2,304 research outputs found
A stereotaxic method for small animals using experimentally determined reference profiles
In bats conventional stereotaxic methods do not yield sufficient positional accuracy to allow reliable recordings and tracer injections in subnuclei of the auditory system. In a newly developed stereotaxic system experimentally measured patterns of skull profile lines are used to define the animal's brain position with an accuracy of ±100 μm. By combining the neurophysiological stereotaxic procedure with a standardization of the neuroanatomical processing of the brains, the location of recordings, stimulations or injections can be readily transformed into brain atlas coordinates. This facilitates the compilation and comparison of data within and among animals. The system is not restricted to use in bats and can be readily adapted to other experimental animals
Vortex ratchet reversal: The role of interstitial vortices
Triangular arrays of Ni nanotriangles embedded in superconducting Nb films
exhibit unexpected dynamical vortex effects. Collective pinning with a vortex
lattice configuration different from the expected fundamental triangular
"Abrikosov state" is found. The vortex motion which prevails against the
triangular periodic potential is produced by channelling effects between
triangles. Interstitial vortices coexisting with pinned vortices in this
asymmetric potential, lead to ratchet reversal, i.e. a DC output voltage which
changes sign with the amplitude of an applied alternating drive current. In
this landscape, ratchet reversal is always observed at all magnetic fields (all
numbers of vortices) and at different temperatures. The ratchet reversal is
unambiguously connected to the presence of two locations for the vortices:
interstitial and above the artificial pinning sites.Comment: 21 pages, 4 figures, 1 Tabl
Growth-Induced In-Plane Uniaxial Anisotropy in VO/Ni Films
We report on a strain-induced and temperature dependent uniaxial anisotropy
in VO/Ni hybrid thin films, manifested through the interfacial
strain and sample microstructure, and its consequences on the angular dependent
magnetization reversal. X-ray diffraction and reciprocal space maps identify
the in-plane crystalline axes of the VO; atomic force and scanning
electron microscopy reveal oriented rips in the film microstructure.
Quasi-static magnetometry and dynamic ferromagnetic resonance measurements
identify a uniaxial magnetic easy axis along the rips. Comparison with films
grown on sapphire without rips shows a combined contribution from strain and
microstructure in the VO/Ni films. Magnetization reversal
characteristics captured by angular-dependent first order reversal curve
measurements indicate a strong domain wall pinning along the direction
orthogonal to the rips, inducing an angular-dependent change in the reversal
mechanism. The resultant anisotropy is tunable with temperature and is most
pronounced at room temperature, which is beneficial for potential device
applications
Efeito da Experiência Atlética e de Diferentes Grupos Musculares na Percepção de Força
O objetivo do presente estudo foi verificar se diferentes níveis de sensibilidade e acurácia na percepção de força podem estar relacionados à experiência atlética e verificar se a acurácia depende do tipo de grupo muscular usado durante diferentes tarefas psicofísicas de percepção de força. Os sujeitos atletas (GA) e sedentários (GS) produziram
e estimaram magnitudes de força através de: 1. pressionar manualmente um dinamômetro (DM); 2. erguer pesos
na posição supino (SU) e 3. empurrar pesos na posição sentada (LP). Os resultados mostraram que GA e GS têm
estilos diferentes de percepção de força. GS percebeu magnitudes de pesos mais próximas da escala real usada na
tarefa LP. GA mostrou uma super constância em ambas as tarefas SU e LP. Sub constância foi comum para ambos os
grupos na tarefa DM. O GA tendeu a superestimar as magnitudes terminais dos pesos levantados nas tarefas SU e LP e demonstrou pouca sensibilidade às mudanças de baixa intensidade
On the use of Purcell factors for plasmon antennas
The Purcell factor is the standard figure of merit for spontaneous emission
enhancement in microcavities, that has also been proposed to describe emission
enhancements for plasmonic resonances. A comparison is made of quality factor,
mode volume and Purcell factor for single and coupled plasmon spheres to exact
calculations of emission rates. The paper explains why the Purcell factor is
not appropriate for plasmon antennas.Comment: 3 pages, 2 figure
Bioinformatic approaches for the genetic and phenotypic characterization of a Saccharomyces cerevisiae wine yeast collection
The objective of the present study was to compare genetic and phenotypic variation of 103 Saccharomyces cerevisiae strains isolated from winemaking environments. We used bioinformatics approaches to identify genetically similary strains with specific phenotypes and to estimate a strain's biotechnological potential. 
A S. cerevisiae collection, comprising 440 strains that were obtained from winemaking environments in Portugal has been constituted during the last years. All strains were genetically characterized by a set of eleven highly polymorphic microsatellites and showed unique allelic combinations. Using neural networks, a subset of 103 genetically most diverse strains was chosen for phenotypic analysis, that included growth in synthetic must media at various temperatures, utilization of carbon sources (glucose, ribose, arabinose, xylose, saccharose, galactose, rafinose, maltose, glycerol, potassium acetate and pyruvic acid), growth in ethanol containing media, evaluation of osmotic and oxidative stress resistance, H2S production and utilization of different nitrogen sources. Using supervised data mining approaches we have found that genotype represented with presence/absence of eleven microsatellites relates well with geographical location (performance evaluation using leave-out-out technique resulted in high performance scores; e.g., area under ROC curve was above 0.8 for a number of standard machine learning approaches tested). To find relations between phenotypes and genotypes, we used a two-step approach which first hierarchically clusters the strains according to their phenotype, and then tests if the resulting sub-clusters are identifiable using strain’s genetic data. Several groups of strains with similar phenotype profiles and common features in genotype were identified this way, and they are subject to further investigations. 

