Investigations on valence-change behaviors of europium ions in Eu-doped aluminate and silicate phosphors

Compounds of Sr3Al2O6: Eu, Sr4Al14O25: Eu, and BaZnSiO4: Eu were synthesized by high-temperature solid state reactions. The doping Eu3+ ions were partially reduced to Eu2+ in Sr4Al14O25: Eu and BaZnSiO4: Eu prepared in an oxidizing atmosphere, N-2 + O-2. However, such an abnormal reduction process could not be performed in Sr3Al2O6: Eu, which was also prepared in an atmosphere of N-2 + O-2. Moreover, even though Sr3Al2O6: Eu was synthesized in a reducing condition CO, only part of the Eu3+ ions was reduced to Eu2+. The existence of trivalent and divalent europium ions was confirmed by photoluminescent spectra. The different valence-change behaviors of europium ions in the hosts were attributed to the difference in host crystal structures. The higher the crystal structure stiffness, the easier the reduction process from Eu3+ to Eu2+.

Structure and residual stress in gamma-LiAlO2, layer fabricated by vapor transport equilibration on (0001)sapphire

gamma-LiAlO2 layers with a highly preferred (1 0 0) orientation were prepared by vapor transport equilibration (VTE) technique on (0 0 0 1) sapphire substrate. Microststructure of the gamma-LiAlO2 layers was studied by XRD and SEM. In the temperature range from 750 to 1100 degrees C, the residual stress in the gamma-LiAlO2 layers varied from tensile to compressive with the increase of VTE temperature, and the critical point of the change between tensile and compressive stress is around 975 degrees C. (c) 2005 Elsevier B.V. All rights reserved.

The structure and margins of the Lake Chilwa fisheries in Malawi: a value chain analysis

Small freshwater pelagic fisheries in closed lakes are very important to millions of people in sub-Saharan Africa providing livelihoods and nutritional security. However, returns from these fisheries have been shown to �uctuate in response to climatic variability. In order to understand the impact of these fluctuations on the livelihoods of people dependant on these fisheries, there is a need for information on how the fish value chain is organized and how it functions in response to variation in supplies. The results will feed into strategies that build resilience in fishing households against the uncertainties arising from unstable ecosystems. The Lake Chilwa fishery value chain is composed of fishers, processors, traders, fish transporters, boat owners, owners of fish processing shades, fisheries associations, gear owners, gear makers, firewood sellers, and traders of fishing gear and equipment. The value chain employs many people and local authorities can consider using this information in the design of rural development strategies for employment generation in small-scale fishing communities. The findings from this study have a number of implications for the improvement of the livelihood of fishers and enhancing their capacity to mitigate against the effects of climate change.

Change in Pacific Northwest coastal ecosystems. Proceedings of the Pacific Northwest Coastal Ecosystems Regional Study Workshop, August 73-14, 1996, Troutdale, Oregon

Over the past one hundred and fifty years, the landscape and ecosystems of the Pacific Northwest coastal region, already subject to many variable natural forces, have been profoundly affected by human activities. In virtually every coastal watershed from the Strait of Juan de Fuca to Cape Mendocino, settlement, exploitation and development of resou?-ces have altered natural ecosystems. Vast, complex forests that once covered the region have been largely replaced by tree plantations or converted to non-forest conditions. Narrow coastal valleys, once filled with wetlands and braided streams that tempered storm runoff and provided salmon habitat, were drained, filled, or have otherwise been altered to create land for agriculture and other uses. Tideflats and saltmarshes in both large and small estuaries were filled for industrial, commercial, and other urban uses. Many estuaries, including that of the Columbia River, have been channeled, deepened, and jettied to provide for safe, reliable navigation. The prodigious rainfall in the region, once buffered by dense vegetation and complex river and stream habitat, now surges down sirfiplified stream channels laden with increased burdens of sediment and debris. Although these and many other changes have occurred incrementally over time and in widely separated areas, their sum can now be seen to have significantly affected the natural productivity of the region and, as a consequence, changed the economic structure of its human communities. This activity has taken place in a region already shaped by many interacting and dynamic natural forces. Large-scale ocean circulation patterns, which vary over long time periods, determine the strength and location of currents along the coast, and thus affect conditions in the nearshore ocean and estuaries throughout the region. Periodic seasonal differences in the weather and ocean act on shorter time scales; winters are typically wet with storms from the southwest while summers tend to be dry with winds from the northwest. Some phenomena are episodic, such as El Nifio events, which alter weather, marine habitats, and the distribution and survival of marine organisms. Other oceanic and atmospheric changes operate more slowly; over time scales of decades, centuries, and longer. Episodic geologic events also punctuate the region, such as volcanic eruptions that discharge widespread blankets of ash, frequent minor earthquakes, and major subduction zone earthquakes each 300 to 500 years that release accumulated tectonic strain, dropping stretches of ocean shoreline, inundating estuaries and coastal valleys, and triggering landslides that reshape stream profiles. While these many natural processes have altered, sometimes dramatically, the Pacific Northwest coastal region, these same processes have formed productive marine and coastal ecosystems, and many of the species in these systems have adapted to the variable environmental conditions of the region to ensure their long-term survival.

