811 research outputs found
Critical features in electromagnetic anomalies detected prior to the L'Aquila earthquake
Electromagnetic (EM) emissions in a wide frequency spectrum ranging from kHz
to MHz are produced by opening cracks, which can be considered as the so-called
precursors of general fracture. We emphasize that the MHz radiation appears
earlier than the kHz in both laboratory and geophysical scale. An important
challenge in this field of research is to distinguish characteristic epochs in
the evolution of precursory EM activity and identify them with the equivalent
last stages in the earthquake (EQ) preparation process. Recently, we proposed
the following two epochs/stages model: (i) The second epoch, which includes the
finally emerged strong impulsive kHz EM emission is due to the fracture of the
high strength large asperities that are distributed along the activated fault
sustaining the system. (ii) The first epoch, which includes the initially
emerged MHz EM radiation is thought to be due to the fracture of a highly
heterogeneous system that surrounds the family of asperities. A catastrophic EQ
of magnitude Mw = 6.3 occurred on 06/04/2009 in central Italy. The majority of
the damage occurred in the city of L'Aquila. Clear kHz - MHz EM anomalies have
been detected prior to the L'Aquila EQ. Herein, we investigate the seismogenic
origin of the detected MHz anomaly. The analysis in terms of intermittent
dynamics of critical fluctuations reveals that the candidate EM precursor: (i)
can be described in analogy with a thermal continuous phase transition; (ii)
has anti-persistent behaviour. These features suggest that the emerged
candidate precursor could be triggered by microfractures in the highly
disordered system that surrounded the backbone of asperities of the activated
fault. We introduce a criterion for an underlying strong critical behavior.Comment: 8 pages, 6 figure
Sudden drop of fractal dimension of electromagnetic emissions recorded prior to significant earthquake
The variation of fractal dimension and entropy during a damage evolution
process, especially approaching critical failure, has been recently
investigated. A sudden drop of fractal dimension has been proposed as a
quantitative indicator of damage localization or a likely precursor of an
impending catastrophic failure. In this contribution, electromagnetic emissions
recorded prior to significant earthquake are analysed to investigate whether
they also present such sudden fractal dimension and entropy drops as the main
catastrophic event is approaching. The pre-earthquake electromagnetic time
series analysis results reveal a good agreement to the theoretically expected
ones indicating that the critical fracture is approaching
Geophysical Observatory in Kamchatka region for monitoring of phenomena connected with seismic activity
Regular monitoring of some geophysical parameters in association with seismicity has been carried out since last year at the Japan-Russian Complex Geophysical Observatory in the Kamchatka region. This observatory was organized in connection with the ISTC project in Russia and was motivated by the results of the FRONTIER/RIKEN and FRONTIER/NASDA research projects in Japan. The main purpose of the observations is to investigate the electromagnetic and acoustic phenomena induced by the lithosphere processes (especially by seismic activity). The seismicity of the Kamchatka area is analyzed and a description of the observatory equipment is presented. At present, the activity of the observatory includes the seismic (frequency range ∆F = 0.5 – 40 Hz) and meteorological recordings, together with seismo-acoustic (∆F = 30 – 1000 Hz) and electromagnetic observations: three-component magnetic ULF variations ( ∆F = 0.003 – 30 Hz), three-component electric potential variations ( ∆F <u><</u> 1.0 Hz), and VLF transmitter’s signal perturbations ( ∆F ~ 10 – 40 kHz)
Study of electromagnetic emissions associated with seismic activity in Kamchatka region
International audienceA review of data processing of electromagnetic emission observation collected at the Complex Geophysical Observatory Karimshino (Kamchatka peninsula) during the first 5 months (July?November, 2000) of its operation is given. The main goal of this study addresses the detection of the phenomena associated with Kamchatka seismic activity. The following observations have been conducted at CGO: variations of ULF/ELF magnetic field, geoelectric potentials (telluric currents), and VLF signals from navigation radio transmitters. The methods of data processing of these observations are discussed. The examples of the first experimental results are presented
