Relativistic kinetic theory of quantum systems: II. Neutrino-antineutrino system

It is shown that the macroscopic current density and energy-momentum density of a neutrino-antineutrino system may be expressed in terms of moments of two scalar Wigner functions, provided that the system is homogeneous on the scale of the de Broglie wavelength of the particles. The equilibrium form of these Wigner functions is established.     

A note on Keldysh's perturbation formalism

The expansion theorem of quantum field theoy relating Heisenberg operators to asymptotic free-field operators is rewritten by means of the time-path technique, originally due to Schwinger, which to date has only found application in statistical mechanics. The theorem is combined with Bogoliubov's initial condition of vanishing correlations in the infinite past to rederive Keldysh's perturbation scheme for non-equilibrium statistical Green's functions.     

Global fits of the SM and MSSM to electroweak precision data

A program including all radiative corrections to the Minimal Supersymmetric Standard Model (MSSM) at the same level as the radiative corrections to the Standard Model (SM) has been developed and used to perform global fits to all electroweak data from LEP, SLC and the Tevatron and the radiative b → sγ decay from CLEO. Values of the strong coupling constant at the M _Z scale and sin² θ _MS are derived, both in the SM and MSSM. Recent updates on electroweak data, which have been presented at the Warsaw Conference in summer 1996, reduce the too high branching ratio of the Z ⁰ boson into b-quarks in the SM from a 3.2σ to a 1.8σ effect. In addition, the b → sγ decay is 30% below the SM prediction. In the MSSM light stops and light charginos increase R _b and decrease the b → sγ rate, so both observations can be brought into agreement with the MSSM for the same region of parameter space. However, the resulting χ ² value for the MSSM fits is only marginally lower and in addition, the splitting in the stop sector has to be unnaturally high.     

Power amplification in an active model of the cochlea--short-wave case

To account for the most recent experimental results on cochlear mechanics, a mathematical model should include an active source of vibrational energy. In this note the energy gain of such a model is computed, for the case that only short waves are supported. It is shown how, via a so-called criterion function, the required energy gain can be found from the basilar-membrane velocity response.     

Calculations for diabolic pair-transfer below the Coulomb barrier

Calculations of the probabilities for two-neutron transfer in the reaction²⁰⁸Pb +¹⁶²Dy at bombarding energies below the Coulomb barrier are presented. The reaction is dominated by the strong Coulomb excitation of the rotational bands in¹⁶²Dy and¹⁶⁴Dy, while the transfer process is a weak perturbation. The presence of a diabolic point in the interval [10⁺–12⁺] in the rotational sequence, above which the transfer matrix elements change sign, leads to a reduction in the total probability for transfer of up to 25%. The relative populations of the spin states above the diabolic point exhibit an even more pronounced variation.     

Mass spectrometry of cycloheptatriene derivatives—II: Ring contraction of the molecular ion of 7-cyanocycloheptatriene. Participation of ring carbon in the loss of HCN (or HNC)

At an electron energy of 70 eV (nominal) both the [M]⁺·-ion and the [M? H]⁺-ion of the title compound expel hydrogen cyanide. ¹³C labelling in the cyano group shows that these ions lose—within experimental error—only H¹³CN when decomposing in the ion source, i.e. when possessing a relatively high internal energy. In the first and second field free region, however, as well as in the ion source at low ionizing energies (9 eV, nominal), H¹²CN is also eliminated. This phenomenon may be explained by ring contraction of the molecular ion to a six membered ring, possibly initiated by the formation of a norcaradiene structure, which may then rearrange further to a species of higher symmetry. This ring contraction is supported by the occurrence of peaks of low intensity at m/e 78 and m/e 77, due to fragments which are generated in one step from the molecular ion.     

The four quasi-particle 178Hf isomeric state,its excitation energy and multipolarities of deexciting transitions

The decay properties of the 31 y ¹⁷⁸Hf isomeric state have been investigated by means of a Ge(Li)-NaI(Tl) Compton suppression device and a Si(Li) detector, as well as with Ge(Li) and Ge(Li), intrinsic Ge and Si(Li) coincidence arrangements. From the E3 character of the unobserved isomeric transition (11.7 ≦ E_IT ≦ 16.7 keV), deduced from L-subshell and M/L ratios, I^π, K of the isomeric level was determined as 16⁺, 16. The {p[404] ↓ + p1514] ↑ + n[514] ↓ + n[624]↑}_16⁺ + four quasi-particle configuration was assigned to this level at 2447.5 ± 2.5 keV. As proposed earlier the isomeric E3 transition decays to the 13^? level of the band built upon the I^π = 8^? isomer. The |g_K?g_R| values derived from $\text{E}\text{2}\text{M}\text{1}$ ratios of interband transitions show that the 8^? isomer contains about 36 % of the p[404] ↓ + p[514] ↑ configuration and about 64 % of the n[624] ↑ + n[514] ↓ configuration.     

Metallic contact formation for molecular electronics: interactions between vapor-deposited metals and self-assembled monolayers of conjugated mono- and dithiols

We present grazing-incidence Fourier transform infrared and AFM data of Au, Al, and Ti vapor-deposited onto self-assembled monolayers (SAMs) of conjugated mono- and dithiols. SAMs of 4,4'-dimercapto-p-quaterphenyl, 4,4"-dimercapto-p-terphenyl, and 4,4'-dimercapto-p-biphenyl have reactive thiols at the SAM/vacuum interface that interact with vapor-deposited Au or Al atoms, preventing metal penetration. Conjugated monothiols lack such metal blocking groups, and metals (Au, Al) can penetrate into their SAMs. Vapor deposition of Ti onto conjugated mono- and dithiol SAMs and onto hexadecanethiol SAMs destroys the monolayers.     

Mobilitätsbestimmungen bei der elektrophorese in agargelen

Agar-gel electrophoresis allows a simple rapid determination of the mobility of a protein in relation to a reference protein (e.g. human serum albumin). The electro-osmotic transport is determined by means of an uncharged substance, usually dextran. The dextran zone can be located more exactly by chemical than mechanical means. However, chemical marking makes the correct choice of the dextran concentration important; 2% dextran seems to be optimal. The mobility of transferrin is significantly higher with 0.5% dextran than with higher concentrations.Replacement of agar bridges with foam plastic was studied for 5 migration times of 55–95 min. With agar the mobilities for transferrin were significantly higher and their fluctuations lower. Also, a dependence on migration time was found with foam but not with agar. A more exact parameter for the product field-strength 'time proved desirable ; viz. the distance between the dextran zone and the point of application (OD). The distances dextran-transferrin and dextran-albumin plotted against OD showed perfect straight lines, which could be extrapolated to the origin.     

Valency-bond studies of some conjugated hydrocarbons—II Pentalene, and some preliminary results on heptalene

Valency-bond studies of the still unknown molecule pentalene C₈H₆ in which the molecular symmetry may be either D_2h or C_2h show that a more stable molecule (lower ground state energy) is found for the lower symmetry, and that marked alternation of bond lengths occurs. The corresponding Penney-Dirac bond orders have been determined. Preliminary results for heptalene forecast a similar conclusion.