Transport characteristics of space charge-dominated multi-species deuterium beam in electrostatic low-energy beam line

The transport characteristics of a space chargedominated multi-species deuterium beam consisting of D_1^+,D_2^+, and D_3^+ particles in an electrostatic low-energy beam line are studied. First, the envelope equations of the primary D_1^+ beam are derived considering the space charge effects caused by all particles. Second, the evolution of the envelope of the multi-species deuterium beam is simulated using the PIC code TRACK, with the results showing a significant effect of the unwanted beam on the transport of the primary beam. Finally, different injected beam parameters are used to study beam matching, and a new beam extraction system for the existing duoplasmatron source is designed to obtain the ideal injected beam parameters that allow a D_1^+ beam of up to 50 m A to pass unobstructed through the electrostatic low-energy beam transport line in the presence of an unwanted(D_2^+, D_3^+)beam of 20 m A; at the same time, distortions of the beam emittance and particle distributions are observed.

A numerical model study on multi-species harmful algal blooms coupled with background ecological fields

Based on systematized physical, chemical, and biological modules, a multi-species harmful algal bloom （HAB） model coupled with background ecological fields was established. This model schematically embod-ied that HAB causative algal species and the background ecological system, quantified as total biomass, were significantly different in terms of the chemical and biological processes during a HAB while the inter-action between the two was present. The model also included a competition and interaction mechanism between the HAB algal species or populations. The Droop equation was optimized by considering tempera-ture, salinity, and suspended material impact factors in the parameterization of algal growth rate with the nutrient threshold. Two HAB processes in the springs of 2004 and 2005 were simulated using this model. Both simulation results showed consistent trends with corresponding HAB processes observed in the East China Sea, which indicated the rationality of the model. This study made certain progress in modeling HABs, which has great application potential for HAB diagnosis, prediction, and prevention.

Identification and Characterization of Métiers in Multi-Species Artisanal Fisheries. A Case Study in Northwest Spain

Artisanal fisheries are characterized by using a vast array of different fishing gears and target species. Such heterogeneity has traditionally complicated their management and the availability of accurate data on fishing effort and incomes. This study identifies and characterizes the métiers currently used by an artisanal fishing fleet based in a coastal Atlantic region in South-Europe (Asturias, Northwest Spain), by applying an integrated method of analysis which combines administrative data on fishing licenses, daily sales statistics and information from surveys. As a result, 21 artisanal fishing métiers have been identified, with special relevance of the trammel net (targeting Lophius spp.), the Merluccius longline and the Merluccius gillnet métiers. Spatio-temporal patterns of fishing effort have been also described, and outputs and inputs demands per métier have been quantified. It has been also found a high degree of alternation between different métiers during the fishing season and significant differences in terms of technical aspects and workforce. Finally, fishermen’s short- and long-term strategies (métier choice) are discussed, different comparisons are made on the basis of other South-European studies and main findings are linked to artisanal fisheries management.

A novel method of utilizing static mixer to obtain mixing homogeneity of multi-species powders in laser metal deposition

Real-time mixing of multi-species powder challenges Laser Metal Deposition(LMD)of Functionally Graded Materials(FGMs).The current work proposes a novel method of using a static mixer to realize rapid,uniform multi-species powder mixing.Firstly,copper powder and 316L stainless steel powder are selected to complete the powder mixing observation experiment with Scanning Electron Microscope(SEM)and Energy Dispersive Spectrometer(EDS).Secondly,computational fluid dynamics and particle mixing simulation models are used to analyze the flow field and particle motion characteristics in the static mixer.Finally,LMD experiment and metallo-graphic observation are carried out with 316L stainless steel powder and WC powder to verify the feasibility of the static mixer.This study provides a theoretical and practical basis for powder mixing in laser processing with a static mixer.The conclusions can also be applied to other processing fields requiring real-time and uniform mixing of multi-species powders.

Potential distributional shifts in North America of allelopathic invasive plant species under climate change models

Predictive studies play a crucial role in the study of biological invasions of terrestrial plants under possible climate change scenarios.Invasive species are recognized for their ability to modify soil microbial communities and influence ecosystem dynamics.Here,we focused on six species of allelopathic flowering plants-Ailanthus altissima,Casuarina equisetifolia,Centaurea stoebe ssp.micranthos,Dioscorea bulbifera,Lantana camara,and Schinus terebinthifolia-Xhat are invasive in North America and examined their potential to spread further during projected climate change.We used Species Distribution Models(SDMs)to predict future suitable areas for these species in North America under several proposed future climate models.ENMEval and Maxent were used to develop SDMs,estimate current distributions,and predict future areas of suitable climate for each species.Areas with the greatest predicted suitable climate in the future include the northeastern and the coastal northwestern regions of North America.Range size estimations demonstrate the possibility of extreme range loss for these invasives in the southeastern United States,while new areas may become suitable in the northeastern United States and southeastern Canada.These findings show an overall northward shift of suitable climate during the next few decades,given projected changes in temperature and precipitation.Our results can be utilized to analyze potential shifts in the distribution of these invasive species and may aid in the development of conservation and management plans to target and control dissemination in areas at higher risk for potential future invasion by these allelopathic species.

