Atomic-scale dynamics of a two-dimensional gas-solid interface

The interface between a two-dimensional (2D) molecular gas and a 2D molecular solid has been imaged with a low-temperature, ultrahigh-vacuum scanning tunneling microscope. The solid consists of benzene molecules strongly bound to step edges on a Cu{111} surface. Benzene molecules on the Cu{111} terraces move freely as a 2D gas at 77 kelvin. Benzene molecules transiently occupy well-defined adsorption sites at the 1D edge of the 2D solid. Diffusion of molecules between these sites and exchange between the two phases at the interface are observed. On raised terraces of the copper surface, the 2D gas is held in a cage of the solid as in a 2D nanometer-scale gas bulb.     

Optical Studies of Pulsar NP 0532

The period of optical pulsations from NP 0532 has been determined to within 3 nanoseconds on three different nights. The time rate of change of the period (dP/dt)(p) was 36.17 x 10(-9) second per day. The pulse shape was highly asymmetrical with strong indications of structure. The ratio of the amplitude of the main pulse to that of the interpulse varied with time. No evidence was found for photon coincidences in the pulse on a time scale shorter than 2 microseconds.     

Multiple-step melting in two-dimensional hexatic liquid-crystal films

An unexpected three-stage melting transition has been observed in two-dimensional (2D) free-standing liquid-crystal films by in situ electron-diffraction and optical-reflectivity measurements. These data suggest the existence of two phases between the 2D solid and liquid: a hexatic phase and, at a higher temperature, an intermediate liquid phase with hexatic-like positional correlations ( approximately 40 angstroms) but no long-range orientational order. Previous high-resolution heat-capacity measurements have revealed a divergent-like anomaly at the hexatic-liquid transition that sharply contradicts the predictions of 2D melting theories. The observation of an intermediate isotropic phase may alter our understanding of 2D melting and lead to reconciliation between current experiments and theories.     

Structure of a Langmuir film on a liquid metal surface

The structure of organic monolayers on liquid surfaces depends sensitively on the details of the molecular interactions. The structure of a stearic acid film on a mercury surface was measured as a function of coverage with angstrom resolution. Unlike monolayers on water, the molecules were found here to undergo a transition from surface-parallel to surface-normal orientation with increasing coverage. At high coverage, two condensed hexatic phases of standing-up molecules were found. At low coverage, a two-dimensional (2D) gas phase and condensed single- and double-layered phases of flat-lying molecular dimers were revealed, exhibiting a 1D longitudinal positional order. This system should provide a broader tunability range for nanostructure construction than solid-supported self-assembled monolayers.     

Water on Mars: Clues from Deuterium/Hydrogen and Water Contents of Hydrous Phases in SNC Meteorites

Ion microprobe studies of hydrous amphibole, biotite, and apatite in shergottite-nakhlite-chassignite (SNC) meteorites, probable igneous rocks from Mars, indicate high deuterium/hydrogen (D/H) ratios relative to terrestrial values. The amphiboles contain roughly one-tentn as much water as expected, suggesting that SNC magmas were less hydrous than previously proposed. The high but variable D/H values of these minerals are best explained by postcrystallization D enrichment of initially D-poor phases by martian crustal fluids with near atmospheric D/H (about five times the terrestrial value). These igneous phases do not directly reflect the D/H ratios of martian "magmatic" water but provide evidence for a D-enriched martian crustal water reservoir.     

X-ray Pulsar in the Crab Nebula

X-ray pulsations have been observed in the Crab Nebula at a frequency closely matching the radio and optical pulsations. About 5 percent of the total x-ray power of the nebula appears in the pulsed component. The x-ray pulsations have the form of a main pulse and an interpulse separated by about 12 milliseconds.     

Temporal summation and refractoriness in hypothalamic reward neurons as measured by self-stimulation behavior

A neurophysiological technique of double-pulse stimulation has been applied to freely moving rats with chronic indwelling electrodes in the hypothalamic reward area. Self-stimulation thresholds, measured as a function of the interpulse interval, generated curves with time constants characteristic of refractory periods and temporal synaptic summation. The results indicate a way of studying central neuronal processes for which the overt behavior of the animal is the dependent variable.     

Carbon-free fullerenes: condensed and stuffed anionic examples in indium systems

Condensed, well-ordered analogs of the fullerenes occur in the hexagonal phases Na(96)In(97)Z(2) (Z = nickel, palladium, or platinum). Large cages of In(74) (D3h) and M(60) (= In(48)Na(12), D3d) share pentagonal faces to generate a double-hexagonal close-packed analog of NiAs. All these polyhedra are centered by partially disordered In(10)Z clusters within deltahedra of sodium atoms that cap all inner faces of the cages, namely, Z@In(10)@Na(39)@In(74) and Z@In(10)@Na(32)@Na(12)In(48) "onions" The highest filled bands in these compounds apparently involve localized electron pairs on surface features on In(74)-based layers. Structural and electronic relations between diamond and Naln (stuffed diamond structure) parallel those between certain fullerenes and Na(96)In(97)Z(2) and, presumably, other valence-driven intermetallic phases.     

