567 research outputs found
Gorillerde 0 Grubu Hiv'e Rastlandı
No full textKamerun''un güneyinde yaşayan gorillerde ilk kez AIDS virüsü HIV' in bir alt grubuna rastlandı. Araştırmacılar, özellikle Kamerun''da yaşayanlar olmak üzere Orta Afrika' nın batısındaki şempanzelerin insanlardakine benzeyen HIV-1 taşıdıklarını, ancak bu hayvanların virüs taşısalar da AIDS''e yakalanmadıklarını biliyordu. Ancak Kamerun' daki maymunların dışkılarını inceleyen araştırmacılar Martine Peeters ve Eric Delaporte ile arkadaşları, gorillere ait 6 örnekte HIV-1 antikoruna rastladı
Sixièmes actualités du Pharo : les grandes endémies en Afrique et communications libres en pathologie tropicale
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Performance Prediction of Cavitating Hydrofoil Sections
No full textHydrofoils can under certain circumstances cause a phase change from liquid water to water vapor. This phenomenon is called cavitation and is caused by the low pressure over the hydrofoil when the vessel exceeds a certain velocity though the water. Cavitation can take different forms depending the angle of attack α and the flow conditions which are characterized with the cavitation number σ . The different types of cavitation can have different effects on flow and loads.Computational Fluid Dynamics (CFD) is widely used in aero and hydrodynamic design, with (U)RANS most commonly used for CFD in the industry due to its relatively low computational cost while providing sufficiently accurate results. Cavitation models in URANS simulations need a multiphase framework in order to model the liquid/vapor interface of the cavitation bubbles. The Schnerr-Sauer cavitation model uses simplified bubble dynamics equations for relatively fast calculation while providing accurate results. In current project, a Volume of Fluid method is used the Schnerr-Sauer cavitation model is used with URANS CFD simulations to improve and enhance the behaviour and performance prediction of hydrofoils sections under cavitating conditions. Given the industrial context of this project, the simulations are conducted using constrained computational resources.Validation is performed for a non-cavitating test case using a NACA-0012 section, followed by validation for a cavitating test case using a modified NACA-66 section. Mesh convergence studies have been performed, turbulence models have been compared and the turbulent viscosity has been modified. The final set-up uses the SST turbulence model with a modified turbulent viscosity exponent n = 2.3. To assess the flow behavior and hydrofoil section performance under cavitating conditions, a comparison is made in CFD using cavitation models, relative to the current practice. This study shows that the lift and drag results for a simulation without cavitation model are underestimated compared to the simulation with cavitation model in conditions of stable cavitation. For conditions with unstable cavitation, strong unsteady disturbed flow and loads are found that are not captured by the simulation without cavitation model. The transition from stable to unstable cavitation is studied by investigating cavitation bubble length and itscorresponding fluctuation as a function of the stability parameter ps = σ/2(α−α0) . The conditions found for the transition from stable to unstable cavitation are consistent with reference value at about ps = 4. The inception of stable cavitation is found at about ps = 7 which is considered to be more optimized to delay the formation of cavitation compared to the NACA-0012 at ps = 8.5.The lift, drag and performance polars are studied for several values of σ . The lift and drag polars for lowerσ , i.e. higher cavitation rate, show a stronger increase in both lift and drag for stable cavitation cases. The performance (or Lift over Drag) is slightly increased at α = 4◦ for σ = 1.2 and 1. For higher angles of attack, the increase in drag surpasses the increase in lift and the performance decreases. These finding only hold the stable cavitation cases (α < 8◦ for all tested σ , and α = 6◦ for σ = 1) since the unstable cavitation results areinconclusive. The main limitation of the set-up developed in the current project is that the predictions show significant discrepancies in capturing the unstable bubble shedding characteristics, with respect to the reference data. As a result, the cloud cavitation shedding frequency is not accurately captured, resulting in an inadequate representation of vibrations and loading due to cloud cavitation.Aerospace Engineerin
Manson’s triple error
No full textThe author discusses the significance, implications and limitations of Manson’s work. How did Patrick Manson resolve some of the major problems raised by the filarial worm life cycle? The Amoy physician showed that circulating embryos could only leave the blood via the percutaneous route, thereby requiring a bloodsucking insect. The discovery of a new autonomous, airborne, active host undoubtedly had a considerable impact on the history of parasitology, but the way in which Manson formulated and solved the problem of the transfer of filarial worms from the body of the mosquito to man resulted in failure. This article shows how the epistemological transformation operated by Manson was indissociably related to a series of errors and how a major breakthrough can be the result of a series of false proposals and, consequently, that the history of truth often involves a history of error
Interferon-mediated changes in the expression of CYP1A1 in human B lymphoblastoid (AHH-1 TK +/-) cells
No full textThe expression of constitutive and inducible cytochrome P450s has been shown to be downregulated by interferon through an unknown pretranslational mechanism that depresses the mRNA encoding P450 apoproteins. To establish an association between gene transcription and P450 apoprotein downregulation by interferon, we studied the effect of recombinant interferon (IFN-alpha 2a) on CYP1A1 in human B lymphoblastoid cell lines. The cHoI cell line expresses inducible native CYP1A1, while the genetically engineered derivative h1A1 v2 expresses a noninducible extrachromosomal vector-derived human CYP1A1 cDNA lacking the CYP1A1 promoter region. We characterized CYP1A1 activity, apoprotein, and mRNA by ethoxyresorufin O-deethylase activity, Western immunoblotting, and Northern blot analysis, respectively. In cHoI cells, following induction with dibenz[a,h]anthracene, interferon depressed CYP1A1 apoprotein and mRNA levels by 55 and 76%, respectively, with no detectable changes in enzyme activity. In h1A1 v2, however, interferon increased CYP1A1 activity, apoprotein, and mRNA. The depression of CYP1A1 mRNA and apoprotein levels incHoI cells, in contrast with the increase observed in h1A1 v2 cells, suggests that nuclear mechanisms are essential for interferon-mediated depression of inducible P450s. From our preliminary results we propose that interferon-mediated downregulation of CYP1A1 may result from inhibition of gene transcription.LR: 20061115; PUBM: Print; JID: 0372712; 0 (Interferon-alpha); 0 (Recombinant Proteins); 9035-51-2 (Cytochrome P-450 Enzyme System); ppublishSource type: Electronic(1
Making Trauma Visible
No full textInternational audienceThe question of psychic trauma first arose in the late nineteenth and early twentieth century in the exchanges between Freud and Breuer. Thus, it was during these prewar years that the initial framework for understanding trauma was outlined. In a text published in 1895, Studies on Hysteria, Freud wrote: ``Psychical trauma\textendash or more precisely the memory of the trauma\textendash acts like a foreign body." He also highlighted the suffering endured by the patient when confronting reminiscences: ``The traumatic memory does not wear away'', adding: ``It must be abreacted." The theory of abreaction came a little later, in 1905, in the text entitled Psychical (Or Mental) Treatment, the mental treatment advocated by Freud being that of a ``treatment (whether of mental or physical disorders)[\ldots ] that uses words, the essential tool of mental treatment''. Freud goes on to evoke the ``magical power'' of words in this respect. His analytical technique as well as his concept of trauma thus gradually came to be defined in the course of these writings, nourished by the discussions he maintained with his main disciples: Ferenczi, Abraham and Jung. \textcopyright The Editor(s) and The Author(s) 2016
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