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Discovery of 13 New Variable Stars in the Field of the Open Cluster NGC 2168 （M35）

A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W UMa systems, one EA type and two EB type eclipsing binaries (one of them could be a W UMa system), and seven pulsating stars including three candidates of δScuti stars.     

Numerical simulation of Pacific water intrusions into Otsuchi Bay,northeast of Japan,with a nested-grid OGCM

A numerical simulation of Otsuchi Bay located on the northeast coast of the Honshu, the largest island of Japan, is conducted, using an ocean general circulation model (OGCM) with a nested-grid system in order to illustrate seasonal variability of the circulation in the bay. Through a year, an anticlockwise circulation is dominant in the bay, as observational studies have implied, although it is modified in the bay-mouth-half of the bay in winter. In addition, there is an intense outflow at the surface layer during spring to autumn, influenced by river water discharge. Intrusion of the Pacific water into the bay is influened by mean circulations, but it is also influenced by baroclinic tides from spring to autumn. Pacific water intrusions affected by baroclinic tides may have an impact on the environment in Otsuchi Bay.     

Respiration and Calcification of <Emphasis Type="Italic">Crassostrea gigas</Emphasis>: Contribution of an Intertidal Invasive Species to Coastal Ecosystem CO<Subscript>2</Subscript> Fluxes

Respiration and calcification rates of the Pacific oyster Crassostrea gigas were measured in a laboratory experiment in the air and underwater, accounting for seasonal variations and individual size, to estimate the effects of this exotic species on annual carbon budgets in the Bay of Brest, France. Respiration and calcification rates changed significantly with season and size. Mean underwater respiration rates, deducted from changes in dissolved inorganic carbon (DIC), were 11.4 μmol DIC g⁻¹ ash-free dry weight (AFDW) h⁻¹ (standard deviation (SD), 4.6) and 32.3 μmol DIC g⁻¹ AFDW h⁻¹ (SD 4.1) for adults (80–110 mm shell length) and juveniles (30–60 mm), respectively. The mean daily contribution of C. gigas underwater respiration (with 14 h per day of immersion on average) to DIC averaged over the Bay of Brest population was 7.0 mmol DIC m⁻² day⁻¹ (SD 8.1). Mean aerial CO₂ respiration rate, estimated using an infrared gas analyzer, was 0.7 μmol CO₂ g⁻¹ AFDW h⁻¹ (SD 0.1) for adults and 1.1 μmol CO₂ g⁻¹ AFDW h⁻¹ (SD 0.2) for juveniles, corresponding to a mean daily contribution of 0.4 mmol CO₂ m⁻² day⁻¹ (SD 0.50) averaged over the Bay of Brest population (with 10 h per day of emersion on average). Mean CaCO₃ uptake rates for adults and juveniles were 4.5 μmol CaCO₃ g⁻¹ AFDW h⁻¹ (SD 1.7) and 46.9 μmol CaCO₃ g⁻¹ AFDW h⁻¹ (SD 29.2), respectively. The mean daily contribution of net calcification in the Bay of Brest C. gigas population to CO₂ fluxes during immersion was estimated to be 2.5 mmol CO₂ m⁻² day⁻¹ (SD 2.9). Total carbon release by this C. gigas population was 39 g C m⁻² year⁻¹ and reached 334 g C m⁻² year⁻¹ for densely colonized areas with relative contributions by underwater respiration, net calcification, and aerial respiration of 71%, 25%, and 4%, respectively. These observations emphasize the substantial influence of this invasive species on the carbon cycle, including biogenic carbonate production, in coastal ecosystems.     

Chemical signature of intermediate water masses along western Portuguese margin

Although the circulation of intermediate water masses in the eastern North Atlantic remains poorly defined, the presence of fresher intermediate waters, the Sub-Artic (SAIW) and the Antarctic Intermediate Water (AAIW), as well the saline intermediate Mediterranean Water (MW), has been tracked using biogeochemical properties. Here we assess the hydrographic and chemical structures of intermediate waters along the western Portuguese margin by examining the vertical distributions and property-property plots of chemical tracers (oxygen and nutrients). AAIW was traced by low oxygen and high nutrients, while SAIW was recognized by low nutrients. The Mediterranean Water (MW) undercurrent is shown to spread towards the eastern flank of Gorringe bank. Concurrently, the fresher waters gained salt by direct incorporation of MW, while this water was enriched in nutrients on its way northward and westward owing, to a great extent, to the entrainment of an AAIW branch. The distributions of nutrients and apparent oxygen utilization are discussed in terms of regional ocean circulation. Our analysis suggests a circulation pattern of the various intermediate waters along the western Portuguese margin: MW extends all over the area, but its presence is more pronounced around cape St. Vincent; SAIW apparently moves southward, reaching the Gorringe bank region, and AAIW flows northward along the coast and around the bank.     

