756 research outputs found
A closer look at the explanation of the ATOMKI nuclear anomalies
We revisit the gauged explanation of the ATOMKI nuclear
anomalies, in which the new gauge boson is the hypothetical particle.
It is known that the vanilla scenario is unable to account for
appropriate couplings, namely the suppression of the couplings of to
neutrinos, which motivates adding vector-like leptons. The simplest case, in
which the new fields have charges equal to , is highly disfavoured
since it requires large mixing with the Standard Model fields. One solution
recently put forward is to consider large charges to counterbalance small
mixing. We show that, in this scenario, and after taking into account several
phenomenological constraints, the dominant contribution to the muon anomalous
magnetic moment is expected to be extremely large and with a
negative sign, being thus excluded by experiment.Comment: 15 LaTeX pages, 4 figure
Preparation of bioactive coatings on the surface of bioinert polymers through an innovative auto-catalytic electroless route
The aim of this research was to develop a new methodology to obtain bioactive coatings
on bioinert and biodegradable polymers that are not intrinsically bioactive. In this study, three types
of materials were used as substrates: (i) high molecular weight polyethylene (HMWPE) and two
different types of starch based blends (ii) starch/ethylene vinyl alcohol blends, SEVA-C, and (iii)
starch/cellulose acetate blends, SCA. These materials were obtained by injection moulding and by
extrusion with blowing agents in order to obtain compact/porous 3D architectures. Three types of
baths were developed in order to produce the newly proposed auto-catalytic Ca-P coatings: (i)
alkaline, (ii) acid, and (iii) oxidant bath. The obtained results indicated that it was possible to coat
the materials surfaces with calcium phosphate (Ca-P) layer with only 60 min of immersion in the
different types of auto-catalytic solutions. These innovative auto-catalytic electroless route allows
for the production of an adherent bioactive film on the polymeric surfaces. Furthermore, it was
possible observe by SEM/EDS the clear bioactive nature of the Ca-P coatings after different
immersion periods, in a simulated body fluid (SBF)
Surgical correction of scoliosis: Numerical analysis and optimization of the procedure
A previously developed model is used to numerically simulate real clinical cases of the surgical correction of scoliosis. This model consists of one-dimensional finite elements with spatial deformation in which (i) the column is represented by its axis; (ii) the vertebrae are assumed to be rigid; and (iii) the deformability of the column is concentrated in springs that connect the successive rigid elements. The metallic rods used for the surgical correction are modeled by beam elements with linear elastic behavior. To obtain the forces at the connections between the metallic rods and the vertebrae geometrically, non-linear finite element analyses are performed. The tightening sequence determines the magnitude of the forces applied to the patient column, and it is desirable to keep those forces as small as possible. In this study, a Genetic Algorithm optimization is applied to this model in order to determine the sequence that minimizes the corrective forces applied during the surgery. This amounts to find the optimal permutation of integers 1, ... , n, n being the number of vertebrae involved. As such, we are faced with a combinatorial optimization problem isomorph to the Traveling Salesman Problem. The fitness evaluation requires one computing intensive Finite Element Analysis per candidate solution and, thus, a parallel implementation of the Genetic Algorithm is developed
Assessment of different coastal defence structures to promote wave energy dissipation and sediments retention
Coastal areas are an apprized environment by society that will continue
to expand rapidly. Traditional coastal protection structures are commonly deployed to protect coastal areas endangered by natural extreme weather events.
However, due to their limited efficiency and very high costs, more efficient and
sustainable strategies to deal with coastal erosion are imperative.
This research work focuses on the assessment of engineering solutions to mitigate and delay coastal erosion. Three different structure geometries (triangular
prism shape, single detached breakwater and group of two detached breakwaters)
are analysed on a realistic bathymetry, using a combination of numerical models
(SWAN and XBeach) to study the influence of those structures on the coastal
hydro- and morphodynamics. SWAN was used for hydrodynamics and XBeach
for hydrodynamics and morphodynamics assessments. In addition, a comparison
between SWAN and XBeach hydrodynamics results was also performed.
