Temporal and frequency characteristics of distributed feedback dye lasers

Previous studies of distributed feedback dye lasers (DFDL's) have identified that the linewidth of the device scales, to a first approximation, with the level of pumping employed. A more recent development is that the DFDL can be used to produce single ultrashort pulses. To produce such pulses the main requirement is that the laser is operated close to its threshold. An apparent contradiction exists here since, by lowering the pump power to achieve narrow linewidth operation, the near threshold region must be avoided since pulsing operation acts to increase the linewidth (to at least the Fourier transform of the pulse duration). This thesis further investigates the mechanisms which contribute to the temporal and linewidth properties of the laser. It is identified that by judicious choice of operating conditions a regime exists where the DFDL may be operated with a linewidth approaching that of the transform limit for the nanosecond pulse durations involved. After introducing the different types of distributed feedback lasers the thesis first reviews previously understood DFDL behaviour. Different DFDL geometries are considered with a view to their particular temporal and linewidth properties. A strategy for the development of a narrow linewidth DFDL is presented. The experimental laser system is described detailing the operation and characteristics of the frequency doubled Q switched Nd:YAG pump laser and the two different DFDL geometries. A high resolution computer aided interferometry (CAIN) system is described which provided single shot linewidth measurements. This system was used extensively in the experiments reported. DFDL linewidth is seen to depend on the thermo-optical properties of the dye's host solvent and as such a full characterization of commonly used solvents is presented. The temporal behaviour of the laser is considered theoretically with the aid of a coupled rate equation model which describes the interplay between the population inversion and the cavity photon flux. The model is used to predict short (picosecond) and smooth (nanosecond) pulse operation of the laser. Finally, a description of and the results obtained from various experimental investigations into the DFDL are presented. Temporal analysis, using a streak camera, revealed that, as expected, under certain circumstances multiple pulsing of picosecond duration could occur. Different conditions however, lead to narrow linewidth (~100 MHz) operation. A description of the two operating regimes is presented and these are related to the particular parameters involved e.g. the grating length or the level of pumping employed

Inhibitory Effect of Extract Granule of Earthworms (Lumbricus Rubellus) on the Pathogenic Bacteria in Vitro

The objective of this study was to determine the inhibition ability of the earthworm (L. rubellus) extract (ECT), dried earthworm extract (ECT-k), and granule earthworm extract (ECT-g) as poultry feed additive against some pathogenic bacteria. Antibacterial activity was performed using diffusion method against Escherichia coli, Salmonella pullorum, Pseudomonas aeruginosa, and Staphylococcus aureus in vitro. In the present study, the concentrations of ECT, ECT-k, and ECT-g in nutrient broth (NB) media tested were consisted of treatments A: 0%, B: 0.26%, C: 0.52%, D: 0.78% and E: 1.04% (g/vol) respectively. The results of the in vitro study showed that started from ECT level 0.26% inhibited (P 0.05) of ECT and ECT-t against S. pullorum. Diameter of inhibition zone for 24 hours showed that S. aureus was the most sensitive bacterium to ECT and ECT-k, and S. pullorum was the most sensitive bacterium to ECT-g

A Fisheries Evaluation of the Westside Ditch and Wapato Canal Fish Screening Facilities, Spring 1989 : Annual Report.

We evaluated the effectiveness of new fish screening facilities in the Westside Ditch and Wapato Canal in south-central Washington State. The screen integrity tests indicated that test fish released in front of the screens could enter the canal behind the screens. At Westside Ditch, between 6% and 25% of the zero-age fry passed through the rotary drum screens. The 6% estimate is based on tests with rainbow trout Oncorhynchus mykiss fry. The 25% estimate is based on monitoring chinook salmon 0. tshawytscha fry that were diverted from the river into the irrigation ditch. At Westside Ditch, we estimated that 1.8% of steelhead 0. mykiss smolts and 0.3% of chinook salmon smolts released during tests were descaled. The time required for 50% of the test fish to exit from the Westside Ditch Screen forebay was 3 to 8 h for chinook salmon smolts and up to 28 h for steelhead smolts. Methods used in 1988 were first used at Sunnyside in 1985 and were used in subsequent years at Richland. Toppenish/Satus. Wapato. and Toppenish Creek. The methods and 1985 through 1987 results have been reviewed by the Washington State Department of Fisheries, U.S. Fish and Wildlife Service, National Marine Fisheries Service, Northwest Power Planning Council, and the Yakima Indian Nation

