Flexoelectric polarisation effects in nematic liquid crystal phase gratings

Nematic phase gratings have been studied in which a planar nematic layer of thickness 17.2 μm is sandwiched between two glass substrates coated with an alignment polymer. The upper substrate is a continuous earth plane and the lower substrate has a patterned electrode of interdigitated stripes (electrodes and gaps are both 40 μm wide). Reorientation of the nematic liquid crystal occurs in response to d.c. electric fields applied between the interdigitated electrodes. These nematic reorientation regions have been used to investigate the influence of the flexoelectric polarisation in the nematic liquid crystal by observing the resultant (i) movement of tilt fringes in a Mach-Zehnder interferometer, and (ii) optical diffraction patterns. In the Mach-Zehnder interferometer the periodic variation of the refractive index resulting from the periodic distortion profile is measured directly from the displacement of the tilt fringes. The asymmetry in the response to positive and negative polarities of the d.c. voltage for both measurement techniques is directly related to the sum of the flexoelectric coefficients, e1 + e3

Divide-and-Conquer Distributed Learning: Privacy-Preserving Offloading of Neural Network Computations

Machine learning has become a highly utilized technology to perform decision making on high dimensional data. As dataset sizes have become increasingly large so too have the neural networks to learn the complex patterns hidden within. This expansion has continued to the degree that it may be infeasible to train a model from a singular device due to computational or memory limitations of underlying hardware. Purpose built computing clusters for training large models are commonplace while access to networks of heterogeneous devices is still typically more accessible. In addition, with the rise of 5G networks, computation at the edge becoming more commonplace, and inspired by the successes of the folding@home project utilizing crowdsourced computation, we consider the scenario of the crowdsourcing the computation required for training of a neural network particularly appealing. Distributed learning promises to bridge the widening gap between singular device performance and large-scale model computational requirements, but unfortunately, current distributed learning techniques do not maintain privacy of both the model and input with- out an accuracy or computational tradeoff. In response, we present Divide and Conquer Learning (DCL), an innovative approach that enables quantifiable privacy guarantees while offloading the computational burden of training to a network of devices. A user can divide the training computation of its neural network into neuron-sized computation tasks and dis- tribute them to devices based on their available resources. The results will be returned to the user and aggregated in an iterative process to obtain the final neural network model. To protect the privacy of the user’s data and model, shuffling is done to both the data and the neural network model before the computation task is distributed to devices. Our strict adherence to the order of operations allows a user to verify the correctness of performed computations through assigning a task to multiple devices and cross-validating their results. This can protect against network churns and detect faulty or misbehaving devices

Spatio-temporal patterns of crab fisheries in the main bays of Guangdong Province, China

Using a semi-balloon otter trawl, crab fisheries in the main bays of Guangdong Province, China, were carried out seasonally . A total of 70 species were found, all belonging to the South China Sea Faunal sub region in the tropical India-West-Pacific Faunal Region. The clustering and nMDS ordination analysis revealed the existence of three groups. Group 1 included Hailing Bay and four bays to its east where typical species were Portunus sanguinolentus, P. pelagicus and Charybdis feriatus. Group 2 included Shuidong Bay and Leizhou Bay where typical species were P. sanguinolentus, P. pelagicus and P. hastatoides. Group 3 was Liusha Bay where typical species were C. feriatus, C. vadorum and C. truncate. The spatial and temporal variations of crab fisheries were mainly associated with characteristics of the sediment, seasonal changes and their own biological characteristics, but not significantly with water depth, temperature, salinity, and the “mid-summer fishing moratorium” conservation measure

Applying process-based models to the Borssele scenario

The objective of this paper is to consider the implications of employing process-based models on predictions for radionuclide activity concentrations in grass and cow milk. The FDMT (Food Chain and Dose Module for Terrestrial Pathways as used in the JRODOS and ARGOS decision support systems) model has been transferred to a modelling platform enabling sub-models to be modified and replaced. Primarily, this has involved invoking process-based models for 137Cs and 90Sr that account for soil chemistry in simulating bioavailability and plant transfer. The implementation of such models can lead to quite dramatic differences in predicted activity concentrations of radionuclides in grass and milk compared to a default FDMT set-up for time periods later than a few weeks post deposition. Considering transfer within a spatial context, by combining information from the outputs of process-based models with illustrative soil maps, leads to the observation that the most elevated 137Cs and 90Sr concentrations in grass and milk might not necessarily occur in areas where deposition is highest. Not accounting for soil type when modelling food chain transfer might lead to the sub-optimal allocation of resources or misidentification of the most vulnerable areas in the long-term after an accidental release

