Kinematical modeling of the Earth rotation,focusing on the Oppolzer terms in a rigid Earth and the Oppolzer-like terms in an elastic Earth

Under perturbations from outer bodies, the Earth experiences changes of its angular momentum axis, figure axis and rotational axis. In the theory of the rigid Earth, in addition to the precession and nutation of the angular momentum axis given by the Poisson terms, both the figure axis and the rotational axis suffer forced deviation from the angular momentum axis. This deviation is expressed by the so-called Oppolzer terms describing separation of the averaged figure axis, called CIP (Celestial Intermediate Pole) or CEP (Celestial Ephemeris Pole), and the mathematically defined rotational axis, from the angular momentum axis. The CIP is the rotational axis in a frame subject to both precession and nutation, while the mathematical rotational axis is that in the inertial (non-rotating) frame. We investigate, kinematically, the origin of the separation between these two axes—both for the rigid Earth and an elastic Earth. In the case of an elastic Earth perturbed by the same outer bodies, there appear further deviations of the figure and rotational axes from the angular momentum axis. These deviations, though similar to the Oppolzer terms in the rigid Earth, are produced by quite a different physical mechanism. Analysing this mechanism, we derive an expression for the Oppolzer-like terms in an elastic Earth. From this expression we demonstrate that, under a certain approximation (in neglect of the motion of the perturbing outer bodies), the sum of the direct and convective perturbations of the spin axis coincides with the direct perturbation of the figure axis. This equality, which is approximate, gets violated when the motion of the outer bodies is taken into account.     

Symmetric horseshoe periodic orbits in the general planar three-body problem

We present some families of horseshoe periodic orbits in the general planar three-body problem for the case of two equal masses. The considered system is a symmetric version of the one formed by Saturn, Janus and Epimetheus. We use a mass ratio equal to 35×10⁻⁵, corresponding to 10⁵ times the Saturn-Janus mass parameter of the restricted case; for this mass ratio the satellites have a significantly bigger influence on the planet than in the classical Saturn, Janus and Epimetheus system. To obtain periodic orbits, we search those horseshoe orbits passing through two reversible configurations. A particular kind of periodic orbits where the minor bodies follow the same path is discussed.     

Solar Magnetic Carpet I: Simulation of Synthetic Magnetograms

This paper describes a new 2D model for the photospheric evolution of the magnetic carpet. It is the first in a series of papers working towards constructing a realistic 3D non-potential model for the interaction of small-scale solar magnetic fields. In the model, the basic evolution of the magnetic elements is governed by a supergranular flow profile. In addition, magnetic elements may evolve through the processes of emergence, cancellation, coalescence and fragmentation. Model parameters for the emergence of bipoles are based upon the results of observational studies. Using this model, several simulations are considered, where the range of flux with which bipoles may emerge is varied. In all cases the model quickly reaches a steady state where the rates of emergence and cancellation balance. Analysis of the resulting magnetic field shows that we reproduce observed quantities such as the flux distribution, mean field, cancellation rates, photospheric recycle time and a magnetic network. As expected, the simulation matches observations more closely when a larger, and consequently more realistic, range of emerging flux values is allowed (4×10¹⁶ – 10¹⁹ Mx). The model best reproduces the current observed properties of the magnetic carpet when we take the minimum absolute flux for emerging bipoles to be 4×10¹⁶ Mx. In future, this 2D model will be used as an evolving photospheric boundary condition for 3D non-potential modeling.     

Strong shock-phenomena at petawatt-picosecond laser side-on ignition fusion of uncompressed hydrogen-boron11

An extreme anomaly of laser-plasma interaction with petawatt-picosecond (PW-ps) pulses of very high contrast ratio for suppression of relativistic self-focusing permitted a come-back of the Bobin-Chu side-on ignition of uncompressed deuterium-tritium (DT) fusion fuel. The plasma blocks for the side-on ignition have to be produced by the well confirmed nonlinear force acceleration which is about 100,000 times higher than thermo-kinetic fluid-dynamic acceleration for comparison with astrophysical cases. It is essential that the dielectric plasma properties within the nonlinear force are used. Using the measured ion beam densities above 10¹¹ A s/cm² the ignition mechanism needed numerical and theoretical studies of extremely strong shock phenomena. When extending these results to the side-on ignition of uncompressed hydrogen-boron11 (HB11), surprisingly, the ignition by this shock mechanism was only about 10 times more difficult than for DT in contrast to ignition by spherical laser driven compression using thermo-kinetic conditions in which case HB11 ignition is 100,000 times more difficult than DT.     

Displaced non-Keplerian orbits using impulsive thrust

This paper investigates new families of displaced, highly non-Keplerian orbits in the two-body problem and artificial equilibria in the circular restricted three-body problem. The families of orbits presented extend prior work by using periodic impulses to generate displaced orbits rather than continuous thrust. The new displaced orbits comprise a sequence of individual Keplerian arcs whose intersection is continuous in position, with discontinuities in velocity removed using impulses. For frequent impulses the new families of orbits approximate continuous thrust non-Keplerian orbits found in previous studies. To generate approximations to artificial equilibria in the circular restricted three-body problem, periodic impulses are used to generate a sequence of connected three-body arcs which begin and terminate at a fixed position in the rotating frame of reference. Again, these families of orbits reduce to the families of artificial equilibria found using continuous thrust.     