Andean Land Use And Biodiversity: Humanized Landscapes In A Time Of Change

Some landscapes Cannot be understood without reference., to the kinds. degrees, kinds, degrees, and history of human-caused modifications to the Earth's surface. The tropical latitudes of the Andes represent one such place, with agricultural land-use systems appearing in the Early Holocene. Current land use includes both intensive and extensive grazing and crop- or tree-based agricultural systems found across virtually the, entire range of possible elevations and humidity regimes. Biodiversity found in or adjacent to such humanized landscapes will have been altered in abundance. composition, and distribution in relation to the resiliency of the native Species to harvest, hold cover modifications, and other deliberate or inadvertent human land uses. In addition, the geometries of land cover, resulting flout difference among the shapes, sizes, connectivities, and physical structures of the patches, corridors, and matrices that compose landscape mosaics, will constrain biodiversity, often in predictable ways. This article proposes a conceptual model that alter ins that the Continued persistence of native species may depend as much oil the shifting Of Andean landscape mosaics as on species characteristics, themselves. Furthermore, mountains such as the Andes display long gradients of environmental Conditions that after in relation to latitude, soil moisture, aspect, and elevation. Global environmental change will shift these, especially temperature and humidity regimes along elevational gradients, causing Changes outside the historical range of variation for some species. Both land-use systems and Conservation efforts will need to respond spatially to these shifts in the future, at both landscape and regional scales.Geography and the Environmen

A Fisheries Evaluation of the Wapato, Sunnyside and Toppenish Creek Canal Fish Screening Facilities, Spring 1988 : Annual Report.

We evaluated the effectiveness of new screening facilities at the Toppenish Creek, Wapato, and Sunnyside canals in southcentral Washington State. Screen integrity tests indicated that fish released in front of the screens were prevented from entering the canal behind the screens. Screen efficiency estimates are 99% ({+-}0.6%) for Toppenish Creek, 99% ({+-}0.3%) for Wapato, and 98% ({+-}0.5%) for Sunnyside. During 1987 at the Wapato Canal, we estimated screen efficiency was 97% ({+-}l%). We conducted descaling tests at the Toppenish Creek Screens. We estimated that 0.2% of steelhead Qncorhynchus mykiss smelts released during tests were descaled. None of the fish released through the fish return pipe were descaled. We measured the time required for fish to move through the screen facilities. The time required for 50% of the test fish to exit the Toppenish Creek Screen forebay was 4 to 9 h for rainbow trout fry and up to 39 h for steelhead smelts. The time for 50% of the test fish to exit the Wapato and Sunnyside screen forebays was less than 8 h. As with past studies, exit times varied with canal flow and species. After 39 h at Toppenish Creek, half the steelhead smelts were still in the forebay when canal flows were 20 cfs. At Sunnyside, half the chinook salmon fry exited the forebay in 1 h or less. Methods used in 1988 were the same as those used at Sunnyside in 1985 and in subsequent years at Richland, Toppenish/Satus, and Wapato. The methods and previous results have been reviewed by the Washington State Department of Fisheries, U.S. Fish and Wildlife Service, National Marine Fisheries Service, Northwest Power Planning Council, and Yakima Indian Nation

Study on future UK demand and supply of lithium, nickel, cobalt, manganese and graphite for electric vehicle batteries

This report has been produced by the British Geological Survey (BGS) under the auspices of the Department for Business, Energy and Industrial Strategy (BEIS)-funded UK Critical Minerals Intelligence Centre (CMIC). It is the first output from CMIC, which aims to provide up to date, accurate, high resolution data and dynamic analysis on primary and secondary minerals resources, supply, stocks and flows of critical minerals, in the UK and globall

Aquatic community response to volcanic eruptions on the Ecuadorian Andean flank: evidence from the palaeoecological record

Aquatic ecosystems in the tropical Andes are under increasing pressure from human modification of the landscape (deforestation and dams) and climatic change (increase of extreme events and 1.5 °C on average temperatures are projected for AD 2100). However, the resilience of these ecosystems to perturbations is poorly understood. Here we use a multi-proxy palaeoecological approach to assess the response of aquatic ecosystems to a major mechanism for natural disturbance, volcanic ash deposition. Specifically, we present data from two Neotropical lakes located on the eastern Andean flank of Ecuador. Laguna Pindo (1°27.132′S–78°04.847′W) is a tectonically formed closed basin surrounded by a dense mid-elevation forest, whereas Laguna Baños (0°19.328′S–78°09.175′W) is a glacially formed lake with an inflow and outflow in high Andean Páramo grasslands. In each lake we examined the dynamics of chironomids and other aquatic and semi-aquatic organisms to explore the effect of thick (> 5 cm) volcanic deposits on the aquatic communities in these two systems with different catchment features. In both lakes past volcanic ash deposition was evident from four large tephras dated to c.850 cal year BP (Pindo), and 4600, 3600 and 1500 cal year BP (Baños). Examination of the chironomid and aquatic assemblages before and after the ash depositions revealed no shift in composition at Pindo, but a major change at Baños occurred after the last event around 1500 cal year BP. Chironomids at Baños changed from an assemblage dominated by Pseudochironomus and Polypedilum nubifer-type to Cricotopus/Paratrichocladius type-II, and such a dominance lasted for approximately 380 years. We suggest that, despite potential changes in the water chemistry, the major effect on the chironomid community resulted from the thickness of the tephra being deposited, which acted to shallow the water body beyond a depth threshold. Changes in the aquatic flora and fauna at the base of the trophic chain can promote cascade effects that may deteriorate the ecosystem, especially when already influenced by human activities, such as deforestation and dams, which is frequent in the high Andes

