702 research outputs found
Grapevine breeding for resistance to powdery mildew: Bioassay system for evaluation of plant resistance and for characterization of different Uncinula necator strains
Several isolates of Uncinula necator were separated and kept in vitro. The pathogenicity of these isolates was compared by a bioassay system using small leaves issued from in vitro plants; 2 Āµl of spore suspension was inoculated on these leaves. Significative differences in sporulation time, aggressiveness, sporulation rate and resistance to fungicide triadimenol were observed between these isolates. Host plant variety also affects some of these characters of pathogenicity. The isolates were classified into 2 mating types concerning the aspect of perithecia formation by paired combination between 2 isolates. Productivity of perithecia varied in response to the combination of isolates and to host plant variety
Picosecond fluctuating protein energy landscape mapped by pressureātemperature molecular dynamics simulation
Microscopic statistical pressure fluctuations can, in principle, lead to corresponding fluctuations in the shape of a protein energy landscape. To examine this, nanosecond molecular dynamics simulations of lysozyme are performed covering a range of temperatures and pressures. The well known dynamical transition with temperature is found to be pressure-independent, indicating that the effective energy barriers separating conformational substates are not significantly influenced by pressure. In contrast, vibrations within substates stiffen with pressure, due to increased curvature of the local harmonic potential in which the atoms vibrate. The application of pressure is also shown to selectively increase the damping of the anharmonic, low-frequency collective modes in the protein, leaving the more local modes relatively unaffected. The critical damping frequency, i.e., the frequency at which energy is most efficiently dissipated, increases linearly with pressure. The results suggest that an invariant description of protein energy landscapes should be subsumed by a fluctuating picture and that this may have repercussions in, for example, mechanisms of energy dissipation accompanying functional, structural, and chemical relaxation
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Does the root to shoot ratio show a hormetic response to stress? An ecological and environmental perspective
Root/shoot (R/S) ratio is an important index for assessing plant health, and has received increased attention in the last decades as a sensitive indicator of plant stress induced by chemical or physical agents. The R/S ratio has been discussed in the context of ecological theory and its potential importance in ecological succession, where species follow different strategies for above-ground growth for light or below-ground competition for water and nutrients. We present evidence showing the R/S ratio follows a biphasic doseāresponse relationship under stress, typical of hormesis. The R/S ratio in response to stress has been widely compared among species and ecological succession classes. It is constrained by a variety of factors such as ontogeny. Furthermore, the current literature lacks doseāresponse studies incorporating the full doseāresponse continuum, hence limiting scientific understanding and possible valuable application. The data presented provide an important perspective for new-generation studies that can advance current ecological understanding and improve carbon storage estimates by R/S ratio considerations. Hormetic response of the R/S ratio can have an important role in forestry for producing seedlings with desired characteristics to achieve maximum health/productivity and resilience under plantation conditions
Vibrational energy relaxation in proteins
An overview of theories related to vibrational energy relaxation (VER) in
proteins is presented. VER of a selected mode in cytochrome c is studied using
two theoretical approaches. One is the equilibrium simulation approach with
quantum correction factors, and the other is the reduced model approach which
describes the protein as an ensemble of normal modes interacting through
nonlinear coupling elements. Both methods result in estimates of the VER time
(sub ps) for a CD stretching mode in the protein at room temperature. The
theoretical predictions are in accord with the experimental data of Romesberg's
group. A perspective on future directions for the detailed study of time scales
and mechanisms for VER in proteins is presented.Comment: 12 pages, 4 figures, accepted for publication in PNA
M\"{o}ssbauer study of the '11' iron-based superconductors parent compound Fe(1+x)Te
57Fe Moessbauer spectroscopy was applied to investigate the superconductor
parent compound Fe(1+x)Te for x=0.06, 0.10, 0.14, 0.18 within the temperature
range 4.2 K - 300 K. A spin density wave (SDW) within the iron atoms occupying
regular tetrahedral sites was observed with the square root of the mean square
amplitude at 4.2 K varying between 9.7 T and 15.7 T with increasing x. Three
additional magnetic spectral components appeared due to the interstitial iron
distributed over available sites between the Fe-Te layers. The excess iron
showed hyperfine fields at approximately 16 T, 21 T and 49 T for three
respective components at 4.2 K. The component with a large field of 49 T
indicated the presence of isolated iron atoms with large localized magnetic
moment in interstitial positions. Magnetic ordering of the interstitial iron
