Optimal Strouhal number for swimming animals

To evaluate the swimming performances of aquatic animals, an important dimensionless quantity is the Strouhal number, St = fA/U, with f the tail-beat frequency, A the peak-to-peak tail amplitude, and U the swimming velocity. Experiments with flapping foils have exhibited maximum propulsive efficiency in the interval 0.25 < St < 0.35 and it has been argued that animals likely evolved to swim in the same narrow interval. Using Lighthill's elongated-body theory to address undulatory propulsion, it is demonstrated here that the optimal Strouhal number increases from 0.15 to 0.8 for animals spanning from the largest cetaceans to the smallest tadpoles. To assess the validity of this model, the swimming kinematics of 53 different species of aquatic animals have been compiled from the literature and it shows that their Strouhal numbers are consistently near the predicted optimum.Comment: 21 pages, 6 figure

Photocatalytic, sonocatalytic and sonophotocatalytic degradation of Rhodamine B using ZnO/CNTs composites photocatalysts

A series of ZnO nanoparticles decorated on multi-walled carbon nanotubes (ZnO/CNTs composites) was synthesized using a facile sol method. The intrinsic characteristics of as-prepared nanocomposites were studied using a variety of techniques including powder X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET) surface area analyzer and X-ray photoelectron spectroscopy (XPS). Optical properties studied using UV–Vis diffuse reflectance spectroscopy confirmed that the absorbance of ZnO increased in the visible-light region with the incorporation of CNTs. In this study, degradation of Rhodamine B (RhB) as a dye pollutant was investigated in the presence of pristine ZnO nanoparticles and ZnO/CNTs composites using photocatalysis and sonocatalysis systems separately and simultaneously. The adsorption was found to be an essential factor in the degradation of the dye. The linear transform of the Langmuir isotherm curve was further used to determine the characteristic parameters for ZnO and ZCC-5 samples which were: maximum absorbable dye quantity and adsorption equilibrium constant. The natural sunlight and low power ultrasound were used as an irradiation source. The experimental kinetic data followed the pseudo-first order model in photocatalytic, sonocatalytic and sonophotocatalytic processes but the rate constant of sonophotocatalysis is higher than the sum of it at photocatalysis and sonocatalysis process. The sonophotocatalysis was always faster than the respective individual processes due to the more formation of reactive radicals as well as the increase of the active surface area of ZnO/CNTs photocatalyst. Chemical oxygen demand (COD) of textile wastewater was measured at regular intervals to evaluate the mineralization of wastewater

Comparable Ages for the Independent Origins of Electrogenesis in African and South American Weakly Electric Fishes

One of the most remarkable examples of convergent evolution among vertebrates is illustrated by the independent origins of an active electric sense in South American and African weakly electric fishes, the Gymnotiformes and Mormyroidea, respectively. These groups independently evolved similar complex systems for object localization and communication via the generation and reception of weak electric fields. While good estimates of divergence times are critical to understanding the temporal context for the evolution and diversification of these two groups, their respective ages have been difficult to estimate due to the absence of an informative fossil record, use of strict molecular clock models in previous studies, and/or incomplete taxonomic sampling. Here, we examine the timing of the origins of the Gymnotiformes and the Mormyroidea using complete mitogenome sequences and a parametric Bayesian method for divergence time reconstruction. Under two different fossil-based calibration methods, we estimated similar ages for the independent origins of the Mormyroidea and Gymnotiformes. Our absolute estimates for the origins of these groups either slightly postdate, or just predate, the final separation of Africa and South America by continental drift. The most recent common ancestor of the Mormyroidea and Gymnotiformes was found to be a non-electrogenic basal teleost living more than 85 millions years earlier. For both electric fish lineages, we also estimated similar intervals (16–19 or 22–26 million years, depending on calibration method) between the appearance of electroreception and the origin of myogenic electric organs, providing rough upper estimates for the time periods during which these complex electric organs evolved de novo from skeletal muscle precursors. The fact that the Gymnotiformes and Mormyroidea are of similar age enhances the comparative value of the weakly electric fish system for investigating pathways to evolutionary novelty, as well as the influences of key innovations in communication on the process of species radiation

Experimental and Analytical Study on the Longitudinal Shear Bond Behaviour of Basalt Textile-Reinforced Concrete Composite Slab

Composite deck slab flooring system is gaining popularity since they allow for simpler, lightweight, and more cost-effective building construction technique. The main constituent materials of a composite slab are profiled deck steel sheet and concrete. Profiled steel sheet serves two purposes: it acts as a main reinforcing structural element as well as a permanent formwork during the construction phase. The efficiency of the composite slab mainly depends upon the shear interaction between concrete and steel decking sheet. This paper contributes to improving the horizontal shear strength of composite slab by utilizing basalt textile reinforced concrete (BTRC) topping. The current research is focused on examining the behavior of this shear bond action and improving its performance even without the shear connectors. Three types of concrete topping and four different shear spans (250 mm, 325 mm, 550 mm, and 625 mm) are the variables of the testing. Based on the load-displacement response, failure mechanisms, maximum strain recorded in concrete/steel, load-slip characteristics, steel-concrete shear bond resistance, and the structural performances of basalt textile-reinforced concrete (BTRC) composite slabs were compared with the conventional concrete (CC) composite slabs. BTRC composite slabs are found to be more ductile than the conventional concrete composite slab, with increased load-bearing and slip resisting capacity. Both the m–k and partial shear connection (PSC) approaches were used to calculate the horizontal shear strength of the composite floor. The m-k technique has proven to be more meticulous than the PSC method

Acoustic cell filter: a proven cell retention technology for perfusion of animal cell cultures

NRC publication: Ye

Effect of sonication on crystal properties

Ultrasonic irradiation resulting in acoustic cavitation was employed during the partial crystallization of diphenyl oxide and dimethyl phenyl carbinol from their respective crude melts. The crystals obtained showed improved purity and better olefactory values for both compounds. This was confirmed by melting point measurements and image analysis of the crystals thus obtained. The beneficial effect of ultrasonic irradiation on the resultant properties is explained on the basis of the theory of acoustic cavitation