人工诱导贻贝Mytilus edulis Linnaeus幼虫附着变态的研究

许多天然物质和人为的外界生物化学因子对许多无脊椎动物附着变态有诱导作用，这为人工控制无脊椎动物幼虫的附着变态过程提供了重要手段，同时对于幼虫培养，特别是对于经济种类幼虫的培养和育苗，具有重要的意义。本文以青岛贻贝Mytilus edulis Linnaeus为研究对象，于1990年1991年分别就不同的海水离子条件、拟肾上腺素和抗肾上腺素、拟胆碱和抗胆碱类化合物以及促进生物新陈代谢类化合物对贻贝幼虫附着变态的诱导作用进行了研究，结果表明：升高K~+或Ca~++浓度以及降低Mg~++浓度均对贻贝幼虫有附着变态诱导作用。Mg~++浓度降低促进K~+的诱导作用。氨基酸类神经递质GABA和其同系物天冬氨酸、谷氨酸、苷氨酸、β－丙氨酸无明显附着变态诱导作用。短时间内，L－DOPA诱导水平（30％）贻贝幼虫不经过附着而直接变态，只作用于β－受体的拟肾上腺素、多巴胺和异丙肾上腺素诱导50％水平的幼虫变态。作用于α－受体的拟肾上腺素、间羟胺、麻黄碱、去氧肾上腺素、去甲肾上腺素和肾上腺素诱70－90％水平的幼虫变态。阻断β－受体的抗肾上腺素、噻吗心安和心得安无诱导作用。但阻断β－受体的抗肾上腺素、立其丁、酚苄明和妥拉苏林对幼虫附着变态有诱导作用。干扰肾上腺素能神经递质释放的化合物利血平无变态诱导作用，并有致死作用。拟胆碱类分合物苯海过、琥珀酰胆碱和阿托品对贻贝幼虫均有附着变态诱导作用。变态诱导率维持在30％水平。拟胆碱化合物加兰他敏有较高的变态诱导率（56.1% (10~(-3)M, 36h)）。抗胆碱类化合物氯丙嗪无明显诱导作用。调节生物体代谢和机能类化合物甲状腺素、ATP、肌、VitB_6和氨茶碱对贻贝幼虫有显著的附着变诱导作用，变态诱导率分别为：甲状腺素84.6 (10~(-3)M, 36h)；ATP 57.7% (10~(-3)M, 36h)；肌苷74.0% (10~(-3)M, 36h); VitB_6 41.3% (10~(-5)M, 36h)和氨茶碱50.0% (10~(-4)M, 36h)。前列腺素无诱导作用，而氯化可的松有一定诱导作用。去甲肾上腺素和乙酰胆碱对幼虫变态的诱导作用被Na~+通道阻断剂普鲁卡因和利多卡因阻断。但ATP和氨茶碱的诱导作用不被其阻断。这表明去甲肾上腺素和乙酰胆碱对幼虫的附着变态的诱导作用是通过视经传递完成的。而神经传递并没有参与ATP和氨茶碱对幼虫变态的诱导过程。

Experimental investigation of an unstable ring resonator with 90-deg beam rotation for a chemical oxygen iodine laser

We report the experimental results of an unstable ring resonator with 90-deg beam rotation for a kilowatt class chemical oxygen iodine laser (COIL). The distributions of near-field phase and far-field intensity were measured. A beam quality of 1.6 was achieved when the COIL average output power was approximately 5 kW. (C) 1999 Optical Society of America.

Control of vortex shedding at moderate Reynolds numbers

The suppression method of vortex shedding from a circular cylinder has been studied experimentally in the Reynolds number range from 300 to 1600. The test is performed in a water channel. The model cylinder is 1 cm in diameter and 38 cm in length. A row of small rods of 0.18 cm in diameter and 1.5 cm in length are perpendicularly connected to the surface of the model cylinder and distributed along the meridian, The distance between the neighboring rods and the angle of attack of the rods can be changed so that the suppression effect on vortex shedding can be adjusted. The results show that vortex shedding can be suppressed effectively if the distance between the neighboring rods is smaller than 3 times and the cylinder diameter and the angle of attack is in the range of 30degreesless than or equal tobeta<90&DEG;.

K418与42CrMo异种金属的激光穿透焊接

实验研究了连续波Nd：YAG激光焊接速度、侧吹保护气流量和离焦量等参量对激光穿透焊接K418和42CrMo焊缝成形的影响。结果表明，K418与42CrMo激光穿透焊接有X形和T形两种典型的焊缝形貌，且焊缝形貌是不对称的。随着焊接速度的提高，焊接线能量降低，焊缝尺寸变小，且焊缝上部尺寸变化比下部尺寸变化慢，焊缝形貌由X形过渡到T形。当离焦量在瑞利长度范围内时，焊缝正面宽度变化很小；当离焦量超出瑞利长度范围时，在足够高的激光功率密度下，焊缝正面宽度快速增加。在激光功率为3kW，侧吹保护气角度为35°条件下，通过优化焊接速度、侧吹保护气流量和离焦量等参量可以得到最佳焊缝质量。

Thermal mismatch stress in SiC whisker reinforced aluminium composite: new measurement method by X-ray diffraction

A new X-ray diffraction method for characterising thermal mismatch stress (TMS) in SiC_w–Al composite has been developed. The TMS and thermal mismatch strain (TMSN) in SiC whiskers are considered to be axis symmetrical, and can be calculated by measuring the lattice distortion of the whiskers. Not only the average TMS in whiskers and matrix can be obtained, but the TMS components along longitudinal and radial directions in the SiC whiskers can also be deduced. Experimental results indicate that the TMS in SiC whiskers is compressive, and tensile in the aluminium matrix. The TMS and TMSN components along the longitudinal direction in the SiC whiskers are greater than those along the radial direction for a SiC_w–Al composite quenched at 500&deg;C.

