313 research outputs found
Microencapsulation by coacervation of biodegradable polymer with thyme oil
The objective of this work is to develop a novel coacervation process to produce
microcapsules of PLA to encapsulate thyme oil that will be used in cosmetics. PLA is
soluble in organic solvents but insoluble in water. Generally, PLA is used to encapsulate
water soluble active principles such as drugs, pesticides and dye-stuffs by coacervation,
mainly by means of microspheres production or by using double emulsion techniques
(o/w/o). However, the objective of this work is to encapsulate thyme oil, a water
insoluble active principle that needs, in a first step, the preparation of an oil-in-water
emulsion. The novelty of our process consists on dissolving PLA in dimethylformamide
(DMF) which is a good solvent for PLA but in addition has high solubility in water.
Upon contact with water, the homogeneous solution of PLA in DMF, promotes the
precipitation of PLA around the thyme oil core. With this work we demonstrate a new,
easy and executable method of coacervation by introducing modifications on
microencapsulation process that allow the encapsulation of an oily active principle by
simply preparing an o/w emulsion. Control of size and wall thickness of microcapsules,
encapsulation efficiency, the influence of surfactants and release of thyme oil were
studied. The produced microcapsules have bimodal particle size distributions in volume
with a mean particle size of 40 ÎĽm. Microcapsules analysis by microscopy have
confirmed the spherical shape, the rough surface, and allowed the estimation of the wall
thickness around 5 ÎĽm. Quantification of the encapsulated thyme oil was performed by
gas chromatography and allowed to evaluate the quality of the encapsulated oil and
pointed out for a preferential encapsulation of thyme oil apolar compounds.FCT: Grant SFRH/BD/43215/2008
Microencapsulation of limonen oil for textile application
The production of polyurethane-urea microcapsules using the interfacial polymerization technology was performed. Microcapsules were produced in a basic IKA® Miniplant laboratory reactor, in order to produce microcapsules with controlled parameters. In this formulation, limonene, a fragrant chemical characteristic of the lemon oil - was microencapsulated, because lemon oil is the most used oil in perfumery. It resulted in microcapsules with bimodal distribution and average size equal to 10µm. The characterisation of the microcapsules includes particle size distribution, optical microscopy and scanning electron microscopy. Using scanning electron microscopy it is visible the presence of well defined microcapsules on the woven.Project SCENTFASHION, contract
ADI/2004/M2.3/0015POCI funded by Agência de Inovação(AdI) in the framework of POCI 2010-Medida 2.3-IDEIA
Synthesis of polyurethane-urea microcapsules with perfume for textile application
This work is a contribution to the introduction of emergent technologies in the textile sector, namely the microencapsulation of fragrances and its application to obtain added-value products. Polyurethane/urea microcapsules with a perfume have been produced using the interfacial polymerization technology for industrial application on textile substrate having in view man suits production.
The specific objective of this work is the production of a scented clothing line, which includes:
Development of technologies/processes for the production of microcapsules;
Incorporation of microcapsules into textile substrates and optimization of the process in a laboratory;
Validation and industrial scale-up;
Development of testing methods and analysis of the release of the perfume.SCENTFASHION, contract ADI/2004/M2.3/0015POC
The Role of Career Shocks in Contemporary Career Development: Key Challenges and Ways Forward
Effectiveness of the global protected area network in representing species diversity
The Fifth World Parks Congress in Durban, South Africa, announced in September 2003 that the global network of protected areas now covers 11.5% of the planet's land surface. This surpasses the 10% target proposed a decade earlier, at the Caracas Congress, for 9 out of 14 major terrestrial biomes. Such uniform targets based on percentage of area have become deeply embedded into national and international conservation planning. Although politically expedient, the scientific basis and conservation value of these targets have been questioned. In practice, however, little is known of how to set appropriate targets, or of the extent to which the current global protected area network fulfils its goal of protecting biodiversity. Here, we combine five global data sets on the distribution of species and protected areas to provide the first global gap analysis assessing the effectiveness of protected areas in representing species diversity. We show that the global network is far from complete, and demonstrate the inadequacy of uniform—that is, 'one size fits all'—conservation targets
Transforming growth factor-β (TGF-β) maintains follicular ultrastructure and stimulates preantral follicle growth in caprine ovarian tissue cultured in vitro
