316 research outputs found
Chiral Perturbation Theory with tensor sources
We construct the most general chirally-invariant Lagrangian for mesons in the
presence of external sources coupled to the tensor current
\bar{\psi}\sigma_{\mu\nu}\psi. In order to have only even terms in the chiral
expansion, we consider the new source of O(p^2). With this choice, we build the
even-parity effective Lagrangian up to the p^6-order (NLO). While there are
only 4 new terms at the p^4-order, at p^6-order we find 78 terms for n_f=2 and
113 terms for n_f=3. We provide a detailed discussion on the different
mechanisms that ensure that our final set of operators is complete and
non-redundant. We also examine the odd-parity sector, to conclude that the
first operators appear at the p^8-order (NNLO).Comment: 23 pages, one figure; typos corrected, one paragraph added, new
section added, references added, published versio
On the development and application of intrusive sensors for two-phase flows characterization in complez environments
Intrusive sensors are widely employed in numerous industrial applications to determine the phase fraction in gas-liquid two-phase flows. Such applications include those in the chemical, nuclear, and oil industries. This study aims to investigate the use of three distinct intrusive sensor topologies, specifically intended for underwater applications, wherein the detailed characterization of the disperse phase is the primary objective. Examples of such applications include aeration diffusers in wastewater treatment plants (WWTPs) and fish farming facilities.Peer Reviewe
Avaliação da morfologia radicular de genótipos de milho sob estresse de fósoforo através da analise de imagens digitais.
Experimental adiabatic vortex ratchet effect in Nb films with asymmetric pinning trap
Nb films grown on top of an array of asymmetric pinning centers show a vortex ratchet effect. A net flow of vortices is induced when the vortex lattice is driven by fluctuating forces on an array of pinning centers without reflection symmetry. This effect occurs in the adiabatic regime and it could be mimiced only by reversible DC driven forces
Development of a three-dimensional cell culture system based on microfluidics for nuclear magnetic resonance and optical monitoring.
A new microfluidic cell culture device compatible with real-time nuclear magnetic resonance (NMR) is presented here. The intended application is the long-term monitoring of 3D cell cultures by several techniques. The system has been designed to fit inside commercially available NMR equipment to obtain maximum readout resolution when working with small samples. Moreover, the microfluidic device integrates a fibre-optic-based sensor to monitor parameters such as oxygen, pH, or temperature during NMR monitoring, and it also allows the use of optical microscopy techniques such as confocal fluorescence microscopy. This manuscript reports the initial trials culturing neurospheres inside the microchamber of this device and the preliminary images and spatially localised spectra obtained by NMR. The images show the presence of a necrotic area in the interior of the neurospheres, as is frequently observed in histological preparations; this phenomenon appears whenever the distance between the cells and fresh nutrients impairs the diffusion of oxygen. Moreover, the spectra acquired in a volume of 8 nl inside the neurosphereshow an accumulation of lactate and lipids, which are indicative of anoxic condi-tions. Additionally, a basis for general temperature control and monitoring and a graphical control software have been developed and are also described. The complete platform will allow biomedical assays of therapeutic agents to be performed in the early phases of therapeutic development. Thus, small quantities of drugs or advanced nanodevices may be studied long-term under simulated living conditions that mimic the flow and distribution of nutrient
Experimental vortex ratchet effect in nanostructured superconductors
Superconducting Nb thin films were grown on different arrays of triangle-shape metallic islands. The vortex lattice dynamics could be strongly modified by these asymmetric vortex traps. These asymmetric pinning potentials lead to a rectification effect on the vortex motion: Injecting an ac supercurrent on the sample yields a net dc vortex flow. This vortex ratchet ffect is adiabatic and reversible: The effect is frequency independent and the polarity of the dc voltage output could be tuned by the applied magnetic fields and the input ac currents
Magnetic order of Cr thin films in Nb/Cr/Fe-nanoisland hybrid: a comparative study between magnetic and superconducting properties
Shifted hysteresis loops characteristic of the exchange bias effect between a ferromagnet and an antiferromagnet are demonstrated in structures formed by a 2.5 nm Cr layer deposited on top of an array of Fe nanoislands (Cr/Fe-nanoislands). This effect evidences the persistence of antiferromagnetic (AF) order for Cr layers much thinner than the thickness reported in the literature. The field shift measured is found to increase for the smallest island sizes, which can be related with the enhancement of the Fe-nanoisland surface to volume ratio. The comparative study between superconducting proximity effects in Nb/Cr/Fe-nanoislands and Nb/normal metal/Fe-nanoisland hybrids (where the normal metals used are Al and Pt) confirms the presence of AF order in the 2.5 nm Cr spacer layer. A much shorter penetration depth of the Cooper pairs into the AF Cr layers than in the normal metal Pt and Al spacer layers is deduced
Directional vortex motion guided by artificially induced mesoscopic potentials
Rectangular pinning arrays of Ni dots define a potential landscape for vortex
motion in Nb films. Magnetotransport experiments in which two in-plane
orthogonal electrical currents are injected simultaneously allow selecting the
direction and magnitude of the Lorentz force on the vortex-lattice, thus
providing the angular dependence of the vortex motion. The background
dissipation depends on angle at low magnetic fields, which is progressively
smeared out with increasing field. The periodic potential locks in the vortex
motion along channeling directions. Because of this, vortex-lattice direction
of motion is up to 85o away from the applied Lorentz force direction.Comment: PDF file includes figure
Control of the chirality and polarity of magnetic vortices in triangular nanodots
Magnetic vortex dynamics in lithographically prepared nanodots is currently a
subject of intensive research, particularly after recent demonstration that the
vortex polarity can be controlled by in-plane magnetic field. This has
stimulated the proposals of non-volatile vortex magnetic random access
memories. In this work, we demonstrate that triangular nanodots offer a real
alternative where vortex chirality, in addition to polarity, can be controlled.
In the static regime, we show that vortex chirality can be tailored by applying
in-plane magnetic field, which is experimentally imaged by means of
Variable-Field Magnetic Force Microscopy. In addition, the polarity can be also
controlled by applying a suitable out-of-plane magnetic field component. The
experiment and simulations show that to control the vortex polarity, the
out-of-plane field component, in this particular case, should be higher than
the in-plane nucleation field. Micromagnetic simulations in the dynamical
regime show that the magnetic vortex polarity can be changed with
short-duration magnetic field pulses, while longer pulses change the vortex
chirality.Comment: 18 pages, 11 figure
Genetic mouse models as in vivo tools for cholangiocarcinoma research
Cholangiocarcinoma (CCA) is a genetically and histologically complex disease with
a highly dismal prognosis. A deeper understanding of the underlying cellular and molecular
mechanisms of human CCA will increase our current knowledge of the disease and expedite
the eventual development of novel therapeutic strategies for this fatal cancer. This endeavor is
effectively supported by genetic mouse models, which serve as sophisticated tools to systematically
investigate CCA pathobiology and treatment response. These in vivo models feature many of the
genetic alterations found in humans, recapitulate multiple hallmarks of cholangiocarcinogenesis
(encompassing cell transformation, preneoplastic lesions, established tumors and metastatic disease)
and provide an ideal experimental setting to study the interplay between tumor cells and the
surrounding stroma. This review is intended to serve as a compendium of CCA mouse models,
including traditional transgenic models but also genetically flexible approaches based on either the
direct introduction of DNA into liver cells or transplantation of pre-malignant cells, and is meant as a
resource for CCA researchers to aid in the selection of the most appropriate in vivo model system
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