Showing papers by "Chinese Academy of Sciences published in 1986"

Influence of nonlinear incidence rates upon the behavior of SIRS epidemiological models

Abstract: When the traditional assumption that the incidence rate is proportional to the product of the numbers of infectives and susceptibles is dropped, the SIRS model can exhibit qualitatively different dynamical behaviors, including Hopf bifurcations, saddle-node bifurcations, and homoclinic loop bifurcations. These may be important epidemiologically in that they demonstrate the possibility of infection outbreak and collapse, or autonomous periodic coexistence of disease and host. The possible mechanisms leading to nonlinear incidence rates are discussed. Finally, a modified general criterion for supercritical or subcritical Hopf bifurcation of 2-dimensional systems is presented.

Probable loss of chlorophyll‐derived pigments during passage through the gut of zooplankton, and some of the consequences

Abstract: By use of biogenic silica as an inert marker, it is shown that chlorophyll a and its derivatives can be destroyed or absorbed during passage through the gut of a herbivorous copepod. This observation is contradictory to the hypothesis that chlorophyll a is converted to pheophorbide a with 100% molar efficiency. The currently used equations for measuring chlorophyll and pheopigment by fluorescence cannot be used to give concentration of phcopigment. Determining quantitatively the role of zooplankton as intermediates in material and energy transfer in aquatic food chains remains a formidable challenge for biological oceanographers. Several kinds of in vivo or in situ techniques have been developed to avoid the lengthy incubations usually required to measure grazing rates in the laboratory, with their attendant problems of interpretation and application. Probably the most widely used of these is the gut chlorophyll method (Mackas and Bohrer 1976). The usefulness of this technique to examine short term variability in zooplankton feeding has been frequently demonstrated (Boyd et al. 1980; Dagg and Grill 1980; Dagg and Wyman 1983; Nicolajsen et al. 1983; Head et al. 1984). On the other hand, there have been relatively few attempts to relate ingestion based on gut pigment contents with ingestion derived from conventional grazing experiments and, when this has been attempted, the results have been contradictory. Kiorboe et al. (1982) carried out a parallel series of grazing experiments and gut chlorophyll ingestion measurements under the same conditions of food and temperature, but at different times, and then used somewhat different models to describe their results, concluding that the agreement was good enough to make (p. 192) “the prospects for application of the indirect method (i.e. gut pigment method) to field situations promising.” Wang and Conover (1986) addressed the same problem by measuring the accumulation of gut pigment and the rate of its removal by grazing simultaneously, but they found that more chlorophyll was ingested than could be accounted for by that found in the gut and that disappearing from the animal during defecation. Several possible explanations for the discrepancy between the ingestion rates generated by the two methods in Wang and Conover’s ( 1986) studies come to mind. First, to convert the level of gut pigment in an animal to a rate of ingestion requires an estimate of gut turnover or evacuation rate, which are assumed to be equivalent. Evacuation rate is usually determined from loss of gut pigment in previously fed animals after transfer to filtered seawater (Mackas and Bohrer 1976; Dagg and Grill 1980; Kiorboe et al. 1982; Wang and Conover 1986). However, an evacuation rate for starving animals might underestimate turnover rate for those that are feeding regularly. Or alternatively there could be loss of pigment, perhaps through exposure to light or carbon dioxide or as a consequence of freezing (Nicolajsen et al. 1983). Or conceivably, a portion of the pigment actually ingested is digested or destroyed in the gut. Wang and Conover (1986) examined these several possibilities and concluded that pigment destruction by the digestive process was the most probable explanation. Here we test this hypothesis. In their original description of the gut pigment method, Mackas and Bohrer (1976)

Comparative study of behavioral qualities of only children and sibling children

Abstract: 993 children from rural and urban kindergartens aged 4-6 and primary schools aged 9-10 from Beijing and surrounding communes participated in a study comparing only children and siblings in which the children rated each other in matched pairs for 7 behavioral characteristics. The kindergarten children rated photographs of their peers in answer to set questions and the schoolchildren answered 22 questions about their peers by name. The characteristics examined were independent thinking persistence behavior control frustration cooperation peer prestige and egocentrism (self-direction). Both rural and urban siblings had higher scores on cooperation and peer prestige than did only children. Only children were more egocentric considered a negative quality. Urban kindergarten sibling children were more persistent than only children. Urban kindergarten only children showed more independent thinking than sibling children yet urban school siblings were more independent than only children. Urban sibling schoolchildren scored higher on all the positive qualities except behavior control while their only children peers scored higher on the negative quality of egocentrism. Older only children had higher scores for behavior control. Kindergarten teachers often noted that only children had low self-control when frustrated. There were no significant associations between behavior scores and parental education or occupation or type of family by number of generations living together. Cooperation and peer prestige were thought to be related and both were enhanced by siblings in the family.

