184 research outputs found
Phthalocyanine-based dumbbell-shaped molecule: synthesis, structure and charge transport studies
International audienceWe describe the synthesis of a fully conjugated donor-acceptor-donor triad (ZnPc-BTD-ZnPc) made of zinc phthalocyanine donor fragments (ZnPc) at both ends of a benzothiadiazole-based central dye (BTD). The molecule exhibits a broad absorption in the whole visible range. The introduction of sterically demanding alkoxy chains to the ZnPc fragments is found to limit the molecular organization to a short-range columnar order and the charge-carrier mobility to moderate values, but provides outstanding solubilities in organic solvents
Anion emission from water molecules colliding with positive ions: Identification of binary and many-body processes
It is shown that negative ions are ejected from gas-phase water molecules
when bombarded with positive ions at keV energies typical of solar-wind
velocities. This finding is relevant for studies of planetary and cometary
atmospheres, as well as for radiolysis and radiobiology. Emission of both H-
and heavier (O- and OH-) anions, with a larger yield for H-, was observed in
6.6-keV 16O+ + H2O collisions. The ex-perimental setup allowed separate
identification of anions formed in collisions with many-body dynamics from
those created in hard, binary collisions. Most of the ani-ons are emitted with
low kinetic energy due to many-body processes. Model calcu-lations show that
both nucleus-nucleus interactions and electronic excitations con-tribute to the
observed large anion emission yield.Comment: 5 pages, 4 figure
Diphoton Production at Hadron Colliders and New Contact Interactions
We explore the capability of the Tevatron and LHC to place limits on the
possible existence of flavor-independent contact
interactions which can lead to an excess of diphoton events with large
invariant masses. Assuming no departure from the Standard Model is observed, we
show that the Tevatron will eventually be able to place a lower bound of
0.5-0.6 TeV on the scale associated with this new contact interaction. At the
LHC, scales as large as 3-6 TeV may be probed with suitable detector cuts and
an integrated luminosity of .Comment: LaTex, 12pages plus 5 figures(available on request), SLAC-PUB-657
Proanthocyanidin oxidation of Arabidopsis seeds is altered in mutant of the high-affinity nitrate transporter NRT2.7
This article appears in:Special Issue: Nutrient Sensing and SignallingNRT2.7 is a seed-specific high-affinity nitrate transporter controlling nitrate content in Arabidopsis mature seeds. The objective of this work was to analyse further the consequences of the nrt2.7 mutation for the seed metabolism. This work describes a new phenotype for the nrt2.7-2 mutant allele in the Wassilewskija accession, which exhibited a distinctive pale-brown seed coat that is usually associated with a defect in flavonoid oxidation. Indeed, this phenotype resembled those of tt10 mutant seeds defective in the laccase-like enzyme TT10/LAC15, which is involved in the oxidative polymerization of flavonoids such as the proantocyanidins (PAs) (i.e. epicatechin monomers and PA oligomers) and flavonol glycosides. nrt2.7-2 and tt10-2 mutant seeds displayed the same higher accumulation of PAs, but were partially distinct, since flavonol glycoside accumulation was not affected in the nrt2.7-2 seeds. Moreover, measurement of in situ laccase activity excluded a possibility of the nrt2.7-2 mutation affecting the TT10 enzymic activity at the early stage of seed development. Functional complementation of the nrt2.7-2 mutant by overexpression of a full-length NRT2.7 cDNA clearly demonstrated the link between the nrt2.7 mutation and the PA phenotype. However, the PA-related phenotype of nrt2.7-2 seeds was not strictly correlated to the nitrate content of seeds. No correlation was observed when nitrate was lowered in seeds due to limited nitrate nutrition of plants or to lower nitrate storage capacity in leaves of clca mutants deficient in the vacuolar anionic channel CLCa. All together, the results highlight a hitherto-unknown function of NRT2.7 in PA accumulation/oxidation.Laure C. David, Julie Dechorgnat, Patrick Berquin, Jean Marc Routaboul, Isabelle Debeaujon, Françoise Daniel-Vedele and Sylvie Ferrario-Mér
Louis-Ferdinand Céline, literary genius or national pariah? Defining moral parameters for influential cultural figures, post- Charlie Hebdo
In January 2011 the French Minister of Culture, Frédéric Mitterrand, withdrew Louis-Ferdinand Céline from a list of famous French authors specifically selected for a national celebration of culture. This bold decision polarized opinion: while many welcomed Mitterrand’s intervention, a number of prominent writers, some of them Jewish, opposed it on the grounds that Céline’s abhorrent political beliefs – expressed in three anti-Semitic pamphlets and his flirtation with Nazism- should in no way detract from his literary genius. In the light of this controversy, and of the rise in anti-Semitism following the Charlie Hebdo attacks of January 2015, this paper proposes Céline as a vital case study of the moral parameters a democratic nation should apply to a culturally important figure whose political views are deemed unacceptably reactionary
Effective-Lagrangian approach to precision measurements: the anomalous magnetic moment of the muon
We investigate the use of effective Lagrangians to describe the effects on
high-precision observables of physics beyond the Standard Model. Using the
anomalous magnetic moment of the muon as an example, we detail the use of
effective vertices in loop calculations. We then provide estimates of the
sensitivity of new experiments measuring the muon's to the scale of
physics underlying the Standard Model.Comment: 22 pages, 1 figure, PHYZZX & EPSF, report #s UCRHEP-T98, UM_TH-92-17,
and NSF-ITP-92-122I Revision: The paper will now TeX properly; the content is
unchange
Constraints on Four Fermion Contact Interactions from Precise Electroweak Measurements
We establish constraints on a general four-fermion contact interaction from
precise measurements of electroweak parameters. We compute the one-loop
contribution for the leptonic width, anomalous magnetic, weak-magnetic,
electric and weak dipole moments of leptons in order to extract bounds on the
energy scale of these effective interactions.Comment: 16 pages, RevTeX, two figure
Uses and Abuses of Effective Lagrangians
Motivated by past and recent analyses we critically re-examine the use of
effective lagrangians in the literature to constrain new physics and to
determine the `physics reach' of future experiments. We demonstrate that many
calculations, such as those involving anomalous trilinear gauge-boson
couplings, either considerably overestimate loop-induced effects, or give
ambiguous answers. The source of these problems is the use of cutoffs to
evaluate the size of such operators in loop diagrams. In contrast to other
critics of these loop estimates, we prove that the inclusion of
nonlinearly-realized gauge invariance into the low-energy lagrangian is
irrelevant to this conclusion. We use an explicit example using known
multi-Higgs physics above the weak scale to underline these points. We show how
to draw conclusions regarding the nature of the unknown high-energy physics
without making reference to low-energy cutoffs.Comment: 36 page
Electron shakeoff following the β+ decay of trapped 35Ar+ ions
The electron shakeoff of 35Cl atoms resulting from the β+ decay of 35Ar+ ions has been investigated using a Paul trap coupled to a recoil-ion spectrometer. The charge-state distribution of the recoiling daughter nuclei is compared to theoretical calculations accounting for shakeoff and Auger processes. The calculations are in excellent agreement with the experimental results and enable one to identify the ionization reaction routes leading to the formation of all charge states.D.R. acknowledges support from the Spanish ministry of Economy and Competitiveness under the project FPA2010-14803 and the action AIC10-D000562
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