Use of artificial neural networks to identify the origin of green macroalgae

This study demonstrates application of artificial neural networks (ANNs) for identifying the origin of green macroalgae (Enteromorpha sp. and Cladophora sp.) according to their concentrations of Cd, Cu, Ni, Zn, Mn, Pb, Na, Ca, K and Mg. Earlier studies confirmed that algae can be used for biomonitoring surveys of metal contaminants in coastal areas of the Southern Baltic. The same data sets were classified with the use of different structures of radial basis function (RBF) and multilayer perceptron (MLP) networks. The selected networks were able to classify the samples according to their geographical origin, i.e. Southern Baltic, Gulf of Gdańsk and Vistula Lagoon. Additionally in the case of macroalgae from the Gulf of Gdańsk, the networks enabled the discrimination of samples according to areas of contrasting levels of pollution. Hence this study shows that artificial neural networks can be a valuable tool in biomonitoring studies.     

5. Prebiotic Chemistry – Biochemistry – Emergence of Life (4.4–2 Ga)

This chapter is devoted to a discussion about the difficulties and even the impossibility to date the events that occurred during the transition from non-living matter to the first living cells. Nevertheless, the attempts to devise plausible scenarios accounting for the emergence of the main molecular devices and processes found in biology are presented including the role of nucleotides at early stages (RNA world). On the other hand, hypotheses on the development of early metabolisms, compartments and genetic encoding are also discussed in relation with their role in extant living organisms. The nature of the Last Common Ancestor is also presented as well as hypotheses on the evolution of viruses. The following sections constitute a collection of independent articles providing a general overview of these aspects.     

天然水镁石纤维的化学松解技术

研究了不同表面活性剂对不同等级水镁石纤维的松解效果,通过对纤维悬浮液叩解度、粘度、纤维表面Zeta电位、纤维混凝土强度等的研究,并经扫描电镜分析,证明了化学松解工艺对水镁石纤维具有较好地劈分作用。表面活性剂种类及用量对纤维的叩解度、纤维的表面电位、悬浮液粘度均有影响,对不同等级纤维的影响有差异。随表面活性剂用量增加,纤维的叩解度、纤维表面的负电荷量、悬浮液的粘度一般均呈增加趋势。经过化学分散试验,水镁石纤维得到了较好松解,纤维直径由微米级下降至纳米级。将水镁石纤维应用于混凝土,抗折强度随纤维叩解度的增加而提高,说明纤维的化学分散有利于纤维对混凝土增强作用的发挥。     

A Comparison of Stiff ODE Solvers for Astrochemical Kinetics Problems

The time dependent chemical rate equations arising from astrochemical kinetics problems are described by a system of stiff ordinary differential equations (ODEs). In this paper, using three astrochemical models of varying physical and computational complexity, and hence different degrees of stiffness, we present a comprehensive performance survey of a set of well-established ODE solver packages from the ODEPACK collection, namely LSODE, LSODES, VODE and VODPK. For completeness, we include results from the GEAR package in one of the test models. The results demonstrate that significant performance improvements can be obtained over GEAR which is still being used by many astrochemists by default. We show that a simple appropriate ordering of the species set results in a substantial improvement in the performance of the tested ODE solvers. The sparsity of the associated Jacobian matrix can be exploited and results using the sparse direct solver routine LSODES show an extensive reduction in CPU time without any loss in accuracy. We compare the performance and the computed abundances of one model with a 175 species set and a reduced set of 88 species, keeping all physical and chemical parameters identical with both sets.We found that the calculated abundances using two different size models agree quite well. However, with no extra computational effort and more reliable results, it is possible for the computation to be many times faster with the larger species set than the reduced set, depending on the use of solvers, the ordering and the chosen options. It is also shown that though a particular solver with certain chosen parameters may have severe difficulty or even fail to complete a run over the required integration time, another solver can easily complete the run with a wider range of control parameters and options. As a result of the superior performance of LSODES for the solution of astrochemical kinetics systems, we have tailor-made a sparse version of the VODE solver by replacing the full numerical matrix linear algebra component of the standard VODE solver with sparse matrix solver routines. The preliminary tests from the preconditioned iterative solver package VODPK indicate very good results for one of our test models, but not for all of the models.     

