Showing papers by "Xiamen University published in 1993"

Role of phosphate in fe2+ binding to horse spleen holoferritin

Abstract: In order to identify the function and location of phosphate associated with the iron core of horse spleen ferritin (HoSF), the phosphate content of native HoSF was altered by two procedures. Adjustment of pH from 7.0 to 10.0 irreversibly released 53% of the phosphate and 10% of the iron, while lowering the pH to 5.0 reversibly released 43% of the phosphate and 35% of the iron. Reversible release of 85% of the initial phosphate (but little iron release) also occurs upon reduction with methyl viologen (MV) or dithionite. Most of the phosphate is released in the early stages of reduction of the iron core, suggesting that the phosphate resides primarily on the mineral core surface. Reduction followed by chelation altered both the iron and phosphate content of the HoSF mineral cores. HoSF iron cores first reconstituted in the absence of phosphate and then incubated with added phosphate did not bind phosphate. However, when HoSF was first reconstituted in the absence of phosphate and then equilibrated anaerobically with both Fe2+ and phosphate, then phosphate was incorporated in amounts similar to native HoSF. Fe2+ binding to native, phosphate altered, and reconstituted HoSF in the presence and absence of phosphate clearly showed that Fe2+ binding to the mineral core depends on the presence of core-bound phosphate. Fe2+ binding to phosphate-depleted mineral cores or to cores reconstituted with 621, 2158, and 3013 Fe/HoSF core in the absence of phosphate bound only eight Fe2+ per entire ferritin molecule, clearly showing that Fe2+ has no measurable affinity for the phosphate-free, reconstituted mineral core.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproductive biology of the guitarfish, Rhinobatos hynnicephalus

Abstract: Reproductive biology of the guitarfish, Rhinobatos hynnicephalus from Xiamen coastal waters is described. Males have two functional testes. Spermatogenic cells in different seminiferous follicles are at different developmental stages while those in the same follicle are at the same stage. The development of claspers suggests that males mature at 380–400mm TL. Females mature at 390–440mm TL. Both ovaries are functional. The first generation of ovarian eggs reach mature size when 22–24mm in diameter in April or May. The subsequent crop of eggs is ready for ovulation when the intrauterine embryos reach full term. The guitarfish is aplacentally viviparous. Longitudinal folds were observed on the internal wall of the uterus. Gestation takes one year and parturition takes place in June or July. Fecundity ranges from 2 to 9, with the large females usually being more fecund. Of 29 embryos ranging from 52–157 mm TL, there were 15 females and 14 males indicating an embryonic sex ratio 1:1.

On the resonance theory

Abstract: In the present paper, the mathematical formulation of resonance theory is discussed. In fact, resonance theory is a representative form of the unitary group approach. Using the standard projection operator of the symmetric group, a new basis for an irreducible representation of the unitary group, called bonded tableau, can be constructed to describe a resonance structure correspondingly. The relationships between bonded tableau and Weyl tableaux and between valence bond and molecular orbital approaches are revealed. Finally, test calculations on ozone and benzene are performed.

Photocatalytic reduction of pollutant Hg(II) on doped WO3 dispersion

Abstract: The photocatalytic reduction of pollutant Hg(II) on photocatalyst ZnO—WO3 or NiPc—WO3 under visible light irradiation is investigated. The adsorbance of Hg(II) on the photocatalyst surface is determined. The Hg(II) (100 μg ml−1) contained in an aqueous solution can either be almost totally eliminated by using ZnO—WO3 as catalyst or be 71.7% photoreduced using NiPc—WO3 as catalyst on irradiation for 1 h. The gram molecular ratio 0.5ZnO—WO3 and 5wt.%NiPc—WO3 are chosen to be the optimal doping ratios. The photocatalytic activities remain constant at pH values in the range 3–4.5 and markedly decrease at pH<3 in accordance with thermodynamic criteria. Photocatalytic Hg(II) reduction is proved to be a first-order reaction. The solar photocatalytic reduction rate of pollutant Hg(II) is markedly improved. 99.1% of the Hg(II) can be photoreduced from a solution of 100 μg ml−1 concentration under sunlight irradiation for 110 min; from this, better prospects for the application of solar photocatalysis to environmental protection is developed. The photocatalyst is characterized by the surface photovoltaic effect, UV—visible absorption spectrum, X-ray diffraction and laser plasma time of the flight mass spectrum. All the experimental results are explained theoretically. A reaction mechanism has been proposed in detail.

