New data on the morphology and systematic status of Spinitectus petrowi and Spinitectus gigi (Nematoda : Cystidicolidae) parasitic in catfishes in central China

Two little-known nematode species of the genus Spinitectus Fourment, 1883, S. petrowi Belous, 1965 (prevalence 25%, intensity 1-8) and S. gigi Fujita, 1927 (prevalence 10%, intensity 2-3), were collected from the gastrointestinal tract of the yellow catfish, Pelteobagrus fulvidraco (Richardson), from Liangzihu Lake, Hubei Province, central China, in September of 2002. The light and scanning electron microscopical examination of this material, supplemented by a few museum specimens of S. gigi collected from the catfish Clarias fuscus (Lacepede) in southern China, made it possible to study in detail the morphology of these parasite species and to redescribe them. The first species, whose correct name is S. petrowi Belous, 1965, exhibits some morphological features (e.g., unusually short vestibule, shape of pseudolabia and of the left spicule) not found in most other congeners; a unique feature is the presence of peculiar pairs of transversely oriented peg-like cuticular spines with rounded ends on the ventral surface of the female tail. Spinitectus gigi was found to have 28-31 cuticular spines in the first ring, relatively long distances between the 2nd-7th rings of spines, and anterior rings divided into 2 sectors; the excretory pore is located at the level of the 4th ring of cuticular spines; males posses 4 pairs of preanal- and 6 pairs of postanal caudal papillae and a pair of small phasmids. Spinitectus bagri Wang, Wu et Yu, 1993 and S. wulingensis Yu et Wang, 1997 are considered junior synonyms of S. petrowi, whereas S. clariasi Ky, 1971, S. ophicephali Ky, 1971 and S. yuanjiangensis Wang, Wit et Yu, 1997 are regarded to be junior synonyms of S. gigi. Spinitectus petrowi was not previously reported from China.

Silver carp, Hypophthalmichthys molitrix, in the Poyang Lake belong to the Ganjiang River population rather than the Changjiang River population

The Poyang Lake is the largest lake and the main nursery area in the middle basin of the Changjiang (Yangtze) River. We compared molecular genetic markers of silver carp among populations of the Changjiang River, the Ganjiang River and the Poyang Lake using the ND5/6 region of mtDNA. Analysis of restriction fragment length polymorphisms (RFLPs) of this region revealed distinct variation between the Ganjiang River and the Changjiang River populations. The Poyang Lake is linked with the Ganjiang River and the Changjiang River. Shared RFLP fragments between the Ganjiang River population and the Poyang Lake population are as high as 61.4%. The value is 47.74% between the populations of the Changjiang River and that of the Poyang Lake. Frequencies of bands peculiar to the Ganjiang River population are the same as in the Poyang Lake population. We conclude that the Poyang Lake silver carp population consists mainly of the Ganjiang River population. The water level of the Poyang Lake outlet, which is higher than that of the Changjiang River in the silver carp spawning season, supports this conclusion.

Distribution, transformation, and long-term accumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans in different tissues of fish and piscivorous birds

The present study monitored 10-year-old fish and piscivorous birds from sites contaminated for many Stars. The data reflected the results of actual, long-term environmental exposures, The results demonstrate that different tissues of fish have quite different concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), The concentration order of PCDD/F within fish is liver congruent to egg congruent to intestines kidney congruent to hearts gill congruent to bladders > muscle > brain. The concentration order of PCDD/F within piscivorous birds was livers egg congruent to hearts muscle congruent to stomachs brain, The results obtained also demonstrate that the accumulation patterns of piscivorous birds and fish are quite different. The tissues of fish and piscivorous birds have different capacities for bioaccumulation and biotransformation of PCDD/F; variable proportions of TEQs were also found throughout their bodies. In fish, toxic equivalency quotient (TEQ): PCDD/F ratios in various tissues ranged from 0.01 to 0.07, whereas in birds the ratios ranged from 0.07 to 0.43. If the concentrations are normalized with lipid content, the results vary less. The effect of different lipid properties is obvious in the case of brain tissue, which is richer in phospholipids. (C) 2000 Academic Press.

