Diels-Alder Reactions with Some N-Substituted Maleimides

A series of endo-carbonyl-1,2-dihydro-(3,4,5,6-tetraphenyl)-N-substituted phthalimides ( 5a – e ) has been synthesized by the Diels-Alder reaction of tetracyclone ( 2 ) with some N-substituted maleimides ( 1a – e ). Decarbonylation of the adducts 5a , b afforded the dihydrophthalimides 6a , b . The dihydro adducts 7a , b and 8a , b were obtained when phencyclone ( 3 ) and 2,3-dimethylfurane ( 4 ) were allowed to react with maleimides 1a , b . Dehydrogenation of the dihydro adducts 5a , b , 6a , b , 7a , b , 8a , b yielded the adducts 9a , b , 10a , b , 11a , b , 12a , b , respectively. The dihydro adducts 6a , b , in contrast to the dihydro adducts 7a , b , reacted further with one molecule of a dienophile to provide the dihydro adducts 14a , b , 15a , b and 16a , b . The dihydro adducts 16a , b , were also obtained in one step when one molecule of 2 was allowed to react with two molecules of each of the N-substituted maleimides 1a , b .     

A novel scheme to improve fault-tolerant capabilities of multistage interconnection networks

In this paper, we propose a novel augmenting and partitioning scheme for constructing multistage interconnection networks (MINs) with improved fault-tolerant capabilities. We first propose a partitioning scheme to construct and analyze partitioned MINs (PMINs). A simulation method is developed, based on the stuck-at fault model, to evaluate dynamic full access (DFA) and average number of passes in PMINs. We then propose an augmenting scheme to construct augmented partitioned MINs (APMINs) with further enhanced fault-tolerant capabilities. Simulation analysis of APMINs, based on the switch level fault model, showed that the proposed scheme significantly improves the fault-tolerant capability of MINs. Finally, the effectiveness of the proposed scheme is evaluated with respect to cost, DFA, locality, and average path length. This revised version was published online in June 2006 with corrections to the Cover Date.     

Impact of network failures on the performance degradation of aclass of cluster-based multiprocessors

The impact of increased unreliability of network components on the performance of a cluster-based multiprocessor system (CBMS) is investigated. A generalized model which has been developed for computing the closed-form bandwidth expressions for fault-free as well as faulty systems is discussed. Performance curves are given which illustrate the degradation when unreliability is increased in terms of the number of cluster-network failures. The architecture of the CBMS along with background material for the analysis is described. A special case called private and favorite memory is discussed     

Analysis of file usage in personal computer environments

This paper discusses collection, analysis and interpretation of data pertaining to files in personal computer (PC) environments. We developed programs to collect and analyze data from PCs running the OS/2¹ operating system and using the High Performance File System (HPFS). The data collection program gathers the information about file sizes, the times and dates of file creation, the last file access, and the last file update by scanning the contents of disk storage devices. The gathered information is used to analyze the distributions of file sizes, functional file lifetimes, and functional lifetimes of file's data. The analysis shows that: most files are small (more than 60% of files on a system are smaller than 8 Kbytes), about 60% of files on a system have never been accessed again after being created and very few files are ever modified. Recommended by: N. Boudriga     

Synergism between phospholipids and naturallyoccurring antioxidants in leaf lipids

Based on oxygen absorption induction periods, the phospholipids, phosphatidylcholine and phosphatidylethanolamine, have been shown to exert a deleterious effect on the stability of lard. However, when these phospholipids are used in combination with the naturally-occurring antioxidants, α-tocopherol and/or quercetin, a very substantial improvement in oxidative stability can be observed. This form of synergistic interaction has been shown to account for the remarkable stability exhibited by leaf lipids.     

Experimental relative permeability curves compared with a new cutting and joining model of porous media with a distribution of pore sizes

A new cutting and joining model of the pore space is presented for calculating wetting and non-wetting phase relative permeability curves in two-phase flow in porous media. Experimental relative permeability curves have been measured in packings of glass beads, both monosized and with a range of sizes. The results are compared with the predictions of the model and with those of other models from the literature.     

Ripening Profile of Semi-Hard Standard Goat Cheese Made From Pasteurized Milk

The microbial groups, physico-chemical characteristics, proteolysis, lipolysis, and rheological properties over a 30-day ripening period of a semi-hard cheese from pasteurized goat's milk were investigated. The count of aerobic mesophilic flora was high in cheese throughout ripening with lactic acid bacteria being the main microbial group. Halophilic bacteria, yeast and molds showed initial low counts but maintained their levels relatively constant during the ripening period. The main biochemical modification of cheese during ripening was related to the extent of proteolysis. The water soluble nitrogen in the semi-hard cheese increased during ripening. Lipolysis also occurred throughout the ripening period, with the major constituents being the palmitic, oleic, myristic, capric, and lauric acids. The rheological study suggested that the most important factors influencing the texture of the goat cheese is the level of total solids, and the extent of protein degradation recorded as soluble nitrogen during the ripening period. Rheological properties of goat cheese showed a transformation from a soft and elastic consistency to a hard and brittle body as a function of aging.     

