Biodegradation of dissolved organic carbon in soil extracts and leachates from a temperate forest stand and its relationship to ultraviolet absorbance

The amount and biodegradability of dissolved organic carbon (DOC) in forest floors can contribute to carbon sequestration in soils and the release of CO 2-C from soil to the atmosphere.There is only limited knowledge about the biodegradation of DOC in soil extracts and leachates due to the limitations inherent in degradation experiments.Differences in the biodegradation of DOC were studied in forest soil extracts using cold and hot water and 4 mmol/L CaCl 2 solution and in soil leachates sampled under different conditions over a wide range of DOC concentrations.From these results,we developed a simple and rapid method for determining the biodegradable organic C in forest floors.The hot water extracts and CaCl 2 extracts after CH 3 Cl fumigation contained higher concentrations of biodegradable organic C than the cold water extracts and CaCl 2 extracts before fumigation,with rapid DOC degradation occurring 24-48 h after incubation with an inoculum,followed by slow DOC degradation till 120-168 h into the incubation.During a 7-d incubation with an inoculum,the variation in DOC degradation in the different soil extracts was consistent with the change in special UV absorbance at 254 nm.Relatively higher levels of biodegradable organic C were detected in soil leachates from the forest canopy than in forest gaps between April and October 2008 (P <0.05).Relatively lower concentrations of DOC and biodegradable organic C were observed in soil leachates from N-fertilized plots during the growing season compared with the control,with the exception of the plot treated with KNO 3 at a rate of 45 kg N ha 1 a 1.Around 77.4% to 96.3% of the variability in the biodegradable organic C concentrations in the forest floors could be accounted for by the initial DOC concentration and UV absorbance at 254 nm.Compared with the conventional inoculum incubation method,the method of analyzing UV absorbance at 254 nm is less time consuming and requires a much smaller sample volume.The results suggest that the regression models obtained using the initial DOC concentration and UV absorbance can provide a rapid,simple and reliable method for determining the biodegradable organic C content,especially in field studies involving relatively large numbers of samples.     

Segregation of a missense mutation in the amyloid precursor protein gene with familial Alzheimer's disease.

A locus segregating with familial Alzheimer's disease (AD) has been mapped to chromosome 21, close to the amyloid precursor protein (APP) gene. Recombinants between the APP gene and the AD locus have been reported which seemed to exclude it as the site of the mutation causing familial AD. But recent genetic analysis of a large number of AD families has demonstrated that the disease is heterogeneous. Families with late-onset AD do not show linkage to chromosome 21 markers. Some families with early-onset AD show linkage to chromosome 21 markers, but some do not. This has led to the suggestion that there is non-allelic genetic heterogeneity even within early onset familial AD. To avoid the problems that heterogeneity poses for genetic analysis, we have examined the cosegregation of AD and markers along the long arm of chromosome 21 in a single family with AD confirmed by autopsy. Here we demonstrate that in this kindred, which shows linkage to chromosome 21 markers, there is a point mutation in the APP gene. This mutation causes an amino-acid substitution (Val----Ile) close to the carboxy terminus of the beta-amyloid peptide. Screening other cases of familial AD revealed a second unrelated family in which this variant occurs. This suggests that some cases of AD could be caused by mutations in the APP gene.     

Study on pitting process of 316L stainless steel by means of staircase potential electrochemical impedance spectroscopy

Pitting corrosion of 316L stainless steel in NaCl solution was investigated by means of staircase potential electrochemical impedance spectroscopy (SPEIS). The investigation focused on the transition of stainless steel from the passive state to pitting corrosion. Based on the evolution of electrical parameters of the equivalent electrical circuit, it is suggested that the most probable mechanism of pit creation is the film breaking model. The result demonstrates that staircase potential electrochemical impedance spectroscopy is an effective method for the investigation of pitting corrosion.     

Soil fertility limits carbon sequestration by forest ecosystems in a CO2-enriched atmosphere

Northern mid-latitude forests are a large terrestrial carbon sink. Ignoring nutrient limitations, large increases in carbon sequestration from carbon dioxide (CO2) fertilization are expected in these forests. Yet, forests are usually relegated to sites of moderate to poor fertility, where tree growth is often limited by nutrient supply, in particular nitrogen. Here we present evidence that estimates of increases in carbon sequestration of forests, which is expected to partially compensate for increasing CO2 in the atmosphere, are unduly optimistic. In two forest experiments on maturing pines exposed to elevated atmospheric CO2, the CO2-induced biomass carbon increment without added nutrients was undetectable at a nutritionally poor site, and the stimulation at a nutritionally moderate site was transient, stabilizing at a marginal gain after three years. However, a large synergistic gain from higher CO2 and nutrients was detected with nutrients added. This gain was even larger at the poor site (threefold higher than the expected additive effect) than at the moderate site (twofold higher). Thus, fertility can restrain the response of wood carbon sequestration to increased atmospheric CO2. Assessment of future carbon sequestration should consider the limitations imposed by soil fertility, as well as interactions with nitrogen deposition.     

