1,818 research outputs found
Mitochondrial DNA and temperature tolerance in lager yeasts
A growing body of research suggests that the mitochondrial genome (mtDNA) is important for temperature adaptation. In the yeast genus Saccharomyces, species have diverged in temperature tolerance, driving their use in high- or low-temperature fermentations. Here, we experimentally test the role of mtDNA in temperature tolerance in synthetic and industrial hybrids (Saccharomyces cerevisiae × Saccharomyces eubayanus or Saccharomyces pastorianus), which cold-brew lager beer. We find that the relative temperature tolerances of hybrids correspond to the parent donating mtDNA, allowing us to modulate lager strain temperature preferences. The strong influence of mitotype on the temperature tolerance of otherwise identical hybrid strains provides support for the mitochondrial climactic adaptation hypothesis in yeasts and demonstrates how mitotype has influenced the world’s most commonly fermented beverage.This work was supported by the USDA National Institute of Food and Agriculture (Hatch project no. 1003258), the NSF (grant no. DEB-1253634), and in part by the DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science; nos. DE-SC0018409 and DE-FC02-07ER64494). E.P.B. was supported by a Louis and Elsa Thomsen Wisconsin Distinguished Graduate Fellowship. C.T.H. is a Pew Scholar in the Biomedical Sciences and a Vilas Faculty Early Career Investigator, supported by the Pew Charitable Trusts and the Vilas Trust Estate. D.P. is a Marie Sklodowska-Curie fellow of the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 747775). J.C.F. was supported by the NIH (no. GM080669)Peer Reviewe
Risk-constrained minimisation of combined event detection and decision time for online transient stability assessment
Sorafenib resistance and JNK signaling in carcinoma during extracellular matrix stiffening
Tumor progression is coincident with mechanochemical changes in the extracellular matrix (ECM). We hypothesized that tumor stroma stiffening, alongside a shift in the ECM composition from a basement membrane-like microenvironment toward a dense network of collagen-rich fibers during tumorigenesis, confers resistance to otherwise powerful chemotherapeutics. To test this hypothesis, we created a high-throughput drug screening platform based on our poly(ethylene glycol)-phosphorylcholine (PEG-PC) hydrogel system, and customized it to capture the stiffness and integrin-binding profile of in vivo tumors. We report that the efficacy of a Raf kinase inhibitor, sorafenib, is reduced on stiff, collagen-rich microenvironments, independent of ROCK activity. Instead, sustained activation of JNK mediated this resistance, and combining a JNK inhibitor with sorafenib eliminated stiffness-mediated resistance in triple negative breast cancer cells. Surprisingly, neither ERK nor p38 appears to mediate sorafenib resistance, and instead, either ERK or p38 inhibition rescued sorafenib resistance during JNK inhibition, suggesting negative crosstalk between these signaling pathways on stiff, collagen-rich environments. Overall, we discovered that β1integrin and its downstream effector JNK mediate sorafenib resistance during tumor stiffening. These results also highlight the need for more advanced cell culture platforms, such as our high-throughput PEG-PC system, with which to screen chemotherapeutics
Manual of techniques for estimating bacterial growth rates, productivity and numbers in aquaculture ponds
Heterotrophic microorganisms, especially bacteria, play an
important part in decomposition processes, nutrient cycling and
food chains in aquatic systems. A number of different methods
have been proposed for measuring microbial growth rates, but many
are not specific for bacteria or do not include the whole population.
It is evident that the ideal method should involve minimal handling
of the bacterial population and be applied quickly so as not to alter
natural or in situ growth rates or to be influenced by bacterial grazers.
The use of radioactive nucleicacid precursors especially thymidine,
to measure the rate of DNA synthesis has many of the prerequisites
of the ideal method. As with all other techniques, there are disadvantages
as well as advantages in using measurements of nucleicacid
synthesi
HI ``Tails'' from Cometary Globules in IC1396
IC 1396 is a relatively nearby (750 pc), large (>2 deg), HII region ionized
by a single O6.5V star and containing bright-rimmed cometary globules. We have
made the first arcmin resolution images of atomic hydrogen toward IC 1396, and
have found remarkable ``tail''-like structures associated with some of the
globules and extending up to 6.5 pc radially away from the central ionizing
star. These HI ``tails'' may be material which has been ablated from the
globule through ionization and/or photodissociation and then accelerated away
from the globule by the stellar wind, but which has since drifted into the
``shadow'' of the globules.
