Deep Bilevel Learning

We present a novel regularization approach to train neural networks that enjoys better generalization and test error than standard stochastic gradient descent. Our approach is based on the principles of cross-validation, where a validation set is used to limit the model overfitting. We formulate such principles as a bilevel optimization problem. This formulation allows us to define the optimization of a cost on the validation set subject to another optimization on the training set. The overfitting is controlled by introducing weights on each mini-batch in the training set and by choosing their values so that they minimize the error on the validation set. In practice, these weights define mini-batch learning rates in a gradient descent update equation that favor gradients with better generalization capabilities. Because of its simplicity, this approach can be integrated with other regularization methods and training schemes. We evaluate extensively our proposed algorithm on several neural network architectures and datasets, and find that it consistently improves the generalization of the model, especially when labels are noisy.Comment: ECCV 201

The development of student learning and information literacy: a case study [conference item]

Literacy is documented as a fundamental human right. The ability to exercise this right improves an individual’s life chances by achieving their personal, social, occupational and educational goals, and it opens opportunities for social, economic and political integration. Currently in an information and knowledge society, there is a salient need for Information Literacy (IL). IL can be defined as knowing when and why one might need information, where to find it, and how to evaluate, use and communicate it in an ethical manner. There is a need for undergraduate and postgraduate students to demonstrate a competency with information literacy skills. For example it is essential for the student to develop a thesis statement, i.e. research question and to consequently search, organise, share and evaluate the results. In this paper we present a case studyhighligting the role of Library and Student Support (LSS) based at Middlesex University London. LSS works in conjunction with University Departments (Schools) and leads on the development and implementation of a coherent and strategic approach to the development of learner competencies. These are identified through the development and implementation of relevant University policies and strategies. We argue that other Higher Education institutions may benefit from our experience of implementing IL policy in collaboration with a Library and Student Support Service

The development of student learning and information literacy: a case study

Literacy is a fundamental human right. When exercised it improves an individual’s life chances by achieving their personal, social, occupational and educational goals, and opening opportunities for social, economic and political integration. In an information and knowledge society, there is a salient need for Information Literacy (IL). IL can be defined as knowing when and why one might need information, where to find it, and how to evaluate, use and communicate it in an ethical manner. There is a need for undergraduate and postgraduate students to demonstrate a competency with IL skills. For example it is essential for the student to develop a thesis statement and to consequently search, organise, share and evaluate the results. In this paper we present a case study highlighting the role of Library and Student Support (LSS) based at Middlesex University London. LSS works in conjunction with University Departments and leads on the development and implementation of a coherent and strategic approach to improving learner competencies. These are identified through the development and implementation of relevant University policies and strategies. We argue that other Higher Education institutions may benefit from our experience of implementing IL policy in collaboration with a Library and Student Support service

Vortex fluctuations in underdoped Bi2Sr2CaCu2O8+d crystals

Vortex thermal fluctuations in heavily underdoped Bi2Sr2CaCu2O8+d (Tc=69.4 K) are studied using Josephson plasma resonance (JPR). From the data in zero magnetic field, we obtain the penetration depth along the c-axis, lambda_{L,c}(0) = 229 micrometers and the anisotropy ratio gamma(0) = 600. The low plasma frequency allows us to study phase correlations over the whole vortex solid (Bragg-glass) state. The JPR results yield a wandering length r_{w} of vortex pancakes. The temperature dependence of r_{w} as well as its increase with applied dc magnetic field can only be explained by the renormalization of the tilt modulus by thermal fluctuations, and suggest the latter is responsible for the dissociation of the vortices at the first order transition.Comment: 4 pages, 5 figures. Submitted to Phys. Rev. Let

Photon emission by an ultra-relativistic particle channeling in a periodically bent crystal

This paper is devoted to a detailed analysis of the new type of the undulator radiation generated by an ultra-relativistic charged particle channeling along a crystal plane, which is periodically bent by a transverse acoustic wave, as well as to the conditions limiting the observation of this phenomenon. This mechanism makes feasible the generation of electromagnetic radiation, both spontaneous and stimulated, emitted in a wide range of the photon energies, from X- up to gamma-rays

Crystal structure of the SARS-CoV-2 non-structural protein 9, Nsp9

Many of the SARS-CoV-2 proteins have related counterparts across the Severe Acute Respiratory Syndrome (SARS-CoV) family. One such protein is non-structural protein 9 (Nsp9), which is thought to mediate viral replication, overall virulence, and viral genomic RNA reproduction. We sought to better characterize the SARS-CoV-2 Nsp9 and subsequently solved its X-ray crystal structure, in an apo form and, unexpectedly, in a peptide-bound form with a sequence originating from a rhinoviral 3C protease sequence (LEVL). The SARS-CoV-2 Nsp9 structure revealed the high level of structural conservation within the Nsp9 family. The exogenous peptide binding site is close to the dimer interface and impacted the relative juxtapositioning of the monomers within the homodimer. We have established a protocol for the production of SARS-CoV-2 Nsp9, determined its structure, and identified a peptide-binding site that warrants further study to understanding Nsp9 function

ESR study of the single-ion anisotropy in the pyrochlore antiferromagnet Gd2Sn2O7

Single-ion anisotropy is of importance for the magnetic ordering of the frustrated pyrochlore antiferromagnets Gd2Ti2O7 and Gd2Sn2O7. The anisotropy parameters for the Gd2Sn2O7 were measured using the electron spin resonance (ESR) technique. The anisotropy was found to be of the easy plane type, with the main constant D=140mK. This value is 35% smaller than the value of the corresponding anisotropy constant in the related compound Gd2Ti2O7.Comment: 8 pages, 3 figure