1,880 research outputs found
NDM-525: EFFECTS OF TORNADO WIND SPEEDS ON CONCRETE ROAD BARRIERS
Wind speeds can be difficult to measure during tornadoes due to their destructive nature. They pose a significant threat to lives and infrastructure in many parts of Canada and the U.S. The Enhanced-Fujita scale focuses on estimating these wind speeds by observing damage to different types of buildings, but significantly less research has been performed on the damage of other structures. Learning more about the effects of high wind speeds on these structures will help improve the ease and accuracy of future tornado classification. A wind tunnel study was performed at the Boundary Layer Wind Tunnel Laboratory of Western University. The study focusses on estimating the wind speeds that cause overturning in a standard 32” concrete “Jersey” barrier. On April 27, 2014, an EF4 Tornado struck Mayflower, Arkansas, and among the damage, several of these concrete barriers were blown over during the storm. The goal of this study was to find the overturning wind velocity and compare it to other damage in this event. This study was performed by placing a 1:8 scale-model of these barriers in a wind tunnel at a variety of orientations and wind speeds. Through analysis, it was determined that an instantaneous wind velocity of 4.55 to 4.85 m/s would cause overturning. These values correspond to an instantaneous wind speed of 340-360 km/h at full scale. It was estimated that the 3-second gust (used for EF rating) was 300-320 km/h, which sits at the top of the 267-322 km/h classification range for an EF4 tornado
Kick stability in groups and dynamical systems
We consider a general construction of ``kicked systems''. Let G be a group of
measure preserving transformations of a probability space. Given its
one-parameter/cyclic subgroup (the flow), and any sequence of elements (the
kicks) we define the kicked dynamics on the space by alternately flowing with
given period, then applying a kick. Our main finding is the following stability
phenomenon: the kicked system often inherits recurrence properties of the
original flow. We present three main examples. 1) G is the torus. We show that
for generic linear flows, and any sequence of kicks, the trajectories of the
kicked system are uniformly distributed for almost all periods. 2) G is a
discrete subgroup of PSL(2,R) acting on the unit tangent bundle of a Riemann
surface. The flow is generated by a single element of G, and we take any
bounded sequence of elements of G as our kicks. We prove that the kicked system
is mixing for all sufficiently large periods if and only if the generator is of
infinite order and is not conjugate to its inverse in G. 3) G is the group of
Hamiltonian diffeomorphisms of a closed symplectic manifold. We assume that the
flow is rapidly growing in the sense of Hofer's norm, and the kicks are
bounded. We prove that for a positive proportion of the periods the kicked
system inherits a kind of energy conservation law and is thus superrecurrent.
We use tools of geometric group theory and symplectic topology.Comment: Latex, 40 pages, revised versio
Exact Lagrangian submanifolds in simply-connected cotangent bundles
We consider exact Lagrangian submanifolds in cotangent bundles. Under certain
additional restrictions (triviality of the fundamental group of the cotangent
bundle, and of the Maslov class and second Stiefel-Whitney class of the
Lagrangian submanifold) we prove such submanifolds are Floer-cohomologically
indistinguishable from the zero-section. This implies strong restrictions on
their topology. An essentially equivalent result was recently proved
independently by Nadler, using a different approach.Comment: 28 pages, 3 figures. Version 2 -- derivation and discussion of the
spectral sequence considerably expanded. Other minor change
Regulation of Motor Function and Behavior by Atypical Chemokine Receptor 1
The final publication is available at Springer via http://dx.doi.org/10.1007/s10519-014-9665-7Atypical Chemokine Receptor 1 (ACKR1), previously known as the Duffy Antigen Receptor for Chemokines, stands out among chemokine receptors for its high selective expression on Purkinje cells of the cerebellum, consistent with the ability of ACKR1 ligands to activate Purkinje cells in vitro. Nevertheless, evidence for ACKR1 regulation of brain function in vivo has been lacking. Here we demonstrate that Ackr1−/− mice have markedly impaired balance and ataxia when placed on a rotating rod and increased tremor when injected with harmaline, a drug that induces whole-body tremor by activating Purkinje cells. Ackr1−/− mice also exhibited impaired exploratory behavior, increased anxiety-like behavior and frequent episodes of marked hypoactivity under low-stress conditions. The behavioral phenotype of Ackr1−/− mice was the opposite of the phenotype occurring in mice with cerebellar degeneration and the defects persisted when Ackr1 was deficient only on non-hematopoietic cells. We conclude that normal motor function and behavior depend in part on negative regulation of Purkinje cell activity by Ackr1
A Model-based Approach for Fast Vehicle Detection in Continuously Streamed Urban LIDAR Point Clouds
Detection of vehicles in crowded 3-D urban scenes is a challenging problem in many computer vision related research fields, such as robot perception, autonomous driving, self-localization, and mapping. In this paper we present a model-based approach to solve the recognition problem from 3-D range data. In particular, we aim to detect and recognize vehicles from continuously streamed LIDAR point cloud sequences of a rotating multi-beam laser scanner. The end-to-end pipeline of our framework working on the raw streams of 3-D urban laser data consists of three steps 1) producing distinct groups of points which represent different urban objects 2) extracting reliable 3-D shape descriptors specifically designed for vehicles, considering the need for fast processing speed 3) executing binary classification on the extracted descriptors in order to perform vehicle detection. The extraction of our efficient shape
descriptors provides a significant speedup with and increased detection
accuracy compared to a PCA based 3-D bounding box fitting method
used as baseline
The homotopy type of the loops on -connected -manifolds
For we compute the homotopy groups of -connected closed
manifolds of dimension . Away from the finite set of primes dividing
the order of the torsion subgroup in homology, the -local homotopy groups of
are determined by the rank of the free Abelian part of the homology.