The role of sense organs in the feeding behaviour of Chinese perch

Experiments were conducted to identify the rules of the individual sense organs in the feeding behaviour of Chinese perch Siniperca chuatsi by determining the consumption of natural food after selective removal or blocking of eyes, lateral lines and olfactory organs, and also by observing the behavioural response to visual, mechanical and chemical stimulation by artificial prey. Chinese perch were able to feed properly on live prey fish when either eyes or lateral lines were intact or functional, but could scarcely feed without these two senses. Chinese perch recognized its prey by vision through the perception of motion and shape, and showed a greater dependence on vision in predation when both visual and mechanical cues were available. Chemical stimulation by natural food could not elicit any feeding response in Chinese perch, and gustation was only important to the fish for the last stage of food discrimination in the oropharyngeal cavity. The sensory basis of Chinese perch in feeding is well adapted to its nocturnal stalking hunting strategy. and also explains its peculiar food habit of accepting live prey fish only and refusing dead prey fish or artificial diets. (C) 1998 The Fisheries Society of the British Isles.

Characteristics of band structures in 1D photonic crystals containing alternate left-right handed materials

This work investigated analytically the band structure of photonic crystals (PCs) with alternate layers of left and right-handed materials in one-dimension. It was found that, under certain conditions, new peculiar band structures not seen in all right-handed material PCs appeared. We transformed the analytic dispersion relation into two cosine terms, and obtained an interesting band structure using the new form of dispersion equation. Conditions for obtaining such peculiar band structure were given. (c) 2005 Elsevier Ltd. All rights reserved.

Unusual carrier thermalization in a dilute GaAs1-xNx alloy

Photoluminescence (PL) properties of the E-0, E-0+Delta(0), and E+ bands in an x=0.62% GaAs1-xNx alloy were investigated in detail, including their peak position, linewidth, and line shape dependences on the excitation energy, excitation power, and temperature, using micro-PL. The hot electrons within the E+ band are found to exhibit highly unusual thermalization, which results in a large blueshift in its PL peak energy by >2k(B)T, suggesting peculiar density of states and carrier dynamics of the E+ band.

Storage of photoexcited electron-hole pairs in an AlAs/GaAs heterostructure created by electron transfer in real and kappa spaces

The storage of photoexcited electron-hole pairs is experimentally carried out and theoretically realized by transferring electrons in both real and k spaces through resonant Gamma - X in an AlAs/GaAs heterostructure. This is proven by the peculiar capacitance jump and hysteresis in the measured capacitance-voltage curves. Our structure may be used as a photonic memory cell with a long storage time and a fast retrieval of photons as well.

Effect of channel surface wettability and temperature gradients on the boiling flow pattern in a single microchannel

The objective of this paper is to investigate the effects of channel surface wettability and temperature gradients on the boiling flow pattern in a single microchannel. The test section consists of a bottom silicon substrate bonded with a top glass cover. Three consecutive parts of an inlet fluid plenum, a central microchannel and an outlet fluid plenum were etched in the silicon substrate. The central microchannel had a width of 800 mu m and a depth of 30 mu m. Acetone liquid was used as the working fluid. High outlet vapor qualities were dealt with here. The flow pattern consists of a fluid triangle (shrinkage of the liquid films) and a connected long liquid rivulet, which is generated in the central microchannel in the timescale of milliseconds. The peculiar flow pattern is formed due to the following reasons: (1) the liquid rivulet tends to have a large contact area with the top hydrophilic channel surface of the glass cover, but a smaller contact area with the bottom silicon hydrophobic surface. (2) The temperature gradient in the chip width direction at the top channel surface of the glass cover not only causes the shrinkage of the liquid films in the central microchannel upstream, but also attracts the liquid rivulet populated near the microchannel centerline. (3) The zigzag pattern is formed due to the competition between the evaporation momentum forces at the vapor-liquid interfaces and the force due to the Marangoni effect. The former causes the rivulet to deviate from the channel centerline and the latter draws the rivulet toward the channel centerline. (4) The temperature gradient along the flow direction in the central microchannel downstream causes the breakup of the rivulet to form isolated droplets there. (5) Liquid stripes inside the upstream fluid triangle were caused by the small capillary number of the liquid film, at which the large surface tension force relative to the viscous force tends to populate the liquid film locally on the top glass cover surface.