Effect of temperature on the inhibition of the acid corrosion of steel by benzimidazole derivatives

The effect of 2-mercaptobenzimidazole (inh. I) and 2-mercapto-5-methylbenzimidazole (inh. II) on the corrosion of mild steel in 1M solutions of sulphuric acid has been investigated in relation to the concentration of the inhibitor as well as temperature by various monitoring corrosion techniques. The results obtained revealed that these compounds are good inhibitors. All the impedance diagrams gave semicircles for both inhibitors indicating that the corrosion of mild steel is controlled by a charge transfer process and the presence of either inhibitor does not alter the mechanism of the dissolution of mild steel. In general, both inhibitors efficiencies increased with increasing the inhibitors concentration at all temperatures used. On the other hand, inhibitors efficiencies were almost constant with increasing the temperature at concentrations 5 × 10⁻⁴ M, 1 × 10⁻³ M and 5 × 10⁻³ M. The best performance was noticed in case of (inh. II) especially at the concentration 5 × 10⁻³ M. Adsorption of both inhibitors was found to follow Langmuir, Flory-Huggins isotherms and kinetic-thermodynamic model. The binding constants “K” were calculated for both inhibitors. On increasing the temperature, the value of “K” increased in both cases indicative of stronger binding of the inhibitor molecule to the mild steel surface and hence higher inhibition efficiency at higher temperatures. The activation energy of the corrosion reaction decreases with increasing the concentration of (inh. I) or (inh. II). The adsorption of both inhibitors on the surface of mild steel is probably chemisorbed on the electrode surface. The thermodynamic parameters were calculated. Mass loss measurements revealed that both inhibitors exhibit maximum inhibition efficiency with increasing the concentration and temperature which confirm the data obtained from AC impedance. DC polarization data reveals that, both inhibitors does not alter the mechanism of anodic behaviour of mild steel and they behave as mixed type inhibitors. Again both inhibitors exhibit maximum inhibition efficiency with increasing the concentration and temperature which confirm the data obtained from AC impedance.     

Fatty acid composition of muscle and fat tissues of Omani Jebel Akhdar goats of different sexes and weights

This paper describes the fatty acid (FA) composition of muscle and fat tissue in Omani Jebel Akhdar buck, wether and does slaughtered at 11, 18 or 28 kg body weight (BW). The fat percentage in dry matter (DM) of the subcutaneous and kidney fats ranged between 85 and 98% and that of muscle ranged between 17 and 21%. Subcutaneous fat tended to have lower DM than kidney fat. Palmitic (C16:0), stearic (C18:0) and oleic (C18:1) acids comprised the largest proportions of FA in the muscle tissue (approximately 80%) with oleic acid being the most abundant. Ninety-one percent of the total FA were contributed by the C16 and C18 fatty acids being 31.6 and 58.5%, respectively. C19 and C20 were not detected in the muscle tissue. The essential FA, C20:2, C20:3 and C20:4 contributing about 1%. Muscle tissue of the Jebel Akhdar goat contained an average 51.3% and 48.7% of saturated (SFA) and unsaturated fatty acids (UFA), respectively. Polyunsaturated FA (PUFA) constituted about 5% and monounsaturated (MFA) 43.5% of the total FA. Subcutaneous fat contained more total FA (68.08%) than kidney fat (48.14%) in the whole tissue. Kidney fat contained higher percentages of C16 and C18 but less C:18:1 than subcutaneous fat. The proportions of SFA to UFA was high in both fat depots with the SFA being much higher in the kidney than subcutaneous fats. C16, C18 and C:18:1c acids comprised 64.2 and 78% and C16s and C18s made up 81 and 85% of total FA in subcutaneous and kidney fats, respectively. In both subcutaneous and kidney fats, there was a trend of increasing values of DM and fat percentage with intact males having the lowest and females the highest values. Males had higher levels of C15, C18:2 and C18:3 but lower levels of C17, C18 and total C16, C18 and C18:1 in muscle tissue. Intact males had higher levels of C10, 12, 15 FA but lower C16:1 and C16+18+18:1 than others in subcutaneous fat. Intact males had a similar trend for C12 and 14 but lower SFA and higher UFA in kidney fat. There was a trend of increasing DM and fat% in dry matter with increasing body weight. C10, 12 and 14 of the kidney fat decreased with increasing slaughter weight. There was a trend of the two C16 FA decreasing and the four C18 increasing with BW in the kidney fat. This resulted in proportions of the total C16 and C18 FA increasing from 81.8 to 86.8%. These findings confirm those of other studies on goat meat quality that, as judged by fatty acid composition it is not inferior to that of meats from other farm animals.