Effect of hydrothermal treatment and ammonium ion incorporation in platinum-mordenite catalysis for n-hexane hydroconversion

Hydroconversion of n-hexane was studied on catalysts containing 0.25% Pt supported on H-mordenite (H-M) and NH₄-M. The H-M containing catalysts were Pt/H-M, Pt on steamed H-M (Pt/St H-M) and steamed Pt/H-M (StPt/H-M), whereas the NH₄-M containing catalysts were Pt/NH₄-M and StPt/NH₄-M. Steam-treatment of H-M containing catalysts enhanced the hydroconversion activity, whereas such treatment decreased the activity of the Pt/NH₄-M catalyst. The diffusion resistance parameter, i.e., the Thiele modulus, Φ_L, estimated for the reaction on the catalysts under study was found to increase with the increase in the catalytic activity, and both were found to decrease in the order:

Pt dispersion in the zeolite was not comparable with the catalytic activities of the H-M containing catalysts. The higher activity of the Pt/NH₄-M catalyst could be attributed to a higher Pt dispersion in the zeolitic channels, higher strength of the acid sites (determined by temperature programmed desorption (TPD) of ammonia) and higher diffusion limitation of the reactant in the catalyst pores.     

Orthotopic replacement with hemi-Kock or W

Since 1986 we have used the orthotopic substitution technique on some 280 male patients suffering from bladder carcinoma and 38 females. There is minimal morbidity and mortality, though patients are generally younger than those seen in Europe and the USA. Postoperative daytime continence is experienced by about 94% of patients and night-time continence by around 78%. Since some complications were encountered using the hemi-Kock's pouch, we devised an orthotopic bladder substitute from 40 cm of ileum, using no staples and without creating a nipple. The ileum is arranged in a W formation, the ante-mesenteric border is incised and the serosa of the two lateral limbs joined together. Two troughs are created on either side of the neo-bladder and each ureter is laid into its respective trough. The mucosa on either side is sutured in front of the ureter creating a tunnel. Some 87 male patients have undergone this revised procedure, and female patients, when the urethra can be utilised.     

Studies on Epdm/Nr Blends. I. Dielectric and Mechanical Properties

Ethylene-propylene-diene terpolymer rubberlnatural rubber blends (EPDM/NR) in different proportions (100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100) reinforced with 20 phr semireinforcing furnace carbon black have been studied. The permittivity ?' and dielectric loss ?″ for these samples were determined in the frequency range 10²–10⁷ Hz. Also, their physico-mechanical properties were investigated.

The EPDM/NR blend (75 : 25) possessed the best mechanical properties and stability against aging. Thus, it was chosen to explore the effect of adding carbon black in different quantities up to 50 phr on its electrical and mechanical properties. Three different types of carbon black. namely high-abrasion furnace black, fast-extrusion furnace black, and medium thermal black, were used. At a certain concentration of carbon black, referred to as the threshold percolation concentration, an abrupt increase in ?′ and ?″, which depends on its type, was detected. This could be attributed to some sort of interaction between the blend and the carbon black at higher concentrations.     

Feasibility study of solar heating and cooling systems at different localities in Egypt

In this investigation, the performance and economic evaluation of a solar heating and cooling system is studied using the transient simulation program (TRNSYS). The water heating load, space heating load, and the cooling load of a typical Egyptian house were considered.     

Evaluation of the DRM and the Time for Preventive Maintenance for Aging Software

An attempt to capture software aging and specify when to do preventive maintenance (PM) is presented in this paper. A composite measure termed the DRM, Deteriorating Response Measure, is defined. It is based on the analysis of the deteriorating speed of the software against time and load. This speed is characterized as follows: (1) It decays with increased load. (2) It does not increase again when the load decreases, this indicates loss of elasticity. The DRM is mathematically formulated based on a queueing system model.Specifying when to do preventive maintenance depends on the decision maker's perspective of the manifestation of aging. It is tried here to formalize this dependence. Three degrading performance metrics are defined for a DRM: (1) Decaying restored speed value. (2) Increasing speed offset ratio (recoverability index). (3) Increasing operation interval offset. These metrics can be used singly or aggregately in a DRM to specify when to do preventive maintenance. Results of model testing are also shown.This work can be part of an on-line procedure that calculates performance indexes for a server type software system like a web browser, an operating system, a database, and helps in the decision to do preventive maintenance for aging software.     

Instrumented Force Platform for Postural Sway Studies

A force platform has been developed, which is capable of measuring postural sway in humans in two orthogonal directions. For each direction, output data consist of total average sway in two frequency bands centered on 0.57 and 2.9 Hz. The device is suitable for use in research or in a clinical setting.     

Polarography of eosin and erythrosin in solutions of varying pH at the DME

The polarographic behaviour of eosin and erythrosin in buffer solutions of pH 4–11 is discussed. The observed waves are assigned to the reduction of furan and pyrone rings of the molecule of erythrosin at pH 4–11 and for eosin at pH ?7. The nature of the waves is also investigated. In alkaline media the electrode reaction is essentially diffusion controlled whereas at pH < 8 adsorption of the reduction products contributes in the electrodes process.     

Stability of spontaneous passive films on high strength Mo-containing stainless steels in aqueous solutions

The stability of naturally grown passive films on some Mo-containing stainless steel specimens was examined in aerated and deaerated universal buffer solutions with different pH (2–12) as well as in sulphate and chloride solutions. Open circuit potential (E _oc) and electrochemical impedance spectroscopy (EIS) were used as measuring techniques. In all cases, E _oc shifts towards less negative values with time until the potential reaches its steady-state (E _ss) value. The E _ss value is found to be more positive with decrease in solution pH or increase in Mo content in the alloy and becomes less positive in deaerated buffer solutions. Also, the thickening rate of the outer layer for the duplex passive film increases with increasing extent of Mo in the steel substrate or pH of the test solution. For a given alloy, E _ss decreases linearly with the anion concentration (C), and is always more positive in Cl⁻ than in SO₄²⁻ media for C ≥ 0.05 M. Analysis of the EIS data showed that the total resistance (R _T) of the passive film has higher values in aerated solutions, and is generally lower in basic solutions. This indicates that lower solution pH favours the formation of oxide films offering better protection. Furthermore, the higher values of R _T in Na₂SO₄ solutions suggest the formation of more stable passive films in sulphate than in chloride solutions. This is discussed on the basis of the relative degree of anion incorporation into the passive films.