Model Predictions for Neutrino Oscillation Parameters

We have surveyed leptonic and grand unified models of neutrino masses and mixings in the literature which are still viable and give numerical predictions for the reactor angle, $\theta_{13}$. The results are of considerable interest in anticipation of the next generation reactor experiments and the possible future need for neutrino factories. Of the 63 models considered which were published or posted on the Archive before June 2006, half predict values of \sin^2 2\theta_{13} \gsim 0.015, which should yield positive signals for $\bar{\nu}_e$ disappearance in the reactor experiments planned for the near future. Depending upon the outcome of those experiments, half of the models can be eliminated on the basis of the presence or absence of such an observed $\bar{\nu}_e$ disappearance signal.Comment: 23 pages including 3 figures; published versio

Potential Vorticity Mixing in a Tangled Magnetic Field

A theory of potential vorticity (PV) mixing in a disordered (tangled) magnetic field is presented. The analysis is in the context of $\beta$-plane MHD, with a special focus on the physics of momentum transport in the stably stratified, quasi-2D solar tachocline. A physical picture of mean PV evolution by vorticity advection and tilting of magnetic fields is proposed. In the case of weak-field perturbations, quasi-linear theory predicts that the Reynolds and magnetic stresses balance as turbulence Alfv\'enizes for a larger mean magnetic field. Jet formation is explored quantitatively in the mean field-resistivity parameter space. However, since even a modest mean magnetic field leads to large magnetic perturbations for large magnetic Reynolds number, the physically relevant case is that of a strong but disordered field. We show that numerical calculations indicate that the Reynolds stress is modified well before Alfv\'enization -- i.e. before fluid and magnetic energies balance. To understand these trends, a double-average model of PV mixing in a stochastic magnetic field is developed. Calculations indicate that mean-square fields strongly modify Reynolds stress phase coherence and also induce a magnetic drag on zonal flows. The physics of transport reduction by tangled fields is elucidated and linked to the related quench of turbulent resistivity. We propose a physical picture of the system as a resisto-elastic medium threaded by a tangled magnetic network. Applications of the theory to momentum transport in the tachocline and other systems are discussed in detail.Comment: 17 pages, 10 figures, 2 table

Scalable Image Retrieval by Sparse Product Quantization

Fast Approximate Nearest Neighbor (ANN) search technique for high-dimensional feature indexing and retrieval is the crux of large-scale image retrieval. A recent promising technique is Product Quantization, which attempts to index high-dimensional image features by decomposing the feature space into a Cartesian product of low dimensional subspaces and quantizing each of them separately. Despite the promising results reported, their quantization approach follows the typical hard assignment of traditional quantization methods, which may result in large quantization errors and thus inferior search performance. Unlike the existing approaches, in this paper, we propose a novel approach called Sparse Product Quantization (SPQ) to encoding the high-dimensional feature vectors into sparse representation. We optimize the sparse representations of the feature vectors by minimizing their quantization errors, making the resulting representation is essentially close to the original data in practice. Experiments show that the proposed SPQ technique is not only able to compress data, but also an effective encoding technique. We obtain state-of-the-art results for ANN search on four public image datasets and the promising results of content-based image retrieval further validate the efficacy of our proposed method.Comment: 12 page

Electric-field control of magnetic ordering in the tetragonal BiFeO3

We propose a way to use electric-field to control the magnetic ordering of the tetragonal BiFeO3. Based on systematic first-principles studies of the epitaxial strain effect on the ferroelectric and magnetic properties of the tetragonal BiFeO3, we find that there exists a transition from C-type to G-type antiferromagnetic (AFM) phase at in-plane constant a ~ 3.905 {\AA} when the ferroelectric polarization is along [001] direction. Such magnetic phase transition can be explained by the competition between the Heisenberg exchange constant J1c and J2c under the influence of biaxial strain. Interestingly, when the in-plane lattice constant enlarges, the preferred ferroelectric polarization tends to be canted and eventually lies in the plane (along [110] direction). It is found that the orientation change of ferroelectric polarization, which can be realized by applying external electric-field, has significant impact on the Heisenberg exchange parameters and therefore the magnetic orderings of tetragonal BiFeO3. For example, at a ~ 3.79 {\AA}, an electric field along [111] direction with magnitude of 2 MV/cm could change the magnetic ordering from C-AFM to G-AFM. As the magnetic ordering affects many physical properties of the magnetic material, e.g. magnetoresistance, we expect such strategy would provide a new avenue to the application of multiferroic materials.Comment: 4 pages, 4 figure

