328 research outputs found

    Modeling of Wave Propagation in Inhomogeneous Media

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    Factors influencing the use of e-commerce by small enterprises in Nigeria

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    The aim of this paper is to assess the factors influencing the use of e-commerce by small enterprises in Nigeria. The study adopts a qualitative methodology which involves in-depth, semi-structured interviews and direct observation in order to derive answers to such questions as ‘why’ the system is adopted and ‘how’ the Nigeria economic conditions influence the system. The study suggests that the main factors which motivate the adoption of e-commerce by small businesses in Nigeria are market expansion and reduced market costs. The findings also indicate that increasing access to the Internet and changing lifestyle enable the success of e-commerce in Nigeria. The implications of the study are discussed

    Life cycle assessment of marine coatings applied to ship hulls

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    This paper presents the methodology developed for Life Cycle Assessment (LCA) of antifouling marine coatings with regards to fouling accumulation on hulls and maintenance of ships. The methodology is based on mathematical models vis-à-vis the environmental and monetary impacts involved in the production and application of hull coatings, added fuel consumption due to fouling accumulation on ship hulls, and hull maintenance. This subject was investigated in a recently completed EU-Funded FP7 Project entitled FOUL-X-SPEL. The LCA methodology was developed using the results of the studies conducted by FOUL-X-SPEL Consortium as well as additional data provided by coating manufacturers, shipyards and shipping companies. Following the introduction of the new LCA model, a case study was carried out to show how to utilize the model using a real tanker which is assumed to be coated with 2 different types of existing coatings, namely a silicone-based fouling release coating and a tin free self-polishing antifouling paint. The total costs and emissions due to the use of different coating types were calculated for the whole life-cycle of the ship. It has been found that CO2 emission reduction due to mitigation of fouling can be achieved using a silicone-based fouling release coating while reducing the cost by means of fuel cost reductions for the shipowners despite the additional capital expenses. The developed LCA model can help stake-holders determine the most feasible paint selection as well as the optimal hull-propeller maintenance schedules and make condition based maintenance decisions

    Secondary forest within a timber plantation concession in Borneo contributes to a diverse mammal assemblage

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    Commercial tree plantations of fast-growing species have become increasingly important in Southeast Asia to meet global demand for wood and wood fiber products. There is a growing need to understand more about their value for wildlife and how they can be managed for biodiversity. We evaluated the effects of landscape attributes on mammal communities in a timber concession consisting of 83 % secondary forest and 17 % tree plantations in northern Sabah, Malaysia. Using camera traps, we compared mammalian species assemblages of secondary forest and commercial tree plantation stands and identified habitat predictors associated with total mammal species detections and species richness in the landscape mosaic. We used 87 camera stations deployed for 23 days across two major land-use types: 62 sites in secondary forest (previously logged natural forest) and 25 sites in tree plantations. We evaluated variation in species richness in these two major land-use categories and assessed the effects of natural and anthropogenic predictors on variation in total mammal detections and species richness. We detected at least 23 large and medium-sized mammal species over 2035 trap nights. Fourteen of those species were classified as threatened or near-threatened by the International Union for the Conservation of Nature. Rarefaction did not reveal differences in mammal species richness or diversity between camera sites placed in tree plantations and secondary forests, likely because most camera sites in tree plantations were close to secondary forest and comprised < 30 % of all sites. However, generalized linear models indicated lower mammal diversity as proportions of tree plantation and proximity to human settlements increased. Total mammal records, including those of threatened mammals, increased with greater proportions of secondary forest. Retention of larger tracts of secondary forest around plantation areas appears to be important to maintain mammalian species richness and contributes to the conservation value of commercial timber plantations. These findings may assist in the management of mammals of conservation concern and implementation of adaptive management plans to enhance biodiversity conservation in commercial plantations

    Broadband acoustic invisibility and illusions

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    Rendering objects invisible to impinging acoustic waves (cloaking) and creating acoustic illusions (holography) has been attempted using active and passive approaches. While most passive methods are inflexible and applicable only to narrow frequency bands, active approaches attempt to respond dynamically, interfering with broadband incident or scattered wavefields by emitting secondary waves. Without prior knowledge of the primary wavefield, the signals for the secondary sources need to be estimated and adapted in real time. This has thus far impeded active cloaking and holography for broadband wavefields. We present experimental results of active acoustic cloaking and holography without prior knowledge of the wavefield so that objects remain invisible and illusions intact even for broadband moving sources. This opens previously inaccessible research directions and facilitates practical applications including architectural acoustics, education, and stealth

    Phase I study of Carzelesin (U-80,244) given (4-weekly) by intravenous bolus schedule

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    Carzelesin is a cyclopropylpyrroloindole analogue which acts as a DNA-sequence-specific alkylating agent. In this phase I study, Carzelesin was given as a 4-weekly 10 min IV infusion to 51 patients with advanced solid tumours. Patients received a median of two courses (range 1–5) at one of nine dose levels: 24, 48, 96, 130, 150, 170, 210, 250 and 300 μg m−2. According to NCI-CTC criteria, non-haematological toxicities (grade 1/2) included fever, nausea and vomiting, mucositis and anorexia, none of which was clearly dose related. The dose-limiting toxicity was haematological and consisted mainly of neutropenia and to a lesser extent thrombocytopenia. From the dose level 150 μg m−2, the haematological toxicity (particularly thrombocytopenia) was delayed in onset, prolonged and cumulative in some patients. In several courses, double WBC nadirs occurred. The maximum tolerated dose for a single course was 300 μg m−2. From the dose level 170 μg m−2, the intended dose intensity could not be delivered to most patients receiving > 2 courses owing to cumulative haematological toxicity. The dose level with the best dose intensity for multiple courses was 150 μg m−2. The pharmacokinetics of Carzelesin and its metabolites (U-76,073; U-76,074) have been established in 31 patients during the first course of treatment using a HPLC method. Carzelesin exhibited linear pharmacokinetics. The concentration of U-76,074 (active metabolite) extended above the lower limit of quantitation (1 ng ml−1) for short periods of time and only at the higher dose levels. There was no relationship between neutropenia and the AUC of the prodrug Carzelesin, but the presence of detectable plasma levels of the active metabolite U-76,074 was usually associated with a substantial decrease in ANC values. © 1999 Cancer Research Campaig
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