Deactivation of copper-ion-exchanged hydrogen-mordenite-type zeolite catalyst by SO2 for no reduction by NH3

Deactivation of copper-ion-exchanged hydrogen-mordenite-type zeolite catalyst by SO₂ for NO reduction by NH₃ was examined in a fixed-bed flow reactor. The deactivation of the catalyst was strongly dependent on reaction temperature. At high reaction temperatures over 300°C, the catalyst did not lose its initial activity up to 50 h of operation, regardless of SO₂ feed concentration from 500 to 20,000 ppm. However, at low reaction temperatures near 250°C, apparent deactivation did occur. Changes in the physicochemical properties such as surface area and sulfur content of deactivated catalyst well correlated with catalyst activity, depending upon reaction temperatures. The deactivation was due to pore blocking and/or filling by deactivating agents, which plugged and/or filled the pores of catalyst. The deactivating agents deposited on the catalyst surface were presumed to be (NH₄)₂SO₄ and/or (NH₄)HSO₄ from the results of TGA and ion-chromatography measurement.     

Epitaxial growth of GaN on (0001) Al<Subscript>2</Subscript>O<Subscript>3</Subscript> via solution-cast seed layer formation process using Ga(mDTC)<Subscript>3</Subscript>

This paper reports an alternative method for the growth of GaN epitaxial layer on (0001) Al₂O₃ substrate by hot-wall vapor phase epitaxy technique. Tris (N,N-dimethyldithiocarbamato)-gallium (III), Ga(mDTC)₃ was introduced as a precursor material for the seed layer formation in the growth of GaN. Optimal growth conditions with seed layers formed by the Ga(mDTC)₃ concentration of 0.047 mol/L were identified: Growth temperature was found to be 850 °C, and optimal distance between the reactant outlet and substrate was determined to be 12.5 cm. Characterization results showed that this growth method produce high-crystallinity GaN epitaxial layers at a relatively lower growth temperature compared to the existing growth techniques and simplify the growth process.     

Improved strained HEMT characteristics using double-heterojunctionIn0.65Ga0.35As/In0.52Al0.48As design

The DC and microwave properties of strained In_0.65Ga _0.35As/In₀₅₂Al_0.48As HEMTs (high electron-mobility transistors) with double-heterojunction design are presented. The high sheet carrier density and good carrier confinement give rise to excellent device performance with very low output conductance. For 1×150-μm² long-gate HEMTs, the measured cutoff frequency f_T and maximum frequency of oscillation f_max are as high as 37 and 66 GHz, respectively     

Prevalence and role of anticardiolipin antibodies in Crohn disease

OBJECTIVES: Anticardiolipin antibodies belong to the group of antiphospholid antibodies, and may be seen in association with endothelial damage and recurrent vascular thrombosis. The aim of our study was to determine in patients with Crohn's disease the frequency of anticardiolipin antibodies, and to correlate their presence with clinical activity and treatment of the disease. METHODS: One hundred and thirty-eight sera from patients with Crohn's disease and 118 from age-matched controls were tested for IgG anticardiolipin antibodies. In the Crohn's disease group, we determined whether the patients had a past history of vascular thrombosis, a clinically active intestinal disease, or a current immunosuppressive therapy (steroids or azathioprine). RESULTS: Anticardiolipin antibodies were found significantly more often in patients with Crohn's disease than in controls: 11.0% versus 2.5%, P < 0.02. Three patients with Crohn's disease had a past history of vascular thrombosis, but none of them had anticardiolipin antibodies. The presence of anticardiolipin antibodies was not correlated with the fact that patients had a clinically active disease (P = 0.77), or a current immunosuppressive therapy at the time of the serological test (P = 0.95). CONCLUSIONS: There is a significantly high prevalence of patients with anticardiolipin antibodies during Crohn's disease. The positivity of the test does not seem to be correlated to the existence of a past history of vascular thrombosis, nor to the clinical activity of the disease.     

Fractionation studies of palm oil by density gradient

The paper describes a method of fractionating vegetable, animal and fish oils, and in particular palm oil. The method involves addition of a medium comprising two common solvents to the semisolid oils. On centrifugation, the olein and stearin are separated by the medium in the middle. Thirteen media made up from binary combinations of nine solvents, viz. water, propylene glycol, glycerine, methanol, ethanol,n-propanol, isopropanol (IPA), acetone and butanone, are found to be effective in olein-stearin separation. However, only the water/IPA and water/methanol systems have been studied in detail. The aqueous IPA provides a higher yield of olein than water/ methanol but intersolubility between oil and medium is also greater. The fractionation process can be carried out at any suitable temperature. Fractionation of the special prime bleached (SPB) palm oil at 16 C yields an olein with a cloud point of 4.8 C. Some hybrid palm oils produce a large quantity of low cloud point olein which can be bleached readily. The process can be extended to include degumming and neutralization by using an alkaline medium for centrifugation. The olein fractions obtained have been found to be free of phosphatides and the free fatty acids reduced to as low as 0.02%. Metal-scavenging agents have also been added to the medium in an attempt to remove copper and iron. The development of this process into a continuous one has been demonstrated on the AlfaLaval LAPX 202 Separator. Fractionation of crude palm oil using a density gradient provides seven fractions of different characteristics. The iodine values vary from 37.5 to 57.4 and the unsaturated fatty acids range from 32.7% to 51.2%. Triglyceride analysis by carbon numbers shows great differences in the C₄₈ and C₅₂ constituents of the fractions. aThe volume ratio of oil to medium in each case was 1:1. The separation involved the oil and wax.     

Rheology-processing-property relationships in tubular blown film extrusion. I. High-pressure low-density polyethylene

Three different grades of high-pressure low-density polyethylene resin were used to establish relationships between tubular film blowability and the molecular parameters, namely, the molecular weight distribution (MWD) and the degree of long-chain branching (LCB), and also between the processing conditions and the mechanical properties of the tubular blown films produced. For the study, both the shearing and elongational flow properties of the resins were determined. During the tubular film blowing experiment we measured the freeze-line position, the tubular bubble diameter, the takeup speed, the axial tension, the pressure inside the tubular bubble, and the mass flow rate of the resin. The thickness of the tubular blown films was measured from the samples collected. In order to determine the tubular film blowability, we measured the maximum takeup speed at which the tubular blown bubble broke, for various blowup ratios. The measurements described above permitted us to calculate the tensile stresses at the freeze line, in both the machine and transverse directions, and they were found to be correlatable to the processing conditions employed. It has been found that the tubular film blowability is increased as the resin's MWD becomes narrower and the degree of LCB is less. It has been found further that a resin having lower elongational viscosity tends to give a greater draw-down ratio, indicating a better tubular film blowability. Finally, the tensile properties of the tubular blown films were found correlatable to the processing variables, namely, blowup and takeup ratios.     

A Lyapunov functional approach to robust stability analysis of continuous-time uncertain linear systems in polytopic domains

In this paper, a sufficient linear matrix inequality (LMI) condition is presented for robust stability analysis of continuous-time linear time-invariant (LTI) systems in polytopic domains. The underlying idea behind the proposed approach is to introduce a family of complex functions which map the closed right-hand side of the complex plane into the inside of the closed unit circle centered at the origin. Then, the mapping properties are used to assure that all the eigenvalues of a system are located in the open left-hand side of the complex plane. Examples show the validity of the proposed condition.     

Object illumination angle measurement in speckle interferometry

Errors in measurement of the object illumination angle affect fringe interpretation accuracies in speckle interferometry. To measure the object illumination angle we propose a method based on the moiré effect. The technique is easy to implement and was found to yield fast and accurate measurements.