3,049 research outputs found

    Advancement of methods for passive acoustic monitoring : a framework for the study of deep-diving cetacean

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    Marine mammals face numerous anthropogenic threats, including fisheries interactions, ocean noise, ship strikes, and marine debris. Monitoring the negative impact on marine mammals through the assessment of population trends requires information about population size, spatiotemporal distribution, population structure, and animal behavior. Passive acoustic monitoring has become a viable method for gathering long-term data on highly mobile and notoriously cryptic marine mammals. However, passive acoustic monitoring still faces major challenges requiring further development of robust analysis tools, especially as it becomes increasingly used in applied conservation for long-term and large-scale studies of endangered or data deficient species such as sperm or beaked whales. Further challenges lie in the translation of animal presence into quantitative population density estimates since methods must control for variation in acoustic detectability of the target species, environmental factors, and for species-specific vocalization rates. The main contribution of this thesis is the advancement of the framework for long-term quantitative monitoring of cetacean species, applied to deep-divers like sperm and beaked whales. Fully-automated methods were developed and implemented to different populations of beaked whales in different conditions. This provided insight into generalization capabilities of these automatic techniques and best practices. However, implementing these tool kits is not always practical, and alternative methods for additional data processing were developed to expeditiously serve multiple purposes including annotation of individual sounds, evaluation of data in order to provide a highly dynamic technique, and classification for quantitative monitoring studies. This work also presents the longest time series of sperm whale presence using passive acoustic monitoring for over seven years in the Gulf of Mexico. Echolocation clicks were detected and discriminated from other sounds to understand the spatiotemporal distribution and structure of the population. A series of steps were implemented to provide adequate parameters and characteristics of the target population for density estimation using an echolocation click-based method. This allowed for the study of the Gulf of Mexico’s sperm whale population, providing significant progress towards the understanding of the population structure, distribution, and trends, in addition to potential long-term impacts of the well-known catastrophic Deepwater Horizon oil spill and other anthropogenic activities. The emergence of innovative approaches for detecting the presence of marine mammals and documenting human interactions can provide insight into ecosystem change. These species can be used as sentinels of ocean health to ensure the conservation of their marine environment into the next epoch.Els mamífers marins s'enfronten a nombroses amenaces antropogèniques, incloses les interaccions pesqueres, la contaminació acústica als oceans, les coalicions amb vaixells i els residus marins. El seguiment de l'impacte d’aquestes amenaces en els mamífers marins mitjançant l'avaluació de les tendències poblacionals requereix informació sobre la mida i l’estructura poblacional, la distribució espaciotemporal i el comportament dels animals. El seguiment amb sistemes d’acústica passiva s'ha convertit en un mètode viable per recollir dades a llarg termini de mamífers marins altament mòbils i críptics. Tanmateix, el seguiment acústic passiu encara ha d’afrontar reptes importants en el desenvolupament d'eines d'anàlisi robustes, especialment de cara al recent increment en el seu ús en la conservació aplicada a seguiments a llarg termini i a gran escala d'espècies en perill d'extinció o amb dades insuficients com ara el catxalot o els zífids. Altres reptes són traduir la presència d’animals a estimacions quantitatives de densitat poblacional, degut a que els mètodes han de controlar la variabilitat en la detecció acústica de les espècies en qüestió, els factors ambientals i les freqüències de vocalització específiques de cada espècie. La principal contribució d'aquesta tesi és l'avanç en els mètodes de seguiment quantitatiu a llarg termini de les espècies de cetacis, aplicat a espècies que viuen a grans profunditats com el catxalot i els zífids. Durant aquesta tesi, s’han desenvolupat i aplicat mètodes totalment automatitzats per detectar zífids de diferents poblacions i en diferents condicions. Aquests mètodes han proporcionat informació sobre la capacitat de generalització d'aquestes tècniques automàtiques i han permès fer recomanacions de bones pràctiques. Tanmateix, degut a que la implementació d’aquestes eines no és sempre pràctic, s’han desenvolupat mètodes per al processament de dades de forma expeditiva, que tenen diversos propòsits, que inclouen l’anotació de sons individuals, l’avaluació de dades per proporcionar una tècnica més dinàmica i la classificació per a estudis de seguiment quantitatiu. Aquest treball també presenta la sèrie temporal més llarga documentada de la presència de catxalots obtinguda mitjançant tècniques de seguiment acústic passiu durant més de set anys al Golf de Mèxic. S’han detectat i discriminat les senyals d'ecolocalització d'altres sons per tal de comprendre la distribució i l'estructura espaciotemporal d’aquesta població de catxalots. S’han implementat una sèrie de passos per proporcionar paràmetres i característiques de la població amb l’objectiu d'estimar la densitat mitjançant un mètode basat en senyals d’ecolocalització. Aquesta implementació ha permès l'estudi de la població de catxalots del Golf de Mèxic i ha suposat un progrés significatiu per la comprensió de l'estructura, la distribució i les tendències poblacionals, així com dels potencials impactes a llarg termini del catastròfic vessament de petroli de la plataforma Deepwater Horizon i altres activitats antropogèniques.Postprint (published version

    Effect of nutritional factors on the growth and production of biosurfactant by Pseudomonas aeruginosa strain 181

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    The growth and production of biosurfactant by P. seudomonas aeruginosa (181) was dependant on nutritional factors. Among the eleven carbon sources tested, glucose supported the maximum growth (0.25 g/L) with the highest biosurfactant yield and this was followed by glycerol. Glucose reduced the surface tension to 35.3 dyne/ cm and gave an E24 reading of 62.7%. Butanol gave the lowest growth and had no biosurfactant production. For the nitrogen sources tested, casamino acid supported a growth of 0.21 g/L which reduced the surface tension to 41.1 dyne/cm and gave an E24 reading of 56%. Soytone was assimilated similarly, with good growth and high biosurfactant production. Corn steep liquor gave the lowest growth and did not show any biosurfactant activity