Germplasm Acquisition and Distribution by CGIAR Genebanks

The international collections of plant genetic resources for food and agriculture (PGRFA) hosted by 11 CGIAR Centers are important components of the United Nations Food and Agriculture Organization’s global system of conservation and use of PGRFA. They also play an important supportive role in realizing Target 2.5 of the Sustainable Development Goals. This paper analyzes CGIAR genebanks’ trends in acquiring and distributing PGRFA over the last 35 years, with a particular focus on the last decade. The paper highlights a number of factors influencing the Centers’ acquisition of new PGRFA to include in the international collections, including increased capacity to analyze gaps in those collections and precisely target new collecting missions, availability of financial resources, and the state of international and national access and benefit-sharing laws and phytosanitary regulations. Factors contributing to Centers’ distributions of PGRFA included the extent of accession-level information, users’ capacity to identify the materials they want, and policies. The genebanks’ rates of both acquisition and distribution increased over the last decade. The paper ends on a cautionary note concerning the potential of unresolved tensions regarding access and benefit sharing and digital genomic sequence information to undermine international cooperation to conserve and use PGRFA

Geological fate of seafloor massive sulphides at the TAG hydrothermal field (Mid-Atlantic Ridge)

Highlights • Generic geological model of hydrothermally extinct seafloor massive sulphide. • Sub-surface characterisation by combined drilling and geophysics. • New resource estimate for slow-spreading mid-ocean ridges. • Holistic approach to seafloor mineral deposits assessment. Abstract Deep-sea mineral deposits potentially represent vast metal resources that could make a major contribution to future global raw material supply. Increasing demand for these metals, many of which are required to enable a low-carbon and high-technology society and to relieve pressure on land-based resources, may result in deep sea mining within the next decade. Seafloor massive sulphide (SMS) deposits, containing abundant copper, zinc, gold and silver, have been the subject of recent and ongoing commercial interest. Although many seafloor hydrothermally systems have been studied, inactive SMS deposits are likely to more accessible to future mining and far more abundant, but are often obscured by pelagic sediment and hence difficult to locate. Furthermore, SMS deposits are three dimensional. Yet, to date, very few have been explored or sampled below the seafloor. Here, we describe the most comprehensive study to date of hydrothermally extinct seafloor massive sulphide deposits formed at a slow spreading ridge. Our approach involved two research cruises in the summer of 2016 to the TAG hydrothermal field at 26°N on the Mid-Atlantic Ridge. These expeditions mapped a number of hydrothermally extinct SMS deposits using an autonomous underwater vehicle and remotely operated vehicle, acquired a combination of geophysical data including sub-seafloor seismic reflection and refraction data from 25 ocean bottom instruments, and recovered core using a sub-seafloor drilling rig. Together, these results that have allowed us to construct a new generic model for extinct seafloor massive sulphide deposits that indicate the presence of up to five times more massive sulphide at and below the seafloor than was previously thought

2024 roadmap for sustainable batteries

Modern batteries are highly complex devices. The cells contain many components—which in turn all have many variations, both in terms of chemistry and physical properties. A few examples: the active materials making the electrodes are coated on current collectors using solvents, binders and additives; the multicomponent electrolyte, contains salts, solvents, and additives; the electrolyte can also be a solid ceramic, polymer or a glass material; batteries also contain a separator, which can be made of glass fibres, polymeric, ceramic, composite, etc. Moving up in scale all these components are assembled in cells of different formats and geometries, coin cells and Swagelok cells for funamental testing and understanding, and pouch, prismatic and cylindrical cells for application. Given this complexity dictated by so many components and variations, there is no wonder that addressing the crucial issue of true sustainability is an extremely challenging task. How can we make sure that each component is sustainable? How can the performance can be delivered using more sustainable battery components? What actions do we need to take to address battery sustainability properly? How do we actually qualify and quantify the sustainability in the best way possible? And perhaps most importantly; how can we all work—academia and battery industry together—to enable the latter to manufacture more sustainable batteries for a truly cleaner future? This Roadmap assembles views from experts from academia, industry, research institutes, and other organisations on how we could and should achieve a more sustainable battery future. The palette has many colours: it discusses the very definition of a sustainable battery, the need for diversification beyond lithium-ion batteries (LIBs), the importance of sustainability assessments, the threat of scarcity of raw materials and the possible impact on future manufacturing of LIBs, the possibility of more sustainable cells by electrode and electrolyte chemistries as well as manufacturing, the important role of new battery chemistries, the crucial role of AI and automation in the discovery of the truly sustainable batteries of the future and the importance of developimg a circular battery economy