605 research outputs found
Ideals, ideal extenders and forcing axioms
Ein ideal heiĂt abschĂŒssig falls die Ultrapotenzen mit einem fĂŒr den zugehörigen Forcing generischen Filter stets fundiert ist. Es werden die zusammenhĂ€nge zwischen abschĂŒssige Ideale und Forcing Axiome analysiert. Erst wird eine Forcingtechnik prĂ€sentiert, die beweist das das BeschrĂ€nkte Martins Maximum Axiom zusammen mit der abschĂŒssigkeit des nichtstationĂ€ren Ideals ein starkes effektives Gegenbeispiel zur Kontinuumshypothese impliziert. In einem zweiten Teil wird gezeigt das das beschrĂ€nkte proper Forcing Axiom zusammen mit der Existenz eines AbschĂŒssigen Ideals die Existenz eines inneren Models mit einer Woodin Kardinalzahl impliziert. Im letzten Teil wird eine Verallgemeinerung von abschĂŒssigen Ideale studiert. Es wird gezeigt das eine Kardinalzahl die generisch stark ist, schon stark im im Kernmodel sein muss, falls es keine woodinkardinalzahlen gibt. Und damit die Ăquikonsistenz von generisch starken und starken Kardinalzahlen bewiesen
Copper phosphoramidite-catalyzed enantioselective desymmetrization of meso-cyclic allylic bisdiethyl phosphates
A highly regio-, diastereo-, and enantioselective desymmetrization of five-, six-, and seven-membered meso-cyclic allylic bis-diethyl phosphates (2a, 2b, and 2c, respectively) was obtained with diethylzinc, using catalytic amounts of [Cu(OTf)](2).C6H6 and phosphoramidite ligands 5. Enantiomeric excesses of up to 87, 94, and >98% were obtained for the addition of diethylzinc to cyclopentene, cyclohexene, and cycloheptene bis-diethyl phosphates, respectively
The grapevine (Vitis vinifera) LysM receptor kinases VvLYK1-1 and VvLYK1-2 mediate chitooligosaccharide-triggered immunity
Chitin, a major component of fungal cell walls, is a well-known pathogen-associated molecular pattern (PAMP) that triggers defense responses in several mammal and plant species. Here, we show that two chitooligosaccharides, chitin and chitosan, act as PAMPs in grapevine (Vitis vinifera) as they elicit immune signalling events, defense gene expression and resistance against fungal diseases. To identify their cognate receptors, the grapevine family of LysM receptor kinases (LysM-RKs) was annotated and their gene expression profiles were characterized. Phylogenetic analysis clearly distinguished three V. vinifera LysM-RKs (VvLYKs) located in the same clade as the Arabidopsis CHITIN ELICITOR RECEPTOR KINASE1 (AtCERK1), which mediates chitin-induced immune responses. The Arabidopsis mutant Atcerk1, impaired in chitin perception, was transformed with these three putative orthologous genes encoding VvLYK1-1, -2, or -3 to determine if they would complement the loss of AtCERK1 function. Our results provide evidence that VvLYK1-1 and VvLYK1-2, but not VvLYK1-3, functionally complement the Atcerk1 mutant by restoring chitooligosaccharide-induced MAPK activation and immune gene expression. Moreover, expression of VvLYK1-1 in Atcerk1 restored penetration resistance to the non-adapted grapevine powdery mildew (Erysiphe necator). On the whole, our results indicate that the grapevine VvLYK1-1 and VvLYK1-2 participate in chitin- and chitosan-triggered immunity and that VvLYK1-1 plays an important role in basal resistance against E. necator
Isotopic control of the boron-vacancy spin defect in hexagonal boron nitride
We report on electron spin resonance (ESR) spectroscopy of boron-vacancy
(V) centers hosted in isotopically-engineered hexagonal boron
nitride (hBN) crystals. We first show that isotopic purification of hBN with
N yields a simplified and well-resolved hyperfine structure of
V centers, while purification with B leads to narrower ESR
linewidths. These results establish isotopically-purified hBN
crystals as the optimal host material for future use of V spin
defects in quantum technologies. Capitalizing on these findings, we then
demonstrate optically-induced polarization of N nuclei in
hBN, whose mechanism relies on electron-nuclear spin mixing in
the V ground state. This work opens up new prospects for future
developments of spin-based quantum sensors and simulators on a two-dimensional
material platform.Comment: 6 pages, 3 figur
Charge Transfer from Regularized Symmetry-Adapted Perturbation Theory
16 pages, 16 figure
Low energy measurement of the 7Be(p,gamma)8B cross section
We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm =
185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi).
Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^*
decay, respectively, were measured using a large acceptance spectrometer. The
zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a
weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is
deduced when combining this value with our previous results at higher energies.Comment: Accepted for publication in Phys. Rev. Let
The role of dynamical polarization of the ligand to metal charge transfer excitations in {\em ab initio} determination of effective exchange parameters
The role of the bridging ligand on the effective Heisenberg coupling
parameters is analyzed in detail. This analysis strongly suggests that the
ligand-to-metal charge transfer excitations are responsible for a large part of
the final value of the magnetic coupling constant. This permits to suggest a
new variant of the Difference Dedicated Configuration Interaction (DDCI)
method, presently one of the most accurate and reliable for the evaluation of
magnetic effective interactions. This new method treats the bridging ligand
orbitals mediating the interaction at the same level than the magnetic orbitals
and preserves the high quality of the DDCI results while being much less
computationally demanding. The numerical accuracy of the new approach is
illustrated on various systems with one or two magnetic electrons per magnetic
center. The fact that accurate results can be obtained using a rather reduced
configuration interaction space opens the possibility to study more complex
systems with many magnetic centers and/or many electrons per center.Comment: 7 pages, 4 figure
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