Temporal pattern as a cue for species-specific calling song recognition in crickets

Female crickets can recognize conspecific calling song from its temporal pattern alone. In Teleogryllus oceanicus, the song pattern consists of three classes of interpulse intervals arranged in a stereotyped sequence. Females recognize a model song in which the sequential order of intervals is random. This argues against the hypothesis that recognition results from matching auditory input to an internal template of the song.     

三种石斛与大叶落地生根光合作用比较研究

石斛属为兰科大属,部分物种光合作用行景天酸代谢途径。为了检验石斛的光合作用碳代谢途径,试验选用典型的专性景天酸代谢植物大叶落地生根为对照。光合作用测定结果表明,报春石斛的光饱和点为700μmolphoton.m-2s-1,最大表观光合作用速率达3.826μmol.CO2m-2.s-1,光合作用日变化呈现出景天酸代谢植物的四阶段特征;鼓槌石斛的光饱和点为900μmolphoton.m-2.s-1,最大光合作用速率高达5.912μmolCO2.m-2.s-1,光合作用日变化呈单峰曲线,最大值出现在中午前后,不具备景天酸代谢植物特征;金钗石斛表现为更适合荫蔽环境,光合作用日变化呈双峰曲线,中午光照最强烈的时段表观光合作用速率出现一定程度降低。     

Molecular transfer of a species-specific behavior from Drosophila simulans to Drosophila melanogaster

Drosophila males modulate the interpulse intervals produced during their courtship songs. These song cycles, which are altered by mutations in the clock gene period, exhibit a species-specific variation that facilitates mating. We have used chimeric period gene constructs from Drosophila melanogaster and Drosophila simulans in germline transformation experiments to map the genetic control of their song rhythm difference to a small segment of the amino acid encoding information within this gene.     

C3D测深侧扫声呐系统在人工鱼礁建设中的应用

长期以来将多波束测深数据和侧扫声呐图像进行融合叠加,一直是水下测绘领域的研究难题,而美国Benthos公司近年推出的C3D测深侧扫声呐系统,采用了多阵列换能器,CAATI专利算法,可同步获得高分辨率的侧扫图像和高质量的测深数据。本文着重研究:(1)在鱼礁区的设计阶段,C3D系统提供三维的水下地形、等深线等数据,进行三维可视化的鱼礁礁址的选择和布设方案设计;提供高分辨率的水下地貌图像,进行海底地质的分类,也可直观判断水下的各种地貌和障碍物等。(2)在鱼礁施工阶段,利用C3D水下图像对鱼礁的位置和状态进行评估,改进投放方法和工艺,确保设计方案的实施到位。(3)在鱼礁竣工后的监测阶段,利用不同时期的C3D高分辨率图像及水深数据进行比对,以判断鱼礁区的地形地貌变化,鱼礁的稳定性、掩埋损坏等情况。实验表明,C3D是一款性能优越的水下声呐探测系统,可为人工鱼礁方案设计提供详细的海底地形和底质信息,可对人工鱼礁建设的过程和结果进行科学的评估,将为各地人工鱼礁工程的顺利实施和效果保障发挥重要作用。     

Control of colonial hydroid macrofouling by free-field ultrasonic radiation

Free-field ultrasonic radiation inhibited the feeding of the macrofouling hydroid Garveia franciscana by causing tentacle contraction at the sonic degasification threshold. Within the frequency range of 250 to 2000 kilohertz, the threshold sound intensity (sonic degasification threshold) that caused tentacle contraction was directly proportional to frequency, with the minimum observed being 0.6 watt per square centimeter at 250 kilohertz. A pulse length of 0.2 second and interpulse period of 102 seconds gave the lowest average power required to produce tentacle contraction at a peak pulse sound intensity of 6.2 watts per square centimeter with a frequency of 250 kilohertz. Twenty-four hour exposures to the sound regime caused destruction of the hydranths and regression of tissue in the stolons.     

PCA对固液反应球磨过程的影响

研究HCl,NaCl,KCl,Na2SO4和硬脂酸等工艺过程控制剂(PCA)对Ni-Al固液反应球磨过程、粉末产量和粉末纯度的影响.采用D5000型X射线衍射仪进行球磨产物的物相分析,JSM-6700F型冷场发射扫描电镜观察球磨产物的显微组织.结果表明:球磨反应过程中,PCA在一定程度上促进了球磨反应的进行,提高了球磨产物的产量,粉末的团聚现象减弱,且PCA对球磨产物的污染很小.此外,分析讨论了PCA在固液反应球磨过程中的防粘机理.     

