Thiophene–phenylene/naphthalene‐based step‐ladder copolymers

A series of step‐ladder copolymers based on thiophene–phenylene–thiophene SL1 ‐ SL3 and thiophene–naphthylene–thiophene SL4 repeat units with varying lengths of the oligothiophene segment has been designed and synthesized via a microwave‐assisted Stille‐type cross‐coupling reaction followed by a polymer‐analogous cyclization reaction. The optical properties of the step‐ladder copolymers have been investigated in detail, in particular at low temperature and in the solid‐state. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7342–7353, 2008     

Discussing the U(1)-Problem of QED2without Instantons

We construct QED₂with mass and flavor and an extra Thirring term. The vacuum expectation values are carefully decomposed into clustering states using the U(1)-axial symmetry of the considered operators and a limiting procedure. The properties of the emerging expectation functional are compared to the proposedθ-vacuum of QCD. The massive theory is bosonized to a generalized Sine–Gordon model (GSG). The structure of the vacuum of QED₂manifests itself in symmetry properties of the GSG. We study the U(1)-problem and derive a Witten–Veneziano-type formula for the masses of the pseudoscalars determined from a semiclassical approximation.     

Photoinduced growth of Cu nanoparticles on ZnO from CuCl<Subscript>2</Subscript> in methanol

Cu nanoparticles were formed on surface of nano-ZnO by UV light induced photoreduction of CuCl₂ in methanol solution suspended with ZnO nanoparticles. By controlling the reaction conditions, the average size of the produced copper nanocrystal can be fine-tuned in the range of 10–200 nm. At constant UV irradiation, the Cu nanocrystals gradually grew up as the initial concentration of copper cation was increased, showing that the in situ formed Cu nanoparticles act as a bridge to facilitate the transferring of photoexcited electrons from ZnO surface to Cu²⁺ in solution. A Redox property was also proved for the Cu nanoparticles.     

In deuterated water the unspecific adsorption of proteins is significantly slowed down: results of an SPR study using model organic surfaces

The control of unspecific adsorption of proteins to natural and technical surfaces plays an important role in biology and also for many applications. Organic model surfaces, e.g., self-assembled monolayers, are often used to identify fundamental surface and/or protein properties that rule protein adsorption. Some techniques involved in biointerface research require the use of heavy water, e.g. neutron scattering techniques. Also in NMR studies D(2)O is the solvent of choice when focusing on biomolecular and hydration dynamics. So far several studies have been concerned with the characterization of the unspecific adsorption of proteins from normal water buffers. In the present work, we report a comparison of the unspecific protein adsorption from normal and heavy water buffers. So far it has been assumed that the surface kinetic of the unspecific adsorption is unaffected by the substitution of water by D(2)O. However, for the four proteins investigated here, this assumption does not hold. The ratio k(H)/k(D) of the adsorption rate constants of the different buffer conditions describe the strength of the isotope effect. We have measured ratios between 1.0 and 2.6, indicating that the adsorption kinetics are strongly affected by a H(2)O-D(2)O substitution.     

MRI-induced stimulation of peripheral nerves: dependency of stimulation threshold on patient positioning

Fast gradient systems enable the imaging of moving organs but also restrict imaging possibilities by stimulating the peripheral nerves. Several studies have determined the stimulation thresholds of the peripheral nerves. However, no study has explicitly examined whether stimulation thresholds are dependent on the position of the patient in the MR imager. In this study, combinations of one, two and three gradient axes were switched with sinusoidal wave forms (rise time 300 micros). Stimulation thresholds were determined for five patient positionings: gradient isocenter at the bridge of the nose, jugular fossa, 10 cm cranial of the umbilicus, umbilicus, and 10 cm caudal of the umbilicus. Experiments were performed in two volunteer groups, one for triple gradient switching (17 male, 14 female) and the other for single and double gradient switching (14 male, 11 female). The dependence of the stimulation threshold on the position of the volunteers in the MR imager was statistically significant for most of the gradient combinations, with the highest stimulation thresholds for positions umbilicus+10 and umbilicus at isocenter. Similar patterns of position dependence were obtained for gradient pairs whose axes were axially symmetric to the human body. Mean stimulation thresholds of male volunteers were lower than those of female volunteers. These findings indicate that stimulation thresholds should be defined according to the position of the patient in the MR scanner.