211 research outputs found
A review of residual stress analysis using thermoelastic techniques
Thermoelastic Stress Analysis (TSA) is a full-field technique for experimental stress analysis
that is based on infra-red thermography. The technique has proved to be extremely effective for
studying elastic stress fields and is now well established. It is based on the measurement of the
temperature change that occurs as a result of a stress change. As residual stress is essentially a
mean stress it is accepted that the linear form of the TSA relationship cannot be used to
evaluate residual stresses. However, there are situations where this linear relationship is not
valid or departures in material properties due to manufacturing procedures have enabled
evaluations of residual stresses. The purpose of this paper is to review the current status of
using a TSA based approach for the evaluation of residual stresses and to provide some
examples of where promising results have been obtained
Independent Component Analysis of Spatiotemporal Chaos
Two types of spatiotemporal chaos exhibited by ensembles of coupled nonlinear
oscillators are analyzed using independent component analysis (ICA). For
diffusively coupled complex Ginzburg-Landau oscillators that exhibit smooth
amplitude patterns, ICA extracts localized one-humped basis vectors that
reflect the characteristic hole structures of the system, and for nonlocally
coupled complex Ginzburg-Landau oscillators with fractal amplitude patterns,
ICA extracts localized basis vectors with characteristic gap structures.
Statistics of the decomposed signals also provide insight into the complex
dynamics of the spatiotemporal chaos.Comment: 5 pages, 6 figures, JPSJ Vol 74, No.
Convective and absolute Eckhaus instability leading to modulated waves in a finite box
We report experimental study of the secondary modulational instability of a
one-dimensional non-linear traveling wave in a long bounded channel. Two
qualitatively different instability regimes involving fronts of spatio-temporal
defects are linked to the convective and absolute nature of the instability.
Both transitions appear to be subcritical. The spatio-temporal defects control
the global mode structure.Comment: 5 pages, 7 figures (ReVTeX 4 and amsmath.sty), final versio
Substitutions of fluorine atoms and phenoxy groups in the synthesis of quinoxaline 1,4-di-N-oxide derivatives.
The unexpected substitution of fluorine atoms and phenoxy groups attached to
quinoxaline or benzofuroxan rings is described. The synthesis of 2-benzyl- and 2-phenoxy-
3-methylquinoxaline 1,4-di-N-oxide derivatives was based on the classical Beirut reaction.
The tendency of fluorine atoms linked to quinoxaline or benzofuroxan rings to be replaced
by a methoxy group when dissolved in an ammonia saturated solution of methanol was
clearly demonstrated. In addition, 2-phenoxyquinoxaline 1,4-di-N-oxide derivatives
became 2-aminoquinoxaline 1,4-di-N-oxide derivatives in the presence of gaseous
ammonia
Defect Chaos of Oscillating Hexagons in Rotating Convection
Using coupled Ginzburg-Landau equations, the dynamics of hexagonal patterns
with broken chiral symmetry are investigated, as they appear in rotating
non-Boussinesq or surface-tension-driven convection. We find that close to the
secondary Hopf bifurcation to oscillating hexagons the dynamics are well
described by a single complex Ginzburg-Landau equation (CGLE) coupled to the
phases of the hexagonal pattern. At the bandcenter these equations reduce to
the usual CGLE and the system exhibits defect chaos. Away from the bandcenter a
transition to a frozen vortex state is found.Comment: 4 pages, 6 figures. Fig. 3a with lower resolution no
Quinoxaline 1,4-di-N-oxide and the Potential for Treating Tuberculosis
New drugs active against drug-resistant tuberculosis are urgently needed to extend the range of TB treatment options to cover drug resistant infections. Quinoxaline derivatives show very interesting biological properties (antibacterial, antiviral, anticancer, antifungal, antihelmintic, insecticidal) and evaluation of their medicinal chemistry is still in progress. In this review we report the properties and the recent developments of quinoxaline 1,4-di-N-oxide derivatives as potential anti-tuberculosis agents. Specific agents are reviewed that have excellent antitubercular drug properties, are active on drug resistant strains and non-replicating mycobacteria. The properties of select analogs that have in vivo activity in the low dose aerosol infection model in mice will be reviewed
Synthesis and biological evaluation of new quinoxaline derivatives as antioxidant and anti-inflammatory agents
We report the synthesis, anti-inflammatory and antioxidant activities of novel quinoxaline and quinoxaline 1,4-di-N-oxide derivatives. Microwave assisted methods have been used in order to optimize reaction times and to improve the yields. The tested compounds presented important scavenging activities and promising in vitro inhibition of soybean lipoxygenase. Two of the best lipoxygenase inhibitors (compounds 7b and 8f) were evaluated as in vivo anti-inflammatory agents using the carrageenin-induced edema model. One of them (compound 7b) showed important in vivo anti-inflammatory effect (41%) similar to that of indomethacin (47%) used as the reference drug
Larval Development in Tropical Gar (Atractosteus tropicus) Is Dependent on the Embryonic Thermal Regime: Ecological Implications under a Climate Change Context
In ectotherm species, environmental temperature plays a key role in development, growth,
and survival. Thus, determining how temperature affects fish populations is of utmost importance to
accurately predict the risk of climate change over fisheries and aquaculture, critical to warrant nutrition
and food security in the coming years. Here, the potential effects of abnormal thermal regimes
(24, 28 and 32 C; TR24, TR28, and TR32, respectively) exclusively applied during embryogenesis
in tropical gar (Atractosteus tropicus) has been explored to decipher the potential consequences on
hatching and growth from fertilization to 16 days post-fertilization (dpf), while effects on skeletal
development and body morphology were explored at fertilization and 16 dpf. Egg incubation at
higher temperatures induced an early hatching and mouth opening. A higher hatching rate was
obtained in eggs incubated at 28 C when compared to those at 24 C. No differences were found in
fish survival at 16 dpf, with values ranging from 84.89 to 88.86%, but increased wet body weight and
standard length were found in larvae from TR24 and TR32 groups. Thermal regime during embryogenesis
also altered the rate at which the skeletal development occurs. Larvae from the TR32 group
showed an advanced skeletal development, with a higher development of cartilaginous structures at
hatching but reduced at 16 dpf when compared with the TR24 and TR28 groups. Furthermore, this
advanced skeletal development seemed to determine the fish body morphology. Based on biometric
measures, a principal component analysis showed how along development, larvae from each thermal
regime were clustered together, but with each population remaining clearly separated from each other.
The current study shows how changes in temperature may induce craniofacial and morphological
alterations in fish during early stages and contribute to understanding the possible effects of global
warming in early development of fish and its ecological implications.Versión del edito
MHD in von Kármán swirling flows, development and first run of the sodium experiment
URL: http://www-spht.cea.fr/articles/s01/004 MHD dans les écoulements de von Kármán | Collaboration VKSNATO Science Series II 26, 35-50 (2001). NATO Advanced Research Workshop, Dynamo and Dynamics, A Mathematical ChallengeWe describe the motivations, development and first run of the Von Kármán Sodium (VKS) experiment built to study high Reynolds number magnetohydrodynamics and applications to the dynamo effect. The flow is optimized using water experiments at scale 1/2 and kinematic dynamo simulations. In VKS run1, induction measurements are made in the presence of an externally applied field. Results are reported concerning the geometry of the induced field and its fluctuations in time
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