1,824 research outputs found
Regimes of self-organized criticality in the atmospheric convection
Large scale organization in ensembles of events of atmospheric convection can
be generated by the combined effect of forcing and of the interaction between
the raising plumes and the environment. Here the "large scale" refers to the
space extension that is larger or comparable with the basic resolved cell of a
numerical weather prediction system. Under the action of external forcing like
heating individual events of convection respond to the slow accumulation of
vapor by a threshold-type dynamics. This is due to the a time-scale separation,
between the slow drive and the fast convective response, expressed as the
"quasi-equilibrium". When there is interaction between the convection plumes,
the effect is a correlated response. We show that the correlated response have
many of the characteristics of the self-organized criticality (SOC). It is
suggested that from the SOC perspective, a description of the specific dynamics
induced by "quasi-equilibrium" can be provided by models of "punctuated
equilibrium". Indeed the Bak-Sneppen model is able to reproduce (within
reasonable approximation) two of the statistical results that have been
obtained in observations on the organized convection.
We also give detailed derivation of the equations connecting the
probabilities of the states in the update sequence of the Bak-Sneppen model
with random neighbors. This analytical framework allows the derivation of
scaling laws for the size of avalanches, a result that gives support to the SOC
interpretation of the observational data.Comment: Text prepared for the Report of COST ES0905 collaboration (2014).
Latex 45 page
Perforated small intestine in a patient with T-cell lymphoma; a rare cause of peritonitis
The nontraumatic perforations of the small intestine are pathological entities with particular aspects in respect to diagnosis and treatment. These peculiarities derive from the nonspecific clinical expression of the peritonitis syndrome, and from the multitude of causes that might be the primary sources of the perforation: foreign bodies, inflammatory diseases, tumors, infectious diseases, etc. Accordingly, in most cases intestinal perforation is discovered only by laparotomy and the definitive diagnosis is available only after histopathologic examination. Small bowel malignancies are rare; among them, lymphomas rank third in frequency, being mostly B-cell non Hodgkin lymphomas. Only 10% of non-Hodgkin lymphomas are with T-cell.
We report the case of a 57 years’ old woman with intestinal T-cell lymphoma, whose first clinical symptomatology was related to a complication represented by perforation of the small intestine. Laparotomy performed in emergency identified an ulcerative lesion with perforation in the jejunum, which required segmental enterectomy with anastomosis. The nonspecific clinical manifestations of intestinal lymphomas make from diagnosis a difficult procedure. Due to the fact that surgery does not have a definite place in the treatment of the small intestinal lymphomas (for cases complicated with perforation), and beyond the morbidity associated with the surgery performed in emergency conditions, prognosis of these patients is finally given by the possibility to control the systemic disease through adjuvant therapy
Appendicular mass – a rare form of tuberculosis
Tuberculosis is in the top 10 causes of death worldwide, being one of the most deadly infectious diseases. It is estimated that one of three people from the entire earth population has a latent infection with M tuberculosis. This aerobic bacterium possesses the ability to persist in host tissues for years and to begin replication once immunity declines.
The lungs are most frequent site of infection as the Mycobacterium tuberculosis is carried by aerosol droplets and is commonly transmitted by respiratory route. The second way of transmission is by contaminated food.
Intestinal contamination coexists with pulmonary tuberculosis and only 10% represent primitive enteric diseases. The ileocecal region is involved most frequently. Even in this context isolated appendicular involvement remains rare.
We report the case of appendicular tuberculosis in a 17-year-old woman with no evidence of other location of disease elsewhere in the body
RFID AND INFORMATION SYSTEMS IN COMMERCE
The paper analysis the possibilities of using, a relative new technology, RFID, in commerce. The main features of this technology, the components of the system, the way the system functions and the stages of the implementing process are also presented. Another part of the paper is devoted to the identification of the advantages of RFID technology and of the hurdels faced by companies in adopting it. The interest for this technology, used as solution for the management of information systems, is in a continuous increase, despite all the problems related to the high cost of the implementation and the wrong legislation, which stops the spread of this technology on a larger scale. The technology is now presented in a relatively small number of companies, but, certainly, it will be adopted, by more and more information systems in the future and it will extend in other activities too.information, radio waves, labels, antenna, reader
Wideband laser locking to an atomic reference with modulation transfer spectroscopy
We demonstrate that conventional modulated spectroscopy apparatus, used for
laser frequency stabilization in many atomic physics laboratories, can be
enhanced to provide a wideband lock delivering deep suppression of frequency
noise across the acoustic range. Using an acousto-optic modulator driven with
an agile oscillator, we show that wideband frequency modulation of the pump
laser in modulation transfer spectroscopy produces the unique single lock-point
spectrum previously demonstrated with electro-optic phase modulation. We
achieve a laser lock with 100 kHz feedback bandwidth, limited by our laser
control electronics. This bandwidth is sufficient to reduce frequency noise by
30 dB across the acoustic range and narrows the imputed linewidth by a factor
of five.Comment: 11 pages, 3 figures, 1 table; v2: additional laser frequency noise
data demonstrating greater linewidth reduction, many textual improvements,
accepted for publication in Optics Expes
Trajectory structures and transport
The special problem of transport in 2-dimensional divergence-free stochastic
velocity fields is studied by developing a statistical approach, the nested
subensemble method. The nonlinear process of trapping determined by such fields
generates trajectory structures whose statistical characteristics are
determined. These structures strongly influence the transport.Comment: Latex file 19 pages, includes 12 EPS figures. Extended version of the
invited talk at the ITCPP, Santorini, 200
Noble internal transport barriers and radial subdiffusion of toroidal magnetic lines
Single trajectories of magnetic line motion indicate the persistence of a
central protected plasma core, surrounded by a chaotic shell enclosed in a
double-sided transport barrier : the latter is identified as being composed of
two Cantori located on two successive "most-noble" numbers values of the
perturbed safety factor, and forming an internal transport barrier (ITB).
Magnetic lines which succeed to escape across this barrier begin to wander in a
wide chaotic sea extending up to a very robust barrier (as long as L<1) which
is identified mathematically as a robust KAM surface at the plasma edge. In
this case the motion is shown to be intermittent, with long stages of
pseudo-trapping in the chaotic shell, or of sticking around island remnants, as
expected for a continuous time random walk.Comment: TEX file, 84 pages including 32 color figures. Higher quality figures
can be seen on the PDF file at
http://membres.lycos.fr/fusionbfr/JHM/Tokamap/JSP.pd
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