Dynamic Analysis of conical shells containing flowing fluid

Dynamic analysis of anisotropic conical shells -- Natural vibrations of conical shells containing flowing fluid -- The algorithm

Nonlinear unsteady streaks engendered by the interaction of free-stream vorticity with a compressible boundary layer

The nonlinear response of a compressible boundary layer to unsteady free-stream vortical fluctuations of the convected-gust type is investigated theoretically and numerically. The free-stream Mach number is assumed to be of O(1) and the effects of compressibility, including aerodynamic heating and heat transfer at the wall, are taken into account. Attention is focused on low-frequency perturbations, which induce strong streamwise-elongated components of the boundary-layer disturbances, known as streaks or Klebanoff modes. The amplitude of the disturbances is intense enough for nonlinear interactions to occur within the boundary layer. The generation and nonlinear evolution of the streaks, which acquire an O(1) magnitude, are described on a self-consistent and first-principle basis using the mathematical framework of the nonlinear unsteady compressible boundary-region equations, which are derived herein for the first time. The free-stream flow is studied by including the boundary-layer displacement effect and the solution is matched asymptotically with the boundary-layer flow. The nonlinear interactions inside the boundary layer drive an unsteady two-dimensional flow of acoustic nature in the outer inviscid region through the displacement effect. A close analogy with the flow over a thin oscillating airfoil is exploited to find analytical solutions. This analogy has been widely employed to investigate steady flows over boundary layers, but is considered herein for the first time for unsteady boundary layers. In the subsonic regime the perturbation is felt from the plate in all directions, while at supersonic speeds the disturbance only propagates within the dihedron defined by the Mach line. Numerical computations are performed for carefully chosen parameters that characterize three practical applications: turbomachinery systems, supersonic flight conditions and wind tunnel experiments. The results show that nonlinearity plays a marked stabilizing role on the velocity and temperature streaks, and this is found to be the case for low-disturbance environments such as flight conditions. Increasing the free-stream Mach number inhibits the kinematic fluctuations but enhances the thermal streaks, relative to the free-stream velocity and temperature respectively, and the overall effect of nonlinearity becomes weaker. An abrupt deviation of the nonlinear solution from the linear one is observed in the case pertaining to a supersonic wind tunnel. Large-amplitude thermal streaks and the strong abrupt stabilizing effect of nonlinearity are two new features of supersonic flows. The present study provides an accurate signature of nonlinear streaks in compressible boundary layers, which is indispensable for the secondary instability analysis of unsteady streaky boundary-layer flows

Epigenetic change in e-cardherin and COX-2 to predict chronic periodontitis

<p>Abstract</p> <p>Background</p> <p>DNA methylation of certain genes frequently occurs in neoplastic cells. Although the cause remains unknown, many genes have been identified with such atypical methylation in neoplastic cells. The hypermethylation of E-Cadherin and Cyclooxygenase 2 (COX-2) in chronic inflammation such as chronic periodontitis may demonstrate mild lesion/mutation epigenetic level. This study compares the hypermethylation status of E-Cadherin and COX-2 genes which are often found in breast cancer patients with that in chronic periodontitis.</p> <p>Methods</p> <p>Total DNA was extracted from the blood samples of 108 systemically healthy non-periodontitis subjects, and the gingival tissues and blood samples of 110 chronic periodontitis patient as well as neoplastic tissues of 106 breast cancer patients. Methylation-specific PCR for E-Cadherin and COX-2 was performed on these samples and the PCR products were analyzed on 2% agarose gel.</p> <p>Results</p> <p>Hypermethylation of E-Cadherin and COX-2 was observed in 38% and 35% of the breast cancer samples, respectively. In chronic periodontitis patients the detection rate was 25% and 19% respectively, and none was found in the systemically healthy non-periodontitis control subjects. The hypermethylation status was shown to be correlated among the three groups with statistical significance (p < 0.0001). The methylation of CpG islands in E-Cadherin and COX-2 genes in periodontitis patients occurs more frequently in periodontitis patients than in the control subjects, but occurs less frequently than in the breast cancer patients.</p> <p>Conclusions</p> <p>This set of data shows that the epigenetic change in E-Cadherin and Cyclooxygenase-2 is associated with chronic periodontitis. The epigenetic changes presented in chronic inflammation patients might demonstrate an irreversible destruction in the tissues or organs similar to the effects of cancer. Chronic periodontitis to some extent might be associated with DNA hypermethylation which is related to cancer risk factors.</p