Fish and habitat community assessments on North Carolina shipwrecks: potential sites for detecting climate change in the graveyard of the Atlantic

The Monitor National Marine Sanctuary (MNMS) was the nation’s first sanctuary, originally established in 1975 to protect the famous civil war ironclad shipwreck, the USS Monitor. Since 2008, sanctuary sponsored archeological research has branched out to include historically significant U-boats and World War II shipwrecks within the larger Graveyard of the Atlantic off the coast of North Carolina. These shipwrecks are not only important for their cultural value, but also as habitat for a wide diversity of fishes, invertebrates and algal species. Additionally, due to their unique location within an important area for biological productivity, the sanctuary and other culturally valuable shipwrecks within the Graveyard of the Atlantic are potential sites for examining community change. For this reason, from June 8-30, 2010, biological and ecological investigations were conducted at four World War II shipwrecks (Keshena, City of Atlanta, Dixie Arrow, EM Clark), as part of the MNMS 2010 Battle of the Atlantic (BOTA) research project. At each shipwreck site, fish community surveys were conducted and benthic photo-quadrats were collected to characterize the mobile conspicuous fish, smaller prey fish, and sessile invertebrate and algal communities. In addition, temperature sensors were placed at all four shipwrecks previously mentioned, as well as an additional shipwreck, the Manuela. The data, which establishes a baseline condition to use in future assessments, suggest strong differences in both the fish and benthic communities among the surveyed shipwrecks based on the oceanographic zone (depth). In order to establish these shipwrecks as sites for detecting community change it is suggested that a subset of locations across the shelf be selected and repeatedly sampled over time. In order to reduce variability within sites for both the benthic and fish communities, a significant number of surveys should be conducted at each location. This sampling strategy will account for the natural differences in community structure that exist across the shelf due to the oceanographic regime, and allow robust statistical analyses of community differences over time.

Quantifying seascape structure: extending terrestrial spatial pattern metrics to the marine realm

Spatial pattern metrics have routinely been applied to characterize and quantify structural features of terrestrial landscapes and have demonstrated great utility in landscape ecology and conservation planning. The important role of spatial structure in ecology and management is now commonly recognized, and recent advances in marine remote sensing technology have facilitated the application of spatial pattern metrics to the marine environment. However, it is not yet clear whether concepts, metrics, and statistical techniques developed for terrestrial ecosystems are relevant for marine species and seascapes. To address this gap in our knowledge, we reviewed, synthesized, and evaluated the utility and application of spatial pattern metrics in the marine science literature over the past 30 yr (1980 to 2010). In total, 23 studies characterized seascape structure, of which 17 quantified spatial patterns using a 2-dimensional patch-mosaic model and 5 used a continuously varying 3-dimensional surface model. Most seascape studies followed terrestrial-based studies in their search for ecological patterns and applied or modified existing metrics. Only 1 truly unique metric was found (hydrodynamic aperture applied to Pacific atolls). While there are still relatively few studies using spatial pattern metrics in the marine environment, they have suffered from similar misuse as reported for terrestrial studies, such as the lack of a priori considerations or the problem of collinearity between metrics. Spatial pattern metrics offer great potential for ecological research and environmental management in marine systems, and future studies should focus on (1) the dynamic boundary between the land and sea; (2) quantifying 3-dimensional spatial patterns; and (3) assessing and monitoring seascape change.

