Structural path analysis of ecosystem networks

This paper explains the application of structural path analysis (SPA), an input–output-based technique for measuring flows in ecological and linked ecological–economic networks. Previous methods of input–output flow analysis have concluded with aggregate indexes relying on the summing feature of the Leontief inverse in order to completely account for throughflows along a multitude of inter-compartmental paths. This paper shows that for most linear dissipative networks, a manageable number of paths of limited length exist that cover in the order of 99% or more of total throughflow. These paths can be conveniently extracted, enumerated and ranked using SPA.     

A Markovian model for ecosystem flow analysis

Nutrient flow through ecosystems is modeled as a discrete Markov chain whose transition probabilities are stationary or time inhomogenous according to whether a steady state or dynamic ecosystem is modeled, respectively. Expected residence time and number of intercompartmental transfers for a nutrient within a set of compartments are derived. Variances of these random variables are also considered. A measure for ecosystem resource recycling is given as a weighted sum of probabilities.     

简便、快速、低成本处理畜禽粪便的方法研究

提出了一种简便、快速、低成本进行畜禽粪便堆肥化处理的方法。该方法利用三面墙式水泥地,池底用竹笆架空,进料口用竹笆堵挡,以增加氧气供应,并用半熟腐堆肥进行水分调节。堆肥温度上升快、温度高、水分蒸发量大、发酵迅速,一次发酵时间可缩短至2～3周,适合于我国中小型养殖企业采用。     

A simple and precise method for fitting a von Bertalanffy growth curve

The parameter K of the von Bertalanffy equation, as developed by Beverton and Holt (1957), is first estimated by the relation $$\log _e \left( {dL_t /dt} \right) = A - Kt$$ where dLt/dt denotes growth increments per a unit of age, t denotes age, and A is a constant. The K estimate is used to evaluate L∞; $$L_\infty = \left( {e^K \sum\limits_2^n {L_t - \sum\limits_1^{n - 1} {L_t } } } \right)/\left( {n - 1} \right)\left( {e^K - 1} \right)$$ The L∞ estimate is used to estimate t _o, and to obtain a better estimate for K; $$\log _e \left( {1 - L_t /L_\infty } \right) = - Kt + Kt_0 $$ The K estimate may be used to obtain another estimate for L∞. Solved examples show that a single iteration is sufficient to obtain fitted equations which are, on the average, as precise as equations fitted by the least squares method shown by Tomlinson and Abramson (1961). This new method can be used, with a slight modification, for the second equation given above, if growth data have unequal age intervals. The variance of K, t _o and log _e L∞ can be estimated by applying the simple methods used in the case of straight-line relationships.     

A Markov random field spatio-temporal analysis of ocean temperature

The National Oceanic Data Center (NODC) contains historical records from approximately 144,000 hydrographic stations in the North Atlantic. This data has been used by oceanographers to construct maps of point estimates of pressure, temperature, salinity and oxygen in the North Atlantic (Levitus (1994); Lozier et al. (1995)). Because data from any particular year are scarce, the previous maps have been for time-averaged values only. In addition, the maps have been reported without uncertainty estimates. This paper presents a Markov random field (MRF) analysis that can generate maps for specific time periods along with associated uncertainties. To estimate changes in oceanic properties over time previous oceanographic work has focused on differences between a few time periods each having many observations. Due to data scarcity this poses a severe restriction for both spatial and temporal coverage of climatic change. The MRF analysis provides a means for temporal modeling that does not require high data density at each time period. To demonstrate the usefulness of a MRF analysis of oceanic data we investigate the temporal variability along 24.5°N in the North Atlantic. Our results are compared to an earlier analysis (Parrilla et al. (1994)) where data from only three time periods was used. We obtain a more thorough understanding of the temperature change found by this previous study.     

A novel method for mapping reefs and subtidal rocky habitats using artificial neural networks

