1,386 research outputs found
The CP-violating asymmetry in \eta\to\pi^+ \pi^- e^+e^-
We study the CP-violating asymmetry {\cal A}_{\rm CP}, which arises, in
\eta\to\pi^+\pi^- e^+e^-, from the angular correlation of the e^+ e^- and
\pi^+\pi^- planes due to the interference between the magnetic and electric
decay amplitudes. With the phenomenologically determined magnetic amplitude and
branching ratio as input, the asymmetry, induced by the electric bremsstrahlung
amplitude through the CP-violating decay \eta\to\pi^+\pi^-, and by an
unconventional tensor type operator, has been estimated respectively. The upper
bound of {\cal A}_{\rm CP} from the former is about 10^{-3}, and the asymmetry
from the latter might be up to O(10^{-2}). One can therefore expect that this
CP asymmetry would be an interesting CP-violating observable for the future
precise measurements in the \eta factories.Comment: LaTeX, 6 pages. One reference corrected, and some new references
adde
Colored noise in the fractional Hall effect: duality relations and exact results
We study noise in the problem of tunneling between fractional quantum Hall
edge states within a four probe geometry. We explore the implications of the
strong-weak coupling duality symmetry existent in this problem for relating the
various density-density auto-correlations and cross-correlations between the
four terminals. We identify correlations that transform as either ``odd'' or
``anti-symmetric'', or ``even'' or ``symmetric'' quantities under duality. We
show that the low frequency noise is colored, and that the deviations from
white noise are exactly related to the differential conductance. We show
explicitly that the relationship between the slope of the low frequency noise
spectrum and the differential conductance follows from an identity that holds
to {\it all} orders in perturbation theory, supporting the results implied by
the duality symmetry. This generalizes the results of quantum supression of the
finite frequency noise spectrum to Luttinger liquids and fractional statistics
quasiparticles.Comment: 14 pages, 3 figure
Conditional expression in corticothalamic efferents reveals a developmental role for nicotinic acetylcholine receptors in modulation of passive avoidance behavior
Prenatal nicotine exposure has been linked to attention deficit hyperactivity disorder and cognitive impairment, but the sites of action for these effects of nicotine are still under investigation. High-affinity nicotinic acetylcholine receptors (nAChRs) contain the .2 subunit and modulate passive avoidance (PA) learning in mice. Using an inducible, tetracycline-regulated transgenic system, we generated lines of mice with expression of high-affinity nicotinic receptors restored in specific neuronal populations. One line of mice shows functional .2 subunit-containing nAChRs localized exclusively in corticothalamic efferents. Functional, presynaptic nAChRs are present in the thalamus of these mice as detected by nicotine-elicited rubidium efflux assays from synaptosomes. Knock-out mice lacking high-affinity nAChRs show elevated baseline PA learning, whereas normal baseline PA behavior is restored in mice with corticothalamic expression of these nAChRs. In contrast, nicotine can enhance PA learning in adult wild-type animals but not in corticothalamic-expressing transgenic mice. When these transgenic mice are treated with doxycycline in adulthood to switch off nAChR expression, baseline PA is maintained even after transgene expression is abolished. These data suggest that high-affinity nAChRs expressed on corticothalamic neurons during development are critical for baseline PA performance and provide a potential neuroanatomical substrate for changes induced by prenatal nicotine exposure leading to long-term behavioral and cognitive deficits
Chronic arsenic exposure and risk of infant mortality in two areas of Chile.
Chronic arsenic exposure has been associated with a range of neurologic, vascular, dermatologic, and carcinogenic effects. However, limited research has been directed at the association of arsenic exposure and human reproductive health outcomes. The principal aim of this study was to investigate the trends in infant mortality between two geographic locations in Chile: Antofagasta, which has a well-documented history of arsenic exposure from naturally contaminated water, and Valparaíso, a comparable low-exposure city. The arsenic concentration in Antofagasta's public drinking water supply rose substantially in 1958 with the introduction of a new water source, and remained elevated until 1970. We used a retrospective study design to examine time and location patterns in infant mortality between 1950 and 1996, using univariate statistics, graphical techniques, and Poisson regression analysis. Results of the study document the general declines in late fetal and infant mortality over the study period in both locations. The data also indicate an elevation of the late fetal, neonatal, and postneonatal mortality rates for Antofagasta, relative to Valparaíso, for specific time periods, which generally coincide with the period of highest arsenic concentration in the drinking water of Antofagasta. Poisson regression analysis yielded an elevated and significant association between arsenic exposure and late fetal mortality [rate ratio (RR) = 1.7; 95% confidence interval (CI), 1.5-1.9], neonatal mortality (RR = 1.53; CI, 1.4-1.7), and postneonatal mortality (RR = 1.26; CI, 1.2-1.3) after adjustment for location and calendar time. The findings from this investigation may support a role for arsenic exposure in increasing the risk of late fetal and infant mortality
Observation of a One-Dimensional Spin-Orbit Gap in a Quantum Wire
Understanding the flow of spins in magnetic layered structures has enabled an
increase in data storage density in hard drives over the past decade of more
than two orders of magnitude1. Following this remarkable success, the field of
'spintronics' or spin-based electronics is moving beyond effects based on local
spin polarisation and is turning its attention to spin-orbit interaction (SOI)
effects, which hold promise for the production, detection and manipulation of
spin currents, allowing coherent transmission of information within a device.
