Electrochemical reduction of the iodinated contrast medium iomeprol: iodine mass balance and identification of transformation products.

Potentiostatic-controlled electrochemical reduction of iomeprol was used to deiodinate iomeprol (IMP), a representative of the iodinated X-ray contrast media. The reduction process was followed by product analysis with liquid chromatography-electrospray ionization-tandem mass spectrometry and ion chromatography-inductively coupled plasma-mass spectrometry. The identification is mainly based on the interpretation of the mass fragmentation.

Gold helix photonic metamaterial as broadband circular polarizer.

We investigated propagation of light through a uniaxial photonic metamaterial composed of three-dimensional gold helices arranged on a two-dimensional square lattice. These nanostructures are fabricated via an approach based on direct laser writing into a positive-tone photoresist followed by electrochemical deposition of gold. For propagation of light along the helix axis, the structure blocks the circular polarization with the same handedness as the helices, whereas it transmits the other, for a frequency range exceeding one octave.

Discontinuous Galerkin time-domain computations of metallic nanostructures.

We apply the three-dimensional Discontinuous-Galerkin Time-Domain method to the investigation of the optical properties of bar- and V-shaped metallic nanostructures on dielectric substrates. A flexible finite element-like mesh together with an expansion into high-order basis functions allows for an accurate resolution of complex geometries and strong field gradients. In turn, this provides accurate results on the optical response of realistic structures.

Strong optical activity from twisted-cross photonic metamaterials.

Following a recent theoretical suggestion and microwave experiments, we fabricate photonic metamaterials composed of pairs of twisted gold crosses using two successive electron-beam-lithography steps and intermediate planarization via a spin-on dielectric. The resulting two effective resonances of the coupled system lie in the 1-2 microm wavelength regime and exhibit pronounced circular dichroism, while the circular polarization conversion is very small. In between the two resonances, we find a fairly broad spectral regime with strong optical activity, i.

Unexpected Trimerization of Pyrazine in the Coordination Sphere of Low-Valent Titanocene Fragments.

The titanium mediated trimerization of pyrazine leads to the formation of a tris-chelate complex employing a 4a,4b,8a,8b,12a,12b-hexahydrodiyprazino[2,3-f:2',3'-h]quinoxaline ligand (HATH6, 3). The driving force in the formation of the (Cp*2Ti)3(HATH6) complex 2 is attributed to the formation of six Ti-N bonds. We show that density functional theory (DFT) fails to predict quantitatively correct results.

Magnetic anisotropy and magnetization dynamics of individual atoms and clusters of Fe and Co on Pt(111).

The recently discovered giant magnetic anisotropy of single magnetic Co atoms raises the hope of magnetic storage in small clusters. We present a joint experimental and theoretical study of the magnetic anisotropy and the spin dynamics of Fe and Co atoms, dimers, and trimers on Pt(111). Giant anisotropies of individual atoms and clusters as well as lifetimes of the excited states were determined with inelastic scanning tunneling spectroscopy.

Efficiency of timing delays and electrode positions in optimization of biventricular pacing: a simulation study.

Electrode positions and timing delays influence the efficacy of biventricular pacing (BVP). Accordingly, this study focuses on BVP optimization, using a detailed 3-D electrophysiological model of the human heart, which is adapted to patient-specific anatomy and pathophysiology. The research is effectuated on ten heart models with left bundle branch block and myocardial infarction derived from magnetic resonance and computed tomography data.

Accurate coupled cluster calculations of the reaction barrier heights of two CH3* + CH4 reactions.

We have computed barrier heights of 71.8 +/- 2.0 and 216.

Formation of bromoform in irradiated titanium dioxide suspensions with varying photocatalyst, dissolved organic carbon and bromide concentrations.

We report the formation of bromoform in TiO(2) suspensions (P25) under simulated solar UV irradiation at different concentrations of photocatalyst (0.5-1.5 g L(-1)) as well as initial concentrations of bromide ions (1-3mg L(-1)) and 2,4-dihydroxybenzoic acid (2-10mg L(-1)).

Near-field optical study of protein transport kinetics at a single nuclear pore.

The kinetics of proteins passing through individual nuclear pore complexes (NPCs) of the nuclear envelope (NE) was studied using near-field scanning optical microscopy (NSOM) in combination with fluorescence correlation spectroscopy (FCS). The NSOM probe was placed over a single pore in an unsupported native NE to observe fluorescence-labeled NTF2 moving in the transport channel. A correlation analysis of the arising fluorescence fluctuations enabled us to characterize the translocation as driven by Brownian motion and to determine the related kinetic constants.

{Ge9R3Cr(CO)5}- and {Ge9R3Cr(CO)3}-: a metalloid cluster (Ge9R3-) as a flexible ligand in coordination chemistry [R=Si(SiMe3)3].

The reactions of the metalloid cluster {Ge9[Si(SiMe3)3]3}- with Cr(CO)5COE (COE=cyclooctene) and Cr(CO)3(CH3CN)3 lead to the new cluster compounds {Ge9[Si(SiMe3)3]3Cr(CO)5}- and {Ge9[Si(SiMe3)3]3Cr(CO)3}-, whose structural and electronic properties are presented.

Systematic studies using 2-(1-adamantylethynyl)pyrimidine-5-carbaldehyde as a starting material in Soai's asymmetric autocatalysis.