Reefs and subtidal rocky habitats are sites of high biodiversity and productivity which harbour commercially important species of fish and invertebrates. Although the conservation management of reef associated species has been informed using species distribution models (SDM) and community based approaches, to date their use has been constrained to specific regions where the locality and spatial extent of reefs is well known. Much of the world's subtidal habitats remain either undiscovered or unmapped, including coasts of intense human use. Consequently, to facilitate a stronger understanding of species-environmental relationships there is an urgent need for a cost and time effective standard method to map reefs at fine spatial resolutions across broad geographical extents. We used bathymetric data (∼250 m resolution) to calculate the local slope and curvature of the seabed. We then constructed artificial neural networks (ANNs) to forecast the probability of reef occurrence within grid cells as a function of bathymetric and slope variables. Testing over an independent data set not used in training showed that ANNs were able to accurately predict the location of reefs for 86% of all grid cells (Kappa = 0.63) without over fitting. The ANN with greatest support, combining bathymetric values of the target grid cell with the slope of adjacent grid cells, was used to map inshore reef locations around the Southern Australian coastline (∼250 m resolution). Broadly, our results show that reefs are identifiable from coarse-scale bathymetry data of the seabed. We anticipate that our research technique will strengthen systematic conservation planning tools in many regions of the world, by enabling the identification of rocky substratum and mapping in localities that remain poorly surveyed due to logistics or monetary constraints.     

Planning for robust reserve networks using uncertainty analysis

Planning land-use for biodiversity conservation frequently involves computer-assisted reserve selection algorithms. Typically such algorithms operate on matrices of species presence–absence in sites, or on species-specific distributions of model predicted probabilities of occurrence in grid cells. There are practically always errors in input data—erroneous species presence–absence data, structural and parametric uncertainty in predictive habitat models, and lack of correspondence between temporal presence and long-run persistence. Despite these uncertainties, typical reserve selection methods proceed as if there is no uncertainty in the data or models. Having two conservation options of apparently equal biological value, one would prefer the option whose value is relatively insensitive to errors in planning inputs. In this work we show how uncertainty analysis for reserve planning can be implemented within a framework of information-gap decision theory, generating reserve designs that are robust to uncertainty. Consideration of uncertainty involves modifications to the typical objective functions used in reserve selection. Search for robust-optimal reserve structures can still be implemented via typical reserve selection optimization techniques, including stepwise heuristics, integer-programming and stochastic global search.     

一种经济、简单的微生物基因组DNA的提取方法

获得一定浓度和纯度的DNA是进行分子生物学研究的基础。破解细胞壁与细胞膜是获得基因组DNA的前提，而蛋白质和核酸物质的分离是获得高质量DNA产物的关键。目前，主要采用的破壁方法有：冷冻研磨法、溶菌酶法、EDTA测等，这些方法一般采用复杂的裂解液体系，并借助蛋白酶K和RNA酶的帮助来获得高质量的抽提产物。由于细胞裂解体系不仅配制十分麻烦，而日部分药品有毒操作危险性大，此外部分药品及相关酶试剂价格昂贵。本文充分利用DNA在不同温度下自身可变性与复性的特性和在高盐与高温条件下蛋白质能够变性并沉淀。以无菌的SDS（c／c=20％）和NaCl（c/c=8％）的混合液作裂解体系，在沸水浴中破壁膜并使得部分的蛋白质变性和DNA变性并得到初步分离；随后在60℃和72℃水浴中使变性的DNA复性和重新凝聚，同时让RNA、蛋白质和细胞壁碎片等杂质降解或沉淀，从而获得高质量的DNA产物。     

A new method for spatially moving correlation analysis in geomedicine

A method of correlation analysis within a spatially moving window was applied to two sets of epidemiological/geochemical data in Norway, (1) mortality/disability rates of multiple sclerosis (MS) versus atmospheric fallout of Mg and concentrations of Se in overbank sediment, and (2) incidence rates of malignant melanoma of the skin (MM) versus concentrations of Ca and K in overbank sediment. It appears that n = 17 observation sites within the moving window is a practical compromise between noise in the data at small values of n and a spatial resolution good enough to detect trends in the distribution patterns of the correlation coefficient. For MS versus Mg, MS versus Se and MM versus Ca the correlation coefficients are generally negative and depict systematic distribution patterns with anomalous clusters of sites with good correlation. For MS versus Se the correlation coefficients also form an additional cluster of positive coefficients. Tests with permutated data show that more than 70% of the negative correlation coefficients for MS versus Mg and for MM versus Ca are both significantly different from zero at p<0.05, while less than 15% of those for MS versus Se are significant at the same level. For MM versus K the correlation coefficients are randomly distributed and not significantly different from zero. The described correlations may be effects of confounders and do not per se indicate any causal relationships. However, further research based on these results may well lead to the identification of possible aetiological factors.     