Impacts of the Wenchuan Earthquake on the giant panda nature reserves in China

The Wenchuan Earthquake that occurred in May of 2008 caused damages to large areas of Sichuan, Gansu, and Shaanxi provinces in China. Reports from local governments and related management agencies show that the giant panda nature reserves in the earthquake-hit areas were heavily damaged. Our estimates in this paper of the impacts of the earthquake on the giant panda in the earthquake-hit areas were made based on the interpretation of remote sensing images and information collected by field survey. A rapid assessment method was designed to estimate the damages of the earthquake on giant panda habitats. By using visual interpretation methods, we decoded the remote sensing images of the disaster area in the 49 giant panda nature reserves. Research results showed that the Wenchuan Earthquake and the succeeding secondary geological disasters caused great damages to the giant panda nature reserves and disturbed the normal life of the giant pandas there (e.g., landscape fragmentation increased significantly). Undoubtedly, the life of the giant pandas there was affected. However, although the earthquake caused certain impacts on the giant pandas, it did not really threat their survival. Even so, we still strongly advocate for protection of the giant pandas, and have prioritized a couple of measures to be taken to restore the giant panda nature reserves in the earthquake-hit areas.     

Community structure and seasonal variation of soil arthropods in the forest-steppe ecotone of the mountainous region in Northern Hebei,China

Soil fauna have been receiving more and more attention because they play an important role in nutrient cycling. However, there is a lack of information on soil arthropods in the forest-steppe ecotone in the mountainous region of northern Hebei, which makes it difficult to meet the need of protecting biodiversity in this area. Soil arthropod communities were investigated in the forest-steppe ecotone in northern Hebei province to provide basic information on changes in mountain soil fertility, which could promote the development of soil arthropod communities in mountain ecotones. From the preliminary identification, a total of 7994 individual soil arthropods were collected, which belonged to 25 groups, 6 classes and 24 orders. Acarina, Hymenoptera and Collembola were the dominant groups in the ecotone. The number of Acarina was higher than Collembola, and this phenomenon was obviously different from other areas in the same climate zone. The increased abundance of rare groups in the Forest zone with the richer vegetation, higher arthropod abundance and more substantial litter depth, could be interpreted as a reaction to the suitable soil environment and food supply. And these rare groups were sensitive to environmental changes, which could be regarded as biotic indicators for evaluating soil quality. The analysis of community diversity showed that the abundance index (d), the Shannon-Wiener index (H′), the evenness index (J) and the density-group index (DG) were significantly higher in the forest zone, lower in the forest-steppe zone, and lowest in the meadow-steppe zone. Seasonal variations in community composition correlated with changes in average air temperature and precipitation in this ecotone. Groups and individuals of soil arthropod communities in the three zones were present in greater numbers in the middle of the rainy season than in the early or late periods of the rainy season as a whole. At the same time, seasonal changes in soil arthropod communities from different plots were also influenced by habitat condition.     

Regional difference in social capital and its impact on regional economic growth in China

Social capital has played an increasingly important role in regional development. China is a country with high stocks of social capital. Using several different indicators of social capital, this study tries to research the regional disparities in social capital and the influence of social capital on economic growth of China in 1978–2004. Measuring social capital with indicators of associations, charities and blood donation rates, this study finds significant regional disparities in social capital at provincial level in China. Those indicators for social capital are highly correlated with regional economic performance. Statistical analysis shows that social capital has a significant and positive effect on a long-term provincial economic growth. This relationship exists after controlling policy, macro location factors, and per capita GDP in the initial year. The empirical findings indicate that institutions, culture and social relations are critical for regional development in China. Therefore, the creation and support of social capital should be paid more attention to when making regional policy.     

Remote sensing of ecosystem services: An opportunity for spatially explicit assessment

Ecosystem service is an emerging concept that grows to be a hot research area in ecology. Spatially explicit ecosystem service values are important for ecosystem service management. However, it is difficult to quantify ecosystem services. Remote sensing provides images covering Earth surface, which by nature are spatially explicit. Thus, remote sensing can be useful for quantitative assessment of ecosystem services. This paper reviews spatially explicit ecosystem service studies conducted in ecology and remote sensing in order to find out how remote sensing can be used for ecosystem service assessment. Several important areas considered include land cover, biodiversity, and carbon, water and soil related ecosystem services. We found that remote sensing can be used for ecosystem service assessment in three different ways: direct monitoring, indirect monitoring, and combined use with ecosystem models. Some plant and water related ecosystem services can be directly monitored by remote sensing. Most commonly, remote sensing can provide surrogate information on plant and soil characteristics in an ecosystem. For ecosystem process related ecosystem services, remote sensing can help measure spatially explicit parameters. We conclude that acquiring good in-situ measurements and selecting appropriate remote sensor data in terms of resolution are critical for accurate assessment of ecosystem services.     

Social construction functions of consumption space under stratification: The case of Guangzhou

As Chinese cities rapidly transformed themselves into consumerist societies, the relationship between consumers and consumption space under stratification has become a new research area in the field of urban social geography. Based on a consumer behavior analysis, this study explores the relationship between consumption space and the social strata of consumers in typical shopping malls in Guangzhou where the first shopping mall in China was built. The result shows that shopping malls have performed significant constructive functions of organizing consumers from different social classes into different consumption space. For middle- and upper-class consumers, the function of shopping malls centers on utilitarian consumption, identity recognition, and identity construction; whereas for lower-class consumers, its function revolves around pleasure and enjoyment. The symbolism of consumption space is the underlying reason for shopping malls to have their social constructive function. The findings of this research suggest that: 1) a shopping mall is a productive consumption space and a geographical space with subjectivity; 2) the micro-location of a shopping mall has social construction function; and 3) symbolic consumption is the core of social construction.