77 research outputs found

    Length Effects of a Built-in Flapping Flat Plate on the Flow Over a Traveling Wavy Foil

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    Flow over the traveling wavy foil with a built-in rigid flapping plate at its trailing edge has been numerically studied using the multi-relaxation-time Lattice Boltzmann method and immersed boundary method. The effect of the plate length on the propulsive performance such as the thrust force, energy consumption, and propeller efficiency has been investigated. Three modes (body force dominated, body and tail force competing and tail force dominated modes) have been identified that are associated with different hydrodynamics and flow structures. It is revealed that there exists a better performance plate length region and, within this region, a high propeller efficiency (close to its maximum value) is achieved due to a great increase in propulsive force at a cost of a slight increase in energy consumption. Furthermore, a weak stabilizing effect on locomotion movement is indicated by the slight decrease in the root-mean-square (rms) values of drag and lateral forces. © 2014 American Physical Society

    Flow Over a Traveling Wavy Foil With a Passively Flapping Flat Plate

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    Flow over a traveling wavy foil with a passively flapping flat plate has been investigated using a multiblock lattice Boltzmann equation and the immersed boundary method. The foil undergoes prescribed undulations in the lateral direction and the rigid flat plate has passive motion determined by the fluid structure interaction. This simplified model is used to study the effect of the fish caudal fin and its flexibility on the locomotion of swimming animals. The flexibility of the caudal fin is modeled by a torsion spring acting about the pivot at the conjuncture of the wavy foil and the flat plate. The study reveals that the passively oscillating flat plate contributes half of the propulsive force. The flexibility, represented by the nondimensional natural frequency F, plays a very important role in the movement and propulsive force generation of the whole body. When the plate is too flexible, the drag force is observed. As the flat plate becomes more rigid, the propulsive force that is generated when the undulation is confined to last part of the wavy foil becomes larger. The steady movement occurs at F=5. These results are consistent with the observations of some swimming animals in nature. © 2012 American Physical Society

    A deformable plate interacting with a non-Newtonian fluid in three dimensions

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    We consider a deformable plate interacting with a non-Newtonian fluid flow in three dimensions as a simple model problem for fluid-structure-interaction phenomena in life sciences (e.g., red blood cell interacting with blood flow). A power-law function is used for the constitutive equation of the non-Newtonian fluid. The lattice Boltzmann equation (the D3Q19 model) is used for modeling the fluid flow. The immersed boundary (IB) method is used for modeling the flexible plate and handling the fluid-plate interaction. The plate drag and its scaling are studied; the influences of three dimensionless parameters (power-law exponent, bending modulus, and generalized Reynolds number) are investigated

    Constraining the denudation process in the eastern Sichuan Basin, China using low-temperature thermochronology and vitrinite reflectance data

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    The temperature history of samples and maximum palaeogeothermal profiles of boreholes were reconstructed based on low‐temperature thermochronology and vitrinite reflectance data, and the results provide limits for the timescale and amount of uplift–denudation of the eastern Sichuan Basin. The thermal history showed that the uplifting and cooling of eastern Sichuan Basin began around the Late Cretaceous (approximately 100–80 Ma). The region had experienced a continuous cooling process from the Late Cretaceous until the present, with the geothermal gradient decreasing from 32–36 °C/km to 20–23 °C/km. The amount of denudation at the Puguang region in north‐eastern Sichuan was approximately 2.3 km, whereas that at south‐eastern Sichuan was 1.9 km, and the erosion thickness in the eastern Sichuan fold belt that was revealed via the field samples is 2.3 ± 0.3–2.6 ± 0.3 km. The north‐eastern Sichuan experienced sustained cooling with inconspicuous fluctuations, whereas the thrust belt and the south‐eastern Sichuan Basin presented 2–4 stages with different cooling rates. It may indicate that the eastern Sichuan fold belt experienced a complex structural evolution, characterized by episodic upliftings and deformations since Late Cretaceous, while a different and gentle deformation took place in the northeastern Sichuan Basin

    Association of CLDN molecules with sleep apnea hypopnea syndrome: new biomarker candidates

