On the work mechanism of MIM point contact diodes

We have performed systematic measurements on a W-Ni MIM point contact diode at different IR, FIR, and IF frequencies in order to investigate the mechanisms responsible for the different response times observed in the diode operation.Our results led to the experimental confirmation of a second effect of thermal nature, besides tunnel effect, responsible for the diode operation. We measure the cutoff frequency of this second effect, which results in good agreement with our theoretical interpretation.     

A hyperfine filter for the 3776 Å thallium resonance line

A magnetic hyperfine filter for the resonance line ²P_{$\text{1}\text{2}$} → ²S_{$\text{1}\text{2}$} of thallium is described. This line is a hyperfine triplet and this filter transmits only the 0→1 component connecting the lower sublevel of the ²P_{$\text{1}\text{2}$} ground state. This filter may thus be used for obtaining a population inversion in the ground state of Tl.     

Polyfunctional MDI oligomers through dendrimerization

An accessible pathway to synthesize dendronized MDI oligomers was studied. Two dendrons bearing -CN and -t-butyl functional groups on the periphery were obtained following the synthetic strategy proposed by Newkome et al. Dendrons with one focal point were converted from nitro into amino precursors and used as modifiers in the preparation of new functionalized materials. The coupling reaction of dendrons on oligomers with isocyanate groups was carried out through an easy and quick procedure. The dendronized oligomers showed conformation changes according to the polarity of the solvents, allowing a prediction of a “stimuli-responsive” behavior.     

“Laser snow” effect in CS2 vapour induced by krypton laser

We report on the laser snow effect observed in CS₂ vapour illuminated by uv lines of a krypton laser. We discuss the effect of diffusion and convection processes on the threshold value of the CS₂ vapour pressure. We discuss also the kinetics of the formation process related to the proposed model of chemical reactions induced by laser light.Work partially supported by the Gruppo Nazionale di Struttura della Materia del CNR and by the INFN.     

Quantum mechanics of 4-derivative theories

A renormalizable theory of gravity is obtained if the dimension-less 4-derivative kinetic term of the graviton, which classically suffers from negative unbounded energy, admits a sensible quantization. We find that a 4-derivative degree of freedom involves a canonical coordinate with unusual time-inversion parity, and that a correspondingly unusual representation must be employed for the relative quantum operator. The resulting theory has positive energy eigenvalues, normalizable wavefunctions, unitary evolution in a negative-norm configuration space. We present a formalism for quantum mechanics with a generic norm.     

Frequency measurement of the 496 μm line of a CH3F FIR laser

A direct frequency measurement of the 496 μm, K = 2 line from a CH₃F laser is reported. Our laser is a metallic wave-guide device pumped by a frequency stabilized CO₂ laser; its output is mixed in a CaAs-Au Schottky barrier diode with a 100 GHz klystron and the beat note is observed on a spectrum analyzer. The result is f_CH3F(496 μm, K = 2) = 604 297.5 ± 0.2 MHz.     

Relating mHiggs to mSUSY by a loop factor

We assume that the scale of the soft supersymmetry breaking masses, m_S, sliding at tree level, is fixed by the minimization of the potential, but without a significant contribution of the cosmological term. Under these assumptions the electroweak breaking scale gets related to m_S by a loop factor. Applied to specific models of supersymmetry breaking, this mechanism naturally gives sparticles slightly above all present accelerator bounds.     

Synthesis and Characterization of Dendronized Polymers

Summary: This research aims at the synthesis of several dendrons with different functional groups on their surface, and their use as functionalizing agents of synthetic polymers. Two principal products were synthesized and characterized: dendronized MDI oligomers and dendronized PMMI. The results of the characterization studies of dendronized polymers demonstrated the influence of the polarity of dendrons and the dendronization pathway on the properties of the final products.