110 research outputs found
Role of boundary conditions in helicoidal flow collimation: Consequences for the von Kármán sodium dynamo experiment
International audienceWe present hydrodynamic and magnetohydrodynamic (MHD) simulations of liquid sodium flow with the PLUTO compressible MHD code to investigate influence of magnetic boundary conditions on the collimation of helicoidal motions. We use a simplified cartesian geometry to represent the flow dynamics in the vicinity of one cavity of a multiblades impeller inspired by those used in the Von-Kármán-sodium (VKS) experiment. We show that the impinging of the large-scale flow upon the impeller generates a coherent helicoidal vortex inside the blades, located at a distance from the upstream blade piloted by the incident angle of the flow. This vortex collimates any existing magnetic field lines leading to an enhancement of the radial magnetic field that is stronger for ferromagnetic than for conducting blades. The induced magnetic field modifies locally the velocity fluctuations, resulting in an enhanced helicity. This process possibly explains why dynamo action is more easily triggered in the VKS experiment when using soft iron impellers
Mg-based materials diminish tumor spreading and cancer metastases
Cancer metastases are the most common causes of cancer-related deaths. The formation of secondary tumors at different sites in the human body can impair multiple organ function and dramatically decrease the survival of the patients. In this stage, it is difficulty to treat tumor growth and spreading due to arising therapy resistances. Therefore, it is important to prevent cancer metastases and to increase subsequent cancer therapy success. Cancer metastases are conventionally treated with radiation or chemotherapy. However, these treatments elicit lots of side effects, wherefore novel local treatment approaches are currently discussed. Recent studies already showed anticancer activity of specially designed degradable magnesium (Mg) alloys by reducing the cancer cell proliferation. In this work, we investigated the impact of these Mg-based materials on different steps of the metastatic cascade including cancer cell migration, invasion, and cancer-induced angiogenesis. Both, Mg and Mg-6Ag reduced cell migration and invasion of osteosarcoma cells in coculture with fibroblasts. Furthermore, the Mgbased materials used in this study diminished the cancer-induced angiogenesis. Endothelial cells incubated with conditioned media obtained from these Mg and Mg-6Ag showed a reduced cell layer permeability, a reduced proliferation and inhibited cell migration. The tube formation as a last step of angiogenesis was stimulated with the presence of Mg under normoxia and diminished under hypoxia
Extensive collection of femtoliter pad secretion droplets in beetle Leptinotarsa decemlineata allows nanoliter microrheology
Pads of beetles are covered with long, deformable setae, each ending in a
micrometric terminal plate coated with secretory fluid. It was recently shown
that the layer of the pad secretion covering the terminal plates is responsible
for the generation of strong attractive forces. However, less is known about
the fluid itself because it is produced in extremely small quantity. We here
present a first experimental investigation of the rheological properties of the
pad secretion in the Colorado potato beetle {\it Leptinotarsa decemlineata}.
Because the secretion is produced in an extremely small amount at the level of
the terminal plate, we first develop a procedure based on capillary effects to
collect the secretion. We then manage to incorporate micrometric beads,
initially in the form of a dry powder, and record their thermal motion to
determine the mechanical properties of the surrounding medium. We achieve such
a quantitative measurement within the collected volume, much smaller than the
l sample volume usually required for this technique. Surprisingly,
the beetle secretion was found to behave as a purely viscous liquid, of high
viscosity. This suggests that no specific complex fluid behaviour is needed
during beetle locomotion. We build a scenario for the contact formation between
the spatula at the setal tip and a substrate, during the insect walk. We show
that the attachment dynamics of the insect pad computed from the high measured
viscosity is in good agreement with observed insect pace. We finally discuss
the consequences of the secretion viscosity on the insect adhesion
Scaling laws and vortex profiles in 2D decaying turbulence
We use high resolution numerical simulations over several hundred of turnover
times to study the influence of small scale dissipation onto vortex statistics
in 2D decaying turbulence. A self-similar scaling regime is detected when the
scaling laws are expressed in units of mean vorticity and integral scale, as
predicted by Carnevale et al., and it is observed that viscous effects spoil
this scaling regime. This scaling regime shows some trends toward that of the
Kirchhoff model, for which a recent theory predicts a decay exponent .
