Effect of flexural and torsional wing flexibility on lift generation in hoverfly flight

The effect of wing flexibility in hoverflies was investigated using an at-scale mechanical model. Unlike dynamically-scaled models, an at-scale model can include all phenomena related to motion and deformation of the wing during flapping. For this purpose, an at-scale polymer wing mimicking a hoverfly was fabricated using a custom micromolding process. The wing has venation and corrugation profiles which mimic those of a hoverfly wing and the measured flexural stiffness of the artificial wing is comparable to that of the natural wing. To emulate the torsional flexibility at the wing-body joint, a discrete flexure hinge was created. A range of flexure stiffnesses was chosen to match the torsional stiffness of pronation and supination in a hoverfly wing. The polymer wing was compared with a rigid, flat, carbon-fiber wing using a flapping mechanism driven by a piezoelectric actuator. Both wings exhibited passive rotation around the wing hinge; however, these rotations were reduced in the case of the compliant polymer wing due to chordwise deformations during flapping which caused a reduced effective angle of attack. Maximum lift was achieved when the stiffness of the hinge was similar to that of a hoverfly in both wing cases and the magnitude of measured lift is sufficient for hovering; the maximum lift achieved by the single polymer and carbon-fiber wings was 5.9?×?10(2)(?)μN and 6.9?×?10(2)(?)μN, respectively. These results suggest that hoverflies could exploit intrinsic compliances to generate desired motions of the wing and that, for the same flapping motions, a rigid wing could be more suitable for producing large lift.     

A modified blade element theory for estimation of forces generated by a beetle-mimicking flapping wing system

We present an unsteady blade element theory (BET) model to estimate the aerodynamic forces produced by a freely flying beetle and a beetle-mimicking flapping wing system. Added mass and rotational forces are included to accommodate the unsteady force. In addition to the aerodynamic forces needed to accurately estimate the time history of the forces, the inertial forces of the wings are also calculated. All of the force components are considered based on the full three-dimensional (3D) motion of the wing. The result obtained by the present BET model is validated with the data which were presented in a reference paper. The difference between the averages of the estimated forces (lift and drag) and the measured forces in the reference is about 5.7%. The BET model is also used to estimate the force produced by a freely flying beetle and a beetle-mimicking flapping wing system. The wing kinematics used in the BET calculation of a real beetle and the flapping wing system are captured using high-speed cameras. The results show that the average estimated vertical force of the beetle is reasonably close to the weight of the beetle, and the average estimated thrust of the beetle-mimicking flapping wing system is in good agreement with the measured value. Our results show that the unsteady lift and drag coefficients measured by Dickinson et al are still useful for relatively higher Reynolds number cases, and the proposed BET can be a good way to estimate the force produced by a flapping wing system.     

Normalized lift: an energy interpretation of the lift coefficient simplifies comparisons of the lifting ability of rotating and flapping surfaces

For a century, researchers have used the standard lift coefficient C(L) to evaluate the lift, L, generated by fixed wings over an area S against dynamic pressure, ?ρv(2), where v is the effective velocity of the wing. Because the lift coefficient was developed initially for fixed wings in steady flow, its application to other lifting systems requires either simplifying assumptions or complex adjustments as is the case for flapping wings and rotating cylinders.This paper interprets the standard lift coefficient of a fixed wing slightly differently, as the work exerted by the wing on the surrounding flow field (L/ρ·S), compared against the total kinetic energy required for generating said lift, ?v(2). This reinterpreted coefficient, the normalized lift, is derived from the work-energy theorem and compares the lifting capabilities of dissimilar lift systems on a similar energy footing. The normalized lift is the same as the standard lift coefficient for fixed wings, but differs for wings with more complex motions; it also accounts for such complex motions explicitly and without complex modifications or adjustments. We compare the normalized lift with the previously-reported values of lift coefficient for a rotating cylinder in Magnus effect, a bat during hovering and forward flight, and a hovering dipteran.The maximum standard lift coefficient for a fixed wing without flaps in steady flow is around 1.5, yet for a rotating cylinder it may exceed 9.0, a value that implies that a rotating cylinder generates nearly 6 times the maximum lift of a wing. The maximum normalized lift for a rotating cylinder is 1.5. We suggest that the normalized lift can be used to evaluate propellers, rotors, flapping wings of animals and micro air vehicles, and underwater thrust-generating fins in the same way the lift coefficient is currently used to evaluate fixed wings.     

