Full Mixing Research Articles

Recent Results from the Palo Verde Neutrino Oscillation Experiment

The [Formula: see text] flux and spectrum have been measured at a distance of about 800 m from the reactors of the Palo Verde Nuclear Generating Station using a segmented Gd-loaded liquid scintillator detector. Results from the experiment show no evidence for neutrino oscillation. [Formula: see text] oscillation were excluded at 90% CL for Δm2>1.12×10-3 eV 2 for full mixing, and sin 2 2θ>0.21 for large Δm2. These results support the conclusion that the observed atmospheric neutrino oscillation does not involve νe.

Chargino and neutralino decays revisited

We perform a comprehensive analysis of the decays of charginos and neutralinos in the Minimal Supersymmetric Standard Model where the neutralino $\chi_1^0$ is assumed to be the lightest supersymmetric particle. We focus, in particular, on the three-body decays of the next-to-lightest neutralino and the lightest chargino into the lightest neutralino and fermion-antifermion pairs and include vector boson, Higgs boson and sfermion exchange diagrams, where in the latter contribution the full mixing in the third generation is included. The radiative corrections to the heavy fermion and SUSY particle masses will be also taken into account. We present complete analytical formulae for the Dalitz densities and the integrated partial decay widths in the massless fermion case, as well as the expressions of the differential decay widths including the masses of the final fermions and the polarization of the decaying charginos and neutralinos. We then discuss these decay modes, in particular in scenarios where the parameter $\tan \beta$ is large and in models without universal gaugino masses at the Grand Unification scale where some new decay channels, such as decays into gluinos and $q\bar{q}$ pairs, open up.

Deficiency of individual high molecular weight glutenin subunits affords flexibility in breeding strategies for bread-making quality in wheat Triticum aestivum L.

High-molecular-weight (HMW) glutenin subunits in wheat Triticumaestivum L., allelic variation for which affects bread-making quality, areencoded by Glu-1 homoeoloci located on the homoeologous group1 chromosomes. Many alleles at Glu-B1 and Glu-D1 producetwo subunits, an x-type of low electrophoretic mobility in polyacrylamidegels, and a y-type of high mobility. In the current study, a combination ofnear isogenic lines of cultivar `Sicco' has been used to characterise theeffect upon quality of the absence of individual subunits 7 (Glu-B1x-type), 12 (Glu-D1 y-type) and, assuming an additive model ofsubunit action, 2 (Glu-D1 x-type). Absence of subunit 7 gave amoderate reduction in SDS-sedimentation volume, indicating its associationwith lower gluten strength (confirmed by Farinogram and Extensogramstudies), yet, from a full mixing input bake, a moderate increase in loafvolume and a considerable improvement in loaf score (an overall evaluationof loaf quality). Absence of subunit 12 gave a slightly larger reduction inSDS-volume, yet no change in loaf volume or score. Absence of bothsubunits 2+12 gave a larger reduction again in SDS-volume, a moderatereduction in loaf volume and a large reduction in loaf score. Absence ofsubunit 2 alone is therefore predicted to reduce SDS-volume, loaf volumeand score such that loss of this x-type subunit would lead to larger changesin quality parameters than loss of y-type subunit 12. A general conclusionof the study is that, while deficiency for HMW glutenin subunits generallyleads to reduced gluten strength and viscoelasticity, the resultantintermediate gluten strength may on occasions lead to improvements in loafperformance in situations where the base gluten strength is high. Theremay, then, be contexts in breeding programmes where selection fordeficiency would be a possible strategy for improving bread-making quality,adding to the flexibility available to the breeder. Somewhat unexpectedly,additional analysis found that, in the genetic background of cultivar `Sicco'used in this study, subunits 7+8 at Glu-B1 were indistinguishablefrom their allelic counterparts subunits 7+9 for virtually all characters, andthat subunits 2+12 at Glu-D1, while inferior in performance formixing properties compared to subunits 5+10, were associated with goodloaf characteristics.

Increase in the primordial4Heyield in the two-doublet four-neutrino mixing scheme

Author(s): Abazajian, K; Fuller, GM; Shi, X | Abstract: We assess the effects on big bang nucleosynthesis (BBN) of lepton number generation in the early universe resulting from the two-doublet four-neutrino mass-mixing scheme. It has been argued that this neutrino mass-mixing arrangement gives the most viable fit to the existing data. We study full 4x4 mixing matrices and show how possible symmetries in these can affect the BBN 4He abundance yields. Though there is as yet no consensus on the reliability of BBN calculations with neutrino flavor mixing, we show that, in the case where the sign of the lepton number asymmetry is unpredictable, BBN considerations may pick out specific relationships between mixing angles. In particular, reconciling the observed light element abundances with a νμ⇌νe oscillation interpretation of LSND would allow unique new constraints on the neutrino mixing angles in this model. ©2000 The American Physical Society.