O objetivo desse estudo foi investigar se o TGF-β afeta a sobrevivĂŞncia, ativação e crescimento de folĂculos primordiais caprinos inclusos no cĂłrtex ovariano apĂłs o cultivo in vitro. Ovários de cabras foram coletados em abatedouro e fragmentos de tecido ovariano foram cultivados por um e sete dias em meio essencial mĂnimo alfa (α-MEM+) sozinho ou suplementado com TGF-β (1, 5, 10 ou 50ng/mL). Fragmentos ovarianos nĂŁo cultivados e cultivados foram processados para análise histolĂłgica e ultraestrutural. Os resultados mostraram que, comparado ao controle fresco, houve diminuição no percentual de folĂculos morfologicamente normais em todos os tratamentos somente apĂłs sete dias de cultivo. O TGF-β nĂŁo afetou a ativação folicular independente da concentração testada, contudo, o diâmetro folicular foi superior (P<0.05) no tratamento com 10ng/mL de TGF-β quando comparado ao controle fresco e aos demais tratamentos. AlĂ©m disso, essa mesma concentração manteve a ultraestrutura normal dos folĂculos apĂłs sete dias de cultivo. Em conclusĂŁo, o TGF-β apresentou efeito adicional no crescimento folicular e na manutenção da integridade ultraestrutural de folĂculos prĂ©-antrais caprinos inclusos no tecido ovariano quando utilizado na concentração de 10ng/mL durante sete dias de cultivo.The objectives of this study were to investigate whether TGF-β affect the survival, activation and further growth of goat primordial follicles enclosed in ovarian cortex after in vitro culture. Goat ovaries were collected from an abattoir and pieces of ovarian tissues were cultured for one or seven days in a supplemented alpha Minimum Essential Medium, alone or containing TGF-β (1, 5, 10 or 50ng/mL). Ovarian tissues from the fresh control as well as those cultured were processed for histological and ultrastructural studies. The results showed that when compared with fresh control, there was decrease in the percentages of histologically normal follicles in all treatments only after seven days culture. TGF-β did not affect the activation of preantral follicles regardless of its concentration, however, larger follicles diameter (P<0.05) was observed using 10ng/mL TGF-β than in the fresh control and other treatments. Moreover, this concentration maintained the normal ultrastructure after seven days of culture. In conclusion, TGF-β showed additional effect on the follicle growth and the maintenance of ultrastructural integrity of goat preantral follicles enclosed in ovarian tissue when used at 10ng/mL during seven days of culture
Density functional method for nonequilibrium electron transport
We describe an ab initio method for calculating the electronic structure,
electronic transport, and forces acting on the atoms, for atomic scale systems
connected to semi-infinite electrodes and with an applied voltage bias. Our
method is based on the density functional theory (DFT) as implemented in the
well tested Siesta approach (which uses non-local norm-conserving
pseudopotentials to describe the effect of the core electrons, and linear
combination of finite-range numerical atomic orbitals to describe the valence
states). We fully deal with the atomistic structure of the whole system,
treating both the contact and the electrodes on the same footing. The effect of
the finite bias (including selfconsistency and the solution of the
electrostatic problem) is taken into account using nonequilibrium Green's
functions. We relate the nonequilibrium Green's function expressions to the
more transparent scheme involving the scattering states. As an illustration,
the method is applied to three systems where we are able to compare our results
to earlier ab initio DFT calculations or experiments, and we point out
differences between this method and existing schemes. The systems considered
are: (1) single atom carbon wires connected to aluminum electrodes with
extended or finite cross section, (2) single atom gold wires, and finally (3)
large carbon nanotube systems with point defects.Comment: 18 pages, 23 figure
Landau-Zener-Stuckelberg interferometry
A transition between energy levels at an avoided crossing is known as a
Landau-Zener transition. When a two-level system (TLS) is subject to periodic
driving with sufficiently large amplitude, a sequence of transitions occurs.
The phase accumulated between transitions (commonly known as the Stuckelberg
phase) may result in constructive or destructive interference. Accordingly, the
physical observables of the system exhibit periodic dependence on the various
system parameters. This phenomenon is often referred to as
Landau-Zener-Stuckelberg (LZS) interferometry. Phenomena related to LZS
interferometry occur in a variety of physical systems. In particular, recent
experiments on LZS interferometry in superconducting TLSs (qubits) have
demonstrated the potential for using this kind of interferometry as an
effective tool for obtaining the parameters characterizing the TLS as well as
its interaction with the control fields and with the environment. Furthermore,
strong driving could allow for fast and reliable control of the quantum system.
Here we review recent experimental results on LZS interferometry, and we
present related theory.Comment: 34 single-column pages, 11 figure
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
- …