In terms of scaled variables, the vortices have a similar profile close to a
Fermi-Dirac distribution.Comment: 4 Latex pages and 4 figures. Submitted to Phys. Rev. Let
Aging dynamics in a colloidal glass of Laponite
The aging dynamics of colloidal suspensions of Laponite, a synthetic clay, is
investigated using dynamic light stattering (DLS) and viscometry after a quench
into the glassy phase. DLS allows to follow the diffusion of Laponite particles
and reveals that there are two modes of relaxation. The fast mode corresponds
to a rapid diffusion of particles within "cages" formed by the neighboring
particles. The slow mode corresponds to escape from the cages: its average
relaxation time increases exponentially fast with the age of the glass. In
addition, the slow mode has a broad distribution of relaxation times, its
distribution becoming larger as the system ages. Measuring the concomitant
increase of viscosity as the system ages, we can relate the slowing down of the
particle dynamics to the viscosity.Comment: 9 pages, 8 Postscript figures, submitted to Phys. Rev.
Xenobiotic CAR activators induce Dlk1-Dio3 locus non-coding RNA expression in mouse liver
Predicting the impact of human exposure to chemicals such as pharmaceuticals and
agrochemicals requires the development of reliable and predictive biomarkers
suitable for the detection of early events potentially leading to adverse outcomes. In
particular, drug-induced non-genotoxic carcinogenesis (NGC) during preclinical
development of novel therapeutics intended for chronic administration in humans is a
major challenge for drug safety.
We previously demonstrated Constitutive Androstane Receptor (CAR) and WNT
signaling-dependent up-regulation of the pluripotency associated Dlk1-Dio3 imprinted
gene cluster non-coding RNAs (ncRNAs) in the liver of mice treated with tumorpromoting
doses of phenobarbital (PB). Here, to explore the sensitivity and the
specificity of this candidate liver tumor promotion ncRNAs signature we compared
phenotypic, transcriptional and proteomic data from wild-type, CAR/PXR double
knock-out and CAR/PXR double humanized animals treated with tumor-promoting
doses of PB or chlordane, both well-established CAR activators. We further
investigated selected transcriptional profiles from mouse liver samples exposed to
seven NGC compounds working through different mode of actions, overall
suggesting CAR-activation specificity of the Dlk1-Dio3 long ncRNAs activation. We
propose that Dlk1-Dio3 long ncRNAs up-regulation is an early CAR-activation
dependent transcriptional signature during xenobiotic-induced mouse liver tumor
promotion. This signature may further contribute mode of action-based ‘weight of
evidence’ cancer risk assessment for xenobiotic-induced rodent liver tumors
Postnatal Growth after Intrauterine Growth Restriction Alters Central Leptin Signal and Energy Homeostasis
Intrauterine growth restriction (IUGR) is closely linked with metabolic diseases, appetite disorders and obesity at adulthood. Leptin, a major adipokine secreted by adipose tissue, circulates in direct proportion to body fat stores, enters the brain and regulates food intake and energy expenditure. Deficient leptin neuronal signalling favours weight gain by affecting central homeostatic circuitry. The aim of this study was to determine if leptin resistance was programmed by perinatal nutritional environment and to decipher potential cellular mechanisms underneath
Quantum cascade laser frequency stabilisation at the sub-Hz level
Quantum Cascade Lasers (QCL) are increasingly being used to probe the
mid-infrared "molecular fingerprint" region. This prompted efforts towards
improving their spectral performance, in order to reach ever-higher resolution
and precision. Here, we report the stabilisation of a QCL onto an optical
frequency comb. We demonstrate a relative stability and accuracy of 2x10-15 and
10-14, respectively. The comb is stabilised to a remote near-infrared
