The N = Z nucleus 76 Sr: Gamow-Teller strength and nuclear deformation

Challenged by recent theoretical work, a study of the -EC decay of the N = Z even-even nucleus ⁷⁶ Sr has been undertaken in order to assign the parent ground-state deformation. In this study 13 levels with have been located in ⁷⁶ Rb. The beta-delayed proton emission has been observed for the first time in an N = Z even-even nucleus. The p branching ratio has been determined to be . The ⁷⁶ Sr half-life has been remeasured and a more precise value of s has been obtained. On the basis of the comparison of measured Gamow-Teller strength with calculated strength distributions for both oblate and prolate deformation, it is concluded that the ⁷⁶ Sr has strong prolate deformation in the ground state.Received: 26 June 2003, Revised: 5 November 2003, Published online: 18 June 2004PACS: 21.10.Hw Spin, parity, and isobaric spin - 23.20.Lv transitions and level energies - 23.40.Hc Relation with nuclear matrix elements and nuclear structure - 27.50. + e J. Giovinazzo: Present address: Centre d Etudes Nucléaires de Bordeaux-Gradignan, Le Haut Vigneau, F-33175 Gradignan Cedex, France.M. Ramdhane: Present address: University Mentouri, 25000 Constantine, Algeria.     

A nanoscale dendrimer-based Fe24 cluster: synthesis and molecular self-assembly

We report the synthesis, characterisation and self-assembly of a nanoscopic Fe24 cluster using an organic dendrimer as a molecular substrate for building up well-defined molecular nanostructures.     

The REX-ISOLDE project

The Radioactive Beam Experiment REX-ISOLDE [1–3] is a pilot experiment at ISOLDE (CERN) testing the new concept of post acceleration of radioactive ion beams by using charge breeding of the ions in a high charge state ion source and the efficient acceleration of the highly charged ions in a short LINAC using modern ion accelerator structures. In order to prepare the ions for the experiments singly charged radioactive ions from the on-line mass separator ISOLDE will be cooled and bunched in a Penning trap, charge bred in an electron beam ion source (EBIS) and finally accelerated in the LINAC. The LINAC consists of a radiofrequency quadrupole (RFQ) accelerator, which accelerates the ions up to 0.3 MeV/u, an interdigital H-type (IH) structure with a final energy between 1.1 and 1.2 MeV/u and three seven gap resonators, which allow the variation of the final energy. With an energy of the radioactive beams between 0.8 MeV/u and 2.2 MeV/u a wide range of experiments in the field of nuclear spectroscopy, astrophysics and solid state physics will be addressed by REX-ISOLDE. This revised version was published online in July 2006 with corrections to the Cover Date.     

Simultaneous Quantification of Neomycin and Bacitracin by LC-ELSD

The first simultaneous quantification of neomycin and bacitracin using liquid chromatography evaporative light scattering detection as an alternative to MS detection and pre-/post-column derivatisation, respectively, was the aim of this study. The developed method was validated for two strength of neomycin and one strength of bacitracin in sterile pharmaceutical formulation and is a fast and efficient tool for content uniformity tests in quality control. With this method the separation of neomycin from sulfate and the base line separation of the four major components of bacitracin (bacitracin A, B1, B2 and B3) was achieved. These four components are responsible for 96% of the microbiological activity. A Phenomenex Synergi POLAR analytical column (250 mm × 4.6 mm, 4 μm I.D.) in combination with 0.5% perfluoropropionic acid and acetonitrile in gradient mode, the peaks of interest could be separated with high efficiency within 14 min. The calibration was performed using a second order regression with an R ² = 0.9999 for neomycin (B and C) sulfate and R ² = 0.9996 for bacitracin A, B1, B2 and B3. The results of the accuracy evaluation were 99.2 and 99.7%, respectively, for neomycin and 100.8% for bacitracin. Injection precision results are 0.4–1.5 RSD% recorded for six injections. The established method has a high potential for routine high-throughput analyses in the pharmaceutical industry.     

