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Mobile edge computing (MEC) has been recognized as a viable technology to satisfy low-delay computation requirements for resource-constrained Internet of things (IoT) devices. Nevertheless, the broadcast feature of wireless electromagnetic communications may lead to the security threats to IoT devices. In order to enhance the task offloading security, this paper proposes a reconfigurable intelligent surface (RIS)-assisted secure MEC network framework. Furthermore, we investigate the max-min computation efficiency problem under the secure computation rate requirements, by jointly optimizing the local computing frequencies and transmission power of IoT devices, time-slot assignment, and phase beamforming of the RIS. To solve the formulated non-convex problem, we further develop an iterative algorithm, in which the Dinkelbach-type method and block coordinate descent (BCD) technique are utilized to tackle the fractional objective function and coupled optimization variables, respectively. In particular, the successive convex approximation (SCA) and penalty function-based methods are exploited to solve the transmit power control and reflecting beamforming optimization subproblems, respectively, and the closed-form expression for local computing frequencies optimization subproblem is derived. Numerical results quantify the performance gain achieved by the proposed RIS-assisted secure MEC networks, when compared to existing benchmark methods. [ABSTRACT FROM AUTHOR]

The combination of wireless energy transfer (WET) and mobile edge computing (MEC) has been proposed to satisfy the energy supply and computation requirements of resource-constrained Internet of Things (IoT) devices. However, the energy transfer efficiency and task offloading rate cannot be guaranteed when wireless links between the hybrid access point (HAP) and IoT devices are hostile. To address this problem, this paper aims at utilizing the intelligent reflecting surfaces (IRS) technique to improve the efficiency of WET and task offloading. In particular, we investigate the total computation bits maximization problem for IRS-enhanced wireless powered MEC networks, by jointly optimizing the downlink/uplink phase beamforming of IRS, transmission power and time slot assignment used for WET and task offloading, and local computing frequencies of IoT devices. Furthermore, an iterative algorithm is presented to solve the non-convex non-linear optimization problem, while the optimal transmission power and time allocation, uplink phase beamforming matrixes and local computing frequencies are derived in closed-form expressions. Finally, extensive simulation results validate that our proposed IRS-enhanced wireless powered MEC strategy can achieve higher total computation rate as compared to existing baseline schemes. [ABSTRACT FROM AUTHOR]

Hovering insects require a rather large lift coefficient. Many insects hover with a large stroke amplitude (120°-170°), and it has been found that the high lift is mainly produced by the delayed-stall mechanism. However, some insects hover with a small stroke amplitude (e.g., 65°). The delayed-stall mechanism might not work for these insects because the wings travel only a very short distance in a stroke, and other aerodynamic mechanisms must be operating. Here we explore the aerodynamic mechanisms of a hoverfly hovering with an inclined stroke plane and a small stroke amplitude (65.6°). The Navier-Stokes equations are numerically solved to give the flows and forces and the theory of vorticity dynamics used to reveal the aerodynamic mechanisms. The majority of the weight-supporting vertical force is produced in the mid portion of the downstroke, a short period (about 26% of the stroke cycle) in which the vertical force coefficient is larger than 4. The force is produced using a new mechanism, the "paddling mechanism." During the short period, the wing moves rapidly downward and forward at a large angle of attack (about 48°), and strong counter clockwise vorticity is produced continuously at the trailing edge and clockwise vorticity at the leading edge, resulting in a large time rate of change in the first moment of vorticity, hence the large aerodynamic force. It is interesting to note that with the well known delayed stall mechanism, the force is produced by the relative motion of two vortices of opposite sign, while in the "paddling mechanism," it is produced by generating new vortices of opposite sign at different locations. [ABSTRACT FROM AUTHOR]

Cockayne syndrome (CS) is a rare autosomal recessive disorder characterized principally by progressive growth failure, neurologic abnormality and premature aging. Mutations of excision repair cross-complementation group 6 (ERCC6) and ERCC8 are predominantly responsible for CS, of which mutation of ERCC6 accounts for approximately two thirds of cases. The current report describes two siblings with severe neurologic abnormality and premature aging. Whole exome sequencing identified two novel mutations in ERCC6 that had not been previously reported. One was a nonsense mutation at codon 612 in exon 9 (c.1834C>T, p.Arg612Ter), and the other a missense mutation at codon 975 in exon 16 (c.2923C>T, p.Arg975Trp). Cosegregation analysis revealed c.1834C>T was paternal and c.2923C>T was maternal. A healthy baby with no mutated alleles was delivered based on prenatal diagnosis performed by genetic testing of amniocytes for the causative mutation. The present study will enrich the clinical and genetic spectrum of CS in China and world wide, and provides more evidence for future genotype-phenotype studies. [ABSTRACT FROM AUTHOR]