Structures considered in this study have regular shaped geometries, and are characterized in terms of their efficiency regarding wave height and wave energy dissipation considering different wave regimes and performance in terms of longterm beach morphodynamic impact (sediments accumulation and erosion). The
analysis is concentrated in two scenarios, one for low and the other for highly
energetic hydrodynamics (the most challenging to coastal zones defence). The
obtained results allowed classifying their performance in terms of the impact on
wave energy and wave height dissipation, and sediment erosion/deposition patterns.This work is supported by the Portuguese Foundation for Science and Technology
(FCT) [PhD grant number SFRH/BD/141381/2018]. The authors also acknowledge
the support provided by the project EcOffShorBe – Eco Offshore Built Environment,
n. 37417, R&D cores in Copromoção, 14/SI/2017, NORTE-01-0247-FEDER-037417,
supported by ANI (FEDER)
Analysis of the interfacial debonding behaviour of NSM CFRP laminates with cement-based adhesive using Digital Image Correlation technique
The superb performance of carbon fiber reinforced polymer (CFRP)
composites as near surface mounted (NSM) reinforcement in strengthening solutions for structures is already well recognized. Due to their deficiencies in fire
conditions, cement-based adhesives as an alternative to polymeric matrices are
recently suggested as a solution in these systems. However, the interface between
the CFRP laminate and cement-based adhesives should have good stress transferring capacity. Thus, it is of great importance the research on improving this
interface to increase the bonding capacity of CFRP/cement-based adhesive system. For that purpose, pull-out tests were conducted to examine the interfacial
debonding process of two types of CFRP laminates: conventional smooth surface
laminates and sand surface treated laminates. Digital image correlation (DIC)
technique was used to verify the potentiality of the proposed sand treating approach. Therefore, the interlocking mechanism of sand treated laminates with the
developed cement-based adhesive is assessed and the results are compared to
those with non-treated smooth surface laminates. Furthermore, the bond-slip behaviour from pull-out tests is compared to obtained data through the DIC technique. The results verified the effectiveness of sand treatment approach applied
to NSM CFRP reinforcements. Moreover, the DIC technique has revealed capable of providing qualitative and quantitative information in this regardFCT through the PTDC/ECMEST/1882/2014 FIRECOMPOSITE projec
Toxicological Study Employing Repeated Doses of Garcinielliptone FC, a Polyisoprenylated-Benzophenone Isolated from Seed of Platonia Insignis Mart
The major constituent from the hexane extract of the seeds of P. insignis is GFC (garcinielliptone FC). Doses of 25, 50and 75 mg/kg of GFC were aseptically suspended in 0.05% Tween 80 dissolved in 0.9% saline (vehicle) and orally administered for30, 90 and 120 consecutive days to adult Swiss mice. In this work, the repeated oral administration, in animals of both sexes,demonstrates that this compound is not able to induce mortality and/or behavioral changes in adult mice. In addition, body weightgain, feed intake and disposal of excreta were not altered by the administration of this compound with repeated doses. Furthermore,no differences in weight and macroscopic structure of the brain, liver, kidney, lung, heart and spleen between groups of male andfemale adult mice were observed after treatment. During the periods of treatment, GFC produced no significant changes onhaematological and biochemical parameters in male and female mice treated with all doses used. The aim of this study was toinvestigate the toxicological potential of GFC through behavioral, hematological, biochemical and morphological parameters inanimals in order to ensure the safe use of Platonia insignis in folk medicine.Fil: Silva, Ana P.. Federal University of PiauÃ; BrasilFil: Filho, José Carlos C. L. S.. North Union of Parana; BrasilFil: da Costa Júnior, Joaquim S.. Federal Institute of PiauÃ; BrasilFil: Peláez, Walter José. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en FÃsico-quÃmica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias QuÃmicas. Instituto de Investigaciones en FÃsico-quÃmica de Córdoba; ArgentinaFil: Faillace, MartÃn Sebastián. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en FÃsico-quÃmica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias QuÃmicas. Instituto de Investigaciones en FÃsico-quÃmica de Córdoba; ArgentinaFil: Falcão Ferraz, Alexandre de B.. Lutheran University of Brazil; BrasilFil: David, Jorge M.. Institute Of Chemistry, Federal University Of Bahia; Brasil. Universidade Federal da Bahia; BrasilFil: Freitas, Rivelilson M.. Federal University of Bahia; Brasi
Calcium-phosphate derived from mineralized algae for bone tissue engineering applications
In this work, several routes are described towards obtaining pure inorganic phases derived from Coralline officinallis red algae. The scanning
electron microscopy studies have shown that it becomes possible not only to eliminate the undesired organic phase, but also to preserve or tailor
the red algae typical microporosity. X-ray diffraction analysis was used to investigate the phase content of the red algae before and after
performing the different treatment routes. Hydroxyapatite nanocrystallites were obtained after converting the coralline calcium carbonate skeleton
by means of combining thermal and chemical routes. These results were confirmed by Fourier transform infra-red spectroscopic analysis. The
processing routes herein described are very promising in order to design bioceramics of algae origin that might find useful applications as bone
fillers and tissue engineering scaffolds
Rheological and mechanical properties of acellular and cellladen methacrylated gellan gum hydrogels
Tissue engineered hydrogels hold great potential as nucleus pulposus substitutes (NP), as they promote intervertebral disc (IVD) regeneration and re-establish its original function. But, the key to their success in future clinical applications greatly depends on its ability to replicate the native 3D micro-environment and circumvent their limitation in terms of mechanical performance. In the present study, we investigated the rheological/mechanical properties of both ionic- (iGG-MA) and photo-crosslinked methacrylated gellan gum (phGG-MA) hydrogels. Steady shear analysis, injectability and confined compression stress-relaxation tests were carried out. The injectability of the reactive solutions employed for the preparation of iGG-MA and phGG-MA hydrogels was firstly studied, then the zero-strain compressive modulus and permeability of the acellular hydrogels were evaluated.In addition, human intervertebral disc (hIVD) cells encapsulated in both iGG-MA and phGG-MA hydrogels were cultured in vitro, and its mechanical properties also investigated under dynamic mechanical analysis at 37ºC and pH 7.4. After 21 d of culturing, hIVD cells were alive (Calcein AM) and the E’ of ionic-crosslinked hydrogels and photo-crosslinked was higher than that observed for acellular hydrogels. Our study suggests that methacrylated gellan gum hydrogels present promising mechanical and biological performance as hIVD cells were producing extracellular matrix
Fractal Dimension and Localization of DNA Knots
The scaling properties of DNA knots of different complexities were studied by
atomic force microscope. Following two different protocols DNA knots are
adsorbed onto a mica surface in regimes of (i) strong binding, that induces a
kinetic trapping of the three-dimensional (3D) configuration, and of (ii) weak
binding, that permits (partial) relaxation on the surface. In (i) the gyration
radius of the adsorbed DNA knot scales with the 3D Flory exponent within error. In (ii), we find , a value between the 3D
and 2D () exponents, indicating an incomplete 2D relaxation or a
different polymer universality class. Compelling evidence is also presented for
the localization of the knot crossings in 2D.Comment: 4 pages, 3 figure
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