A simple and cheap method for preparation of coupled ZrO2/ZnO with high photocatalytic activities

The objective of this study was to prepare a new photocatalyst with high activities for degradation of organic pollutants. Coupled ZrO₂/ZnO photocatalyst was prepared with a simple precipitation method with cheap raw materials zinc acetate and zirconium oxychloride, and was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Reactive brilliant red X-3B was used as a model compound to investigate the photocatalytic activity of synthesized catalysts in water under 254 nm UV irradiation. Results show that the optimal calcination temperature and coupling molar ratio of Zr were 350°C And 2.5%, respectively. At the calcination temperature of 350°C, ZrO₂ was dispersed on the surface of hexagonal ZnO in the form of amorphous clusters. The particle size of ZrO₂/ZnO decreased with the decrease of calcination temperature and the increase of Zr coupling amount. ZrO₂/ZnO has better photocatalytic activity for degradation of reactive brilliant red (RBR) X-3B than pure ZnO and P25-TiO₂.     

A simple ligandless microextraction method based on ionic liquid for the determination of trace cadmium in water and biological samples

A simple and efficient ionic liquid-based ligandless microextraction method has been developed for preconcentration of cadmium ions (Cd²⁺) as a step prior to its determination by flame atomic absorption spectrometry (FAAS) with a micro-sample introduction system. In this approach, the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆] and ethanol were used as extractant and dispersive solvents to preconcentrate the Cd²⁺ in different waters, acid digested scalp hair, and nail samples. Some analytical parameters influencing the extraction efficiency of Cd²⁺ and its subsequent determination, including pH, IL volume, dispersant solvent volume, sample volume, temperature, incubation time, and matrix effect, were optimized. Under optimal conditions, the limit of detection (LOD), limit of quantification (LOQ), and enhancement factor (EF) were 0.4 μg L^?1, 1.3 μg L^?1, and 50, respectively. The relative standard deviation (RSD) of 100 μgL^?1 Cd²⁺ was 4.3% (n = 6). The validity of the proposed method was checked by determining Cd²⁺ in certified reference material (TM-25.3 fortified water) and standard addition; the results showed sufficient recovery (>98%) of Cd²⁺ within the certified value. The method was applied for preconcentration and determination of cadmium in waters and biological samples.     

A simple bioassay for feeding-stimulants for the young seahare Aplysia juliana

Water extracts of a green alga (Ulva sp.) are known to elicit phagostimulatory responses against a seahare Aplysia sp. In 1984 we happened, however, to find that a seahare shows its feeding preference for filter paper on which an ether extract of Ulva sp. had been absorbed. We succeeded in establishing a simple and reliable bioassay procedure for the feeding-stimulants for the seahare A. juliana, which is applicable to isolation of the active principles.Chemical Studies on Phagostimulants for Marine Gastropods, Part V. For Part IV, see Sakata et al. (1985)     

Randomly selected order statistics in ranked set sampling: A less expensive comparable alternative to simple random sampling

Rank-based sampling designs are powerful alternatives to simple random sampling (SRS) and often provide large improvements in the precision of estimators. In many environmental, ecological, agricultural, industrial and/or medical applications the interest lies in sampling designs that are cheaper than SRS and provide comparable estimates. In this paper, we propose a new variation of ranked set sampling (RSS) for estimating the population mean based on the random selection technique to measure a smaller number of observations than RSS design. We study the properties of the population mean estimator using the proposed design and provide conditions under which the mean estimator performs better than SRS and some existing rank-based sampling designs. Theoretical results are augmented with some numerical studies and a real-life example, where we also study the performance of our proposed design under perfect and imperfect ranking situations.     

生态经济系统的一种整合评价方法:能值理论与分析方法

能值理论与分析方法是目前系统生态学和生态经济学发展的新成果，为复合生态系统开拓了一条定量研究途径，是连接生态学和经济学的桥梁。其理论研究与实践应用具有重要的科学意义和应用意义。文章论述了能值分析理论与分析方法的产生背景、过程、主要的基本概念、特点，指出了其需要解决的问题；并以种植业系统为例，简要介绍了能值分析的基本方法和步骤以及能值指标的计算。     

A sensitivity analysis of an ecosystem model of estuarine carbon flow

The North Inlet Marsh-Estuarine System Model (NIMES) is a 19-compartment real-time deterministic ecosystem simulation model of intrasystem carbon flow and exchange between an estuary and adjacent coastal water. A complete sensitivity analysis of this model with regard to POM, DOM and nekton annual exchange and annual system net productivity was completed and the functional relationship between these system behaviors and the perturbed parameters were determined by regression techniques. Simulated POM annual exchange between the estuary and the sea was largely controlled by offshore POM concentration, water column respiration and the gross productivity of the marsh and water column flora. Simulated DOM annual estuarine-oceanic exchange was most sensitive to perturbations in the gross productivity and biomass changes in marsh flora and water column microbial DOM uptake. Simulated nekton exchange reflected a sensitivity to migratory behavior and subtidal benthic biomass changes. System annual net productivity as simulated by the model showed a high sensitivity to all model processes which affected component primary production and respiration. From this sensitivity analysis, a scheme is developed to evaluate research needs for further model development for the North Inlet ecosystem.     

