The anomalous 3-boson couplings as an implication of the Higgs sector

We discuss the possible new electroweak interactions which may be generated by the Higgs sector at the scale of theZ mass. For this purpose, we give a set ofSU(2)×U(1) gauge invariant operators constructed in terms ofW, Z, γ and Higgs fields which in the unitary gauge describe all possible γWW andZWW anomalous couplings. The dimension of these operators varies from 6 to 12. This fact allows us to consider various scenaria for the manifestations of the New Physics. We conclude that the underlying dynamics induced by the Higgs sector can be tested through a model-independent amplitude analysis of gauge boson pair production at LEP2 and future colliders.     

Effects of strong coupling in homonuclear correlation spectroscopy

A calculation of the complex signals in homonuclear correlation spectra (HOMCOR) of strongly coupled ABX three-spin systems is presented. It is shown that the presence of strong coupling causes the behavior of the cross-peaks to differ significantly from that found in the case of weak coupling. Two classes of connectivity patterns, namely weak and strong connectivity pairs of transitions are distinguished. Closed expressions for the real amplitudes are given. The dependence of the real amplitude on the flip angle of the mixing pulse and on the coupling strength is analyzed.     

Experimental study of a plasma-filled backward wave oscillator

Experimental studies of a plasma-filled X-band backward-wave oscillator (BWO) are presented. Depending on the background gas pressure, microwave frequency upshifts of up to 1 GHz appeared along with an enhancement by a factor of 7 in the total microwave power emission. The bandwidth of the microwave emission increased from ⩽0.5 GHz to 2 GHz when the BWO was working at the RF power enhancement pressure region. The RF power enhancement appeared over a much wider pressure range in a high beam current case (10-100 mT for 3 kA) than in a lower beam case (80-115 mT for 1.6 kA). The plasma-filled BWO has higher power output than the vacuum BWO over a broader region of magnetic guide field strength. Trivelpiece-Gould modes (T-G modes) are observed with frequencies up to the background plasma frequency in a plasma-filled BWO. Mode competition between the T-G modes and the X-band Tm₀₁ mode prevailed when the background plasma density was below 6×10¹¹ cm^-3 . At a critical background plasma density of ≃8×10¹¹ cm^-3 power enhancement appeared in both X-band and the T-G modes. Power enhancement of the S-band in this mode collaboration region reached up to 8 dB. Electric fields measured by the Stark-effect method were as high as 34 kV/cm while the BWO power level was 80 MW. These electric fields lasted throughout the high-power microwave pulse     

A common motif in G-protein-coupled seven transmembrane helix receptors

Summary G-protein-coupled receptors all share the seven transmembrane helix motif similar to bacteriorhodopsin. This similarity was exploited to build models for these receptors. From an analysis of a multi-sequence alignment of 225 G-protein-coupled receptors belonging to the rhodopsin-like superfamily, conclusions could be drawn about functional residues. Seven residues in the transmembrane regions are conserved throughout all aligned receptors. These residues cluster at the cytosolic side of the transmembrane helices and are for all rhodopsin-like G-protein-coupled receptors implied in signal transduction. An analysis of correlated mutations reveals a number of residues, both in the helices and in the cytosolic loops, that might be important in the signal transduction pathway in subfamilies of this receptor family.     

EPMA of interfaces applied to the solid oxide fuel cell

Chemical interactions at the phase boundaries of materials applied for the solid oxide fuel cell (SOFC) have been studied by EPMA. The chemical reactivity at the interface of La_y-xSr_xMnO₃/ZrO₂-Y₂O₃ is dependent on the stoichiometry (y) and the Sr content (x) of the perovskite. Typical reaction products (zirconates) and a diffusion zone in the ZrO₂–Y₂O₃ have been observed. The extension of cation release (Mn) is related to the increasing chemical activity of Mn oxide in the perovskite by the Sr substitution for La. The wettability of the metal/oxide interface in the anode cermet (Ni/ZrO₂–Y₂O₃) has been found to be influenced by chemical reactions resulting from the applied reducing atmosphere with high carbon activity. The disintegration of ZrO₂–Y₂O₃ in contact with molten Ni or Ni-Ti and Ni-Cr alloys leads to the redeposition of Y₂O₃-enriched oxides and also to Zr-rich intermetallic compounds and eutectics.     

Observation of ionic thermocurrents in zirconia-based solid electrolytes

In ionic conductors, long range-migrating charges are a main cause of polarization processes. This has complicated, up to date, the study of ionic thermocurrents (ITC) in solid electrolytes. However, the method is appealing, as it probes directly charge-formation phenomena that are important both from a scientific point of view and for applications. This work reports on the observation of ITC in solid electrolytes. Under appropriate experimental conditions, the ITC response of a zirconia sample electroded with platinum is a reproducible one, thus opening the way to a new characterization method that may complement other well established methods, such as Impedance Spectroscopy and a number of electrochemical techniques. The general trends of the response, which is composed of two well resolved ITC peaks, is discussed. One of them, taking place at higher temperatures, conforms to the standard shape of a first order kinetics depolarization process. Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995     

Laser writing techniques for photomask fabrication using a femtosecond laser

Photomasks are the backbone of microfabrication industries. Currently they are fabricated by a lithographic process, which is very expensive and time consuming since it is a multi-step process. These issues can be addressed by fabricating photomasks by direct femtosecond laser writing, which is a single-step process and comparatively cheaper and faster than lithography. In this paper we discuss our investigations on the effect of two types of laser writing techniques, namely front- and rear-side laser writing, with regard to the feature size and the edge quality of a feature. It is proved conclusively that for the patterning of masks, front-side laser writing is a better technique than rear-side laser writing with regard to smaller feature size and better edge quality. Moreover the energy required for front-side laser writing is considerably lower than that for rear-side laser writing. Received: 22 May 2001 / Accepted: 14 September 2001 / Published online: 17 October 2001     

Dynamic scanning force microscopy study of self-assembled DNA-protein nanostructures

Self-assembled oligomeric nanostructures consisting of bisbiotinylated DNA fragments connected by the protein streptavidin (STV) are studied by dynamic scanning force microscopy (SFM) operating in air. A comparison of the images taken in repulsive and attractive regimes is systematically made on DNA and STV structures. Stable and reproducible SFM images are obtained in the attractive regime by using a special feedback circuit, called Q-control. On the other hand, when SFM is operating in the repulsive regime, deformation of the structures that reduce the resolution and the image quality are clearly observable. The heights of both DNA and STV have been measured as a function of the tip/molecule interaction forces. This study offers the possibility to suggest a different mechanical behavior of DNA with respect to STV. Received: 24 July 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002