720 research outputs found

    THEORETICAL ANALYSIS OF A WET COOLING TOWER FOR FRESH WATER FROM PLUME AND ANALYZING AN INDUSTRIAL COOLING TOWER BASED ON RESULTS

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    A cooling tower is a heat rejection device which rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature. The stream of saturated exhaust air leaving the cooling tower called the plume is visible when water vapor it contains condenses in contact with cooler ambient air, like the saturated air in one's breath fogs on a cold day. Under certain conditions, the cooling tower plume may present fogging or icing hazards to its surroundings and gives some environmental problems. To find the solution for this problem a cooling tower has been analysed based on air flow rate through the tower and the cooling load to obtain fresh water yield by utilising plume from cooling tower top. The theoretical analysis gives the values of important parameters Theoretical analysis has been done on wet cooling tower by varying the water flow rate through which affect the performance of a cooling tower such as the cooling range, effectiveness, approach, fresh water yield etc. Then with the conditions of a trials from the analysis, the mass flow rate of water in the cooling tower was scaled up to match the mass flow rate of water in an industrial cooling tower. This helps in obtaining the mass flow rate of the air and fresh water yield through the industrial cooling tower

    Optical study of titanium dioxide thin films prepared by R.F. sputtering

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    Optical response of TiO2 layers, prepared by R.F. sputtering from TiO2 target, was studied as a function of target state, oxygen partial pressure and sputtering power. We have found that TiO2 layers deposited from a used target exhibit a high absorptance which decreases greatly when an oxygen partial pressure is introduced. Whereas an increase of sputtering power leads to an absorbent TiO2 matrix.Optical response of TiO2 layers, prepared by R.F. sputtering from TiO2 target, was studied as a function of target state, oxygen partial pressure and sputtering power. We have found that TiO2 layers deposited from a used target exhibit a high absorptance which decreases greatly when an oxygen partial pressure is introduced. Whereas an increase of sputtering power leads to an absorbent TiO2 matrix

    Genomewide Spatial Correspondence Between Nonsynonymous Divergence and Neutral Polymorphism Reveals Extensive Adaptation in Drosophila

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    The effect of recurrent selective sweeps is a spatially heterogeneous reduction in neutral polymorphism throughout the genome. The pattern of reduction depends on the selective advantage and recurrence rate of the sweeps. Because many adaptive substitutions responsible for these sweeps also contribute to nonsynonymous divergence, the spatial distribution of nonsynonymous divergence also reflects the distribution of adaptive substitutions. Thus, the spatial correspondence between neutral polymorphism and nonsynonymous divergence may be especially informative about the process of adaptation. Here we study this correspondence using genomewide polymorphism data from Drosophila simulans and the divergence between D. simulans and D. melanogaster. Focusing on highly recombining portions of the autosomes, at a spatial scale appropriate to the study of selective sweeps, we find that neutral polymorphism is both lower and, as measured by a new statistic QS, less homogeneous where nonsynonymous divergence is higher and that the spatial structure of this correlation is best explained by the action of strong recurrent selective sweeps. We introduce a method to infer, from the spatial correspondence between polymorphism and divergence, the rate and selective strength of adaptation. Our results independently confirm a high rate of adaptive substitution (∼1/3000 generations) and newly suggest that many adaptations are of surprisingly great selective effect (∼1%), reducing the effective population size by ∼15% even in highly recombining regions of the genome

