地下水位对胡杨(Populus euphratica)和灰胡杨(Populus pruinosa)叶绿素荧光光响应与光合色素含量的影响

在塔里木河上游利用便携式调制叶绿素荧光仪研究了地下水位对胡杨(Populus pruinosa)和灰胡杨(Populus pruinosa)光合色素和叶绿素荧光光响应的影响.结果表明:不同地下水位环境下,2树种表观光合电子传递速率(ETR)、非光化学猝灭系数(NPQ)、PSⅡ激发能压力(1-qP)、天线色素热耗散能量(D)、非光化学反应耗散能量(E)、光合功能相对限制值(PED)和光系统间激发能分配不平衡偏离系数(β/α-1)随光合有效辐射(PAR)增加而升高,PSⅡ实际光化学效率(ΦPSⅡ)、光化学猝灭系数(qP)和光化学反应能量(P)则随PAR增加而降低;相同光强下,地下水位下降导致胡杨和灰胡杨叶片含水量、最大电子传递速率(ETRmx)、光化学反应启动速率(θ)、ETR、ΦPSⅡ、qP、P与叶绿素(Chla、Chlb、Chl(a+b))和类胡萝卜素(Car)含量降低,而使Chla/b、NPQ、D、E、PED、1-qP、β/α-1明显升高;地下水位下降显著影响2树种叶绿素荧光光响应参数,引起光能吸收、传递与分配改变,致使光合效率降低;地下水位下降对灰胡杨光合生理过程的影响程度明显高于胡杨,表明胡杨对荒漠逆境的适应性强于灰胡杨.逆境下胡杨通过维持相对较高的ETR、ETRmax、θ、ΦPSⅡ、qP、P值,并通过增强非辐射性热耗散来调节自身能量代谢,以此来保护光合机构正常运转,这是胡杨长期适应干旱荒漠逆境而形成的一种自我调节机制.     

Effects of blue light on gametophyte development of Laminaria japonica （Laminariales, Phaeophyta）

1 INTRODUCTION Light acts as an important ambient factor to regulate plant growth. Several critical points in life history for many marine algae are controlled by light. Photobiology of algae has been a discipline of particular interest for a long time (Dring, 1988). Many light effects on algae are photoperi- odic-regulated, such as sporangia formation in red algae Porphyra tenera (Rentschler, 1967) and As- paragopsis armata (Oza, 1976), and erect thalli de- velopment in brown algae Scy…     

Analysis of Extra-Solar Planetary Transits Using Tools from Eclipsing Binaries

Analytical formulae for the computation of the photometric elements of extra-solar planetary transits are presented. They were initially derived for the study of well-detached eclipsing binaries and are valid for any degree of limb darkening and type of transit as well as for eccentric orbits. The only assumption is that the projections of the star and the planet on the plane of the sky are well represented by circular discs. The procedure to get valid ranges for the involved parameters, as well as to make precise estimations of initial parameters, using the analytical nature of the equations is given together with some discussion on their practical application. Examples are shown for OGLE-TR-113, representative of a light curve obtained with ground-based telescopes, and HD 209458 with a precise light curve obtained with the Hubble Space Telescope.     