Background: Recruitment of bone marrow derived endothelial progenitor cells (BMDEPCs) alleviates multiple organ injury (MOI) and improves outcomes. However, mechanisms mediating BMDEPC recruitment following septic MOI remain largely unknown. This study characterized the kinetics of BMDEPC recruitment and proliferation and defined the role of NF-κB in regulating BMDEPC recruitment and proliferation. Methods and Main Findings: Chimeric mice with an intact or disrupted NF-κB p50 gene and BMDEPC-restricted expression of green fluorescent protein were created and injected with LPS (2 mg/kg, i.p.). BMDEPC recruitment and proliferation in multiple organs were quantified. BMDEPC recruitment and proliferation are highly organ-dependent. Lungs had the highest number of BMDEPC recruitment, whereas heart, liver and kidney had only a small fraction of the number of BMDEPCs in lungs. Number of proliferating BMDEPCs was several-fold higher in lungs than in other 3 organs. Kinetically, BMDEPC recruitment into different organs showed different time course profiles. NF-κB plays obligatory roles in mediating BMDEPC recruitment and proliferation. Universal deletion of NF-κB p50 gene inhibited LPS-induced BMDEPC recruitment and proliferation by 95% and 69% in heart. However, the contribution of NF-κB to these regulations varies significantly between organs. In liver, universal p50 gene deletion reduced LPS-induced BMDEPC recruitment and proliferation only by 49% and 35%. NF-κB activities in different tissue compartments play distinct roles. Selective p50 gene deletion either in stromal/parenchymal cells or in BM/blood cells inhibited BMDEPC recruitment by a similar extent. However, selective p50 gene deletion in BM/blood cells inhibited, but in stromal/parenchymal cells augmented BMDEPC proliferation. Conclusions: BMDEPC recruitment and proliferation display different kinetics in different organs following endotoxemic MOI. NF-κB plays obligatory and organ-dependent roles in regulating BMDEPC recruitment and proliferation. NF-κB activities in different tissue compartments play distinct roles in regulating BMDEPC proliferation. [ABSTRACT FROM AUTHOR]

Abstract: Background: Hypoxic pulmonary arterial hypertension (PAH) is a disabling disease with limited treatment options. Hypoxic pulmonary vascular remodeling is a major cause of hypoxic PAH. Pharmacological agents that can inhibit the remodeling process may have great therapeutic value. Objective: To examine the effect of intermedin (IMD), a new calcitonin gene-related peptide family of peptide, on hypoxic pulmonary vascular remodeling. Methods: Rats were exposed to normoxia or hypoxia (∼10% O2), or exposed to hypoxia and treated with IMD, administered by an implanted mini-osmotic pump (6.5 μg/rat/day), for 4 weeks. The effects of IMD infusion on the development of hypoxic PAH and right ventricle (RV) hypertrophy, on pulmonary vascular remodeling, on pulmonary artery smooth muscle cell (PASMC) proliferation and apoptosis, and on the activations of l-arginine nitric oxide (NO) pathway and endoplasmic reticulum stress apoptotic pathway were examined. Results: Rats exposed to hypoxia developed PAH and RV hypertrophy. IMD treatment alleviated PAH and prevented RV hypertrophy. IMD inhibited hypoxic pulmonary vascular remodeling as indicated by reduced wall thickness and increased lumen diameter of pulmonary arterioles, and decreased muscularization of distal pulmonary vasculature in hypoxia-exposed rats. IMD treatment inhibited PASMC proliferation and promoted PASMC apoptosis. IMD treatment increased tissue level of constitutive NO synthase activity and tissue NO content in lungs, and enhanced l-arginine uptake into pulmonary vascular tissues. IMD treatment increased cellular levels of glucose-regulated protein (GRP) 78 and GRP94, two major markers of endoplasmic reticulum (ER) stress, and increased caspase-12 expression, the ER stress-specific caspase, in lungs and cultured PASMCs. Conclusions: These results demonstrate that IMD treatment attenuates hypoxic pulmonary vascular remodeling, and thereby hypoxic PAH mainly by inhibiting PASMC proliferation. Promotion of PASMC apoptosis may also contribute to the inhibitory effect of IMD. Activations l-arginine–NO pathway and of ER stress-specific apoptosis pathway could be the mechanisms mediating the anti-proliferative and pro-apoptotic effects of IMD. [Copyright &y& Elsevier]

Background: MtDNA haplogroups could have important implication for understanding of the relationship between the mutations of the mitochondrial genome and diseases. Distribution of a variety of diseases among these haplogroups showed that some of the mitochondrial haplogroups are predisposed to disease. To examine the susceptibility of mtDNA haplogroups to ROU, we sequenced the mtDNA HV1, HV2 and HV3 in Chinese ROU. Methodology/Principal Findings: MtDNA haplogroups were analyzed in the 249 cases of ROU patients and the 237 cases of healthy controls respectively by means of primer extension analysis and DNA sequencing. Haplogroups G1 and H were found significantly more abundant in ROU patients than in healthy persons, while haplogroups D5 and R showed a trend toward a higher frequency in control as compared to those in patients. The distribution of C-stretch sequences polymorphism in mtDNA HV1, HV2 and HV3 regions was found in diversity. Conclusions/Significance: For the first time, the relationship of mtDNA haplogroups and ROU in Chinese was investigated. Our results indicated that mtDNA haplogroups G1 and H might constitute a risk factor for ROU, which possibly increasing the susceptibility of ROU. Meanwhile, haplogroups D5 and R were indicated as protective factors for ROU. The polymorphisms of C-stretch sequences might being unstable and influence the mtDNA replication fidelity. [ABSTRACT FROM AUTHOR]

