Página 4 dos resultados de 350 itens digitais encontrados em 0.179 segundos

Bilateral recurrent laryngeal neurectomy as a model for the study of idiopathic canine laryngeal paralysis.

Greenfield, C L; Alsup, J C; Hungerford, L L; McKiernan, B C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1997 EN
Relevância na Pesquisa
25.7%
The purposes of this study were to develop an experimental model of canine laryngeal paralysis that mimicked the naturally occurring disease and to document the upper airway changes produced, both clinically and with pulmonary function testing. Ten dogs had bilateral recurrent laryngeal neurectomy performed and were recovered from anesthesia. Tidal breathing flow-volume loop analysis and upper airway resistance measurements were taken before and after the development of clinical laryngeal paralysis while dogs breathed room air and after the individual administration of 2 respiratory stimulants. Clinical signs of laryngeal paralysis developed 38 days (median) following denervation. Although some variations were present, tidal breathing flow-volume loop analyses on room air, following denervation, were similar to those reported in naturally occurring cases. Upper airway resistance increased following denervation and was significantly increased with both respiratory stimulants. We concluded that bilateral recurrent laryngeal neurectomy resulted in clinical signs and respiratory changes similar to those of idiopathic canine laryngeal paralysis.

Competition between Reversible Aggregation and Loop Formation in Denatured Iso-1-cytochrome C†

Tzul, Franco O.; Kurchan, Eydiejo; Roder, Heinrich; Bowler, Bruce E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 20/01/2009 EN
Relevância na Pesquisa
25.72%
The competition between intramolecular histidine-heme loop formation and ligand-mediated oligomer formation in the denatured state is investigated for two yeast iso-1-cytochrome c variants, AcH26I52 and AcA25H26I52. Besides the native His 18 heme ligand, both variants contain a single His at position 26. The AcA25H26I52 variant has Pro 25 mutated to Ala. The concentration dependence of the apparent pKa for His 26-heme binding in 3 M gdnHCl indicates that the P25A mutation disfavors oligomerization mediated by intermolecular heme ligation by 10-fold. Single and double pH jump stopped-flow experiments with the AcH26I52 variant show that fast phases for His-heme bond formation and breakage are due to intramolecular loop formation and slow phases for His-heme bond formation and breakage are due to intermolecular aggregation. The presence of two closely-spaced slow phases in the kinetics of loop formation for both variants suggests that intermolecular His 26-heme ligation results in both dimers and higher order aggregates. The P25A mutation slows formation and speeds breakdown of an initial dimer, demonstrating a strong effect of local sequence on aggregation. Analysis of the kinetic data yields equilibrium constants for intramolecular loop formation and intermolecular dimerization at pH 7.1 and indicates that the rate constant for intermolecular aggregation is very fast at this pH (107 to 108 M−1s−1). In light of the very fast rates of aggregation in the denatured state...

Detection of Mycobacterium tuberculosis by Using Loop-Mediated Isothermal Amplification Combined with a Lateral Flow Dipstick in Clinical Samples

Kaewphinit, Thongchai; Arunrut, Narong; Kiatpathomchai, Wansika; Santiwatanakul, Somchai; Jaratsing, Pornpun; Chansiri, Kosum
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
25.7%
Tuberculosis (TB) is a communicable disease caused by the bacterium Mycobacterium tuberculosis (MTB) and is a persistent problem in the developing countries. Loop-mediated isothermal amplification (LAMP) allows DNA to be amplified rapidly at a constant temperature. Here, a LAMP method was combined with a chromatographic lateral-flow dipstick (LFD) to detect IS6110 gene of M. tuberculosis specifically and rapidly. The reaction was optimized at 63°C for 60 min, and the amplified DNA hybridized to an FITC-labeled oligonucleotide probe for 5 min was detected at the LFD test line 5 min after application. Excluding the step of DNA extraction, the test results could be generated approximately within 1 h. In addition to the advantage of short assay time, this technique could avoid the contact of carcinogenic ethidium bromide due to the exclusion of the electrophoresis analysis step. Furthermore, the data indicated that LAMP-LFD could detect M. tuberculosis genomic DNA as little as 5 pg. The technique showed a significant specificity since no cross-hybridization to M. intracellulare (MIC), M. fortuitum (MFT), M. avium (MAV), M. kansasii (MKS), and M. gordonae (MGD) genomic DNAs was observed. In the clinical unknown samples test, the sensitivity of LAMP-LFD was 98.92 % and the specificity was 100 % compared to those of the standard culture assay. Based on its sensitivity...

