924 research outputs found
Explicit Formulas for Non-Geodesic Biharmonic Curves of the Heisenberg Group
We consider the biharmonicity condition for maps between Riemannian manifolds
(see [BK]), and study the non-geodesic biharmonic curves in the Heisenberg
group H_3. First we prove that all of them are helices, and then we obtain
explicitly their parametric equations.Comment: 16 pages, 2 figure
Entre connaissances implicites et processus explicites en intercompréhension écrite : peut-on réussir tous les transferts ?
International audienceLa mĂ©thodologie dĂ©veloppĂ©e dans la mĂ©thode Eurom5 (Ă©dition enrichie de la mĂ©thode EuRom4 (1997) rĂ©alisĂ©e entre autres par Claire Blanche-Benveniste) permet Ă des lecteurs experts en L1 romane de transfĂ©rer leur compĂ©tence dans plusieurs autres langues parentes peu ou pas connues. Le travail de recherche et les applications expĂ©rimentales menĂ©es durant plusieurs annĂ©es ont permis de rĂ©diger un protocole qui sâappuie sur lâexploitation de plusieurs types de stratĂ©gies relevant du processus de lecture et de comprĂ©hension. Pour chacun des paramĂštres qui entrent en jeu lorsquâil sâagit de comprendre un texte, nous proposons certaines voies facilitatrices tout en mentionnant les variables sur lesquelles faire porter une attention particuliĂšre. LâoriginalitĂ© de cette mĂ©thodologie est dâavoir traitĂ© la dimension grammaticale des langues comme une stratĂ©gie dâaccĂšs au sens
Constant mean curvature and totally umbilical biharmonic surfaces in 3-dimensional geometries
We prove that a totally umbilical biharmonic surface in any -dimensional
Riemannian manifold has constant mean curvature. We use this to show that a
totally umbilical surface in Thurston's 3-dimensional geometries is proper
biharmonic if and only if it is a part of in . We also
give complete classifications of constant mean curvature proper biharmonic
surfaces in 3-dimensional geometries and in 3-dimensional
Bianchi-Cartan-Vranceanu spaces, and a complete classifications of proper
biharmonic Hopf cylinders in 3-dimensional Bianchi-Cartan-Vranceanu spaces.Comment: 15 page
Thermal boundary resistance from transient nanocalorimetry: a multiscale modeling approach
The Thermal Boundary Resistance at the interface between a nanosized Al film
and an Al_{2}O_{3} substrate is investigated at an atomistic level. A room
temperature value of 1.4 m^{2}K/GW is found. The thermal dynamics occurring in
time-resolved thermo-reflectance experiments is then modelled via macro-physics
equations upon insertion of the materials parameters obtained from atomistic
simulations. Electrons and phonons non-equilibrium and spatio-temporal
temperatures inhomo- geneities are found to persist up to the nanosecond time
scale. These results question the validity of the commonly adopted lumped
thermal capacitance model in interpreting transient nanocalorimetry
experiments. The strategy adopted in the literature to extract the Thermal
Boundary Resistance from transient reflectivity traces is revised at the light
of the present findings. The results are of relevance beyond the specific
system, the physical picture being general and readily extendable to other
heterojunctions.Comment: 12 pages, 8 figure
MBOAT7 in liver and extrahepatic diseases
MBOAT7 is a protein anchored to endomembranes by several transmembrane domains. It has a catalytic dyad involved in remodelling of phosphatidylinositol with polyunsaturated fatty acids. Genetic variants in the MBOAT7 gene have been associated with the entire spectrum of non-alcoholic fatty liver (NAFLD), recently redefined as metabolic dysfunction-associated fatty liver disease (MAFLD) and, lately, steatotic liver disease (SLD), and to an increasing number of extrahepatic conditions. In this review, we will (a) elucidate the molecular mechanisms by which MBOAT7 loss-of-function predisposes to MAFLD and neurodevelopmental disorders and (b) discuss the growing number of genetic studies linking MBOAT7 to hepatic and extrahepatic diseases. MBOAT7 complete loss of function causes severe changes in brain development resulting in several neurological manifestations. Lower MBOAT7 hepatic expression at both the mRNA and protein levels, due to missense nucleotide polymorphisms (SNPs) in the locus containing the MBOAT7 gene, affects specifically metabolic and viral diseases in the liver from simple steatosis to hepatocellular carcinoma, and potentially COVID-19 disease. This body of evidence shows that phosphatidylinositol remodelling is a key factor for human health
On level line fluctuations of SOS surfaces above a wall
We study the low temperature D Solid-On-Solid model on
with zero boundary conditions and non-negative heights (a floor at height ).
Caputo et al. (2016) established that this random surface typically admits
either or many nested macroscopic level line
loops for an explicit ,
and its top loop has cube-root fluctuations: e.g., if
is the vertical displacement of from the bottom boundary point
, then over . It is believed that rescaling by
and by would yield a limit law of a diffusion on
. However, no nontrivial lower bound was known on for a fixed
(e.g., ), let alone on in , to
complement the bound on . Here we show a lower bound of the
predicted order : for every there exists such
that with probability at least
. The proof relies on the Ornstein--Zernike machinery due to
Campanino--Ioffe--Velenik, and a result of Ioffe, Shlosman and Toninelli (2015)
that rules out pinning in Ising polymers with modified interactions along the
boundary. En route, we refine the latter result into a Brownian excursion limit
law, which may be of independent interest.Comment: 48 pages, 2 figure
Bourâs theorem and helicoidal surfaces with constant mean curvature in the BianchiâCartanâVranceanu spaces
In this paper, we generalize a classical result of Bour concerning helicoidal surfaces in the three-dimensional Euclidean space R3 to the case of helicoidal surfaces in the Bianchiâ CartanâVranceanu (BCV) spaces, i.e., in the Riemannian 3-manifolds whose metrics have groups of isometries of dimension 4 or 6, except the hyperbolic one. In particular, we prove that in a BCV-space there exists a two-parameter family of helicoidal surfaces isometric to a given helicoidal surface; then, by making use of this two-parameter representation, we characterize helicoidal surfaces which have constant mean curvature, including the minimal ones
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