The composition of amylopectin is the determinant of rice eating quality under certain threshold of protein content and the ratio of amylose and amylopectin. In molecular biology level, the fine structure of amylopectin is determined by relative activities of starch branching enzyme (SBE), granule-bound starch synthase (GBSS), and soluble starch synthase (SSS) in rice grain under the same ADP-Glucose level. But the underlying mechanism of eating quality in molecular biology level remains unclear. This paper reports the differences on major parameters such as SNP and insertion-deletion sites, RNA expressions, and enzyme activities associated with eating quality of japonica varieties. Eight japonica rice varieties with significant differences in various eating quality parameters such as palatability and protein content were used in this experiment. Association analysis between nucleotide polymorphism and eating quality showed that S12 and S13 loci in SBE1, S55 in SSS1, S58 in SSS2A were significantly associated with apparent amylose content, alkali digestion value, setback viscosity, consistency viscosity, pasting temperature, which explained most of the variation in apparent amylose content, setback viscosity, and consistency viscosity; and explained almost all variations in alkali digestion value and pasting temperature. Thirty-five SNPs and insertion-deletions from SBE1, SBE3, GBSS1, SSS1, and SSS2A differentiated high or intermediate palatability rice varieties from low palatability rice varieties. Correlation analysis between enzyme activities and eating quality properties revealed that SBE25 and SSS15/W15 were positively correlated with palatability, whereas GBSS10 and GBSS15 were negatively correlated. Gene expressions showed that SBE1 and SBE3 expressions in high palatability varieties tended to be higher than middle and low palatability varieties. Collectively, SBE1, SBE3, SSS1, and SSS2A, especially SBE1 and SBE3 could improve eating quality, but GBSS1 decreased eating quality. The results indicated the possibility of developing high palatability cultivars through modification of key genes related to japonica rice eating quality formation in starch biosynthesis. [ABSTRACT FROM AUTHOR]

We studied the effects of wing deformation on the aerodynamic forces of wings of hovering hoverflies by solving the Navier-Stokes equations on a dynamically deforming grid, employing the recently measured wing deformation data of hoverflies in free-flight. Three hoverf lies were considered. By taking out the camber deformation and the spanwise twist deformation one by one and by comparing the results of the deformable wing with those of the rigid flat-plate wing (the angle of attack of the rigid flatplate wing was equal to the local angle of attack at the radius of the second moment of wing area of the deformable wing), effects of camber deformation and spanwise twist were identified. The main results are as follows. For the hovering hoverf lies considered, the time courses of the lift, drag and aerodynamic power coefficients of the deformable wing are very similar to their counterparts of the rigid flat-plate wing, although lift of the deformable wing is about 10% larger, and its aerodynamic power required about 5% less than that of the rigid flat-plate wing. The difference in lift is mainly caused by the camber deformation, and the difference in power is mainly caused by the spanwise twist. The main reason that the deformation does not have a very large effect on the aerodynamic force is that, during hovering, the wing operates at a very high angle of attack (about 5odeg) and the flow is separated, and separated flow is not very sensitive to wing deformation. Thus, as a first approximation, the deformable wing in hover flight could be modeled by a rigid flat-plate wing with its angle of attack being equal to the local angle of attack at the radius of second moment of wing area of the deformable wing. [ABSTRACT FROM AUTHOR]

Effects of unsteady deformation of a flapping model insect wing on its aerodynamic force production are studied by solving the Navier-Stokes equations on a dynamically deforming grid. Aerodynamic forces on the flapping wing are not much affected by considerable twist, but affected by camber deformation. The effect of combined camber and twist deformation is similar to that of camber deformation. With a deformation of 6% camber and 20° twist (typical values observed for wings of many insects), lift is increased by 10% ∼ 20% and lift-to-drag ratio by around 10% compared with the case of a rigid flat-plate wing. As a result, the deformation can increase the maximum lift coefficient of an insect, and reduce its power requirement for flight. For example, for a hovering bumblebee with dynamically deforming wings (6% camber and 20° twist), aerodynamic power required is reduced by about 16% compared with the case of rigid wings. [ABSTRACT FROM AUTHOR]

