4,976 research outputs found
Expression of PTEN-WT in the posterior compartment of the wing disc supressed PI3K/Akt signalling.
No full textRepresentative images of imaginal wing discs of 3rd instar larvae stained with anti-GFP to visualize tGPH, a fluorescent sensor of PIP3 levels [74] (A,B) anti-pAkt (A’,B’) and anti-PTEN (A”,B”) for attp2 and PTEN-WT. Expression of PTEN-WT leads to suppression of both PI3K-induced PIP3 and pAkt levels in the posterior compartment of the wing imaginal disc. (TIF)</p
Wing length.
No full text<p>Comparisons of average wing length of WT and OX513A mosquitoes reared at different densities in 100 ml pots; error bars showing 95% CI.</p
Flutter behaviour of composite aircraft wings
Get PDFThis research work presents series of investigations into the structural
dynamics and dynamic aeroelastic (flutter) behaviour of composite and metal wings.
The study begins with a literature review where the development and an over view of
the previous investigations in this field are presented. Static stiffness is very important
to any type of analysis, especially in both dynamic and flutter analysis as in this case.
Therefore, different methods are presented and used for the determination of cross-
sectional rigidities such as bending, torsional and bending-torsional coupling rigidities
properties for beams constructed of laminated and thin-walled structures materials.
A free vibration experimental analysis was conducted on the physical
Cranfield Al aerobatic composite wing box structure. The composite wing box was
exited in the frequency range of 0 to 300 Hz, with both sinusoidal and random
excitations, which yields to six resonant frequencies.
The theoretical free vibration and flutter analysis was then carried out firstly
on the physical Cranfield Al aerobatic metal wing box. The metal wing was modeled
using two techniques; the first model was a simplified wing structure (beam with
lumped mass). This analysis of the simplified model was done using CALFUN
program for the free vibration analysis and using MSC/NASTRAN for both free
vibration and flutter analysis. The second model was a detailed model created by
MSC/PATRAN and analyzed by MSC/NASTRAN for the free vibration and flutter
analysis. The obtained results (natural frequencies and mode shapes) showed a good
agreement between the simplified, detailed model and the experimental test. It was
found that even with using the simplified model, but having the physical
characteristics of the wing leads to a good agreement with the detailed model and
experimental work. This also showed the importance of simplified model at early
stage of the design to the structural designer in terms of the accuracy, time, and size of
the model.
Free vibration and flutter analysis was carried out on the Cranfield Al
aerobatic composite wing box with the original laminate lay ups using Lanczos
method for extracting the eigenvalues and eigenvectors and using PK method for
finding the flutter speed and frequency provided by MSC/NASTRAN. The results were compared with the experimental vibration analysis and were found a large
difference in the first frequency mode. To investigate the cause of the variation, a
series of static loading tests were performed on the composite wing box. Also a
comparison of the results between the metal and composite aerobatic wing box is
presented. It was found that the large difference could be due to the combination of
different parameters such as stiffness (age of the wing, delamination and boundary
condition), and increase of mass of the physical wing box (due to environmental effect
such as moisture) and modelling differences.
The free vibration characteristics of ten wing models constructed from
balanced and unbalanced laminate configurations were carried out using Lanczos
method provided by MSC/NASTRAN. The analysis was done on ten wing models
modeled to simulate Circumferentially Asymmetric Stiffness (CAS) and
Circumferentially Uniform Stiffness (CUS). The static equivalent stiffness was
calculated using two different modeling methods for a wide range of fibre angles 0 (-
90° to 90°) of the skins. The variations and the importance of the stiffness ratio
(EI/GJ), parameter (K/GJ), and the frequency ratio (wb/(Ot) are illustrated against the
fibre angle 0. It was found that the fundamental bending frequency is slightly lower in
the case of CUS (K = 0) as compared to the CAS (K # 0), which was not the case in
the plate model. Also, the first torsion frequency mode in the case of CUS was much
lower than the first torsion frequency of the CAS, which was not the case of the plate
model. However, the effect of bend-twist coupling stiffness on the mode shapes was
pronounced in both structures especially at the area of higher coupling stiffness.
The flutter analysis was done using the PK method for all the wing models of
both (CAS) and (CUS) configurations. The results showed the optimum value of
flutter speed and the importance of the stiffness ratio (EI/GJ), parameter (K/GJ), the
frequency ratio (wb/wt), which will lead to the maximum flutter speed. The effects of
the above parameters, geometrical coupling and the wash-in and washout on the non-
dimensional flutter speed are presented. It was concluded that, negative bend-twist
coupling stiffness is beneficial for flutter speed compared to the positive bend-twist
coupling stiffness at 00<0<_30°. It was also found that the flutter speed for the CUS
was higher at 00<0<_300 compared to the CAS. Also creating an offsite between the elastic axis and center of gravity (behind) decreases the flutter speed whereas having
more ribs increases the flutter speed compared with adding stringers.