A zero-stiffness elastic shell structure

A remarkable shell structure is described that, due to a particular combination of geometry and initial stress, has zero stiffness for any finite deformation along a twisting path; the shell is in a neutrally stable state of equilibrium. Initially the shell is straight in a longitudinal direction, but has a constant, nonzero curvature in the transverse direction. If residual stresses are induced in the shell by, for example, plastic deformation, to leave a particular resultant bending moment, then an analytical inextensional model of the shell shows it to have no change in energy along a path of twisted configurations. Real shells become closer to the inextensional idealization as their thickness is decreased; experimental thin-shell models have confirmed the neutrally stable configurations predicted by the inextensional theory. A simple model is described that shows that the resultant bending moment that leads to zero stiffness gives the shell a hidden symmetry, which explains this remarkable property.

Interdecadal variability in the spatial structure of wind and SST in the California Current system

The physical environment of eastern boundary current systems is rarely uniform in time. ENSO and other perturbations produce profound anomalies in the atmosphere and ocean on interannual to decadal and century time scales. ... The objective of this paper is to describe the temporal variability in the spatial texture of the California Current system, a major eastern boundary current system off the west coast of North America, to provide a base from which to evaluate the effect of climate change - in the recent past, at present, and for the future.

The characteristics of distribution and change of the seawater temperature and salinity of Cai river estuary and Northern Part of Nha Trang bay in the dry and rainy season

In this paper, some results of analyzing the hydrographic characteristics of the seawater temperature and salinity are presented. The received results showed that: in dry season, the influence of the Cai river water has is limited in Cai river estuary with the approximate transferable distance from the river mouth to the open sea of about 1 km. The isohaline 32%o could be defined as the separate boundary of the Cai river water; In rainy season, due to the river water discharges are high, the influence of Cai river water could be transferred to the open sea and island areas. The immerge of the Cai river water in the open sea areas in rainy season has changed the vertical structure of salinity and temperature in the northern part of Nhatrang bay. In both seasons, the Cai river water have influenced in the surface water layers 0 - 2m and the water layers deeper than 2m are influenced by the sea waters with the salinity of higher than 32%o.

A matrix-calculation-based algorithm for numerical change propagation analysis

Engineering changes (ECs) are raised throughout the lifecycle of engineering products. A single change to one component produces knock-on effects on others necessitating additional changes. This change propagation significantly affects the development time and cost and determines the product's success. Predicting and managing such ECs is, thus, essential to companies. Some prediction tools model change propagation by algorithms, whereof a subgroup is numerical. Current numerical change propagation algorithms either do not account for the exclusion of cyclic propagation paths or are based on exhaustive searching methods. This paper presents a new matrix-calculation-based algorithm which can be applied directly to a numerical product model to analyze change propagation and support change prediction. The algorithm applies matrix multiplications on mutations of a given design structure matrix accounting for the exclusion of self-dependences and cyclic propagation paths and delivers the same results as the exhaustive search-based Trail Counting algorithm. Despite its factorial time complexity, the algorithm proves advantageous because of its straightforward matrix-based calculations which avoid exhaustive searching. Thereby, the algorithm can be implemented in established numerical programs such as Microsoft Excel which promise a wider application of the tools within and across companies along with better familiarity, usability, practicality, security, and robustness. © 1988-2012 IEEE.

Short-term effects of drawing water for connectivity of rivers and lakes on zooplankton community structure

During 28-29, September 2005, water was drawn from Hanjiang River and Houguan Lake to the Yangzi River via Sanjiao Lake and Nantaizi Lake in Wuhan in order to provide favorable conditions for ecosystem restoration. To evaluate the feasibility and validity of drawing water as a means of ecosystem restoration, zooplankton populations were studied 3 times (before, immediately after finishing and a month after drawing water) at seven locations from 27 Sept. 2005 to 2 Nov. 2005. Water quality in the lakes was mostly improved and zooplankton species richness decreased as soon as drawing water had finished but increased a month after drawing water. Zooplankton density and biomass was reduced in the lakes by drawing water but was increased at the entrance to Sanjiao Lake because of landform geometry change. Before drawing water, most species in Sanjiao Lake e.g., Brachionus sp. and Keratella sp. were tolerant of contamination. After drawing water oligotrophic-prone species such as Lecane ludwigii and Gastropus stylifer emerged. We conclude that drawing water could be important for improving water quality and favour ecosystem restoration. Dilution of nutrient concentrations may be an important role in the effect.

