Changes In Potential Distribution Research Articles

Predicting the potential distribution of geographically-limited species, Apsylla cistellata Buckton (Psyllidae: Hemiptera) on mango (Mangifera indica) under different climate change scenarios

The aim of present study was to predict the potential distribution of mango shoot gall psylla, Apsylla cistellata (Psyllidae: Hemiptera) under current and future climate scenarios of 2050 and 2070. This study was conducted across six states in India where their infestation and occurrence noticed. The study provided a deep insight on surveys of shoot gall psylla infestation that occurred between 2012 and 2018. Current and future climate change scenarios acquired from the WorldClim database and Maxent modeling technique was used to fit with occurrence points and current climate data to model potential shoot gall psylla distributions. The model performance was tested using area under the curve (AUC) of the receiver operating characteristic (ROC) values. Response curves depicted the relationships between bioclimatic variables and predicted probability of A.cistellata presence. MaxEnt model used to develop spatial map and their distributions for selected climate change scenarios (RCP2.6, RCP 4.5. RCP 6.0 and RCP 8.5) and mapped the habitat for A.cistellata suitability under current and future scenarios. Present study results suggested that under current climate change scenarios, the potential distribution of shoot gall psylla was noticed in Western and Central part of Uttar Pradesh and Eastern part of Madhya Pradesh. In future climate change scenarios predicted suitable habitat areas for A.cistellata was found mostly from regions of Western and Central Uttar Pradesh, Southern parts Himachal Pradesh and Uttarakhand. The predicted suitability maps developed from present study will be useful in planning and designing of pest management strategies to control pest effectively from designated areas. The study provides clutches of clues for understanding potential changes in distribution and activity of pest in designated areas in response to current and future climate change scenarios.

Species‐specific transpiration and water use patterns of two pioneer dominant tree species under manipulated rainfall in a low‐subtropical secondary evergreen forest

AbstractLike many other ecosystems, subtropical forests are suffering more intense and longer droughts with the ongoing climate change. This study aimed to explore the seasonal transpiration and physiological responses of two dominant tree species, Schima superba and Michelia macclurei, to manipulated precipitation patterns in a subtropical evergreen forest of South China, in which an ambient control treatment (BC), a drier dry and wetter wet season treatment (DD) and an extended dry and wetter wet season treatment (ED) were applied. Tree water use and associated ecophysiological characters, such as the daily whole‐tree transpiration (EL), intrinsic water use efficiency (WUEi), Huber values (As:Al) and utilization proportions from different water sources were determined during the period from October 2012 to September 2013. For both tree species, no significant difference in transpiration among the three treatments was observed in the wet season, and a relatively stronger decrease of transpiration occurred under DD and ED treatments during the later dry season. Moreover, the higher transpiration of M. macclurei and its advantage of utilizing the shallow water derived from light rainfall under dry condition suggested that it has more survival and growth advantages in this subtropical forest. Therefore, under the seasonal drought caused by uneven distribution of rainfall in the future, M. macclurei that inclines to use shallow soil water would adopt a drought‐avoidance strategy, whereas S. superba that could uptake deeper soil water would be drought tolerant. The different spatial and temporal patterns of water use, together with the contrasting water use strategies, could reduce competition of the two species and facilitate their coexistence under potential precipitation distribution changes.

Modelling habitat suitability for occurrence of human tick-borne encephalitis (TBE) cases in Finland

The numbers of reported human tick-borne encephalitis (TBE) cases in Europe have increased in several endemic regions (including Finland) in recent decades, indicative of an increasing threat to public health. As such, it is important to identify the regions at risk and the most influential factors associated with TBE distributions, particularly in understudied regions. This study aimed to identify the risk areas of TBE transmission in two different datasets based on human TBE disease cases from 2007 to 2011 (n = 86) and 2012–2017 (n = 244). We also examined which factors best explain the presence of human TBE cases. We used ensemble modelling to determine the relationship of TBE occurrence with environmental, ecological, and anthropogenic factors in Finland. Geospatial data including these variables were acquired from several open data sources and satellite and aerial imagery and, were processed in GIS software. Biomod2, an ensemble platform designed for species distribution modelling, was used to generate ensemble models in R. The proportion of built-up areas, field, forest, and snow-covered land in November, people working in the primary sector, human population density, mean precipitation in April and July, and densities of European hares, white-tailed deer, and raccoon dogs best estimated distribution of human TBE disease cases in the two datasets. Random forest and generalized boosted regression models performed with a very good to excellent predictive power (ROC = 0.89–0.96) in both time periods. Based on the predictive maps, high-risk areas for TBE transmission were located in the coastal regions in Southern and Western Finland (including the Åland Islands), several municipalities in Central and Eastern Finland, and coastal municipalities in Southern Lapland. To explore potential changes in TBE distributions in future climate, we used bioclimatic factors with current and future climate forecast data to reveal possible future hotspot areas. Based on the future forecasts, a slightly wider geographical extent of TBE risk was introduced in the Åland Islands and Southern, Western and Northern Finland, even though the risk itself was not increased. Our results are the first steps towards TBE-risk area mapping in current and future climate in Finland.

