of tiaprofenic acid.     

Damage to mitochondria of cultured human skin fibroblasts photosensitized by fluoroquinolones

The phototoxic fluoroquinolones ofloxacin, lomefloxacin, norfloxacin, ciprofloxacin and BAYy 3118 have ionizable groups with pKa values close to neutrality. Different ionic species of these fluoroquinolones, therefore, partition in various compartments and organelles of living cells according to their ionic equilibria. While all these fluoroquinolones accumulate in lysosomes, they more or less stain the rest of the cytoplasm of living HS 68 fibroblasts. As a result, photosensitized damage to other cytoplasmic sites than lysosomes can also be expected. Using microfluorometry and rhodamine 123 (Rh 123) as a specific fluorescent probe which is released from mitochondria by light absorption, we show that under ultraviolet A (UVA) irradiation norfloxacin and ciprofloxacin readily damage mitochondrial membranes. as evidenced by the UVA dose-dependent strongly accelerated release of Rh 123 from mitochondria in cells treated with norfloxacin and ciprofloxacin. Damages are already noticeable at UVA doses as low as 2 J/cm2. By contrast, no such photoinduced damage can be observed with ofloxacin, lomefloxacin and BAYy 3118, the latter being the most phototoxic derivative towards HS 68 fibroblasts. The initial photodamage induced by norfloxacin and ciprofloxacin can then propagate after the irradiation as shown by the strongly increased rate of release of Rh 123 from mitochondria of cells that have been incubated with these two fluoroquinolones and left in the dark after a pre-irradiation with 18 J/cm2 of UVA. Interestingly, the same pre-irradiation after cells have been treated with BAYy 3118 and lomefloxacin induces similar post-irradiation effects, although they have no apparent immediate photosensitizing action on mitochondria.     

Ab Initio CI Determination of the Exchange Coupling Constant of Doubly-Bridged Nickel(II) Dimers

Ab initio DDCI2 (difference-dedicated configuration interaction) calculations are performed on the exchange coupling constant of the doubly-bridged Ni(II) complexes [Ni(en)(2)Cl](2)(2+) and [Ni(terpy)(N(3))](2)(2+), which are modeled by substituting the external ligands with ammonia groups. The variational CI space is selected on the grounds of the effective Hamiltonian theory and includes all the second-order contributions to the difference between the lowest quintet, triplet, and singlet states. Both complexes are found to be ferromagnetic, with coupling constants of 1.8 and 21.1 cm(-1), in good agreement with the experiment. A transformation of the molecular orbitals is also proposed for large systems, enabling the molecular orbital set to be significantly truncated-as well as the file of two-electron integrals and the DDCI2 space-with no loss of efficiency.