326 research outputs found
Low attenuation frequency bands for Lamb waves immersed in viscous fluids: theoretical analysis and experimental validation.
6 pĂĄginas, 3 figuras. Proceedings of the 2013 International Congress on Ultrasonics (ICU 2013). 2-5 may 2013, SingaporeThe application of Lamb waves is a promising technique i
n ultrasonic NDE
techniques for inspection and fluid characterization due to multi
modal and dispersive
characteristics. When a plate is in contact with a viscous
fluid these waves are strongly attenuated.
However, for most of the Lamb wave modes there is a low at
tenuation frequency band that could
be used for non-destructive testing or fluid characteriz
ation. In order to explore this feature the
phase velocity and attenuation curves of Lamb modes are expe
rimentally measured in these low
attenuation frequency bands, showing good agreement with theory
.The present work was supported by the Brazilian National Council for Scientific and
Technological Development â CNPq and the Spanish Ministery of Economy and Competitivity
through the projects 560825/2010-2 and PIB2010BZ-00570, respectively.Peer reviewe
Active Detectors for Plasma Soft X-Ray Detection at PALS
This paper summarizes the work carried out for an experimental study of low-energy nuclear excitation by laser-produced plasma at the PALS Prague laser facility. We describe the adaptation and shielding of single-quantum active radiation detectors developed at IEAP CTU Prague to facilitate their operation inside the laser interaction chamber in the vicinity of the plasma target. The goal of this effort is direct real-time single-quantum detection of plasma soft X-ray radiation with energy above a few keV and subsequent identification of the decay of the excited nuclear states via low-energy gamma rays in a highly radiative environment with strong electromagnetic interference
Neoplastic Transformation of T Lymphocytes through Transgenic Expression of a Virus Host Modification Protein
Virus host evasion genes are ready-made tools for gene manipulation and therapy. In this work we have assessed the impact in vivo of the evasion gene A238L of the African Swine Fever Virus, a gene which inhibits transcription mediated by both NF-ÎșB and NFAT. The A238L gene has been selectively expressed in mouse T lymphocytes using tissue specific promoter, enhancer and locus control region sequences for CD2. The resulting two independently derived transgenic mice expressed the transgene and developed a metastasic, angiogenic and transplantable CD4+CD8+CD69â lymphoma. The CD4+CD8+CD69â cells also grew vigorously in vitro. The absence of CD69 from the tumour cells suggests that they were derived from T cells at a stage prior to positive selection. In contrast, transgenic mice similarly expressing a mutant A238L, solely inhibiting transcription mediated by NF-ÎșB, were indistinguishable from wild type mice. Expression of Rag1, Rag2, TCRÎČ-V8.2, CD25, FoxP3, Bcl3, Bcl2 l14, Myc, IL-2, NFAT1 and Itk, by purified CD4+CD8+CD69â thymocytes from A238L transgenic mice was consistent with the phenotype. Similarly evaluated expression profiles of CD4+CD8+ CD69â thymocytes from the mutant A238L transgenic mice were comparable to those of wild type mice. These features, together with the demonstration of (mono-)oligoclonality, suggest a transgene-NFAT-dependent transformation yielding a lymphoma with a phenotype reminiscent of some acute lymphoblastic lymphomas
Noncollinear magnetic ordering in small Chromium Clusters
We investigate noncollinear effects in antiferromagnetically coupled clusters
using the general, rotationally invariant form of local spin-density theory.
The coupling to the electronic degrees of freedom is treated with relativistic
non-local pseudopotentials and the ionic structure is optimized by Monte-Carlo
techniques. We find that small chromium clusters (N \le 13) strongly favor
noncollinear configurations of their local magnetic moments due to frustration.
This effect is associated with a significantly lower total magnetization of the
noncollinear ground states, ameliorating the disagreement between Stern-Gerlach
measurements and previous collinear calculations for Cr_{12} and Cr_{13}. Our
results further suggest that the trend to noncollinear configurations might be
a feature common to most antiferromagnetic clusters.Comment: 9 pages, RevTeX plus .eps/.ps figure
The BIOMEX experiment on-board the International Space Station: limits of life and detection of biomarkers after exposure to space- and to Mars-like conditions
To explore the limits of terrestrial life in space, we have to understand the effects of the space environment on unprotected biological and chemical material, and on the degradation of organic molecules or biomarkers. The exposure platform EXPOSE-R2 on the ISS offer a suitable facility for the exposure of samples of the astrobiological model lichen Circinaria gyrosa, included in the BIOMEX experiment (Biology and Mars Experiment, ESA). During 18 months (2014-2016), the lichens lived in a latent state at space and at simulated Mars-like conditions, to study Marsâ habitability and resistance to space conditions. After the return of the samples in June 2016, initial analysis showed rapid recovery of photosystem II (PSII) activity in the samples exposed exclusively to space vacuum and to Mars-like atmosphere. In contrast, the samples directly exposed to solar UV radiation showed a slow and a lower recovery, in reference to their observed original activity. This tendency was corroborated with the complementary morphological/ultrastructural and biomolecular analyses. Complementary, the biogeochemical variations have been examined with Raman spectroscopy to assess the possible degradation of cell surfaces and pigments which were in contact with terrestrial rocks, and Martian analogue regolith. Identification of the biomarker whewellite (calcium oxalate) and other organic compounds and mineral products of the biological activity of Circinaria gyrosa were detected by Raman Laser. These findings contribute to answer questions on the habitability of Mars, the likelihood of the Lithopanspermia Hypothesis, the capability to detect biomolecules exposed to an extraterrestrial environment by life-detection instruments and will be of relevance for planetary protection issues
Variability of Myrciaria dubia genotypes (Myrtaceae) in native populations of Roraima state.
