Theoretical Study of Strengthening for Increased Shear Bearing Capacity

In recent years, the use of carbon fiber reinforced polymer (CFRP) has been shown to be a competitive method for strengthening both the structural and economic performance of concrete. The method has been used for almost a decade, yet – most research undertaken has studied the flexural behavior of strengthened structures, while research on shear strengthening has been limited. The work presented in this paper focuses on CFRP shear strengthening of concrete beams. The theory presented addresses the limitations of the widely used truss model, and a refinement is suggested. A reduction factor to consider the nonuniform strain distribution over the cross section is proposed and strain limitations are prescribed for the principal strain in the concrete instead of the fiber strain, as in previous studies. The derived analytical model is compared to experimental data from tests. Fairly good agreement is found between results from tests and calculated values from theory with regard to both shear-bearing capacity and average fiber utilization.     

Comparative behaviour of coal and maceral concentrates during artificial coalification

A series of experiments were performed in cold-seal autoclaves (confined-pyrolysis) to characterize the behaviour of individual macerais (vitrinite, inertinite, exinite) extracted from the same Lorraine Basin coal during artificial coalification. Rock-Eval pyrolysis, elemental analysis and weight loss determination provided the simple maturation indexes required. Emphasis was laid on the timing of hydrocarbon generation and on the possible similarities existing between inertinite and vitrinite of higher rank. Hydrocarbon potential and hydrocarbon yield were found to increase from inertinite to vitrinite and exinite, but similar mechanisms were involved during the thermal degradation of both inertinite and vitrinite.     

Toward the Development of Dual‐Targeted Glyceraldehyde‐3‐phosphate Dehydrogenase/Trypanothione Reductase Inhibitors against Trypanosoma brucei and Trypanosoma cruzi

A significant improvement in the treatment of trypanosomiases has been achieved with the recent development of nifurtimox–eflornithine combination therapy (NECT). As an alternative to drug combinations and as a means to overcome most of the antitrypanosomatid drug discovery challenges, a multitarget drug design strategy has been envisaged. To begin testing this hypothesis, we designed and developed a series of quinone–coumarin hybrids against glyceraldehyde‐3‐phosphate dehydrogenase/trypanothione reductase (GAPDH/TR). These enzymes belong to metabolic pathways that are vital to Trypanosoma brucei and Trypanosoma cruzi, and have thus been considered promising drug targets. The synthesized molecules were characterized for their dual‐target antitrypanosomal profile, both in enzyme assays and in in vitro parasite cultures. The merged derivative 2‐{[3‐(3‐dimethylaminopropoxy)‐2‐oxo‐2H‐chromen‐7‐yl]oxy}anthracene‐1,4‐dione ( 10 ) showed an IC₅₀ value of 5.4 μM against TbGAPDH and a concomitant K_i value of 2.32 μM against TcTR. Notably, 2‐{4‐[6‐(2‐dimethylaminoethoxy)‐2‐oxo‐2H‐chromen‐3‐yl]phenoxy}anthracene‐1,4‐dione (compound 6 ) displayed a remarkable EC₅₀ value for T. brucei parasites (0.026 μM ) combined with a very low cytotoxicity toward mammalian L6 cells (7.95 μM ). This promising low toxicity of compound 6 might be at least partially due to the fact that it does not interfere with human glutathione reductase.     

Cloning and characterization of the NAD-linked glycerol-3-phosphate dehydrogenases of Trypanosoma brucei brucei and Leishmania mexicana mexicana and expression of the trypanosome enzyme in Escherichia coli

