739 research outputs found
The Eminent Doctor Fizz : Dr. Fizz and Chorus
https://digitalcommons.library.umaine.edu/mmb-vp/4599/thumbnail.jp
Room temperature magnetism in LaVO3/SrVO3 superlattices by geometrically confined doping
Based on the Hubbard model of strongly correlated systems, a reduction in the
bandwidth of the electrons can yield a substantial change in the properties of
the material. One method to modify the bandwidth is geometrically confined
doping, i.e. the introduction of a (thin) dopant layer in a material. In this
paper, the magnetic properties of LaVO/SrVO superlattices, in which the
geometrically confined doping is produced by a one monolayer thick SrVO
film, are presented. In contrast to the solid solution LaSrVO,
such superlattices have a finite magnetization up to room temperature.
Furthermore, the total magnetization of the superlattice depends on the
thickness of the LaVO layer, indicating an indirect coupling of the
magnetization that emerges at adjacent dopant layers. Our results show that
geometrically confined doping, like it can be achieved in superlattices,
reveals a way to induce otherwise unaccessible phases, possibly even with a
large temperature scale.Comment: 5 pages, 4 figure
T and CPT Symmetries in Entangled Neutral Meson Systems
Genuine tests of an asymmetry under T and/or CPT transformations imply the
interchange between in-states and out-states. I explain a methodology to
perform model-indepedent separate measurements of the three CP, T and CPT
symmetry violations for transitions involving the decay of the neutral meson
systems in B- and {\Phi}-factories. It makes use of the quantum-mechanical
entanglement only, for which the individual state of each neutral meson is not
defined before the decay of its orthogonal partner. The final proof of the
independence of the three asymmetries is that no other theoretical ingredient
is involved and that the event sample corresponding to each case is different
from the other two. The experimental analysis for the measurements of these
three asymmetries as function of the time interval {\Delta}t > 0 between the
first and second decays is discussed, as well as the significance of the
expected results. In particular, one may advance a first observation of true,
direct, evidence of Time-Reserval-Violation in B-factories by many standard
deviations from zero, without any reference to, and independent of,
CP-Violation. In some quantum gravity framework the CPT-transformation is
ill-defined, so there is a resulting loss of particle-antiparticle identity.
This mechanism induces a breaking of the EPR correlation in the entanglement
imposed by Bose statistics to the neutral meson system, the so-called
{\omega}-effect. I present results and prospects for the {\omega}-parameter in
the correlated neutral meson-antimeson states.Comment: Proc. DISCRETE 2010, Symposium on Prospects in the Physics of
Discrete Symmetries, December 2010, Rom
The Unique Brain Anatomy of Meditation Practitioners: Alterations in Cortical Gyrification
Several cortical regions are reported to vary in meditation practitioners. However, prior analyses have focused primarily on examining gray matter or cortical thickness. Thus, additional effects with respect to other cortical features might have remained undetected. Gyrification (the pattern and degree of cortical folding) is an important cerebral characteristic related to the geometry of the brain’s surface. Thus, exploring cortical gyrification in long-term meditators may provide additional clues with respect to the underlying anatomical correlates of meditation. This study examined cortical gyrification in a large sample (n = 100) of meditators and controls, carefully matched for sex and age. Cortical gyrification was established by calculating mean curvature across thousands of vertices on individual cortical surface models. Pronounced group differences indicating larger gyrification in meditators were evident within the left precentral gyrus, right fusiform gyrus, right cuneus, as well as left and right anterior dorsal insula (the latter representing the global significance maximum). Positive correlations between gyrification and the number of meditation years were similarly pronounced in the right anterior dorsal insula. Although the exact functional implications of larger cortical gyrification remain to be established, these findings suggest the insula to be a key structure involved in aspects of meditation. For example, variations in insular complexity could affect the regulation of well-known distractions in the process of meditation, such as daydreaming, mind-wandering, and projections into past or future. Moreover, given that meditators are masters in introspection, awareness, and emotional control, increased insular gyrification may reflect an integration of autonomic, affective, and cognitive processes. Due to the cross-sectional nature of this study, further research is necessary to determine the relative contribution of nature and nurture to links between cortical gyrification and meditation
Quantum Fields on the Groenewold-Moyal Plane: C, P, T and CPT
We show that despite the inherent non-locality of quantum field theories on
the Groenewold-Moyal (GM) plane, one can find a class of , ,
and invariant theories. In particular, these are theories
without gauge fields or with just gauge fields and no matter fields. We also
show that in the presence of gauge fields, one can have a field theory where
the Hamiltonian is and invariant while the -matrix
violates and .
