Supercritical multicomponent solvent coal extraction

The yield of organic extract from the supercritical extraction of coal with larger diameter organic solvents such as toluene is increased by use of a minor amount of from 0.1 to 10% by weight of a second solvent such as methanol having a molecular diameter significantly smaller than the average pore diameter of the coal

Tribological analysis on the effect of heat transfer towards engine in-cylinder friction

The aim of this study is to determine the effect of heat transfer towards engine in-cylinder frictional losses, generated by the piston ring pack sliding along the engine cylinder liner. A mathematical model is derived from the 1D Reynolds equation, using Reynolds’ boundary condition, to determine the contact pressure distribution along the ring-liner conjunction. Meanwhile, the lubricant temperature profile is solved using the 1D energy equation, considering heat conduction and viscous heating effect. The mathematical models are implemented in C-program. The minimum film thickness and the total friction force from the current model are showing good correlation with literature data. The results showed that heat conduction mechanism predominates the viscous heating effect in the ring-liner conjunction. Meanwhile, the boundary friction predominates the contribution of viscous friction, especially along the vicinity of dead centres. However, the boundary friction is not affected by the changes in lubricant viscosity. Hence, from an overall engine operation point of view, the effect of heat transfer towards the total friction force generated by the ring pack could be considered trivial

On graded polynomial identities with an antiautomorphism

AbstractLet G be a commutative monoid with cancellation and let R be a strongly G-graded associative algebra with finite G-grading and with antiautomorphism. Suppose that R satisfies a graded polynomial identity with antiautomorphism. We show that R is a PI algebra

Repetitive Segmental Structure of the Transducin β Subunit: Homology with the CDC4 Gene and Identification of Related mRNAs

Retinal transducin, a guanine nucleotide regulatory protein (referred to as a G protein) that activates a cGMP phosphodiesterase in photoreceptor cells, is comprised of three subunits. We have identified and analyzed cDNA clones of the bovine transducin β subunit that may be highly conserved or identical to that in other G proteins. From the cDNA nucleotide sequence of the entire coding region, the primary structure of a 340-amino acid protein was deduced. The encoded β subunit has a Mr of 37,375 and is comprised of repetitive homologous segments arranged in tandem. Furthermore, significant homology in primary structure and segmental sequence exists between the β subunit and the yeast CDC4 gene product. The Mr 37,375 β subunit polypeptide is encoded by a 2.9-kilobase (kb) mRNA. However, there exists in retina other β-related mRNAs that are divergent from the 2.9-kb mRNA on the basis of oligonucleotide and primer-extended probe hybridizations. All mammalian tissues and clonal cell lines that have been examined contain at least two β-related mRNAs, usually 1.8 and 2.9 kb in length. These results suggest that the mRNAs are the processed products of a small number of closely related genes or of a single highly complex β gene

Antarctic polar stratospheric aerosols: The roles of nitrates, chlorides and sulfates

Nitric and hydrochloric acids have been postulated to condense in the winter polar stratosphere to become an important component of polar stratospheric clouds. One implication is that the removal of NO(y) from the gas phase by this mechanism allows high Cl(x) concentrations to react with O3, because the formation of ClNO3 is inhibited. Contributions of NO3 and Cl to the stratospheric aerosol were determined during the 1987 Airborne Antarctic Ozone Experiment by testing for the presence of nitrates and chlorides in the condensed phase. Aerosol particles were collected on four 500 micron diameter gold wires, each pretreated differently to give results that were specific to certain physical and chemical aerosol properties. One wire was carbon-coated for concentration and size analyses by scanning electron microscopy; X-ray energy dispersive analyses permitted the detection of S and Cl in individual particles. Three more wires were coated with Nitron, barium chloride and silver nitrate, respectively, to detect nitrate, sulfate and chloride in aerosol particles. All three ions, viz., sulfates, nitrates and chlorides were detected in the Antarctic stratospheric aerosol. In terms of number concentrations, the aerosol was dominated by sulfates, followed by chlorides and nitrates. An inverse linear regression can be established between nitrate concentrations and ozone mixing ratio, and between temperature and nitrates

Superconductivity-Induced Anomalies in the Spin Excitation Spectra of Underdoped YBa_2 Cu_3 O_{6+x}

Polarized and unpolarized neutron scattering has been used to determine the effect of superconductivity on the magnetic excitation spectra of YBa_2 Cu_3 O_{6.5} (T_c = 52K) and YBa_2 Cu_3 O_{6.7} (T_c = 67K). Pronounced enhancements of the spectral weight centered around 25 meV and 33 meV, respectively, are observed below T_c in both crystals, compensated predominantly by a loss of spectral weight at higher energies. The data provide important clues to the origin of the 40 meV magnetic resonance peak in YBa_2 Cu_3 O_7.Comment: LaTex, 4 pages, 4 ps figures. to appear in Phys. Rev. Let

Use of comparative research in the study of chemistry education: A systematic analysis of the literature

Comparative research can help identify the similarities of and differences in different contexts, enabling us to recognize more possibilities and strategies of enhancing our understanding of different aspects of education. To review and analyse the current status of using comparative research designs in chemistry education research, a Boolean keyword search in Scopus and Web of Science has been performed to retrieve articles published from January 2016 to February 2023. In total 7682 entries have been retrieved, but less than 0.01 % of them have applied comparative research in addressing issues of chemistry education. Twelve of the retrieved articles have met the inclusion criteria for further analysis. Though comparative research has been found to be used by over 65 % of the analysed articles to study teaching and learning in chemistry education, its application in curriculum development and student development has been demonstrated by some analysed studies. In addition, 75 % of the analysed articles have declared being funded by local and/or national funding sources. This suggests that the importance of comparative research in chemistry education has been recognized at the national level in various countries. It is hoped that the opportunities brought about by comparative research designs as revealed in this article can enhance the varieties and possibilities in chemistry education research in the forthcoming future