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Trailing Edge (trailing + edge)
Selected AbstractsA fluorescence energy transfer-based mechanical stress sensor for specific proteins in situFEBS JOURNAL, Issue 12 2008Fanjie Meng To measure mechanical stress in real time, we designed a fluorescence resonance energy transfer (FRET) cassette, denoted stFRET, which could be inserted into structural protein hosts. The probe was composed of a green fluorescence protein pair, Cerulean and Venus, linked with a stable ,-helix. We measured the FRET efficiency of the free cassette protein as a function of the length of the linker, the angles of the fluorophores, temperature and urea denaturation, and protease treatment. The linking helix was stable to 80 °C, unfolded in 8 m urea, and rapidly digested by proteases, but in all cases the fluorophores were unaffected. We modified the ,-helix linker by adding and subtracting residues to vary the angles and distance between the donor and acceptor, and assuming that the cassette was a rigid body, we calculated its geometry. We tested the strain sensitivity of stFRET by linking both ends to a rubber sheet subjected to equibiaxial stretch. FRET decreased proportionally to the substrate strain. The naked cassette expressed well in human embryonic kidney-293 cells and, surprisingly, was concentrated in the nucleus. However, when the cassette was located into host proteins such ,-actinin, nonerythrocyte spectrin and filamin A, the labeled hosts expressed well and distributed normally in cell lines such as 3T3, where they were stressed at the leading edge of migrating cells and relaxed at the trailing edge. When collagen-19 was labeled near its middle with stFRET, it expressed well in Caenorhabditis elegans, distributing similarly to hosts labeled with a terminal green fluorescent protein, and the worms behaved normally. [source] Wing wear, aerodynamics and flight energetics in bumblebees (Bombus terrestris): an experimental studyFUNCTIONAL ECOLOGY, Issue 4 2001A. Hedenström Summary 1,Previous work has shown that wing wear increases mortality rate in bumblebees. Two proximate explanations have been suggested to account for this: increased energy flight costs and increased predation risk due to reduced manoeuvrability. 2,Wing wear was mimicked by experimentally clipping the forewing distal trailing edge, causing a 10% wing area reduction. Experimental and sham control bumblebees were induced to hover in a flight respirometry chamber for measuring metabolic rate of hovering. Simultaneous video and sound recordings were taken for wingbeat kinematic data required for an aerodynamic analysis. 3,In the experimental group with reduced wing area we measured increased wingbeat frequency, lift coefficient and induced power, but a reduced profile power. The mechanical power output, assuming perfect elastic storage in the flight system, remained largely unchanged after the wing-trimming treatment. 4,Metabolic flight costs (CO2 production rate) did not increase significantly in the reduced wing area group, which is in line with the aerodynamic power output. 5,Our results indicate that an increase of flight cost due to wing wear is not a likely explanation for increased mortality rate in bumblebees. Wing wear may, however, affect escape performance from predators. [source] Sequence-specific termination by T7 RNA polymerase requires formation of paused conformation prior to the point of RNA releaseGENES TO CELLS, Issue 4 2001Hoseok Song Background The sequence-specific, hairpin-independent termination signal for the bacteriophage RNA polymerases in Escherichia coli rrnB t1 terminator consists of two modules. The upstream module includes the conserved sequence and the downstream one is U-rich. Results Elongation complexes of T7 RNA polymerase paused 2 bp before reaching the termination site at a 500 µm concentration of NTP. At 5,50 µm NTP, however, they paused and terminated there or resumed elongation beyond the termination site. Only at higher concentrations of NTP (500 µm), the pause complex proceeded slowly to and became incompetent at the termination site. At 4 bp or more before the termination site, the unprotected single-stranded region of transcription bubble shrank at the trailing edge to 4,5 bp from ,10 bp, resulting from duplex formation of the conserved sequence. The pause and bubble collapse were not observed with an inactive mutant of the termination signal. Conclusion Sequence-specific termination requires the slow elongation mode of paused conformation, working only at high concentrations of NTP for a few bp prior to the RNA release site. The collapse of bubble that was observed several base pairs before the termination site and/or the resulting duplex might subsequently lead to the paused conformation of T7 elongation complexes. [source] Role of lateral mantle flow in the evolution of subduction systems: insights from laboratory experimentsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2004Francesca Funiciello SUMMARY We present 3-D laboratory experiments constructed to investigate the pattern of mantle flow around a subducting slab under different boundary conditions. In particular we present a set of experiments, characterized by different conditions imposed at the trailing edge of the subducting plate (that is, plate fixed in the far field, plate detached in the far field, imposed plate motion). Experiments have been performed using a silicone slab floating inside a honey tank to simulate a thin viscous lithosphere subducting in a viscous mantle. For each set, we show differences