Dynamics of gut pigment in the copepod Temora longicornis and the determination of in situ grazing rates

Abstract: Gut fluorescence attributable to algae caten by an herbivorous zooplankter should be a function of chlorophyll consumption minus loss of pheopigments in defecation. The amount of chlorophyll ingested, as determined in a laboratory grazing experiment, minus the gut pigment content at the end in the grazers, should equal chlorophyll dcfecatcd and should also provide a calibration for the determination of evacuation rate in filtered seawater. The kinetics of gut filling and emptying in Temora Iongicornis have been studied at different food concentrations. Neither is constant with time. Filling rate is positively correlated with food concentration but gut pigment content may be maximal at lower concentrations when food supply is presumably still limiting. Evacuation rates, while not constant, are independent of initial gut chlorophyll content or food concentration in the experimental environment over a range from 0.5 to 8 mm3 liter-’ of Coulter Counter volume. Ingestion rates determined from gut pigment concentration and gut clearance time and those determined from filtration rate were directly correlated (slope = 1) but showed a systematic difference apparently caused by undetected loss of gut pigment. An improved method for determining in situ grazing rates from gut pigment measurements is proposed.

[Dynamics of regional ecological frangibility under natural hazard stress: a case study in Qingping Town of Sichuan Province, Southwest China].

Abstract: By using the aerial remote sensing images after May 12, 2008 (the date of catastrophic Wenchuan Earthquake) and the unmanned aircraft vehicle remote sensing images after August 13, 2010 (the date of extraordinary debris flow), and in combining with the land use map (1:10000), topographic map (1:50000), and collected field investigation data of Qingping Town, Mianzhu City of Sichuan Province in 2006, this paper analyzed and evaluated the ecological frangibility of the Town. In the Town, the slightly, lightly, moderately, heavily, and extremely fragile ecological zones after the extraordinary debris flow occupied 1.9%, 7.9%, 18.7%, 23.0%, and 48.5%, respectively, with the area of heavily and extremely fragile ecological zones accounting for 71.5% of the total, being 238.45 km2, i. e., the ecological environment was overall very fragile. Under the impact of the two natural hazards, the ecological frangibility degree of the Town increased obviously. As compared with that before the Earthquake, the area of heavily and extremely fragile ecological zones after the Earthquake increased by 12.4%, and the area of extremely fragile ecological zone was 1.67 times larger. The dynamic evolution of the ecological frangibility of the Town was mainly manifested in the conversion of heavily fragile ecological zone into extremely fragile ecological zone. Complex terrain was the key factor of the ecological frangibility of the Town.

Levels of Isopenicillin N Synthetase and Deacetoxycephalosporin C Synthetase in Cephalosporium acremonium Producing High and Low Levels of Cephalosporin C

Abstract: Levels of Isopenicillin N Synthetase and Deacetoxycephalosporin C Synthetase in Cephalosporium acremonium Producing High and Low Levels of Cephalosporin C

Monolayer films of a substituted silicon phthalocyanine

Abstract: This paper describes the preparation and properties of Langmuir-Blodgett films of tetra-4-tert-butyl phthalocyaninatosilicon dichloride (ttb PcSiCl2). Our experiments indicate the relative ease with which films of this material can be prepared compared with similarly substituted compounds. All the isotherm, optical and electrical data are consistent with the molecules being stacked edge-on to the substrate with the molecular faces having a preferred orientation perpendicular to the dipping direction. The uniformity of the films is reflected in their ability to sustain high electric fields; their electrical resistivity perpendicular to the substrate is approximately 5 × 105Ωcm.

Optical determination of alkali metal vapor number density using Faraday rotation

Abstract: We present a convenient and reliable method for measuring the number density of the alkali metal vapor. The method is based on the diamagnetic Faraday rotation of the plane of polarization of nearly resonant light by the alkali metal vapor, and it is suitable for optically thick vapor where the conventional integrated absorption technique fails.

Aerosol Charge Neutralization by a Radioactive Alpha Source

Abstract: The performance of a Po-210 radioactive ionizer for aerosol charge neutralization and bipolar charging has been evaluated. Monodisperse neutral and singly charged aerosols have been passed through the ionizer and their approach to the steady-state Boltzmann charge measured by measuring the fraction of particles that are electrically charged. The result shows that an Nt of approximately 2.5 × 105 cm−3 s is needed for the development of a steady-state charge fraction equal to that given by the Boltzmann' s law where N is the ion concentration and t is the residence time of the aerosol in the neutralizer. In addition, the performance of the ionizer for particle charge neutralization in a vibrating-orifice aerosol generator has been evaluated and the result shows that the source is less effective for this application and the residual charge on the particles is considerably higher than that given by the Boltzmann's law.