Moreover, we show that these -local homotopy groups can be expressed as a
direct sum of -local homotopy groups of spheres. The integral homotopy type
of the loop space is also computed and shown to depend only on the rank of the
free Abelian part and the torsion subgroup.Comment: Trends in Algebraic Topology and Related Topics, Trends Math.,
Birkhauser/Springer, 2018. arXiv admin note: text overlap with
arXiv:1510.0519
Amplitude of the Electrical Potential Oscillations in the Salt-Water Oscillator
The amplitude of the electrical potential oscillations of the salt water oscillator depends on the character of an electrical double layer formed in the glass capillary or at the interface between the dilute and concentrated salt solutions. When a stationary mercury electrode was used, a new type of periodic behavior, compound oscillation, was observed
Authigenic iron oxide proxies for marine zinc over geological time and implications for eukaryotic metallome evolution
Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Geobiology 11 (2013): 295-306, doi:10.1111/gbi.12036.Here we explore enrichments in paleomarine Zn as recorded by authigenic iron oxides
including Precambrian iron formations, ironstones and Phanerozoic hydrothermal
exhalites. This compilation of new and literature-based iron formation analyses track
dissolved Zn abundances and constrain the magnitude of the marine reservoir over
geological time. Overall, the iron formation record is characterized by a fairly static range
in Zn/Fe ratios throughout the Precambrian, consistent with the shale record (Scott et al.,
2013, Nature Geoscience, 6, 125-128). When hypothetical partitioning scenarios are
applied to this record, paleomarine Zn concentrations within about an order of magnitude
of modern are indicated. We couple this examination with new chemical speciation
models used to interpret the iron formation record. We present two scenarios: first, under
all but the most sulfidic conditions and with Zn binding organic ligand concentrations
similar to modern oceans, the amount of bioavailable Zn remained relatively unchanged
through time. Late proliferation of Zn in eukaryotic metallomes has previously been
linked to marine Zn biolimitation, but under this scenario, the expansion in eukaryotic Zn
metallomes may be better linked to biologically intrinsic evolutionary factors. In this case
zinc’s geochemical and biological evolution may be decoupled, and viewed as a function
of increasing need for genome regulation and diversification of Zn-binding transcription
factors. In the second scenario, we consider Archean organic ligand complexation in such
excess that it may render Zn bioavailability low. However, this is dependent on Zn
organic ligand complexes not being bioavailable, which remains unclear. In this case,
although bioavailability may be low, sphalerite precipitation is prevented, thereby
maintaining a constant Zn inventory throughout both ferruginous and euxinic conditions.
These results provide new perspectives and constraints 50 on potential couplings between
the trajectory of biological and marine geochemical coevolution.This work was supported by a NSERC Discovery
Grant to KOK, a NSERC PDF to SVL, a NSERC CGSM to LJR, and an NSF-EAR-PDF
to NJP. MAS acknowledges support from the Gordon and Betty Moore Foundation Grant
#2724. This work was also supported by grants from the Deutsche
Forschungsgemeinschaft (DFG) to A.K. (KA 1736/4-1 and 12-1)
The future is now: Model-based clinical trial design for Alzheimer's disease
Failures in trials for Alzheimer's disease (AD) may be attributable to inadequate dosing, population selection, drug inefficacy, or insufficient design optimization. The Coalition Against Major Diseases (CAMD) was formed in 2008 to develop drug development tools (DDT) to expedite drug development for AD and Parkinson's disease.1 CAMD led a process that successfully advanced a clinical trial simulation (CTS) tool for AD through the formal regulatory review process at the US Food and Drug Administration (FDA) and European Medicines Agency (EMA)
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