Showing papers by "Chinese Academy of Sciences published in 1983"

Methylotrophic bacteria: biochemical diversity and genetics.

Abstract: Bacteria that are able to use methane as a sole carbon and energy source also carry out a broad range of biotransformations, some of which have industrial and environmental significance. Genetic studies on methylotrophs, including the use of recombinant DNA techniques, show promise for the isolation and cloning of genes coding for specific functions.

Inequality of eddy transfer coefficients for vertical transport of sensible and latent heats during advective inversions

Abstract: Similarity of transport of water vapour and sensible heat was investigated within an advective inversion layer by measuring eddy fluxes together with gradients of temperature and humidity. The experimental site was a field of rice, grown under flood irrigation, which was situated in a semi-arid region. The fetch was about 300 m and local stabilities (z/L) over the rice ranged from 0 to 0.1. Results were expressed as the ratio of eddy transfer coefficients for sensible heat (K H) and water vapour (K w). Near neutral stability, K H/KW approached 1, but the ratio decreased to about 0.65 with increasing stability. Existing theory predicts the result qualitatively but accounts for only about one fifth of the decrease in K H/KW with stability.

Pseudolaric acids from Pseudolarix kaempferi.

Abstract: Three novel diterpenoids, pseudolaric acids A, B and C, were isolated from the root bark of PSEUDOLARIX KAEMPFERI G ORDEN used as an antifungal agent in folk medicine in China. The structures of pseudolaric acids B and C were assigned as 1 and 6 by spectral and chemical evidence. Pseudolaric acids A, B and C possess antifungal activity and pseudolaric acid B possesses an antifertility effect.

On the vertical structure of tidal currents in a homogeneous sea

Abstract: Summary. The vertical variation of tidal currents caused by friction at the sea-bed is investigated in both qualitative and quantitative ways with the Coriolis force being taken into account. The simple model with the assumption of constant eddy viscosity is employed to study the effects of friction on the vertical structure of tidal currents. The model explains these effects in vertical change of the maximum velocity, the ellipticity (the ratio of the minor to the major axis) of current ellipse, the time and the direction of the maximum velocity, and the ratio of diurnal current to semidiurnal current. To reach a quantitative agreement with the data observed by Bowden & Fairbairn in the Irish Sea, the mixing length theory is applied to numerical calculation of the vertical distribution of tidal currents with a finite difference scheme. A fair agreement with the observations is obtained in the calculation. The results show the following features: (1) the vertical profile of amplitude of the main component for the current is almost logarithmic throughout the depth; (2) the corresponding profde for the shearing stress is almost linear with depth; (3) the maximum stress lags the maximum velocity with the delay increasing with elevation; (4) the eddy viscosity coefficient has its maximum around the mid-depth; and (5) the vertically averaged viscosity lags the velocity magnitude. The dependence of the quadratic resistance coefficient and the coefficient k defined by Bowden's formula v= khū(h — depth, v and ū— depth-averaged eddy viscosity and velocity) on the roughness length is given for a steady flow in a non-rotating system. The numerical solution shows that these relations can be approximately applied to the tidal currents in shallow waters.

The asymptotic near-tip solution for mode-III crack in steady growth in power hardening media

Abstract: Two local solutions, one perpendicular and one parallel to the direction of solar gravitational field, are discussed. The influence of gravity on the gas-dynamical process driven by the piston is discussed in terms of characteristic theory, and the flow field is given quantitatively. For a typical piston trajectory similar to the one for an eruptive prominence, the velocity of the shock front which locates ahead the transient front is nearly constant or slightly accelerated, and the width of the compressed flow region may be kept nearly constant or increased linearly, depending on the velocity distribution of the piston. Based on these results, the major features of the transient may be explained. Some of the fine structure of the transient is also shown, which may be compared in detail with observations.

