16,020 research outputs found
Dual regimes of ion migration in high repetition rate femtosecond laser inscribed waveguides
Ion migration in high repetition rate femtosecond laser inscribed waveguides
is currently being reported in different optical glasses. For the first time we
discuss and experimentally demonstrate the presence of two regimes of ion
migration found in laser written waveguides. Regime-I, corresponds to the
initial waveguide formation mainly via light element migration (in our case
atomic weight < 31u), whereas regime-II majorly corresponds to the movement of
heavy elements. This behavior brings attention to a problem which has never
been analyzed before and that affects laser written active waveguides in which
active ions migrate changing their local spectroscopic properties. The
migration of active ions may in fact detune the pre-designed optimal values of
active photonic devices. This paper experimentally evidences this problem and
provides solutions to avert it.Comment: 4 pages, 5 figure
Unitarity of the Leptonic Mixing Matrix
We determine the elements of the leptonic mixing matrix, without assuming
unitarity, combining data from neutrino oscillation experiments and weak
decays. To that end, we first develop a formalism for studying neutrino
oscillations in vacuum and matter when the leptonic mixing matrix is not
unitary. To be conservative, only three light neutrino species are considered,
whose propagation is generically affected by non-unitary effects. Precision
improvements within future facilities are discussed as well.Comment: Standard Model radiative corrections to the invisible Z width
included. Some numerical results modified at the percent level. Updated with
latest bounds on the rare tau decay. Physical conculsions unchange
Magnetic transitions in Pr2NiO4 single crystal
The magnetic properties of a stoichiometric Pr2NiO4 single crystal have been examined by means of the temperature dependence of the complex ac susceptibility and the isothermal magnetization in fields up to 200 kOe at T=4.2 K. Three separate phases have been identified and their anisotropic character has been analyzed. A collinear antiferromagnetic phase appears first between TN = 325 K and Tc1 = 115 K, where the Pr ions are polarized by an internal magnetic field. At Tc1 a first modification of the magnetic structure occurs in parallel with a structural phase transition (Bmab to P42/ncm). This magnetic transition has a firstâorder character and involves both the outâofâplane and the inâplane spin components (magnetic modes gx and gxcyfz, respectively). A second magnetic transition having also a firstâorder character is also clearly identified at Tc2 = 90 K which corresponds to a spin reorientation process (gxcyfz to cxgyaz magnetic modes). It should be noted as well that the outâofâphase component of Ïac shows a peak around 30 K which reflects the coexistence of both magnetic configurations in a wide temperature interval. Finally, two fieldâinduced transitions have been observed at 4.2 K when the field is directed along the c axis. We propose that the highâfield anomaly arises from a metamagnetic transition of the weak ferromagnetic component, similarly to La2CuO4
Phenomenology of double deeply virtual Compton scattering in the era of new experiments
We revisit the phenomenology of the deep exclusive electroproduction of a
lepton pair, i.e. double deeply virtual Compton scattering (DDVCS), in view of
new experiments planned in the near future. The importance of DDVCS in the
reconstruction of generalized parton distributions (GPDs) in their full
kinematic domain is emphasized. Using Kleiss-Stirling spinor techniques, we
provide the leading order complex amplitudes for both DDVCS and Bethe-Heithler
sub-processes. Such a formulation turns out to be convenient for practical
implementation in the PARTONS framework and EpIC Monte Carlo generator that we
use in simulation studies.Comment: 21 pages, 13 figure
Prospects for GPDs extraction with Double DVCS
Double deeply virtual Compton scattering (DDVCS) is the process where an
electron scatters off a nucleon and produces a lepton pair. The main advantage
of this process in contrast with deeply virtual and timelike Compton
scatterings (DVCS and TCS) is the possibility of directly measuring GPDs for
at leading order in (LO). We present a new calculation
of the DDVCS amplitude based on the methods developed by R. Kleiss and W. J.
Stirling in the 1980s. These techniques produce expressions for amplitudes that
are perfectly suited for implementation in numerical simulations. Via the
PARTONS software, the correctness of this new formulation has been tested by
comparing the DVCS and TCS limits of DDVCS with independent calculations of
DVCS and TCS.Comment: 5 pages, 4 figures, proceedings for the XXIX Cracow Epiphany
Conferenc
Thermodynamic properties of CO2 + SO2 + CH4 mixtures over wide ranges of temperature and pressure. Evaluation of CO2/SO2 co-capture in presence of CH4 for CCS
In this work, density, vapor-liquid equilibrium and speed of sound measurements of the mixtures [CO2+ 4.72 mol% SO2+ 1.85 mol% CH4] and [CO2+ 0.09 mol% SO2+ 1.54 mol% CH4] were performed over the temperature range 263-373 K and at pressures of up to 30 MPa for density and up to 190 MPa for speed of sound. For the speed of sound measurements, the mixtures were doped with congruent to 0.8 mol% CH3OH. We compared our results to the values calculated using an extended version of the equation of state for combustion gases (EOSCG) that includes binary models for the CO2+ SO2 and CO2+ CH4 subsystems, and a perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state, validating both equations in this way. From our experimental results, we evaluated the impact of the simultaneous presence of SO2 and CH4 as impurities in anthropogenic CO2 on selected parameters for carbon capture and storage technology. With the understanding that chemical effects have not been considered, we concluded that the presence of 4.72 mol% SO2 compensates for the negative effect of 1.85 mol% CH4 on most of the studied parameters, resulting in a favorable fluid for carbon, capture and storage, contrary to the mixture with 0.09 mol% SO2 and 1.54 mol% CH4
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