Rapid and Sensitive Detection of Novel Avian-Origin Influenza A (H7N9) Virus by Reverse Transcription Loop-Mediated Isothermal Amplification Combined with a Lateral-Flow Device

Ge, Yiyue; Wu, Bin; Qi, Xian; Zhao, Kangchen; Guo, Xiling; Zhu, Yefei; Qi, Yuhua; Shi, Zhiyang; Zhou, Minghao; Wang, Hua; Cui, Lunbiao
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 01/08/2013 EN
Relevância na Pesquisa
25.7%
A severe disease in humans caused by a novel avian-origin influenza A (H7N9) virus emerged in China recently, which has caused at least 128 cases and 26 deaths. Rapid detection of the novel H7N9 virus is urgently needed to differentiate the disease from other infections, and to facilitate infection control as well as epidemiologic investigations. In this study, a reverse transcription loop-mediated isothermal amplification combined with a lateral flow device (RT-LAMP-LFD) assay to rapidly detect H7N9 virus was developed and evaluated. The RT-LAMP primers were designed to target the haemagglutinin (HA) and neuraminidase (NA) genes of H7N9 virus. Results of 10-fold dilution series assays showed that analysis of RT-LAMP products by the LFD method was as sensitive as real-time turbidity detection, and that the analytic sensitivities of the HA and NA RT-LAMP assays were both 10 copies of synthetic RNA. Furthermore, both the assays showed 100% clinical specificity for identification of H7N9 virus. The performance characteristics of the RT-LAMP-LFD assay were evaluated with 80 clinical specimens collected from suspected H7N9 patients. The NA RT-LAMP-LFD assay was more sensitive than real time RT-PCR assay. Compared with a combination of virus culture and real-time RT-PCR...

Molecular Characterization of Sudanese and Southern Sudanese Chicken Breeds Using mtDNA D-Loop

Wani, Charles E.; Yousif, Ibrahim A.; Ibrahim, Muntasir E.; Musa, Hassan H.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
25.71%
The objective of this study was to assess the genetic relationships and diversity and to estimate the amount of gene flow among the five chicken populations from Sudan and South Sudan and commercial strain of egg line White Leghorn chickens. The chicken populations were genotyped using mtDNA D-loop as a molecular marker. PCR product of the mtDNA D-loop segment was 600 bp and 14 haplotypes were identified. The neighbor-joining phylogenetic tree indicated that the indigenous Sudanese chickens can be grouped into two clades, IV and IIIa only. Median joining networks analysis showed that haplotype LBB49 has the highest frequency. The hierarchal analysis of molecular variance (AMOVA) showed that genetic variation within the population was 88.6% and the differentiation among the population was 11.4%. When the populations was redefined into two geographical zones, rich and poor Savanna, the results were fractioned into three genetic variations: between individuals within population 95.5%, between populations within the group 0.75%, and genetic variation between groups 3.75%. The pair wise Fst showed high genetic difference between Betwil populations and the rest with Fst ranging from 0.1492 to 0.2447. We found that there is large number of gene exchanges within the Sudanese indigenous chicken (Nm = 4.622).

The ‘Sphere’: A Dedicated Bifurcation Aneurysm Flow-Diverter Device

Peach, Thomas; Cornhill, J. Frederick; Nguyen, Anh; Riina, Howard; Ventikos, Yiannis
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
25.76%
We present flow-based results from the early stage design cycle, based on computational modeling, of a prototype flow-diverter device, known as the ‘Sphere’, intended to treat bifurcation aneurysms of the cerebral vasculature. The device is available in a range of diameters and geometries and is constructed from a single loop of NITINOL® wire. The ‘Sphere’ reduces aneurysm inflow by means of a high-density, patterned, elliptical surface that partially occludes the aneurysm neck. The device is secured in the healthy parent vessel by two armatures in the shape of open loops, resulting in negligible disruption of parent or daughter vessel flow. The device is virtually deployed in six anatomically accurate bifurcation aneurysms: three located at the Basilar tip and three located at the terminus bifurcation of the Internal Carotid artery (at the meeting of the middle cerebral and anterior cerebral arteries). Both steady state and transient flow simulations reveal that the device presents with a range of aneurysm inflow reductions, with mean flow reductions falling in the range of 30.6–71.8% across the different geometries. A significant difference is noted between steady state and transient simulations in one geometry, where a zone of flow recirculation is not captured in the steady state simulation. Across all six aneurysms...