Competition effects in an afrotemperate forest

Background： Information about competition responses is mainly available for monospecific stands or mixed stands with a small number of species. Studies on complex multi-species and highly structured forest ecosystems are scarce. Accordingly, the objective of this study was to quantify competition effects and analyse competition responses in a species-diverse afrotemperate forest in South Africa, based on an observational study with mapped tree positions and long-term diameter increment records. Methods： The sensitivity to competition was analysed for individual species and involved the calculation of the slope of the linear relation between the value of a competition index （CI） and diameter growth as a measure of sensitivity. In a next step different competition indices were combined and tree diameters were grouped in three classes as surrogates for canopy status and ontogenetic stage. Results： Five competition indices were found to be effective in showing sensitivity to competition for a number of canopy and sub-canopy species. Significant linear regressions were fitted for 18 of a total of 25 species. Species reactions varied significantly in their sensitivity to the different CIs. The indices were classified as belonging to two groups, those that responded more to local crowding and those that are more sensitive to overtopping, which revealed species-specific sensitivities to both factors. The analysis based on diameter classes revealed that species clearly changed their sensitivity to crowding or overtopping depending on diameter. Canopy and sub-canopy species showed distinct differences in their reactions. Conclusions： The application of multiple CIs brought novel insights relating to the dynamics of afrotemperate forests. The response patterns to different competition indices that focus on crowding and overtopping are varied and tree diameter dependent, indicating that oversimplified assumptions are not warranted in the interpretation of Cl- growth relations.

An Evaluation of the Selectivity Characteristics of Different Juvenile Fish Escape Panel Designs for the Demersal Trap Fishery of Abu Dhabi, United Arab Emirates

The selectivity characteristics of 4 juvenile fish escape panel designs and their utility for the regulation of a multi-species demersal trap fishery were evaluated using a suite of objective socio-economic and biological criteria. The panel designs consisted of a control (type A) which had a hexagonal mesh size which was the same as that of the body of the trap (3.5 cm), a rectangular mesh (type B) which was representative of the current regulation (5.0 x 7.6 cm) and 2 escape panels with square meshes of 7.5 x 7.5 cm (type C) and 10.0 x 10.0 cm (type D). The results demonstrated that there was only a limited reduction in the proportion of juvenile fish and by-catch retained for the existing juvenile escape panel design (type B). Furthermore, as the selectivity characteristics for the key species (Epinephelus coioides and Diagramma pictum) were similar to the control type, the predicted increases in yields, revenues and spawning stock biomass were small by comparison. The escape panel with the largest mesh size (type D) retained the least un-utilized and discarded by-catch. Whilst simulations predicted the highest spawner biomass per recruit, long term yields and revenues for the key species, its use was associated with a dramatic short-term decline in revenues which were 23.3% of the value of the control type. Traps fitted with the type C which had a square mesh of 7.5 x 7.5 cm had the lowest juvenile retention and the highest overall score for all the assessment criteria combined. The study provides an empirical basis for gear regulations for the demersal trap fishery of the Emirate of Abu Dhabi and the wider Arabian Gulf region.

Geochemical characteristics from tests of four modern planktonic foraminiferal species in the Indonesian Throughflow region and their implications

Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those established from other regions can be broadly applied. In this study, characteristics of6180 and Mg/Ca from tests of four planktonic foraminiferal species, Globigerinoides ruber sensu stricto(s.s.), Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, from 60 coretop sediment samples retrieved from the Indonesian Throughflow(ITF) region were studied. These geochemical data were compared with modern hydrographic profiles in order to assess their relations and to investigate potential implications of test geochemical parameters in reconstructing past oceanographic change in the ITF region. Calcification depths of these four species were first estimated based on comparison between measured test δ180 and predicted calcite δ^(18)O that was calculated from modern temperature and salinity. The results indicate that G. ruber s.s. and G. sacculifer calcify within the mixedlayer at 0-50 m and 20-75 m, respectively, whereas P. obliquiloculata and N. dutertrei calcify within the thermocline at around 75 to 125 m. A combined study of excess Mg/Ca(difference between measured and predicted Mg/Ca) and salinity suggests that salinity exerts a negligible impact on test Mg/Ca of these foraminiferal species in the ITF region. Comparison of test Mg/Ca-derived temperatures with temperature profiles of the upper 200 m of the water column from the seas of the ITF region also indicate calcification depths of these species, which match well with the above estimations using test δ^(18)O. It further indicates that G. sacculifer may be more sensitive in reflecting changes in the depth of the mixedlayer, highlighting a potential use of Mg/Ca temperature difference between G. ruber s.s. and G. sacculifer in reconstructing the depth of the mixed-layer in the ITF region.