Herein, we present a new substrate for the Soai reaction, which has an adamantylethynyl residue (1 g) and exhibits asymmetric autocatalysis, yielding products with enantiomeric excesses above 99%. For the first time, all reactions were performed on a parallel synthesizer system to ensure identical reaction conditions. A detailed systematic study of reaction parameters was performed and we report the highest enhancements of enantiomeric excess reported so far in the Soai reaction in one reaction cycle (7.

Laser speckle reduction via colloidal-dispersion-filled projection screens.

We use projection screens filled with colloidal dispersions to reduce laser speckle in laser projection systems. Laser light is multiply scattered at the globules of the colloidal dispersion's internal phase, which do Brownian movement. The integration time of the human eye causes a perception of a reduced laser speckle contrast because of temporal averaging.

Photodissociation dynamics of IrBr6(2-) dianions by time-resolved photoelectron spectroscopy.

We have used femtosecond time-resolved photoelectron spectroscopy to examine the photodissociation dynamics of doubly charged anions IrBr(6)(2-) after excitation at h nu(pump) = 1.6 eV and with a detachment photon energy of h nu(probe) = 4.8 eV.

Hydrides and dimers of C(58) fullerenes: structures and stabilities.

A density functional theory (DFT) study of fullerene hydrides C(58)H(2x) (2x = 2,4,...

Cadherin-11 regulates protrusive activity in Xenopus cranial neural crest cells upstream of Trio and the small GTPases.

Xenopus Cadherin-11 (Xcad-11) is expressed when cranial neural crest cells (CNC) acquire motility. However, its function in stimulating cell migration is poorly understood. Here, we demonstrate that Xcad-11 initiates filopodia and lamellipodia formation, which is essential for CNC to populate pharyngeal pouches.

A simple simulation of the degradation of natural organic matter in homogeneous and heterogeneous advanced oxidation processes.

The degradation of natural organic matter (NOM) in homogeneous and heterogeneous advanced oxidation processes (AOP) was simulated using a simple underlying physical model. By treating the NOM molecules as linear chains and allowing them to be cleaved at any point selected at random, it is possible to reproduce well the results for homogeneous AOP experiments. To simulate a heterogeneous process, a bias was introduced (in the form of different weights for different chain lengths) according to literature data on the adsorption of NOM onto TiO(2) nanoparticle agglomerates.

Source identification of sulphate forming salts on sandstones from monuments in Salamanca, Spain--a stable isotope approach.

Background, Aim And Scope: Salt efflorescences markedly contribute to the alteration and deterioration of building material, in this case the Villamayor Sandstone of the facades in the Old Town of Salamanca, Spain (United Nations Educational, Scientific and Cultural Organization world cultural heritage site). A better understanding of the mechanisms of salt formation and the involved elements would allow more precise measures in monument conservation. The magnesium which is required for the salt precipitation originates from selective processes of hydrolysis.

Coupling effects in low-symmetry planar split-ring resonator arrays.

We introduce a particular low-symmetry (point group of unit cell C(1)) planar periodic arrangement of magnetic split-ring resonators that acts as an effective optical wave plate. We show that this behavior specifically results from the in-plane interactions among the individual split-ring resonators. Measured normal-incidence transmittance and conversion spectra of gold-based samples fabricated via electron-beam lithography show fundamental resonances at around 235 THz frequency (1,275 nm wavelength) that are in good agreement with theory.

Microalgae and terrestrial biomass as source for fuels--a process view.

Due to increasing oil prices and climate change concerns, biofuels have become more important as potential alternative energy sources. It is an open question which kind of biofuels with which yield potentials, characteristic properties and environmental consequences should give the largest contributions. Microalgae offer novel aquatic biomass systems with higher fuel yield potential and lower water demand than terrestrial biomass.

Catalytic hydroaminoalkylation.

Excellent couplings: Recent developments in the metal-catalyzed C-H activation of sp(3) centers in an alpha position relative to an amine nitrogen atom are presented. Their reaction with alkenes to give alkylamines (hydroaminoalkylation) is also summarized (see general scheme).

Two base pair duplexes suffice to build a novel material.

Tetrahedral DNA hybrids with tetrakis(p-hydroxyphenyl)methane cores hybridize in a sequence-specific fashion at much higher temperatures than isolated linear duplexes. Dinucleotide DNA arms suffice to induce the formation of a solid at room temperature; this demonstrates the strength of multivalent binding. The graphic shows a view of a modeled assembly.

[Patient safety in medical technology research].

The message of this article is that patient safety must be an essential part of thinking and planning in research for medical technology. Which aspects must be considered already in an early phase of any project are presented. The most important standards are listed briefly.

Design of Experiment (DoE) as a Tool for the Optimization of Source Conditions in SEC-ESI-MS of Functional Synthetic Polymers Synthesized via ATRP.

Design of experiment (DoE) is applied to establish the optimum ionization conditions for analyzing synthetic polymers via coupled size exclusion chromatography electrospray ionization mass spectrometry (SEC-ESI-MS) yielding maximum ionization efficiency. The ion source conditions were optimized with regard to the ionization efficiency, the amount of fragmentation, as well as the formation of salt adducts. A D-optimal experimental design was employed for this purpose and the recorded data were evaluated by a quadratic response surface model, accounting for possible interactions between the individual source settings.