In non-abelian gauge theories with matter fields such as the electro-weak and
sectors of the standard model of particle physics, , ,
and the product of any pair of them are broken while
remains intact for the case . (Here , : coordinate functions,
constant.) When ,
it contributes to breaking also and . It is known that the
-matrix in a non-abelian theory depends on only through
. The -matrix is frame dependent. It breaks (the identity
component of the) Lorentz group. All the noncommutative effects vanish if the
scattering takes place in the center-of-mass frame, or any frame where
, but not otherwise. and are good symmetries of the theory in this special case.Comment: 18 pages, 1 figure, revised, 2 references adde
Quantum Fields on the Groenewold-Moyal Plane
We give an introductory review of quantum physics on the noncommutative
spacetime called the Groenewold-Moyal plane. Basic ideas like star products,
twisted statistics, second quantized fields and discrete symmetries are
discussed. We also outline some of the recent developments in these fields and
mention where one can search for experimental signals.Comment: 50 pages, 3 figures. v2: published versio
Thermodynamics of the superconducting state in Calcium at 200 GPa
The thermodynamic parameters of the superconducting state in Calcium under
the pressure at 200 GPa were calculated. The Coulomb pseudopotential values
() from 0.1 to 0.3 were taken into consideration. It has been
shown, that the specific heat's jump at the critical temperature and the
thermodynamic critical field near zero Kelvin strongly decrease with
. The dimensionless ratios and
significantly differ from the predictions based on the BCS model. In
particular, decreases from 2.64 to 1.97 with the Coulomb
pseudopotential; whereas increases from 0.140 to 0.157. The numerical
results have been supplemented by the analytical approach.Comment: 7 pages, 6 figure
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Searching for life with rovers: exploration methods and science results from the 2004 field campaign of the “Life in the Atacama” project and applications to future Mars Missions
LITA develops and field tests a long-range automated rover and a science payload to search for microbial life in the Atacama. The Atacama's evolution provides a unique training ground for designing and testing exploration strategies and life detection methods for the search for life on Mars
Cytosolic chaperones influence the fate of a toxin dislocated from the endoplasmic reticulum
The plant cytotoxin ricin enters target mammalian cells by receptor-mediated endocytosis and undergoes retrograde transport to the endoplasmic reticulum (ER). Here, its catalytic A chain (RTA) is reductively separated from the cell-binding B chain, and free RTA enters the cytosol where it inactivates ribosomes. Cytosolic entry requires unfolding of RTA and dislocation across the ER membrane such that it arrives in the cytosol in a vulnerable, nonnative conformation. Clearly, for such a dislocated toxin to become active, it must avoid degradation and fold to a catalytic conformation. Here, we show that, in vitro, Hsc70 prevents aggregation of heat-treated RTA, and that RTA catalytic activity is recovered after chaperone treatment. A combination of pharmacological inhibition and cochaperone expression reveals that, in vivo, cytosolic RTA is scrutinized sequentially by the Hsc70 and Hsp90 cytosolic chaperone machineries, and that its eventual fate is determined by the balance of activities of cochaperones that regulate Hsc70 and Hsp90 functions. Cytotoxic activity follows Hsc70-mediated escape of RTA from an otherwise destructive pathway facilitated by Hsp90. We demonstrate a role for cytosolic chaperones, proteins typically associated with folding nascent proteins, assembling multimolecular protein complexes and degrading cytosolic and stalled, cotranslocational clients, in a toxin triage, in which both toxin folding and degradation are initiated from chaperone-bound states
Cytosolic chaperones influence the fate of a toxin dislocated from the endoplasmic reticulum
The plant cytotoxin ricin enters target mammalian cells by receptor-mediated endocytosis and undergoes retrograde transport to the endoplasmic reticulum (ER). Here, its catalytic A chain (RTA) is reductively separated from the cell-binding B chain, and free RTA enters the cytosol where it inactivates ribosomes. Cytosolic entry requires unfolding of RTA and dislocation across the ER membrane such that it arrives in the cytosol in a vulnerable, nonnative conformation. Clearly, for such a dislocated toxin to become active, it must avoid degradation and fold to a catalytic conformation. Here, we show that, in vitro, Hsc70 prevents aggregation of heat-treated RTA, and that RTA catalytic activity is recovered after chaperone treatment. A combination of pharmacological inhibition and cochaperone expression reveals that, in vivo, cytosolic RTA is scrutinized sequentially by the Hsc70 and Hsp90 cytosolic chaperone machineries, and that its eventual fate is determined by the balance of activities of cochaperones that regulate Hsc70 and Hsp90 functions. Cytotoxic activity follows Hsc70-mediated escape of RTA from an otherwise destructive pathway facilitated by Hsp90. We demonstrate a role for cytosolic chaperones, proteins typically associated with folding nascent proteins, assembling multimolecular protein complexes and degrading cytosolic and stalled, cotranslocational clients, in a toxin triage, in which both toxin folding and degradation are initiated from chaperone-bound states
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