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 Tecnología. Laboratorio de Oncología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alonso, Daniel Fernando. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Oncología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; 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 $\mathcal{P}_N(K,\lambda)$ that a large $N \times N$ adjacency matrix of sparse random graphs has $K$ eigenvalues below a threshold $\lambda$. The method allows to determine, in principle, all moments of $\mathcal{P}_N(K,\lambda)$, 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 $N \gg 1$ for $|\lambda| > 0$, 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 $\lambda$. These results contrast with rotationally invariant random matrices, where the index variance scales only as $\ln N$, with an universal prefactor that is independent of $\lambda$. 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