Non-equilibrium relativistic M.H.D. with finite electrical conductivity

A system of balance laws for relativistic m.h.d, with finite eIectrical conductivity, heat flux and viscosity is proposed, starting from the properties of the systems of conservation laws compatible with a supplementary balance law (entropy balance). Adopting a two-fluid scheme the plasma is treated as a mixture of a neutral fluid and a charged fluid. Following the approach ofextended thermodynamics heat flux, viscous stress and electric current density are considered as new field variables contributing to non equilibrium entropy density and flux.     

Extended thermodynamics of a relativistic plasma with finite electric conductivity

A system of equations for relativistic m.h.d, with finite electric conductivity and no heat flux is proposed, starting from the properties of the systems of conservation laws compatible with a supplementary balance law (entropy balance) with convex density (symmetric-hyperbolic systems). The electric current density is treated as a new field variable which contributes to non equilibrium entropy density (extended thermodynamics). The result is a theory in which only one new constitutive function, representing entropy increment respect to equilibrium, is necessary to characterize the properties of the medium related to electric conductivity.G.N.F.M. of the C.N.R.     

Space charge effects and electronic bistability

Summary The excitation of metastable states in an atomic beam apparatus by means of electron collision is a widespread technique. We have observed a large bistable behaviour in our apparatus designed to provide an intense and collimated beam of metastable helium by excitation with orthogonally impinging electrons. This bistable behaviour largely affects the efficiency of the apparatus and is therefore worth of being carefully investigated. The apparatus has an electrode configuration equivalent to that of a tetrode valve with large intergrid distances. The bistability consists in a hysteresis cycle in the curve of the anode currentvs. grid voltage. Experimental measurements, supported by a simple theoretical model and by numerical simulation, stress out the crucial role played by space charge effects for the onset of bistability. A comparison with previous observation of this phenomenon is given. Spontaneous current oscillations with various shapes have been recorded in one of the two curves of the hysteresis cycle.     

IR-FIR Transferred lamb-dip spectroscopy in optically pumped molecular lasers

Pump saturation effects are reported for CH₃ and CH₃F optically pumped molecular lasers. The Lamb-dip of the pumping transition is observed directly in the optoacoustic absorption signal and as a transferred Lamb-dip in the emission of various FIR laser lines (CH₃F 496 μm, CH₃OH 119, 70.5 and 96.5 μm) . The offset of the absorbing transitions and their Stark effect are directly investigated. Results are also reported for the unassigned CH₃OH 164 μm line.     

Optogalvanic nonlinear hanle effect by a single frequency laser: A quantitative analysis

The optogalvanic technique combined with the excitation by means of a single-frequency dye laser has been used to investigate the nonlinear Hanle effect on a variety of atomic transitions involving various quantum numbers and selection rules. A rate equation model has been successfully applied to provide a quantitative analysis of the observed signals. Saturation and pressure broadening parameters are reported for Ne transitions at 607.4 and 603.0 nm and Ca transitions at 610.2 and 585.7 nmWork partially supported by INFN and Italian Ministery of Education     

Surface modification of activated polymeric matrices by dendritic attachments

Aware of the growing interest in materials that exhibit specific physiochemical properties and potential applications, we focused our work on modifying commercial agarose with polyfunctional dendrons capable of molecular recognition through hydrogen bonding. 2,6‐Di(acylamino)pyridine moieties within the internal superstructure of dendritic macromolecules have been reported to be capable of forming H‐bonded complexes with imide groups, such as barbituric acid and its derivatives. We report the synthesis of new dendrons possessing multiple 2,6‐di(acylamino)pyridinyl sites, each capable of molecular recognition, and the development of new polymeric supports of an activated agarose matrix by surface modification. From comparative studies of the beads modified by different dendrons, we found improved results in those dendritic supports possessing 2,6‐di(acylamino)pyridinyl moieties, except when their juxtaposition between the groups promoted inner H bonds. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2779–2786, 2000     

Probing High-Scale and Split Supersymmetry with Higgs mass measurements

We study the range of Higgs masses predicted by High-Scale Supersymmetry and by Split Supersymmetry, using the matching condition for the Higgs quartic coupling determined by the minimal field content. In the case of Split Supersymmetry, we compute for the first time the complete next-to-leading order corrections, including two-loop renormalization group equations and one loop threshold effects. These corrections reduce the predicted Higgs mass by a few GeV. We investigate the impact of the recent LHC Higgs searches on the scale of supersymmetry breaking. In particular, we show that an upper bound of 127 GeV on the Higgs mass implies an upper bound on the scale of Split Supersymmetry of about ¹⁰⁸ GeV, while no firm conclusion can yet be drawn for High-Scale Supersymmetry.     

Nonlinear Hanle effect in the active discharge of an argon laser

 We present experimental evidence of the NonLinear Hanle Effect (NLHE) on the 488 nm transition in an active discharge of an argon laser. Experimental data are used to estimate the homogeneous linewidth of the upper level of the transition. The role of the NLHE in the laser power enhancement is also discussed. Received: 22 February 1996 / Revised version: 17 June 1996     

Experimental investigation of13CD3OH infrared transitions by means of optoacoustic spectroscopy

A systematic investigation of¹³CD₃OH infrared transitions around CO₂ laser line emissions is performed by means of optoacoustic detection. Using a waveguide CO₂ laser of 290 MHz tunability and, in some cases, an acoustooptic modulator to provide an extension of 180 MHz, 108 transitions are observed. Measurements of pump off-set and relative intensity have been performed. The data may be compared with those previously reported of high resolution Fourier Transform spectroscopy.Work supported by: FAPESP, CNPq, FAEP — Brasil CNR — ItaliaPermanent address: Depto de Ciências, FEIS-UNESP (15378) I.Solteira-SP, Brasil