Screening and analysis of genes expressed upon infection of broad bean with Clover yellow vein virus causing lethal necrosis
Clover yellow vein virus (ClYVV) causes lethal systemic necrosis in legumes, including broad bean (Vicia faba) and pea (Pisum sativum). To identify host genes involved in necrotic symptom expression after ClYVV infection, we screened cDNA fragments in which expression was changed in advance of necrotic symptom expression in broad bean (V. faba cv. Wase) using the differential display technique and secondarily with Northern blot analysis. Expression changes were confirmed in 20 genes, and the six that exhibited the most change were analyzed further. These six genes included a gene that encodes a putative nitrate-induced NOI protein (VfNOI), and another was homologous to an Arabidopsis gene that encodes a glycine- and proline-rich protein GPRP (VfGPRP). We recently reported that necrotic symptom development in ClYVV-infected pea is associated with expression of salicylic acid (SA)-dependent pathogenesis-related (PR) proteins and requires SA-dependent host responses. Interestingly, VfNOI and VfGPRP expression was correlated with that of the putative SA-dependent PR proteins in ClYVV-infected broad bean. However, broad bean infected with a recombinant ClYVV expressing the VfGPRP protein showed weaker symptoms and less viral multiplication than that infected with ClYVV expressing the GFP protein. These results imply that VfGPRP plays a role in defense against ClYVV rather than in necrotic symptom expression
3D Morphology, Ultrastructure and Development of Ceratomyxa puntazzi Stages: First Insights into the Mechanisms of Motility and Budding in the Myxozoa
Free, amoeboid movement of organisms within media as well as substrate-dependent cellular crawling processes of cells and organisms require an actin cytoskeleton. This system is also involved in the cytokinetic processes of all eukaryotic cells. Myxozoan parasites are known for the disease they cause in economical important fishes. Usually, their pathology is related to rapid proliferation in the host. However, the sequences of their development are still poorly understood, especially with regard to pre-sporogonic proliferation mechanisms. The present work employs light microscopy (LM), electron microscopy (SEM, TEM) and confocal laser scanning microscopy (CLSM) in combination with specific stains (Nile Red, DAPI, Phalloidin), to study the three-dimensional morphology, motility, ultrastructure and cellular composition of Ceratomyxa puntazzi, a myxozoan inhabiting the bile of the sharpsnout seabream
Current Applications of Computational Chemistry in JACS
Article discussing molecules, mechanisms, and materials and current applications of computational chemistry in the Journal of the American Chemical Society (JACS)
Aggregation and settling in aqueous polydisperse alumina nanoparticle suspensions
Nanoparticle suspensions (also called nanofluids) are often polydisperse and
tend to settle with time. Settling kinetics in these systems are known to be
complex and hence challenging to understand. In this work, polydisperse
spherical alumina (Al2O3) nanoparticles in the size range of ~10-100nm were
dispersed in water and examined for aggregation and settling behaviour near its
isoelectric point (IEP). A series of settling experiments were conducted and
the results were analysed by photography and by Small Angle X-ray Scattering
(SAXS). The settling curve obtained from standard bed height measurement
experiments indicated two different types of behaviour, both of which were also
seen in the SAXS data. But the SAXS data were remarkably able to pick out the
rapid settling regime as a result of the high temporal resolution (10s) used.
By monitoring the SAXS intensity, it was further possible to record the
particle aggregation process for the first time. Optical microscopy images were
produced on drying and dried droplets extracted from the suspension at various
times. Dried deposits showed the rapid decrease in the number of very large
particles with time which qualitatively validates the SAXS prediction, and
therefore its suitability as a tool to study unstable polydisperse colloids.
Keywords: Nanoparticles, nanofluids, polydisperse, aggregation, settling,
alumina, microscopy, SAX
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