2,097 research outputs found
Transverse Wave Propagation in Relativistic Two-fluid Plasmas in de Sitter Space
We investigate transverse electromagnetic waves propagating in a plasma in
the de Sitter space. Using the 3+1 formalism we derive the relativistic
two-fluid equations to take account of the effects due to the horizon and
describe the set of simultaneous linear equations for the perturbations. We use
a local approximation to investigate the one-dimensional radial propagation of
Alfv\'en and high frequency electromagnetic waves and solve the dispersion
relation for these waves numerically.Comment: 19 pages, 12 figure
Phase stability, elastic properties and electronic structures of Mg–Y intermetallics from first-principles calculations
AbstractThe phase stability, elastic properties and electronic structures of three typical Mg–Y intermetallics including Mg24Y5, Mg2Y and MgY are systematically investigated using first-principles calculations based on density functional theory. The optimized structural parameters including lattice constants and atomic coordinates are in good agreement with experimental values. The calculated cohesive energies and formation enthalpies show that either phase stability or alloying ability of the three intermetallics is gradually enhanced with increasing Y content. The single-crystal elastic constants Cij of Mg–Y intermetallics are also calculated, and the bulk modulus B, shear modulus G, Young's modulus E, Poisson ratio v and anisotropy factor A of polycrystalline materials are derived. It is suggested that the resistances to volume and shear deformation as well as the stiffness of the three intermetallics are raised with increasing Y content. Besides, these intermetallics all exhibit ductile characteristics, and they are isotropic in compression but anisotropic to a certain degree in shear and stiffness. Comparatively, Mg24Y5 presents a relatively higher ductility, while MgY has a relatively stronger anisotropy in shear and stiffness. Further analysis of electronic structures indicates that the phase stability of Mg–Y intermetallics is closely related with their bonding electrons numbers below Fermi level. Namely, the more bonding electrons number below Fermi level corresponds to the higher structural stability of Mg–Y intermetallics
Bailout Embeddings, Targeting of KAM Orbits, and the Control of Hamiltonian Chaos
We present a novel technique, which we term bailout embedding, that can be
used to target orbits having particular properties out of all orbits in a flow
or map. We explicitly construct a bailout embedding for Hamiltonian systems so
as to target KAM orbits. We show how the bailout dynamics is able to lock onto
extremely small KAM islands in an ergodic sea.Comment: 3 figures, 9 subpanel
Correlation between chemical composition, EHGE and TME of corn for ducks
Correlations between chemical composition, enzymatic hydrolysate gross energy (EHGE), and true metabolizable energy (TME) of corn for ducks were investigated. Twenty-two corn samples were collected from various regions in 11 provinces of China. The crude protein (CP), ether extract (EE), neutral detergent fibre (NDF), Ash, gross energy (GE), dry matter (DM), amylopectin (AP), amylose (AM), total starch (TS), and AP/AM were determined for each sample. Five of the samples of corn were chosen at the mean, mean ± 1 standard deviation (SD), and mean ± 2 SD based on AP/AM. The EHGE of these samples was analysed using the pepsin-artificial small intestinal fluid enzymatic method. These five samples were also force-fed to male Cherry Valley ducks to assay their TME. Finally, correlation analyses were performed, and regression equations were established. Ash content, GE, and TS were highly related to EHGE. Univariate prediction equations were EHGE = 11.8566Ash-0.0421 (P <0.05), EHGE = 0.1535GE1.5642 (P <0.05), and EHGE = 0.1020TS1.1561 (P <0.05). The total starch, AP/AM, and ash of the chemical compositions were highly related to TME. The corresponding univariate regression equations were TME = 21.9355TS-0.0910 (P <0.05), TME = 15.6590AP/AM-0.0559 (P <0.05), and TME = 15.0778Ash0.0442 (P <0.05). The mean EHGE was equivalent to 78.5% of TME, but their correlation coefficient was low. In conclusion, chemical composition was predictive of EHGE and TME of corn samples for ducks, but the correlation of EHGE and TME was low
Keywords: Cherry Valley duck, amylopectin, amylose, true metabolizable energ
Late Holocene isotope hydrology of Lake Qinghai, NE Tibetan Plateau: effective moisture variability and atmospheric circulation changes
