A 200 W average power, narrow bandwidth, tunable waveguide dye laser

A planar waveguide dye laser, driven by commercial xenon flashlamps with an average power output of 200 W at 50 pulse per second (pps) is described. Due to the planar structure, a narrow bandwidth operation down to 10 GHz has been obtained with a single grating arranged at grazing incidence. With this configuration, high overall efficiency up to 0.6 percent has been obtained, partially due to energy conversion of the broad-band emission spectrum of the flash-lamps by circulating an appropriate dye solution between flashlamps and reflectors.     

The growth morphology of the Ni-rich Ni-Ta-Cr-Mn system

The solidification of an Ni-Ta-Cr-Mn alloy has been investigated for a range of cooling rates and the cellular-to-dendrite transition characterized. The growth directions of the primary and secondary dendrite branches are parallel to 〈100〉. Microsegregation produces a white core in the dendrite interior in some growth conditions.     

Conceptual modeling of data-intensive Web applications

Many of the Web applications around us are data-intensive; their main purpose is to present a large amount of data to their users. Most online trading and e-commerce sites fall into this category, as do digital libraries and institutional sites describing private and public organizations. Several commercial Web development systems aid rapid creation of data-intensive applications by supporting semiautomatic data resource publishing. Automatic publishing is typically subject to the constraints of database schemas, which limit an application designer's choices. Thus, Web application development often requires adaptation through programming, and programs end up intricately mixing data, navigation, and presentation semantics. Presentation is often a facade for elements of structure, composition, and navigation. Despite this frequently unstructured development process, data-intensive applications, based on large data sets organized within a repository or database, generally follow some typical patterns and rules. We describe these patterns and rules using WebML as a conceptual tool to make such notions explicit. WebML is a conceptual Web modeling language that uses the entity-relationship (ER) model for describing data structures and an original, high-level notation for representing Web content composition and navigation in hypertext form.     

Identification of histidine 45 as the axial heme iron ligand of heme oxygenase-2

A truncated, soluble, and enzymatically active form of human heme oxygenase-2 (DeltaHHO2) was expressed in Escherichia coli. To identify the axial heme ligand of HO-2, His-45 to Ala (DeltaH45A) and His-152 to Ala (DeltaH152A) mutants have been prepared using this expression system. DeltaH45A could form a 1:1 complex with hemin but was completely devoid of the heme degradation activity. A 5-coordinate-type ferrous NO EPR spectrum was observed for the heme-DeltaH45A complex. The DeltaH152A mutant was expressed as an inclusion body and was recovered from the lysis pellet by dissolution in urea followed by dialysis. The solubilized fraction obtained, however, was composed of a mixture of a functional enzyme and an inactive fraction. The inactive fraction was removed by Sephadex G-75 column chromatography since it eluted out of the column at the void volume. The gel filtration-purified DeltaH152A exhibited spectroscopic and enzymatic properties identical to those of wild-type. We conclude, in contrast to the previous reports (McCoubrey and Maines (1993) Arch. Biochem. Biophys. 302, 402-408; McCoubrey, W. K., Jr., Huang, T. J., and Maines, M. (1997) J. Biol. Chem. 272, 12568-12574), that His-45, but not His-152, in heme oxygenase isoform-2 is the proximal ligand of the heme and is essential for the heme degradation activity of the enzyme. His-152 appears to play a structural role in stabilization of the heme oxygenase protein.     

On the solution of the polynomial systems arising in the discretization of certain ODEs

We study the positive stationary solutions of a standard finite-difference discretization of the semilinear heat equation with nonlinear Neumann boundary conditions. We prove that, if the diffusion is large enough, then there exists a unique solution of such a discretization, which approximates the unique positive stationary solution of the boundary-value problem under consideration. Furthermore, in this case we exhibit an algorithm computing an ε-approximation of such a solution by means of a homotopy continuation method. The cost of our algorithm is polynomial in the number of nodes involved in the discretization and the logarithm of the number of digits of approximation required. Some of the results presented here were first announced at the IV Congreso Internacional de Matemática Aplicada a la Ingeniería, In-Mat 2008 (Buenos Aires, August 2008) (see [16]).     

Statistical description of optical system performances due torandom coupling on the principal states of polarization

Due to polarization-mode dispersion (PMD), the performances of an optical transmission system show a random behavior. We calculate the probability density function of the Q-factor due to PMD. We adopt the principal states of polarization model, and we also consider the clock recovery behavior at the receiver. Theoretical results are reported for a 40-Gb/s system, and are compared with those obtained considering the effect of pulse broadening due to PMD     

Investigation of passive DMFC mini-stacks at ambient temperature

Two designs of flow fields/current collectors for a passive direct methanol fuel cell (DMFC) monopolar three-cell stack were investigated. The first one (A) consisted of two plastic plates covered by thin gold film current collectors in the area of electrodes with a distribution of holes through which methanol (from a reservoir) and air (from ambient) could diffuse into the electrodes. The second design (B) consisted of thin gold film deposited on the external borders of the fuel and oxidant apertures where the electrodes were placed in contact. A big central hole allowed a direct exposure of electrodes to ambient air (for the cathodes) and methanol solution (for the anodes). An investigation of the performance and discharge behaviour of the two designs was carried out. The advantages and disadvantages of each configuration were analysed. Similar performances in terms of maximum power were recorded; whereas, better mass transport characteristics were obtained with the design B. On the contrary, open circuit voltage (OCV) and stack voltage at low current were higher for the design A as a consequence of lower methanol cross-over. A longer discharge time (17 h) with a unique MeOH charge was recorded with design B at 250 mA compared to the design A (5 h). This was attributed to an easier CO₂ removal from the anode and better mass transport properties.     

Study on the Implementation of Optical Transparent Transport Networks in the European Environment—Results of the Research Project COST 239

Photonic Network Communications -     

The U22 host gene (UHG): chromosomal localization of UHG and distribution of U22 small nucleolar RNA

The U22 host gene (UHG) is very unusual because it encodes a spliced, polyadenylated RNA that has little apparent coding capacity and is rapidly degraded. The stable RNA products from this locus are actually encoded within eight different introns of the UHG pre-RNA. These small nucleolar RNAs (snoRNAs) assemble into ribonucleoproteins, some of which have been shown to function in rRNA processing and modification. In order to more fully characterize the locus, we have mapped UHG to chromosome 11q13 by fluorescence in situ hybridization (FISH). Radiation hybrid mapping placed this sequence-tagged site with very high probability (lod >19) to chromosome 11, approximately 10.1 cR distal to framework marker WI-8652. We also investigated the possibility that the expression of UHG was subject to genomic imprinting. Several laboratories have shown that non-protein-coding mRNAs are frequently associated with imprinted domains in mammalian cells. We used a novel somatic cell hybrid method to assay parent-of-origin effects in the expression of UHG alleles and found that, unlike XIST, IPW, and H19, this RNA is expressed biparentally. Additional FISH experiments using anti-U22 oligonucleotides revealed that, as with U3, this sno-RNA is localized throughout the nucleolus.