Experimental study of a shearing interferometer concept for at-wavelength characterization of extreme-ultraviolet optics

We describe the experimental evaluation of a shearing interferometer concept for at-wavelength testing of extreme-ultraviolet optics. The concept is based on the Ronchi test, which has been modified by a new design for entrance and exit gratings to suppress disturbing higher-order interference patterns. The interferometer concept has been tested on an experimental setup, of which all relevant parameters have been scaled from extreme-ultraviolet to visible-light wavelengths. A Twyman-Green interferometer has been integrated into the setup for comparison with the improved Ronchi test. A systematic difference of 7-12 mlambda rms has been found between wave fronts measured with the improved Ronchi test and with the Twyman-Green interferometer. Possible error sources have been analyzed. The accuracy of the interferometer is estimated to be 10 mlambda rms.     

Blue lasing at room temperature in an optically pumped lattice-matched AlInN=GaN VCSEL structure

Laser action with low threshold average pump power density (~50 W - cm^-2 ) at room temperature is reported for a crack-free planar vertical cavity surface emitting laser (VCSEL) structure based on a bottom lattice-matched AllnN/GaN distributed Bragg reflector (DBR) and a top dielectric DBR. The cavity region, formed by n- and p-type GaN layers surrounding only three InGaN/GaN quantum wells, corresponds to a typical active region suitable for an electrically driven VCSEL. In addition to low threshold, a spontaneous emission coupling factor beta ~ 2 x 10^-10 is derived for this ready-to-be-processed laser structure.     

Effect of the titanium oxide stoichiometry on the efficiency of CO oxidation on the Au/TiOx system surface

Infrared reflection absorption and X-ray photoelectron spectroscopies are used to show that the process of carbon monoxide (CO) oxidation can occur on the surface of a system formed during the appearance of gold clusters on the surface of a titanium oxide layer cooled below room temperature. The efficiency of this process is significantly affected by stoichiometry of the titanium oxide layer. The use of a TiO_x substrate with the stoichiometry different from TiO₂ results in more effective CO oxidation in comparison with the process observed in the Au/TiO₂ system. An important role in the oxidation process is played by the gold-oxide interface.     

Identification and analysis of the plant peroxisomal targeting signal 1 receptor NtPEX5

Protein translocation into peroxisomes takes place via recognition of a peroxisomal targeting signal present at either the extreme C termini (PTS1) or N termini (PTS2) of matrix proteins. In mammals and yeast, the peroxisomal targeting signal receptor, Pex5p, recognizes the PTS1 consisting of -SKL or variants thereof. Although many plant peroxisomal matrix proteins are transported through the PTS1 pathway, little is known about the PTS1 receptor or any other peroxisome assembly protein from plants. We cloned tobacco (Nicotiana tabacum) cDNAs encoding Pex5p (NtPEX5) based on the protein's interaction with a PTS1-containing protein in the yeast two-hybrid system. Nucleotide sequence analysis revealed that the tobacco Pex5p contains seven tetratricopeptide repeats and that NtPEX5 shares greater sequence similarity with its homolog from humans than from yeast. Expression of NtPEX5 fusion proteins, consisting of the N-terminal part of yeast Pex5p and the C-terminal region of NtPEX5, in a Saccharomyces cerevisiae pex5 mutant restored protein translocation into peroxisomes. These experiments confirmed the identity of the tobacco protein as a PTS1 receptor and indicated that components of the peroxisomal translocation apparatus are conserved functionally. Two-hybrid assays showed that NtPEX5 interacts with a wide range of PTS1 variants that also interact with the human Pex5p. Interestingly, the C-terminal residues of some of these peptides deviated from the established plant PTS1 consensus sequence. We conclude that there are significant sequence and functional similarities between the plant and human Pex5ps.     

Lymph node and cutaneous syndrome associated with bone plasmacytoma]

Spinal cavernous haemangiomas are rare and an intradural extramedullary location is rarer still. We give a detailed report of four such cases with a review of 12 cases reported in the past. The clinical presentation, investigations and treatment are discussed.     

Strongyloides stercoralis infection in a non-immunosuppressed tourist with involvement of the central nervous system

In the present case report a 50-year-old woman is presented with a Strongyloides stercoralis infection after a one-month stay in Sri Lanka. She showed a severe involvement of the central nervous system without a correlation of an immunosuppression. Strongyloides stercoralis is regarded as the cause of the cerebral involvement. Other possible causes are also discussed.     

Mechanical behaviour at large strain of polycarbonate nanocomposites during uniaxial tensile test

The present study focuses on the mechanical behaviour of polycarbonate nanocomposites reinforced by alumina or silica nanoparticles at low levels of incorporation. More particularly, we present an experimental approach, specific to large strain measurements by using a Digital Image Correlation (DIC) technique. The mechanical mechanisms involved during uniaxial tensile test of polycarbonate nanocomposites were studied at two-dimensional scales. First, elastic properties of the nanocomposites were determined at macro-homogeneous scale and compared to values obtained by continuum-based elastic micromechanical models. Then the in-plane kinematics measurements at the central part of a double-edge notched sample is analysed locally. The evolution during the test of the volumetric strain and axial strain profiles were studied before and after the yield stress: this analysis revealed the existence of several damage processes during the test up to rupture and put in relief the influence of fillers. Finally, the necking phenomenon was statistically studied and the shape of the neck in terms of strain intensity and localisation was analysed.