Uma nova estratégia de controle baseado em modelo de perdas para melhoria de eficiência energética em motores de indução

Pelegrin, Jessé de
Fonte: Pato Branco Publicador: Pato Branco
Tipo: Dissertação de Mestrado
POR
Relevância na Pesquisa
25.74%
This paper develops a new method of controlling the drive energy efficiency of induction motors . This technique uses a model of losses and a control structure based on minimum energy consumption . At first , studies with the main drivers of energy efficiency in the last decade are presented . Then the electrical and mechanical models of three-phase induction motor are presented , from the classic model , with the reference axis qd0 . The controller used is an indirect field-oriented control (IFOC), composed of an outer control loop speed and flow , and an inner current control loop , showing a good performance of torque and speed. Because it is a IFOC controller, where the engine parameters are critical to obtain good results , the testing of induction motor is carried out and presented . Knowing the main sources of losses of the engine, the controller of energy efficiency can be drawn . The loss model based (LMC) controller is described , as well as the controller recursive search (SC), both widely used in the literature . The LMC proposed is implemented through optimum standard curves of flow based on power absorbed. Depending on the load on the motor shaft , a new standard curve is used . The proposed controller called efficiency ( MBC - Model Based Control ) uses the LMC method with a IFOC controller ...

Uma proposta de controle de paralelismo de inversores com a rede elétrica utilizando-se a técnica de realimentação de fase

Paiva, Élcio Precioso de
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
25.76%
Este trabalho apresenta um controlador de fluxos de potência ativa e reativa aplicado ao paralelismo de um inversor com a rede elétrica. Uma malha adicional de controle é inserida a um controlador convencional, o qual é baseado nas curvas características de potência ativa versus freqüência e potência reativa versus tensão. Essa malha utiliza a realimentação da própria variação da potência ativa para a geração do ângulo de carga da tensão de referência do inversor, quando o mesmo é conectado em paralelo com a rede elétrica. Como resultado as oscilações transitórias das potências ativa e reativa são melhor atenuadas, sem produzir efeitos colaterais indesejáveis tais como as variações de tensão e potência reativa presentes na utilização do PSS (Power System Stabilizer – Estabilizador de Sistemas de Potência), outra técnica usada para melhorar o amortecimento do sistema, [Martins, M. P., 2004]. Um modelo dinâmico do sistema baseado na análise para pequenos sinais é apresentado. Gráficos do lugar das raízes, mostrando os pólos do sistema diante de variações paramétricas também são apresentados, permitindo a análise de estabilidade do sistema. Resultados de simulação e resultados experimentais utilizando-se um protótipo de laboratório...

An alternative approach to identifying and appraising adaptive loops in complex organizations

Omarova, A.; Ireland, V.; Gorod, A.
Fonte: Elsevier; Netherlands Publicador: Elsevier; Netherlands
Tipo: Conference paper
Publicado em //2012 EN
Relevância na Pesquisa
25.73%
This paper describes a research into the adaptation property of complex organizations. The research is focused on the development of a methodology for identifying and appraising loops that can allow for organizational adaptation. The proposed methodology draws a parallel between the nature of adaptation in complex organizations and the process of adaptive decisionmaking in human behavior. From this perspective, the adaptive loop in complex organizations can be divided into four steps adapted from the OODA loop (Observe-Orient-Decide-Act). The extension of the OODA loop to an organizational scale is incorporated with an assumption that flow of information, involved in adaptation processes, can be formed by different organizational components. Subsequently, the OODA loop can be presented as a chain of actions created by independent components of both the organization and its environment. Applying this approach to complex organizations necessitates mapping a functional definition of different organizational components within each step of the adaptive loop. Thus, while the functional definition of an organization can be done by using existing tools of organizational analysis (organizational structure, functional decomposition, architecture frameworks...

Computational hemodynamics: Hemolysis and viscoelasticity

Arora, Dhruv
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
25.7%
Computational Fluids Dynamics (CFD) has emerged as a viable and reliable design tool for the analysis of blood-handling devices. The CFD-based design is simple, time- and cost-effective; the method predicts accurately the hydraulic performance of these devices. However, the CFD-based hematologic design is in its infancy. This thesis presents a holistic design approach for centrifugal blood pumps. The flow through the pump is simulated with a novel finite element method that accounts efficiently for deformable domains and moving parts while retaining desirable scalability on distributed-memory computers. The method is validated successfully against literature results in a benchmark problem of flow past a stirrer in a square cavity. Blood is treated as a Newtonian fluid in these initial simulations. However, blood is known to display shear-thinning and viscoelasticity; a generalized Newtonian model is employed to capture the shear-thinning blood viscosity, and the flow through the GYRO pump (Baylor College of Medicine) is simulated in typical operating conditions. The overall hydraulic performance predicted by the shear-thinning model show little difference compared to the Newtonian results. However, the shear-thinning model predicts smaller recirculation regions and higher values of wall shear stress. For simulating viscoelasticity...

