Possible interaction of interstellar particles with the solar and terrestrial environment

The possibility for detection of interstellar particles in the earth's environment is considered on the basis of the passage of the solar system through the interstellar medium. Among the forces which inhibit interstellar particle penetration, the deflection by the solar magnetic field and the repulsive force due to the radiation from the sun are by far the most important

Wave length dependence of polarization by small graphite flakes

Graphite polarization data for semi-quantitative estimation of interstellar radiation wave extinction by small graphite flake

A schistosome [beta] subunit remodels inactivation of a calcium channel _via_ an N-terminal polyacidic motif

The beta subunit of high voltage-activated Ca (Cav) channels targets the pore forming [alpha]~1~ subunit to the plasma membrane and defines the biophysical phenotype of the Cav channel complex. Cav channel inactivation following activation and opening is tightly regulated and is an essential property that not only prevents excessive entry of Ca^2+^ into the cell but may also have functions in signal transduction. The [beta] subunit modulates Ca^2+^-dependent and voltage-dependent components of Cav channel inactivation via its interaction with the I-II linker of the [alpha]~1~ subunit. Here, using Cav2.3 and whole-cell patch-clamp, we show that a [beta] subunit from the human parasite _Schistosoma mansoni_ ([beta]~Sm~) accelerates inactivation via a unique, long N-terminal polyacidic motif (NPAM). The accelerating effect of NPAM-containing subunits, both native ([beta]~Sm~)and chimeric mammalian [beta]~1b~, [beta]~2a~ and [beta]~3~ subunits to which NPAM had been attached, was only apparent when Ca^2+^ was internally buffered with BAPTA (5 mM) or when Ba^2+^ was used as the charge carrier, two commonly used strategies to eliminate Ca^2+^/calmodulin dependent inactivation. These results indicate that calmodulin is not involved. In addition to accelerating inactivation, NPAM-containing [beta] subunits significantly reduced current density with respect to their non NPAM-bearing counterparts. Interestingly, when the amino acids N terminal to NPAM were deleted, inactivation of Cav2.3 currents was faster than in the presence of the entire N-terminal portion of the [beta]~Sm~ subunit, as if the pre-NPAM region counteracts the effect of NPAM. Presence of NPAM also resulted in currents that activated faster, suggesting that NPAM increases open channel probability. However, NPAM does not modulate inactivation gating. In summary, this study identifies a structural determinant of Cav channel inactivation that is entirely unlike those previously known

Hope vs. Fear: The Debate Over a State Constitutional Convention

On November 7, 2017, New Yorkers will go to their polling places and receive ballots containing a thirteen-word referendum question: “Shall there be a convention to revise the constitution and amend the same?” That question appears on the ballot because the New York State Constitution commands that at least once every twenty years voters are asked whether or not to call a constitutional convention. The mandatory referendum reflects Thomas Jefferson’s belief that every generation the people should be given a chance to revise their basic law

On elliptic curves with an isogeny of degree 7

We show that if $E$ is an elliptic curve over $\mathbf{Q}$ with a $\mathbf{Q}$-rational isogeny of degree 7, then the image of the 7-adic Galois representation attached to $E$ is as large as allowed by the isogeny, except for the curves with complex multiplication by $\mathbf{Q}(\sqrt{-7})$. The analogous result with 7 replaced by a prime $p > 7$ was proved by the first author in [7]. The present case $p = 7$ has additional interesting complications. We show that any exceptions correspond to the rational points on a certain curve of genus 12. We then use the method of Chabauty to show that the exceptions are exactly the curves with complex multiplication. As a by-product of one of the key steps in our proof, we determine exactly when there exist elliptic curves over an arbitrary field $k$ of characteristic not 7 with a $k$-rational isogeny of degree 7 and a specified Galois action on the kernel of the isogeny, and we give a parametric description of such curves.Comment: The revision gives a complete answer to the question considered in Version 1. Version 3 will appear in the American Journal of Mathematic

Variational Principle in the Algebra of Asymptotic Fields

This paper proposes a variational principle for the solutions of quantum field theories in which the ``trial functions'' are chosen from the algebra of asymptotic fields, and illustrates this variational principle in simple cases.Comment: 15 pages, Latex, no figure

Fast accretion of small planetesimals by protoplanetary cores

We explore the dynamics of small planetesimals coexisting with massive protoplanetary cores in a gaseous nebula. Gas drag strongly affects the motion of small bodies leading to the decay of their eccentricities and inclinations, which are excited by the gravity of protoplanetary cores. Drag acting on larger ($\gtrsim 1$ km), high velocity planetesimals causes a mere reduction of their average random velocity. By contrast, drag qualitatively changes the dynamics of smaller ($\lesssim 0.1-1$ km), low velocity objects: (1) small planetesimals sediment towards the midplane of the nebula forming vertically thin subdisk; (2) their random velocities rapidly decay between successive passages of the cores and, as a result, encounters with cores typically occur at the minimum relative velocity allowed by the shear in the disk. This leads to a drastic increase in the accretion rate of small planetesimals by the protoplanetary cores, allowing cores to grow faster than expected in the simple oligarchic picture, provided that the population of small planetesimals contains more than roughly 1% of the solid mass in the nebula. Fragmentation of larger planetesimals ($\gtrsim 1$ km) in energetic collisions triggered by the gravitational scattering by cores can easily channel this amount of material into small bodies on reasonable timescales ($< 1$ Myr in the outer Solar System), providing a means for the rapid growth (within several Myr at 30 AU) of rather massive protoplanetary cores. Effects of inelastic collisions between planetesimals and presence of multiple protoplanetary cores are discussed.Comment: 17 pages, 8 figures, additional clarifications, 1 more figure and table adde

A sweep algorithm for massively parallel simulation of circuit-switched networks

A new massively parallel algorithm is presented for simulating large asymmetric circuit-switched networks, controlled by a randomized-routing policy that includes trunk-reservation. A single instruction multiple data (SIMD) implementation is described, and corresponding experiments on a 16384 processor MasPar parallel computer are reported. A multiple instruction multiple data (MIMD) implementation is also described, and corresponding experiments on an Intel IPSC/860 parallel computer, using 16 processors, are reported. By exploiting parallelism, our algorithm increases the possible execution rate of such complex simulations by as much as an order of magnitude