Maintenance and degradation of proteins in intact and severed axons: Implications for the mechanism of long-term survival of anucleate crayfish axons

Protein maintenance and degradation are examined in the severed distal (anucleate) portions of crayfish medial giant axons (MGAs), which remain viable for over 7 months following axotomy. On polyacrylamide gels, the silver-stained protein banding pattern of anucleate MGAs severed from their cell bodies for up to 4 months remains remarkably similar to that of intact MGAs. At 7 months postseverance, some (but not all) proteins are decreased in anucleate MGAs compared to intact MGAs. To determine the half-life of axonally transported proteins, we radiolabeled MGA cell bodies and monitored the degradation of newly synthesized transported proteins. Assuming exponential decay, proteins in the fast component of axonal transport have an average half-life of 14 d in anucleate MGAs and proteins in the slow component have an average half-life of 17 d. Such half-lives are very unlikely to account for the ability of anucleate MGAs to survive for over 7 months after axotomy.This work was supported by an ATP grant to G.D.B.Neuroscienc

Moduli spaces of hyperbolic 3-manifolds and dynamics on character varieties

The space AH(M) of marked hyperbolic 3-manifold homotopy equivalent to a compact 3-manifold with boundary M sits inside the PSL_2(C)-character variety X(M) of \pi_1(M). We study the dynamics of the action of Out(\pi_1(M)) on both AH(M) and X(M). The nature of the dynamics reflects the topology of M. The quotient AI(M)=AH(M)/Out(\pi_1(M)) may naturally be thought of as the moduli space of unmarked hyperbolic 3-manifolds homotopy equivalent to M and its topology reflects the dynamics of the action

Plethodon elongatus

Number of Pages: 2Integrative BiologyGeological Science

Off-lattice Monte Carlo Simulation of Supramolecular Polymer Architectures

We introduce an efficient, scalable Monte Carlo algorithm to simulate cross-linked architectures of freely-jointed and discrete worm-like chains. Bond movement is based on the discrete tractrix construction, which effects conformational changes that exactly preserve fixed-length constraints of all bonds. The algorithm reproduces known end-to-end distance distributions for simple, analytically tractable systems of cross-linked stiff and freely jointed polymers flawlessly, and is used to determine the effective persistence length of short bundles of semi-flexible worm-like chains, cross-linked to each other. It reveals a possible regulatory mechanism in bundled networks: the effective persistence of bundles is controlled by the linker density.Comment: 4 pages, 4 figure

Search for the second forbidden beta decay of 8B to the ground state of 8Be

A significant decay branch of 8B to the ground state of 8Be would extend the solar neutrino spectrum to higher energies than anticipated in the standard solar models. These high-energy neutrinos would affect current neutrino oscillation results and also would be a background to measurements of the hep process. We have measured the delayed alpha particles from the decay of 8B, with the goal of observing the two 46-keV alpha particles arising from the ground-state decay. The 8B was produced using an in-flight radioactive beam technique. It was implanted in a silicon PIN-diode detector that was capable of identifying the alpha-particles from the 8Be ground state. From this measurement we find an upper limit (at 90% confidence level) of 7.3 x 10^{-5} for the branching ratio to the ground state. In addition to describing this measurement, we present a theoretical calculation for this branching ratio.Comment: One reference corrected. Minor edits in tex

In de voetsporen van de kritische boerin : 25 jaar Landelijke Boerinnen Belangen, 1983-2008

Het verhaal van 25 jaar Landelijke Boerinnen Belangen (LBB) geeft in een notendop weer hoe kritische boerinnen hun maatschappelijke betrokkenheid vormgaven. Gestimuleerd door de vrouwenbeweging merkten zij in de zeventig jaren van de vorige eeuw dat zij een andere positie hadden dan de meeste vrouwen. Zij waren niet alleen getrouwd met een man die boer van beroep was, maar ook met zijn bedrijf. Niet alleen economisch, maar ook sociaal waren gezin, huishouden en bedrijf zo met elkaar verweven, dat zij hun positie wel in samenhang moesten bekijken. De geschiedenis van LBB toont hun zoektocht naar de tot dan toe onderbelichte positie van vrouwen in de agrarische sector. Deze boerinnen lieten ook zien hoe het landbouwbeleid en de besluitvorming daarover samenhingen met de knelpunten en problemen die zij in de dagelijkse praktijk tegenkwamen. Zij experimenteerden in hun eigen praktijk, vertaalden hun visies naar beleidsalternatieven en brachten die onder de aandacht bij de landbouworganisaties en ministeries. Voor het eerst lieten boerinnen hun stem horen over landbouwzaken waar zij zich toentertijd verre van dienden te houden

Second Harmonic Generation from Phononic Epsilon-Near-Zero Berreman Modes in Ultrathin Polar Crystal Films

Immense optical field enhancement was predicted to occur for the Berreman mode in ultrathin films at frequencies in the vicinity of epsilon near zero (ENZ). Here, we report the first experimental proof of this prediction in the mid-infrared by probing the resonantly enhanced second harmonic generation (SHG) at the longitudinal optic phonon frequency from a deeply subwavelength-thin aluminum nitride (AlN) film. Employing a transfer matrix formalism, we show that the field enhancement is completely localized inside the AlN layer, revealing that the observed SHG signal of the Berreman mode is solely generated in the AlN film. Our results demonstrate that ENZ Berreman modes in intrinsically low-loss polar dielectric crystals constitute a promising platform for nonlinear nanophotonic applications