Evaluation of conformational and spectral behavior and prediction of biological activity and chemical reactivity descriptors of Levosimendan

The conformational behavior and structural stability of Levosimendan (LVM) is investigated by density functional theory. The spectroscopic properties are analyzed using 1H NMR, FT-IR and Raman techniques. The 1H NMR chemical shifts of the molecule are calculated by Gauge independent atomic orbital method and compared with the experimental results. The vibrational spectra have been interpreted with the aid of normal coordinate analysis. A comparison of normal modes of both the conformers has been made in terms of change in wavenumbers, intensities and potential energy distribution. Lipophilicity and aqueous solubility have been calculated to estimate the absorption and distribution properties of drug which dictate the success or failure rate of drug discovery and development. ‘Prediction of Activity Spectra for Substances’ analysis has been done to predict the possible biological activities of LVM. Molecular docking has been performed to investigate the potential of the LVM molecule to bind with human cardiac troponin C receptor. Several chemical reactivity descriptors such as ionization energy, electron affinity, chemical potential, global hardness and electrophilicity have been evaluated to understand the molecular properties. The possible electrophilic and nucleophilic reactive sites of the molecule are studied using molecular electrostatic potential surface and Fukui function.

Distribution Pattern of Endangered Plant Semiliquidambar cathayensis (Hamamelidaceae) in Response to Climate Change after the Last Interglacial Period

Semiliquidambar cathayensis is a special and endangered plant in China, used for traditional Chinese medicine and in landscape applications. Predicting the impact of climate change on the distribution of S. cathayensis is crucial for its protection and the sustainable use of resources. We used the maximum entropy (MaxEnt) model optimized by the ENMeval data packet to analyze the potential geographic distribution changes of S. cathayensis in 12 provinces of Southern China for the different periods since the last interglacial period (LIG, 120–140 ka). Considering the potential geographic distribution changes in the province, and based on the two climate scenarios of Representative Concentration Pathways (RCP) 2.6 and RCP 8.5, the distribution range of S. cathayensis was analyzed and we predicted the range for the 2050s (average for 2041–2060) and 2070s (average for 2061–2080). The area under AUC (Area under the receiver operating characteristic (ROC) curve) is 0.9388 under these parameters, which indicates that the model is very accurate. We speculate that the glacial period refugia were the Nanling and Wuyi Mountains for S. cathayensis, and central and Western Fujian and Taiwan are likely to be the future climate refugia. In the mid-Holocene (MH, 6 ka), the growth habitat was 32.41% larger than the modern habitat; in the 2050s and 2070s (except RCP2.6–2070s), the growth habitat will shrink to varying degrees, so efforts to support its in situ and ex situ conservation are urgently needed. The jackknife test showed that the main factors affecting the geographical distribution of S. cathayensis were annual precipitation, precipitation of the wettest month, and precipitation of the driest month. The annual precipitation may be the key factor restricting the northward distribution of S. cathayensis. In general, the centroid of the distribution of S. cathayensis will move northward. The centroid of the adaptive habitats will move northward with the highest degree of climate abnormality. We think that Hainan Island is the most likely origin of S. cathayensis. These findings provide a theoretical basis for the establishment of genetic resources protection measures, the construction of core germplasm resources, and the study of the formation and evolution of Hamamelidaceae.

Dental Practice Integration into Primary Care: A Microsimulation of Financial Implications for Practices.

