197 research outputs found
L'erbario del Prof. Manlio Chiappini (1924-1998) in Herbarium CAG
No full textThe herbarium of Chiappini, held in Herbarium CAG of Cagliari University, is presented. Prof. Manlio Chiappini, who dead the 4th of january 1998, teached Botany at the Athenaeum of Cagliari from 1965 to 1987 and from 1965 to 1986 he was director of Botanical Institute and Botanical gardens of Cagliari University. From a research carried out in Herbarium CAG is shown that Chiappini’s herbarium is compound of 1262 exsiccata, referred to 630 specific and subspecific entities (about the 30% of Sardinian flora), of which 45 referred to endemic species (about the 20% of Sardinian flora) and that the Museum Herbarium CAG itself is depositary of a number of 4 species pointed out, by the Author himself, for the first time to Sardinia
Three-Body Dynamics and Self-Powering of an Electrodynamic Tether in a Plasmasphere
No full textThe dynamics of an electrodynamic tether in a three-body gravitational environment are investigated. In the classical two-body scenario the extraction of power is at the expense of orbital kinetic energy. As a result of power extraction, an electrodynamic tether satellite system loses altitude and deorbits. This concept has been proposed and well investigated in the past, for example for orbital debris mitigation and spent stages reentry. On the other hand, in the three-body scenario an electrodynamic tether can be placed in an equilibrium position fixed with respect to the two primary bodies without deorbiting, and at the same time generate power for onboard use. The appearance of new equilibrium positions in the perturbed three-body problem allow this to happen as the electrical power is extracted at the expenses of the plasma corotating with the primary body. Fundamental differences between the classical twobody dynamics and the new phenomena appearing in the circular restricted three-body problem perturbed by the electrodynamic force of the electrodynamic tether are shown in the paper. An interesting application of an electrodynamic tether placed in the Jupiter plasma torus is then considered, in which the electrodynamic tether generates useful electrical power of about 1 kW with a 20-km-long electrodynamic tether from the environmental plasma without losing orbital energy
Properties of Thermus aquaticus b-NADH oxidase immobilised on various supports
No full textbeta-NADH oxidase purified from Thermus aquaticus was covalently immobilised on various solid supports. The preparations obtained were compared with the soluble enzyme for activity and kinetic properties. Activated glutaryl-PVA was found to be the best support. The immobilised enzyme was less stable at high temperatures than the soluble enzyme. No differences could be detected in the presence of organic solvents.beta-NADH oxidase purified from Thermus aquaticus was covalently immobilised on various solid supports. The preparations obtained were compared with the soluble enzyme for activity and kinetic properties. Activated glutaryl-PVA was found to be the best support. The immobilised enzyme was less stable at high temperatures than the soluble enzyme. No differences could be detected in the presence of organic solvents
IFN-alpha2b increases interleukin-10 expression in primary activated human CD8+ T cells
No full textInterleukin-10 (IL-10) is a multifunctional cytokine with diverse effects on most hematopoietic cell types. It appears the principal function of IL-10 is to limit and ultimately terminate inflammatory response. We demonstrate here that interferon-alpha2b (IFN-alpha) increases the expression of IL-10 in activated primary CD8(+) T cells. Optimal induction of mRNA expression and protein synthesis was observed when IFN-alpha was added to cells activated by the combination of anti-CD3 monoclonal antibody (mAb) and IL-2. Maximal stimulation of IL-10 protein production was observed after prolonged incubation periods (48-72 h). No effects were observed on the production of IL-4, whereas IFN-gamma was produced with a faster kinetics than an untreated control. Our data indicate that IFN-alpha promotes the development of a CD8(+) T cell population with enhanced anti-inflammatory activity, which may play a critical role in the regulation of a proper immune response
Numerical formulation of the jet damping torque for space vehicles with thrust vector control
No full textExploration of the Galilean Moons using electrodynamic tethers for propellantless maneuvers and self-powering
No full textAbstract. Recent studies have demonstrated the benefits of using electrodynamic tethers (EDT) for the exploration of the inner region of the Jovian system. Intense planetary magnetic field and reasonable environmental plasma density make the electrodynamic interaction of the
conductive tether with the plasmasphere strong. The interaction is responsible for a Lorentz
force that can be conveniently used for propellantless maneuvers and extraction of electrical
power for on board use. Jupiter and the four Galilean Moons represent an exceptional gravitational
environment for the study of the orbital dynamics of an EDT. The dynamics of such a system was analyzed using a 3-body model, consisting of the planet plus one of its moons
(Io in this work) and the EDT itself. New and interesting features appear, like for example the
possibility to place the tether in equilibrium with respect to a frame co-rotating with the moon at points that do not coincide with the classical Lagrangian points for non-null electrodynamic forces
Engagement of CD28 modulates CXC chemokine receptor 4 surface expression in both resting and CD3-stimulated CD4+ T cells
No full textOptimal CD4+ T cell activation requires the cooperation of multiple signaling
pathways coupled to the TCR-CD3 complex and to the CD28 costimulatory molecule.