Multivariate statistical analysis to identify the major factors governing groundwater quality in the coastal area of Kimje,South Korea

The main purpose of this study is to identify the major factors affecting groundwater quality by means of multivariate statistical analysis of the physico‐chemical compositions. Cluster analysis results show that the groundwater in the study area is classified into four groups (A, B, C and D), and factor analysis indicates that groundwater composition, 81·9% of the total variance of 17 variables, is mainly affected by three factors: seawater intrusion, microbial activity and chemical fertilizers. These results might be related to the geographical characteristics of the study area. The main influence on groundwater in groups B, C and D, which are close to the Yellow Sea and contain reclaimed areas, is the seawater intrusion by the present seawater, the trapped seawater, and microbial activity. Group A, however, has been used for agriculture for a long time, and thus groundwater in this group has been largely affected by chemical fertilizers. As groundwater flows from group A to group D according to its path, the governing factor of the groundwater quality gradually changes from chemical fertilizers to microbial activity and seawater intrusion. Copyright © 2004 John Wiley & Sons, Ltd.     

Stormflow generation in a small rainforest catchment in the Luquillo Experimental Forest,Puerto Rico

Various complementary techniques were used to investigate the stormflow generating processes in a small headwater catchment in northeastern Puerto Rico. Over 100 samples were taken of soil matrix water, macropore flow, streamflow and precipitation, mainly during two storms of contrasting magnitude, for the analysis of calcium, magnesium, silicon, potassium, sodium and chloride. These were combined with hydrometric information on streamflow, return flow, precipitation, throughfall and soil moisture to distinguish water following different flow paths. Geo‐electric sounding was used to survey the subsurface structure of the catchment, revealing a weathering front that coincided with the elevation of the stream channel instead of running parallel to surface topography. The hydrometric data were used in combination with soil physical data, a one‐dimensional soil water model (VAMPS ) and a three‐component chemical mass‐balance mixing model to describe the stormflow response of the catchment. It is inferred that most stormflow travelled through macropores in the top 20 cm of the soil profile. During a large event, saturation overland flow also accounted for a considerable portion of the stormflow, although it was not possible to quantify the associated volume fully. Although the mass‐balance mixing model approach gave valuable information about the various flow paths within the catchment, it was not possible to distill the full picture from the model alone; additional hydrometric and soil physical evidence was needed to aid in the interpretation of the model results. Copyright © 2004 John Wiley & Sons, Ltd.     

E2-transition probabilities for NiXVIII

Accurate theoretical data for the transition probabilities are highly demanding in astrophysics and in the study of plasma in astrophysical objects and fusion devices. Na-like highly stripped ions of iron group, specially NiXVIII is very important in this respect. A highly improved basis in a relativistic many-body coupled-cluster method (CCM) to include correlation properly is employed to calculate excitation energies, the electric quadrupole (E2) transition line strengths and transition probabilities for NiXVIII. The effect of correlation is studied thoroughly. The present improved data for different atomic/ionic properties are compared with the available theoretical and/or experimental data and they are in agreement. Some E2 transition data are reported for the first time. This revised version was published online in July 2006 with corrections to the Cover Date.     

CHEMICAL CHARACTERISTICS OF AEROSOLS IN THE KUROSHIO AREA——II.CHEMICAL FORMS AND SIZE DISTRIBUTIONS OF TRACE METALS

Aerosol samples were collected with a Sierrer Model 235 cascade impactor in the marine atmosphere over the Kuroshio area in consecutive four seasons from 1987 to 1988. Na, G, Al, V, and water soluble and acid soluble Mn, Fe, Pb, Cu, V, Cd were determined by neutron activation analysis and atomic absorption spectrophotometry, respectively. Seawater source chemical species in the aerosols appeared in high content in large over 3.6um diameter particles, and crustal source vanadium appeared in 3.6um diameter particles, but pollution source vanadium appeared in less than 0.52um diameter particles. Trace metals in the aerosols mostly had the highest concentration of water soluble metals on fine particles, and acid soluble metals on large particles. The concentrations of trace metals in the aerosols were higher in autumn and winter, lower in spring and summer.     

气相色谱-质谱法分析香蕉叶挥发油化学成分

采用气相色谱 质谱法 (GC/MS)分析了香蕉叶中挥发油的化学成分 ,鉴定了 2 2个化合物 ,主要成分是十七烷、二十一烷、二十八烷、三十四烷、10 甲基 十九烷、3,7,11,15 四甲基十六烷、十五烷基环己烷等 ,占整个挥发性物质的 6 1.4 5% ;其次是 2 ,6 二叔丁基 4 甲基苯酚 ,占总挥发性物质的 14 .74 %。确认了C2 0 H42 同分异构体。