Given the widespread lack of access to dental care for many vulnerable Americans, there is a growing realization that integrating dental and primary care may provide comprehensive care. We sought to model the financial impact of integrating dental care provision into a primary care practice. A microsimulation model was used to estimate changes in net revenue per practice by simulating patient visits to a primary dental practice within primary care practices, utilizing national survey and un-identified claims data from a nationwide health insurance plan. The impact of potential changes in utilization rates and payer distributions and hiring additional staff was also evaluated. When dental care services were provided in the primary care setting, annual net revenue changes per practice were −$92,053 (95% CI: −93,054, −91,052) in the first year and $104,626 (95% CI: 103,315, 105,316) in subsequent years. Net revenue per annum after the first year of integration remained positive as long as the overall utilization rates decreased by less than 25%. In settings with a high proportion of publicly insured patients, the net revenue change decreased but was still positive. Integrating primary dental and primary care providers would be financially viable, but this viability depends on demands of dental utilization and payer distributions.

Phylogeography of the Volcano Rabbit (Romerolagus diazi): the Evolutionary History of a Mountain Specialist Molded by the Climatic-Volcanism Interaction in the Central Mexican Highlands

Processes such as climate fluctuations together with recent volcanism have driven the diversification and local persistence of biodiversity within the Mexican highlands. We reconstruct the phylogeographic pattern and historical demography of the volcano rabbit, Romerolagus diazi, an endemic lagomorph in central Mexico, to elucidate the effect of the climate-volcanism interaction on its evolutionary history. We sequenced two mtDNA regions for 152 individuals from 45 sample sites located at the volcanic fields Sierra Chichinautzin and Sierra Nevada. We surveyed the genetic diversity, and reconstructed and dated an intraspecific phylogeny. The effective population size trough time was estimated, and an Ecological Niche Model was projected onto the past. Results showed a well-supported phylogeny with five monophyletic lineages with a north to south geographic pattern at Sierra Nevada, and east to west at Sierra Chichinautzin. Dating estimates indicated that those lineages might have started their diversification ca. 1.4 Ma, which agrees with the geological dating reported for the volcanic fields rising. We detected changes in demographic history and potential distribution, with a global population expansion during the Last Glacial Maximum and a retraction during the Last Interglacial period. The molecular evidence showed that the volcano rabbit had a dynamic evolutionary history molded by geological and climatic events during the Pleistocene. The volcanic events that shaped Sierra Chichinautzin and Sierra Nevada generated regions that allowed the colonization, isolation and posterior in-situ diversification of their populations. Additionally, the climatic fluctuations of the latest glacial-interglacial cycles promoted altitudinal populations shifts, with a sky-island dynamic that allowed their persistence.

Invasion risk of the South American tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in India: predictions based on MaxEnt ecological niche modelling

The South American tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a recent invasion in India, causing widespread infestations in tomato crop in the States of central peninsula, especially Maharashtra and Karnataka. Hitherto, this pest was not reported to occur in India and thus presumed to be of exotic origin. The present study attempted to delineate the potential habitat suitability of geographical areas for spread and distribution of T. Absoluta in India. We have modelled the potential habitat distribution of T. absoluta using algorithm in Maxent, a maximum entropy modelling program. The climate niche for T. absoluta was developed based on the relationship between presence only data for 64 places and a reference climate data for the year 2000. This established relationship was then used to predict the changes in potential distribution under future climatic conditions of 2050. The future climate data from SRES A1b emission scenario at a resolution of 10 arc minutes were used for analysing climate change impacts. The predictions from Maxent were mapped in DIVA GIS, an open source computer aided tool for mapping and analysing spatial data. The established model in Maxent gave a reasonable estimate of T. absoluta range with better discrimination of suitable and unsuitable areas for its occurrence under current and future climatic conditions. This was evident from the highest value of AUC i.e. 0.968 and 0.874 for training and test data, respectively. A Jacknife test for variable importance indicated that Bio3 (isothermality) with highest gain value was the most important abiotic factor influencing the potential habitat distribution of T. absoluta. Temperatures >30 °C and precipitation >500 mm were found to have detrimental effects on distribution of T. absoluta. The modelled habitat distribution of T. absoluta will be a useful guide for researchers and plant protection workers to frame appropriate management strategies against this invading pest insect to cope with the future climate change conditions.