In this study, we have investigated the expression of surface CXC chemokine
receptor 4 (CXCR4) in enriched populations of CD4+ T PBL, stimulated with
anti-CD3 and anti-CD28 mAbs, immobilized on plastic. Anti-CD3 alone induced a
progressive down-regulation of surface CXCR4, accompanied by a significant
decline in the entry of the HXB2 T cell line-tropic (X4-tropic) HIV-1 clone in
CD4+ T cells. Of note, this effect was strictly dependent on the presence in
culture of CD14+ monocytes. On the other hand, anti-CD28 alone induced a small
but reproducible increase in the expression of surface CXCR4 as well as in the
entry of HXB2 HIV-1 clone in resting CD4+ T cells. When the two mAbs were used in
combination, anti-CD28 potently synergized with anti-CD3 in inducing the
expression of CD69 activation marker and stimulating the proliferation of CD4+ T
cells. On the other hand, anti-CD28 counteracted the CXCR4 down-modulation
induced by anti-CD3. The latter effect was particularly evident when anti-CD28
was associated to suboptimal concentrations of anti-CD3. Because CXCR4 is the
major coreceptor for the highly cytopathic X4-tropic HIV-1 strains, which
preferentially replicate in proliferating CD4+ T cells, the ability of anti-CD28
to up-regulate the surface expression of CXCR4 in both resting and activated CD4+
T cells provides one relevant mechanism for the progression of HIV-1 disease
IFN-α2b reduces IL-2 production and IL-2 receptor function in primary CD4+ T cells
No full textInitially described as an antiviral cytokine, IFN-alpha has been subsequently shown to affect several cellular functions, including cellular differentiation and proliferation. For these reasons, IFN-alpha is currently used in clinical practice for the treatment of viral infections and malignancies. In this manuscript, we show two novel mechanisms concomitantly responsible for the antiproliferative effect of IFN-alpha. First, long-term treatment with IFN-alpha of primary CD4+ T cells reduced surface expression of CD3 and CD28. These events resulted in decreased phosphorylation of the mitogen-activated extracellular signal-regulated activating kinase and its substrate extracellular signal-regulated kinase, leading to diminished production of IL-2. Second, IFN-alpha treatment of primary CD4+ T cells reduced proliferative response to stimulation in the presence of exogenous IL-2 by markedly decreasing mRNA synthesis and surface expression of CD25 (alpha-chain), a critical component of the IL-2R complex. These results may be relevant for the antitumor effects of IFN-alpha and may help us to better understand its detrimental role in the inhibition of proliferation of the bulk of CD4+ T cells (uninfected cells) in HIV-infected persons, who are known to overproduce IFN-alpha
Numerical formulation of the equations describing the rigid-body dynamics of a variable mass rocket with internal flow
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