Cycling of dissolved organic phosphorus compounds in natural waters

U.S. Department of the InteriorU.S. Geological SurveyOpe

Whole genome sequencing-based mapping and candidate identification of mutations from fixed zebrafish tissue

As forward genetic screens in zebrafish become more common, the number of mutants that cannot be identified by gross morphology or through transgenic approaches, such as many nervous system defects, has also increased. Screening for these difficult-to-visualize phenotypes demands techniques such as whole-mount in situ hybridization (WISH) or antibody staining, which require tissue fixation. To date, fixed tissue has not been amenable for generating libraries for whole genome sequencing (WGS). Here, we describe a method for using genomic DNA from fixed tissue and a bioinformatics suite for WGS-based mapping of zebrafish mutants. We tested our protocol using two known zebrafish mutant alleles, gpr126st49 and egr2bfh227, both of which cause myelin defects. As further proof of concept we mapped a novel mutation, stl64, identified in a zebrafish WISH screen for myelination defects. We linked stl64 to chromosome 1 and identified a candidate nonsense mutation in the F-box and WD repeat domain containing 7 (fbxw7) gene. Importantly, stl64 mutants phenocopy previously described fbxw7vu56 mutants, and knockdown of fbxw7 in wild-type animals produced similar defects, demonstrating that stl64 disrupts fbxw7. Together, these data show that our mapping protocol can map and identify causative lesions in mutant screens that require tissue fixation for phenotypic analysis

On the consistent solution of the gap--equation for spontaneously broken λΦ4\lambda \Phi^4-theory

We present a self--consistent solution of the finite temperature gap--equation for $\lambda \Phi^4$ theory beyond the Hartree-Fock approximation using a composite operator effective action. We find that in a spontaneously broken theory not only the so--called daisy and superdaisy graphs contribute to the resummed mass, but also resummed non--local diagrams are of the same order, thus altering the effective mass for small values of the latter.Comment: 15 pages of revtex + 3 uuencoded postscript figures, ENSLAPP A-488/9

BMQ

BMQ: Boston Medical Quarterly was published from 1950-1966 by the Boston University School of Medicine and the Massachusetts Memorial Hospitals. Pages 49-52, v17n2, provided courtesy of Howard Gotlieb Archival Research Center

Nonlinear lattice model of viscoelastic Mode III fracture

We study the effect of general nonlinear force laws in viscoelastic lattice models of fracture, focusing on the existence and stability of steady-state Mode III cracks. We show that the hysteretic behavior at small driving is very sensitive to the smoothness of the force law. At large driving, we find a Hopf bifurcation to a straight crack whose velocity is periodic in time. The frequency of the unstable bifurcating mode depends on the smoothness of the potential, but is very close to an exact period-doubling instability. Slightly above the onset of the instability, the system settles into a exactly period-doubled state, presumably connected to the aforementioned bifurcation structure. We explicitly solve for this new state and map out its velocity-driving relation

Relation between Barrier Conductance and Coulomb Blockade Peak Splitting for Tunnel-Coupled Quantum Dots

We study the relation between the barrier conductance and the Coulomb blockade peak splitting for two electrostatically equivalent dots connected by tunneling channels with bandwidths much larger than the dot charging energies. We note that this problem is equivalent to a well-known single-dot problem and present solutions for the relation between peak splitting and barrier conductance in both the weak and strong coupling limits. Results are in good qualitative agreement with the experimental findings of F. R. Waugh et al.Comment: 19 pages (REVTeX 3.0), 3 Postscript figure

Mean Field Theory of the Morphology Transition in Stochastic Diffusion Limited Growth

We propose a mean-field model for describing the averaged properties of a class of stochastic diffusion-limited growth systems. We then show that this model exhibits a morphology transition from a dense-branching structure with a convex envelope to a dendritic one with an overall concave morphology. We have also constructed an order parameter which describes the transition quantitatively. The transition is shown to be continuous, which can be verified by noting the non-existence of any hysteresis.Comment: 16 pages, 5 figure