While SOI-induced spin transport effects have been observed in two- and
three-dimensional samples, these have been subtle and elusive, often detected
only indirectly in electrical transport or else with more sophisticated
techniques. Here we present the first observation of a predicted 'spin-orbit
gap' in a one-dimensional sample, where counter-propagating spins, constituting
a spin current, are accompanied by a clear signal in the easily-measured linear
conductance of the system.Comment: 10 pages, 5 figures, supplementary informatio
Cytoplasmic localization of calcium/calmodulin-dependent protein kinase I-α depends on a nuclear export signal in its regulatory domain
AbstractCalcium/calmodulin-dependent protein kinase I-α (CaMKI-α) is a ubiquitous cytosolic enzyme that phosphorylates a number of nuclear proteins in vitro and has been implicated in transcriptional regulation. We report that cytoplasmic localization of CaMKI-α depends on CRM1-mediated nuclear export mediated through a Rev-like nuclear export signal in the CaMKI-α regulatory domain. Interaction of CaMKI-α with a CRM1 complex in vitro is enhanced by incubation with calcium/calmodulin. Translocation of CaMKI-α into the nucleus involves a conserved sequence located within the catalytic core. Mutation of this sequence partially blocks nuclear entry of an export-impaired mutant of CaMKI-α
Spontaneous Abortion and a Diet Drug Containing Caffeine and Ephedrine: A Study within the Danish National Birth Cohort
Background: Medications may be consumed periconceptionally before a woman knows she is pregnant. In this study, the authors evaluate the association of a prescription diet drug (Letigen) containing ephedrine (20 mg) and caffeine (200 mg) with spontaneous abortion (SAB) in the Danish National Birth Cohort. Methods: Women were recruited during their first prenatal visit from 1996-2002. Pre-conception and early pregnancy medication use was reported on the enrollment form, and pregnancy outcome was determined by linking the mother's Civil Registration Number to the Medical Birth Registry and the National Hospital Discharge Register. Of 97,903 eligible pregnancies, 4,443 ended in SAB between 5 and 20 completed gestational weeks, inclusive. Letigen use was reported for 565 pregnancies. Cox regression models accounting for left truncation were fit to estimate the effect of pre-conception and early pregnancy Letigen use on SAB. Principal Findings: The estimated maternal age-adjusted hazard ratio for SAB was 1.1 (95% confidence interval 0.8-1.6) for any periconceptional Letigen use compared to no periconceptional use. Conclusions: Although Letigen has high levels of caffeine (the recommended 3 pills/day are approximately equivalent to caffeine from 6 cups of coffee), periconceptional use does not appear to be associated with an appreciably increased hazard of clinically recognized SAB. © 2012 Howards et al
Nonuniversal behavior of scattering between fractional quantum Hall edges
Among the predicted properties of fractional quantum Hall states are
fractionally charged quasiparticles and conducting edge-states described as
chiral Luttinger liquids. In a system with a narrow constriction, tunneling of
quasi-particles between states at different edges can lead to resistance and to
shot noise. The ratio of the shot noise to the backscattered current, in the
weak scattering regime, measures the fractional charge of the quasi-particle,
which has been confirmed in several experiments. However, the non-linearity of
the resistance predicted by the chiral Luttinger liquid theory was apparently
not observed in some of these cases. As a possible explanation for these
discrepancies, we consider a model where a smooth edge profile leads to
formation of additional edge states. Coupling between the current carrying edge
mode and the additional phonon like mode can lead to {\it nonuniversal}
exponents in the current-voltage characteristic, while preserving the ratio
between shot noise and the back-scattered current, for weak backscattering. For
special values of the coupling, one may obtain a linear I-V behavior.Comment: 10 pages, 3 figure
Taxing the powerful, the rise of populism and the crisis in Europe: the case for the EU Common Consolidated Corporate Tax Base
Contemporary populism is rooted in a crisis of legitimacy. Corporate taxavoidance by multinationals is one cause of that crisi s. Although states tend to beincreasingly formally committed to tackling avoidance, they do so in a system thatpromotes contradictory sets of behaviour. This tends to undermine attempts to solvethe problem of avoidance unless a more transformative collective approach is taken.Ironically, despite its own democratic deficit, the European Comm ission has taken aleading role in promoting such a solution: the Common Consolidated Corporate TaxBase (CCCTB). In this paper, I set out the case for ‘unitary taxation’ based on theCCCTB and state some of its current problems. The problem of corporation taxraises a basic issue in terms of who is sovereignty for, and solving the problemprovides an important contribution to legitimacy of both the state and the EU
- …