Cytoplasmic and outer membranes separation in Rhodopseudomonas sphaeroides

A cell envelope fraction has been prepared after mechanical disruption of lysozyme-EDTA spheroplasts from depigmented Rhodopseudomonas sphaeroides (aerobically grown in the light). On linear sucrose gradients this fraction can be separated in a cytoplasmic membrane fraction and an outer membrane fraction. The cytoplasmic fraction (buoyant density: 1.18 g/cm³) has been characterized by its succinic dehydrogenase activity and by its composition. The outer membrane fraction (buoyant density: 1.21 g/cm³) does not contain any respiratory activity nor hemoproteins. The same fractionation has been done on cells repigmented in the dark by lowering the O₂ pressure. In that case the same two fractions have been detected in addition to the chromatophore fraction (buoyant density: 1.14 g/cm³). However both, and specially the outer membrane fraction, were contaminated by chromatophore material.     

Effect of diamide on force generation and axial stiffness of the cochlear outer hair cell.

We found that diamide, which affects spectrin, reduces the axial stiffness of the cochlear outer hair cell, the cylindrically shaped mechanoreceptor cell with a unique voltage-sensitive motility. This effect thus provides a means of examining the relationship between the stiffness and the motility of the cell. For measuring axial stiffness and force production, we used an experimental configuration in which an elastic probe was attached to the cell near the cuticular plate and the other end of the cell was held with a patch pipette in the whole-cell recording mode. Diamide at concentrations of up to 5 mM reduced the axial stiffness in a dose-dependent manner to 165 nN per unit strain from 502 nN for untreated cells. The isometric force elicited by voltage pulses under whole-cell voltage clamp was also reduced to 35 pN/mV from 105 pN/mV for untreated cells. Thus the isometric force was approximately proportional to the axial stiffness. Our observations suggest a series connection between the motor and cytoskeletal elements and can be explained by the area motor model previously proposed for the outer hair cell.     

Effect of face lift on earlobe ptosis and pseudoptosis

The authors have previously described a classification system for earlobe ptosis and established criteria for earlobe pseudoptosis. Earlobe heights were characterized on the basis of anatomic landmarks, including the intertragal notch, the otobasion inferius (the most caudal anterior attachment of the earlobe to the cheek skin), and the subaurale (the most caudal extension of the earlobe free margin). The classification system was derived from earlobe height preferences as determined by a survey of North American Caucasians and identified the ideal free caudal segment (otobasion inferius to subaurale distance) measuring 1 to 5 mm (grade I ptosis). Also, earlobe pseudoptosis was defined by an attached cephalic segment (intertragal notch to otobasion inferius distance) measuring greater than 15 mm. In this study, the authors evaluated the effects of standard face lift surgery on earlobe ptosis and pseudoptosis by comparing the preoperative and postoperative earlobe height measurements from life-size photographs of 44 patients who underwent rhytidectomy performed by the senior author. The postoperative attached cephalic segment (intertragal notch to otobasion inferius distance, 12.22 +/- 0.364 mm) increased over its preoperative attached cephalic segment (intertragal notch to otobasion inferius distance, 11.10 +/- 0.406 mm) (p = 0.041). The postoperative free caudal segment (otobasion inferius to subaurale distance, 6.32 +/- 0.438 mm) demonstrated only a trend toward decreased heights when compared with the preoperative free caudal segment (otobasion inferius to subaurale distance, 7.15 +/- 0.489 mm) (p = 0.210). The incidence of pseudoptosis, defined by an attached segment (intertragal notch to otobasion inferius distance) greater than 15 mm, increased from 12.3 percent of preoperative patient earlobes to 17.3 percent of postoperative patient earlobes. An ideal free caudal segment (otobasion inferius to subaurale distance), defined by a range of 1 to 5 mm, was observed in only 37.0 percent of postoperative earlobes versus 22.2 percent of preoperative earlobes. Significant increases in the attached cephalic segments (intertragal notch to otobasion inferius distance) following rhytidectomies correlated with increased incidence of earlobe pseudoptosis, as observed in 17.3 percent of postoperative patient earlobes. Because the free caudal segment was negligibly affected by rhytidectomy, a majority of earlobes (63.0 percent) demonstrated persistent nonoptimal free caudal segment heights (otobasion inferius to subaurale distance > 5 mm). Earlobe height changes can result from either age-related lobule ptosis (increase in free caudal segment) as previously described or in patients undergoing rhytidectomy (increase in attached cephalic segment). Therefore, ideal lobule distances along with the effects of aging and rhytidectomy surgery on the lobule should be discussed with patients who are seeking a more youthful facial appearance, so that the aging ear may be addressed concurrently with the aging face.     

