9,487 research outputs found
Gluon saturation and the Froissart bound: a simple approach
At very high energies we expect that the hadronic cross sections satisfy the
Froissart bound, which is a well-established property of the strong
interactions. In this energy regime we also expect the formation of the Color
Glass Condensate, characterized by gluon saturation and a typical momentum
scale: the saturation scale . In this paper we show that if a saturation
window exists between the nonperturbative and perturbative regimes of Quantum
Chromodynamics (QCD), the total cross sections satisfy the Froissart bound.
Furthermore, we show that our approach allows us to describe the high energy
experimental data on total cross sections.Comment: 6 pages, 5 figures. Includes additional figures, discussion and
reference
A note on the cylindrical collapse of counter-rotating dust
We find analytical solutions describing the collapse of an infinitely long
cylindrical shell of counter-rotating dust. We show that--for the classes of
solutions discussed herein--from regular initial data a curvature singularity
inevitably develops, and no apparent horizons form, thus in accord with the
spirit of the hoop conjecture.Comment: 8 pages, LaTeX, ijmpd macros (included), 1 eps figure; accepted for
publication in Int. J. Mod. Phys.
Multilayer Complex Network Descriptors for Color-Texture Characterization
A new method based on complex networks is proposed for color-texture
analysis. The proposal consists on modeling the image as a multilayer complex
network where each color channel is a layer, and each pixel (in each color
channel) is represented as a network vertex. The network dynamic evolution is
accessed using a set of modeling parameters (radii and thresholds), and new
characterization techniques are introduced to capt information regarding within
and between color channel spatial interaction. An automatic and adaptive
approach for threshold selection is also proposed. We conduct classification
experiments on 5 well-known datasets: Vistex, Usptex, Outex13, CURet and MBT.
Results among various literature methods are compared, including deep
convolutional neural networks with pre-trained architectures. The proposed
method presented the highest overall performance over the 5 datasets, with 97.7
of mean accuracy against 97.0 achieved by the ResNet convolutional neural
network with 50 layers.Comment: 20 pages, 7 figures and 4 table
No-horizon theorem for spacetimes with spacelike G1 isometry groups
We consider four-dimensional spacetimes which obey the
Einstein equations , and admit a global spacelike
isometry group. By means of dimensional reduction and local
analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on
which guarantees that cannot contain apparent
horizons. Given any (3+1) spacetime with spacelike translational isometry, the
no-horizon condition can be readily tested without the need for dimensional
reduction. This provides thus a useful and encompassing apparent horizon test
for -symmetric spacetimes. We argue that this adds further evidence
towards the validity of the hoop conjecture, and signals possible violations of
strong cosmic censorship.Comment: 8 pages, LaTeX, uses IOP package; published in Class. Quantum Gra
Characterization of the self-assembly process of hydrophobically modified dextrin
Hydrophobized dextrin, randomly substituted by long alkyl chain (C16), forms stable
hydrogel nanoparticles by self-assembling in water. Hydrophobic chains, distributed along
the polymer backbone, promote the formation of hydrophobic microdomains within the
nanoparticles. The influence of degree of substitution with hydrophobic chains (DSC16)
on nanoparticles size, colloidal stability, density, aggregation number and nanoparticle
weight was studied. Size distribution was also evaluated at different pH, urea concentration
and ionic strength conditions. As shown by dynamic light scattering and transmission
electron microscopy, the particles are spherical having a diameter of about 20 nm. The
more substituted polymer forms more densely packed hydrophobic microdomains, such
that the colloidal stability (in water and PBS buffer) of nanoparticles is increased. The
knowledge of the aggregate building process and the characteristics of the nanoparticles
are crucial for the design of drug delivery systems.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/22242/2005, POCTI/
BIO/45356/2002
Improving cost-efficiency for MPs density separation by zinc chloride reuse
The methodology used to extract and quantify microplastics (MPs) in aquatic systems are still not standardized. Salt saturated solutions, such as sodium chloride (NaCl), zinc chloride (ZnCl2) and/or sodium iodide (NaI), are normally added to separate dense plastics from aquatic samples. However, the most effective reagents are also the most expensive (e.g. ZnCl2 and NaI). To decrease this cost, a reuse process of the salt solutions should be applied. The reuse process has been widely investigated for the NaI solution neglecting the ZnCl2. Hence, the aim of this study was to present a simple methodology to reuse the ZnCl2 solution ensuring the efficiency of the product. Results of the present study showed that ZnCl2 solution could be reused at least five times maintaining an efficiency above 95 %. •The ZnCl2 reuse decreases the cost of the methodology.•The efficiency of ZnCl2 solution after five filtrations remains above 95 % (all polymers are detected and recovered).•The use of this salt solution is the most cost-effective methodology to isolate MPs from aquatic samples.publishe
Self-assembled hydrogel nanoparticles for drug delivery applications
Hydrogel nanoparticles—also referred to as polymeric nanogels or
macromolecular micelles—are emerging as promising drug carriers for therapeutic
applications. These nanostructures hold versatility and properties suitable for the delivery
of bioactive molecules, namely of biopharmaceuticals. This article reviews the latest
developments in the use of self-assembled polymeric nanogels for drug delivery
applications, including small molecular weight drugs, proteins, peptides, oligosaccharides,
vaccines and nucleic acids. The materials and techniques used in the development of
self-assembling nanogels are also described
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