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    IntroductionObstructive sleep apnea (OSA) is a common sleep-related breathing disorder, and has become a serious threat to public health. Intermittent hypoxia caused by OSA results in a low-grade inflammatory response that leads to impaired mucosal barrier function. Claudin (CLDN) molecules are important for the permeability of the mucosal epithelium. This study aimed to explore whether CLDN molecules can be a potential biomarker of OSA.MethodsA total of 37 healthy controls and 40 OSA patients underwent a physical assessment for OSA and filled out the STOP-Bang Questionnaire (SBQ) and Epworth Sleepiness Scale (ESS). Clinical specimens of plasma and urine were obtained to observe the difference between OSA patients and healthy controls and diagnostic accuracy of CLDN molecules for OSA.ResultsCLDN1, CLDN2, and CLDN3 molecules in plasma and urine decreased in OSA patients (both p < 0.05). The areas under the receiver operating characteristic curve (AUCs) of urinary CLDN1, plasma CLDN1, urinary CLDN2, plasma CLDN2, urinary CLDN3, and plasma CLDN3 were 0.887, 0.724, 0.779, 0.676, 0.828, and 0.665, respectively. The AUC of urinary CLDN1 + CLDN2 + CLDN3 was 0.906 (95% confidence interval (CI), 0.831–0.981). The AUC of plasma CLDN1 + CLDN2 + CLDN3 was 0.776 (95% CI, 0.645–0.878). The AUC of urinary CLDN3 + SBQ was 0.899 (95% CI, 0.832–0.967). The AUC of urinary CLDN3 + ESS was 0.896 (95% CI, 0.826–0.966). In addition, Urinary CLDN-3 was negative associated with the severity of OSA.ConclusionCLDN molecules are promising as useful biomarkers for OSA, which may be related to the impaired barrier function related to OSA

    Complete mitochondrial genome of Rhizosolenia setigera (Coscinodiscophyceae, Bacillariophyta)

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    Rhizosolenia is a species-rich genus with 144 described species, many of which are harmful algal species (HABs) with significant negative ecological impact. Despite their significance in primary production and their potential to induce HABs, genome data of these species remain extremely limited. In this study, the complete mitochondrial genome (mtDNA) of Rhizosolenia setigera Brightwell 1858 was determined for the first time, which also represented the first mtDNA of the order Rhizosoleniales. The circular mtDNA was 34,792 bp in length with GC content of 23.28%. It encoded 63 genes including 35 protein-coding genes (PCGs), 24 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and 2 conserved open reading frames (orfs). Phylogenetic analysis using concatenated PCGs revealed that R. setigera and Melosira undulate, which also belongs to the class Coscinodiscophyceae, clustered together as expected. However, comparison of these two mtDNAs revealed extensive genome rearrangement events, suggesting large evolutionary distance. The complete mtDNA of R. setigera will facilitate research on the phylogenetic relationship among Rhizosolenia species, which will in turn facilitate exploration of the evolutionary relationships in the class of Coscinodiscophyceae

    Complete mitochondrial genome of the harmful algal bloom species Thalassiosira nordenskioeldii (Mediophyceae, Bacillariophyta) from the east China sea

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    Thalassiosira nordenskioeldii is a common harmful algal bloom (HAB) species with worldwide distribution. Although barcode sequences of this ecologically important species have been published, no genome data have been published for T. nordenskioeldii. In this study, we constructed the complete mitochondrial genome (mtDNA) of a T. nordenskioeldii strain isolated from the East China Sea. The T. nordenskioeldii mtDNA is circular and has a length of 47,038 bp and a GC content of 30.84%. The mtDNA encodes 69 genes, including 40 protein-coding (PCGs), 27 tRNA and two rRNA genes. Phylogenetic analysis using concatenated amino acid sequences of 31 shared PCGs from 37 diatom mtDNAs revealed that the mtDNA of T. nordenskioeldii was fully resolved in a clade with that of Thalassiosira profunda. The mtDNA of T. nordenskioeldii showed high collinearity with those of T. profunda and Skeletonema marinoi with only minor rearrangements. The completion of Thalassiosira mtDNAs will facilitate evolutionary studies on species of the order Thalassiosirales and the class Mediophyceae
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