Physical properties of asteroid dust bands and their sources

Disruptive collisions in the main belt can liberate fragments from parent bodies ranging in size from several micrometers to tens of kilometers in diameter. These debris bodies group at initially similar orbital locations. Most asteroid-sized fragments remain at these locations and are presently observed as asteroid families. Small debris particles are quickly removed by Poynting-Robertson drag or comminution but their populations are replenished in the source locations by collisional cascade. Observations from the Infrared Astronomical Satellite (IRAS) showed that particles from particular families have thermal radiation signatures that appear as band pairs of infrared emission at roughly constant latitudes both above and below the Solar System plane. Here we apply a new physical model capable of linking the IRAS dust bands to families with characteristic inclinations. We use our results to constrain the physical properties of IRAS dust bands and their source families. Our results indicate that two prominent IRAS bands at inclinations ≈2.1° and ≈9.3° are byproducts of recent asteroid disruption events. The former is associated with a disruption of a ≈30-km asteroid occurring 5.8 Myr ago; this event gave birth to the Karin family. The latter came from the breakup of a large >100-km-diameter asteroid 8.3 Myr ago that produced the Veritas family. Using an N-body code, we tracked the dynamical evolution of ≈10⁶ particles, 1 μm to 1 cm in diameter, from both families. We then used these results in a Monte Carlo code to determine how small particles from each population undergo collisional evolution. By computing the thermal emission of particles, we were able to compare our results with IRAS observations. Our best-fit model results suggest the Karin and Veritas family particles contribute by 5-9% in 10-60-μm wavelengths to the zodiacal cloud's brightness within 50° latitudes around the ecliptic, and by 9-15% within 10° latitudes. The high brightness of the zodiacal cloud at large latitudes suggests that it is mainly produced by particles with higher inclinations than what would be expected for asteroidal particles produced by sources in the main belt. From these results, we infer that asteroidal dust represents a smaller fraction of the zodiacal cloud than previously thought. We estimate that the total mass accreted by the Earth in Karin and Veritas particles with diameters 20-400 μm is ≈15,000-20,000 tons per year (assuming 2 g cm⁻³ particles density). This is ≈30-50% of the terrestrial accretion rate of cosmic material measured by the Long Duration Exposure Facility. We hypothesize that up to ≈50% of our collected interplanetary dust particles and micrometeorites may be made up of particle species from the Veritas and Karin families. The Karin family IDPs should be about as abundant as Veritas family IDPs though this ratio may change if the contribution of third, near-ecliptic source is significant. Other sources of dust and/or large impact speeds must be invoked to explain the remaining ≈50-70%. The disproportional contribution of Karin/Veritas particles to the zodiacal cloud (only 5-9%) and to the terrestrial accretion rate (30-50%) suggests that the effects of gravitational focusing by the Earth enhance the accretion rate of Karin/Veritas particles relative to those in the background zodiacal cloud. From this result and from the latitudinal brightness of the zodiacal cloud, we infer that the zodiacal cloud emission may be dominated by high-speed cometary particles, while the terrestrial impactor flux contains a major contribution from asteroidal sources. Collisions and Poynting-Robertson drift produce the size-frequency distribution (SFD) of Karin and Veritas particles that becomes increasingly steeper closer to the Sun. At 1 AU, the SFD is relatively shallow for small particle diameters D (differential slope exponent of particles with D?100 μm is ≈2.2-2.5) and steep for D?100 μm. Most of the mass at 1 AU, as well as most of the cross-sectional area, is contributed by particles with D≈100-200 μm. Similar result has been found previously for the SFD of the zodiacal cloud particles at 1 AU. The fact that the SFD of Karin/Veritas particles is similar to that of the zodiacal cloud suggests that similar processes shaped these particle populations. We estimate that there are ≈5×¹⁰²⁴ Karin and ≈10²⁵ Veritas family particles with D>30 μm in the Solar System today. The IRAS observation of the dust bands may be satisfactorily modeled using ‘averaged’ SFDs that are constant with semimajor axis. These SFDs are best described by a broken power-law function with differential power index α≈2.1-2.4 for D?100 μm and by α?3.5 for 100 μm?D?1 cm. The total cross-sectional surface area of Veritas particles is a factor of ≈2 larger than the surface area of the particles producing the inner dust bands. The total volumes in Karin and Veritas family particles with 1 μm<D<1 cm correspond to D=11 km and D=14 km asteroids with equivalent masses ≈1.5×¹⁰¹⁸ g and ≈3.0×¹⁰¹⁸ g, respectively (assuming 2 g cm⁻³ bulk density). If the size-frequency and radial distribution of particles in the zodiacal cloud were similar to those in the asteroid dust bands, we estimate that the zodiacal cloud represents ∼3×¹⁰¹⁹ g of material (in particles with 1 μm<D<1 cm) at ±10° around the ecliptic and perhaps as much as ∼¹⁰²⁰ g in total. The later number corresponds to about a 23-km-radius sphere with 2 g cm⁻³ density.     

