Comparison between experimental decay of the compound nuclei150Gd and evaporation calculations

The deexcitation of the compound nucleus¹⁵⁰Gd formed by¹⁵⁶O+¹³⁴Ba and⁴⁰Ar+¹¹⁰Pd have been studied. Excitation functions were determined for various exit channels: (HI, × n) withx=3, 4, 5 (HI, pxn) withx=2, 3, 4 (HI, axn) withx=3 and 5. A systematic comparison has been made between these experimental data and the results of evaporation calculation using the ALI CE code. The very good agreement obtained for the total residue cross section disappears completely when a more detailed analysis of the different contributions is performed. Absolute and relative cross sections are not reproduced; excitation functions of each individual channel (HI, 3n), (HI, 4n) etc. ... are not found at the right place in energy. A very preliminary explanation for such a shift towards higher energies is suggested.     

Improvement of the PLD process assisted by RF plasma for AlN growth

The pulsed-laser-deposition (PLD) method is particularly well suited for the growth of oxide thin films, but in the case of other compounds, such as nitrides, PLD presents some limitations which are mainly due to the low reactivity of nitrogen in comparison with oxygen. A possible way to overcome this problem is to increase the reactivity of the constituent species, via plasma assisted-pulsed-laser deposition. A plasma is coupled to the ablation chamber, in order to increase the density of reactive atomic species, which can be further incorporated in the growing film. This approach is described in this paper as well as the nature, energy, and concentration of the atomic and molecular species in the plasma as determined by various plasma diagnostics. These results are correlated to the growth of thin films in the particular case of the aluminum nitride compound. The composition and structure of the films are studied as a function of the growth conditions, and the positive effects of the additional discharge are evidenced on the film purity and properties. The fundamental problem with the PLD technique, especially with metallic targets, is the production of unwanted droplets that significantly worsen the properties of the films. To eliminate these droplets, a thin film has been grown with an experimental setup using two targets and crossed laser beams which gave positive results. PACS 81.15.Fg; 52.80.Pi; 77.84.Bw     

Morphology and microstructure of all-epitaxial ferroelectric tri-layered (Bi,La)4Ti3O12/Pb(Zr0.4Ti0.6)O3/ (Bi,La)4Ti3O12 thin films on SrTiO3(011)

The morphology and microstructure of all-epitaxial (Bi,La)₄Ti₃O₁₂/Pb(Zr_0.4Ti_0.6)O₃/(Bi,La)₄Ti₃O₁₂ (BLT/PZT/BLT) tri-layered ferroelectric films, grown on (011)-oriented SrTiO₃ (STO) substrates by pulsed laser deposition, are investigated by transmission electron microscopy (TEM). X-ray diffraction and electron diffraction patterns demonstrate that the epitaxial relationship between BLT, PZT and STO can be described as ; . Cross-sectional TEM images show that the growth rate of BLT is nearly two times that for PZT at the same growth conditions, and 90° ferroelectric domain boundaries lying on {110} planes are observed in the PZT layer. The 90° ferroelectric domains in the PZT layer extend up to 600 nm in length. Long domains penetrate into the neighboring columnar grain through the columnar grain boundary, whereas others are nucleating at the columnar grain boundaries. The roughness of the PZT/BLT interfaces appears to depend on the viewing direction, i.e., it is different for different azimuthal directions. Planar TEM investigations show that the grains in the top BLT layer have a rod-like morphology, preferentially growing along the [110]_BLT direction. The grain width is rather constant at about 90 nm, whereas the length of the grains varies from 150 to 625 nm. These morphological details point to the important role the crystal anisotropy of BLT plays for the growth and structure of the tri-layered films. PACS 81.15-z; 68.37.Lp; 77.84.-s     

High Probe Intensity Photobleaching Measurement of Lateral Diffusion in Cell Membranes

Lateral diffusion measurements, most commonly accomplished through Fluorescence Photobleaching Recovery (FPR or FRAP), provide important information on cell membrane molecules' size, environment and participation in intermolecular interactions. However, serious difficulties arise when these techniques are applied to weakly expressed proteins of either of two types: fusions of membrane receptors with visible fluorescent proteins or membrane molecules on autofluorescent cells. To achieve adequate sensitivity in these cases, techniques such as interference fringe FPR are needed. However, in such measurements, cytoplasmic species contribute to the fluorescence recovery signal and thus yield diffusion parameters not properly representing the small number of surface molecules. A new method helps eliminate these difficulties. High Probe Intensity (HPI)-FPR measurements retain the intrinsic confocality of spot measurements to eliminate interference from fluorescent cytoplasmic species. However, HPI-FPR methods lift the previous requirement that FPR procedures be performed at probe beam intensities low enough to not induce bleaching in samples during measurements. The high probe intensities now employed provide much larger fluorescence signals and thus more information on molecular diffusion from each measurement. We report successful measurement of membrane dynamics by this technique.     

How to reduce the experimental time in isotopic 2H NMR using the ERETIC method

Deuterium site-specific natural isotope abundance (Ai) is routinely measured by NMR spectroscopy and quantified using an internal reference peak. This study demonstrates that the substitution of the chemical compound used as internal reference by an electronically generated signal (the ERETIC method) allows a dramatic reduction of the experimental time. Measurements of Ai on eight samples of methylsalicylate have been performed using either an internal reference (TMU) or ERETIC. No significant difference in accuracy or precision had been found between the two methods. However, because the method is applicable in partially saturated conditions, the experiment time was divided by a factor of 4 and the drawbacks associated with an internal chemical reference were avoided when ERETIC was used.     

Solution-phase parallel synthesis of a 1140-member ureidothiophene carboxylic acid library

A 1140-library of thiophene ureidoacids was synthesized by the reaction of a set of 60 primary or secondary amines with a number of 19 thieno[3,2-d]- or thieno[2,3-d][1,3]oxazine-2,4-diones. All compounds were obtained by a simple solution-phase combinatorial strategy on a 200-400-mg scale with over 70% yields and purities over 80%. Sixty library members chosen at random were successfully characterized by standard 1H NMR, HPLC/MS, and IR studies. Analgesic, antalgic, and antiinflammatory potential were investigated. The 1140-member ureidothiophene carboxylic acid library will be used in high-throughput screening assays.