Amorphous solid water: a neutron diffraction study

The structure factor of amorphous solid D(2)O deposited from the vapor at 10 degrees K has been obtained by measuring the neutron diffraction spectrum in the wave vector transfer from 0.8 to 12.3 reciprocal angstroms. The results indicate that the phase investigated is amorphous and has a liquiid-like structure factor. The Fourier-transformed structure e factor yields a real space pair distribution function consistent with local tetrahedral coordination and hydrogen bonding, as in other condensed phases of water. The intramolecular OD separation is 1.00 angstrom; the lack of data for very large wave vector transfer and the expected near equality of the intramolecular DD separation and intermolecular O . . . D separation make it impossible to determine the intramolecular DOD angle with precision. The neutron scattering data presented are complementary to the x-ray diffraction studies of Venkatesh, Rice, antd Narten.     

刺楸组培快繁及试管苗保存培养基的筛选

    以刺楸嫩叶柄为外植体,应用均匀设计法筛选最适合的培养基.结果表明,刺楸组织培养的不同阶段需要不同的培养基.最适的愈伤组织诱导培养基为C2D+6-BA(6-苄氨基腺嘌呤) 0.50 mg·L-1+NAA(萘乙酸)1.00 mg·L-1;愈伤组织增殖培养基为C2D+6-BA 0.50 mg·L-1+NAA 0.50～1.00 mg·L-1;愈伤组织诱导再分化培养基为C2D+6-BA 2.50 mg·L-1+KT(激动素) 4.50 mg·L-1+NAA 0.10 mg·L-1;生根培养基为1/2 MS + IBA(吲哚丁酸) 0.10 mg·L-1+IAA(吲哚乙酸) 0.10 mg·L-1;试管苗保存培养基为1/5 MS+ABA(脱落酸) 2.50 mg·L-1.常温条件下,利用低营养促成休眠的方法在试管内保存刺楸种质可达44个月.     

A behavioral measure of homosynaptic and heterosynaptic temporal summation in the self-stimulation system of rats

Bilateral stimulation of the medial forebrain bundle with pulses of varying interpulse intervals elicited a pattern of self-stimulation behavior in the rat indicative of temporal synaptic summation: the shorter the interval the greater the response. In contrast, the effectiveness of unilateral stimulation at very short intervals was limited by neuronal refractory periods. The results support the notion that there is convergence of the medial forebrain bundle self-stimulation system from the two sides of the brain and suggest ways of studying the degree of convergence. They also suggest a technique for behaviorally comparing heterosynaptic and homosynaptic mechanisms of summation.     

三叶香茶菜的植物形态、生态环境和生物学特性观察

介绍了三叶香茶菜的植物形态、野生分布、生态环境、物候期、茎叶特性、开花结果习性、抗旱和耐涝性等,为人工栽培三叶香茶菜提供参考。     

褐菖鲉发声系统形态结构及其发声特征研究

分别采用形态学和模拟领地入侵的方法研究了褐菖鲉发声系统和发声特征。结果表明,褐菖鲉发声系统由鱼鳔肌和鱼鳔组成。鱼鳔肌前方附着于颅骨的翼耳骨,后经第1～7肋骨,与鱼鳔背后侧部相连。在领地入侵模拟实验中,褐菖鲉发出了连续脉冲的“咕噜噜”声音,其平均脉冲周期为(32.6±2.6) ms,平均脉冲间隔为(51.8±81.4) ms, 主频为68～175 Hz。对单个声音脉冲中包涵的正弦波型的能量周期分析发现：其声音主频与最大能量周期的倒数一致,表明褐菖鲉是采用鱼鳔肌收缩的发声机制。     

不同龄期菜蚜茧蜂对蚜虫宽缘金小蜂发育的影响

田间收集蚜虫宽缘金小蜂Pachyneuron aphidis(Bouche),采用室内饲养的方法,研究了不同龄期菜蚜茧蜂Diaeretella rapae M’Intosh对蚜虫宽缘金小蜂发育的影响,蚜虫宽缘金小蜂寄生菜蚜茧蜂的蛹,是体外寄生蜂,其对处于预蛹期前的菜蚜茧蜂不会有寄生行为．随着菜蚜茧蜂蛹龄的增加,蚜虫宽缘金小蜂的发育历期由15．22d逐渐缩短为12．21d,重寄生率也由15％逐渐降低为3％,蚜虫宽缘金小蜂的个体发育可分为卵、工龄幼虫、Ⅱ龄幼虫、Ⅲ龄幼虫、预蛹、蛹等6个阶段,文中对各发育阶段作了详细描述,并附有相应的图片。