Rotation of mercury: theoretical analysis of the dynamics of a rigid ellipsoidal planet

The second-order nonlinear differential equation for the rotation of Mercury implies locked-in motion when the period is within the range where e is the eccentricity and T is the period of Mercury's orbit, the time t is measured from perihelion, and lambda is a measure of the planet's disiortion. For values near 2T/3, the instantaneous period oscillates about 2T/3 with period (21lambdae/2)T.     

新生入学阶段实施成才观念教育的探析

在进行大学新生成才障碍的心理因素分析的基础上, 归纳大学新生入学后易出现的各类问题, 并结合学校新生入学教育方案, 指出新生入学阶段帮助其克服成才心理障碍的教育对策, 提出了相应的健康成长成才的教育、引导途径。以求使大学新生在思想、学习、生活等各方面顺利度过从心理不适、职业迷茫到健康成才的适应期, 踏上新的人生征程。     

Climate-related, long-term faunal changes in a california rocky intertidal community

Changes in the invertebrate fauna of a California rocky intertidal community between the period 1931 to 1933 and the period 1993 to 1994 indicate that species' ranges shifted northward, consistent with predictions of change associated with climate warming. Of 45 invertebrate species, the abundances of eight of nine southern species increased and the abundances of five of eight northern species decreased. No trend was evident for cosmopolitan species. Annual mean shoreline ocean temperatures at the site increased by 0.75 degrees C during the past 60 years, and mean summer maximum temperatures from 1983 to 1993 were 2.2 degrees C warmer than for the period 1921 to 1931.     

Discrimination of successiveness: a test of a model of attention

Interpreting attention as a periodic phenomenon, we show its relevance to discriminating the successiveness of signals presented to separate sense modalities. Experiments confirm the expected linear relation between the probability of discriminating pairs of successive from pairs of simultaneous signals and make it possible to infer the period of attention.     

Evidence for a past high-eccentricity lunar orbit

The large differences between the Moon's three principal moments of inertia have been a mystery since Laplace considered them in 1799. Here we present calculations that show how past high-eccentricity orbits can account for the moment differences, represented by the low-order lunar gravity field and libration parameters. One of our solutions is that the Moon may have once been in a 3:2 resonance of orbit period to spin period, similar to Mercury's present state. The possibility of past high-eccentricity orbits suggests a rich dynamical history and may influence our understanding of the early thermal evolution of the Moon.     

一次暴雨过程的非平衡振动与诊断分析

采用诊断分析方法,对2010年7月15-18日四川盆地的暴雨天气过程进行分析。结果表明,在暴雨的强盛阶段和持续阶段,盆地内的上升气流均非常强盛,达300 hPa以上;在暴雨强盛阶段,气流的辐合层并不十分深厚,气流的辐合运动在500 hPa以下;此次过程中对流层低层的正涡度大值中心与暴雨区对应的相对较好,气流辐合辐散强度较旋转强度大一个量级,散度在系统变化过程中起主导作用;在暴雨强盛阶段,对流层低层非平衡值U〈0,较强的非平衡振动有利地激发辐合运动发展,对流层上层非平衡值U〉0,激发高层辐散运动发展,高层辐散带动低层辐合,形成强烈的上升运动。     

Sedimentary rock types: relative proportions as a function of geological time

Proportions of sedimentary rock types remaining today differ from period to period. These differences may be chiefly the result of differential rates of deposition and erosion of the various components of the rocks. Lower percentages of limestones and evaporites in Precambrian rocks than in post-Precambrian rocks probably represent selective loss of these more easily removable components from the original deposits.     

Refractoriness in female lizard reproduction: a probable circannual clock

Postreproductive Cnemidophorus uniparens maintained under free-running conditions of constant darkness for 7 months became reproductive at the same time as controls exposed to a long photoperiod. This lizard exhibits a pause in reproductive activity (refractory period) commencing in late summer in nature and terminating in mid-December in captivity. Both groups terminated refractoriness and started reproducing simultaneously in December despite maintenance of the experimental group in darkness since September. These results confirm the hypothesis that the refractory period in this lizard is under endogenous control.     

华北粗砂土免耕桃园生态尺度水分利用效率研究

为了给制定果园精准灌溉管理方案提供理论依据,采用涡度相关技术,监测并探讨粗砂土立地条件下12年树龄自然生草免耕桃园生态尺度水分耗散及水分利用效率的动态变化。结果表明,桃园全年监测期内,日平均蒸散耗水量和水分利用效率分别为(2.2±2.1) mm和0.44 g/kg,饱和水汽压差是影响桃树旺盛生长季日水分利用效率的关键因子,群体水平日平均水分利用效率由高到低的顺序为：果实收获后＞果实成熟期与果实膨大后期＞果实膨大初期与开花期;季节变化过程中,蒸散耗水量和水分利用效率均呈单峰型变化趋势,在果实膨大后期至成熟期蒸散耗水量较多,且日最高蒸散量达到7.1 mm,日平均水分利用效率则在果实收获后达到高峰,日平均水分利用效率最高为2.1 g/kg;全年累积蒸散耗水量为790.6 mm,平均作物系数(Kc=1.08)高于FAO(1998)推荐值达27%。果实膨大后期-成熟期是桃树水分耗散高峰期,采取精准灌溉等措施进行果园水分科学管理是提高果树水分利用效率的关键。     

Wake collapse in a stratified fluid

A two-dimensional model is used to obtain quantitative data on characteristics of turbulently mixed wakes of bodies submerged in stratified fluids (more dense below than above). The time between turbulent mixing and maximum expansion of the wake before vertical collapse starts is 0.44 T, where T is the local V?is?l?-Brunt period. Time after mixing for maximum rate of horizontal spreading is about 2.0 T. The average V?is?l?-Brunt period for the oceans and atmosphere is discussed. It is predicted that the wake collapse phenomenon is not unusual in these environments. The characteristic time for the most active phase of vertical wake collapse should be between a few minutes to several tens of minutes. Qualitative observations of aircraft vapor trails tend to confirm that the phenomenon does occur at full scale.     