Effect of cations, anions and salt concentrations on oviposition by trichogramma pretiosum in wax eggs

Abstract: K+, Mg2+, Cl−, and SO42- were important components eliciting oviposition by Trichogramma pretiosum in aqueous solutions in wax eggs. Ca2+ inhibited oviposition in a KCl-MgSO4 solution. The solutions most active in stimulating oviposition were 124.7–36.5 and 83.1–24.3 mM, respectively, of KCl-MgSO4. RESUME Effet des concentrations en cations, anions et sels sur la ponte de Trichogramma pretiosum sur des œufs en paraffine La ponte de Trichogramma pretiosum Riley dans des œufs artificiels etait induite par une combinaison de K+, Mg2+, Cl− et SO42-. Par contre Na+, Mn2+, Fe3+, Zn2+ et Cn2+ avaient peu ou aucun effet sur la ponte. Ca2+ inhibait la ponte quand il etait ajoute a une solution de KCl-MgSO4. Quand des solutions salines etaient testees seules, KCl etait legerement actif, NaCl faiblement actif et MgSO4 tres faiblement actif. La concentration la plus efficace etait 124,7 mM KCl-36,5 mM MgSO4; cette solution permettait d'obtenier 5000 œufs de Trichogramma par œuf artificiel. Quand les concentrations en K+ et Mg2+ etaient maintenues constantes a respectivement 84,1 et 48,6 meq/l. et que les concentrations de Cl− et SO42- variaient, l'ordre d'activite de ponte etait: 83,1 meq/l Cl− −48,6 meq/l SO42- > 48,6 meq/l Cl− 83,1 meq/l SO42- > 131,7 meq/l Cl −131.7 meq/l SO42-.

Interpenetrating polymer networks from polyurethanes and methacrylate polymers. I. Effect of molecular weight of polyols and NCO/OH ratio of urethane prepolymers on properties and morphology of IPNs

Abstract: Two types of reinforced elastomeric interpentrating polymer network (IPN) were prepared by simultaneous polymerization and crosslinking in solution. The first type consisted of polyurethane-poly(methyl methacrylate) (PU/PMMA), and the second, of polyurethane-poly(methyl methacrylate-methacrylic acid) PU/P(MMA–MAA) of constant composition (90/10) and (80/20) by weight, respectively. The members of each type differed in the NCO/OH ratio of the PU prepolymer and the molecular weight (MW) of the polyol in the PU component because we wished to investigate systematically the effect of changing the NCO/OH ratio and MW of the polyol on the mechanical properties and morphology of the resulting IPNs. The mechanical properties, particularly the modulus of both tyes of IPN, increased with increasing NCO/OH ratio and decreased with increasing MW of the polyol in the PU. The morphology of the IPNs was studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Improved phase compatibility and decreasing extent of phase separation was observed in both types of IPN with increasing NCO/OH ratio and decreasing MW of the polyol used in the PU. These results may imply that improved interpenetration results from increasing the NCO/OH ratio and decreasing the MW of the polyol in the PU component. The fact that the effect is more pronounced with the type of PU-P(MMA–MAA) IPN can be rationalized as due to the additional hydrogen bonding between the carbonyl in the carboxyl groups and the urethane or urea groups in the PU component.

Indications of Optical Coherence in Biological Systems and Its Possible Significance

Abstract: The widespread, if not general phenomenon of “ultraweak” photon emission from living cells and organisms, which is different from bioluminescence1), has been extensively 2–4) reviewed The measurements are carried out with a photomultiplier of high sensitivity in the range between 200 and 800 nm. The living material is kept within cuvettes in a dark chamber in front of the photomultiplier (for a more detailed description see refs.3–5)). With our equipment a photon current density of 1 photon/s/cm2 can be detected at a significance level of 99.9% within 10 hours. The uptake of count numbers within given time intervals and calculations are carried out with an interfaced computer.

An experimental appraisal of the terms in the heat and moisture flux equations for local advection

Abstract: Terms in the heat and vapour flux equations, appropriate to the atmospheric surface layer with horizontal heterogeneity in one direction, have been evaluated empirically. The experimental site was a flooded rice field, which was bounded to windward by a semi-arid region. Local conditions over the rice were always stable, but the vertical fluxes of heat and water vapour were large. All terms in the flux equations were either measured directly, or, if sufficiently small, estimated, except the term containing fluctuating pressure, which was obtained by difference. The relative magnitudes of the major terms (production and pressure covariance) were similar to those reported previously for horizontally homogeneous flow with similar stabilities. Current parameterizations of the pressure covariance terms sometimes gave values which differed by factors of five or ten from the experimental results, and the interrelationships depended upon the stability.

