9,568 research outputs found
Pressure and chemical substitution effects in the local atomic structure of BaFe2As2
The effects of K and Co substitutions and quasi-hydrostatic applied pressure
(P<9 GPa) in the local atomic structure of BaFe2As2, Ba(Fe{0.937}Co{0.063})2As2
and Ba{0.85}K{0.15}Fe2As2 superconductors were investigated by extended x-ray
absorption fine structure (EXAFS) measurements in the As K absorption edge. The
As-Fe bond length is found to be slightly reduced (<~ 0.01 Angstroms) by both
Co and K substitutions, without any observable increment in the corresponding
Debye Waller factor. Also, this bond is shown to be compressible (k =
3.3(3)x10^{-3} GPa^{-1}). The observed contractions of As-Fe bond under
pressure and chemical substitutions are likely related with a reduction of the
local Fe magnetic moments, and should be an important tuning parameter in the
phase diagrams of the Fe-based superconductors.Comment: 7 pages, 6 figure
Quadratic optical frequency combs: Towards a new platform for multi-octave microcombs
Optical frequency comb sources based on three-wave-mixing in quadratic nonlinear materials allow for reduced pump power threshold and extended spectral coverage. We review recent progress on quadratic optical frequency combs based on second-harmonic generation and optical parametric oscillation
Permutation symmetry for the tomographic probability distribution of a system of identical particles
The symmetry properties under permutation of tomograms representing the
states of a system of identical particles are studied. Starting from the action
of the permutation group on the density matrix we define its action on the
tomographic probability distribution. Explicit calculations are performed in
the case of the two-dimensional harmonic oscillator.Comment: 13 pages, latex, no figure
Finite Temperature Casimir Effect in Randall-Sundrum Models
The finite temperature Casimir effect for a scalar field in the bulk region
of the two Randall-Sundrum models, RSI and RSII, is studied. We calculate the
Casimir energy and the Casimir force for two parallel plates with separation
on the visible brane in the RSI model. High-temperature and low-temperature
cases are covered. Attractiveness versus repulsiveness of the temperature
correction to the force is discussed in the typical special cases of
Dirichlet-Dirichlet, Neumann-Neumann, and Dirichlet-Neumann boundary conditions
at low temperature. The Abel-Plana summation formula is made use of, as this
turns out to be most convenient. Some comments are made on the related
contemporary literature.Comment: 33 pages latex, 2 figures. Some changes in the discussion. To appear
in New J. Phy
Antioxidant edible films based on bacterial cellulose and tilapia gelatin skin peptides.
In this work antioxidant films (AF) based on bacterial cellulose nanofibers (BCNF) and fish skin gelatin peptides (AFSGP) were developed. AFSGP addiction up to ~44% contributes to increase antioxidant activity (Aa) of BCNF films. The films containing AFSGP and sorbitol presented similar opacity compared to BCNF films without AFSGP. Considering the compact nanostructure, Aa, water vapour permeability and thermal stability, BCNF/AFSGP films can be used as bioactive food packing.Editor: Raul Fangueiro. ICNF. 21, 22 e 23 de jun. 2017
Improvement of imiquimod solubilization and skin retention via tpgs micelles: Exploiting the co-solubilizing effect of oleic acid
Imiquimod (IMQ) is an immunostimulant drug approved for the topical treatment of actinic keratosis, external genital-perianal warts as well as superficial basal cell carcinoma that is used off-label for the treatment of different forms of skin cancers, including some malignant melanocytic proliferations such as lentigo maligna, atypical nevi and other in situ melanoma-related diseases. Imiquimod skin delivery has proven to be a real challenge due to its very low water-solubility and reduced skin penetration capacity. The aim of the work was to improve the drug solubility and skin retention using micelles of d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), a water-soluble derivative of vitamin E, co-encapsulating various lipophilic compounds with the potential ability to improve imiquimod affinity for the micellar core, and thus its loading into the nanocarrier. The formulations were characterized in terms of particle size, zeta potential and stability over time and micelles performance on the skin was evaluated through the quantification of imiquimod retention in the skin layers and the visualization of a micelle-loaded fluorescent dye by two-photon microscopy. The results showed that imiquimod solubility strictly depends on the nature and concentration of the co-encapsulated compounds. The micellar formulation based on TPGS and oleic acid was identified as the most interesting in terms of both drug solubility (which was increased from few ”g/mL to 1154.01 ± 112.78 ”g/mL) and micellar stability (which was evaluated up to 6 months from micelles preparation). The delivery efficiency after the application of this formulation alone or incorporated in hydrogels showed to be 42-and 25-folds higher than the one of the commercial creams
Obtenção de nanocelulose extraĂda de resĂduos lignocelulĂłsicos da prensagem do mesocarpo do dendĂȘ.
- âŠ