between models that do or do not include the possibility of out-of-plane lateral flow in the mantle by varying the lateral boundary conditions. Our results illustrate how a subducting slab vertically confined over a 660-km equivalent depth can be influenced in its geometry and in its kinematics by the presence or absence of possible lateral pathways. On the basis of these results we show implications for natural subduction systems and we highlight the importance of suitable simulations of lateral viscosity variations to obtain a realistic simulation of the history of subduction. [source] Laminar separation bubble on an Eppler 61 airfoilINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2010Samir B. Savaliya Abstract Laminar separation bubble that occurs on the suction side of the Eppler 61 airfoil at Re=46000 is studied. The incompressible flow equations are solved using a stabilized finite element method. No turbulence model is used. The variation of the bubble length and its location, with the angle of attack (,), is studied in detail. An abrupt increase in the lift coefficient is observed at ,,4.5°. It is found to be related to a sudden decrease in the separation bubble length at the trailing edge of the airfoil. Significant differences are observed in the results from the 2D and 3D computations. Stall is observed in 3D simulations, but is found to be absent in 2D. The laminar bubble, which fails to reattach in 3D for ,>14°, continues to reattach for , as large as 20° in the 2D computations. Reynolds stress calculations in both 2D and 3D indicate the extent to which the outer flow is affected by the presence of bubble. It is found that the Reynolds stress components and are of comparable order of magnitude indicating that spanwise fluctuations are significant. The effect of the time window used to compute the time-averaged aerodynamic coefficients is studied. The time-averaged and root mean square (rms) value of the aerodynamic coefficients are calculated for both 2D and 3D computations and compared with the previously published experimental results. The 3D computations show good agreement with the earlier data. The variation of the rms value of the aerodynamic coefficients with angle of attack shows certain peaks. The cause of their appearance is investigated. The effect of Reynolds number is studied. The increase in Re at ,=10° is found to reduce the bubble length and cause it to move closer to the leading edge. Copyright © 2009 John Wiley & Sons, Ltd. [source] Vortex surface method: some numerical problems of the potential calculationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8 2001T. Belamri Abstract The singularities method is used to analyze the flow around an isolated profile or through a plane cascade. In this paper, a numerical study has been developed in order to discuss the accuracy of solutions. The aims of this study are summarized as follows: (1) to expose the elements that influence the method,precision in the geometrical profile definition, trailing-edge geometry, smoothing problems, number of discretization points, precision of calculation, etc.; (2) to provide an accurate solution for these different problems. For example, some profiles, obtained by the Joukowski transformation, present, in spite of an analytical definition, a crossing of the suction and pressure sides at the trailing edge. This crossing causes a serious error in the velocity field computation. A new procedure to solve this problem is presented. Copyright © 2001 John Wiley & Sons, Ltd. [source] Anomalous charge relaxation in channels of pentacene-based organic field-effect transistors: a charge transient spectroscopy studyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2006I. Thurzo Abstract Two types of Si/SiO2/pentacene organic field-effect transistors (OFET) with bottom Au-source (S) and , drain (D) electrodes were examined by charge transient spectroscopy (QTS), applying pulsed bias ,UDS to the channel of an OFET with floating gate electrode. The transient charge Q (t ), flowing through the channel after the removal of the bias pulse, was processed at a constant temperature by a three-channel correlator yielding the signal ,Q = Q (t1) , 3/2Q (2t1) + 1/2Q (4t1), the scanned delay t1 being related to the trailing edge of the bias pulse. Most of the QTS spectra were characterized by peaks of ,Q (t1) with FWHM corresponding to discrete time constants ,m , t1m, while scanning t1 from 2 ,s to 0.1 s. The common feature of the QTS spectra was a linear dependence of the peak height ,Qm on ,UDS for both polarities of the latter, thereby resembling what is expected for dielectric relaxation (polarization). Some devices showed anomalous (reversed) sign of the signal with respect to the polarity of ,UDS, or even features like transitions from the correct sign to the reversed one. In order to customize the anomalies, a model is presented which ignores injection of excess charge carriers and takes into account two contributions to the total transient charge: a/space charge of intrinsic charge carriers piled up at the blocking Au-electrodes during the pulse, relaxing with the dielectric relaxation time ,D = ,0,r/, (, being conductivity of the organics); b/orientation of molecular dipoles (,dip) in the relaxing electric field of the space charge. It is the dipolar component that is responsible for the anomalous charge flow direction manifested by the signal reversal. The origin of the permanent dipole moment of the otherwise non-polar pentacene molecules may be either attached excess or missing atoms (vacancies) of the defect molecules [J. E. Northrup and M. L. Chabinyc, Phys. Rev. B 68, 041202 (2003)]. In cases of non-blocking contacts the dipolar relaxation would lead to QTS peaks of correct sign, to be distinguished from possibly non-negligible contribution of the dielectric relaxation in the semiconductor. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] 3-D Inviscid Transonic Condensing Flow around a Swept WingPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003K.A. Goodheart Transonic condensing flow is an interesting phenomena because of the large change in temperature over a small area. This drop in temperature allows the moist air to condense. It is the purpose of this paper to examine the effect of sweep on condensing flow. The geometry of the wing model starts with NACA-0014 at the wall and reduces to a NACA-0010 at the tip. The span of the wing is 2.5 times the maximum chord length. The effect of sweep is examined by comparing a model wing with a sweep angle of 11.3 with a straight trailing edge that has no thickness and then a straight leading edge with a 11.3 trailing edge sweep. The free stream Mach number is 0.8 and angle of attack is 0. A 2-D calculation shows that the NACA-0014 and NACA-0010 have a region of supersonic flow but due to the effect of sweep the sonic line does not extend to the tip. This change of the supersonic region influences the area of condensation on the wing. The swept wing has a lower total drag coefficient for the adiabatic and all condensation cases compared to the straight leading edge wing and second for the each wing the trend of increasing drag with humidity is shown. [source] Examination of the three-dimensional geometry of cetacean flukes using computed tomography scans: Hydrodynamic implicationsTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 6 2007Frank E. Fish Abstract The flukes of cetaceans function in the hydrodynamic generation of forces for thrust, stability, and maneuverability. The three-dimensional geometry of flukes is associated with production of lift and drag. Data on fluke geometry were collected from 19 cetacean specimens representing eight odontocete genera (Delphinus, Globicephala, Grampus, Kogia, Lagenorhynchus, Phocoena, Stenella, Tursiops). Flukes were imaged as 1 mm thickness cross-sections using X-ray computer-assisted tomography. Fluke shapes were characterized quantitatively by dimensions of the chord, maximum thickness, and position of maximum thickness from the leading edge. Sections were symmetrical about the chordline and had a rounded leading edge and highly tapered trailing edge. The thickness ratio (maximum thickness/chord) among species increased from insertion on the tailstock to a maximum at 20% of span and then decreasing steadily to the tip. Thickness ratio ranged from 0.139 to 0.232. These low values indicate reduced drag while moving at high speed. The position of maximum thickness from the leading edge remained constant over the fluke span at an average for all species of 0.285 chord. The displacement of the maximum thickness reduces the tendency of the flow to separate from the fluke surface, potentially affecting stall patterns. Similarly, the relatively large leading edge radius allows greater lift generation and delays stall. Computational analysis of fluke profiles at 50% of span showed that flukes were generally comparable or better for lift generation than engineered foils. Tursiops had the highest lift coefficients, which were superior to engineered foils by 12,19%. Variation in the structure of cetacean flukes reflects different hydrodynamic characteristics that could influence swimming performance. Anat Rec, 290:614,623, 2007. © 2007 Wiley-Liss, Inc. [source] Where the trailing edge of anthropology meets the leading edge of bioethicsANTHROPOLOGY TODAY, Issue 4 2002Jonathan Marks First page of article [source] Numerical Study of a Bio-Centrifugal Blood Pump With Straight Impeller Blade ProfilesARTIFICIAL ORGANS, Issue 2 2010Guoliang Song Abstract Computational fluid dynamic simulations of the flow in the Kyoto-NTN (Kyoto University, Kyoto, Japan) magnetically suspended centrifugal blood pump with a 16-straight-bladed impeller were performed in the present study. The flow in the pump was assumed as unsteady and turbulent, and blood was treated as a Newtonian fluid. At the impeller rotating speed of 2000 rpm and flow rate of 5 L/min, the pump produces a pressure head of 113.5 mm Hg according to the simulation. It was found that the double volute of the pump has caused symmetrical pressure distribution in the volute passages and subsequently caused symmetrical flow patterns in the blade channels. Due to the tangentially increasing pressure in the volute passages, the flow through the blade channels initially increases at the low-pressure region and then decreases due to the increased pressure. The reverse flow and vortices have been identified in the impeller blade channels. The high shear stress of the flow in the pump mainly occurred at the inlet and outlet of the blade channels, the beginning of the volute passages and the regions around the tips of the cutwater and splitter plate. Higher shear stress is obtained when the tips of the cutwater and splitter plate are located at the impeller blade trailing edges than when they are located at the middle of the impeller blade channel. It was found that the blood damage index assessed based on the blood corpuscle path tracing of the present pump was about 0.94%, which has the same order of magnitude as those of the clinical centrifugal pumps reported in the literature. [source] | |||||||||||||