Financially supported by the programs POCI 2010 (FEDER/FCT, POCTI/AGR/56102/2004) and AGRO (ENOSAFE, Nº 762).

The non-birefringent limit of all linear, skewonless media and its unique light-cone structure
Based on a recent work by Schuller et al., a geometric representation of all
skewonless, non-birefringent, linear media is obtained. The derived
constitutive law is based on a "core", encoding the optical metric up to a
constant. All further corrections are provided by two (anti-)selfdual
bivectors, and an "axion". The bivectors are found to vanish if the optical
metric has signature (3,1) - that is, if the Fresnel equation is hyperbolic. We
propose applications of this result in the context of transformation optics and
premetric electrodynamics.Comment: 12 pages, REVTeX; v2: typos; v3: relevant changes in text,
reorganization of manuscript; v4: new section added, final version, to appear
in Annalen der Physi
Expression of the α7 nicotinic acetylcholine receptor in human lung cells
BACKGROUND: We and others have shown that one of the mechanisms of growth regulation of small cell lung cancer cell lines and cultured pulmonary neuroendocrine cells is by the binding of agonists to the α7 neuronal nicotinic acetylcholine receptor. In addition, we have shown that the nicotine-derived carcinogenic nitrosamine, 4(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), is a high affinity agonist for the α7 nicotinic acetylcholine receptor. In the present study, our goal was to determine the extent of α7 mRNA and protein expression in the human lung. METHODS: Experiments were done using reverse transcription polymerase chain reaction (RT-PCR), a nuclease protection assay and western blotting using membrane proteins. RESULTS: We detected mRNA for the neuronal nicotinic acetylcholine receptor α7 receptor in seven small cell lung cancer (SCLC) cell lines, in two pulmonary adenocarcinoma cell lines, in cultured normal human small airway epithelial cells (SAEC), one carcinoid cell line, three squamous cell lines and tissue samples from nine patients with various types of lung cancer. A nuclease protection assay showed prominent levels of α7 in the NCI-H82 SCLC cell line while α7 was not detected in SAEC, suggesting that α7 mRNA levels may be higher in SCLC compared to normal cells. Using a specific antibody to the α7 nicotinic receptor, protein expression of α7 was determined. All SCLC cell lines except NCI-H187 expressed protein for the α7 receptor. In the non-SCLC cells and normal cells that express the α7 nAChR mRNA, only in SAEC, A549 and NCI-H226 was expression of the α7 nicotinic receptor protein shown. When NCI-H69 SCLC cell line was exposed to 100 pm NNK, protein expression of the α7 receptor was increased at 60 and 150 min. CONCLUSION: Expression of mRNA for the neuronal nicotinic acetylcholine receptor α7 seems to be ubiquitously expressed in all human lung cancer cell lines tested (except for NCI-H441) as well as normal lung cells. The α7 nicotinic receptor protein is expressed in fewer cell lines, and the tobacco carcinogen NNK increases α7 nicotinic receptor protein levels
Pressure drop non-linearities in material extrusion additive manufacturing: a novel approach for pressure monitoring and numerical modeling
Fused Filament Fabrication is an additive manufacturing technique in which
molten thermoplastic polymers are extruded through a nozzle. Therefore, the
interplay between the viscoelastic nature of the polymer melt, temperature,
printing conditions and nozzle shape may lead to inconsistent extrusion. To
improve the extrusion control and optimize the print-head performance, a better
understanding of the flow process of the polymer melt both in the nozzle and
the liquefier is needed. However, several challenges need to be overcome due to
the complexity of gathering experimental data on the melt pressure in the
nozzle and the lack of numerical models able to capture the full rheology of
the molten polymer. This research introduces an innovative approach for
monitoring the pressure within a material extrusion 3D printer's nozzle. This
method involves utilizing a pin in direct contact with the molten material,
which then transmits the applied force from the material to an externally
mounted load cell. The setup provides reliable, repeatable pressure data in
steady-state conditions for two nozzle geometries and at different extrusion
flows and temperatures. Moreover, the Giesekus model enabled capturing the
viscoelastic rheometric features of the melt, and the numerical predictions
have been compared with the experimental data. Results show that the numerical
model accurately describes the flow conditions in the nozzle and allows the
estimation of the behaviour of the melt in the liquefier zone, the area of the
print-head where the filament is molten. It could be concluded that the
backflow, which is the backward flow of the molten polymer in the gap between
the filament and the liquefier towards the cold end, caused significant
non-linearities in the total pressure drop measured in the feeders, which were
related to normal forces induced by shear in that region
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