Mixing Effects in the Selective Noncatalytic Reduction of NO

An engineering model that combines a simple mixing model and a detailed reaction mechanism has been used to investigate selective noncatalytic reduction (SNCR) of NO. In this process a jet of NH3 is injected at high temperatures into a flue gas containing NO and O2. The mixing model used is based on the “maximum mixedness” model proposed by Zwietering. The chemical kinetic model of Miller and Glarborg was validated against experimental data obtained in a flow reactor over a range of NH3/NO/O2 compositions corresponding to conditions ranging from early jet entrainment to full mixing between reactants. The effect of mixing was investigated on three different experimental scales: A laboratory-scale diffusion-mixing reactor, a bench-scale setup, and a full-scale grate-fired furnace. The results show that finite rate mixing affects the SNCR process efficiency at high temperatures where it may cause a narrowing or a widening of the temperature window, depending on the NO concentration. The effect of mixing on the selectivity for NO reduction could be modeled qualitatively in all scales with the proposed model, using mixing times estimated from simple jet correlations. Calculations for a full-scale wood-fired grate fumace indicate that for this system with NO concentrations of 50−100 ppm the initial segregation of reactants may enhance the process efficiency. In systems with higher NO levels finite rate mixing may have an adverse effect on the SNCR process.

Fully paired-configuration mixing calculations in46Tiand48Cr

The basic theoretical formalism of angular momentum projection based on a particle-number-conserving treatment is elaborated. This method is, for the first time, applied to the middle of the fp shell. Full paired-configuration mixing calculations in the even-even deformed nuclei ${}^{46}\mathrm{Ti}$ and ${}^{48}\mathrm{Cr}$ show that only small parts $(\mathrm{weight}g0.01)$ of the configuration components are important for the case of either ground states or excited states. Low-lying excited energy spectra and reduced transition probabilities $B(E2)$ in the $K=0$ bands can be reproduced well only by admixing very limited fully paired configurations. The improvements in the energy spectra are much more prominent than those without configuration mixing. The calculated $B(E2)$ values are more reasonable in comparison with the available experimental data, as well as those from other models.

Determination of neutrino incoming direction in the CHOOZ experiment and its application to supernova explosion location by scintillator detectors

The CHOOZ experiment measured the antineutrino flux at a distance of about 1 Km from two nuclear reactors in order to detect possible neutrino oscillations with squared mass differences as low as 10**-3 eV**2 for full mixing. We show that the data analysis of the electron antineutrino events, collected by our liquid scintillation detector, locates the antineutrino source within a cone of half-aperture of about 18 degrees at the 68% C.L.. We discuss the implications of this experimental result for tracking down a supernova explosion.

Selection and coexistence by reaction-diffusion dynamics in fitness landscapes

The phenomena of selection and coexistence are modelled as chemical pattern formation by competition for a given resource in heterogeneous spatial fields (fitness landscapes). The reactions form a closed reproductive cycle so that total concentration of species and their building-blocks is kept constant in time. Eigen's `constant overall organization' conditions can be view as a particular case of proposed conditions. Species whose fitness values exceed the replication threshold govern the system dynamics. In the limit of vanishing diffusion of species and full diffusional mixing of resource, all individuals share a common niche and only the fittest survives during an evolution. In the opposite limit of negligible diffusivity of resource, there is no competition between individuals and all of them coexist. At the intermediate values of resource diffusion, a number of long-lived spatial niches are formed, which lead to long-term coexistence of locally fittest individuals.

Ice-Cover Influence on Near-Field Mixing in Dune-Bed Channel: Numerical Simulation

This paper presents the results of a numerical-simulation investigation of ice-cover influence on the mixing and transport of a neutrally buoyant contaminant released in a straight reach of a dune-bed channel. The investigation used a three-dimensional computational fluid dynamics model, validated against flume data for flow distribution in the channel and against a simple analytical solution for mixing in the channel. The model was used to simulate contaminant release near the ice-cover underside and near the bed. The results show that, for constant water discharge, cover presence reduces near-field mixing because it redistributes the flow, increases flow depth, decreases bulk velocity, reduces maximum level of turbulence, and modifies dune geometry. For the ice-covered flow, a contaminant released near the bed or near the cover underside remains closer to those boundaries over a longer distance than for open-water flow. The simulation shows that cover presence reduces the depth-averaged diffusivity to ∼45% of the corresponding diffusivity for open-water flow. The distance to attain full mixing across the flow depth increases by a commensurate amount.