Atmospheric pollution from coal combustion in China

Abstract: Coal combustion is the primary contributor to atmospheric pollution in China, especially so In big cities. Particulate matter and sulfur dioxide are the two main pollutants worthy of attention. Concentration of suspended particles is usually higher in northern cities than in southern cities and higher in winter than in summer. In the case of sulfur dioxide, concentrations are high in the heating season (wintertime) in northern cities, but also in some of the cities in the southwest part of China. Rainfall with pH less than 5.6 occurs mostly to the south of the Yangtze River, especially so in the cities of Chongqing and Gueiyang, and their neighboring areas, and also In the southwest part of China. No acid rain, however, has been found in Beijing and Tianjin. Although the formation of acid rain can thus be thought of as dependent on the presence of enough sulfur dioxide, other factors such as airborne particles and ammonia also play an important role. The difference is, therefore, explained and theorem pos...

An Investigation of the Summer Lows over the Qinghai-Xizang Plateau

Abstract: Low pressure areas over the Qinghai-Xizang Plateau on the 500 hPa level in the summer half year are found to be one of the major systems producing rainfall there[1]. In our investigation, 11 similar cases of occurrence of these lows are sorted out from the observations made during the first QXPMEX. Their structure is studied, using the compositing method[2] and taking the mean 500 hpa low center (denoted in the Figures as ▲) as the reference low center. The climatological factors favorable for the development of these lows are also discussed.

Direct observation of the transformation of the icosahedral phase in (Al6Mn)1−xSix, into α(AlMnSi)

Abstract: In-situ heating of the icosahedral phase in (Al6Mn)1−xSix, x = 0·02 and 0·04, in a Philips EM420 electron microscope leads to the formation of α(AlMnSi) and Al6Mn crystalline phases. The orientation relationship between the icosahedral phase and the α phase is found to be as suggested by Guyot and Audier, and Elser and Henley.

The synchrotron-maser theory of type II solar radio emission processes - The physical model and generation mechanism

Abstract: A theory is proposed to explain the generation mechanism of type II solar radio bursts. It is suggested that the shock wave formed at the leading edge of a coronal transient can accelerate electrons. Because of the nature of the acceleration process, the energized electrons can possess a 'hollow-beam' type distribution function. When the electron beam propagates along the ambient magnetic field to lower altitudes and attains larger pitch angles, a synchrotron-maser instability can set in. This instability leads to the amplification of unpolarized or weakly polarized radiation. The present discussion incorporates a model which describes the ambient magnetic field and background plasma by means of MHD simulation. The potential emission regions may be located approximately, according to the time-dependent MHD simulation. Since the average local plasma frequency in the source region can be evaluated from the MHD model, the frequent drift associated with the radiation may be estimated. The result seems to be in good agreement with that derived from observations.

One-to-one correspondence between Kekulé and sextet patterns

Abstract: The concept of super sextet is clarified and the generalized sextet polynomial in two elements is proposed. Two theorems related to Ohkami-Hosoya conjecture [1] are proved and one novel conjecture is proposed.

The Qinghai-Xizang Plateau Meteorological Experiment (Qxpmex) May–August 1979

Abstract: Many earlies studies have pointed out that the Qinghai-Xizang Plateau strongly influences the weather and climate of China, even the general circulation of the world. If one does not include the influence of the Qinghai-Xizang Plateau in the numerical simulation, the mean circulation and the characteristics of climate seem to conflict with the reality of the present situation, but after due consideration one can see that they are not so very incongruous after all. We have yet to understand well the exact reasons for the Plateau’s influence, neither have we been able to conclude much from some of the important observational facts. For these reasons we have mounted the Qinghai-Xizang Plateau Meteorological Plateau Meteorological Experiment (QXPMEX) in May–August 1979, during the same period as the MONEX. The main objectives of the experiment were to investigate the thermal and dynamic effects of the Plateau on the general circulations in Eastern Asia, the radiation and heat budget on the surface on the Plateau and the weather on the Plateau under various synoptic conditions. The QXPMEX was divided into three phases: the experiment design phase (1978), the actual field observing phase (May–August, 1979) and the research phase (1980 and 1981). More than 100 scientists from various research institutes, provincial weather bureaus and universities participated in the experiment. The cost of the experiment was about 3 million Yuan.

A convergence theorem of Rosen's gradient projection method

Abstract: Since Rosen’s gradient projection method was published in 1960, a rigorous convergence proof of his method has remained an open question. A convergence theorem is given in this paper.