    Characterization of antioxidants activity in a microfluidic channel

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    Antioxidant is the common designation for substances that have a potential action in the prevention of oxidative stress. The characterization of the reactivity of these substances has attracted the attention of many researchers, with the aim to establish correlations between the intake of antioxidants and health maintenance or to detect early stages of diseases associated with oxidative stress. The measurement of antioxidant capacity of physiological fluids (blood serum, saliva or urine) or foodstuff is currently performed by means of different methods, mostly based on spectrophotometric detection. Voltammetry has gained popularity in this context.[1] Whereas peak potentials are used to characterize the reactivity of the antioxidant, the peak currents (or the area under voltammograms) are used for the antioxidant capacity evaluation. Although voltammetric methods constitute one of the most effective means to monitor the antioxidant electron-transfer reactions, quantitative information is not directly obtained from voltammograms of antioxidants mixtures. The antioxidant capacity is usually evaluated by relative parameters defined towards a reference substance. The significance of this result is limited and cannot be translated in the effective protection degree provided by the antioxidant. In a recent work, we have proposed an analytical method for the evaluation of the reducing antioxidant capacity of antioxidants evaluated by electrolysis (RACE). [2] The oxidation of antioxidants is analyzed in large scale controlled potential electrolysis and its consumption is monitored at the anode by the current decrease. The monitored charge for the complete oxidation of active antioxidants provides a quantitative measure of their ability to eliminate a given reactive oxygen species, according to the selected potential used in the electrolysis. In order to transfer the RACE methodology to a sensor design, electrochemical microfluidic devices were built and tested. Experimental variables such as device geometry and flow rate were optimised in order to achieve a thin-layer regime in mass transport [3]. The chronoamperometric response of antioxidants was analyzed to evaluate its reducing power at selected potentials, according to the nature of the reactive oxygen species whose action is simulated. These results demonstrated the validity of the concept

    Exploring the length scales, timescales and chemistry of challenging materials (Part 1)

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    This themed issue explores the different length scales and timescales that determine the physics and chemistry of a variety of key materials, explored from the perspective of a wide range of disciplines, including physics, chemistry, materials science, Earth science and biochemistry. The topics discussed include catalysis, chemistry under extreme conditions, energy materials, amorphous and liquid structure, hybrid organic materials and biological materials. The issue is in two parts, with the present part exploring glassy and amorphous systems and materials at high pressure. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'

    Exploring the length scales, timescales and chemistry of challenging materials (Part 2)

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    This themed issue explores the different length and timescales that determine the physics and chemistry of a variety of key of materials, explored from the perspective of a wide range of disciplines, including physics, chemistry materials science, Earth science and biochemistry. The topics discussed include catalysis, chemistry under extreme conditions, energy materials, amorphous and liquid structure, hybrid organic materials and biological materials. The issue is in two parts, with this second set of contributions exploring hybrid organic materials, catalysis low-dimensional and graphitic materials, biological materials and naturally occurring, super-hard material as well as dynamic high pressure and new developments in imaging techniques pressure. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'

    Formas de uréia e doses de nitrogênio em cobertura na qualidade fisiológica de sementes de trigo.

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    A adubação nitrogenada, além de aumentar a produtividade, pode favorecer a qualidade fisiológica das sementes. O trigo no Paraná é geralmente cultivado após a cultura da soja, com isso a palha da soja e outros fatores do solo podem minimizar o efeito do nitrogênio no trigo. O objetivo do trabalho foi avaliar o efeito de doses de adubação nitrogenada em cobertura e de diferentes formas de ureia, na qualidade fisiológica de sementes de genótipos de trigo. Os experimentos foram conduzidos em Londrina e Ponta Grossa-PR. As áreas experimentais são manejadas no sistema de plantio direto com rotação de culturas, sendo a soja a cultura anterior. Foram avaliadas sementes de três genótipos de trigo (BRS 208, BRS Pardela e IWT 04008) cultivados sob quatro doses de nitrogênio em cobertura (0, 40, 80 e 120 kg ha-1), provenientes de três formas de ureia (convencional, com inibidor de urease e protegida). A adubação nitrogenada de cobertura foi realizada durante o estádio de perfilhamento, aos 20 dias após a emergência. Avaliou-se o teor de nitrogênio nas sementes, a massa de 1000 sementes, a germinação e o vigor (primeira contagem, frio, emergência, massa seca de plântulas, envelhecimento acelerado e condutividade elétrica). Os genótipos de trigo foram analisados conjuntamente para cada local. A linhagem IWT 04008 e a cultivar BRS Pardela apresentam sementes com qualidade fisiológica superior a cultivar BRS 208. Somente em Londrina, em consequência do acamamento, as doses de nitrogênio influenciaram negativamente a massa de 1000 grãos e a condutividade elétrica e, positivamente o teor de proteína. As formas de ureia e as doses de nitrogênio não alteram a qualidade fisiológica das sementes de diferentes genótipos de trigo
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