1,665 research outputs found
Review of Recent Legacy Airline Mergers in the U.S.: An Empirical Study from Investors’ Perspectives
Since the 2008 financial crisis, three legacy airline mergers have dramatically reshaped the landscape of the U.S. airline industry. Due to the lengthy process involved in an airline merger, it is important to understand whether the investors view the merger favorably. This study examined how investors reacted to the three recent legacy airline mergers in the U.S. by adopting a GARCH-EVT-Copula approach. Our empirical results revealed that positive dependencies between returns and trading volume changes were observed for each merger during various periods, indicating that investors were optimistic about the mergers. Accordingly, implications for future mergers are discussed
Corrections to and Discussion of "Implementation and Evaluation of Mixed-criticality Scheduling Approaches for Sporadic Tasks"
The AMC-IA mixed-criticality scheduling analysis was proposed as an improvement to the AMC-MAX adaptive mixed-criticality scheduling analysis. However, we have identified several necessary corrections to the AMC-IA analysis. In this letter we motivate and describe those corrections, and discuss and illustrate why the corrected AMC-IA analysis cannot be shown to outperform AMC-MAX
BRANCHLESS TRICHOMES links cell shape and cell cycle control in Arabidopsis trichomes
Endoreplication, also called endoreduplication, is a modified cell cycle in which DNA is repeatedly replicated without subsequent cell division. Endoreplication is often associated with increased cell size and specialized cell shapes, but the mechanism coordinating DNA content with shape and size remains obscure. Here we identify the product of the BRANCHLESS TRICHOMES (BLT) gene, a protein of hitherto unknown function that has been conserved throughout angiosperm evolution, as a link in coordinating cell shape and nuclear DNA content in endoreplicated Arabidopsis trichomes. Loss-of-function mutations in BLT were found to enhance the multicellular trichome phenotype of mutants in the SIAMESE (SIM) gene, which encodes a repressor of endoreplication. Epistasis and overexpression experiments revealed that BLT encodes a key regulator of trichome branching. Additional experiments showed that BLT interacts both genetically and physically with STICHEL, another key regulator of trichome branching. Although blt mutants have normal trichome DNA content, overexpression of BLT results in an additional round of endoreplication, and blt mutants uncouple DNA content from morphogenesis in mutants with increased trichome branching, further emphasizing its role in linking cell shape and endoreplication. © 2011. Published by The Company of Biologists Ltd
Contrasting Responses of Rhizosphere Bacterial, Fungal, Protist and Nematode Communities to Nitrogen Fertilisation and Crop Genotype in Field Grown Oilseed Rape (Brassica napus)
© 2021 Picot, Hale, Hilton, Teakle, Schäfer, Huang, Perryman, West and Bending. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). https://creativecommons.org/licenses/by/4.0/The rhizosphere microbiome is considered to play a key role in determining crop health. However, current understanding of the factors which shape assembly and composition of the microbiome is heavily biased toward bacterial communities, and the relevance for other microbial groups is unclear. Furthermore, community assembly is determined by a variety of factors, including host genotype, environment and agricultural management practices, and their relative importance and interactions remain to be elucidated. We investigated the impact of nitrogen fertilization on rhizosphere bacterial, fungal, nematode and protist communities of 10 contrasting oilseed rape genotypes in a field experiment. We found significant differences in the composition of bacteria, fungi, protist and nematode communities between the rhizosphere and bulk soil. Nitrogen application had a significant but weak effect on fungal, bacterial, and protist community composition, and this was associated with increased relative abundance of a complex of fungal pathogens in the rhizosphere and soil, including Mycosphaerella sp. and Leptosphaeria sp. Network analysis showed that nitrogen application had different effects on microbial community connectivity in the soil and rhizosphere. Crop genotype significantly affected fungal community composition, with evidence for a degree of genotype specificity for a number of pathogens, including L. maculans, Alternaria sp., Pyrenopeziza brassicae, Olpidium brassicae, and L. biglobosa, and also potentially beneficial Heliotales root endophytes. Crop genotype had no significant effect on assembly of bacteria, protist or nematode communities. There was no relationship between genetic distance of crop genotypes and the extent of dissimilarity of rhizosphere microbial communities. Field disease assessment confirmed infection of crops by Leptosphaeria sp., P. brassicae, and Alternaria sp., indicating that rhizosphere microbiome sequencing was an effective indicator of plant health. We conclude that under field conditions soil and rhizosphere nutrient stoichiometry and crop genotype are key factors determining crop health by influencing the infection of roots by pathogenic and mutualistic fungal communities, and the connectivity and stability of rhizosphere microbiome interaction networks.Peer reviewedFinal Published versio
Testing Inflation with Large Scale Structure: Connecting Hopes with Reality
The statistics of primordial curvature fluctuations are our window into the
period of inflation, where these fluctuations were generated. To date, the
cosmic microwave background has been the dominant source of information about
these perturbations. Large scale structure is however from where drastic
improvements should originate. In this paper, we explain the theoretical
motivations for pursuing such measurements and the challenges that lie ahead.
