Synthesis and Properties of Amide Derivatives of 4-N,N-Dialkylaminoazobenzenes

Several disperse dyes, derivatives of 4-N, N-dialkylaminoazobenzene having acetylamino, carbamyl, phthalimide or naphthalimide substituents have been prepared. Their spectral properties and reaction to heat were determined, and their usefulness was evaluated in terms of the sublimation fastness. It was found that the dyes containing a benzamide system with an unsubstituted NH group, similar to that in phthalimide and naphthalimide derivatives, show a high sublimation fastness due to their ability to associate.     

The porphyromonas gingivalis prtP/kgp homologue exists as two open reading frames in strain 381

Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels increase in patients with heart failure with the progression of clinical symptoms and with the deterioration of hemodynamics; consequently, assay methods for these peptides may be useful in the follow-up of cardiac patients. Non-competitive immunoradiometric assay (IRMA) methods for ANP or BNP do not generally require preliminary extraction and/or purification of the plasma sample, and so may be more suitable than competitive immunoradiometric assay (RIA) methods for the routine assay of plasma peptide concentrations. We evaluated the analytical characteristics and clinical usefulness of two IRMAs for plasma ANP and BNP, to verify whether these methods may be considered suitable for the follow-up of patients with heart failure. Both methods are based on the solid-phase sandwich IRMA system, which uses two monoclonal antibodies prepared against two sterically remote epitopes of peptide molecule; the first antibody was coated on the beads solid-phase and the second was radiolabeled with 125I. Blood samples were collected from a brachial vein in ice-chilled disposable polypropylene tubes containing aprotinin and EDTA after the patient had rested for at least 20 min in the recumbent position. Plasma samples were immediately separated by centrifugation and stored at -20 C until assay. The IRMA methods showed a better sensitivity and a wider working range sensitivity (about 2 ng/l) than those of RIA methods. Moreover, the normal range found with these methods (ANP = 16.1 +/- 8.6 ng/l, 5.2 +/- 2.8 pmol/l, BNP = 8.6 +/- 8.2 ng/l, 2.5 +/- 2.4 pmol/l) was similar to that generally reported using the most accurate methods, such as the other IRMAs or RIAs, using a preliminary extraction and purification of plasma samples with chromatographic procedures. Our results obtained in patients with different degrees of heart failure indicate that plasma ANP and BNP increase with the progression of clinical symptoms (NYHA class) (ANOVA p < 0.0001). Indeed, circulating levels of ANP (R = -0.701, no. = 86) and BNP (R = -0.745, no. = 55) were significantly (p < 0.0001) and negatively correlated with the left ventricular ejection fraction values. Furthermore, a close curvilinear regression (R = 0.960, no. = 215) was found between ANP and BNP values, because plasma BNP progressively increases more than plasma ANP in patients with different stages of heart failure. In conclusion, IRMA methods are preferable for the measurement of plasma ANP and BNP for experimental studies and routine assay because they are more practicable, sensitive and accurate than RIA procedures. Finally, BNP assay appears to be better than ANP for discriminating between normal subjects and patients with different degrees of heart failure.     

Energy–exergy analysis and modernization suggestions for a combined‐cycle power plant

Energy and exergy analysis were carried out for a combined‐cycle power plant by using the data taken from its units in operation to analyse a complex energy system more thoroughly and to identify the potential for improving efficiency of the system. In this context, energy and exergy fluxes at the inlet and the exit of the devices in one of the power plant main units as well as the energy and exergy losses were determined. The results show that combustion chambers, gas turbines and heat recovery steam generators (HRSG) are the main sources of irreversibilities representing more than 85% of the overall exergy losses. Some constructive and thermal suggestions for these devices have been made to improve the efficiency of the system. Copyright © 2005 John Wiley & Sons, Ltd.     

Metadata requirements for digital museum environments

We describe a system which addresses all the processes involved in digitally acquiring, modelling, storing, manipulating and creating virtual exhibitions from 3D museum artefacts. More specifically, we examine the significance of metadata in enabling and supporting all of these processes and describe the extensive facilities provided for authoring, maintaining and managing metadata. The development of the system has been heavily influenced by factors relating to interoperability, standards, museum best practice and feedback from two museum pilot sites. Finally, we briefly consider the system in the wider context of applications such as virtual learning environments and distributed repositories of archives.     

Studies of the fischer-tropsch synthesis on a cobalt catalyst i. evaluation of product distribution parameters from experimental data

Two models describing the distribution of linear and monomethyl alkanes in Fischer-Tropsch products from a cobalt catalyst are formulated. Distribution parameters for monomethyl isomers are derived by assuming either a post-branching effect on linear chain growth or a decreasing reactivity toward branching with increasing chain length. Distribution parameters for each of the models have been extracted from an extensive experimental data set. We find that the experimental results are well represented by both the models. A “break” in the distribution of linear paraffins has also been observed and is modelled as a sum of the yields of two Anderson-Schulz-Flory distributions. We postulate that the two chain growth processes which produce the distributions are governed by two kinds of termination.     

Prospects for a high octane gasoline synthesis catalyst

The thermodynamics of synthesis reactions relevant to the production of alcohols, aldehydes, olefins, paraffins and aromatics lead us to conclude that the direct synthesis of aromatics will be favoured at temperatures around 650 K. We also note that the exothermicity of such a synthesis will be some 20% lower than that in conventional Fischer Tropsch synthesis.     

Kinetics and selectivity of reactions of 1-alkenes on HY zeolite: The influence of chain length

Catalytic reactions of 1-alkenes on HY have been studied at 400°C. Skeletal isomerization to the corresponding rnonornethylalkene is the dominant initial process. Cracking and coke formation are also observed as initial processes. Initial cracking selectivity can be accounted for by monomolecular β-scission processes involving a carbenium ion intermediate. However, the initial cracking product distribution for l-hexene must be explained by assuming some contribution from a dimerization-cracking mechanism. The kinetics of these processes have been fitted by a model previously used to describe the reactions of n-alkanes. It is found that the rate constants for both skeletal isomerization and cracking increase with chain length of the feed alkene.     

The nature of active sites in the isomerization of 1-hexene on cracking catalysts

The molar ratio of cis/trans 2-hexene isomers formed from 1-hexene on NaY zeolites exchanged to various levels with protons or lanthanum ions can be explained by assuming that two types of sites are active for the 1–2 isomerization reaction. The first gives both isomers, while the second gives only the cis isomer. In HY zeolite, active sites for the isomerization reaction can be produced by substitution of the most easily replaced sodium ions, either by simple washing with water, or by calcination of a partially exchanged ammonium form. The catalyst activity and the observed ratio of cis/trans isomers formed on a partially exchanged LaY zeolite, has been found to depend on the degree of hydration of the catalyst. Ratios of cis/trans 2-hexene are closer to their equilibrium value when the reaction is carried out on ZSM-5, mordenite and amorphous silica-aluminas rather than on Y zeolite. This is explained in terms of the proportion of each type of site present, although diffusional limitations within the narrower pore structures of ZSM-5 and mordenite may also play a role.