Changes in potential geographical distribution of <i>Tsoongiodendron odorum</i> since the Last Glacial Maximum

Changes in potential geographical distribution of <i>Tsoongiodendron odorum</i> since the Last Glacial Maximum

A look into the past, present and future potential distributions of Talinopsis frutescens, a North American endemic lineage closely related to Cactaceae

Talinopsis frutescens (Anacampserotaceae, a family that is close related to Cactaceae) is a succulent species endemic to North America. The aim of this study was to explore, using Ecological Niche Modeling (ENM), changes in potential distribution ranges considering different climate scenarios: past conditions during the Last Inter Glacial (LIG) and the Last Glacial Maximum (LGM), the present and projections for 2070 (RCP 2.6 to 8.5). A pattern of contraction is observed during the LIG, which agrees with other studies focused in species from arid environments. This pattern was followed by a migration towards the south during the LGM and a possible recent expansion to the north as is observed in the present scenario. All future projections show the same contraction and fragmentation patterns, resulting in three discontinuous areas: the northern part of the Chihuahuan Desert, the southern-central part of the Mexican Plateau, and the smallest one in the Tehuacan-Cuicatlan Valley. Our projections for future scenarios agree with other studies and support that global climate change tends to alter the current distribution of arid environment species.

Circumpolar patterns of Arctic freshwater fish biodiversity: A baseline for monitoring

Abstract Climate change, biological invasions, and anthropogenic disturbance pose a threat to the biodiversity and function of Arctic freshwater ecosystems. Understanding potential changes in fish species distribution and richness is necessary, given the great importance of fish to the function of freshwater ecosystems and as a resource to humans. However, information gaps limit large‐scale studies and our ability to determine patterns and trends in space and time. This study takes the first step in determining circumpolar patterns of fish species richness and composition, which provides a baseline to improve both monitoring and conservation of Arctic freshwater biodiversity. Information on species presence/absence was gathered from the Circumpolar Biodiversity Monitoring Program's Freshwater Database and used to examine patterns of freshwater fish γ‐, α‐, and β‐diversity across 234° of longitude in the Arctic. The metrics of diversity provided information on species richness and composition across hydrobasins, ecoregions, and Arctic zones. Circumpolar patterns of fish species biodiversity varied with latitude, isolation, and coarse ecoregion characteristics; patterns were consistent with historic and contemporary barriers to colonisation and environmental characteristics. Gamma‐diversity was lower in the high Arctic compared to lower latitude zones, but α‐diversity did not decrease with increasing latitude below 71°N, reflecting glacial history. Alpha‐diversity was reduced to a single species, Arctic charr Salvelinus alpinus, in ecoregions above 71°N, where γ‐diversity was the lowest. Beta‐diversity indicated little variation in the composition and richness of species across the High Arctic; at lower latitudes, ecoregions contained more species, although species composition turned over across large spatial extents. In an analysis of five ecoregions in the circumpolar Arctic, physical isolation, and ecoregion area and topography were identified as strong drivers of γ‐, α‐, and β‐diversity. Physical isolation reduced the γ‐ and α‐diversity, and changes in β‐diversity between adjacent locations were due mainly to losses in species richness, rather than due to differences in species composition. Heterogeneity of habitats, environmental gradients, and geographic distance probably contributed to patterns of fish dissimilarity within and across ecoregions. This study presents the first analysis of large‐scale patterns of freshwater fish biodiversity in the circumpolar Arctic. However, information gaps in space, time, and among taxonomic groups remain. Future inclusion of extensive archive and new data will allow future studies to test for changes and drivers of the observed patterns of biodiversity. This is important given the potential impacts of ongoing and accelerating climate change, land use, and biotic exchange on Arctic fish biodiversity.