A simple and cheap apparatus for the controlled feeding of suspension feeders

A simple and cheap device, which allows a controlled and continuous food supply of suspension feeding animals in long term experiments, has been developed and is described.     

Soil irrigation with treated wastewater: A simple,reduced scale,evaluation method

A laboratory scale method is proposed in order to establish the advantages and disadvantages of reclaimed wastewater irrigation. Data on possible environmental impact (on groundwater and soils) of such irrigation practices are obtained by using lysimetric columns. At the same time it is possible to gather data about treated wastewater nutrient content.

Global results of percolating ions and vegatative growth on columns data are shown.     

Modelling the effect of in-stream and overland dispersal on gene flow in river networks

Modelling gene flow across natural landscapes is a current challenge of population genetics. Models are essential to make clear predictions about conditions that cause genetic differentiation or maintain connectivity between populations. River networks are a special case of landscape matrix. They represent stretches of habitat connected according to a branching pattern where dispersal is usually limited to upstream or downstream movements. Because of their peculiar topology, and the increasing concern about conservation issues in hydrosystems, there has been a recent revival of interest in modelling dispersal in river networks. Network complexity has been shown to influence global population differentiation. However, geometric characteristics are likely to interact with the way individuals move across space. Studies have focused on in-stream movements. None of the work published so far took into consideration the ability of many species to disperse overland between branches of the same network though. We predicted that the relative contribution of these two dispersal modalities (in-stream and overland) would affect the overall genetic structure. We simulated dispersal in synthetic river networks using an individual-based model. We tested the effect of dispersal modalities, i.e. the ratio of overland/in-stream dispersal, and two geometric parameters, bifurcation angle between branches and network complexity. Data revealed that if geometrical parameters affected population differentiation, dispersal parameters had the strongest effect. Interestingly, we observed a quadratic relationship between p the proportion of overland dispersers and population differentiation. We interpret this U-shape pattern as a balance between isolation by distance caused by in-stream movements at low values of p and intense migrant exchanges within the same branching unit at high values of p. Our study is the first attempt to model out-of-network movements. It clearly shows that both geometric and dispersal parameters interact. Both should be taken into consideration in order to refine predictions about dispersal and gene flow in river network.     

Modelling hydraulic jump using the bubbly two-phase flow method

Hydraulic jumps have complex flow structures, characterised by strong turbulence and large air contents. It is difficult to numerically predict the flows. It is necessary to bolster the existing computer models to emphasise the gas phase in hydraulic jumps, and avoid the pitfall of treating the phenomenon as a single-phase water flow. This paper aims to improve predictions of hydraulic jumps as bubbly two-phase flow. We allow for airflow above the free surface and air mass entrained across it. We use the Reynolds-averaged Navier–Stokes equations to describe fluid motion, the volume of fluid method to track the interface, and the k–ε model for turbulence closure. A shear layer is shown to form between the bottom jet flow and the upper recirculation flow. The key to success in predicting the jet flow lies in formulating appropriate bottom boundary conditions. The majority of entrained air bubbles are advected downstream through the shear layer. Predictions of the recirculation region’s length and air volume fraction within the layer are validated by available measurements. The predictions show a linear growth of the shear layer. There is strong turbulence at the impingement, and the bulk of the turbulence kinetic energy is advected to the recirculation region via the shear layer. The predicted bottom-shear-stress distribution, with a peak value upstream of the toe of the jump and a decaying trend downstream, is realistic. This paper reveals a significant transient bottom shear stress associated with temporal fluctuations of mainly flow velocity in the jump. The prediction method discussed is useful for modelling hydraulic jumps and advancing the understanding of the complex flow phenomenon.     

A note concerning time parameterization of Markovian models of ecosystem flow analysis

A continuous Markovian model of resource flow in a steady state ecosystem model is developed. This model calculates the mean and variance of the frequency of intercompartmental cyclings and duration of compartmental residence times. This model is compared with an analogous discrete Markovian flow model to demonstrate the sensitivity of discrete and continuous ecosystem flow analyses. Appropriate time parameterization of of discrete Markovian flow models is then discussed with special reference to Shannon's theorem of dynamic system sampling.