201 research outputs found
Atomic site sensitive processes in low energy ion-dimer collisions
Electron capture processes for low energy Ar9+ ions colliding on Ar2 dimer
targets are investigated, focusing attention on charge sharing as a function of
molecule orientation and impact parameter. A preference in charge-asymmetric
dissociation channels is observed, with a strong correlation between the
projectile scattering angle and the molecular ion orientation. The measurements
provide here clear evidences that projectiles distinguish each atom in the
target and, that electron capture from near-site atom is favored. Monte Carlo
calculations based on the classical over-the-barrier model, with dimer targets
represented as two independent atoms, are compared to the data. They give a new
insight into the dynamics of the collision by providing, for the di erent
electron capture channels, the two-dimensional probability maps p(~b), where ~b
is the impact parameter vector in the molecular frame
Louis-Ferdinand CĂ©line, literary genius or national pariah? Defining moral parameters for influential cultural figures, post- Charlie Hebdo
In January 2011 the French Minister of Culture, FrĂ©dĂ©ric Mitterrand, withdrew Louis-Ferdinand CĂ©line from a list of famous French authors specifically selected for a national celebration of culture. This bold decision polarized opinion: while many welcomed Mitterrandâs intervention, a number of prominent writers, some of them Jewish, opposed it on the grounds that CĂ©lineâs abhorrent political beliefs â 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 CĂ©line 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
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
Cranberry A-type proanthocyanidins selectively target acute myeloid leukemia cells
Most elderly patients affected with acute myeloid leukemia (AML) will relapse and die of their disease even after achieving complete remission, thus emphasizing the urgent need for new therapeutic approaches with minimum toxicity to normal hematopoietic cells. Cranberry (Vaccinium spp.) extracts have exhibited anticancer and chemopreventive properties that have been mostly attributed to A-type proanthocyanidin (A-PAC) compounds. A-PACs, isolated from a commercially available cranberry extract, were evaluated for their effects on leukemia cell lines, primary AML samples, and normal CD34+ cord blood specimens. Our results indicated potent and specific antileukemia activity in vitro. In addition, the antileukemia activity of A-PACs extended to malignant progenitor and stem cell populations, sparing their normal counterparts. The antileukemia effects of A-PACs were also observed in vivo using patient derived xenografts. Surprisingly, we found that the mechanism of cell death was driven by activation of NF-ÎșB. Overall, our data suggest that A-PACs could be used to improve treatments for AML by targeting leukemia stem cells through a potentially novel pathway
QCD Corrections and Non-standard Three Vector Boson Couplings in Production at Hadron Colliders
The process p\,p\hskip-7pt\hbox{^{^{(\!-\!)}}} \rightarrow W^{+} W^{-} + X
\rightarrow \ell^+_1 \nu_1 \ell^-_2 \bar \nu_2 + X is calculated to for general and conserving couplings (). The prospects for probing the couplings in this reaction are
explored. The impact of QCD corrections and various
background processes on the observability of non-standard couplings in
production at the Tevatron and the Large Hadron Collider (LHC) is
discussed in detail. Sensitivity limits for anomalous couplings are
derived at next-to-leading order for the Tevatron and LHC center of mass
energies, and are compared to the bounds which can be achieved in other
processes. Unless a jet veto or a cut on the total transverse momentum of the
hadrons in the event is imposed, the QCD corrections and
the background from top quark production decrease the sensitivity of
p\,p\hskip-7pt\hbox{^{^{(\!-\!)}}} \rightarrow W^{+} W^{-} + X \rightarrow
\ell^+_1 \nu_1 \ell^-_2 \bar \nu_2 + X to anomalous couplings by a
factor two to five.Comment: REVTEX 3, 62 pages, 21 Figures (not included available upon request),
the postscript file of the complete paper is available at
ftp://ucdhep.ucdavis.edu/han/ww/ww_paper.p
Historical perspective on seismic hazard to Hispaniola and the northeast Caribbean region
This paper is not subject to U.S. copyright. The definitive version was published in Journal of Geophysical Research 116 (2011): B12318, doi:10.1029/2011JB008497.We evaluate the long-term seismic activity of the North-American/Caribbean plate boundary from 500 years of historical earthquake damage reports. The 2010 Haiti earthquakes and other earthquakes were used to derive regional attenuation relationships between earthquake intensity, magnitude, and distance from the reported damage to the epicenter, for Hispaniola and for Puerto Rico and the Virgin Islands. The attenuation relationship for Hispaniola earthquakes and northern Lesser Antilles earthquakes is similar to that for California earthquakes, indicating a relatively rapid attenuation of damage intensity with distance. Intensities in Puerto Rico and the Virgin Islands decrease less rapidly with distance. We use the intensity-magnitude relationships to systematically search for the location and intensity magnitude MI which best fit all the reported damage for historical earthquakes. Many events occurred in the 20th-century along the plate-boundary segment from central Hispaniola to the NW tip of Puerto Rico, but earlier events from this segment were not identified. The remaining plate boundary to the east to Guadeloupe is probably not associated with M > 8 historical subduction-zone earthquakes. The May 2, 1787 earthquake, previously assigned an M 8â8.25, is probably only MI 6.9 and could be located north, west or SW of Puerto Rico. An MI 6.9 earthquake on July 11, 1785 was probably located north or east of the Virgin Islands. We located MI < 8 historical earthquakes on April 5, 1690, February 8, 1843, and October 8, 1974 in the northern Lesser Antilles within the arc. We speculate that the December 2, 1562 (MI 7.7) and May 7, 1842 (MI 7.6) earthquakes ruptured the Septentrional Fault in northern Hispaniola. If so, the recurrence interval on the central Septentrional Fault is âŒ300 years, and only 170 years has elapsed since the last event. The recurrence interval of large earthquakes along the Hispaniola subduction segment is likely longer than the historical record. Intra-arc M â„ 7.0 earthquakes may occur every 75â100 years in the 410-km-long segment between the Virgin Islands and Guadeloupe
Cyclic Nucleotide Phosphodiesterases and Compartmentation in Normal and Diseased Heart
International audienceCyclic nucleotide phosphodiesterases (PDEs) degrade the second messengers cAMP and cGMP, thereby regulating multiple aspects of cardiac function. This highly diverse class of enzymes encoded by 21 genes encompasses 11 families which are not only responsible for the termination of cyclic nucleotide signalling, but are also involved in the generation of dynamic microdomains of cAMP and cGMP controlling specific cell functions in response to various neurohormonal stimuli. In myocardium, the PDE3 and PDE4 families are predominant to degrade cAMP and thereby regulate cardiac excitation-contraction coupling. PDE3 inhibitors are positive inotropes and vasodilators in human, but their use is limited to acute heart failure and intermittent claudication. PDE5 is particularly important to degrade cGMP in vascular smooth muscle, and PDE5 inhibitors are used to treat erectile dysfunction and pulmonary hypertension. However, these drugs do not seem efficient in heart failure with preserved ejection fraction. There is experimental evidence that these PDEs as well as other PDE families including PDE1, PDE2 and PDE9 may play important roles in cardiac diseases such as hypertrophy and heart failure. After a brief presentation of the cyclic nucleotide pathways in cardiac cells and the major characteristics of the PDE superfamily, this chapter will present their role in cyclic nucleotide compartmentation and the current use of PDE inhibitors in cardiac diseases together with the recent research progresses that could lead to a better exploitation of the therapeutic potential of these enzymes in the future
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