Zeroing in on more photons and gluons

We discuss radiation zeros that are found in gauge tree amplitudes for processes involving multi-photon emission. Previous results are clarified by examples and by further elaboration. The conditions under which such amplitude zeros occur are identical in form to those for the single-photon zeros, and all radiated photons must travel parallel to each other. Any other neutral particle likewise must be massless (e.g. gluon) and travel in that common direction. The relevance to questions like gluon jet identification and computational checks is considered. We use examples to show how certain multi-photon amplitudes evade the zeros, and to demonstrate the connection to a more general result, the decoupling of an external electromagnetic plane wave in the ``null zone". Brief comments are made about zeros associated with other gauge-boson emission.Comment: 26 page

1.5W diode-pumped monolithic planar waveguide laser

We describe a compact and efficient Nd:YAG waveguide laser pumped by a diode-bar. An output of 1.5W is obtained for 6W incident power, with significant brightness enhancement

Altered functional brain network connectivity and glutamate system function in transgenic mice expressing truncated Disrupted-in-Schizophrenia 1

Considerable evidence implicates DISC1 as a susceptibility gene for multiple psychiatric diseases. DISC1 has been intensively studied at the molecular, cellular and behavioral level, but its role in regulating brain connectivity and brain network function remains unknown. Here, we utilize a set of complementary approaches to assess the functional brain network abnormalities present in mice expressing a truncated Disc1 gene (Disc1tr Hemi mice). Disc1tr Hemi mice exhibited hypometabolism in the prefrontal cortex (PFC) and reticular thalamus along with a reorganization of functional brain network connectivity that included compromised hippocampal–PFC connectivity. Altered hippocampal–PFC connectivity in Disc1tr Hemi mice was confirmed by electrophysiological analysis, with Disc1tr Hemi mice showing a reduced probability of presynaptic neurotransmitter release in the monosynaptic glutamatergic hippocampal CA1–PFC projection. Glutamate system dysfunction in Disc1tr Hemi mice was further supported by the attenuated cerebral metabolic response to the NMDA receptor (NMDAR) antagonist ketamine and decreased hippocampal expression of NMDAR subunits 2A and 2B in these animals. These data show that the Disc1 truncation in Disc1tr Hemi mice induces a range of translationally relevant endophenotypes underpinned by glutamate system dysfunction and altered brain connectivity

On Relativistic Material Reference Systems

This work closes certain gaps in the literature on material reference systems in general relativity. It is shown that perfect fluids are a special case of DeWitt's relativistic elastic media and that the velocity--potential formalism for perfect fluids can be interpreted as describing a perfect fluid coupled to a fleet of clocks. A Hamiltonian analysis of the elastic media with clocks is carried out and the constraints that arise when the system is coupled to gravity are studied. When the Hamiltonian constraint is resolved with respect to the clock momentum, the resulting true Hamiltonian is found to be a functional only of the gravitational variables. The true Hamiltonian is explicitly displayed when the medium is dust, and is shown to depend on the detailed construction of the clocks.Comment: 18 pages, ReVTe

Effect of Tensor Correlations on Gamow-Teller States in 90Zr and 208Pb

The tensor terms of the Skyrme effective interaction are included in the self-consistent Hartree-Fock plus Random Phase Approximation (HF+RPA) model. The Gamow-Teller (GT) strength function of 90Zr and 208Pb are calculated with and without the tensor terms. The main peaks are moved downwards by about 2 MeV when including the tensor contribution. About 10% of the non-energy weighted sum rule is shifted to the excitation energy region above 30 MeV by the RPA tensor correlations. The contribution of the tensor terms to the energy weighted sum rule is given analytically, and compared to the outcome of RPA.Comment: 13 pages, 2 figures,2 table