9,280 research outputs found
Hydrogen bonding in substituted nitroanilines : isolated nets in 1,3-diamino-4-nitrobenzene and continuously interwoven nets in 3,5-dinitroaniline
Peer reviewedPublisher PD
Invariant Peano curves of expanding Thurston maps
We consider Thurston maps, i.e., branched covering maps
that are postcritically finite. In addition, we assume that is expanding in
a suitable sense. It is shown that each sufficiently high iterate of
is semi-conjugate to , where is equal to the
degree of . More precisely, for such an we construct a Peano curve
(onto), such that
(for all ).Comment: 63 pages, 12 figure
An amphipathic helix enables septins to sense micrometer-scale membrane curvature
© The Authors, 2019. This article is distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 4.0 International License. The definitive version was published in Journal of Cell Biology (2019), doi:10.1083/jcb.201807211.Cell shape is well described by membrane curvature. Septins are filament-forming, GTP-binding proteins that assemble on positive, micrometer-scale curvatures. Here, we examine the molecular basis of curvature sensing by septins. We show that differences in affinity and the number of binding sites drive curvature-specific adsorption of septins. Moreover, we find septin assembly onto curved membranes is cooperative and show that geometry influences higher-order arrangement of septin filaments. Although septins must form polymers to stay associated with membranes, septin filaments do not have to span micrometers in length to sense curvature, as we find that single-septin complexes have curvature-dependent association rates. We trace this ability to an amphipathic helix (AH) located on the C-terminus of Cdc12. The AH domain is necessary and sufficient for curvature sensing both in vitro and in vivo. These data show that curvature sensing by septins operates at much smaller length scales than the micrometer curvatures being detected.We thank the Gladfelter laboratory and Danny Lew for useful discussions, Matthias Garten for ideas in setting up the rod assay, and the University of North Carolina EM facility (Victoria Madden and Kristen White) for support with scanning electron microscope.
This work was supported by a Howard Hughes Medical Institute Faculty Scholars award to A.S. Gladfelter, and K.S. Cannon was supported in part by a grant from the National Institute of General Medical Sciences under award T32 GM119999.2019-07-0
Plans for phase coherent long baseline interferometry for geophysical applications using the Anik-B communications satellite
A pilot project to establish an operational phase stable very long baseline interferometer (VLBI) for geophysical studies is described. Methods for implementation as well as practical applications are presented
AGC 226067: A possible interacting low-mass system
We present Arecibo, GBT, VLA and WIYN/pODI observations of the ALFALFA source
AGC 226067. Originally identified as an ultra-compact high velocity cloud and
candidate Local Group galaxy, AGC 226067 is spatially and kinematically
coincident with the Virgo cluster, and the identification by multiple groups of
an optical counterpart with no resolved stars supports the interpretation that
this systems lies at the Virgo distance (D=17 Mpc). The combined observations
reveal that the system consists of multiple components: a central HI source
associated with the optical counterpart (AGC 226067), a smaller HI-only
component (AGC 229490), a second optical component (AGC 229491), and extended
low surface brightness HI. Only ~1/4 of the single-dish HI emission is
associated with AGC 226067; as a result, we find M_HI/L_g ~ 6 Msun/Lsun, which
is lower than previous work. At D=17 Mpc, AGC 226067 has an HI mass of 1.5 x
10^7 Msun and L_g = 2.4 x 10^6 Lsun, AGC 229490 (the HI-only component) has
M_HI = 3.6 x 10^6 Msun, and AGC 229491 (the second optical component) has L_g =
3.6 x 10^5 Lsun. The nature of this system of three sources is uncertain: AGC
226067 and AGC 229490 may be connected by an HI bridge, and AGC 229490 and AGC
229491 are separated by only 0.5'. The current data do not resolve the HI in
AGC 229490 and its origin is unclear. We discuss possible scenarios for this
system of objects: an interacting system of dwarf galaxies, accretion of
material onto AGC 226067, or stripping of material from AGC 226067.Comment: Accepted for publication in A&A. 6 pages, 4 figure
Elementary amenable subgroups of R. Thompson's group F
The subgroup structure of Thompson's group F is not yet fully understood. The
group F is a subgroup of the group PL(I) of orientation preserving, piecewise
linear self homeomorphisms of the unit interval and this larger group thus also
has a poorly understood subgroup structure. It is reasonable to guess that F is
the "only" subgroup of PL(I) that is not elementary amenable. In this paper, we
explore the complexity of the elementary amenable subgroups of F in an attempt
to understand the boundary between the elementary amenable subgroups and the
non-elementary amenable. We construct an example of an elementary amenable
subgroup up to class (height) omega squared, where omega is the first infinite
ordinal.Comment: 20 page
Early Advanced LIGO binary neutron-star sky localization and parameter estimation
2015 will see the first observations of Advanced LIGO and the start of the
gravitational-wave (GW) advanced-detector era. One of the most promising
sources for ground-based GW detectors are binary neutron-star (BNS)
coalescences. In order to use any detections for astrophysics, we must
understand the capabilities of our parameter-estimation analysis. By simulating
the GWs from an astrophysically motivated population of BNSs, we examine the
accuracy of parameter inferences in the early advanced-detector era. We find
that sky location, which is important for electromagnetic follow-up, can be
determined rapidly (~5 s), but that sky areas may be hundreds of square
degrees. The degeneracy between component mass and spin means there is
significant uncertainty for measurements of the individual masses and spins;
however, the chirp mass is well measured (typically better than 0.1%).Comment: 4 pages, 2 figures. Published in the proceedings of Amaldi 1
Progress on the Low-Latency Inspiral Gravitational Wave Detection algorithm known as SPIIR
Low-latency event triggers to signify the presence of gravitational waves from coalescing binaries will be required to make prompt electromagnetic follow-up observations of electromagnetic counterparts. We present the recent progress made on implementing the time-domain low-latency detection algorithm known as summed parallel infinite impulse response (SPIIR) filtering into a real gravitational wave search pipeline
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