Growth of E. coli in a stirred tank and in an air lift tower reactor with an outer loop

E. coli ATCC 11105 was cultivated in a 10-1 stirred tank reactor and in a 60-1 tower loop reactor in batch and continuous operation. By on-line measurements of O₂ and CO₂ concentrations in the outlet gas, pH, temperature, cell mass concentration X as well as dissolved O₂ concentration along the tower in the broth, gas holdup, broth recirculation rate through the loop and by offline measurements of substrate concentration DOC and cell mass concentration along the tower, the maximum specific growth rate _m , yield coefficients Y _X/S. Y _X/DOC and were evaluated in stirred tank and tower loop in batch and continuous cultures with and without motionless mixers in the tower and at different broth circulation rates through the loop. To control the accuracy of the measurements the C balance was calculated and 95% of the C content was covered.The biological parameters determined depend on the mode of operation as well as on the reactor used. Furthermore, they depend on the recirculation rate of the broth and built-ins in the tower. The unstructured cell and reactor models are unable to explain these differences. Obviously, structured cell and reactor models are needed. The cell mass concentration can be determined on line by NADH fluorescence in balanced growth, if the model parameters are determined under the same operational conditions in the same reactor.List of Symbols a, b empirical parameters in Eq. (1) - CPR kg/(m³ h) CO₂ production rate - C kg/m³ concentration - D l/h dilution rate - DOC kg/m³ dissolved organic carbon - I net. fluorescence intensity - K _S kg/m³ Monod constant - k _L a l/h volumetric mass transfer coefficient - OTR kg/(m³ h) oxygen transfer rate - OUR kg/(m³ h) oxygen utilization rate - RQ = CPR/OUR respiratory quotient - S kg/m³ substrate concentration - t h,min, s time - t _u min recirculation time - t _M min mixing time - v m³/h volumetric flow rate through the loop - X kg/m³ (dry) cell mass concentration - Y _X/S yield coefficient of cell mass with regard to the consumed substrate - Y _X/DOC yield coefficient of the cell mass with regard to the consumed DOC - Y _X/O yield coefficient of the cell mass with regard to the consumed oxygen - Z relative distance in the tower from the aerator with regard to the height of the aerated broth - l/h specific growth rate - _m l/h maximum specific growth rate Indices f feed - e outlet     

Effect of slotted wing tips on yawing moment characteristics

The aerodynamic yawing moment characteristics of bird wings with slotted tips are dealt with. Emphasis is placed on the effect of sweep which the separated feathers constituting the wing tips show and which can reach significant values. Reference is made to basic aerodynamic characteristics of wings with sweep which yields a stabilizing yawing moment significantly larger than that of unswept wings. Then, the yawing moment characteristics are determined for a wing, the features of which are considered as representative of bird wings with sweep in their slotted tips. A sophisticated aerodynamic procedure is used for obtaining results of high precision. It is shown that the sweep in the slotted wing tips yields a stabilizing yawing moment of significant magnitude, considerably increasing with the lift coefficient. To make the significance of wing tip sweep for the ability to generate yawing moments more perspicuous, a wing modification the slotted tips of which are unswept is considered for comparison. It turns out that this wing shows yawing moments which are substantially smaller. A physical insight into the effect of slotted wing tip sweep on the aerodynamic yawing moment characteristics is provided by showing the underlying mechanism. From the results presented in this paper it follows that the sweep in slotted wing tips provides a substantial contribution to the aerodynamic yawing moment and, thus, to yaw stability. It may be concluded that this is an essential reason why there is sweep in the slotted tips of bird wings.     

Force generation in the outer hair cell of the cochlea.

The outer hair cell of the mammalian cochlea has a unique motility directly dependent on the membrane potential. Examination of the force generated by the cell is an important step in clarifying the detailed mechanism as well as the biological importance of this motility. We performed a series of experiments to measure force in which an elastic probe was attached to the cell near the cuticular plate and the cell was driven with voltage pulses delivered from a patch pipette under whole-cell voltage clamp. The axial stiffness was also determined with the same cell by stretching it with the patch pipette. The isometric force generated by the cell is around 0.1 nN/mV, somewhat smaller than 0.15 nN/mV, predicted by an area motor model based on mechanical isotropy, but larger than in earlier reports in which the membrane potential was not controlled. The axial stiffness obtained, however, was, on average, 510 nN per unit strain, about half of the value expected from the mechanical isotropy of the membrane. We extended the area motor theory incorporating mechanical orthotropy to accommodate the axial stiffness determined. The force expected from the orthotropic model was within experimental uncertainties.     