ultra-stable laser referenced to frequency primary standards, whose signal is
transferred via an optical fibre link. The stability and frequency traceability
of our QCL exceed those demonstrated so far by two orders of magnitude. As a
demonstration of its capability, we then use it to perform high-resolution
molecular spectroscopy. We measure absorption frequencies with an 8x10-13
relative uncertainty. This confirms the potential of this setup for ultra-high
precision measurements with molecules, such as our ongoing effort towards
testing the parity symmetry by probing chiral species
Long-Term Alterations of Cytokines and Growth Factors Expression in Irradiated Tissues and Relation with Histological Severity Scoring
PURPOSE: Beside its efficacy in cancer treatment, radiotherapy induces degeneration of healthy tissues within the irradiated area. The aim of this study was to analyze the variations of proinflammatory (IL-1α, IL-2, IL-6, TNF-α, IFN-γ), profibrotic (TGF-β1), proangiogneic (VEGF) and stem cell mobilizing (GM-CSF) cytokines and growth factors in an animal model of radiation-induced tissue degeneration. MATERIALS AND METHODS: 24 rats were irradiated unilaterally on the hindlimb at a monodose of 30 Gy. Six weeks (n=8), 6 months (n=8) and 1 year (n=8) after irradiation the mediators expression in skin and muscle were analyzed using Western blot and the Bio-Plex® protein array (BPA) technology. Additional histological severity for fibrosis, inflammation, vascularity and cellularity alterations scoring was defined from histology and immnunohistochemistry analyses. RESULTS: A significant increase of histological severity scoring was found in irradiated tissue. Skin tissues were more radio-sensitive than muscle. A high level of TGF-β1 expression was found throughout the study and a significant relation was evidenced between TGF-β1 expression and fibrosis scoring. Irradiated tissue showed a chronic inflammation (IL-2 and TNF-α significantly increased). Moreover a persistent expression of GM-CSF and VEGF was found in all irradiated tissues. The vascular score was related to TGF-β1 expression and the cellular alterations score was significantly related with the level of IL-2, VEGF and GM-CSF. CONCLUSION: The results achieved in the present study underline the complexity and multiplicity of radio-induced alterations of cytokine network. It offers many perspectives of development, for the comprehension of the mechanisms of late injuries or for the histological and molecular evaluation of the mode of action and the efficacy of rehabilitation techniques
Congelación de alimentos bajo alta presión
La OTRI del Centro Tecnológico Nacional de la Conserva y Alimentación junto con la OTT del Consejo Superior de Investigaciones Científicas, colaboran en el Proyecto AGROCSIC, el cual fue aprobado por el Ministerio de Ciencia y Tecnología y financiado por el Ministerio de Educación y Ciencia. El objetivo principal de esta nueva actuación es estudiar las distintas líneas de trabajo de los Centros del CSIC relacionadas con la alimentación, para transferir sus resultados al sector industrial.El empleo de altas presiones en tecnología de alimentos, se remonta a 1899, Hite realizó ensayos con alta presión en leche para intentar incrementar su conservación reduciendo la microflora. Sin enbargo en
aquella época no era posible este método en la industria, por lo que sus trabajos fueron olvidados hasta 1989 cuando el Ministerio de Agricultura japonés con empresas de ingeniería y alimentación formó la "Asociación para la Investigación y Desarrollo de la tecnología de altas presiones" en la industria alimentaria.Este trabajo ha sido financiado mediante
el proyecto español "Plan Nacional de I+D+I (2003-2006) MCYT, AGL 2003-06862-C02-01/ALI project; y por el proyecto de la Comisión de la UE, RTD programa "Quality of Life and Management of Living Resources", proyecto
QLK1-CT-2002-D2230.Peer reviewe
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