39,483 research outputs found
Role of electrostatics in the texture of islands in free standing ferroelectric liquid crystal films
Curved textures of ferroelectric smectic C* liquid crystals produce space
charge when they involve divergence of the spontaneous polarization field.
Impurity ions can partially screen this space charge, reducing long range
interactions to local ones. Through studies of the textures of islands on very
thin free-standing smectic films, we see evidence of this effect, in which
materials with a large spontaneous polarization have static structures
described by a large effective bend elastic constant. To address this issue, we
calculated the electrostatic free energy of a free standing film of
ferroelectric liquid crystal, showing how the screened coulomb interaction
contributes a term to the effective bend elastic constant, in the static long
wavelength limit. We report experiments which support the main features of this
model
The cost effectiveness of integrated care for people living with HIV including antiretroviral treatment in a primary health care centre in Bujumbura, Burundi
The incremental cost effectiveness of an integrated care package (i.e., medical care including antiretroviral therapy (ART) and other services such as psychological and social support) for people living with HIV/AIDS was calculated in a not-for-profit primary health care centre in Bujumbura run by Society of Women against AIDS-Burundi (SWAA-Burundi), an African non-governmental organisation (NGO). Results are expressed as cost-effectiveness ratio 2007, constant US per DALY averted. The package of care provided by SWAA-Burundi is therefore a very cost-effective intervention in comparison with other interventions against HIV/AIDS that include ART. It is however, less cost effective than other types of interventions against HIV/AIDS, such as preventive activities
Dynamics of the molecular orientation field coupled to ions in two-dimensional ferroelectric liquid crystals
Molecular orientation fluctuations in ferroelectric smectic liquid crystals
produce space charges, due to the divergence of the spontaneous polarization.
These space charges interact with mobile ions, so that one must consider the
coupled dynamics of the orientation and ionic degrees of freedom. Previous
theory and light scattering experiments on thin free-standing films of
ferroelectric liquid crystals have not included this coupling, possibly
invalidating their quantitative conclusions. We consider the most important
case of very slow ionic dynamics, compared to rapid orientational fluctuations,
and focus on the use of a short electric field pulse to quench orientational
fluctuations. We find that the resulting change in scattered light intensity
must include a term due to the quasistatic ionic configuration, which has
previously been ignored. In addition to developing the general theory, we
present a simple model to demonstrate the role of this added term
Plaquette expectation value and lattice free energy of three-dimensional SU(N) gauge theory
We use high precision lattice simulations to calculate the plaquette
expectation value in three-dimensional SU(N) gauge theory for N=2,3,4,5,8.
Using these results, we study the N-dependence of the first non-perturbative
coefficient in the weak-coupling expansion of hot QCD. We demonstrate that, in
the limit of large N, the functional form of the plaquette expectation value
with ultraviolet divergences subtracted is 15.9(2)-44(2)/N^2.Comment: 14 pages, 6 figures. v2: references added; published versio
The electroclinic effect and modulated phases in smectic liquid crystals
We explore the possibility that the large electroclinic effect observed in
ferroelectric liquid crystals arises from the presence of an ordered array of
disclination lines and walls. If the spacing of these defects is in the
subvisible range, this modulated phase would be similar macroscopically to a
smectic A phase. The application of an electric field distorts the array,
producing a large polarization, and hence a large electroclinic effect. We show
that with suitable elastic parameters and sufficiently large chirality, the
modulated phase is favored over the smectic A and helically twisted smectic C*
phases. We propose various experimental tests of this scenario.Comment: 9 pages, 7 figures; new version includes dipolar interactions and
bend-twist couplin
XTE J1550-564: INTEGRAL Observations of a Failed Outburst
The well known black-hole X-ray binary transient XTE J1550-564 underwent an
outburst during the spring of 2003 which was substantially underluminous in
comparison to previous periods of peak activity in that source. In addition,
our analysis shows that it apparently remained in the hard spectral state over
the duration of that outburst. This is again in sharp contrast to major
outbursts of that source in 1998/1999 during which it exhibited an irregular
light curve, multiple state changes and collimated outflows. This leads us to
classify it as a "failed outburst." We present the results of our study of the
spring 2003 event including light curves based on observations from both
INTEGRAL and RXTE. In addition, we studied the evolution of the high-energy
3-300 keV continuum spectrum using data obtained with three main instruments on
INTEGRAL. These spectra are consistent with typical low-hard-state thermal
Comptonization emission. We also consider the 2003 event in the context of a
multi-source, multi-event period-peak luminosity diagram in which it is a clear
outlyer. We then consider the possibility that the 2003 event was due to a
discrete accretion event rather than a limit-cycle instablility. In that
context, we apply model fitting to derive the timescale for viscous propagation
in the disk, and infer some physical characteristics.Comment: 22 pages, 8 figures, to be published in The Astrophysical Journa
Neoseiulus californicus (Acari: Phytoseiidae, McGregor): o ácaro predador dominante em pomares comerciais de macieira conduzidos nos Sistema Convencional e Produção Integrada.
bitstream/item/60655/1/CNPUV-COM.TEC.-92.pd
Intra- and extra-cellular excretion of carboxylates
Carboxylates, such as malate and citrate, are widely acknowledged to have a central role in plant metabolism. They are involved in the production of energy and its storage as well as contributing to the cellular osmolyte pool and participating in the regulation of cellular pH. As we discuss here, recent research has demonstrated the functional importance of carboxylate excretion into the soil, apoplast and vacuole, particular with respect to the regulation of stomatal and root function
MA/BR 65 (Sambaiba): nova cultivar de soja adaptada para o Estado do Piaui.
bitstream/item/83336/1/CT870001.pd
- …