Physical mechanism of superluminal traversal time: interference between multiple finite wave packets

The mechanism of superluminal traversal time through a potential well or potential barrier is investigated from the viewpoint of interference between multiple finite wave packets, due to the multiple reflections inside the well or barrier. In the case of potential-well traveling that is classically allowed, each of the successively transmitted constituents is delayed by a subluminal time. When the thickness of the well is much smaller in comparision with a characteristic length of the incident wave packet, the reshaped wave packet in transmission maintains the profile of the incident wave packet. In the case of potential-barrier tunneling that is classically forbidden, though each of the successively transmitted constituents is delayed by a time that is independent of the barrier thickness, the interference between multiple transmitted constituents explains the barrier-thickness dependence of the traversal time for thin barriers and its barrier-thickness independence for thick barriers. This manifests the nature of Hartman effect.Comment: 9 pages, 3 figures, Some comments and suggestions are appreciate

Dirac Leptogenesis with a Non-anomalous U(1)′U(1)^{\prime} Family Symmetry

We propose a model for Dirac leptogenesis based on a non-anomalous $U(1)^{\prime}$ gauged family symmetry. The anomaly cancellation conditions are satisfied with no new chiral fermions other than the three right-handed neutrinos, giving rise to stringent constraints among the charges. Realistic masses and mixing angles are obtained for all fermions. The model predicts neutrinos of the Dirac type with naturally suppressed masses. Dirac leptogenesis is achieved through the decay of the flavon fields. The cascade decays of the vector-like heavy fermions in the Froggatt-Nielsen mechanism play a crucial role in the separation of the primodial lepton numbers. We find that a large region of parameter space of the model gives rise to a sufficient cosmological baryon number asymmetry through Dirac leptogenesis.Comment: 8 pages, 8 figures, version to appear in JHE

Probing the C-H Activation of Linear and Cyclic Ethers at (PNP)Ir

Interaction of the amido/bis(phosphine)-supported (PNP)Ir fragment with a series of linear and cyclic ethers is shown to afford, depending on substrate, products of α,α-dehydrogenation (carbenes), α,β-dehydrogenation (vinyl ethers), or decarbonylation. While carbenes are exclusively obtained from tert-amyl methyl ether, sec-butyl methyl ether (SBME), n-butyl methyl ether (NBME), and tetrahydrofuran (THF), vinyl ethers or their adducts are observed upon reaction with diethyl ether and 1,4-dioxane. Decarbonylation occurs upon interaction of (PNP)Ir with benzyl methyl ether, and a mechanism is proposed for this unusual transformation, which occurs via a series of C−H, C−O, and C−C bond cleavage events. The intermediates characterized for several of these reactions as well as the α,α-dehydrogenation of tert-butyl methyl ether (MTBE) are used to outline a reaction pathway for the generation of PNP-supported iridium(I) carbene complexes, and it is shown that the long-lived, observable intermediates are substrate-dependent and differ for the related cases of MTBE and THF. Taken together, these findings highlight the variety of pathways utilized by the electron-rich, unsaturated (PNP)Ir fragment to stabilize itself by transferring electron density to ethereal substrates through oxidative addition and/or the formation of π-acidic ligands

Cascade refinement extraction network with active boundary loss for segmentation of concrete cracks from high-resolution images

Accurate extraction of cracks is important yet challenging in bridge inspection, particularly that of tiny cracks captured from high-resolution (HR) images. This paper presents a crack-boundary refinement framework (CBRF) for meticulous segmentation of HR crack images. First, a triple-scale feature extraction module is designed to enhance the representation of miniscule-crack pixels. Then, a cascade operation involving global and local steps is adopted to conduct the refinement. In addition, an active boundary loss is introduced into the training process to solve the semantic inconsistency of crack boundary areas. The first HR crack image dataset is established to thoroughly evaluate the CBRF. Finally, an unmanned aerial vehicle (UAV)-based case study is conducted on the Yinpenling Bridge, which further confirms the practicality of the CBRF in improving the safety and efficiency of UAV-based bridge detection while ensuring the accuracy