Effects of antibody concentration on the separation of human natural killer cells in a commercial immunomagnetic separation system.

BACKGROUND: The magnetic separation of a cell population based on cell surface markers is a critical step in many biological and clinical laboratories. In this study, the effect of antibody concentration on the separation of human natural killer cells in a commercial, immunomagnetic cell separation system was investigated. METHODS: Specifically, the degree of saturation of antibody binding sites using a two-step antibody sandwich was quantified. The quantification of the first step, a primary anti-CD56-PE antibody, was achieved through fluorescence intensity measurements using a flow cytometer. The quantification of the second step, an anti-PE-microbeads antibody reagent, was achieved through magnetophoretic mobility measurements using cell tracking velocimetry. RESULTS: From the results of these studies, two different labeling protocols were used to separate CD56+ cells from human, peripheral blood by a Miltenyi Biotech MiniMACS cell separation system. The first of these two labeling protocols was based on company recommendations, whereas the second was based on the results of the saturation studies. The results from these studies demonstrate that the magnetophoretic mobility is a function of both primary and secondary antibody concentrations and that mobility does have an effect on the performance of the separation system. CONCLUSIONS: As the mobility increased due to an increase in bound antibodies, the positive cells were almost completely eliminated from the negative eluent. However, with an increase in bound antibodies, and thus mobility, the total amount of positive cells recovered decreases. It is speculated that these cells are irreversibly retained in the column. These results demonstrate the complexity of immunomagnetic cell separation and the need to further optimize the cell separation process.     

Occurrence of a coupled-enzyme system on the intact-sperm outer surface that phosphorylates and dephosphorylates ecto-proteins

Goat cauda-epididymal intact sperm ecto [32P] proteins phosphorylated in presence of exogenous [gamma-32P]ATP by an endogenous ecto-cyclic AMP-independent protein kinase (CIK), have been found to lose 32P when the labelled cells are incubated at 37 degrees C in a modified Ringer's solution. Analysis of the 32P-labelled products of the turnover of the ecto-phosphoproteins show that 32Pi rather than 32P-labelled peptides, is released from the cell-surface phosphoproteins indicating that the turnover of the ecto-phosphoproteins is mediated by an endogenous sperm outer-surface phosphoprotein phosphatase (ecto-PPase). The ecto-PPase is not a non-specific phosphatase since unlabelled p-nitrophenyl phosphate, beta-glycerophosphate or ATP at a relatively high concentration (1 mM each) has no appreciable effect on the dephosphorylation of the cell-surface proteins. The intact-sperm ecto-proteins phosphorylated and then dephosphorylated by the endogenous ecto-CIK and PPase respectively, undergo rephosphorylation by the cell-surface CIK. The data are consistent with the view that sperm external surface possesses a novel coupled-ecto-CIK and PPase enzyme system that regulates the phosphorylated states of the intact-sperm ecto-proteins by a cyclic mechanism of protein phosphorylation and dephosphorylation.     

Sequence of centromere separation: generation of unstable multicentric chromosmes in a rat cell line

A transformed cell line, B₁, of cerebral endothelial origin from the Wistar-Kyoto male rat has chromatid and chromosome type bridges in virtually every cell. It exhibits various dicentric and polycentric chromosomes. Most dicentrics are symmetric isochromosomes. Certain isodicentrics are present in a fair segment of the cell population; however, almost all cells have some newly arising isodicentrics. The live cells show a lengthened prometaphase. Anaphase is also retarded possibly due to the occurrence of bridges. At anaphase some multicentrics split at only one centromere. When pulled to the two poles the unsplit centromeres and the distal chromosome segment form a side arm bridge. Another mechanism appears to be a total lack of separation of daughter centromeres at meta-anaphase (meiotic-like behavior of mitotic chromosomes). This is realized by the pulling of each of the two unsplit centromeres to opposite poles and results in bridges with both sister chromatids running parallel to each other. A break at corresponding weak points in the two sister chromatids followed by rejoining can form a dicentric isochromosome. A third mechanism, the breakage-fusion-bridge cycle, is also operative but would not produce isodicentrics. In the case of the first two mechanisms some or all centromeres apparently split between telophase and onset of the following DNA synthesis rather than at the usual time at late metaphase. These observations may suggest some previously unknown behavior of multicentric chromosomes during mitosis.     