An Experimental Study of Worst Case Scenarios of Nitric Acid Decomposition in a Toluene Nitration Process

Several worst case scenarios were carried out for safety evaluation of an existing nitration process. Heterogeneous nitric acid decomposition is observed to be the worst credible scenario in the toluene nitration process. Fire or explosion may subsequently develop due to temperature or pressure runaway from the undesired reaction. Gassy nitric acid decomposition can easily be triggered by process derivation from the desired reaction. In this study, a heat-flux calorimeter (C80–II) and an adiabatic calorimeter (VSP2) were used to measure the thermokinetics and determine the runaway characteristics for assessing worst credible scenarios. The heat of reaction of toluene mononitration is measured to be 190.9±6 3.6/(kJ mol −1 ). The calculated Arrhenius parameters are Ea (kJ mol −1 ) = 30.9±2.1 and A (mol −1.5 l 1.5 s −1 ) = (1.38 ± 0.07) × 10 −2 . The ‘worst case’ scenarios were chosen at the following conditions: loss of cooling, stirrer failure, batch-wise charging, and decomposition of reactants. The experimentally determined worst case was found to be a combination of a loss of cooling with batch-wise charging coupled with decomposition of nitric acid with full mixing. Adiabatic temperature rise, self-heat rate, final pressure and non-condensable gas quantity in the VSP2 experiment were used to assess thermal explosion in a nitration reactor. Unstable and critical onset temperature to runaway is determined as about 140°C for the process in this study.

Status of the Chooz experiment

The Chooz experiment is measuring the neutrino flux at distance of about 1 Km from two nuclear reactors in order to detect possible ν e → ν x oscillations with squared mass differences as low as 10 −3 eV 2 for full mixing. The sensitivity to neutrino oscillations includes the region of parameters which could explain the atmosferic neutrino anomaly by ν μ → ν e oscillations. A short description of the experiment is given; the status of the data taking and of the physics analysis is illustrated.

Entropic Effects on the Dynamical Bottleneck Location and Tunneling Contributions for C2H4 + H → C2H5: Variable Scaling of External Correlation Energy for Association Reactions

The temperature dependence of the dynamical bottleneck location for the prototype olefin addition process H + C2H4 has been studied by variational transition state theory. In addition, a multidimensional tunneling calculation has been carried out. To obtain a reliable potential energy profile, a new way to extrapolate electronic structure calculations to the limit of full configuration mixing and a complete electronic basis set is proposed. The method, called variable scaling of external correlation (VSEC) uses a scale factor that varies with geometry to combine a complete-active-space self-consistent-field (CASSCF) calculation with a calculation including an appreciable amount of the dynamical correlation energy. The parameters in the scaling factor are adjusted to experimental or high-quality theoretical data at critical points. For the title reaction we find excellent agreement with experiment at all temperatures both for the rate constant of the association reaction and also for the rate constant of i...

Analytic theory of coherent cross-gain modulation in semiconductor travelling-wave amplifiers

Abstract We report a simple analytic solution to the problem of cross amplitude-phase modulation in nonlinear two-wave mixing, under the approximation of constant saturating power. The results are applied to travelling-wave semiconductor laser amplifiers where the linewidth enhancement factor inevitably leads to amplitude-phase coupling and asymmetric energy transfer. Our solution is used to obtain the transmission gain of each beam, the spectral profile and the amplifier input-output characteristics. Limits are established as to the applicability of the analytic solution, by comparison with numerical solutions to the related full four-wave mixing problem.

Analytic theory of coherent cross-gain modulation in semiconductor travelling-wave amplifiers

We report a simple analytic solution to the problem of cross amplitude-phase modulation in nonlinear two-wave mixing, under the approximation of constant saturating power. The results are applied to travelling-wave semiconductor laser amplifiers where the linewidth enhancement factor inevitably leads to amplitude-phase coupling and asymmetric energy transfer. Our solution is used to obtain the transmission gain of each beam, the spectral profile and the amplifier input-output characteristics. Limits are established as to the applicability of the analytic solution, by comparison with numerical solutions to the related full four-wave mixing problem.

