Improvement of para-selectivity in methylation of toluene on various MFI-type metallosilicate catalysts

MFI-type metallosilicates incorporating various transition metal elements were synthesized by the rapid crystallization method. Compared with H-ZSM-5, these metallosilicates possess fewer acid sites and weaker acidic strength. In the methylation of toluene with methanol, protonated metallosilicates exhibited lower conversion of toluene, higher para-selectivity and higher yield of paraxylene than H-ZSM-5. Distributions of trimethylbenzene and tetramethylbenzene isomers produced in toluene methylation indicate that the effective pore size (openings and/or channels) of metallosilicates may be smaller than that of ZSM-5, which is more advantageous for formation of the smallest isomers in trimethylbenzenes and tetramethylbenzenes. The relation between the paraselectivity in toluene methylation and the isomerization activity in para-xylene conversion suggests that the para-selectivity could occur exclusively, when isomerization of para-xylene to other isomers could be completely prevented. Therefore, the improvement in para-selectivity on MFI-type metallosilicates should be attributed to both the reduction in effective pore size and the decrease of strong acid sites, on which produced para-xylene would be isomerized to ortho- and meta-xylenes.     

Surrogate Constraints Algorithm for Reliability Optimization Problems with Multiple Constraints

This paper presents a surrogate constraints algorithm for solving nonlinear programming, nonlinear integer programming, and nonlinear mixed integer programming problems. The algorithm contains a new technique for generating a succession of vector values of surrogate multiplier (ie, surrogate problems). By using this technique, a computer can keep a polyhedron, which is a vector space of surrogate multipliers to be considered at a certain time, in its memory. Furthermore it can cut the polyhedron by a given hyperplane, and produce the remaining space as the next polyhedron. Simple examples are included.     

Single balanced mixer for SAW front-end module used in 800 MHz cellular radio

A new-type single balanced mixer which satisfies the specifications of E-TACS (extended total access communication system) ultra-wideband cellular radio has been developed. The circuit is constructed with a single ferrite hybrid coil, two GaAs FETs and an IF coil, which provide good spurious-response characteristics for arbitrary intermediate frequencies. Miniaturisation of the front-end module is achieved by using SAW filters and the above mixer.<>     

Evaluation of plume characteristics of arc-heaters with various oxygen injection systems

Arc-heater plumes generated by various oxygen injection systems were investigated by laser absorption spectroscopy. Firstly, oxygen was directly injected into a high-temperature cathode-jet region through a thoriated-tungsten hollow cathode. Although number density of atomic oxygen was increased, erosion of the cathode was too severe to maintain stable discharge. Then, zirconium was used as a cathode material to reduce cathode erosion by oxidation. As a result, stable discharge was maintained for 3 h with pre-mixed argon–oxygen injection and number density of atomic oxygen was successfully increased.     

A simple method for rendering penumbrae caused by sunlight

A simple rendering method for penumbrae caused by sunlight is proposed to create more realistic outdoor scenery. Only four points are used to define the penumbra area cast by a contour edge so that little storage is needed for penumbra areas. Complex penumbrae caused by such objects as curtains can be rendered. Calculation of illumination in the shadows cast by natural objects, such as trees, mapped on a transparent virtual plane is available. In order to show the usefulness of the proposed method, some computer-generated images with penumbrae are compared with those without penumbrae.     

Endothelial cell dysfunction in patients with impaired renal function

In order to investigate endothelial cell dysfunction in patients with impaired renal function, we measured circulating endothelin (ET-1) and thrombomodulin (Tm) concentrations used as markers for endothelial cell injury in patients with renal failure. 1) ET-1 and Tm were significantly higher in patients with renal failure and pre-dialysis patients than in normal subjects. Tm in CRF patients was significantly greater than that in ARF patients. In contrast, ET-1 was significantly greater in ARF than in CRF. 2) A positive correlation was found between serum creatinine concentration (Cr) and Tm in pre-dialysis patients. However, no correlation was found between Cr and ET-1. 3) A positive correlation was found between Tm and the duration of dialysis in HD patients, but not in CAPD patients. 4) With the improvement of renal function after regular HD treatment, a substantial reduction was found in ARF patients in both Tm and ET-1, but not in CRF patients. The present study suggests the presence of endothelial cell dysfunction in patients with impaired renal function. The progression of endothelial cell damage may differ between patients on HD and those on CAPD. In addition, it is suggested that endothelial cell dysfunction reverses in ARF patients with improved renal function.     

Gas barrier changes and morphological alterations induced by retorting in ethylene vinyl alcohol–based food packaging structures

Ethylene vinyl alcohol (EVOH)–based packaging structures were analyzed in terms of both barrier properties and morphological alterations after a retorting process and as functions of ethylene content. From the results, it was found that the samples do have a substantial decrease in oxygen barrier properties and that the kinetics of recovery strongly depends on the copolymer ethylene fraction. A morphological deterioration was also observed as a result of retorting, particularly for packaging structures composed of EVOH copolymers of low ethylene contents. However, the polymer morphology and barrier properties were restored after a dry thermal treatment of the retorted samples. Interestingly, preannealing of copolymers of low ethylene content rendered them more resistant to the retorting process by means of promoting both a more robust crystallinity and a lower water sorption capacity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2192–2202, 2005     

Gigahertz SAW filter developed using new submicrometre techniques

A photolithographic technique was developed that uses 1/10-reduction photoprinting with a phase-shifting mask to make gigahertz SAW devices. Combined with a positive-type resist, this new technique produces IDT electrodes with smaller deviations in width compared with using a negative-type resist. Very sharp 40 nm thick AI electrodes with 0.4 μm lines and spaces were achieved. A 2.5 GHz SAW filter suitable for optical communication systems was developed     

Stereospecifity in radical polymerization of methyl α-(chloromethyl)acrylate

Poly(methyl α-(chloromethyl)acrylate)s (PMCMAs) obtained by homopolymerizations of methyl α-(chloromethyl)acrylate (MCMA) in benzene at different temperatures were converted to poly(methyl methacrylate)s (PMMAs) by reduction with tributyltin hydride. The reduction proceeded smoothly to yield PMMA exhibiting no ¹H NMR resonance due to the CH₂Cl group. The tacticity of the PMCMA obtained at 40 °C was determined using the ¹H NMR resonances of the α-methyl group of PMMA derived: mm/mr/rr=8/56/36. Apparently, the propagation of MCMA preferred r addition to a lower extent in comparison with that of MMA. The more polar and the bulkier α-substituent ClCH₂ (relative to CH₃) would diminish the effect of the carbomethoxy group, thus resulting in a lower level of synditacticity than in MMA polymerization. The tacticity of MMA-MCMA copolymers estimated after conversion to PMMA varied from that of PMMA to that of PMCMA; an increase in MCMA content in the feed resulted in a decrease in rr content. Coisotactic parameters for copolymerization of MCMA with MMA-d₈ were determined according to Hatada's procedure for determination of these parameters [Polym J 19 (1987) 1105].