A polyclonal antiserum raised against the purified glycosomal glycerol-3-phosphate dehydrogenase of Trypanosoma brucei brucei has been used to identify the corresponding cDNA clone in a T.b. brucei expression library. This cDNA was subsequently used to obtain genomic clones containing glycerol-3-phosphate dehydrogenase genes. Two tandemly arranged genes were detected in these clones. Characterization of one of the genes showed that it codes for a polypeptide of 353 amino acids, with a molecular mass of 37,651 Da and a calculated net charge of +8. Using the T.b. brucei gene as a probe, a corresponding glycerol-3-phosphate dehydrogenase gene was also identified in a genomic library of Leishmania mexicana mexicana. The L.m. mexicana gene codes for a polypeptide of 365 amino acids, with a molecular mass of 39,140 Da and a calculated net charge of +8. The amino-acid sequences of both polypeptides are 63% identical and carry a type-1 peroxisomal targeting signal (PTS1) SKM and -SKL at their respective C-termini. Moreover, the L.m. mexicana polypeptide also carries a short N-terminal extension reminiscent of a mitochondrial transit sequence. Subcellular localisation analysis showed that in L.m. mexicana the glycerol-3-phosphate dehydrogenase activity co-fractionated both with mitochondria and with glycosomes. This is not the case in T. brucei, where the enzyme is predominantly glycosomal. The two trypanosomatid sequences resemble their prokaryotic homologues (32-36%) more than their eukaryotic counterparts (25-31%) and carry typical prokaryotic signatures. The possible reason for this prokaryotic nature of a trypanosomatid glycerol-3-phosphate dehydrogenase is discussed.     

Calculation of the compressibility factor of natural gases based on the calorific value and the specific gravity

The measurement of large volume flows of natural gas in transmission lines requires an accurate equation of state for pressures up to about 12 MPa and in the temperature range from 265 to 335 K. If a detailed analysis of the gas mixture is available, one of the possibilities is to use the virial equation of state. However, such a gas analysis is time-consuming and expensive and, therefore, not always practical. We have developed a new equation which is based on the virial equation but requires limited input data. In general, for any given natural gas, the gross calorific value, the specific gravity, and the mole fractions of nitrogen and carbon dioxide are known. It will be shown that a knowledge of three of these four quantities is sufficient for an accurate prediction of the compressibility factor of the natural gas.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

New types of cellulose materials obtained by an alternative spinning method

Conclusions ALCERU, Lyocell, Newcell, and Tencel (the order is alphabetical and not by importance) are thus alternative hydrated cellulose fibres fabricated by a method with a low degree of harmfulness. Is this only a name or is it also a hope, as for viscose wool fibre 60 years ago? In our opinion, this is much more than only the beginning of a new generation of fibres, yarns, thin strips from film, spun articles, etc. Is this perhaps an overestimation again? No, we are convinced that this is the true path to future developments.In research on this type of processing, the goal should not be to replace natural silk, cotton, or chemical fibres, but to create a totally different type of biodegradable material fabricated with a low degree of harmfulness of the process. A multitude of requirements of modern economic development related to the operation and cost-effectiveness of production could be satisfied in this way.During development, we became convinced that fibrillation is not a defect, but instead a positive effect whose use will make it possible to discover new types of materials. And we should now be bold in using these new fibres and yarns for creating new materials. The reports from Courtaulds (Great Britain) concerning the introduction of three installations with a capacity of 50,000 tons a year each and Lenzing (Austria) concerning an installation with a capacity of 40,000 tons a year in the next three years are convincing evidence of the validity of this opinion.C. Burger's report to the annual meeting of the Scientific Council on Scientfic Research on Textile Problems, Dresden, 1994.Turing Textiles and Plastics Research Institute, Rudolstadt. Translated from Khimicheskie Volokna, No. 1, pp. 35–39, January–February, 1966.     

The conductance of suspensions with conducting particles

The conductance of conductive ceramics, graphite and metal suspensions in aqueous KOH solutions was measured with the impedance technique using a four-electrode cell. The measurements were carried out for volume fractions up to high viscosities with particles of different sizes. A wide frequency range was used to investigate also the effect of particle-surface polarisation on the conductance. The results have been analysed in terms of the asymmetric and symmetric theories of Bruggeman and the GEM theory for a wide volume-fraction range of suspended particles. Depending on the suspended material, particle size and electrolyte properties, the suspensions reveal flocculation or chain formation. In case of chain formation, sometimes a decrease of the polarisation resistivity is found due to shortcircuiting by direct particle-particle contact. The conductivities of the particles phase, calculated from measured values, are orders lower than predicted from conductivity data of the pure materials. This is attributed to the occurrence of a constriction resistance and film resistance between the particles in the case of flocculation or chain formation as well as to poor wetting of the particles.