NOx-Abatement Potential of Lean-Premixed GT Combustors

The influence of the structure of perfectly premixed flames on NOx formation is investigated theoretically. Since a network of reaction kinetics modules and model flames is used for this purpose, the results obtained are independent of specific burner geometries. Calculations are presented for a mixture temperature of 630 K, an adiabatic flame temperature of 1840 K, and 1 and 15 bars combustor pressure. In particular, the following effects are studied separately from each other: • molecular diffusion of temperature and species; • flame strain; • local quench in highly strained flames and subsequent reignition; • turbulent diffusion (no preferential diffusion); • small scale mixing (stirring) in the flame front. Either no relevant influence or an increase in NOx production over that of the one-dimensional laminar flame is found. As a consequence, besides the improvement of mixing quality, a future target for the development of low-NOx burners is to avoid excessive turbulent stirring in the flame front. Turbulent flames that exhibit locally and instantaneously near laminar structures (“flamelets”) appear to be optimal. Using the same methodology, the scope of the investigation is extended to lean-lean staging, since a higher NOx-abatement potential can be expected in principle. As long as the chemical reactions of the second stage take place in the boundary between the fresh mixture of the second stage and the combustion products from upstream, no advantage can be expected from lean-lean staging. Only if the primary burner exhibits much poorer mixing than the second stage can lean-lean staging be beneficial. In contrast, if full mixing between the two stages prior to afterburning can be achieved (lean-mix-lean technique), the combustor outlet temperature can in principle be increased somewhat without NO penalty. However, the complexity of such a system with a larger flame tube area to be cooled will increase the reaction zone temperatures, so that the full advantage cannot be realized in an engine. Of greater technical relevance is the potential of a lean-mixlean combustion system within an improved thermodynamic cycle. A reheat process with sequential combustion is perfectly suited for this purpose, since, first, the required low inlet temperature of the second stage is automatically generated after partial expansion in the high pressure turbine, second, the efficiency of the thermodynamic cycle has its maximum and, third, high exhaust temperatures are generated, which can drive a powerful Rankine cycle. The higher thermodynamic efficiency of this technique leads to an additional drop in NOx emissions per power produced.

The neutrino-oscillation experiment at the CHOOZ nuclear power plant

The CHOOZ experiment is measuring the neutrino flux from two nuclear reactors at a distance of 1 km. The aim is to search for possible ν e → ν x oscillations in a region of parameters ( Δm 2 ≥ 10 −3eV 2 at full mixing) where hints at neutrino oscillations come from the measurement of the atmosferic neutrino flux. A short description of the status of the experiment (data taking and physics analysis) is given.

Theoretical and experimental studies of CIDNP kinetics in recombination of radical pairs by the method of switched external magnetic field. I. Theory

The theory of chemically induced dynamic nuclear polarization (CIDNP) of radical pairs in restricted volume formed in experiments with instantaneously switched external magnetic field is developed. For this purpose the theory of recombination of radical pairs with instantaneously changed spin Hamiltonian is extended to the case of rather weak magnetic fields. Using kinematic approximation it is shown that the recombination probability of radical pairs is fully expressed via the matrix formulas in terms of averages of Green’s functions of Liouville equation over both the reaction zone and that of energy level crossing. The effect of field switching on the CIDNP value is calculated for the typical parameters of the radical pairs. Simple biexponential expressions are derived for the CIDNP time dependencies for the case of strongly averaged S−T0 transitions and full mixing in configuration space.

On a weak (algebraic) extremum principle for a second-order parabolic system

The notion of a weak “algebraic” extremum principle (WAEP) is introduced for second-order parabolic systems. It is based on the representation of the (coefficient) matrix of the system as a sum of matrices that are similar to diagonal matrices and nilpotent matrices, and on the reduction of the system to a single equation. The validity of the WAEP is proved for a rather broad class of second-order parabolic systems with “full mixing”. The WAEP is applied to prove the uniqueness of the solution of the first boundary-value problem for the parabolic systems in question.

Dominance of the nucleon decay K-channels in PLR invariant SO(10)

RH rotations of the fermionic mass matrices are not observable in the standard model, but dictate the details of the proton decay in GUTs. $P_{LR}$ symmetry in the two light families leads to a full RH mixing. We give two versions of suitable broken $P_{LR}$ invariant SO(10) which leads to nucleon decay modes similar to those of SUSY-GUTs with rates in the range of observability of superKamiokande and ICARUS.

The NOMAD experiment: a status report

NOMAD is an experiment searching for ν μ(e) → ν τ oscillations at the CERN SPS Wide-Band neutrino Beam. This search is performed via the appearance of ν τ in a predominantly ν μ beam of 24 GeV average energy. The experiment has been designed to allow a kinematical selection of ν τ charged current interactions from the background of ν μ and ν e charged and neutral current interactions and has maximum sensitivity in sin 2 2 θ for Δm 2 greater than 40 eV 2 , and some sensitivity remains for Δm 2 down to 1 eV 2 in the case of full mixing. NOMAD has taken data with the full detector since August 1995, and will pursue the oscillations search until the end of 1997. Charged and neutral current interactions of ν μ , ν¯ μ , ν e and V¯ e have been identified and comparisons between data and Monte-Carlo are presented. The status of the ν μ → ν τ oscillation search using various tau decay channels ( τ → μ , τ → e, τ → hadrons) is also reported.