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.     

An algorithm for temperature compensation in a heated greenhouse

A temperature compensation algorithm modifies the greenhouse heating setpoint depending on temperatures previously achieved. The algorithm increases the setpoint following a period when the heating is insufficient to achieve the blueprint temperature, and may also reduce the setpoint following a period of temperatures above the blueprint. The time constant used to calculate the average departure from the blueprint is long (1–10 days). Maximum compensation is obtained with a 10-day time constant. The correction applied to the blueprint varies very slowly and does not affect the rate of temperature change demanded during the dawn, evening, or dusk change over periods.     

山西农家乐旅游发展初探

山西省农家乐旅游的发展速度异常迅猛,但由于前期缺乏规划,农村基础设施配套和农民自身综合素质等原因,我国农家乐还处于探索起步阶段。     

Geothermal evidence from Canada for a cold period before recent climatic warming

Three deep boreholes in a small area in Quebec, each having two high-accuracy temperature logs separated by 22 years, allow reliable determination of the ground surface temperature history during the past few centuries. The temperature logs show that the recent climatic warming was preceded by a cold period near the end of the 19th century in this area. The presence of such a cold period is also suggested by borehole temperature data from other areas in Canada.     

无花粉型水稻温敏核不育系籼S的生育特性研究

在广州市人控光温条件下的研究表明,籼S在广州(23°08'N)自然条件下,正常的播始历期最长104 d,最短为71 d,籼S播始历期的变化受温度的影响较大,籼S具有明显的感光性,光长对播始历期的影响有所不同,第一光周期的光长对播始历期的影响较第二光周期要大;以籼S为母本杂交F1的播始历期绝大多数比籼S短,且与父本更接近.     

Efficiency of a siphon drainage system under conditions in a low gradient area

The drainage system designs and their function principles at the experimental production plot for the siphon- and vacuum-assisted drainage in the Mugan-Salyan massif characterized by the nongradient area have been described. The surveys are carried out in the natural environments during the vegetation period for the irrigation of cotton occupying the entire area of the experimental plot. A high efficiency of the siphonand vacuum-assisted drainage system has been calculated. In addition, the drain discharge and the discharge module are closely connected to the existing water pressure value in the interdrain. In the vegetation period, the maximum and minimum water discharges comprised 11.1 L/sec and 2.8 L/sec, respectively. The drainage module value varied from 0.14 to 0.55 L/sec hectare. It has been ascertained that the drainage system operation provides the opportunity to lower the depth of the groundwater table within the interdrain up to 250–280 cm (the initial depth is 120–150 cm). The possibilities of significant increases in the flushing intensity and the reduction of the terms of the regulated ameliorative activities within the certain hydrogeological regime have been proven.     

Ordered phosphorylation governs oscillation of a three-protein circadian clock

The simple circadian oscillator found in cyanobacteria can be reconstituted in vitro using three proteins-KaiA, KaiB, and KaiC. The total phosphorylation level of KaiC oscillates with a circadian period, but the mechanism underlying its sustained oscillation remains unclear. We have shown that four forms of KaiC differing in their phosphorylation state appear in an ordered pattern arising from the intrinsic autokinase and autophosphatase rates of KaiC and their modulation by KaiA. Kinetic and biochemical data indicate that one of these phosphoforms inhibits the activity of KaiA through interaction with KaiB, providing the crucial feedback that sustains oscillation. A mathematical model constrained by experimental data quantitatively reproduces the circadian period and the distinctive dynamics of the four phosphoforms.     

菜用大豆品种毛豆292鼓粒与需水特点

通过3种灌水处理研究了菜用大豆品种毛豆292的鼓粒和需水特点.结果表明,在干旱条件下始花期和鼓粒初期各灌水1次,能明显加快籽粒鼓粒速度,延长鼓粒持续期,促进籽粒饱满,增加标准荚数,提高鲜荚产量和标准荚产量.     

湘西瓜14号新品种的选育

为选育西瓜良种 ,以新 80 45 2为母本 ,以日本引进的杂交一代品种、经多代自交分离而成的高世代自交系HF为父本进行杂交 ,于 1997年育成中熟、优质、多抗无籽西瓜新品种湘西瓜 14号 .该新品种全生育期 92 d左右 ,果实发育期 30～ 32 d,果皮绿色 ,覆有深绿色纹条带 ,果实高圆形 ,外形美观 ,果肉鲜红一致 ,肉质细嫩爽脆 ,汁多味甜 ,口感风味好 .中心可溶性固形物含量 12 %以上 ,边糖 10 % ;平均单瓜重 5～ 6 kg,产量可达 5 .2 5× 10 4kg/ hm2 .抗西瓜炭疽病和疫病     

生物制剂激活蛋白在烤烟生产上的应用研究

为探索防治烟草花叶病和提高烟叶产质量新方法,以激活蛋白为材料,开展生物制剂在烤烟生产上的应用研究。结果表明:在烤烟不同生育期喷施激活蛋白能有效促进烟株生长,抑制烟叶花叶病发生,提高烟叶经济性状和改善烟叶品质。其中以苗床期、移栽期和团棵期3个时期都喷施激活蛋白的处理效果最优。