The control of flight forces and moments by flapping wings of a model bumblebee is studied using the method of computational fluid dynamics. Hovering flight is taken as the reference flight: Wing kinematic parameters are varied with respect to their values at hovering flight. Moments about (and forces along) x, y, z axes that pass the center of mass are computed. Changing stroke amplitude (or wingbeat frequency) mainly produces a vertical force. Changing mean stroke angle mainly produces a pitch moment. Changing wing angle of attack, when down-and upstrokes have equal change, mainly produces a vertical force, while when down-and upstrokes have opposite changes, mainly produces a horizontal force and a pitch moment. Changing wing rotation timing, when dorsal and ventral rotations have the same timing, mainly produces a vertical force, while when dorsal and ventral rotations have opposite timings, mainly produces a pitch moment and a horizontal force. Changing rotation duration has very small effect on forces and moments. Anti-symmetrically changing stroke amplitude (or wingbeat frequency) of the contralateral wings mainly produces a roll moment. Anti-symmetrically changing angles of attack of the contralateral wings, when down-and upstrokes have equal change, mainly produces a roll moment, while when down-and upstrokes have opposite changes, mainly produces a yaw moment. Anti-symmetrically changing wing rotation timing of the contralateral wings, when dorsal and ventral rotations have the same timing, mainly produces a roll moment and a side force, while when dorsal and ventral rotations have opposite timings, mainly produces a yaw moment. Vertical force and moments about the three axes can be separately controlled by separate kinematic variables. A very fast rotation can be achieved with moderate changes in wing kinematics. [ABSTRACT FROM AUTHOR]

The longitudinal stabilization control of a hovering model insect was studied using the method of computational fluid dynamics to compute the stability and control derivatives, and the techniques of eigenvalue and eigenvector analysis and modal decomposition, for solving the equations of motion (morphological and certain kinematical data of hoverflies were used for the model insect). The model insect has the same three natural modes of motion as those reported recently for a hovering bumblebee: one unstable oscillatory mode, one stable fast subsidence mode and one stable slow subsidence mode. Controllability analysis shows that although unstable, the flight is controllable. For stable hovering, the unstable oscillatory mode needs to be stabilized and the slow subsidence mode needs stability augmentation. The former can be accomplished by feeding back pitch attitude, pitch rate and horizontal velocity to produce δϕ or δα2; the latter by feeding back vertical velocity to produce δΦ or δα1 (δΦ, δϕ, δα1 and δα2 denote control inputs: δΦ and δϕ represent changes in stroke amplitude and mean stroke angle, respectively; δα1 represents an equal change whilst δα2 a differential change in the geometrical angles of attack of the downstroke and upstroke). [ABSTRACT FROM AUTHOR]

The lift and power requirements of a model dragonfly in forward flight are studied, using the method of numerically solving the Navier-Stokes equations. The graph of power against flight speed is U-shaped, suggesting that a dragonfly might have a preferred cruising speed. Considerable variation in the relative phase between fore- and hindwings results in only very small change in power requirement. This suggests theat the forewing-hingwing interaction is weak and furthermore, might explain why phase angles ranging from to are employed by dragonflies in hovering and forward flight. [ABSTRACT FROM AUTHOR]

The aerodynamics and forewing-hindwing interaction of a model dragonfly in forward flight are studied, using the method of numerically solving the Navier-Stokes equations. Available morphological and stroke-kinematic parameters of dragonfly (Aeshna jancea) are used for the model dragonfly. Six advance ratios (J; ranging from 0 to 0.75) and, at each J, four forewing-hindwing phase angle differences (γd; 180°, 90°, 60° and 0°) are considered. The mean vertical force and thrust are made to balance the weight and body-drag, respectively, by adjusting the angles of attack of the wings, so that the flight could better approximate the real flight. At hovering and low J (J=0, 0.15), the model dragonfly uses separated flows or leading-edge vortices (LEV) on both the fore- and hindwing downstrokes; at medium J (J=0.30, 0.45), it uses the LEV on the forewing downstroke and attached flow on the hindwing downstroke; at high J (J=0.6, 0.75), it uses attached flows on both fore- and hindwing downstrokes. (The upstrokes are very lightly loaded and, in general, the flows are attached.) At a given J, at γd=180°, there are two vertical force peaks in a cycle, one in the first half of the cycle, produced mainly by the hindwing downstroke, and the other in the second half of the cycle, produced mainly by the forewing downstroke; at γd=90°, 60° and 0°, the two force peaks merge into one peak. The vertical force is close to the resultant aerodynamic force [because the thrust (or body-drag) is much smaller than vertical force (or the weight)]. 55–65% of the vertical force is contributed by the drag of the wings. The forewing-hindwing interaction is detrimental to the vertical force (and resultant force) generation. At hovering, the interaction reduces the mean vertical force (and resultant force) by 8–15%, compared with that without interaction; as J increases, the reduction generally decreases (e.g. at J=0.6 and γd=90°, it becomes 1.6%). A possible reason for the detrimental interaction is as follows: each of the wings produces a mean vertical force coefficient close to half that needed for weight support, and a downward flow is generated in producing the vertical force; thus, in general, a wing moves in the downwash-velocity field induced by the other wing, reducing its aerodynamic forces. [ABSTRACT FROM AUTHOR]