Methane oxidative coupling over fluoro-oxide catalysts

Abstract: LaF3 modified ZrO2, CeO2 and ThO2 catalysts for the oxidative coupling of methane indicate that ZrO2/LaF3, CeO2/LaF3 and ThO2/LaF3 catalysts have high activity and high selectivity at low temperature. In the temperature region 480–650 °C, the methane conversion is 24.38–30.8% and the C2= selectivity is 40–55.38%. The characterization of oxygen species on the catalysts indicates that, because of the modification of LaF3 to ZrO2, CeO2 and ThO2, it is favourable for the activation of O2.

Reproductive biology of guitar,Rhinobatos hynnicephalus

Abstract: Reproductive biology of the guitarfish,Rhinobatos hynnicephalus, from Xiamen coastal waters is described. Males have two functional testes. Spermatogenic cells in different seminiferous follicles are at different developmental stages while those in the same follicle are at the same stage. The development of claspers suggests that males mature at 380–400 mm TL. Females mature at 390–440mm TL. Both ovaries are functional. The first generation of ovarian eggs reach mature size when 22–24mm in diameter in April or May. The subsequent crop of eggs is ready for ovulation when the intrauterine embryos reach full term. The guitarfish is aplacentally viviparous. Longitudinal folds were observed on the internal wall of the uterus. Gestation takes one year and parturition takes place in June or July. Fecundity ranges from 2 to 9, with the large females usually being more fecund. Of 29 embryos ranging from 52–157mm TL, there were 15 females and 14 males indicating an embryonic sex ratio 1:1.

Valence bond description for the ground state and several low-lying excited states of LiH

Abstract: Of these three bonded tableaux, the first two consist of the covalent bond between the atomic orbital Hls and the hybrid atomic orbitals of Li 2s and Li 2p,, while the last one corresponds to the ionic structure Li+H-. Further analyses showed that, compared with the covalent structures, the ionic structure Li+H- contributes less to the binding energy and the dipole moment of the ground state of LiH. This result differs from that based on MO theory. Our results clearly indicate that an electron will transfer from lithium to hydrogen in the range 5.0-7.0 a.u., which explains the so-called “harpoon” mechanism in the molecular-beam dynamics. A detailed and successful valence bond explanation for the variation curve of the dipole moment ~1 with respect to the distance R for the first excited state is also presented. There are two opposite effects, namely the contribution from the ionic structure Li+H- and the non-equivalent sp hybridization of the atomic orbitals on lithium, which make the dipole moment of the first excited state vary with R and lead the direction of ~1 to reverse at approximately 6.0a.u. A brief discussion of the other three excited states is given.

Optical multiple‐variable fuzzy logic array using shadow casting

Abstract: An optical area-coded scheme is proposed to implement three-variable fuzzy logic based on the shadow-casting technique on one stage. In particular, no thresholding device is required. Experimental results are also given. © 1993 John Wiley & sons, Inc.

Oxidative coupling of methane over BaF2-TiO2 catalysts

Abstract: The addition of F− to Ba-Ti mixed oxide catalysts significantly improves the catalytic performances for the oxidative coupling of methane (MOC), which can achieve high C2 yields at wide feed composition range and high GHSV. The effect is particularly marked for the BaF2− TiO2 catalysts containing more than 50 mol% BaF2. The C2 yield of 17% and the C2 selectivity of > 60% were achieved over these catalysts at 700 ° C. After being on stream for 31 h, the ≥ 50 mol% BaF2-TiO2 catalysts showed only a 1–1.5% decrease in the C2 yields. Results obtained by XRD show that various Ba-Ti oxyfluoride phases were formed due to the substitution of F− to O2−.

Acidity generation on mechanically mixed ZrO2-ZnO catalysts

Abstract: Lewis acid sites are generated by mechanical mixing of ZrO2 and ZnO. These sites may be the coordinatively unsaturated metal ions, on which adsorbed pyridine cannot be desorbed during the multiple scans on a laser Raman spectroscope; but physisorbed pyridine and its adspecies on Bronsted acid sites desorb easily under laser irradiation.