Consideration of the frequency performance potential of GaAs homojunction and heterojunction n-p-n transistors

Abstract: A study is made of the expected frequency performance of n-p-n GaAs homojunction transistors and n-p-n AlGaAs-GaAs heterojunction transistors. The analysis suggests that if parasitic base resistance is minimized in the homojunction transistor design, the frequency performance should be comparable to that of heterojunction transistors of similar dimensions.

Phase Equilibria in the Systems Rare‐Earth Sesquioxide‐Beryllium Oxide

Abstract: Phase equilibria in systems comprised of a rare-earth or yttrium sesquioxide and beryllia were studied. Two types of beryllates, stable and metastable, with molecular ratios of 1:2 and 3:2, were found: their formation and stability are discussed in terms of crystal chemistry.

Liquid Crystal Research in China: 1970-1982

Abstract: Liquid crystal was discovered in 1888. However, it was only after the observation of dynamic scattering in nematics in 1968 and the subsequent application in displays that liquid crystal, as a field of research, has obtained its vitality and importance as we know it today.† Not surprisingly, it was in the early years of this modern era of liquid crystals that China ventured into this exciting “new” field.1-16

Novel design of travelling-wave FET

Abstract: In the letter we propose a novel travelling-wave FET, in which an additional image gate is placed beside the drain of the FET as a phase velocity synchroniser. Small-signal analysis is given in the light of coupled wave theory and shows that the device is capable of high gain and wide bandwidth amplification. The easy adjustment of phase synchronisation and compability of the conventional FET fabrication technique make it promising for high-frequency distributed amplification.

Topographical changes induced by low energy ion beam sputtering at oblique incidence

Abstract: When niechanically polished Ge, Si, GaAs, LiNbOj, Cd-Ga-garnet, fused quartz and glass surfaces are sputtered by low energy ion beam (from 300 to 1200 eV) at an incident angle of 45°, the surfaces are found to exhibit hillock-like features. The influence of ion beam incident angle, energy, dose and target rotation on surface topography have been investigated. The analysesof hillocks by SIMS and AES show that their formation may not be due to impurity contamination caused by redeposition. A mechanism for hillock formation is proposed. This can be expressed by aformula, through which all the results can be successfully explained.

Submicron filament multistrand powder metallurgy processed Cu-Nb-Sn wire

Abstract: Submicron size ultrafine Cu-Nb-Sn superconducting wire has been fabricated by the powder metallurgy process simulating large scale industrial fabrication using the bundling technique. Starting copper and niobium powders ranged from 250 to 500 μm. Both external and tin core processed wires were fabricated with overall current densities of J_{c} \sim 2-3 \times 10^{4} A/cm2at 14 T, demonstrating that both particle size and billet can be scaled up to large scale fabrication.

Bifunctional interaction and its effect on the esterification of dicarboxylic acids in chemical ionization mass spectrometry

Abstract: The chemical ionization mass spectra of different dicarboxylic acids, including saturated and unsaturated aliphatic, aromatic, hydroxyl and amino-substituted dicarboxylic acids, have been studied using pure methanol as the reagent gas. Biomolecular monoesterification and diesterification product ions [M+15]+ and [M+29]+, and adduct ion [M+33]+, were observed, in addition to the protonated molecule [MH]+ and unimolecular water elimination product ions. The formation of a protonated molecule with bridged intramolecular hydrogen bond, and its effect on the esterification of dicarboxylic acids is discussed. Geometric isomers, such as maleic and fumaric acid, and ortho and meta isomers of phthalic acids can be distinguished from each other by methanol chemical ionization mass spectra. When ethanol was used as the reagent gas, similar mass spectra of some dicarboxylic acids were obtained.

Lateral symmetry in duration of grasp by infants

Abstract: The mean duration for which Chinese infants aged 63 to 135 days (mean age 94 days) maintained grasp of a rattle did not differ consistently between the left hand and the right hand. This result contrasts with the asymmetry in grasp favouring the right hand found by Caplan and Kinsbourne with infants of similar ages using the same procedures.

Thalifaberine, thalifabine and huangshanine, three new dimeric aporphine-benzylisoquinoline alkaloids.

Abstract: La thalifaberine et l'huangshanine possedent des proprietes cytotoxiques pour les cellules d'epithelioma Walker 256