Interactions of the platelet GP Ib-IX-V complex with immobilized von Willebrand factor under flow conditions

Schade, Alicia J.
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
25.74%
Platelets play key roles in physiology, such as the arrest of bleeding following vascular injury, and in pathology, such as mural arterial thrombosis. The initial step in both processes is platelet adhesion to von Willebrand factor. The adhesion molecule on the platelet surface responsible for this interaction is the platelet glycoprotein (GP) Ib-IX-V complex. This complex consists of four subunits, and the GP Ib a subunit contains the vWf binding site. The exact region or regions of GP Ib a that are involved in the GP Ib-IX-V -- vWf interaction are unknown. The purpose of this work was to investigate the importance of several structural domains of GP Ib a in the GP Ib-IX-V -- vWf interaction under high fluid shear stress. This was done by several methods which all used a parallel-plate flow chamber to create wall shear stress: an antibody blocking study of cell rolling, mutational analysis of four different domains of GP Ib a , and dog/human chimeras of GP Ib a . First, we evaluated the blocking effects of GP Ib a and vWf antibodies on rolling of CHO cells expressing the GP Ib-IX complex on immobilized vWf and then compared this data with the antibody blocking studies of modulator- and shear-induced platelet aggregation. Our results suggest that the mechanism of the GP Ib-IX-V -- vWf interaction in rolling is different than the mechanisms involved in shear- and modulator-induced platelet aggregation. Next...

Evaluation of a Stratified Multi-tank Thermal Storage for Solar Heating Applications

Cruickshank, CYNTHIA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 4505718 bytes; application/pdf
EN; EN
Relevância na Pesquisa
25.75%
A novel multi-tank thermal energy storage (TES) was evaluated experimentally and numerically. The multi-tank storage is based on the interconnection of standard hot water storage tanks by a single charge flow loop. Each tank is charged through a thermosyphon loop and natural convection heat exchanger (NCHE). Both series- and parallel-connected configurations were investigated and results show that high degrees of stratification can occur. To predict the performance of the series- and parallel-connected multi-tank TES, a numerical model was developed and implemented in the TRNSYS simulation environment. Laboratory tests were also conducted to measure the unit’s performance under charge conditions representative of combinations of clear and overcast days. The effects of rising and falling charge loop temperatures and power levels on storage temperatures and heat transfer rates were studied and indicated that sequential stratification was achieved in the series-connected storage. Under certain conditions, reverse flow through the thermosyphon loops was identified, leading to destratification and carry-over of heat to the downstream storage tanks. Consequently, a new model was developed and showed to model reverse thermosyphon operation. A subsequent analysis showed that these effects could be minimized by careful system design. To quantify the relative benefits of the sequentially stratified TES...

Efeito da razão de submersão sobre os parâmetros hidrodinâmicos de uma coluna de recirculação de líquido através de um tubo exterior

Vila Nova, Jorge Alfredo da Costa
Fonte: Instituto Politécnico do Porto. Instituto Superior de Engenharia do Porto Publicador: Instituto Politécnico do Porto. Instituto Superior de Engenharia do Porto
Tipo: Dissertação de Mestrado
Publicado em //2009 POR
Relevância na Pesquisa
25.73%
No trabalho realizado nesta tese, procedeu-se ao estudo hidrodinâmico de uma coluna de borbulhamento de recirculação externa do líquido (CREL), que permitiu ampliar o conhecimento já existente sobre este tipo de colunas. Para realizar este estudo utilizaram-se líquidos viscosos Newtonianos, nomeadamente soluções aquosas de glicerina com viscosidades entre 0,007 e 0,522 Pa.s. Para a gama de caudais de ar injectados, 1,5x10-5 até 1,35x10-4 m3/s, o ar ascendia ao longo da coluna de borbulhamento sob a forma de bolhas tubulares. Após a realização dos ensaios, verificou-se que o regime de escoamento do líquido entre bolhas tubulares variou desde o tipo laminar até transição (1,9