Thermal annealing effect on the nanomechanical properties and structure of P3HT:PCBM thin films

Nanostructured polymer-fullerene thin films are among the most prominent materials for application in high efficient polymer solar cells. Specifically, poly(3-hexylthiophene) (P3HT) and fullerene derivatives (PCBM) blends are used as the donor/acceptor materials forming a bulk heterojunction. Although P3HT:PCBM properties have been extensively studied, less light has been set on its nanomechanical properties, which affect the device service life. In this work Atomic Force Acoustic Microscopy (AFAM), Atomic Force Spectroscopy and Nanoindentation were used to study the effect of the fullerene presence and the annealing on the P3HT:PCBM nanomechanical behavior. The P3HT:PCBM thin films were prepared by spin coating on glass substrates and then annealed at 100 °C and 145 °C for 30 min. Large phase separation was identified by optical and Atomic Force Microscopy (AFM) for the annealed samples. Needle-like PCBM crystals were formed and an increase of the polymer crystallinity degree with the increase of the annealing temperature was confirmed by X-ray diffraction. AFAM characterization revealed the presence of aggregates close to stiff PCBM crystals, possibly consisting of amorphous P3HT material. AFM force-distance curves showed a continuous change in stiffness in the vicinity of the PCBM crystals, due to the PCBM depletion near its crystals, and the AFM indentation provided qualitative results about the changes in P3HT nanomechanical response after annealing. © 2011 Elsevier B.V. All rights reserved.

Effects of seasonal succession and water pollution on the protozoan community structure in an eutrophic lake

The purpose of the research is to study the seasonal succession of protozoa community and the effect of water quality on the protozoa community to characterize biochemical processes occurring at a eutrophic Lake Donghu, a large shallow lake in Wuhan City, China. Samples of protozoa communities were obtained monthly at three stations by PFU (polyurethane foam unit) method over a year. Synchronously, water samples also were taken from the stations for the water chemical quality analysis. Six major variables were examined in a principal component analysis (PCA), which indicate the fast changes of water quality in this station I and less within-year variation and a comparatively stable water quality in stations II and III. The community data were analyzed using multivariate techniques, and we show that clusters are rather mixed and poorly separated, suggesting that the community structure is changing gradually, giving a slight merging of clusters form the summer to the autumn and the autumn to the winter. Canonical correspondence analysis (CCA) was used to infer the relationship between water quality variables and phytoplankton community structure, which changed substantially over the survey period. From the analysis of cluster and CCA, coupled by community pollution value (CPV), it is concluded that the key factors driving the change in protozoa community composition in Lake Donghu was water qualities rather than seasons. (c) 2006 Elsevier Ltd. All rights reserved.

Changes in the structure of a zooplankton community during a Ceratium (dinoflagellate) bloom in a eutrophic fishless pond

The community structure of zooplankton was studied in a eutrophic, fishless Japanese pond. The ecosystem was dominated by a dinoflagellate, Ceratium hirundinella, two filter-feeding cladocerans, Daphnia rosea and Ceriodaphnia reticulata, and an invertebrate predator, the dipteran Chaoborus flavicans. The midsummer zooplankton community showed a large change in species composition (the Daphnia population crashed) when a heavy Ceratium bloom occurred. It is shown that (i) the rapid density decline of D.rosea in mid-May was mainly caused by a shortage of edible phytoplankton, which was facilitated by the rapid increase in C.hirundinella abundance; (ii) the low density of D.rosea in June-July was considered to be mainly caused by the blooming of Ceratium hirundinella (which may inhibit the feeding process of D.rosea), while predation by C.flavicans larvae, the changing temperature, the interspecific competition and the scarcity of edible algae were not judged to be important; (iii) the high summer biomass of the planktonic C.flavicans larvae was maintained by the bloom of C.hirundinella, because >90% of the crop contents of C.flavicans larvae were C.hirundinella during this period. The present study indicates that the large-sized cells or colonies of phytoplankton are not only inedible by most cladocerans, but the selective effect of the blooming of these algae can also influence the composition and dominance of the zooplankton community, especially for the filter-feeding Cladocera, in a similar way as the selective predation by planktivorous fish. The large-sized phytoplankton can also be an important alternative food for ominivorous invertebrate predators such as Chaoborus larvae, and thus may affect the interactions between these predators and their zooplanktonic prey. In this way, such phytoplankton may play a very important role in regulating the dynamics of the aquatic food web, and become a driving force in shaping the community structure of zooplankton.