Imide photodissociation investigated by X-ray absorption spectroscopy.

X-ray absorption spectroscopy is used to investigate the photodissociation of the imides PMDI (pyromellitic diimide) and SSMCC (sulfosuccinimidyl 4-(N-maleimidomethyl) cyclohexane-1-carboxylate). PMDI contains only one type of imide, and its photodissociation can be explained by a simple conversion from imide to a mix of imine and nitrile after desorption of the oxygens from the imide. SSMCC contains two different imides.

Nuclear dynamics and spectator effects in resonant inelastic soft x-ray scattering of gas-phase water molecules.

The electronic structure of gas-phase H(2)O and D(2)O molecules has been investigated using resonant inelastic soft x-ray scattering (RIXS). We observe spectator shifts for all valence orbitals when exciting into the lowest three absorption resonances. Strong changes of the relative valence orbital emission intensities are found when exciting into the different absorption resonances, which can be related to the angular anisotropy of the RIXS process.

[Effects of mechanical ventilation and positive end-expiratory on central venous pressure].

Objective: To investigate the effects of mechanical ventilation and positive end expiratory pressure (PEEP) on central venous pressure (CVP).

Methods: Forty cases of respiratory failure with mechanical ventilation were enrolled. Catheter was inserted via subclavian vein in each.

Universal mechanism for breaking amide bonds by ionizing radiation.

The photodissociation of the amide bond by UV light and soft x-rays is investigated by x-ray absorption spectroscopy at the C, N, and O 1s edges. Irradiation leaves a clear and universal signature for a wide variety of amides, ranging from oligopeptides to large proteins and synthetic polyamides, such as nylon. As the π∗ peak of the amide bond shrinks, two new π∗ peaks appear at the N 1s edge with a characteristic splitting of 1.

Unoccupied states in Cu and Zn octaethyl-porphyrin and phthalocyanine.

Copper and zinc phthalocyanines and porphyrins are used in organic light emitting diodes and dye-sensitized solar cells. Using near edge x-ray absorption fine structure (NEXAFS) spectroscopy at the Cu 2p and Zn 2p edges, the unoccupied valence states at the Cu and Zn atoms are probed and decomposed into 3d and 4s contributions with the help of density functional calculations. A comparison with the N 1s edge provides the 2p states of the N atoms surrounding the metal, and a comparison with inverse photoemission provides a combined density of states.

Association between interleukin-6 gene promoter -572C/G polymorphism and the risk of sporadic Alzheimer's disease.

Inflammation is a key component of Alzheimer's disease (AD), and we have examined the effect of two polymorphisms (-174G/C and -572C/G) in the promoter of the inflammatory cytokine interleukin-6 (IL-6) gene on risk of AD in 318 AD patients. Significant differences in genotype and allele frequencies of -572C/G IL-6 promoter polymorphism were observed between AD patients and controls. The GG genotype was associated with a decreased risk of developing AD (OR 0.

X-ray absorption spectroscopy of biomimetic dye molecules for solar cells.

Dye-sensitized solar cells are potentially inexpensive alternatives to traditional semiconductor solar cells. In order to optimize dyes for solar cells we systematically investigate the electronic structure of a variety of porphyrins and phthalocyanines. As a biological model system we use the heme group in cytochrome c which plays a role in biological charge transfer processes.

Unusual layer-dependent charge distribution, collective mode coupling, and superconductivity in multilayer cuprate Ba2Ca3Cu4O8F2.

Low energy ultrahigh momentum resolution angle resolved photoemission spectroscopy study on four-layer self-doped high Tc superconductor Ba2Ca3Cu4O8F2 (F0234) revealed fine structure in the band dispersion, identifying the unconventional association of hole and electron doping with the inner and outer CuO2 layers, respectively. For the states originating from two inequivalent CuO2 layers, different energy scales are observed in dispersion kinks associated with the collective mode coupling, with the larger energy scale found in the electron (n-) doped state which also has stronger coupling strength. Given the earlier finding that the superconducting gap is substantially larger along the n-type Fermi surface, our observations connect the mode coupling energy and strength with magnitude of the pairing gap.

Origin of the monochromatic photoemission peak in diamondoid monolayers.

Recent photoemission experiments have discovered a highly monochromatized secondary electron peak emitted from diamondoid self-assembled monolayers on metal substrates. New experimental data and simulation results are presented to show that a combination of negative electron affinity and strong electron-phonon scattering is responsible for this behavior. The simulation results are generated using a simple Monte Carlo transport algorithm.

Near-edge X-ray absorption fine structure spectroscopy of diamondoid thiol monolayers on gold.

Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications.

Anomalous Fermi-surface dependent pairing in a self-doped high-Tc superconductor.

We report the discovery of a self-doped multilayer high Tc superconductor Ba2Ca3Cu4O8F2 (F0234) which contains distinctly different superconducting gap magnitudes along its two Fermi-surface sheets. While formal valence counting would imply this material to be an undoped insulator, it is a self-doped superconductor with a Tc of 60 K, possessing simultaneously both electron- and hole-doped Fermi-surface sheets. Intriguingly, the Fermi-surface sheet characterized by the much larger gap is the electron-doped one, which has a shape disfavoring two electronic features considered to be important for the pairing mechanism: the van Hove singularity and the antiferromagnetic (pi/a, pi/a) scattering.