OH超脉泽源的模型与统计分析

本文提出OH超脉泽源的一个具体模型,在该模型中OH超脉泽源由非饱和的球型子源组成.在此估算出超脉泽星系致密射电核的尺度和连续谱亮温度,以及OH源距星系核的最小非饱和距离.计算表明,OH超脉泽源所包含的子源数目可能相当大.R_H～log ρ_(25μm)/ρ_(60μm)图、log L_(OH)/L_(IR)～log ρ_(25μm)/ρ_(60μm)图和其它结果显示,有一部分OH超脉泽源很可能是弱饱和的,本文对此作了解释.     

珲春中部土壤常量元素地球化学特征

采用XRF-X荧光光谱法,研究了吉林省珲春中部常量元素在表层土壤中的含量以及在土壤剖面中的迁移分布等土壤地球化学特征.结果表明:表层土壤中MgO(0.85%)、CaO(0.95%)的含量平均值低于全国土壤平均值(分别为1.8%和3.2%),Fe2O3(3.41%)、K2O(2.61%)、Al2O3(13.33%)、SiO2(69.25%)含量平均值与全国平均值基本相当(分别为3.40%,2.50%,12.60%和65.00%),Na2O(1.83%)含量平均值高于全国平均值(1.60%).暗棕壤和白浆土两种类型土壤剖面常量元素组成差别不大,在垂向上呈现出不同的规律性.Sa、Saf和ba指标反映出暗棕壤土壤的风化淋溶度略强于白浆土,在剖面不同层次上,随土壤深度的增加,Sa和Saf呈现下降的趋势,而表层土壤的ba值比深层土壤高.     

Phytoplankton of the Barents Sea at the Polar Front in Spring

Oceanology - This paper describes the comprehensive studies of phytoplankton carried out in April 2018 in the northwestern Barents Sea, in the Polar Front region (74.8°–76.2° N), at...     

Cosmic‐ray rejection for single spectroscopic CCD images by means of template matching

This article describes a novel algorithm for cosmic‐ray rejection in single spectroscopic CCD images. This algorithm is based on a variation of template matching. It focuses on identifying those pixels belong to spectra, while other conventional algorithms tried to locate the cosmic‐ray hits directly. The main principle is applying template matching to find suspicious blocks, which is followed by surface patching to locate the legitimate pixels accurately. Therefore, the rest pixels are the ones corrupted by cosmic‐ray hits. Meanwhile, almost all the parameters are automatically extracted from the images. Examples of its performance are given for both simulated and observed images. It shows an advantage of significantly low false alarm rate with relatively high detection rate (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Seasonal soil water storage changes beneath central Amazonian rainforest and pasture

Evaporation and infiltration were compared for tropical rainforest and pasture, near to Manaus, Brazil from October 1990 to February 1992 using measurements of soil water storage over a depth of 2 m. The soil is a clayey oxisol of low water available capacity. In both of the dry seasons studied, the maximum change in soil water storage in the forest was 154 mm and in the pasture it was 131 and 112 mm. Similar behaviour of the soil water reservoir below forest and pasture in the wet season implied that differences in evaporation and drainage were small. In the dry season, soil water storage behaviour in the upper metre of the soil was similar but there were marked differences in the second metre. The pasture took up little water from below 1.5 m but the forest appeared to utilise all of the available water in the 2 m profile in both seasons.

The water balance of the 2 m profile showed that the pasture evaporation rate was equal to that of the forest until storage had decreased 80 mm from the maximum. There was then a decline in pasture evaporation rate to 1.2 mm day⁻¹ as the storage decreased by a further 50 mm. In contrast, the forest uptake rate remained above 3.5 mm day⁻¹ until storage had decreased 140 mm from the maximum (within 15 mm of the extraction limit), before declining abruptly to less than 1.5 mm day⁻¹. There was strong evidence that the forest was able to abstract water from depths greater than 3.6 m.

Spatial variability of soil water storage was significantly greater beneath the pasture than beneath the forest, particularly following rainfall events in the dry season. This was largely the result of redistribution of rainfall as local surface runoff. There was no evidence of redistribution or runoff in the forest.     

Directional seas should be ergodic

Directional seas are often modelled as a double summation of plane sinusoidal waves from different directions at a set of discrete frequencies. Unfortunately, this model is commonly used in a way which produces unrealistic standing wave phenomena and hence is not ergodic. Consequently, time averages of variables are not necessarily the same as space averages and averages over different realisations. The resulting point spectrum is randomly distributed about the target point spectrum as required, but the time history generated is only representative of a short record of the target sea. In this note, the basis of the phenomenon and its consequences for both wave tank and computer simulation work are described. Two alternative techniques of directional wave generation are discussed.

Standing waves also occur near reflectors in the sea and test tanks; their effects on point and directional wave measurements are discussed.     

Responses of marine phytoplankton in iron enrichment experiments in the northern North Sea and northeast Atlantic Ocean

Short-term iron enrichment experiments were carried out with samples collected in areas with different phytoplankton activity in the northern North Sea and northeast Atlantic Ocean in the summer of 1993. The research area was dominated by high numbers of pico-phytoplankton, up to 70,000 ml⁻¹. Maximum chlorophyll a concentrations varied from about 1.0 μg l⁻¹ in a high-reflectance zone (caused by loose coccoliths, remnants from a bloom of Emiliania huxleyi) and about 3.5 μg l⁻¹ in a zone in which the phytoplankton were growing, to about 0.5 μg l⁻¹ in the northeast Atlantic Ocean. From the high-reflectance zone to the northeast Atlantic Ocean, nitrate concentrations increased from 0.5 μM to 6.0 μM. Concentrations of reactive iron in surface water showed an opposite trend and decreased from about 2.6 nM in the high-reflectance zone to <1.0 nM in the northeast Atlantic Ocean. In the research area, no signs of true iron deficiency were found, but iron enrichments in the high-reflectance zone, numerically dominated by Synechococcus sp., resulted in increased nitrate uptake. Ammonium uptake was hardly affected. Strong support for the effect of Fe on cell physiology is given by the increase in the f-ratio. Net growth rates of the phytoplankton (changes in cell numbers over 24 h) were almost unchanged. Phytoplankton collected from the northeast Atlantic Ocean, did not show changes in the nitrogen metabolism upon addition of iron. Net growth rates in these incubations were low or negative, with only slightly higher values with additional iron.     

Early diagenesis of phytyl esters in a contemporary temperate intertidal sediment

Analysis of a sediment core for hydrolysed chlorins (acidic chlorins e.g. pheophorbide a) and non-acidic chlorins, and free, bound and esterified alcohols have been performed and the results have been interpreted in terms of input and sedimentary interconversions. There is an association of the acidic chlorin input with an input of unesterified aliphatic n-alkanols (> C₂₀), and subsequent degradation of the chlorins with depth. Input of phytol to the anoxic region of the sediment is not associated with the n-alkanols:phytol in the sediment is derived largely from chlorophyll-a input to the surface layers as intact microalgae. Degradation with depth involves conversion of the chlorophyll-a to non-chlorin, colourless phytyl esters prior to incorporation of the phytol into a bound fraction. At depth this bound phytol is hydrolysed resulting in release of free phytol.