Study of localized molecular orbitals using group theory methods and its approach to the many-electron correlation problem: III. Orthogonal bonded functions

Abstract: By using the group symmetrical localized molecular orbitals (SLMOs) as configuration-generating orbitals (CGOs) of many-electron wave functions, the symmetry adaptation of many-electron spaces is greatly simplified, and novel orthogonal bonded functions (OBFs), as complete space- and spin-adapted antisymmetrized products, are introduced. The corresponding programs for the solutions of OBFs are developed. © 1993 John Wiley & Sons, Inc.

Improved model of optical fuzzy associative memory.

Abstract: A new learning algorithm of fuzzy associative memory is proposed. Optical implementation of a fuzzy associative memory network is presented, and experimental results are given.

Interstitial photodynamic therapy for cancers of cavum oris, skin, and cervix

Abstract: Interstitial photodynamic therapy, in which the straight cut optical fiber was directly inserted into tumors and the insertion points were rationally arranged on an entire lesion area, was performed on 31 oral cancers, 6 skin cancers, and 4 cervix cancers in 41 patients. A highly satisfactory rate of complete response (90%) was obtained via only one treatment. And no severe complication occurred in any of the treatments. The follow-up record for 33 cases with a CR curative effect shows 12 cases have survived free of tumor more than 4 years and only 5 cases relapsed within a year. In this paper, the factors affecting therapeutic effectiveness and the selection of indication are discussed.

Effects of Formic Acid and CO2 in CO Hydrogenation to Methanol Over Copper-Based Catalysts and Nature of Active Sites

Abstract: Effects of small amounts of formic acid and/or CO 2 on methanol yield in CO hydrogenation to methanol over Cu/ZnO, Cu/ZrO 2 , and Cu/MgO catalysts and the in-situ FT-IR spectra of the chemisorbed species have been investigated. Formate adspecies appears to be a chemisorbed intermediate in CO hydrogenation to methanol over the three copper-based catalysts; CO hydrogenation over Cu/MgO is inhibited by even very small proportion of CO 2 ; over Cu/ZnO, the inhibit on by CO 2 becomes apparent at slightly higher CO 2 proportion, while over Cu/ZrO 2 it is unaffected by small amounts of CO 2 . The inhibition is probably due to carbonation of the basic MgO site and the slightly basic ZnO site. The nature of the active site and mechanism of synergistic catalysis in CO hydrogenation to methanol over copper-based catalysts is discussed.

Characterization of mosx-k+/sio2 catalysts for synthesis of mixed alcohols from syngas

Abstract: Characteristic studies, by means of XRD, XPS, LRS, IR and TPD methods, of MoS x -K 4 /SiO 2 catalysts for mixed alcohols synthesis provide experimental evidence for formation of Mo-S-K surface phase and presence of disulfide species, (S-S) 2− , at the surface of the catalysts. One of the origins of the promoter action in shifting the selectivity from hydrocarbons to alcohols is likely that addition of the alkali salt led to a decrease in concentration of (S-S) 2− at the surface, which in turn would reduce the generation of the reactive hydrogen.

Tea, Silver, Opium and War: From Commercial Expansion to Military Invasion

Abstract: Sino-Western relations in the eighteenth century mainly found their expression in a particular mode of commercial transactions in Canton. The structure of the Western trade with China was based on silver and colonial products from India and the Malay archipelago, like silver, cotton, pepper, lead. These commodities were exchanged for Chinese tea, silk and porcelain by the mediation of the so-called Hong trades. As long as the trade structure was kept in balance the Westerners were able to make large profits and commercial relations remained the same. When the trade structure fell out balance through, for instance, a shortage of silver or the prohibition of opium smuggling, the Western powers resorted to force. The discontinuation of the traditional Sino-Western trade because of an imbalance in the trade structure eventually did not lead to the decline of trade, but to military conquest: the Opium War in 1840. This War enabled the Westerners, headed by the English, to revamp the structure of their trade with China on their own terms and forced the Chinese government into acceptance. Since then the process of the Western expansion into China was characterised by commercial expansion, military show of force and political control. In this essay I would like to analyze how the traditional structure of Sino-Western trade lost its equilibrium and to study the changing character of European expansion into China as a result of this imbalance during the period of 1740-1840.