A search for small noncoding RNAs in Staphylococcus aureus reveals a conserved sequence motif for regulation

Bioinformatic analysis of the intergenic regions of Staphylococcus aureus predicted multiple regulatory regions. From this analysis, we characterized 11 novel noncoding RNAs (RsaA‐K) that are expressed in several S. aureus strains under different experimental conditions. Many of them accumulate in the late-exponential phase of growth. All ncRNAs are stable and their expression is Hfq-independent. The transcription of several of them is regulated by the alternative sigma B factor (RsaA, D and F) while the expression of RsaE is agrA-dependent. Six of these ncRNAs are specific to S. aureus, four are conserved in other Staphylococci, and RsaE is also present in Bacillaceae. Transcriptomic and proteomic analysis indicated that RsaE regulates the synthesis of proteins involved in various metabolic pathways. Phylogenetic analysis combined with RNA structure probing, searches for RsaE‐mRNA base pairing, and toeprinting assays indicate that a conserved and unpaired UCCC sequence motif of RsaE binds to target mRNAs and prevents the formation of the ribosomal initiation complex. This study unexpectedly shows that most of the novel ncRNAs carry the conserved C−rich motif, suggesting that they are members of a class of ncRNAs that target mRNAs by a shared mechanism

Modeling Ice Shedding Propagation on Transmission Lines with or without Interphase Spacers

Ice shedding propagation on a single conductor and on a circuit of three conductors in a vertical configuration where conductors are linked with interphase spacers was modeled numerically. Several concentrated loads acting along the loaded span modeled the ice, and the shedding propagation was then simulated through the removal in a defined sequence of these concentrated loads. The model determines conductor displacement and the variation of conductor tension during the vibration following ice shedding propagation; and, thus, it predicts conductor rebound height, tension peak, and to what extent the conductor clearance is reduced during vibration. Ice shedding propagation on the full-scale test line of Hydro-Quebec was considered, and the model was validated by comparing simulation results to former experimental observations. The results show that the application of spacers reduces the severity of vibration considerably, and consequently increases the conductor clearance and reduces the risk of flashover. The dynamic effects of different shedding processes were also compared. The rebound height is the greatest for a single conductor when ice detachment propagates along the conductor, but then ice falls suddenly as a big chunk. However, the consequences of sudden detachment and shedding are obtained as the most severe when conductors are linked with spacers

Evaluation of power line cable fatigue parameters based on measurements on a laboratory cable test span

peer reviewedThe present paper describes experiments carried out on IREQ laboratory cable test bench. Test span arrangement is a 63.15m cable span with termination ends designed so as to minimize energy dissipation. A shaker provides a vertical alternating force to the conductor. During the experiments, a maximum of information on mode shape is collected: location of nodes, antinode amplitude of vibration, relative displacement at 44.5, 89, and 178mm from the last point of contact with the metallic clamp. Several configurations are studied: span equipped with an homogeneous steel cable, span equipped with an ACSR Crow conductor, sometimes in combination with other equipments such as a vibration damper or a local mass, to investigate how the presence of such devices impacts conductor vibrations. It results from these experiments an interesting comparison of two widely used fatigue indicators, the relative displacement Yb 2 (also called “bending amplitude”) and fymax (the product of antinode amplitude of vibration by frequency). Also, collected data gives indirect information on conductor variable bending stiffness

VIBRATIONS OF A SHORT SPAN, COMPARISON BETWEEN MODELIZATION AND MEASUREMENTS PERFORMED ON A LABORATORY TEST SPAN

peer reviewedIn the first part of the present paper, experiments carried out on IREQ laboratory cable test bench were described. One of the objectives of these experiments was to collect all the required data to validate the modelization of this cable test bench vibrating at its eigen frequencies. Conductor excitation was performed by a vibration shaker. In the present paper, the first modelization results are presented. The model used is a beam element model, with an average value of conductor bending stiffness. For certain of the simulations, some material damping was introduced through the use of a visco-elastic material. The vibration shaker is modelled by a harmonic force of adequate amplitude and location. The results obtained with this model put in evidence the impact of tension variations on such span length, which makes it difficult to obtain a resonance. Also, computed mode shapes are in good agreement with the reality, and time response of the model with a concentrated mass enabled us to reproduce some interesting observed phenomena

Galloping Conductors

The chapter describes galloping of overhead conductors. It includes an overview on the phenomenon, with information on its characteristics, types of galloping, damage resulting from it, and causes. The chapter also covers the mechanisms of galloping and reviews protection methods