Simultaneous multiwavelength observations of sagittarius A

We observed Sgr A* using the Very Large Array (VLA) and the Giant Metrewave Radio Telescope (GMRT) at multiple centimeter and millimeter wavelengths on 2003 June 17. The measured flux densities of Sgr A*, together with those obtained from the Submillimeter Array (SMA) and the Keck II 10 m telescope on the same date, are used to construct a simultaneous spectrum of Sgr A* from 90 cm to 3.8 mu m. The simultaneous spectrum shows a spectral break at about 3.6 cm, a possible signature of synchrotron self-absorption of the strong radio outburst that occurred near epoch 2003 July 17. At 90 cm, the flux density of Sgr A* is 0.22 +/- 0.06 Jy, suggesting a sharp decrease in flux density at wavelengths longer than 47 cm. The spectrum at long cm wavelengths appears to be consistent with free-free absorption by a screen of ionized gas with a cutoff similar to 100 cm. This cutoff wavelength appears to be three times longer than that of similar to 30 cm suggested by Davies, Walsh, & Booth based on observations in 1974 and 1975. Our analysis suggests that the flux densities of Sgr A* at wavelengths longer than 30 cm could be attenuated and modulated by stellar winds from massive stars close to Sgr A*.

Two-component model for the interstellar scattering in direction to the Vela pulsar

This paper discusses a rigorous treatment of the refractive scintillation of pulsar PSR B0833-45 caused by a two-component interstellar scattering medium. It is assumed that the interstellar scattering medium is composed of a thin screen ISM and an extended interstellar medium. We consider that the scattering of the thin screen concentrates in a thin layer presented by a delta function distribution and that the scattering density of the extended irregular medium satisfies the Gaussian distribution. We investigate and develop equations for the flux density structure function corresponding to this two-component ISM geometry in the scattering density distribution and compare our result with that of the Vela pulsar observations. We conclude that the refractive scintillation caused by this two-component ISM scattering gives a more satisfactory explanation for the observed flux density variation of the Vela pulsar than does the single extended medium model. The level of refractive scintillation is strongly sensitive to the distribution of scattering material along the line of sight. The logarithmic slope of the structure function is sensitive to thin screen location and is relatively insensitive to the scattering strength of the thin screen medium. Therefore, the proposed model can be applied to interpret the structure function of flux density observed in pulsar PSR B0833-45. The result suggests that the medium consists of a discontinuous distribution of plasma turbulence embedded in the Vela supernova remnant. Thus our work provides some insight into the distribution of the scattering along the line of sight to the Vela pulsar.

Revision of Yunnanilus with descriptions of a miniature species flock and six new species from China (Cypriniformes: Homalopteridae)

The genus Yunnanilus Nichols, 1925 is revised; Eonemachilus Berg, 1938 is a junior subjective synonym. Yunnanilus includes at least nine described species and five undescribed species. The status of Y; salmonides Chaudhuri is still incertae sedis. Six new species are described: Y. parvus, Y: altus, Y; pachycephalus, X niger, Y. macrogaster and Y. paludosus. The last three species occur sympatrically in a small endorheic basin of eastern Yunnan; they developed different feeding specializations which allowed them to use different niches. Other species also have peculiar specializations. The diversity of feeding habits and related adaptations in Yunnanilus is greater than in the whole subfamily Nemacheilinae and is one more example of supralimital specialization. Speciation of fishes on the Yunnan Plateau is discussed. Several species are endangered or possibly extinct. Introduction

THEORETICAL INVESTIGATION OF THE DYNAMIC PROCESS OF THE ILLUMINATION OF GAAS

The dynamic process of light illumination of GaAs is studied numerically in this paper to understand the photoquenching characteristics of the material. This peculiar behavior of GaAs is usally ascribed to the existence of EL2 states and their photodriven metastable states. To understand the conductivity quenching, we have introduced nonlinear terms describing the recombination of the nonequilibrium free electrons and holes into the calculation. Though some photoquenching such as photocapacitance, infrared absorption, and electron-paramagnetic-resonance quenching can be explained qualitatively by only considering the internal transfer between the EL2 state and its metastability, it is essential to take the recombination into consideration for a clear understanding of the photoquenching process. The numerical results and approximate analytical approach are presented in this paper for the first time to our knowledge. The calculation gives quite a reasonable explanation for n-type semiconducting GaAs to have infrared absorption quenching while lacking photoconductance quenching. Also, the calculation results have allowed us to interpret the enhanced photoconductance phenomenon following the conductance quenching in typical semi-insulating GaAs and have shown the expected thermal recovery temperature of about 120 K. The numerical results are in agreement with the reported experiments and have diminished some ambiguities in previous works.

A NEW RESULT IN TRANSIENT CURRENT EXPERIMENT ON A-SI-H P/I/N AND N/I/N DEVICES

The transient current response of a-Si:H in both p/i/n and n/i/n structures has been measured as a function of pulse intermittence and pulse amplitude. The results are consistent with the picture that in p/i/n samples the peculiar current response is caused by the competing contributions of electrons and holes which show themselves in different time scales.

