4,550 research outputs found
Potential distribution of a new Bacillus species causing anthrax in African rainforests
This presentation was given as part of the GIS Day@KU symposium on November 14, 2018. For more information about GIS Day@KU activities, please see http://gis.ku.edu/gisday/2018/PLATINUM SPONSORS:
KU Department of Geography and Atmospheric Science
KU Institute for Policy & Social Research
GOLD SPONSORS:
KU Libraries
State of Kansas Data Access & Support Center (DASC)
SILVER SPONSORS:
Bartlett & West
Kansas Applied Remote Sensing Program
KU Center for Global and International Studies
BRONZE SPONSORS:
Boundles
Condensates and quasiparticles in inflationary cosmology: mass generation and decay widths
During de Sitter inflation massless particles of minimally coupled scalar
fields acquire a mass and a decay width thereby becoming \emph{quasiparticles}.
For bare massless particles non-perturbative infrared radiative corrections
lead to a self-consistent generation of mass, for a quartic self interaction , and for a cubic self-interaction the mass is induced
by the formation of a non-perturbative \emph{condensate} leading to . These radiatively generated masses restore de Sitter
invariance and result in anomalous scaling dimensions of superhorizon
fluctuations. We introduce a generalization of the non-perturbative
Wigner-Weisskopf method to obtain the time evolution of quantum states that
include the self-consistent generation of mass and regulate the infrared
behavior. The infrared divergences are manifest as poles in
in the single particle self-energies, leading to a re-arrangement of the
perturbative series non-analytic in the couplings. A set of simple rules that
yield the leading order infrared contributions to the decay width are obtained
and implemented. The lack of kinematic thresholds entail that all particle
states acquire a decay width, dominated by the emission and absorption of
superhorizon quanta for cubic and quartic couplings respectively to
leading order in . The decay of single particle quantum states hastens as
their wavevectors cross the Hubble radius and their width is related to the
highly squeezed limit of the bi- or tri-spectrum of scalar fluctuations
respectively.Comment: 31 pages, 7 figures. Comments and references, matches published
versio
A Fresh Catch of Massive Binaries in the Cygnus OB2 Association
Massive binary stars may constitute a substantial fraction of progenitors to
supernovae and gamma-ray bursts, and the distribution of their orbital
characteristics holds clues to the formation process of massive stars. As a
contribution to securing statistics on OB-type binaries, we report the
discovery and orbital parameters for five new systems as part of the Cygnus OB2
Radial Velocity Survey. Four of the new systems (MT070, MT174, MT267, and MT734
(a.k.a. VI Cygni #11) are single-lined spectroscopic binaries while one (MT103)
is a double-lined system (B1V+B2V). MT070 is noteworthy as the longest period
system yet measured in Cyg OB2, with P=6.2 yr. The other four systems have
periods ranging between 4 and 73 days. MT174 is noteworthy for having a
probable mass ratio q<0.1, making it a candidate progenitor to a low-mass X-ray
binary. These measurements bring the total number of massive binaries in Cyg
OB2 to 25, the most currently known in any single cluster or association.Comment: Accepted for publication in the Astrophysical Journa
Mycobacterium leprae in Armadillo Tissues from Museum Collections, United States
We examined armadillos from museum collections in the United States using molecular assays to detect leprosy-causing bacilli. We found Mycobacterium leprae bacilli in samples from the United States, Bolivia, and Paraguay; prevalence was 14.8% in nine-banded armadillos. US isolates belonged to subtype 3I-2, suggesting long-term circulation of this genotype
Global Stability of a Premixed Reaction Zone (Time-Dependent Liñan’s Problem)
Global stability properties of a premixed, three-dimensional reaction zone are considered. In the nonadiabatic case (i.e., when there is a heat exchange between the reaction zone and the burned gases) there is a unique, spatially one-dimensional steady state that is shown to be unstable (respectively, asymptotically stable) if the reaction zone is cooled (respectively, heated) by the burned mixture. In the adiabatic case, there is a unique (up to spatial translations) steady state that is shown to be stable. In addition, the large-time asymptotic behavior of the solution is analyzed to obtain sufficient conditions on the initial data for stabilization. Previous partial numerical results on linear stability of one-dimensional reaction zones are thereby confirmed and extended
Morrigan: A Composite Instruction TLB Prefetcher
The effort to reduce address translation overheads has typically targeted data accesses since they constitute the overwhelming portion of the second-level TLB (STLB) misses in desktop and HPC applications. The address translation cost of instruction accesses has been relatively neglected due to historically small instruction footprints. However, state-of-the-art datacenter and server applications feature massive instruction footprints owing to deep software stacks, resulting in high STLB miss rates for instruction accesses. This paper demonstrates that instruction address translation is a performance bottleneck in server workloads. In response, we propose Morrigan, a microarchitectural instruction STLB prefetcher whose design is based on new insights regarding instruction STLB misses. At the core of Morrigan there is an ensemble of table-based Markov prefetchers that build and store variable length Markov chains out of the instruction STLB miss stream. Morrigan further employs a sequential prefetcher and a scheme that exploits page table locality to maximize miss coverage. An important contribution of the work is showing that access frequency is more important than access recency when choosing replacement candidates. Based on this insight, Morrigan introduces a new replacement policy that identifies victims in the Markov prefetchers using a frequency stack while adapting to phase-change behavior. On a set of 45 industrial server workloads, Morrigan eliminates 69% of the memory references in demand page walks triggered by instruction STLB misses and improves geometric mean performance by 7.6%.This work is partially supported by the Spanish Ministry of Science and Technology through the PID2019-107255GB project, the Generalitat de Catalunya (contract 2017-SGR-1414), the NSF grant CCF-1912617, the Semiconductor Research Corporation grant 2936.001, and generous gifts from Intel Labs. Georgios Vavouliotis has been supported by the Spanish Ministry of Economy, Industry and Competitiveness and the European Social Fund under the FPI fellowship No. PRE2018-087046. Marc Casas has been supported by the Spanish Ministry of Economy, Industry and Competitiveness under the Ramon y Cajal fellowship No. RYC-2017-23269.Peer ReviewedPostprint (author's final draft
Growth Route Toward III-V Multispectral Solar Cells on Silicon
To date, high efficiency multijunction solar cells have been developed on Ge
or GaAs substrates for space applications, and terrestrial applications are
hampered by high fabrication costs. In order to reduce this cost, we propose a
breakthrough technique of III-V compound heteroepitaxy on Si substrates without
generation of defects critical to PV applications. With this technique we
expect to achieve perfect integration of heterogeneous Ga1-xInxAs
micro-crystals on Si substrates. In this paper, we show that this is the case
for x=0. GaAs crystals were grown by Epitaxial Lateral Overgrowth on Si (100)
wafers covered with a thin SiO2 nanostructured layer. The cristallographic
structure of these crystals is analysed by MEB and TEM imaging. Micro-Raman and
Micro-Photomuminescence spectra of GaAs crystals grown with different
conditions are compared with those of a reference GaAs wafer in order to have
more insight on eventual local strains and their cristallinity. This work aims
at developping building blocks to further develop a GaAs/Si tandem demonstrator
with a potential conversion efficiency of 29.6% under AM1.5G spectrum without
concentration, as inferred from our realistic modeling. This paper shows that
Epitaxial Lateral Overgrowth has a very interesting potential to develop
multijunction solar cells on silicon approaching the today 30.3% world record
of a GaInP/GaAs tandem cell under the same illumination conditions, but on a
costlier substrate than silicon.Comment: Preprint of the 28th EUPVSEC proceedings, September 2013, Paris,
France. (5 pages
- …