17,547 research outputs found
Reciprocal interactions between tumor and endothelial cells: Effects of selective vasopressin V2 receptor peptide agonists
Recent experimental evidence suggested that the synthetic peptide desmopressin (DDAVP) interferes tumor angiogenesis by inducing the formation of angiostatin. It is also known that DDAVP stimulates the endothelial release of von Willebrand factor, a key element in resistance to metastasis. Vasopressin V2 receptor agonists such as DDAVP seem to evoke dual angiostatic and antimetastatic effects, breaking cooperative interactions of tumor and endothelial cells during tumor progression.Fil: Garona, Juan. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de OncologĂa Molecular; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Alonso, Daniel Fernando. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de OncologĂa Molecular; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentin
Biomechanics of hearing in katydids
Animals have evolved a vast diversity of mechanisms to detect sounds. Auditory
organs are used to detect intraspecific communicative signals and environmental
sounds relevant to survival. To hear, terrestrial animals must convert the acoustic
energy contained in the airborne sound pressure waves into neural signals. In
mammals, spectral quality is assessed by the decomposition of incoming sound waves
into elementary frequency components using a sophisticated cochlear system. Some
neotropical insects like katydids (bushcrickets) have evolved biophysical mechanisms
for auditory processing that are remarkably equivalent to those of mammals. Located
on their front legs, katydid ears are small, yet are capable of performing several of the
tasks usually associated with mammalian hearing. These tasks include air-to-liquid
impedance conversion, signal amplification, and frequency analysis. Impedance
conversion is achieved by a lever system, a mechanism functionally analogous to the
mammalian middle ear ossicles, yet morphologically distinct. In katydids, the exact
mechanisms supporting frequency analysis seem diverse, yet are seen to result in
dispersive wave propagation phenomenologically similar to that of cochlear systems.
Phylogenetically unrelated, katydids and tetrapods have evolved remarkably different
structural solutions to common biophysical problems. Here, we discuss the biophysics
of hearing in katydids and the variations observed across different species
Scalar-Vector Bootstrap
We work out all of the details required for implementation of the conformal
bootstrap program applied to the four-point function of two scalars and two
vectors in an abstract conformal field theory in arbitrary dimension. This
includes a review of which tensor structures make appearances, a construction
of the projectors onto the required mixed symmetry representations, and a
computation of the conformal blocks for all possible operators which can be
exchanged. These blocks are presented as differential operators acting upon the
previously known scalar conformal blocks. Finally, we set up the bootstrap
equations which implement crossing symmetry. Special attention is given to the
case of conserved vectors, where several simplifications occur.Comment: 76 pages, v3 moved several details into appendices, expanded
discussion of mixed symmetry projecto
Index statistical properties of sparse random graphs
Using the replica method, we develop an analytical approach to compute the
characteristic function for the probability that a
large adjacency matrix of sparse random graphs has eigenvalues
below a threshold . The method allows to determine, in principle, all
moments of , from which the typical sample to sample
fluctuations can be fully characterized. For random graph models with localized
eigenvectors, we show that the index variance scales linearly with
for , with a model-dependent prefactor that can be exactly
calculated. Explicit results are discussed for Erd\"os-R\'enyi and regular
random graphs, both exhibiting a prefactor with a non-monotonic behavior as a
function of . These results contrast with rotationally invariant
random matrices, where the index variance scales only as , with an
universal prefactor that is independent of . Numerical diagonalization
results confirm the exactness of our approach and, in addition, strongly
support the Gaussian nature of the index fluctuations.Comment: 10 pages, 5 figure
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