一种新奇的甲烷氧化细菌——能兼性营养和厌氧生长的沼气甲基弯菌

经过细心的条件选择实现了无甲烷条件下甲烷氧化菌沼气甲基弯菌81Z(methylosinus methanica 81Z)利用C2化合物的生长，同时 发现二碳代谢中间产物甘氨酸的胞外积累及对生长的抑制作用。又在此基础上从81Z原种中富集得到一株菌81Z-A，兼性生长能力大 幅度提高，而且除乙酸外又能利用丙酮酸、苹果酸、柠檬酸、葡萄糖而生长。对细胞氧化各种有机底物时氧吸收的测定及酶分析结 果发现了在其它甲烷氧化细菌中未曾发现的异柠檬酸裂解酶和苹果酸酶的存在，表明81Z除了具有通常II型菌的碳代谢途径外，具 有特殊的补偿代谢途径——乙醛酸支路以及从乙酸生糖的回补途径。因此推证其兼性生长的能力是固有的，从而说明了甲烷氧化菌 的专一性概念没有普遍意义。说明了81Z还能在含有二碳的培养基中厌氧生长，包括细胞的分裂和增值行为。虽然这种厌氧生长还 很弱，但至少可以说明它不是严格好氧的，这对于传统的关于甲烷氧化菌的严格好氧的概念是一个冲击。81Z正常条件下是利用甲 烷而生长的，当供给它乙酸、乙醛酸和丝氨酸时能促进含C-C键有机物氧化的活性，而对甲烷单加氧酶和其它C2化合物的氧化有抑 制或阻遏作用，对碳同化的丝氨酸途径的关键酶羟基丙酮酸还原酶有阻抑作用。同时也证明了81Z的甲烷单加氧酶和甲醇氧化活性 可被甲烷、甲醇所诱导，而因甲酸而降低。The growth of Methylosinus methanica 81Z on C2-compounds without methane was realized by selecting suitable conditions. The intermediate product Gly from its C2 metabolism was found to accumulate out cells and inhibit its growth. 81Z-A, which was obtained from 81Z by richening, could grow on C2- compounds rapidly. It can even grow on pyruvate, malate, citrate and glucose. The results of measurements of oxygen consumption by cell suspensions in the presence of various organic compounds and the results of enzyme assays of detected activities of isocitrate lyaze and malic enzyme in cell extracts which were not found in other methantrophs showed that 81Z possesses not only the regular carbon metabalic pathways but also some peculiar anaplerotic pathways--the glyoxylate cycle and the gluconeogenic pathway from acetate. As a consequence of these studies, its ability of facultative growth is inherent. Therefore, the concept of obligate dependence on C2- compounds of methanotrophs is not of universal significance. The ability of 81Z's growth(including desintegration and proliferation behaviour) on C2-compounds anaerobically was also demonstrated. Despite of the weakness of this growth, at least it could be said that 81Z is not strictly aerobic. This is a strike to the traditonal concept about the strictly aerobic action of methanotrophs. Regularly, 81Z grows on methane. The presence of acetate, glyoxylate and serine could increaze its ability of oxidizing the organic coumpounds containing C-C ponds. In contrast, they could inhibit the activities of MMO and other C2-compounds oxidation, they also repressed the key enzyme hydroxypyruvate reductase of the serine-pathway for carbon assimilation. At the some time, it was testified that the activities of MMO and methanol oxidation were inducible by methane or methanol and were lower in the presence of formate.

Triton-He-3 relative and differential flows as probes of the nuclear symmetry energy at supra-saturation densities

Using a transport model coupled with a phase-space coalescence afterburner, we study the triton-He-3 (t-He-3) ratio with both relative and differential transverse flows in semicentral Sn-132 + Sn-124 reactions at a beam energy of 400 MeV/nucleon. The neutron-proton ratios with relative and differential flows are also discussed as a reference. We find that similar to the neutron-proton pairs, the t-He-3 pairs also carry interesting information regarding the density dependence of the nuclear symmetry energy. Moreover, the nuclear symmetry energy affects more strongly the t-He-3 relative and differential flows than the pi(-)/pi(+) ratio in the same reaction. The t-He-3 relative flow can be used as a particularly powerful probe of the high-density behavior of the nuclear symmetry energy.