The longitudinal dynamic flight stability of a hovering bumblebee was studied using the method of computational fluid dynamics to compute the aerodynamic derivatives and the techniques of eigenvalue and eigenvector analysis for solving the equations of motion. For the longitudinal disturbed motion, three natural modes were identified: one unstable oscillatory mode, one stable fast subsidence mode and one stable slow subsidence mode. The unstable oscillatory mode consists of pitching and horizontal moving oscillations with negligible vertical motion. The period of the oscillations is 0.32 s (approx. 50 times the wingbeat period of the bumblebee). The oscillations double in amplitude in 0.1 s; coupling of nose-up pitching with forward horizontal motion (and nose-down pitching with backward horizontal motion) in this mode causes the instability. The stable fast subsidence mode consists of monotonic pitching and horizontal motions, which decay to half of the starting values in 0.024 s. The stable slow subsidence mode is mainly a monotonic descending (or ascending) motion, which decays to half of its starting value in 0.37 s. Due to the unstable oscillatory mode, the hovering flight of the bumblebee is dynamically unstable. However, the instability might not be a great problem to a bumblebee that tries to stay hovering: the time for the initial disturbances to double (0.1 s) is more than 15 times the wingbeat period (6.4 ms), and the bumblebee has plenty of time to adjust its wing motion before the disturbances grow large. [ABSTRACT FROM AUTHOR]

Aerodynamic force generation and mechanical power requirements of a dragonfly (Aeschna juncea) in hovering flight are studied. The method of numerically solving the Navier-Stokes equations in moving overset grids is used. When the midstroke angles of attack in the downstroke and the upstroke are set to 52° and 8°, respectively (these values are close to those observed), the mean vertical force equals the insect weight, and the mean thrust is approximately zero. There are two large vertical force peaks in one flapping cycle. One is in the first half of the cycle, which is mainly due to the hindwings in their downstroke; the other is in the second half of the cycle, which is mainly due to the forewings in their downstroke. Hovering with a large stroke plane angle (52°), the dragonfly uses drag as a major source for its weight-supporting force (approximately 65% of the total vertical force is contributed by the drag and 35% by the lift of the wings). The vertical force coefficient of a wing is twice as large as the quasi-steady value. The interaction between the fore- and hindwings is not very strong and is detrimental to the vertical force generation. Compared with the case of a single wing in the same motion, the interaction effect reduces the vertical forces on the fore- and hindwings by 14% and 16%, respectively, of that of the corresponding single wing. The large vertical force is due to the unsteady flow effects. The mechanism of the unsteady force is that in each downstroke of the hindwing or the forewing, a new vortex ring containing downward momentum is generated, giving an upward force. The body-mass-specific power is 37 W kg-1, which is mainly contributed by the aerodynamic power. [ABSTRACT FROM AUTHOR]

Aerodynamic force generation and power requirements in forward flight in a fruit fly with modeled wing motion were studied using the method of computational fluid dynamics. The Navier-Stokes equations were solved numerically. The solution provided the flow velocity and pressure fields, from which the vorticity wake structure and the unsteady aerodynamic forces and torques were obtained (the inertial torques due to the acceleration of the wing-mass were computed analytically). From the flowstructure and force information, insights were gained into the unsteady aerodynamic force generation. On the basis of the aerodynamic and inertial torques, the mechanical power was obtained, and its properties were investigated. The unsteady force mechanisms revealed previously for hovering (i.e. delayed stall, rapid acceleration at the beginning of the strokes and fast pitching-up rotation at the end of the strokes) apply to forward flight. Even at high advance ratios, e.g. J=0.53-0.66 (J is the advance ratio), the leading edge vortex does not shed (at such advance ratios, the wing travels approximately 6.5 chord lengths during the downstroke). At !ow speeds (J≈0.13), the lift (vertical force) for weight support is produced during both the down- and upstrokes (the downstroke producing approximately 80% and the upstroke producing approximately 20% of the mean lift), and the lift is contributed mainly by the wing lift; the thrust that overcomes the body drag is produced during the upstroke, and it is contributed mainly by the wing drag. At medium speeds (J≈0.27), the lift is mainly produced during the downstroke and the thrust mainly during the upstroke; both of them are contributed almost equally by the wing lift and wing drag. At high speeds (J≈0.53), the lift is mainly produced during the downstroke and is mainly contributed by the wing drag; the thrust is produced during both the down- and upstrokes, and in the downstroke, is contributed by the wing lift and in the upstroke, by the wing drag. In forward flight, especially at medium and high flight speeds, the work done during the downstroke is significantly greater than during the upstroke. At advance ratios J≈0.13, 0.27 and 0.53, the work done during the downstroke is approximately 1.6, 2.8 and 4.2 times as much as that during the upstroke, respectively. At J=O (hovering), the body-mass-specific power is approximately 29 W kg[sup -1]; at J=0.13 and 0.27, the power is approximately 10% less than that of hovering; at J=0.40, the power is approximately the same as that of hovering; when J is further increased, the power increases sharply. The graph of power against flying speeds is approximately J -shaped. From the graph of power against flying speeds, it is predicted that the insect usually flies at advance ratios between zero and 0.4, and for fast flight, it would fly at an advance ratio between 0.4 and 0.53. [ABSTRACT FROM AUTHOR]

