5,806 research outputs found

    Phosphate Contaminant Detection in Water Through a Paper-based Microfluidic Device

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    This report describes a project aimed at developing a low-cost, portable, on-site, user-friendly system for detecting different concentrations of phosphate in drinking water. Phosphate is a natural chemical, but toxic in large concentrations; detection is therefore important to avoid drinking contaminated water. Despite this fact, no cheap, and/or nontoxic system for phosphate detection is yet on the market. The detection system utilizes a paper-based microfluidic device to automate the electrochemical detection process, which normally requires expert use of lab equipment. When combined with a portable potentiostat that works with a mobile app, the device will allow untrained users to determine if any source of drinking water contains unsafe levels of phosphate without equipment or training, and to communicate that information to a central database for further analysis. Those of any background, particularly in developing countries, will be able to maintain health and raise awareness about clean water. Microfluidic devices are useful tools for the detection of water contaminants, but there is a gap in technology for the detection of phosphate. Our phosphate detection system is a paper-based microfluidic device with an already-developed voltammetry device that automates the detection process so that any user can safely find phosphate in water. The system will provide a binary analysis about whether the water is safe to consume or not. Completion of the project provides a valuable tool to both average customers in developing countries and scientific researchers in determining the safety of drinking water

    Deriving N=2 S-dualities from Scaling for Product Gauge Groups

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    S-dualities in scale invariant N=2 supersymmetric field theories with product gauge groups are derived by embedding those theories in asymptotically free theories with higher rank gauge groups. S-duality transformations on the couplings of the scale invariant theory follow from the geometry of the embedding of the scale invariant theory in the Coulomb branch of the asymptotically free theory.Comment: 19 pages latex and 1 figure using psfig.sty. References adde

    Optimal production scheduling for dairy industries

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    In this work, a complete two-level framework for use in food and in particular dairy industries is proposed. The specific characteristics of the dairy industry have been taken into consideration, in terms of the behavior of food sales over time and the special requirements in the production phase. At the scheduling level, an MILP (Mixed Integer Linear Programming) model of the system was developed, using a continuous representation of time

    Purpose and potential for commodity exchanges in African economies:

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    This paper reviews the purpose and potential of commodity exchanges in Africa. Drawing from the existing literature and using indicative empirics, it examines the conditions that enable successful exchanges, highlights the special challenges to setting up exchanges in Africa, and reviews alternatives to domestic exchanges. We argue that many critical preconditions for the successful establishment of commodity exchanges in Africa remain binding in the short to medium term. The development of commodity exchanges in the region is impeded by the relatively small size of domestic commodity markets, the weak physical and communication infrastructure, a lack of supportive legal and regulatory environments, and the likelihood of policy interventions, particularly in the staple cereals market. Meanwhile, the demand for a domestic commodity exchange for export crops may be limited due to the availability of well-established exchanges abroad and functioning auction floors. The paper highlights three points: (a) efforts to launch exchanges in Africa should realistically assess whether basic conditions for success can be met, (b) if the pre-conditions cannot be met, the use of existing exchanges abroad or the development of regional exchanges may be more feasible than the establishment of national commodity exchanges, and (c) the goals of risk management and reduced transaction costs might be achieved more effectively by improving market fundamentals through investments in transportation, information services, or other financial institutions.commodity exchanges, Risk management, Market development,

    Synthesis, characterisation and olefin oligomerization over nickel, cobalt and zinc substituted synthetic mica montmorillonite

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    Nickel, cobalt and zinc were substituted for structural octahedral aluminium in SMM. X-ray diffraction, together with elemental analysis, confirmed that a 2: 1 layered aluminosilicate had been formed. The inclusion of these metals facilitated the crystallisation of the SMM structure in the synthesis process as was shown by their more well-defined X-ray diffraction patterns over unsubstituted SMM synthesized in this work. The 2: 1 layer spacings increased at nickel contents of 16 and 34wt%, indicating a more montmorillonite-like structure. Cobalt levels at 33wt% were seen to disrupt the basal spacing. The opposite effect was seen with zinc, where increased zinc loadings caused the 2: 1 layers to be drawn closer together. This was indicative of a more micalike structure

    Connectomic analysis of the input to the principal cells of the mammalian cerebral cortex

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    Optimal Hashing in External Memory

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    Hash tables are a ubiquitous class of dictionary data structures. However, standard hash table implementations do not translate well into the external memory model, because they do not incorporate locality for insertions. Iacono and Patrasu established an update/query tradeoff curve for external-hash tables: a hash table that performs insertions in O(lambda/B) amortized IOs requires Omega(log_lambda N) expected IOs for queries, where N is the number of items that can be stored in the data structure, B is the size of a memory transfer, M is the size of memory, and lambda is a tuning parameter. They provide a complicated hashing data structure, which we call the IP hash table, that meets this curve for lambda that is Omega(log log M + log_M N). In this paper, we present a simpler external-memory hash table, the Bundle of Arrays Hash Table (BOA), that is optimal for a narrower range of lambda. The simplicity of BOAs allows them to be readily modified to achieve the following results: - A new external-memory data structure, the Bundle of Trees Hash Table (BOT), that matches the performance of the IP hash table, while retaining some of the simplicity of the BOAs. - The Cache-Oblivious Bundle of Trees Hash Table (COBOT), the first cache-oblivious hash table. This data structure matches the optimality of BOTs and IP hash tables over the same range of lambda

    Introduction: 1707, 2014 and the constitutional imperative in Scotland’s national press and civil society

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    This essay provides an historical, cultural and institutional juxtaposition of the Scottish national press’ relationship to constitutional change, using the Union of 1707 and 2014 independence referendum as key markers of this relationship. It reviews the parallels between both historical events in the context of structural changes to Scottish civil society, and the role played by the media in both amplifying and facilitating these changes. Finally, the essay maps the work of a number of historical and literary scholars, media experts, civil society actors, and journalists who have contributed to the Scottish Affairs special issue, 1707 and 2014: The national press, civil society and constitutional identity in Scotland
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