Photocatalytic Activity of Metalloporphyrin–Titanium Mixtures in Microemulsions

This report explores the photocatalytic activity of TiO₂, Ti(IV) citrate and Zn(II) tetraphenyl porphyrin (ZnTPP) and its mixtures in water/oil (W/O) and O/W microemulsion (μE). The 4-chlorophenol was used to assess the efficiency of the photoactive compounds in a degradation process. A simple photoelectrochemical study based on cyclic voltammetry was also developed. The results revealed that most of the photocatalytic procedures developed are effective in the degradation process. However, phenol was the major product obtained.     

A GC-based method for high-throughput screening of enantioselective catalysts

By combining two gas chromatography instruments (each containing a column with a chiral stationary phase) with the proper robotics and software, it is possible to construct an instrumental configuration which makes possible high-throughput screening of the enantioselectivity of a given catalytic reaction. As an example, the acylation-based catalytic kinetic resolution of racemic 2-phenyl-1-propanol catalyzed by mutant lipases can be about assayed, 700 exact E- and ee-determinations being possible per day. The method is, therefore, of interest in the directed evolution of enantioselective enzymes and/or in the combinatorial search for asymmetric transition metal catalysts.     

Reproducibility of continuous arterial spin labeling perfusion MRI after 7 weeks

Background Continuous arterial spin labeling (CASL) is a non-invasive technique for the measurement of cerebral blood flow (CBF). The aim of the present study was to examine the reproducibility of CASL measurements and its suitability to consistently detect differences between groups, regions, and resting states. Materials and methods Thirty-eight healthy subjects (19 female) were examined at 1.5 T on two measurement occasions that were seven weeks apart. Resting CBF was measured with eyes open and eyes closed. Results In different regions of interest (ROIs) the repeatability estimates varied between 9 and 19 ml/100 g/min. There were no significant mean differences between occasions in all ROIs (P > 0.05). Greater CBF in the eyes-open than in the eyes-closed state was consistently present in the primary and secondary visual areas. Furthermore, CBF was consistently greater in the right than in the left hemisphere (P < 0.05) and differed between lobes and between arterial territories (P < 0.001). Finally, we consistently observed greater CBF in women than in men (P < 0.001). Conclusion This study demonstrates the suitability of CASL to consistently detect differences between groups, regions, and resting states even after seven weeks. This emphasizes its usefulness for longitudinal designs.     

Algebraic solution of transcritical carbon dioxide flow through adiabatic capillary tubes

This paper outlines an algebraic model for simulating the transcritical expansion of carbon dioxide through adiabatic capillary tubes. The model was put forward based on the analytical solution of the momentum conservation equation assuming an isenthalpic expansion process. The theoretical model predictions were compared with 66 experimental data points covering different operating conditions and tube geometries. A good agreement between the experimental and calculated mass flow rates was achieved, with more than 94% of the data points lying within an error band of ±10%.     

A Metropolis algorithm combined with Nelder–Mead Simplex applied to nuclear reactor core design

A hybridization of the recently introduced Particle Collision Algorithm (PCA) and the Nelder–Mead Simplex algorithm is introduced and applied to a core design optimization problem which was previously attacked by other metaheuristics. The optimization problem consists in adjusting several reactor cell parameters, such as dimensions, enrichment and materials, in order to minimize the average peak-factor in a three-enrichment-zone reactor, considering restrictions on the average thermal flux, criticality and sub-moderation. The new metaheuristic performs better than the genetic algorithm, particle swarm optimization, and the Metropolis algorithms PCA and the Great Deluge Algorithm, thus demonstrating its potential for other applications.     

Stromelysin-1: three-dimensional structure of the inhibited catalytic domain and of the C-truncated proenzyme

The proteolytic enzyme stromelysin-1 is a member of the family of matrix metalloproteinases and is believed to play a role in pathological conditions such as arthritis and tumor invasion. Stromelysin-1 is synthesized as a pro-enzyme that is activated by removal of an N-terminal prodomain. The active enzyme contains a catalytic domain and a C-terminal hemopexin domain believed to participate in macromolecular substrate recognition. We have determined the three-dimensional structures of both a C-truncated form of the proenzyme and an inhibited complex of the catalytic domain by X-ray diffraction analysis. The catalytic core is very similar in the two forms and is similar to the homologous domain in fibroblast and neutrophil collagenases, as well as to the stromelysin structure determined by NMR. The prodomain is a separate folding unit containing three alpha-helices and an extended peptide that lies in the active site of the enzyme. Surprisingly, the amino-to-carboxyl direction of this peptide chain is opposite to that adopted by the inhibitor and by previously reported inhibitors of collagenase. Comparison of the active site of stromelysin with that of thermolysin reveals that most of the residues proposed to play significant roles in the enzymatic mechanism of thermolysin have equivalents in stromelysin, but that three residues implicated in the catalytic mechanism of thermolysin are not represented in stromelysin.     

New reflective type star couplers for full duplex channels

A new reflective-type singlemode fibre-optic passive star coupler is described. For this new type of coupler, power entering any one of the ports is divided to all ports except the input port, and thus the optical signal is prevented from returning to its own source.<>