The lift and power requirements for hovering flight in Drosophila virilis were studied using the method of computational fluid dynamics. The Navier-Stokes equations were solved numerically. The solution provided the flow velocity and pressure fields, from which the unsteady aerodynamic forces and moments were obtained. The inertial torques due to the acceleration of the wing mass were computed analytically. On the basis of the aerodynamic forces and moments and the inertial torques, the lift and power requirements for hovering flight were obtained. For the fruit fly Drosophila virilis in hovering flight (with symmetrical rotation), a midstroke angle of attack of approximately 37° was needed for the mean lift to balance the insect weight, which agreed with observations. The mean drag on the wings over an up- or downstroke was approximately 1.27 times the mean lift or insect weight (i.e. the wings of this tiny insect must overcome a drag that is approximately 27 % larger than its weight to produce a lilt equal to its weight). The body-mass-specific power was 28.7Wkg[sup -1], the muscle-mass-specific power was 95.7Wkg[sup -1] and the muscle efficiency was 17 %. With advanced rotation, larger lift was produced than with symmetrical rotation, but it was more energy-demanding, i.e. the power required per unit lift was much larger. With delayed rotation, much less lilt was produced than with symmetrical rotation at almost the same power expenditure; again, the power required per unit lift was much larger. On the basis of the calculated results for power expenditure, symmetrical rotation should be used for balanced, long-duration flight and advanced rotation and delayed rotation should be used for flight control and manoeuvering. This agrees with observations. [ABSTRACT FROM AUTHOR]

Examines the unsteady aerodynamic force process of a model fruit fly wing in flapping motion. Acceleration of the wing at the beginning of a stroke; Increase of pitching-up rotation of the wing; Absence of stall during the stroke.

Replaces tangential blowing with alternating tangential blowing/suction in boundary layer control. Implication of boundary-layer separation; Numerical simulations based on Navier-Stokes equations; Variation of the aerodynamic forces.

Background and aims Chronic intermittent hypoxia (CIH) exposure causes atherosclerosis, although the underlying mechanisms are poorly understood. This study defines the role of endothelial intrinsic NF-κB signaling in the atherogenic response to CIH. Methods We created ApoE-EC I-κBmt mice that are deficient in the apolipoprotein E gene ( ApoE −/− ) and overexpress an I-κBα mutant (I-κBmt) selectively in endothelial cells. ApoE −/− and ApoE-EC I- κBmt mice were fed a normal chow diet (NCD) or high cholesterol diet (HCD) and exposed to sham or CIH, and atherosclerotic lesions were quantified. Results CIH exposure activated NF-κB in aortas, and induced the expression of endothelial-specific and NF-κB-dependent genes, E-selectin and vascular cell adhesion molecule (VCAM)-1, in the aortas and hearts. Endothelial I-κBmt overexpression in ApoE-EC I-κBmt mice significantly inhibited CIH-induced NF-κB activity, and suppressed E-selectin and VCAM-1 expressions, confirming endothelial NF-κB inhibition in ApoE-EC I-κBmt mice. ApoE −/− mice, on NCD, developed mild atherosclerotic lesions spontaneously, and developed advanced and larger areas of atherosclerotic plaques when exposed to CIH. ApoE −/− mice also developed advanced atherosclerotic lesions when fed an HCD alone. The HCD-induced atherosclerotic plaques became more advanced, and plaque area was doubled in mice exposed to HCD + CIH. Endothelial I-κBmt overexpression in ApoE-EC I-κBmt mice attenuated spontaneously developed atherosclerotic lesions, abrogated CIH-induced atherosclerosis and mitigated CIH-mediated facilitation of HCD-induced atherosclerosis. Conclusions These results suggest that endothelial intrinsic NF-kB signaling may play a pivotal role in CIH-induced atherosclerosis. [ABSTRACT FROM AUTHOR]