Controlled coupling of a single nitrogen-vacancy center to a silver nanowire

We report on the controlled coupling of a single nitrogen-vacancy (NV) center to a surface plasmon mode propagating along a chemically grown silver nanowire (NW). We locate and optically characterize a single NV center in a uniform dielectric environment before we controllably position this emitter in the close proximity of the NW. We are thus able to control the coupling of this particular emitter to the NW and directly compare the photon emission properties before and after the coupling. The excitation of single plasmonic modes is witnessed and a total rate enhancement by a factor of up to 4.6 is demonstrated.     

Catalyst patterning methods for surface-bound chemical vapor deposition of carbon nanotubes

We present three different catalyst preparation and patterning techniques for plasma-enhanced chemical vapor deposition of carbon nanostructures from acetylene and ammonia mixtures. The different merits and potential areas of application are highlighted for each technique as compared to the benchmark of e-beam-lithography patterning. Maskless, focused ion beam written Pt can nucleate aligned carbon nanofibers, thereby allowing a sub-100 nm lateral resolution on non-planar substrate geometries combined with an in-situ monitoring. Ion beam milling additionally enables the pre-shaping and marking of the substrate, which is shown for the growth of individual nanofibers on the apex of commercial scanning probe tips. Pulsed electrochemical deposition was used to form Ni and Fe catalyst islands of controlled size and density. This is also demonstrated on complex substrate geometries such as carbon cloth. Nanocontact printing was employed to deposit a highly purified Co colloid in regular patterns with feature sizes down to 100 nm onto silicon wafers for low cost patterning over large areas. We analyze the catalyst restructuring upon exposure to elevated temperatures for each technique and relate this to the nucleated nanofiber dimensions and array densities. The flexibility in catalyst and substrate material allows a transfer of our achievements to catalyst-assisted growth of nanostructures in general facilitating their hierarchical device integration and future application. PACS 81.16.Rf; 81.16.Hc; 61.46.+w     

Topography printing to locally control wettability

This paper reports a new patterning method, which utilizes NaOH to facilitate the irreversible binding between the PDMS stamp and substrates and subsequent cohesive mechanical failure to transfer the PDMS patterns. Our method shows high substrate tolerance and can be used to "print" various PDMS geometries on a wide range of surfaces, including Si100, glass, gold, polymers, and patterned SU8 photoresist. Using this technique, we are able to locally change the wettability of substrate surfaces by printing well-defined PDMS architectures on the patterned SU8 photoresist. It is possible to generate differential wetting and dewetting properties in microchannels and in the PDMS printed area, respectively.     

Analysis of carbohydrates using different quaternized polystyrene-divinylbenzene particles and pulsed amperometric detection

Summary This paper reports on the use of a polymer-based, strong anion-exchange stationary phase for rapid, selective and sensitive analysis of physiological important mono-, di- and oligosaccharides by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) under alkaline conditions. The adsorbent was obtained by direct nitration of 3 and 5 μm, spherical non-porous highly cross-linked, styrene-divinylbenzene copolymer (PS-DVB) beads, followed by reduction of superficially introduced nitro groups with nascent hydrogen and quaternization of the resultant amino groups with iodomethane. Extended exposure to high pressure and strong alkaline conditions did not have any untoward effect on mechanical stability and chromatographic performance. A comparison of the 3 and 5 μm beads showed, that the synthesized 3 μm highly cross-linked PS-DVB particles are the preferred phases for the separation of monosaccharides and the 5 μm particles are preferable for the separation of oligosaccharides. To demonstrate the suitability for the analysis of complex samples, the optimized and validated system was used for the determination of glucose, fructose and sucrose in apple juice and other soft drinks such as Coca Cola. Finally, analysis within a few minutes without sample pretreatment down to a lower limit of detection of 0.174–0.504 μg mL⁻¹ at a linearity with R²>0.994 and a repooducibility higher than 98% further confirmed the efficiency of these polymeric sorbents.