Cod and climate: a systems approach for sustainable fisheries management of Atlantic cod (Gadus morhua) in coastal Danish waters

This study applied the Systems Approach Framework (SAF) to address the issue of declining Atlantic cod fishery in coastal areas. Interviews of 58 fishers from 26 harbours and meetings with national fisheries organisations and managers revealed the perception of an offshore movement of coastal cod. Numerical modelling based on fishing survey data did not substantiate these perceptions in the data-poor coastal waters. However, Data Storage Tag (DST) information combined with bottom sea water temperature data from the spatio-temporal hydrodynamic Baltic Sea Ice-Ocean Model showed changes in potential cod habitat distribution in the Skagerrak-Kattegat and western Baltic from 1979 to 2016. Subsequently, cod habitats were defined in three categories: (i) potentially suitable (T ≤ 12 °C); (ii) episodic (12 16 °C). The environmental changes were linked to the socio-economic component of cod fishery. Cod catches (weight and monetary value) were retrieved using logbook information and data from the Vessel Monitoring System (VMS, 2005–2016) and the Automatic Identification System (AIS, 2006-2016). General additive modelling significantly showed the largest proportion of catches took place in the potentially suitable habitat whereas catches were lower in the episodic habitat and rare in the unsuitable habitat. The results of this first large-scale SAF application are highly valuable for adapting existing fisheries management by: (i) providing information on habitat shrinkage for Maximum Sustainable Yield (MSY) based stock assessments; (ii) adding a spatio-temporal dimension for coastal productivity relative to the vessel-based Individual Transferable Quota (ITQ) system; and (iii) providing a predictive scenario simulation tool for sustainable management under changing environmental conditions.

Current and future potential distributions of three Dracaena Vand. ex L. species under two contrasting climate change scenarios in Africa.

Forest undergrowth plants are tightly connected with the shady and humid conditions that occur under the canopy of tropical forests. However, projected climatic changes, such as decreasing precipitation and increasing temperature, negatively affect understory environments by promoting light‐demanding and drought‐tolerant species. Therefore, we aimed to quantify the influence of climate change on the spatial distribution of three selected forest undergrowth plants, Dracaena Vand. ex L. species, D. afromontana Mildbr., D. camerooniana Baker, and D. surculosa Lindl., simultaneously creating the most comprehensive location database for these species to date.A total of 1,223 herbarium records originating from tropical Africa and derived from 93 herbarium collections worldwide have been gathered, validated, and entered into a database. Species‐specific Maxent species distribution models (SDMs) based on 11 bioclimatic variables from the WorldClim database were developed for the species. HadGEM2‐ES projections of bioclimatic variables in two contrasting representative concentration pathways (RCPs), RCP2.6 and RCP8.5, were used to quantify the changes in future potential species distribution. D. afromontana is mostly sensitive to temperature in the wettest month, and its potential geographical range is predicted to decrease (up to −63.7% at RCP8.5). Optimum conditions for D. camerooniana are low diurnal temperature range (6–8°C) and precipitation in the wettest season exceeding 750 mm. The extent of this species will also decrease, but not as drastically as that of D. afromontana. D. surculosa prefers high precipitation in the coldest months. Its potential habitat area is predicted to increase in the future and to expand toward the east.This study developed SDMs and estimated current and future (year 2050) potential distributions of the forest undergrowth Dracaena species. D. afromontana, naturally associated with mountainous plant communities, was the most sensitive to predicted climate warming. In contrast, D. surculosa was predicted to extend its geographical range, regardless of the climate change scenario.

Modeling the climate suitability of tea [Camellia sinensis(L.) O. Kuntze] in Sri Lanka in response to current and future climate change scenarios

Knowledge of potential distributions and habitat preferences of tea (Camellia sinensis) under current and future climate conditions are vital for policy makers and stakeholders to develop suitable adaptation measures to mitigate against any detrimental effects of climate change. Without broad awareness of climate suitability and potential changes in distributions of tea growing areas, efforts of expanding the productivity of tea would remain ineffective. This study aimed to model the climate suitability of tea in Sri Lanka in response to the current and future climate change scenarios using the correlative habitat suitability model MaxEnt. Three representative concentration pathways were used under MIROC5 and CCSM4 global climate models for the year 2050 and 2070. The MaxEnt model projected current habitat suitability for tea based on existing datasets with a mean AUC of 0.92. The TSS value with a mean 0.847 ± 0.007 signifies high accuracy of predicting suitability habitats while the maximum kappa value (k) of the current and future models was around 0.454, indicating the overall performance of the model was good. In relation to the current time, areas of 6090 km2 (9.3%), 5769 km2(8.8%), and 5086 km2 were projected as potential areas of having optimal, medium, and marginal climate suitability for tea, respectively. Results show that most of the optimal and medium suitability areas in the low elevation areas would be lost to a greater extent in comparison to the high elevation areas for all tested RCPs by 2050 and 2070 under both GCMs of MIROC5 and CCSM4. The comparison of the current and future distributions of suitable tea growing areas revealed a decline of approximately 10.5%, 17% and 8% in total 'optimal', 'medium', and 'marginal' suitability areas respectively, implying that climate would have a negative effect on the habitat suitability of tea in Sri Lanka by 2050 and 2070.