In particular, we discuss and identify theoretical targets regarding the
measurement of primordial non-Gaussianity. We argue that when quantified in
terms of the local (equilateral) template amplitude
(), natural target levels of sensitivity are . We highlight that such levels are within
reach of future surveys by measuring 2-, 3- and 4-point statistics of the
galaxy spatial distribution. This paper summarizes a workshop held at CITA
(University of Toronto) on October 23-24, 2014.Comment: 27 pages + reference
The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
Recent high resolution observations of the Galactic center black hole allow
for direct comparison with accretion disk simulations. We compare
two-temperature synchrotron emission models from three dimensional, general
relativistic magnetohydrodynamic simulations to millimeter observations of Sgr
A*. Fits to very long baseline interferometry and spectral index measurements
disfavor the monochromatic face-on black hole shadow models from our previous
work. Inclination angles \le 20 degrees are ruled out to 3 \sigma. We estimate
the inclination and position angles of the black hole, as well as the electron
temperature of the accretion flow and the accretion rate, to be i=50+35-15
degrees, \xi=-23+97-22 degrees, T_e=(5.4 +/- 3.0)x10^10 K and
Mdot=(5+15-2)x10^-9 M_sun / yr respectively, with 90% confidence. The black
hole shadow is unobscured in all best fit models, and may be detected by
observations on baselines between Chile and California, Arizona or Mexico at
1.3mm or .87mm either through direct sampling of the visibility amplitude or
using closure phase information. Millimeter flaring behavior consistent with
the observations is present in all viable models, and is caused by magnetic
turbulence in the inner radii of the accretion flow. The variability at
optically thin frequencies is strongly correlated with that in the accretion
rate. The simulations provide a universal picture of the 1.3mm emission region
as a small region near the midplane in the inner radii of the accretion flow,
which is roughly isothermal and has \nu/\nu_c ~ 1-20, where \nu_c is the
critical frequency for thermal synchrotron emission.Comment: 14 pages, 17 figures, accepted by Ap
DBI Inflation using a One-Parameter Family of Throat Geometries
We demonstrate the possibility of examining cosmological signatures in the
DBI inflation setup using the BGMPZ solution, a one-parameter family of
geometries for the warped throat which interpolate between the Maldacena-Nunez
and Klebanov-Strassler solutions. The warp factor is determined numerically and
subsequently used to calculate cosmological observables including the scalar
and tensor spectral indices, for a sample point in the parameter space. As one
moves away from the KS solution for the throat the warp factor is qualitatively
different, which leads to a significant change for the observables, but also
generically increases the non-Gaussianity of the models. We argue that the
different models can potentially be differentiated by current and future
experiments.Comment: 17 pages, 10 figures; v2: section 4 expanded, references added; v3:
typos fixe
Universal Non-Polar Switching in Carbon-doped Transition Metal Oxides (TMOs) and Post TMOs
Transition metal oxides (TMOs) and post-TMOs (PTMOs), when doped with Carbon,
show non-volatile current-voltage (I-V) characteristics, which are both
universal and repeatable. We have shown spectroscopic evidence of the
introduction of carbon-based impurity states inside the existing larger bandgap
effectively creating a smaller bandgap which we suggest could enable Mott-like
correlation effect. Our findings indicate new insights for yet to be understood
unipolar and nonpolar resistive switching in the TMOs and PTMOs. We have shown
that device switching is not thermal-energy dependent and have developed an
electronic-dominated switching model that allows for the extreme temperature
operation (from 1.5 K to 423 K) and state retention up to 673 K for a 1-hour
bake. Importantly, we have optimized the technology in an industrial process
and demonstrated integrated 1-transistor/1-resistor (1T1R) arrays up to 1 kbit
with 47 nm devices on 300 mm wafers for advanced node CMOS-compatible
correlated electron RAM (CeRAM). These devices are shown to operate with 2 ns
write pulses and retain the memory states up to 200 C for 24 hours. The
collection of attributes shown, including scalability to state-of-the-art
dimensions, non-volatile operation to extreme low and high temperatures, fast
write, and reduced stochasticity as compared to filamentary memories such as
ReRAMs show the potential for a highly capable two-terminal back-end-of-line
non-volatile memory.Comment: 28 pages, 17 figures, accepted in APL Material
Probing the Optical Dynamics of Quantum Emitters in Hexagonal Boron Nitride
Hexagonal boron nitride is a van der Waals material that hosts
visible-wavelength quantum emitters at room temperature. However, experimental
identification of the quantum emitters' electronic structure is lacking, and
key details of their charge and spin properties remain unknown. Here, we probe
the optical dynamics of quantum emitters in hexagonal boron nitride using
photon emission correlation spectroscopy. Several quantum emitters exhibit
ideal single-photon emission with noise-limited photon antibunching,
. The photoluminescence emission lineshapes are consistent with
individual vibronic transitions. However, polarization-resolved excitation and
emission suggests the role of multiple optical transitions, and photon emission
correlation spectroscopy reveals complicated optical dynamics associated with
excitation and relaxation through multiple electronic excited states. We
compare the experimental results to quantitative optical dynamics simulations,
develop electronic structure models that are consistent with the observations,
and discuss the results in the context of ab initio theoretical calculations.Comment: 31 pages, 16 figures, 6 table
- …