Search results for " Stab"
showing 10 items of 1773 documents
Convective instability in proto-neutron stars
2000
The linear hydrodynamic stability of proto-neutron stars (PNSs) is considered taking into account dissipative processes such as neutrino transport and viscosity. We obtain the general instability criteria which differ essentially from the well-known Ledoux criterion used in previous studies. We apply the criteria to evolutive models of PNSs that, in general, can be subject to the various known regimes such as neutron fingers and convective instabilities. Our results indicate that the fingers instability arises in a more extended region of the stellar volume and lasts a longer time than expected.
Onset of convection in a vertical porous cylinder with a permeable and conducting side boundary
2015
Abstract The onset of natural convection in a vertical porous cylinder saturated by a fluid is studied. The lateral confinement of the porous cylinder is due to an external porous medium having a permeability much smaller than that of the cylinder. Thus, the vertical side boundary of the cylinder is permeable and constrained by given pressure and temperature distributions. The lower and upper plane boundaries of the cylinder are impermeable walls. The lower wall is subject to a uniform heat flux, while the upper wall has a uniform temperature. The basic motionless state displays a uniform and vertical temperature gradient oriented downward. The linear stability analysis is carried out by us…
Viscous dissipation and thermoconvective instabilities in a horizontal porous channel heated from below
2010
Accepted version of av article from the journal: International Journal of Thermal Sciences. Published version available on Science Direct: http://dx.doi.org/10.1016/j.ijthermalsci.2009.10.010 A linear stability analysis of the basic uniform flow in a horizontal porous channel with a rectangular cross section is carried out. The thermal boundary conditions at the impermeable channel walls are: uniform incoming heat flux at the bottom wall, uniform temperature at the top wall, adiabatic lateral walls. Thermoconvective instabilities are caused by the incoming heat flux at the bottom wall and by the internal viscous heating. Linear stability against transverse or longitudinal roll disturbances …
Onset of convection in a porous rectangular channel with external heat transfer to upper and lower fluid environments
2012
Published version of an article in the journal: Transport in Porous Media. Also available from the publisher at: http://dx.doi.org/10.1007/s11242-012-0018-9 The conditions for the onset of convection in a horizontal rectangular channel filled with a fluid saturated porous medium are studied. The vertical sidewalls are assumed to be impermeable and adiabatic. The horizontal upper and lower boundary walls are considered as impermeable and subject to external heat transfer, modelled through a third-kind boundary condition on the temperature field. The external fluid environments above and below the channel, kept at different temperatures, provide the heating-from-below mechanism which may lead…
ALTERAZIONI DEL RECETTORE OCULARE E COMPENSI DELLA COLONNA CERVICO-DORSALE: PARAMETRI STABILOMETRICI
2009
Scopo dello studio è stato quello di analizzare la relazione tra atteggiamento scoliotico dorsale e difetti di convergenza oculare. In 40 soggetti giovani adolescenti maschi di età compresa tra 10 e 12 anni è stata eseguita una valutazione delle curve rachidee con scoliosometro ed un esame stabilometrico mediante piattaforma Baropodometrica Elettronica Modulare “Diagnostic Support”, da cui sono stati ricavati la velocità di variazione, la deviazione media coronale (x-medio), la deviazione media sagittale (y-medio) e la superficie e lunghezza dello statokinesigramma. Inoltre, per l’analisi della funzionalità del recettore oculare, sono stati effettuati il test di convergenza oculare e il cov…
Robust l2-gain control for 2D nonlinear stochastic systems with time-varying delays and actuator saturation
2013
Abstract This paper is concerned with the problems of stability analysis and l2-gain control for a class of two-dimensional (2D) nonlinear stochastic systems with time-varying delays and actuator saturation. Firstly, a convex hull representation is used to describe the saturation behavior, and a sufficient condition for the existence of mean-square exponential stability of the considered system is derived. Then, a state feedback controller which guarantees the resulting closed-loop system to be mean-square exponentially stable with l2-gain performance is proposed, and an optimization procedure to maximize the estimation of domain of attraction is also given. All the obtained results are for…
Zn(II)-alloferon complexes - Similar sequence, different coordination modes, no antibacterial activity.
2020
Often, in the search for a highly defined scientific phenomenon, a different one becomes apparent. This was also the case of this work, in the scope of which we planned to search for metal-enhanced, novel antibacterial/ antifungal compounds. Instead, we denied the existence of such and revealed the details of the bioinorganic chemistry of Zn(II)-alloferon complexes. Zinc(II) complexes of alloferon 1 and 2, ligands with a sequential difference of one amino acid only, show a substantially different coordination pattern at physiological pH. In the case of Zn(II)-alloferon 1 species, a histamine-like binding mode is observed (N-terminal amine and imidazole of His-1) and the coordination sphere …
Bridging vs. chelating coordination modes of vinylsilanes in CuI π-Complexes: Structure and stability
2014
Two new copper(I) olefin complexes, [Cu6Cl6(MTrVS)2] (1) and [Cu2Cl2(DMVSP)2] (2), of tridentate bridging methyltrivinylsilane (MTrVS) and bidentate chelating 2-[dimethyl(vinyl)silyl]pyridine (DMVSP) have been synthesized and characterized by single-crystal X-ray structure analysis, IR and 1H NMR spectroscopy. It has been shown that using the alkenylsilanes with required electronic properties, molecular symmetry and conformational flexibility, it is possible to control the formation of optimal copper(I) halide oligomers. The obtained results, together with relevant literature data, also illustrate how the coordination mode of vinylsilanes is related to Cu–(C=C) bond strengthening and, conse…
Tratamiento psicofarmacológico del trastorno bipolar en América Latina
2011
Objective: This study assessed the treatment preferences among Latin-American psychiatrists for their bipolar disorder patients and if these preferences reflect the current guidelines. Methods: We designed a survey comprised of fourteen questions. All the questions were aimed at the treatment of bipolar I patients only. We distributed the survey by hand or e-mail to psychiatrists in eight different countries: Argentina, Brasil, Colombia, Costa Rica, Ecuador, México, Perú and Venezuela. Between May 2008 and June 2009, we were able to gather 1143 surveys. Results: As the initial choice of treatment for a bipolar patient who debuts with mania, 61.3% choose a combination of an atypical antipsyc…
The Role of Covalent Functionalization in the Thermal Stability and Decomposition of Hybrid Layered Hydroxides
2020
The room temperature synthesis of two Co-based hybrid layered hydroxides containing the same organic ligand (suberate [Sub]), one connected through purely electrostatic interactions (CoAl layered double hydroxide [LDH]), and the other covalently functionalized (α-CoII simonkolleite phase) has been carried out. The magnetic properties exhibit an acute difference in the magnetization temperatures (from ≈10 K for the CoAl-LDH to ≈55 K for the α-CoII). Moreover, the role of the covalent functionalization in the thermal stability and the decomposition has been investigated by a forefront characterization tool consisting of thermogravimetric analysis coupled with gas chromatography and mass spect…