Effect of electron mediators on current generation and fermentation in a microbial fuel cell

Effects of select electron mediators [9,10-anthraquinone-2,6-disulfonic acid disodium salt (AQDS), safranine O, resazurin, methylene blue, and humic acids] on metabolic end-products and current production from cellulose digestion by Clostridium cellulolyticum in microbial fuel cells (MFCs) were studied using capillary electrophoresis and traditional electrochemical techniques. Addition of the mediator resazurin greatly enhanced current production but did not appear to alter the examined fermentation end-products compared to MFCs with no mediator. Assays for lactate, acetate, and ethanol indicate that the presence of safranine O, methylene blue, and humic acids alters metabolite production in the MFC: safranine O decreased the examined metabolites, methylene blue increased lactate formation, and humic acids increased the examined metabolites. Mediator standard redox potentials (E ₀) reported in the literature do not coincide with redox potentials in MFCs due presumably to the electrolytic complexity of media that supports bacterial survival and growth. Current production in MFCs: (1) can be effected by the mediator redox potential while in the media, which may be significantly shifted from E ₀, and (2) depended on the ability of the mediator to access the bacterial electron source, which may be cytoplasmic. In addition, some electron mediators had significant effects on metabolic end-products and therefore the metabolism of the organism itself. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of parathyroid hormone and dietary phosphate on phosphate transport in renal outer cortical and outer medullary brush-border membrane vesicles

Two distinctive sodium-dependent phosphate transport systems have been identified in early and late proximal tubules; a high-capacity process located only in outer cortical tissue, and a high affinity present in both outer cortical and outer medullary brush-border membranes (Km 0.1-0.25 mM). A third, sodium-independent, pH gradient-stimulated system (Vmax 4.7 +/- 0.3 nmol.mg-1.min-1, Km 0.15 +/- 0.002 mM) is present in the outer medulla, but absent in outer cortex. Brush-border vesicles were prepared from outer cortical and outer medullary tissue of pigs maintained on low (less than 0.05%), normal (0.4%), or high (4%) phosphate diets. Sodium-dependent phosphate uptake of the high-capacity system decreased (Vmax, 9.4 to 2.2 nmol.mg-1.min-1) from low to high phosphate diet, whereas uptake rates decreased about 50% in the high-affinity system. There were no changes in the respective Km values. The pH gradient-stimulated uptake also decreased (Vmax, 6.9 to 3.0 nmol.mg-1.min-1) with no change in mean Km value (0.15 +/- 0.001 mM) with dietary manipulation. Administration of 1 U parathyroid hormone prior to study resulted in a decrease in sodium-dependent uptake by 40-50% and in pH-dependent uptake (36%) with no change in the respective Km values. In conclusion, the antecedent dietary phosphate intake and parathyroid hormone administration appropriately alters phosphate uptake across the brush-border membrane of all three systems, sodium-dependent and pH gradient-stimulated phosphate transport.     

Modeling human neurodegenerative diseases in Drosophila: on a wing and a prayer

The ability of Drosophila genetics to reveal new insights into human neurodegenerative disease is highlighted not only by mutants in flies that show neuronal cell loss, but also by targeted expression of human disease genes in the fly. Moreover, study of Drosophila homologs of various human disease genes provides new insight into fundamental aspects of protein function. These recent findings confirm the remarkable homology of gene function in flies when compared with humans. With the advent of complete genomic sequencing on the horizon, Drosophila will continue to be an outstanding model system in which to unravel the complexities, causes and treatments for human neural degeneration.     

Temporal and spatial windows delimit activation of the outer ring of wingless in the Drosophila wing

Extracellular signalling molecules play many roles in the development of higher organisms. They are used reiteratively in different tissues and stages, but the response of the receiving cells is controlled in a context dependent manner. The pattern of expression of the signalling molecule Wingless/WNT in Drosophila is extraordinarily complex. We have studied the mechanism that controls its expression and function in the outer ring of the Drosophila wing hinge. Our findings indicate that wingless expression is controlled by a dual mechanism: its initial activation requires the product of zinc finger homeodomain 2 and is subsequently repressed by the product of the gene complex elbow/no ocelli. This tight regulation restricts the activation of wingless temporally and spatially. Later in development, wingless expression is maintained by an autoregulatory loop that involves the product of homothorax. We have analyzed the phenotype of a wingless allelic combination that specifically removes the outer ring, and our results show that Wingless is required to promote local proliferation of the wing base cells. Thus, cell proliferation in the proximal-distal axis is controlled by the sequential activation of wingless in the inner ring and the outer ring at different stages of development.