Spatiotemporal dynamics in habitat suitability of a large Arctic herbivore: Environmental heterogeneity is key to a sedentary lifestyle

Quantifying spatial and temporal variation in habitat suitability is crucial to understand changes in animal distribution and to inform conservation and management initiatives, especially for species occupying regions profoundly impacted by climatic and environmental change. A detailed understanding of the environmental conditions shaping seasonal habitat suitability of free-ranging muskoxen (Ovibos moschatus), a key species in the Arctic tundra ecosystem, is currently lacking. We applied the maximum entropy modelling algorithm (MaxEnt) to build seasonal species distribution models (SDMs) over four years to quantify variation in habitat suitability in time and space. Suitable habitat was predicted based on location data from 27 GPS-collared adult female muskoxen in northeast Greenland and the spatial distribution of topographic variables and landcover within the study area. Overall, our results highlight distinct seasonal differences in both the spatial extent and distribution of suitable muskox habitat. Suitable space was smallest and spatially most clustered during autumn, and increased in extent and dispersion throughout the snow-covered period until peaking in summer. Nonetheless, the importance of environmental variables influencing habitat suitability was consistent across inter-annual and seasonal scales as habitat suitability was consistently predicted to be highest in vegetated, flat to moderately rugged terrain at low to medium elevation (<500–600 m.a.s.l.) close to the coast (<5–10 km). One year with extraordinary large amounts of snow differed from the general pattern, exhibiting markedly smaller areas of suitable habitat and higher spatial clustering. The results support the notion that adult female muskoxen are able to lead a relatively sedentary lifestyle due to the close proximity of suitable habitats across all seasons. However, above-average snow depths appear to be a potential bottleneck limiting access to suitable habitat, with consequences even beyond the snow-covered season. Our study provides the foundation for assessing potential future changes in habitat suitability and distribution of this key Arctic herbivore.

Climate change and tree harvest interact to affect future tree species distribution changes

Abstract Tree harvest and climate change can interact to have synergistic effects on tree species distribution changes. However, few studies have investigated the interactive effects of tree harvest and climate change on tree species distributions. We assessed the interactive effects of tree harvest and climate change on the distribution of 29 dominant tree species at 270 m resolution in the southern United States, while accounting for species demography, competition, urban growth and natural fire. We simulated tree species distribution changes to year 2100 using a coupled forest dynamic model (LANDIS PRO), ecosystem process model (LINKAGES) and urban growth model (SLEUTH). The distributions of 20 tree species contracted and nine species expanded within the region under climate change by end of 21st century. Distribution changes for all tree species were very slow and lagged behind the changes in potential distributions that were in equilibrium with new climatic conditions. Tree harvest and climate change interacted to affect species occurrences and colonization but not extinction. Occurrence and colonization were mainly affected by tree harvest and its interaction with climate change while extinctions were mainly affected by tree harvest and climate change. Synthesis and applications. Interactive effects of climate and tree harvest acted in the same direction as climate change effects on species occurrences, thereby accelerating climate change induced contraction or expansion of distributions. The overall interactive effects on species colonization were negative, specifically with positive interactive effects at leading edges of species ranges and negative interactive effects at trailing edges. Tree harvest generally did not interact with climate change to greatly facilitate or ameliorate species extinction. Our modelling results highlight the importance of considering disturbances and species demography (e.g. post‐harvest regeneration dynamics) when predicting changes in tree distributions.