Analysis of pumping systems for the cooling of underground transmission lines

Kočí, Paul FrantiÅ¡ek; Glicksman, Leon R.; Rohsenow, Warren Max
Fonte: MIT Energy Lab Publicador: MIT Energy Lab
Tipo: Relatório Formato: 4918938 bytes; application/pdf
EN_US
Relevância na Pesquisa
25.73%
Various pumping arrangements and their pressure profile control for forced cooling of long pipe type transmission lines were investigated. In order to overcome the extensive friction head losses and provide ample cable cooling, a number of pump stations has to be used. Since the inner line segments cannot be provided with pressure control head tanks, line blockages, flow resistance changes, flow rate changes, pump shutdowns, or other imbalances in one segment can alter the pressure profile along the entire line, and, when two head tanks are used, create transverse flow. Using experimental and analytical methods, it was determined that the pump - relief valve combination operating as a constant flow source is superior to the pump - relief valve combination operating as a constant pressure source, and that the configuration consisting of an even number of loops, each loop having the opposite flow direction from its neighbor's, is the best solution when operated with only one pressure control head tank. The simplest, and yet effective, line pressure profile control appears to be the pump bypass, which could be easily implemented on existing installations. The head tank pressure adjustment, however, is the most effective line pressure profile control scheme...

Computation of eigenvalue sensitivity to base flow modifications in a discrete framework: Application to open-loop control

Mettot, Clément; Renac, Florent; Sipp, Denis
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/01/2014
Relevância na Pesquisa
25.71%
A fully discrete formalism is introduced to perform stability analysis of a turbulent compressible flow whom dynamics is modeled with the Reynolds-Averaged Navier-Stokes (RANS) equations. The discrete equations are linearized using finite differences and the Jacobian is computed using repeated evaluation of the residuals. Stability of the flow is assessed solving an eigenvalue problem. The sensitivity gradients which indicate regions of the flow where a passive control device could stabilize the unstable eigenvalues are defined within this fully discrete framework. Second order finite differences are applied to the discrete residual to compute the gradients. In particular, the sensitivity gradients are shown to be linked to the Hessian of the RANS equations. The introduced formalism and linearization method are generic: the code used to evaluate the residual of the RANS equations can be used in a black box manner, and the complex linearization of the Hessian is avoided. The method is tested on a two dimensional deep cavity case, the flow is turbulent with a Reynolds number equal to 860 000 and compressible with a Mach number of 0.8. Several turbulence models and numerical schemes are used to validate the method. Physical features of the flow are recovered...

The Potential of Synergistic Static, Dynamic and Speculative Loop Nest Optimizations for Automatic Parallelization

Baghdadi, Riyadh; Cohen, Albert; Bastoul, Cedric; Pouchet, Louis-Noel; Rauchwerger, Lawrence
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/11/2011
Relevância na Pesquisa
25.73%
Research in automatic parallelization of loop-centric programs started with static analysis, then broadened its arsenal to include dynamic inspection-execution and speculative execution, the best results involving hybrid static-dynamic schemes. Beyond the detection of parallelism in a sequential program, scalable parallelization on many-core processors involves hard and interesting parallelism adaptation and mapping challenges. These challenges include tailoring data locality to the memory hierarchy, structuring independent tasks hierarchically to exploit multiple levels of parallelism, tuning the synchronization grain, balancing the execution load, decoupling the execution into thread-level pipelines, and leveraging heterogeneous hardware with specialized accelerators. The polyhedral framework allows to model, construct and apply very complex loop nest transformations addressing most of the parallelism adaptation and mapping challenges. But apart from hardware-specific, back-end oriented transformations (if-conversion, trace scheduling, value prediction), loop nest optimization has essentially ignored dynamic and speculative techniques. Research in polyhedral compilation recently reached a significant milestone towards the support of dynamic...