disappeared in accordance with the fallout of the SDW with the increasing
temperature
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Ethylenediurea (EDU) effects on Japanese larch: an one growing season experiment with simulated regenerating communities and a four growing season application to individual saplings
Japanese larch (Larix kaempferi (Lamb.) Carr.) and its hybrid are economically important coniferous trees widely grown in the Northern Hemisphere. Ground-level ozone (O3) concentrations have increased since the pre-industrial era, and research projects showed that Japanese larch is susceptible to elevated O3 exposures. Therefore, methodologies are needed to (1) protect Japanese larch against O3 damage and (2) conduct biomonitoring of O3 in Japanese larch forests and, thus, monitor O3 risks to Japanese larch. For the first time, this study evaluates whether the synthetic chemical ethylenediurea (EDU) can protect Japanese larch against O3 damage, in two independent experiments. In the first experiment, seedling communities, simulating natural regeneration, were treated with EDU (0, 100, 200, and 400 mg Lā1) and exposed to either ambient or elevated O3 in a growing season. In the second experiment, individually-grown saplings were treated with EDU (0, 200 and 400 mg Lā1) and exposed to ambient O3 in two growing seasons and to elevated O3 in the succeeding two growing seasons. The two experiments revealed that EDU concentrations of 200ā400 mg Lā1 could protect Japanese larch seedling communities and individual saplings against O3-induced inhibition of growth and productivity. However, EDU concentrationsāā¤ā200 mg Lā1 did offer only partial protection when seedling communities were coping with higher level of O3-induced stress, and only 400 mg EDU Lā1 fully protected communities under higher stress. Therefore, we conclude that among the concentrations tested the concentration offering maximum protection to Japanese larch plants under high competition and O3-induced stress is that of 400 mg EDU Lā1. The results of this study can provide a valuable resource of information for applied forestry in an O3-polluted world
Taxing Capital? Not a Bad Idea After All!
Premi a l'excelĀ·lĆØncia investigadora. 2010Publicat tambĆ© com a : CEPR Discussion Paper - ISSN 0265-8003 NĆŗm. 5929 (2006), p. 1-55We quantitatively characterize the optimal capital and labor income tax in an overlapping generations model with idiosyncratic, uninsurable income shocks and permanent productivity differences of households. The optimal capital income tax rate is significantly positive at 36 percent. The optimal progressive labor income tax is, roughly, a flat tax of 23 percent with a deduction of #7,200 (relative to average household income of #42,000). The high optimal capital income tax is mainly driven by the life-cycle structure of the model, whereas the optimal progressivity of the labor income tax is attributable to the insurance and redistribution role of the tax system. (JEL E13, H21, H24, H25
Electronic and Magnetic Phase Diagram of a Superconductor, SmFeAsO1-xFx
A crystallographic and magnetic phase diagram of SmFeAsO1-xFx is determined
as a function of x in terms of temperature based on electrical transport and
magnetization, synchrotron powder x-ray diffraction, 57Fe Mossbauer spectra
(MS), and 149Sm nuclear resonant forward scattering (NRFS) measurements. MS
revealed that the magnetic moments of Fe were aligned antiferromagnetically at
~144 K (TN(Fe)). The magnetic moment of Fe (MFe) is estimated to be 0.34
myuB/Fe at 4.2 K for undoped SmFeAsO; MFe is quenched in superconducting
F-doped SmFeAsO. 149Sm NRFS spectra revealed that the magnetic moments of Sm
start to order antiferromagnetically at 5.6 K (undoped) and 4.4 K (TN(Sm)) (x =
0.069). Results clearly indicate that the antiferromagnetic Sm sublattice
coexists with the superconducting phase in SmFeAsO1-xFx below TN(Sm), while
antiferromagnetic Fe sublattice does not coexist with the superconducting
phase.Comment: Accepted in New Journal of Physic
Page charge of D-branes and its behavior in topologically nontrivial B-fields
The RR Page charges for the D(2p+1)-branes with B-field in type IIB
supergravity are constructed consistently from brane source currents. The
resulting Page charges are B-independent in the nontrivial and intricate way.
It is found that in topologically trivial B-field the Page charge is conserved,
but in the topologically nontrivial B-field it is no longer to be conserved,
instead there is a jump between two Page charges defined in each patch, and we
interpret this jump as Hanany-Witten effect.Comment: 25 pages, 4 figures, typos corrected and reference adde
Paramagnetic Phase of a Heavy-Fermion Compound, CeFePO, Probed by 57Fe M\"{o}ssbauer Spectroscopy
57Fe M\"{o}ssbauer spectroscopy was applied to an iron-based layered compound
CeFePO. At temperatures from 9.4 to 293 K, no magnetic splitting was observed
in the M\"ossbauer spectra of CeFePO indicating a paramagnetic phase of the Fe
magnetic sublattice. All the spectra were fitted with a small quadrupole
splitting, and the Debye temperature of CeFePO was found to be \sim448 K. The
isomer shift at room temperature, 0.32 mm/s, was almost equal to those of
LnFeAsO (Ln = La, Ce, Sm). Comparing s-electron density using the isomer shifts
and unit cell volumes, it was found that the Fe of CeFePO has a similar valence
state to other layered iron-based quaternary oxypnictides except LaFePO
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