This report presents the first results of the Galactic Plane Survey Project
recently begun by the Dominion Radio Astrophysical Observatory.Comment: 11 pages, 5 postscript figures, uses aaspp4.sty macros, submitted in
uuencoded gzipped tar format, accepted for publication in Astrophysical
Journal Letters, colour figures available at
http://www.drao.nrc.ca/~schieven/news_sep95/ic1396.htm
Kinematics and the origin of the internal structures in HL Tau jet (HH 151)
Knotty structures of Herbig-Haro jets are common phenomena, and knowing the
origin of these structures is essential for understanding the processes of jet
formation. Basically, there are two theoretical approaches: different types of
instabilities in stationary flow, and velocity variations in the flow. We
investigate the structures with different radial velocities in the knots of the
HL Tau jet as well as its unusual behaviour starting from 20 arcsec from the
source. Collation of radial velocity data with proper motion measurements of
emission structures in the jet of HL Tau makes it possible to understand the
origin of these structures and decide on the mechanism for the formation of the
knotty structures in Herbig-Haro flows. We present observations obtained with a
6 m telescope (Russia) using the SCORPIO camera with scanning Fabry-Perot
interferometer. Two epochs of the observations of the HL/XZ Tau region in
Halpha emission (2001 and 2007) allowed us to measure proper motions for high
and low radial velocity structures. The structures with low and high radial
velocities in the HL Tau jet show the same proper motion. The point where the
HL Tau jet bents to the north (it coincides with the trailing edge of so-called
knot A) is stationary, i.e. does not have any perceptible proper motion and is
visible in Halpha emission only. We conclude that the high- and low- velocity
structures in the HL Tau jet represent bow-shocks and Mach disks in the
internal working surfaces of episodic outflows. The bend of the jet and the
brightness increase starting some distance from the source coincides with the
observed stationary deflecting shock. The increase of relative surface
brightness of bow-shocks could be the result of the abrupt change of the
physical conditions of the ambient medium as well as the interaction of a
highly collimated flow and the side wind from XZ Tau.Comment: To be published in Astronomy and Astrophysic
Observations of H3+ in the Diffuse Interstellar Medium
Surprisingly large column densities of H3+ have been detected using infrared
absorption spectroscopy in seven diffuse cloud sightlines (Cygnus OB2 12,
Cygnus OB2 5, HD 183143, HD 20041, WR 104, WR 118, and WR 121), demonstrating
that H3+ is ubiquitous in the diffuse interstellar medium. Using the standard
model of diffuse cloud chemistry, our H3+ column densities imply unreasonably
long path lengths (~1 kpc) and low densities (~3 cm^-3). Complimentary
millimeter-wave, infrared, and visible observations of related species suggest
that the chemical model is incorrect and that the number density of H3+ must be
increased by one to two orders of magnitude. Possible solutions include a
reduced electron fraction, an enhanced rate of H2 ionization, and/or a smaller
value of the H3+ dissociative recombination rate constant than implied by
laboratory experiments.Comment: To be published in Astrophysical Journal, March 200
The equation of state of solid nickel aluminide
The pressure-volume-temperature equation of state of the intermetallic
compound NiAl was calculated theoretically, and compared with experimental
measurements. Electron ground states were calculated for NiAl in the CsCl
structure, using density functional theory, and were used to predict the cold
compression curve and the density of phonon states. The Rose form of
compression curve was found to reproduce the ab initio calculations well in
compression but exhibited significant deviations in expansion. A
thermodynamically-complete equation of state was constructed for NiAl. Shock
waves were induced in crystals of NiAl by the impact of laser-launched Cu
flyers and by launching NiAl flyers into transparent windows of known
properties. The TRIDENT laser was used to accelerate the flyers to speeds
between 100 and 600m/s. Point and line-imaging laser Doppler velocimetry was
used to measure the acceleration of the flyer and the surface velocity history
of the target. The velocity histories were used to deduce the stress state, and
hence states on the principal Hugoniot and the flow stress. Flyers and targets
were recovered from most experiments. The effect of elasticity and plastic flow
in the sample and window was assessed. The ambient isotherm reproduced static
compression data very well, and the predicted Hugoniot was consistent with
shock compression data
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