Analysis of the influence of dynamic components of AC/DC system on transient voltage stability based on energy function method

With the interconnection of large power networks, transient voltage stability of AC/DC power systems has been paid more attention in recent years. To investigate main influence of generating facility, high-voltage direct current (HVDC) and motor load for transient voltage stability, from the perspective of the generalised branch potential energy, the new indexes, and analysis method is proposed here. First, an energy function for AC/DC system is constructed with major dynamic components, namely classical HVDC control systems and motors in third-order model. Accordingly, the influence effects of the above major dynamic elements are investigated based on indexes from the corresponding generalised branch potential energy. With the rule of change in transient potential energy distribution in the network and information in stability margins, an evaluating procedure is established. Here, the judgment of transient voltage stability employs a heuristic energy function method. Finally, simulation tests on three-machine system with a HVDC transmission line are conducted in PSAT package, and the obtained results demonstrate the feasibility and effectiveness of the proposed method.

Stability of cationic and amphoteric derivatives of mannan from the yeast Candida albicans

Infection with Candida albicans can prove lethal in immuno-compromised patients. It is imperative to develop a vaccine against this common organism. The amphoteric derivatives of the mannan component of the Candida cell wall may present a prospective target for the development of such a vaccine; however, the radical processing by antigen-presenting cells of the immune system is not fully understood. In this work a set of tailor-made cationic and amphoteric derivatives of three different degrees of quaternization (DSQ 0.14–0.38) has been prepared by chemical modification of ultrasonically-treated mannan and three carboxymethylated mannan derivatives (DSCM 0.13–0.32). These were exposed to free-radical attack by OH, generated in situ by the Fenton reaction. Potential changes in composition, DSQ, and molar mass distribution due to free-radical degradation were monitored by elemental analysis, NMR and FTIR spectroscopies, and size exclusion chromatography. A protective effect of quaternization against OH degradation was found. Non-isothermal thermogravimetric analysis found that the thermal stability of this mannan was also improved by chemical modification.

Harvesting geo-spatial data on coastal fish assemblages through coordinated citizen science

In response to repeated complaints from recreational and commercial coastal fishermen about declining fishing opportunities in inner Danish waters, focus was directed to inshore fish stocks. However, without data targeting inshore areas, it was not possible to investigate potential changes in fish distribution or abundances, or their causes. As a first step, a voluntary catch registration system was initiated in 2002, in collaboration with locally organized recreational fishermen. Using citizen science as a methodology, scientists and the fishermen developed a protocol for data collection, which the fishermen then implemented. The aim was to establish regular monitoring of fish catches from gill net and fyke net fisheries in coastal waters around Denmark in order to provide data that could inform management. After three years, during which time recreational fishermen could use their own gear and fish where they normally fished, the data was evaluated. As a result, the fishing method was switched in 2005 to fixed gears and fixed positions, to enable comparison between areas, years and season. The project has been very successful in recruiting highly motivated fishermen, who register their entire catch regularly. The time-series of data spans more than a decade and covers over 16,000 instances of fishing. The data from this project are now being used to create coastal fish indicators for managers to assess environmental status at a regional scale. Here we present an analysis of a subset of the data on one species, the European flounder (Platichthys flesus), to illustrate how the spatial and seasonal coverage can be utilized further for investigation of coastal ecosystems and to inform management.

Nondestructive Degradation Evaluation for Organic Coated Steels By Surface Potential Measurement

Organic coatings have been widely used for most steel structures as a cost-effective way for corrosion protection and ornamental design. Various methods have been suggested in order to check a degree of corrosion of organic coated metals. For example, visual observation and gloss measurement are well known as typical evaluation methods for organic coated metals.In this study, the corrosion performance of organic coated steels exposed to corrosive environment was estimated by surface potential measurement. In this study, the corrosion behavior of organic coated steels exposed to corrosive environment was monitored by surface potential measurement. In addition, the change in surface potential distribution was compared with the result of electrochemical impedance measurement in 0.5 M NaCl solution after measuring the surface potential. Carbon steel of the size of 3cm x 5cm was used as a substrate, and the organic coated steel samples were prepared by spraying a clear acrylic lacquer coating. Wet-dry cyclic corrosion test was conducted by alternating the condition of adding 20μl droplet of 0.5M NaCl solution and drying at 293K and 40%RH. After several cycles, a part of the surface exposed to corrosive environment showed lower potential than the other area. As the corrosion proceed, the change area grew up and the surface potential further declined. The electrochemical impedance characteristics also changed with an increase of wet and dry cycle number. The change in surface potential corresponds to that in the impedance characteristics, indicating that the deterioration process of the coated steel can be monitored by the surface potential measurement from the stage of the coating film deterioration.