Camu-camu, Myrciaria dubia (Myrtaceae) is a native species of the Amazon Rainforest that has been attracting attention worldwide and arousing great interest in the food and pharmacological industries due to the high concentrations of ascorbic acid in its fruit, which is exported to several countries. Characterizing different materials of M. dubia by means of molecular markers allows integration of agronomic and molecular information to aid in the search for more promising varieties. We examined the genetic variability of 11 populations of this species distributed along the Branco River hydrographic basin in state of Roraima in northern Brazil. The populations were defined taking into account the origin of the subsample. The 55 sub-samples present in the Embrapa Roraima Germplasm Collection were evaluated using five ISSR initiators (UBC 811, UBC 812, UBC 817, UBC 868 and UBC 880). The five primers tested generated 64 fragments, with a 98% polymorphism rate. The greatest genetic variation was expressed within the populations (66.6%), while the lowest divergence was determined among the populations (33.4%) of the collection. There was a significant correlation between genetic and geographical distances (Mantel test, r = 0.3%, P < 0.01). Analysis with the UPGMA method gave four subgroups showing that various individuals are genetically divergent and can be used in genetic breeding programs
A matter of life and death: the Middle Neolithic population from Bom Santo Cave (Lisbon, Portugal)
The study of the Bom Santo Cave (central Portugal), a Neolithic cemetery, indicated a complex social, palaeoeconomic and population scenario. With isotope, aDNA and provenience analyses of raw materials coupled with stylistic variability of material culture items and
palaeogeographical data light is shed on the territory and social organization of a population dated to 3800â3400 cal BC, i.e. the middle phase of the period. Results indicate an itinerant farming, segmentary society, where exogamic practices were the norm and patrilocality probably predominated. Its lifeway may be that of the earliest megalithic builders of the region, but further research is needed to correctly evaluate the degree of participation in such phenomenon
The expression of monocarboxylate transporters in thyroid carcinoma can be associated with the morphological features of BRAF (V600E) mutation
BRAF (V600E) mutation, usually performed by DNA techniques, is one of the most common diagnostic markers in papillary thyroid carcinoma. Few papers have demonstrated that plump cells (eosinophilic cytoplasms and papillary thyroid carcinoma nuclei) and peculiar sickle-shaped nuclei represent morphological features of BRAF (V600E) on papillary thyroid carcinomas. These features seem to be linked to glycolytic phenotype whereby monocarboxylate transporters 1-4 are hypothesized to have a dominant role as lactate transporters. We investigated the association between these morphological features and monocarboxylate transporters 1 and 4 in 48 cyto-histological samples diagnosed as "positive for malignancy-favoring papillary thyroid carcinoma". These cases were processed with liquid-based cytology and underwent BRAF (V600E) mutational analysis (pyrosequencing) on liquid-based cytology and monocarboxylate transporters immunostaining on histology. The expression of monocarboxylate transporter 1, monocarboxylate transporter 4, glucose trasporter-1 and carbonic anhidrase were scored semi-quantitatively with expression from 0 to 3+ (strong positivity). The 33 mutated and 15 wild type cases showed 100 % cyto-histological concordance. The cytological evaluation revealed plump cells and sickle nuclear shape in 100 % mutated cases. Monocarboxylate transporter 1 yielded 76 % positivity in the mutated cases especially in both the plump cells and sickle-shaped nuclei, whereas the wild types showed 13.3 % positive monocarboxylate transporter 1 (p = 0.00013). Monocarboxylate transporter 4 resulted in 100 % positivity in mutated and 40 % in wild types (p 0.05). This is the first report analyzing the association between monocarboxylate transporter expression and the morphological features of BRAF (V600E) mutated papillary thyroid carcinomas suggesting the possible involvement of lactate in the morphological features.info:eu-repo/semantics/publishedVersio
Vibrational Properties of Nanoscale Materials: From Nanoparticles to Nanocrystalline Materials
The vibrational density of states (VDOS) of nanoclusters and nanocrystalline
materials are derived from molecular-dynamics simulations using empirical
tight-binding potentials. The results show that the VDOS inside nanoclusters
can be understood as that of the corresponding bulk system compressed by the
capillary pressure. At the surface of the nanoparticles the VDOS exhibits a
strong enhancement at low energies and shows structures similar to that found
near flat crystalline surfaces. For the nanocrystalline materials an increased
VDOS is found at high and low phonon energies, in agreement with experimental
findings. The individual VDOS contributions from the grain centers, grain
boundaries, and internal surfaces show that, in the nanocrystalline materials,
the VDOS enhancements are mainly caused by the grain-boundary contributions and
that surface atoms play only a minor role. Although capillary pressures are
also present inside the grains of nanocrystalline materials, their effect on
the VDOS is different than in the cluster case which is probably due to the
inter-grain coupling of the modes via the grain-boundaries.Comment: 10 pages, 7 figures, accepted for publication in Phys. Rev.
- âŠ