Present-day oxidative subsidence of organic soils and mitigation in the Sacramento-San Joaquin Delta,California, USA

Subsidence of organic soils in the Sacramento-San Joaquin Delta threatens sustainability of the California (USA) water supply system and agriculture. Land-surface elevation data were collected to assess present-day subsidence rates and evaluate rice as a land use for subsidence mitigation. To depict Delta-wide present-day rates of subsidence, the previously developed SUBCALC model was refined and calibrated using recent data for CO₂ emissions and land-surface elevation changes measured at extensometers. Land-surface elevation change data were evaluated relative to indirect estimates of subsidence and accretion using carbon and nitrogen flux data for rice cultivation. Extensometer and leveling data demonstrate seasonal variations in land-surface elevations associated with groundwater-level fluctuations and inelastic subsidence rates of 0.5–0.8 cm yr^–1. Calibration of the SUBCALC model indicated accuracy of ±0.10 cm yr^–1 where depth to groundwater, soil organic matter content and temperature are known. Regional estimates of subsidence range from <0.3 to >1.8 cm yr^–1. The primary uncertainty is the distribution of soil organic matter content which results in spatial averaging in the mapping of subsidence rates. Analysis of leveling and extensometer data in rice fields resulted in an estimated accretion rate of 0.02–0.8 cm yr^–1. These values generally agreed with indirect estimates based on carbon fluxes and nitrogen mineralization, thus preliminarily demonstrating that rice will stop or greatly reduce subsidence. Areas below elevations of –2 m are candidate areas for implementation of mitigation measures such as rice because there is active subsidence occurring at rates greater than 0.4 cm yr^–1.     

人海河流河口及其近海水域盐度分析方法浅析

在水质监测及水环境调查中,盐度分析工作是一个重要环节,根据现行的<水质分析国家标准>,<海洋调查规范>,地表水及生活用水的盐度分析一般采用前者,而海洋水样则采用后者.对于长江口及其近海水域既有适用<水质分析国家标准>(TB11896-89)的区段,又有适用<海洋调查规范>的区域,亦有两者都不适用的部分.本文通过对长江口盐度分析方法的研究.阐述了该区域进行水样盐度分析的各种方法的适用范围及提高效率保证成果质量的办法.最后作者提出的人海河流河口及其近海水域盐度分析的方法是:按取样地点位于河口的具体位置来选择其分析方法.     

New stacked central configurations for the planar 5-body problem

A stacked central configuration in the n-body problem is one that has a proper subset of the n-bodies forming a central configuration. In this paper we study the case where three bodies with masses m ₁, m ₂, m ₃ (bodies 1, 2, 3) form an equilateral central configuration, and the other two with masses m ₄, m ₅ are symmetric with respect to the mediatrix of the segment joining 1 and 2, and they are above the triangle generated by {1, 2, 3}. We show the existence and non-existence of this kind of stacked central configurations for the planar 5-body problem.     

陕西黄土高原人工林土壤干层及形成原因

1 Introduction Abroad, a lot of research on soil water removal, seeping and evaporation has been done (Ole, 1998; Rapp, 2000). A seeping model of soil water was suggested (Yuin, 1998) and it was known that water removal is very slow in the unsaturated zon…     

Element sets for high-order Poincaré mapping of perturbed Keplerian motion

The propagation and Poincaré mapping of perturbed Keplerian motion is a key topic in Celestial Mechanics and Astrodynamics, e.g., to study the stability of orbits or design bounded relative trajectories. The high-order transfer map (HOTM) method enables efficient mapping of perturbed Keplerian orbits using the high-order Taylor expansion of a Poincaré or stroboscopic map. The HOTM is only accurate close to the expansion point and therefore the number of revolutions for which the map is accurate tends to be limited. The proper selection of coordinates is of key importance for improving the performance of the HOTM method. In this paper, we investigate the use of different element sets for expressing the high-order map in order to find the coordinates that perform best in terms of accuracy. A new set of elements is introduced that enables extremely accurate mapping of the state, even for high eccentricities and higher-order zonal perturbations. Finally, the high-order map is shown to be very useful for the determination and study of fixed points and center manifolds of Poincaré maps.