Size-dependent optical properties of Au nanorods

In the fast evolving field of nanoscience and nanotechnology,where size and shape are crucial in deciding the optoelectronic properties of nanomaterials,the understanding of size and shape dependent behavior is of direct relevance to device applications.Present study reports the synthesis of Au nanorods with well controlled aspect ratios,and the influence of the aspect ratio on the surface enhanced Raman scattering(SERS) activity using crystal violet(CV) as the probe molecule.The influence of pH and the concentrations of reducing agent and Ag ions in controlling the aspect ratio of gold nanorods are also investigated.The structural and optical properties of the synthesized samples have been characterized by transmission electron microscopy(TEM) and UV-visible absorption spectroscopy.The nonlinear optical(NLO) transmission of the Au nanorods investigated using the open aperture Z-scan technique revealed the absorption saturation followed by an optical limiting behavior,which may find potential applications in optoelectronic nanodevices.     

Simulation of wind gust structure in the atmospheric boundary layer with Lattice Boltzmann Method

Cold fronts occur in northern East Asia during winter and spring.After cold frontal passage,airflow is downward and accompa-nying strong winds fluctuate significantly;this is termed wind gusts.Analysis of observation data shows that wind gust structure has coherent characteristics.This is important for entrainment of spring dust storms into the upper boundary layer,where they are transported great distances.The Lattice Boltzmann Method(LBM) is a computational fluid technique based on the Boltzmann transport equation.The LBM has been used to study complex motion such as turbulence,because it describes motion at the micro level.In this paper,Large eddy simulation is introduced in the LBM,enabling simulation of turbulent flow in the atmospheric boundary layer.The formation and development of wind gusts are simulated,and a coherent structure with a combination of wave and vortex is obtained.This explains the mechanism of soil erosion and sand entrainment by the coherent structure of wind gusts.     

Cluster Synchronization in a Complex Dynamical Network with Two Nonidentical Clusters

This paper further investigates cluster synchronization in a complex dynamical network with two-cluster. Each cluster contains a number of identical dynamical systems, however, the subsystems composing the two clusters can be different, i.e., the individual dynamical system in one cluster can differ from that in the other cluster. Complete synchronization within each cluster is possible only if each node from one cluster receives the same input from nodes in other cluster. In this case, the stability condition of one-cluster synchronization is known to contain two terms： the first accounts for the contribution of the inner-cluster coupling structure while the second is simply an extra linear term, which can be deduced by the ＂same-input＂ condition. Applying the connection graph stability method, the authors obtain an upper bound of input strength for one cluster if the first account is known, by which the synchronizability of cluster can be scaled. For different clusters, there are different upper bound of input strength by virtue of different dynamics and the corresponding cluster structure. Moreover, two illustrative examples are presented and the numerical simulations coincide with the theoretical analysis.     

A STAGE-STRUCTURED SI ECO-EPIDEMIOLOGICAL MODEL WITH TIME DELAY AND IMPULSIVE CONTROLLING*

This paper formulates a robust stage-structured SI eco-epidemiological model with periodic constant pulse releasing of infectious pests with pathogens. The authors show that the conditions for global attractivity of the ＇pest-eradication＇ periodic solution and permanence of the system depend on time delay, hence, the authors call it ＂profitless＂. Further, the authors present a pest management strategy in which the pest population is kept under the economic threshold level （ETL） when the pest population is uniformly persistent. By numerical analysis, the authors also show that constant maturation time delay for the susceptible pests and pulse releasing of the infectious pests can bring obvious effects on the dynamics of system.     

Robust model predictive control of continuous uncertain systems*

The authors concern robust model predictive control for linear continuous systems with polytopic uncertainties and input constraints. At each sampling time, a piecewise constant control sequence is obtained by solving a set of linear matrix inequalities. The sufficient conditions on the existence of the model predictive control are given, and the robust stability of the closed-loop systems is guaranteed. A simulation example illustrates the efficiency of the proposed method.     

Participatory Sustainability Impact Assessment: Scientific Policy Advice as a Social Learning Process

This paper deals with the development of scientific policy advice by providing a methodology to foster a social learning process. The methodology, called participatory Sustainability Impact Assessment (pSIA), aims to structure complex problem situations, to clarify interests and basic assumptions, to interpret scientific studies, to develop impact assessment, and to explore sensitivity of uncertainty and lack of information. In pSIA workshops the participants are supposed to build conceptual models with different modelling methods, like System Dynamics, Value Chain Analysis, and Morphological Analysis. A case study is presented that describes a workshop series with political as well as academic actors, applying the pSIA approach to an impact assessment of Economic Partnership Agreements between the European Union and the Eastern and Southern Africa Region.