Mixed-mode impedance and reflection coefficient of two-port devices

From the point of view of mixed-mode scattering parameters, Smm, a two-port device can be excited using different driving conditions. Each condition leads to a particular set of input reflection and input impedance coefficient definitions that should be carefully applied depending on the type of excitation and symmetry of the two-port device. Therefore, the aim of this paper is to explain the general analytic procedure for the evaluation of such reflection and impedance coefficients in terms of mixed-mode scattering parameters. Moreover, the driving of a two-port device as a one-port device is explained as a particular case of a two-port mixed-mode excitation using a given set of mixed-mode loads. The theory is applied to the evaluation of the quality factor, Q, of symmetrical and non- symmetrical inductors.Ministerio de Innovación y Ciencia TEC2010-14825/MIC, TEC2010-21484Junta de Andalucía TIC-253

WEAK DIPOLE MOMENTS AT e+e−{\bf e^+e^-} COLLIDERS

The weak dipole moments of leptons and quarks, \ie those related to their $Z$--coupling, are reviewed. Standard Model predictions and experimental results may result in a stringent test for both their pointlike structure and also for the Standard Model. Special attention is devoted to the anomalous weak--magnetic dipole moment and to the $CP$--violating weak--electric dipole moment.Comment: Latex file and 2 figures included in an uucoded compressed postscript file. To appear in the proceedings of the Ringberg Workshop on "Perspectives for electroweak interactions in $e^+e^-$ collisions" hosted by the Max Planck Institut, at the Ringberg Castle, M\"unich, February 5-8, 1995. Edited by B. Knieh

Tau magnetic moment

The τ lepton magnetic moment theoretical predictions and measurements are reviewed. While it is believed that such a high mass particle is a good candidate to show up new physics, this is not the case up to now. The magnetic moment of elementary fermions, and in particular the anomalous magnetic moment of the electron, had an historical impact both in relativistic quantum mechanics and in quantum field theories. Besides, many new physics models were discarded when confronted with these magnitudes. More recently, the discrepancy of the experiments and the theoretical predictions for the muon anomalous magnetic moment is still an open issue. For the τ lepton, instead, while the theoretical prediction is well known for the standard model and some new physics models, the data are very far of determining even its sign or the first figure. We will discuss the most important theoretical aspects of the τ magnetic moment, and also the current accepted measurements and future perspectives, in particular related to B-factories

Tau spin correlations and the anomalous magnetic moment

We show that the precise determination of the Tau magnetic properties is possible in the next generation accelerators, specially at B/Flavour factories. We define spin correlation observables suitable to extract the real part of the magnetic form factor that, for the first time, will allow to test the standard model-QED predictions. In particular, the predicted QED-dependence with both the momentum transfer and the lepton mass can be precisely measured. Until now, the most stringent bounds on the $\tau$ magnetic moment $a_\tau$ come from LEP data with strong assumptions on the physics involved on the observed process. In this paper, we find three different combinations of spin correlations of the outgoing Taus that disentangle the magnetic moment form factor of the Tau lepton in the electromagnetic vertex. These combinations of asymmetries also get rid off the contributions coming from Z-mediating amplitudes to the defined correlations. Using unpolarized electron beams and an integrated luminosity of $15 \times 10^{18} b^{-1}$, the sensitivity to the $\tau$ magnetic moment form factor is of the order $10^{-6}$. This sensitivity is two orders of magnitude better than the present existing high- or low-energy bounds on the magnetic moment and would allow its actual measurement with the precision of a few per cent.Comment: 14 pages, 1 figur

Cryopreservation of embryogenic cell suspensions of the Spanish grapevine cultivars ‘Albariño’ and ‘Tempranillo’

Embryogenic cell suspensions of two elite Spanish grapevine cultivars (‘Albariño’ and ‘Tempranillo’) were successfully cryopreserved by encapsulation-dehydration. The method implied the encapsulation of cells in alginate beads, subsequent culture in liquid medium with 1 M sucrose for 4 days, and desiccation for 2-4 h in the flow of a laminar-flow bench, before immersing in liquid nitrogen. With this simple method, up to 50 % of cell viability in the cryopreserved beads was measured (using the triphenyl tetrazolium method), which corresponded to vigorous growth of 100 % of beads after culture on semi-solid medium. The cryopreserved encapsulated cells were successfully used for initiation of new cell suspensions and their embryogenic capacity was studied. This cryopreservation method is an advance to store ready-to-use competent embryogenic tissue for grapevine genetic transformation projects

CP violation and electric-dipole-moment at low energy τ\tau production with polarized electrons