Modelling artificial night-sky brightness with a polarized multiple scattering radiative transfer computer code

As part of an ongoing investigation of radiative effects produced by hazy atmospheres, computational procedures have been developed for use in determining the brightening of the night sky as a result of urban illumination. The downwardly and upwardly directed radiances of multiply scattered light from an offending metropolitan source are computed by a straightforward Gauss–Seidel (G–S) iterative technique applied directly to the integrated form of Chandrasekhar's vectorized radiative transfer equation. Initial benchmark night-sky brightness tests of the present G–S model using fully consistent optical emission and extinction input parameters yield very encouraging results when compared with the double scattering treatment of Garstang, the only full-fledged previously available model.     

二阶后牛顿光线方程

近来相继提出一系列的空间天体测量计划，要求考虑在多参考系中二阶后牛顿部分对光线传播的贡献，也就是说，必须讨论在最近完成的扩展的DSX体系下的二阶后牛顿(2PN)光线方程．DSX体系是在20世纪90年代初建立的，用来讨论对N个任意形状和组成、自转可变形物体的一套完整的一阶后牛顿(1PN)天体力学理论．在此建议采用迭代的方法来推导2PN光线方程．从度规和Christoffel记号出发推导太阳系中的2PN光线方程．当忽略掉更高阶的项时，2PN光线方程将回到在很多教科书中广泛出现的1PN光线方程．利用这套方程就可以计算太阳系的光线传播．     

Study of light signal receptor of Stephanopyxis palmeriana during sexual reproduction

We collected centric diatom Stephanopyxis palmeriana samples in coastal waters of Xiamen for characteristic red light/far red light (R/FR) phytochrome reactions to identify its photoreceptor in the course of sexual reproduction. The result showed that pre-illumination of 2-3h red light before darkness could induce sexualization of S.palmeriana, while the follow-up illumination of far red light could reverse the effect of red light, which is a featured reaction of phytochrome. The Southern Dot Blot was carried out to identify the type of phytochrome that induces the sexualization. The result also showed high homogeneity of DNA fragment of S. palmeriana with phyB, but phyA. This means the photoreceptor in the process of sexual reproduction of S. palmeriana is phytochrome B (phyB).     

Study of light signal receptor of Stephanopyxis palmeriana during sexual reproduction

We collected centric diatomStephanopyxis palmeriana samples in coastal waters of Xiamen for characteristic red light/far red light (R/FR) phytochrome reactions to identify its photoreceptor in the course of sexual reproduction. The result showed that pre-illumination of 2–3h red light before darkness could induce sexualization ofS. palmeriana, while the follow-up illumination of far red light could reverse the effect of red light, which is a featured reaction of phytochrome. The Southern Dot Blot was carried out to identify the type of phytochrome that induces the sexualization. The result also showed high homogeneity of DNA fragment ofS. palmeriana with phyB, but phyA. This means the photoreceptor in the process of sexual reproduction ofS. palmeriana is phytochrome B (phyB). Supported by National Natural Science Foundation of China (No. 39670076)     

多目标光纤光谱处理方法的研究

以俄罗斯SAO 6米望远镜的多目标光纤光谱（multi-object-fiber-spectra）为例，介绍了多目标光纤光谱的观测方法和数据处理的一般过程，分析了影响精度的主要误差来源，根据所用软件和仪器的情况，对散射光，相对透过率，波长定标，流量定标等问题作了相应的讨论和适当改性。     

5种波长光对日本沼虾人工育苗幼体成活率的影响

光照与日本沼虾繁殖和孵化关系极为密切。研究了不同波长的光对日本沼虾孵化的影响 ,结果表明 :在环境光谱主峰值 4 70 .5nm、4 77.9nm、4 92 .6nm、5 0 4 .8nm和 6 15 .2nm条件下 ,适度成熟的亲虾都能顺利孵化 ,日本沼虾孵化与否 ,与孵化环境中的光波波长无关 ,而与抱卵日本沼虾胚胎发育有关。日本沼虾在孵化期对不同波长的光谱有明显的视觉敏感度分布 ,在前 4种光谱条件下 ,日本沼虾视觉器官敏感 ,而在光谱主峰值 6 15 .2nm时日本沼虾视觉器官不敏感。这一特点在日本沼虾育苗生产上具指导意义 ,可防止抱卵亲虾在孵化过程中吞食幼体 ,提高幼体成活率