The effects of stroke deviation of a flapping model insect wing on its aerodynamic force production are studied by solving the Navier-Stokes equations. Stroke deviation of a flapping wing often takes the forms of various out-of-plane wing-tip trajectories that depend on the time variation of the stroke deviation angle. In the present paper, four typical wing-tip trajectories, referred to as cases A-D, were used to investigate the effect of stroke deviation by comparing the aerodynamic forces, flows, and power requirements of the flapping wings with and without stroke deviation. The stroke deviation has remarkable influences on the time course of the aerodynamic force of a flapping wing. The influences could be explained by two mechanisms: one is the added-rotation effect, which is introduced by the deviation angle of the wing; the other is the change in effective angle of attack of the wing, which is due to the angular speed of the deviation. In general, the stroke deviation only produces a small effect on the cycle-mean aerodynamic forces, because the changes due to stroke deviation could be roughly offset in a wingbeat cycle. The analysis of power requirements shows that stroke deviation will generally lead to an increase in energy consumption for insect flights, indicating that insects should have the tendency to maintain the flapping motion in a plane for hovering or low-speed flight, as is observed in nature. [ABSTRACT FROM AUTHOR]

The article presents the study "Dragonfly Forewing -- Hindwing Interaction at Various Flight Speeds and Wing Phasing," conducted by Hua Huang and Mao Sun of Beijing University of Aeronautics and Astronautics in China. Scientists have always been enthralled by dragonflies' flight. Researchers are starting to study dragonfly areodynamics and the forewing-hindwing interactions using three-dimensional model wings due to the advances in computational and experimental techniques and facilities.

Aerodynamic force generation in hovering flight in a tiny insect, Encarsia formosa, has been studied. The Reynolds number of the flapping wings (based on the mean chord length and the mean flapping velocity) is around 15. The flapping motion of the insect is unique in that the wing pair "claps" together near the end of an upstroke and "flings" open at the beginning of the subsequent downstroke. The method of solving the Navier-Stokes equations over moving overset grids is used. The fling produces a large lift peak at the beginning of the downstroke, the mechanism of which is the generation of a vortex ring containing a downward jet in a short period; the clap produces a large lift peak near the end of the subsequent upstroke by a similar mechanism. Because the vorticity generated during the clap and fling diffuses rapidly, the clap and fling has little influence on the flows in the rest part of the stroke cycle. The mean lift is enough to support the weight of the insect. The lift peaks due to the clap and fling result in more than 30% increase in mean lift coefficient compared to the case of flapping without clap and fling. [ABSTRACT FROM AUTHOR]

Most hovering insects flap their wings in a horizontal plane (body having a large angle from the horizontal), called 'normal hovering'. But some of the best hoverers, e.g. true hoverflies, hover with an inclined stroke plane (body being approximately horizontal). In the present paper, wing and body kinematics of four freely hovering true hoverflies were measured using three-dimensional high-speed video. The measured wing kinematics was used in a Navier-Stokes solver to compute the aerodynamic forces of the insects. The stroke amplitude of the hoverflies was relatively small, ranging from 65 to 85 deg, compared with that of normal hovering. The angle of attack in the downstroke (~50 deg) was much larger that in the upstroke (~20 deg), unlike normal-hovering insects, whose downstroke and upstroke angles of attack are not very different. The major part of the weight-supporting force (approximately 86%) was produced in the downstroke and it was contributed by both the lift and the drag of the wing, unlike the normal-hovering case in which the weight-supporting force is approximately equally contributed by the two half-strokes and the lift principle is mainly used to produce the force. The mass-specific power was 38.59-46.3 and 27.5-35.4 W kg-1 in the cases of 0 and 100% elastic energy storage, respectively. Comparisons with previously published results of a normal-hovering true hoverfly and with results obtained by artificially making the insects' stroke planes horizontal show that for the true hoverflies, the power requirement for inclined stroke-plane hover is only a little (<10%) larger than that of normal hovering. [ABSTRACT FROM AUTHOR]

We have examined the aerodynamic effects of corrugation in model insect wings that closely mimic the wing movements of hovering insects. Computational fluid dynamics were used with Reynolds numbers ranging from 35 to 3400, stroke amplitudes from 70 to 180 deg and mid-stroke angles of incidence from 15 to 60 deg. Various corrugated wing models were tested (care was taken to ensure that the corrugation introduced zero camber). The main results are as follows. At typical mid-stroke angles of incidence of hovering insects (35-50 deg), the time courses of the lift, drag, pitching moment and aerodynamic power coefficients of the corrugated wings are very close to those of the flat-plate wing, and compared with the flat-plate wing, the corrugation changes (decreases) the mean lift by less than 5% and has almost no effect on the mean drag, the location of the center of pressure and the aerodynamic power required. A possible reason for the small aerodynamic effects of wing corrugation is that the wing operates at a large angle of incidence and the flow is separated: the large angle of incidence dominates the corrugation in determining the flow around the wing, and for separated flow, the flow is much less sensitive to wing shape variation. The present results show that for hovering insects, using a flat-plate wing to model the corrugated wing is a good approximation. [ABSTRACT FROM AUTHOR]