The new proposals for high luminosity B/Flavor factories, near and on top of the $\Upsilon$ resonances, allow for a detailed investigation of CP-violation in the $\tau$-pair production. In particular, bounds on the tau electric dipole moment can be obtained from genuine CP-odd observables related to the $\tau$-pair production. We perform an independent analysis from low energy (10 GeV) data by means of linear spin observables. We show that, for a longitudinally polarized electron beam, a CP-odd asymmetry, associated to the normal polarization term, can be measured at these low energy facilities both at resonant and non resonant energies. In this way, stringent and independent bounds to the tau electric dipole moment, which are orders of magnitude below other high or low energy bounds, can be obtained.Comment: 12 pages, 2 figure

Tau EDM at Low Energies

Low energy tau pair production, at B factories and on top of the $\Upsilon$ resonances, allows for a detailed investigation on the CP violation at the electromagnetic tau pair production vertex. High statistic available at low energies offers the opportunity for an independent analysis of CP-violation in the $\tau$ lepton physics. We show that stringent and independent bounds on the $\tau$ electric dipole moment, competitive with the high energy measurements, can be established in low energies experiments.Comment: Talk at the Seventh International Workshop on Tau Lepton Physics (TAU02), Santa Cruz, Ca, USA, Sept 2002, 5 pages, LaTeX, 1 eps figur

Describing soil surface microrelief by crossover length and fractal dimension

International audienceAccurate description of soil surface topography is essential because different tillage tools produce different soil surface roughness conditions, which in turn affects many processes across the soil surface boundary. Advantages of fractal analysis in soil microrelief assessment have been recognised but the use of fractal indices in practice remains challenging. There is also little information on how soil surface roughness decays under natural rainfall conditions. The objectives of this work were to investigate the decay of initial surface roughness induced by natural rainfall under different soil tillage systems and to compare the performances of a classical statistical index and fractal microrelief indices. Field experiments were performed on an Oxisol at Campinas, São Paulo State (Brazil). Six tillage treatments, namely, disc harrow, disc plow, chisel plow, disc harrow + disc level, disc plow + disc level and chisel plow + disc level were tested. Measurements were made four times, firstly just after tillage and subsequently with increasing amounts of natural rainfall. Duplicated measurements were taken per treatment and date, yielding a total of 48 experimental surfaces. The sampling scheme was a square grid with 25×25 mm point spacing and the plot size was 1350×1350 mm, so that each data set consisted of 3025 individual elevation points. Statistical and fractal indices were calculated both for oriented and random roughness conditions, i.e. after height reading have been corrected for slope and for slope and tillage tool marks. The main drawback of the standard statistical index random roughness, RR, lies in its no spatial nature. The fractal approach requires two indices, fractal dimension, D, which describes how roughness changes with scale, and crossover length, l, specifying the variance of surface microrelief at a reference scale. Fractal parameters D and l, were estimated by two independent self-affine models, semivariogram (SMV) and local root mean square (RMS). Both algorithms, SMV and RMS, gave equivalent results for D and l indices, irrespective of trend removal procedure, even if some bias was present which is in accordance with previous work. Treatments with two tillage operations had the greatest D values, irrespective of evolution stage under rainfall and trend removal procedure. Primary tillage had the greatest initial values of RR and l. Differences in D values between treatments with primary tillage and those with two successive tillage operations were significant for oriented but not for random conditions. The statistical index RR and the fractal indices l and D decreased with increasing cumulative rainfall following different patterns. The l and D decay from initial value was very sharp after the first 24.4 mm cumulative rainfall. For five out of six tillage treatments a significant relationship between D and l was found for the random microrelief conditions allowing a covariance analysis. It was concluded that using RR or l together with D best allow joint description of vertical and horizontal soil roughness variations

CP violation and electric-dipole-moment at low energy tau-pair production

CP violation at low energy is investigated at the tau electromagnetic vertex. High statistics at B factories, and on top of the Upsilon resonances, allows a detailed investigation of CP-odd observables related to the tau-pair production. The contribution of the tau electric dipole moment is considered in detail. We perform an analysis independent from the high energy data by means of correlation and linear spin observables at low energy. We show that different CP-odd asymmetries, associated to the normal-transverse and normal-longitudinal correlation terms can be measured at low energy accelerators, both at resonant and non resonant energies. These observables allow to put stringent and independent bounds to the tau electric dipole moment that are competitive with other high or low energy results.Comment: 18 pages, 2 figures, references added, minor changes in section 3 and 5, to be published in Nucl.Phys.