15,139 research outputs found
Numerical simulation of the twist-grain-boundary phase of chiral liquid crystals
We study the core structure of the twist-grain-boundary (TGB) phase of chiral
liquid crystals by numerically minimizing the Landau-de Gennes free energy. We
analyze the morphology of layers at the grain boundary, to better understand
the mechanism of frustration between the smectic layer order and chirality. As
the chirality increases, the effective bending rigidity of layers is reduced
due to unlocking of the layer orientation and the director. This results in
large deviation of the layer morphology from that of Scherk's first minimal
surface and linear stack of screw dislocations (LSD).Comment: 4 pages and 6 figure
Recommended from our members
Vertical and meridional distributions of the atmospheric CO2 mixing ratio between northern midlatitudes and southern subtropics
The atmospheric CO2 mixing ratio was measured using a continuous measurement system onboard a Gulfstream-II aircraft between the northern midlatitudes and the southern subtropics during the Biomass Burning and Lightning Experiment Phase A (BIBLE A) campaign in September-October 1998. The vertical distribution Of CO2 over tropical regions was almost constant from the surface to an altitude of 13 km. CO2 enhancements from biomass burning and oceanic release were observed in the tropical boundary layer. Measurements in the upper troposphere indicate interhemispheric exchange was effectively suppressed between 2°N-7°N. Interhemispheric transport of air in the upper troposphere was suppressed effectively in this region. The CO2 mixing ratios in the Northern and Southern Hemispheres were almost constant, with an average value of about 365 parts per million (ppm) and 366 ppm, respectively. The correlation between the CO2 and NOy mixing ratios observed north of 7°N was apparently different from that obtained south of 2°N. This fact strongly supports the result that the north-south boundary in the upper troposphere during BIBLE A was located around 2°N-7°N as the boundary is not necessary a permanent feature
Equilibrium states and their entropy densities in gauge-invariant C*-systems
A gauge-invariant C*-system is obtained as the fixed point subalgebra of the
infinite tensor product of full matrix algebras under the tensor product
unitary action of a compact group. In the paper, thermodynamics is studied on
such systems and the chemical potential theory developed by Araki, Haag,
Kastler and Takesaki is used. As a generalization of quantum spin system, the
equivalence of the KMS condition, the Gibbs condition and the variational
principle is shown for translation-invariant states. The entropy density of
extremal equilibrium states is also investigated in relation to macroscopic
uniformity.Comment: 20 pages, revised in March 200
Polymers in Curved Boxes
We apply results derived in other contexts for the spectrum of the Laplace
operator in curved geometries to the study of an ideal polymer chain confined
to a spherical annulus in arbitrary space dimension D and conclude that the
free energy compared to its value for an uncurved box of the same thickness and
volume, is lower when , stays the same when , and is higher when
\mbox{}. Thus confining an ideal polymer chain to a cylindrical shell,
lowers the effective bending elasticity of the walls, and might induce
spontaneous symmetry breaking, i.e. bending. (Actually, the above mentioned
results show that {\em {any}} shell in induces this effect, except for
a spherical shell). We compute the contribution of this effect to the bending
rigidities in the Helfrich free energy expression.Comment: 20 pages RevTeX, epsf; 4 figures; submitted to Macromoledule
Energy Dependence of Breakup Cross Sections of Halo Nucleus 8B and Effective Interactions
We study the energy dependence of the cross sections for nucleon removal of
8B projectiles. It is shown that the Glauber model calculations with
nucleon-nucleon t-matrix reproduce well the energy dependence of the breakup
cross sections of 8B. A DWBA model for the breakup cross section is also
proposed and results are compared with those of the Glauber model. We show that
to obtain an agreement between the DWBA calculations, the Glauber formalism,
and the experimental data, it is necessary to modify the energy behavior of the
effective interaction. In particular, the breakup potential has a quite
different energy dependence than the strong absorption potential.Comment: 13 pages, 4 figure
Expression of the Aeluropus littoralis AlSAP gene enhances rice yield under field drought at the reproductive stage
We evaluated the yields of Oryza sativa L. 'Nipponbare' rice lines expressing a gene encoding an A20/AN1 domain stress-associated protein, AlSAP, from the halophyte grass Aeluropus littoralis under the control of different promoters. Three independent field trials were conducted, with drought imposed at the reproductive stage. In all trials, the two transgenic lines, RN5 and RN6, consistently out-performed non-transgenic (NT) and wild-type (WT) controls, providing 50â90% increases in grain yield (GY). Enhancement of tillering and panicle fertility contributed to this improved GY under drought. In contrast with physiological records collected during previous greenhouse dry-down experiments, where drought was imposed at the early tillering stage, we did not observe significant differences in photosynthetic parameters, leaf water potential, or accumulation of antioxidants in flag leaves of AlSAP-lines subjected to drought at flowering. However, AlSAP expression alleviated leaf rolling and leaf drying induced by drought, resulting in increased accumulation of green biomass. Therefore, the observed enhanced performance of the AlSAP-lines subjected to drought at the reproductive stage can be tentatively ascribed to a primed status of the transgenic plants, resulting from a higher accumulation of biomass during vegetative growth, allowing reserve remobilization and maintenance of productive tillering and grain filling. Under irrigated conditions, the overall performance of AlSAP-lines was comparable with, or even significantly better than, the NT and WT controls. Thus, AlSAP expression inflicted no penalty on rice yields under optimal growth conditions. Our results support the use of AlSAP transgenics to reduce rice GY losses under drought conditions. (RĂ©sumĂ© d'auteur
Sustainability strategies and stakeholder management for upland farming
Upland farming provides important benefits to society. To retain these benefits, measures to encourage farms to adopt practices that balance economic, environmental and social aspects of sustainability are required. This study used survey data from a sample of farms located in less-favoured areas in Northern England to identify the trade-offs between the three dimensions of farm-level sustainability and the impacts of farm behaviours on them, including diversification, participation in agri-environmental policies and stakeholder management. Results showed that farm businesses may face a trade-off between improving economic and environmental performance through their decisions about participating in agri-environmental schemes and that strengthening relationships with some stakeholders is critical for achieving sustainability. This suggests that future policy design may simultaneously improve three dimensions of sustainability by promoting environmental conservation activities through non-economic incentives and by encouraging farm businesses to build good working relationships with their stakeholders
Chaos and Geodynamics: Mélanges, Mélange-forming Processes and Their Significance in the Geological Record
Spin Gap in a Doped Kondo Chain
We show that the Kondo chain away from half-filling has a spin gap upon the
introduction of an additional direct Heisenberg coupling between localized
spins. This is understood in the weak-Kondo-coupling limit of the
Heisenberg-Kondo lattice model by bosonization and in the strong-coupling limit
by a mapping to a modified t-J model. Only for certain ranges of filling and
Heisenberg coupling does the spin gap phase extend from weak to strong
coupling.Comment: 4 pages RevTeX including 4 eps figures; minor corrections and
clarification
- âŠ