    Shedding Light on Diatom Photonics by means of Digital Holography

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    Diatoms are among the dominant phytoplankters in the worl's ocean, and their external silica investments, resembling artificial photonics crystal, are expected to play an active role in light manipulation. Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside the cell cytoplasm, condition that is hardly accessible via standard microscopy. The full characterization of the propagated beam, in terms of quantitative phase and intensity, removed a long-standing ambiguity about the origin of the light. The data were discussed in the light of living cell behavior in response to their environment

    Catalysis of a 1,3-dipolar reaction by distorted DNA incorporating a heterobimetallic platinum(II) and copper(II) complex

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    A novel catalytic system based on covalently modified DNA is described. This catalyst promotes 1,3-dipolar reactions between azomethine ylides and maleimides. The catalytic system is based on the distortion of the double helix of DNA by means of the formation of Pt(II) adducts with guanine units. This distortion, similar to that generated in the interaction of DNA with platinum chemotherapeutic drugs, generates active sites that can accommodate N-metallated azomethine ylides. The proposed reaction mechanism, based on QM(DFT)/MM calculations, is compatible with thermally allowed concerted (but asynchronous) [pi4s + pi2s] mechanisms leading to the exclusive formation of racemic endo-cycloadducts.MINECO: Grants CTQ2013-45415-P, CTQ2016-80375-P MAT2013-46006-R, CTQ2016-81797-REDC and PCIN-2015-240 Gobierno Vasco / Eusko Jaurlaritza: Grants IT673-13 and PI-2013 57 European Commission: Grants ERC Starting-Grant St 209842 (MATRIX) and ERC PoC 713641 (ESSENS

    Transport of a dilute active suspension in pressure-driven channel flow

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    Confined suspensions of active particles show peculiar dynamics characterized by wall accumulation, as well as upstream swimming, centerline depletion and shear-trapping when a pressure-driven flow is imposed. We use theory and numerical simulations to investigate the effects of confinement and non-uniform shear on the dynamics of a dilute suspension of Brownian active swimmers by incorporating a detailed treatment of boundary conditions within a simple kinetic model where the configuration of the suspension is described using a conservation equation for the probability distribution function of particle positions and orientations, and where particle-particle and particle-wall hydrodynamic interactions are neglected. Based on this model, we first investigate the effects of confinement in the absence of flow, in which case the dynamics is governed by a swimming Peclet number, or ratio of the persistence length of particle trajectories over the channel width, and a second swimmer-specific parameter whose inverse measures the strength of propulsion. In the limit of weak and strong propulsion, asymptotic expressions for the full distribution function are derived. For finite propulsion, analytical expressions for the concentration and polarization profiles are also obtained using a truncated moment expansion of the distribution function. In agreement with experimental observations, the existence of a concentration/polarization boundary layer in wide channels is reported and characterized, suggesting that wall accumulation in active suspensions is primarily a kinematic effect which does not require hydrodynamic interactions. Next, we show that application of a pressure-driven Poiseuille flow leads to net upstream swimming of the particles relative to the flow, and an analytical expression for the mean upstream velocity is derived in the weak flow limit. In stronger imposed flows .....

    Active and Passive Acoustic Methods for In-situ Monitoring of the Ocean Status

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    Recent European strategic plans for the successful monitoring of the status of the ocean push on the development of an integrated observing system able to further link existing instruments and techniques with the aim to complement each other and answer open issues. A more intensive use of acoustic devices could contribute to the knowledge of oceanographic processes exploiting the characteristic of sound to travel in the ocean for a wide area than in the atmosphere. In this context, the installation of passive acoustic instruments, able to listen to ambient noise on fixed or mobile platforms, could contribute to provide information on sound budget and to enhance the monitoring capacity of meteorological phenomena also in the open ocean. Instead, the deployment of active acoustic instruments can be of benefit for monitoring biological activities through the analysis of backscatter data as well as for monitoring ocean waves

    Ultrasound cleaning of microfilters

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    The doctoral research abstracts. Vol:10 2016 / Institute of Graduate Studies, UiTM

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    Foreword: Congratulations to Institute of Graduate Studies on the continuous efforts to publish the 10th issue of the Doctoral Research Abstracts which showcases the research carried out in the various disciplines range from science and technology, business and administration to social science and humanities. This issue captures the novelty of research contributed by seventy (70) PhD graduands receiving their scrolls in the UiTM’s 85th Convocation. As of October 2016, this year UiTM has produced 138 PhD graduates soaring from125 in the previous year (2015). It shows that UiTM is in the positive direction to achive the total of 1200 PhD graduates in 2020. To the 70 doctorates, I would like it to be known that you have most certainly done UiTM proud by journeying through the scholarly world with its endless challenges and obstacles, and by persevering right till the very end. This convocation should not be regarded as the end of your highest scholarly achievement and contribution to the body of knowledge but rather as the beginning of embarking into more innovative research from knowledge gained during this academic journey, for the community and country. This year marks UiTM’s 60th Anniversary and we have been producing many good quality graduates that have a major impact on the socio-economic development of the country and the bumiputeras. As alumni of UiTM, we hold you dear to our hearts. We sincerely wish you all the best and may the Almighty guide you to a path of excellence and success. As you leave the university as alumni we hope a new relationship will be fostered between you and the faculty in soaring UiTM to greater heights. “UiTM Sentiasa di Hati Ku” / Prof Emeritus Dato’ Dr Hassan Said Vice Chancellor Universiti Teknologi MAR
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