When an insect hovers, the centre of mass of its body oscillates around a point in the air and its body angle oscillates around a mean value, because of the periodically varying aerodynamic and inertial forces of the flapping wings. In the present paper, hover flight including body oscillations is simulated by coupling the equations of motion with the Navier-Stokes equations. The equations are solved numerically; periodical solutions representing the hover flight are obtained by the shooting method. Two model insects are considered, a dronefly and a hawkmoth; the former has relatively high wingbeat frequency (n) and small wing mass to body mass ratio, whilst the latter has relatively low wingbeat frequency and large wing mass to body mass ratio. The main results are as follows. (i) The body mainly has a horizontal oscillation; oscillation in the vertical direction is about 1/6 of that in the horizontal direction and oscillation in pitch angle is relatively small. (ii) For the hawkmoth, the peak-to-peak values of the horizontal velocity, displacement and pitch angle are 0.11 U (U is the mean velocity at the radius of gyration of the wing), 0.22=4mm (c is the mean chord length) and 4 deg., respectively. For the dronefly, the corresponding values are 0.02U, 0.05c=0.15mm and 0.3 deg., much smaller than those of the hawkmoth. (iii) The horizontal motion of the body decreases the relative velocity of the wings by a small amount. As a result, a larger angle of attack of the wing, and hence a larger drag to lift ratio or larger aerodynamic power, is required for hovering, compared with the case of neglecting body oscillations. For the hawkmoth, the angle of attack is about 3.5 deg. larger and the specific power about 9% larger than that in the case of neglecting the body oscillations; for the dronefly, the corresponding values are 0.7 deg. and 2%. (iv) The horizontal oscillation of the body consists of two parts; one (due to wing aerodynamic force) is proportional to 1/cn2 and the other (due to wing inertial force) is proportional to wing mass to body mass ratio. For many insects, the values of 1/cn2 and wing mass to body mass ratio are much smaller than those of the hawkmoth, and the effects of body oscillation would be rather small; thus it is reasonable to neglect the body oscillations in studying their aerodynamics. [ABSTRACT FROM AUTHOR]

Abstract: High levels of ethylene oxide (EO) and acetaldehyde (AE) were detected, using gas chromatography and a portable gas detector, among volatile organic compounds (VOC) emitted during simulated frying of herbs and spices in soybean oil at temperatures between 120°C and 200°C. Both EO and AE were distributed between the gas phase and oil phase after cooking each vegetable at 150°C for 5min under either nitrogen or air at 1atm. EO concentrations in the gas phase (25–75ppm) exceeded the threshold limit value of 1ppm, the TLV TWA value established by the American Conference of Government Industrial Hygienists and permitted by the Occupational Safety and Health Administration. EO has been identified as a significant carcinogen. Thus, while no causal relationship can be concluded from this study, the results suggest a possible relationship between the high levels of EO emitted during frying and the high incidence of lung cancer among Taiwanese women engaged in traditional cooking. [Copyright &y& Elsevier]

To investigate the way in which very small insects compensate for unilateral wing damage, we measured the wing kinematics of a very small insect, a phorid fly (Megaselia scalaris), with 16.7% wing area loss in the outer part of the left wing and a normal counterpart, and we computed the aerodynamic forces and power expenditures of the phorid flies. Our major findings are the following. The phorid fly compensates for unilateral wing damage by increasing the stroke amplitude and the deviation angle of the damaged wing (the large deviation angle gives the wing a deep U-shaped wing path), unlike the medium and large insects studied previously, which compensate for the unilateral wing damage mainly by increasing the stroke amplitude of the damaged wing. The increased stroke amplitude and the deep U-shaped wing path give the damaged wing a larger wing velocity during its flapping motion and a rapid downward acceleration in the beginning of the upstroke, which enable the damaged wing to generate the required vertical force for weight support. However, the larger wing velocity of the damaged wing also generates larger horizontal and side forces, increasing the resultant aerodynamic force of the damaged wing. Due to the larger aerodynamic force and the smaller wing area, the wing loading of the damaged wing is 25% larger than that of the wings of the normal phorid fly; this may greatly shorten the life of the damaged wing. Furthermore, because the damaged wing has much larger angular velocity and produces larger aerodynamic moment compared with the intact wing of the damaged phorid fly, the aerodynamic power consumed by the damaged wing is 38% larger than that by the intact wing, i.e., the energy distribution between the damaged and intact wings is highly asymmetrical; this may greatly increase the muscle wastage of the damaged side. [ABSTRACT FROM AUTHOR]

Miniature insects fly at very low Reynolds number (Re); low Re means large viscous effect. If flapping as larger insects, sufficient vertical force cannot be produced. We measure the wing kinematics for miniature-insect species of different sizes and compute the aerodynamic forces. The planar upstroke commonly used by larger insects changes to a U-shaped upstroke, which becomes deeper as size or Re decreases. For relatively large miniature insects, the U-shaped upstroke produces a larger vertical force than a planar upstroke by having a larger wing velocity and, for very small ones, the deep U-shaped upstroke produces a large transient drag directed upwards, providing the required vertical force. [ABSTRACT FROM AUTHOR]