Fish Assemblages in the Degraded Mangrove Ecosystems of the Coastal Zone, Benin, West Africa: Implications for Ecosystem Restoration and Resources Conservation

Mangrove forests are unique habitats in their function as potential food source and nurseries, and support an important fisheries resource. In the Benin coastal zone, the mangrove fishes have been surveyed to investigate fish species diversity, community structures and ecosystem degradation impacts in order to protect and to improve the mangrove fish resources. Results from wet, high-water and dry season samplings revealed that the two dominant mangrove species, Rizophora racemosa and Avicennia africana, are being intensively degraded for domestic use such as firewood and house building. Fifty one (51) fish species belonging to 25 families were recorded with Eleotridae (7 species), Cichlidae (5 species), and Mugilidae (5 species), the most speciose families. Dominant trophic guilds were detritivores (54.57%) and planktinovores/microcarnivores (30.41%). Six (6) species, Sarotherodon melanotheron, Dormitator lebretonis, Gerres melanopterus, Hemichromis fasciatus, Ethmalosa fimbriata, and Aplocheilichthys spilauchen, dominated the samples and accounted for about 80.27%. Sarotherodon melanotheron constituted the major dominant species and accounted numerically for about 29% of the total catches and 46.7% of the total biomass. The Margalef index of species richness ranged between 2.42 and 4.43, the Shannon-Weaver index of species diversity between 1.39 and 2.27, and the evenness between 0.50 and 0.62. Lower indices were observed for the highly degraded and the moderately degraded sites whereas higher indices were recorded for the less degraded and the restored sites. Species richness, species diversity and dominant species abundance were positively correlated with depth and transparency and negatively correlated with temperature. Multi-species fisheries dominate the coastal zone with Sarotherodon melanotheron, Dormitator lebretonis, Gerres melanopterus, Ethmalosa fimbriata, Liza falcipinus, Mugil sp. and Chrysichthys nigrodigitatus, the major species in the commercial catches. In addition to the mangrove destruction, the hydro electrical dam have greatly modified the Mono River flooding regime, water quality and the fish composition of the Benin coastal lagoon system. An integrated approach of the mangrove resource management/conservation, including intensive mangrove restoration, management of key fish species, freshwater prawns (Macrobrachiun sp.), peneids shrimps, mangrove oysters (Crassostrea sp.), and crabs (Callinectes sp., Cardiosoma sp.), and habitat protection is required for ecosystem recovery and sustainable exploitation.

Multi-scale habitat selection and impacts of climate change on the distribution of four sympatric meso-carnivores using random forest algorithm

Background:The habitat resources are structured across different spatial scales in the environment,and thus animals perceive and select habitat resources at different spatial scales.Failure to adopt the scale-dependent framework in species habitat relationships may lead to biased inferences.Multi-scale species distribution models(SDMs)can thus improve the predictive ability as compared to single-scale approaches.This study outlines the importance of multi-scale modeling in assessing the species habitat relationships and may provide a methodological framework using a robust algorithm to model and predict habitat suitability maps(HSMs)for similar multi-species and multi-scale studies.Results:We used a supervised machine learning algorithm,random forest(RF),to assess the habitat relationships of Asiatic wildcat(Felis lybica ornata),jungle cat(Felis chaus),Indian fox(Vulpes bengalensis),and golden-jackal(Canis aureus)at ten spatial scales(500-5000 m)in human-dominated landscapes.We calculated out-of-bag(OOB)error rates of each predictor variable across ten scales to select the most influential spatial scale variables.The scale optimization(OOB rates)indicated that model performance was associated with variables at multiple spatial scales.The species occurrence tended to be related strongest to predictor variables at broader scales(5000 m).Multivariate RF models indicated landscape composition to be strong predictors of the Asiatic wildcat,jungle cat,and Indian fox occurrences.At the same time,topographic and climatic variables were the most important predictors determining the golden jackal distribution.Our models predicted range expansion in all four species under future climatic scenarios.Conclusions:Our results highlight the importance of using multiscale distribution models when predicting the distribution and species habitat relationships.The wide adaptability of meso-carnivores allows them to persist in human-dominated regions and may even thrive in disturbed habitats.These meso-carnivores are among the few species that may benefit from climate change.

Analysis of Mathematics and Numerical Pattern Formation in Superdiffusive Fractional Multicomponent System

In this work,we examine the mathematical analysis and numerical simulation of pattern formation in a subdiffusive multicomponents fractional-reactiondiffusion system that models the spatial interrelationship between two preys and predator species.The major result is centered on the analysis of the system for linear stability.Analysis of the main model reflects that the dynamical system is locally and globally asymptotically stable.We propose some useful theorems based on the existence and permanence of the species to validate our theoretical findings.Reliable and efficient methods in space and time are formulated to handle any space fractional reaction-diffusion system.We numerically present the complexity of the dynamics that are theoretically discussed.The simulation results in one,two and three dimensions show some amazing scenarios.