Micro- and macro-tribological study on a self-assembled dual-layer film

A novel self-assembled dual-layer film as apotential excellent lubricant for micromachines was successfully prepared on single-crystal silicon substrate by chemical adsorption of stearic acid (STA) molecules on self-assembled monolayer of 3-aminopropyltri

Direct Numerical Simulation Of Hypersonic Boundary-Layer Transition Over A Blunt Cone

Direct numerical simulation of transition How over a blunt cone with a freestream Mach number of 6, Reynolds number of 10,000 based on the nose radius, and a 1-deg angle of attack is performed by using a seventh-order weighted essentially nonoscillatory scheme for the convection terms of the Navier-Stokes equations, together with an eighth-order central finite difference scheme for the viscous terms. The wall blow-and-suction perturbations, including random perturbation and multifrequency perturbation, are used to trigger the transition. The maximum amplitude of the wall-normal velocity disturbance is set to 1% of the freestream velocity. The obtained transition locations on the cone surface agree well with each other far both cases. Transition onset is located at about 500 times the nose radius in the leeward section and 750 times the nose radius in the windward section. The frequency spectrum of velocity and pressure fluctuations at different streamwise locations are analyzed and compared with the linear stability theory. The second-mode disturbance wave is deemed to be the dominating disturbance because the growth rate of the second mode is much higher than the first mode. The reason why transition in the leeward section occurs earlier than that in the windward section is analyzed. It is not because of higher local growth rate of disturbance waves in the leeward section, but because the growth start location of the dominating second-mode wave in the leeward section is much earlier than that in the windward section.

M_∞=1及其附近翼型绕流的计算结果

本文全速势方程的有限差分数值计算结果,给出了0&deg;和2&deg;攻角下NACA0012翼型当地马赫数分布冻结时的自由流马赫数范围,以及M_&infin;稍大于1变至1.30时前方脱体激波的变化位置。

Experimental studies on self-ignition of hydrogen/air supersonic combustion

Self-ignition tests of a model scramjet combustor were conducted by using parallel sonic injection of gaseous hydrogen from the base of a blade-like strut into a supersonic airstream, The vitiated air was produced by burning H-2, O-2, and air to a stagnation temperature of 1000-2100 K and a stagnation pressure of 0.8-1.6 MPa, The effects of different parameters on the self-ignition limits were analyzed, In addition, the effects of the combustor's different wall configurations on self-ignition limits were specifically studied. It was found that the wall configurations of the combustor had a significant effect on self-ignition limits, which might have variations of 420-840 K deg in stagnation temperature; however, the local static temperature in the recirculation zones for different wall configurations remained the same at approximately 1100 K, It was found that self-ignition could initiate at the exit of the combustor and this can be considered as a weak self-ignition characteristic.

Creep characterization of a fiber reinforced plastic material

Creep behavior of [±45&deg;]_s composite material is characterized by using uniaxial creep and recovery tests. The well-known Schapery nonlinear viscoelastic consti tutive relation was modified to make it suitable for characterizing the creep behavior of this material. Then, using this modified Schapery constitutive equation, by which the vis coplastic and creep damage can be taken into consideration, the creep behavior of [±45&deg;]. glass fiber reinforced epoxy laminate was studied. The constitutive parameters of the material were determined experimentally, and the procedure and method of determination of the material parameters are proved to be valid.

Creep behavior of woven roving grp beam in three-point bending

The creep and relaxation behaviour of laminated glass fibre reinforced plastics (GRP) in three-point bending were studied both experimentally and analytically. Creep and relaxation experiments were carried out on eight types of specimens, consisting of glass fibre fabric reinforced epoxy beams. While the bending deflexion and creep strains were measured in the creep tests, the load and relaxation strain were recorded in the relaxation tests. Marked creep effects were seen in the tests, where the environment temperature was 50&deg;C and the period of the measurement was 60 min. An attempt to predict the creep deflexion and relaxation behaviour was made. The transverse shear effect on creep deflexion was taken into account. The predicted results were compared with experimental ones. They were found to be in reasonable agreement, but the linearization assumption, upon which the relaxation behaviour analysis was based, appears to lead to larger inaccuracies in the results.

Thermophoretic deposition of particles in gas flowing over cold surfaces

Some of the calculated parameters show a maximum value for specimens heat-treated at about 100&deg;C. The tensile strength is, for instance, substantially higher for specimens shock-heated at 100&deg;C than for non-heated ones. Another striking feature is the initial decrease of the diameter observed in specimens heat-treated at 600&deg;C when loaded in uniaxial compression. Both optical microscopy and DSA experiments reveal a large increase in microcracking when the heat-treatment temperature exceeds 300&deg;C.