A sub-centennial-resolution record of lacustrine carbonate oxygen isotopes (δ<sup>18</sup>O<sub>C</sub>) from the closed-basin Lake Qinghai on the NE Tibetan Plateau shows pronounced variability over the past 1500 years. Changes in δ<sup>18</sup>O<sub>C</sub> in hydrologically closed lakes are often interpreted in terms of changing effective moisture. Under this interpretation our record would imply increasing effective moisture during the Little Ice Age (LIA) compared to the Medieval Warm Period (MWP). However, independent evidence from other archives strongly suggests the Asian summer monsoon was stronger during the MWP and weakened during the LIA. Controls other than effective moisture (the balance of water inputs over evaporative loss) must therefore have contributed to the δ<sup>18</sup>O<sub>C</sub> values. We propose the LIA signal in Lake Qinghai resulted from a reduction in evaporation caused by colder air temperatures, coupled with a decrease in oxygen isotope composition of input waters as a result of an increase in the relative importance of westerly-derived precipitation. Our results caution against simplistic interpretations of carbonate oxygen isotope records from hydrologically closed lakes and suggest all possible controlling factors must be taken into account in order to avoid misleading palaeoclimatic reconstructions
A polarized beam splitter using an anisotropic medium slab
The propagation of electromagnetic waves in the anisotropic medium with a
single-sheeted hyperboloid dispersion relation is investigated. It is found
that in such an anisotropic medium E- and H-polarized waves have the same
dispersion relation, while E- and H-polarized waves exhibit opposite amphoteric
refraction characteristics. E- (or H-) polarized waves are positively refracted
whereas H- (or E-) polarized waves are negatively refracted at the interface
associated with the anisotropic medium. By suitably using the properties of
anomalous refraction in the anisotropic medium it is possible to realize a very
simple and very efficient beam splitter to route the light. It is shown that
the splitting angle and the splitting distance between E- and H- polarized beam
is the function of anisotropic parameters, incident angle and slab thickness.Comment: 14 pages, 6 figure
Adult attachment style across individuals and role-relationships: Avoidance is relationship-specific, but anxiety shows greater generalizability
A generalisability study examined the hypotheses that avoidant attachment, reflecting the representation of others, should be more relationship-specific (vary across relationships more than across individuals), while attachment anxiety, reflecting self-representation, should be more generalisable across a person’s relationships. College students responded to 6-item questionnaire measures of these variables for 5 relationships (mother, father, best same-gender friend, romantic partner or best opposite-gender friend, other close person), on 3 (N = 120) or 2 (N = 77) occasions separated by a few weeks. Results supported the hypotheses, with the person variance component being larger than the relationship-specific component for anxiety, and the opposite happening for avoidance. Anxiety therefore seems not to be as relationship-specific as previous research suggested. Possible reasons for discrepancies between the current and previous studies are discussed
Faraday rotation in graphene
We study magneto--optical properties of monolayer graphene by means of
quantum field theory methods in the framework of the Dirac model. We reveal a
good agreement between the Dirac model and a recent experiment on giant Faraday
rotation in cyclotron resonance. We also predict other regimes when the effects
are well pronounced. The general dependence of the Faraday rotation and
absorption on various parameters of samples is revealed both for suspended and
epitaxial graphene.Comment: 10 pp; v2: typos corrected and references added, v3, v4: small
changes and more reference
Bulk Versus Edge in the Quantum Hall Effect
The manifestation of the bulk quantum Hall effect on edge is the chiral
anomaly. The chiral anomaly {\it is} the underlying principle of the ``edge
approach'' of quantum Hall effect. In that approach, \sxy should not be taken
as the conductance derived from the space-local current-current correlation
function of the pure one-dimensional edge problem.Comment: 4 pages, RevTex, 1 postscript figur
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