The analysis was carried out on a more practical composite wing box, which
was the physical Cranfield Al aerobatic composite wing box. There are some
simplifications on the physical structure, which are the cancellation of the woven
materials and keeping the same laminate lay ups for the upper and lower skin. The
natural frequency and mode shapes was obtained and plotted against the fibre angle 0
of the upper and lower skin for the (CAS) and (CUS) configurations using both
symmetric and asymmetric laminate for the upper and lower skin. The flutter analysis
was done for the composite wing box for the same configurations as in the free
vibration analysis. The effects of the fibre angle 0 of the upper and lower skin,
material coupling stiffness, wash-in and wash-out, and structural damping on the non-
dimensional flutter speed and flutter frequencies are illustrated. It was found that in
this configurations both structural and bend-twist coupling are exist, negative bend-
twist coupling (wash-in) increases the flutter speed compared with the positive bend-
twist coupling, and the possibility of increasing the flutter speed at higher frequency
ratio, structural coupling and positive bend-twist coupling (wash-out)
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
Get PDFIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
A robust correlation analysis framework for imbalanced and dichotomous data with uncertainty
No full textComparative Study Of The Influence Of Natural Convection On Directional Solidification Of Al-3.5 Wt% Ni And Al-7 Wt% Si Alloys
Get PDFWe present numerical simulations of thermosolutal convection for directional solidification of Al-3.5 wt% Ni and Al-7 wt% Si. Numerical results predict that fragmentation of dendrite arms resulting from dissolution could be favored in Al-7 wt% Si, but not in Al-3.5 wt% Ni. Corresponding experiments are in qualitative agreement with the numerical predictions. Distinguishing the two fragmentation mechanisms, namely dissolution and remelting, is critical during experiments on earth, when fluid flow is dominant. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved
An investigation into the benefits of distributed propulsion on advanced aircraft configurations
Get PDFRadical aircraft and propulsion system architecture changes may be required to continue historic performance improvement rates as current civil aircraft and engine technologies mature. Significant fuel-burn savings are predicted to be achieved through the Distributed Propulsion concept, where an array of propulsors is distributed along the span of an aircraft to ingest boundary layer air and increase propulsive efficiency. Studies such as those by NASA predict large performance benefits when integrating Distributed Propulsion with the Blended Wing Body aircraft configuration, as this planform geometry is particularly suited to the ingestion of boundary layer air and the fans can be redesigned to reduce the detrimental distortion effects on performance. Additionally, a conventional aircraft with Distributed Propulsion has not been assessed in public domain literature and may also provide substantial benefits.
A conceptual aircraft design code has been developed to enable the modelling of conventional and novel aircraft. A distributed fan tool has been developed to model fan performance, and a mathematical derivation was created and integrated with the fan tool to enable the boundary layer ingestion modelling. A tube & wing Distributed Propulsion aircraft with boundary layer ingestion has been compared with a current technology reference aircraft and an advanced turbofan aircraft of 2035 technology. The advanced tube & wing aircraft achieved a 27.5% fuel-burn reduction relative to the baseline aircraft and the Distributed Propulsion variant showed fuel efficiency gains of 4.1% relative to the advanced turbofan variant due to a reduced specific fuel consumption, produced through a reduction in distributed fan power requirement. The Blended Wing Body with Distributed Propulsion was compared with a turbofan variant reference aircraft and a 5.3% fuel-burn reduction was shown to be achievable through reduced core engine size and weight. The Distributed Propulsion system was shown to be particularly sensitive to inlet duct losses. Further investigation into the parametric sensitivity of the system revealed that duct loss could be mitigated by altering the mass flow and the percentage thrust produced by the distributed fans. Fuel-burn could be further reduced bydecreasing component weight and drag, through decreasing the fan and electrical system size to below that necessary for optimum power or specific fuel consumption
Hysteresis phenomenon and wetting characteristics of molten Sn-3.0 wt.%Ag-0.5 wt.%Cu on different tilting substrates
No full textThe hysteresis phenomenon and wetting characteristics of molten Sn-3.0 wt.%Ag-0.5 wt.%Cu on wetting and non-wetting tilting substrates at different temperatures were investigated. The viewpoint on negative interfacial tension was proposed in this paper to explain the spreading and wetting behaviors for sample on different tilted substrates. The critical sliding angle was defined as limited tilting angle of surface at which the molten drop slid down and the upper and lower contact angles of molten drop were measured as the advancing and receding contact angles, respectively. Wetting experiments were performed to determine how contact angle and contact hysteresis on alumina and oxygen-free copper tilting substrates changed with temperature. Static, limited tilting, advancing and receding contact angles on two kinds of substrates were measured at different temperatures. In general, both negative interfacial tension and hysteresis for sample on copper were much larger than that on alumina over the range of temperatures studied, indicating better wettability but worse motion characteristics for the former. It was due to the larger adhesion between solid and liquid than the cohesion of liquid, the negative interfacial tension and the acute contact angle. (C) 2009 Elsevier B.V. All rights reserved
Deletion of vitamin D receptor leads to premature emphysema/COPD by increased matrix metalloproteinases and lymphoid aggregates formation
Get PDFDeficiency of vitamin D is associated with accelerated decline in lung function. Vitamin D is a ligand for nuclear hormone vitamin D receptor (VDR), and upon binding it modulates various cellular functions. The level of VDR is reduced in lungs of patients with chronic obstructive pulmonary disease (COPD) which led us to hypothesize that deficiency of VDR leads to significant alterations in lung phenotype that are characteristics of COPD/emphysema associated with increased inflammatory response. We found that VDR knock-out (VDR(-/-)) mice had increased influx of inflammatory cells, phospho-acetylation of nuclear factor-kappaB (NF-κB) associated with increased proinflammatory mediators, and up-regulation of matrix metalloproteinases (MMPs) MMP-2, MMP-9, and MMP-12 in the lung. This was associated with emphysema and decline in lung function associated with lymphoid aggregates formation compared to WT mice. These findings suggest that deficiency of VDR in mouse lung can lead to an early onset of emphysema/COPD because of chronic inflammation, immune dysregulation, and lung destruction
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