Sensitivity and open-loop control of stochastic response in a noise amplifier flow: the backward-facing step

Boujo, Edouard; Gallaire, François
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/11/2014
Relevância na Pesquisa
25.71%
The two-dimensional backward-facing step flow is a canonical example of noise amplifier flow: global linear stability analysis predicts that it is stable, but perturbations can undergo large amplification in space and time as a result of non-normal effects. This amplification potential is best captured by optimal transient growth analysis, optimal harmonic forcing, or the response to sustained noise. In view of reducing disturbance amplification in these globally stable open flows, a variational technique is proposed to evaluate the sensitivity of stochastic amplification to steady control. Existing sensitivity methods are extended in two ways to achieve a realistic representation of incoming noise: (i) perturbations are time-stochastic rather than time-harmonic, (ii) perturbations are localised at the inlet rather than distributed in space. This allows for the identification of regions where small-amplitude control is the most effective, without actually computing any controlled flows. In particular, passive control by means of a small cylinder and active control by means of wall blowing/suction are analysed for Reynolds number $Re=500$ and step-to-outlet expansion ratio $\Gamma=0.5$. Sensitivity maps for noise amplification appear largely similar to sensitivity maps for optimal harmonic amplification at the most amplified frequency. This is observed at other values of $Re$ and $\Gamma$ too...

Frequency lock closed-loop control of a separated flow using visual feedback

Gautier, N.; Aider, J. -L.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/11/2013
Relevância na Pesquisa
25.74%
In this study, a simple model based closed-loop algorithm is used to control the separated flow downstream a backward-facing step. It has been shown in previous studies that the recirculation bubble can be minimized when exciting the shear layer at its natural Kelvin-Helmholtz instability frequency. In this experiment, the natural shedding frequency is identified through real-time analysis of 2D velocity fields. Actuation (pulsed jet) is then locked on this frequency. If flow characteristics stray too far from a set point, shedding frequency is updated and actuation changed. The present work demonstrates the efficacy and robustness of this approach in reducing recirculation while Reynolds number is randomly varied between 1400 and 2800.

Local Stability Analysis and Eigenvalue Sensitivity of Reacting, Bluff Body Wakes

Emerson, Benjamin; Lieuwen, Tim; Juniper, Matthew P.
Fonte: Cambridge University Press Publicador: Cambridge University Press
Tipo: Article; accepted version
EN
Relevância na Pesquisa
25.71%
This is the author accepted manuscript. It is currently embargoed pending publication.; This paper presents an experimental and theoretical investigation of high Reynolds number, low density reacting wakes near a hydrodynamic Hopf bifurcation. This configuration is applicable to the wake flows that are commonly used to stabilize flames in high velocity flows. First, an experimental study is conducted to measure the limit cycle oscillation of this reacting bluff body wake. The experiment is repeated while independently varying the bluff body lip velocity and the density ratio across the flame. In all cases, the wake exhibits a sinuous oscillation. Linear stability analysis is performed on the measured time-averaged velocity and density fields. In the first stage of this analysis, a local, spatio-temporal stability analysis is performed on the measured, time averaged velocity and density fields. The stability analysis results are compared to the experimental measurement, and demonstrate that the local stability analysis correctly captures the influence of the lip velocity and density ratio parameters on the sinuous mode. In the second stage of this analysis, the linear direct and adjoint global modes are estimated by combining the local results. The sensitivity of the eigenvalue to changes in intrinsic feedback mechanisms is found by combining the direct and adjoint global modes. This is referred to as the eigenvalue sensitivity throughout the paper for reasons of brevity. The predicted global mode frequency is consistently within 10 % of the measured value...

Mitochondrial DNA analysis of population structure in the Atlantic croaker, Micropogonias undulatus (Perciformes: Sciaenidae)

Lankford, Thomas E. Jr.; Targett, Timothy E.; Gaffney, Patrick M.
Fonte: United States. National Marine Fisheries Service. Publicador: United States. National Marine Fisheries Service.
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
25.72%
Publisher's PDF.; Genetic population struc- ture in Atlantic croaker ( Micropogonias undulatus Linnaeus) was examined by using the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis of mi- tochondrial DNA (mtDNA). Juvenile croaker from three U.S. Atlantic locali- ties (Delaware, North Carolina, and Florida) and one Gulf of Mexico local- ity (Louisiana) were screened to docu- ment the magnitude and spatial distri- bution of mtDNA variation in M. undulatus ; to evaluate the integrity of Cape Hatteras, North Carolina, as a genetic stock boundary; and to estimate levels of gene flow among Atlantic lo- calities to provide an improved basis for future decisions regarding coastwide management of this fishery resource. RFLP analysis of the ATPase 6 and D-loop mtDNA regions revealed a total of 15 composite haplotypes in 93 indi- viduals. Monte Carlo simulations re- vealed no geographic heterogeneity in mtDNA haplotype frequencies among Atlantic localities and no evidence that juveniles collected north and south of Cape Hatteras originated from sepa- rate gene pools (net sequence diver- gence=–0.002%). There was significant heterogeneity between Atlantic and Gulf of Mexico samples...