MALA-within-Gibbs samplers for high-dimensional distributions with sparse conditional structure

Markov chain Monte Carlo (MCMC) samplers are numerical methods for drawing samples from a given target probability distribution. We discuss one particular MCMC sampler, the MALA-within-Gibbs sampler, from the theoretical and practical perspectives. We first show that the acceptance ratio and step size of this sampler are independent of the overall problem dimension when (i) the target distribution has sparse conditional structure, and (ii) this structure is reflected in the partial updating strategy of MALA-within-Gibbs. If, in addition, the target density is blockwise log-concave, then the sampler's convergence rate is independent of dimension. From a practical perspective, we expect that MALA-within-Gibbs is useful for solving high-dimensional Bayesian inference problems where the posterior exhibits sparse conditional structure at least approximately. In this context, a partitioning of the state that correctly reflects the sparse conditional structure must be found, and we illustrate this process in two numerical examples. We also discuss trade-offs between the block size used for partial updating and computational requirements that may increase with the number of blocks

On electromagnetic interactions for massive mixed symmetry field

In this paper we investigate electromagnetic interactions for simplest massive mixed symmetry field. Using frame-like gauge invariant formulation we extend Fradkin-Vasiliev procedure, initially proposed for investigation of gravitational interactions for massless particles in AdS space, to the case of electromagnetic interactions for massive particles leaving in (A)dS space with arbitrary value of cosmological constant including flat Minkowski space. At first, as an illustration of general procedure, we re-derive our previous results on massive spin 2 electromagnetic interactions and then we apply this procedure to massive mixed symmetry field. These two cases are just the simplest representatives of two general class of fields, namely completely symmetric and mixed symmetry ones, and it is clear that the results obtained admit straightforward generalization to higher spins as well.Comment: 17 pages. Some clarifications added. Version to appear in JHE

Two-Stage Convolutional Neural Network for Breast Cancer Histology Image Classification

This paper explores the problem of breast tissue classification of microscopy images. Based on the predominant cancer type the goal is to classify images into four categories of normal, benign, in situ carcinoma, and invasive carcinoma. Given a suitable training dataset, we utilize deep learning techniques to address the classification problem. Due to the large size of each image in the training dataset, we propose a patch-based technique which consists of two consecutive convolutional neural networks. The first "patch-wise" network acts as an auto-encoder that extracts the most salient features of image patches while the second "image-wise" network performs classification of the whole image. The first network is pre-trained and aimed at extracting local information while the second network obtains global information of an input image. We trained the networks using the ICIAR 2018 grand challenge on BreAst Cancer Histology (BACH) dataset. The proposed method yields 95 % accuracy on the validation set compared to previously reported 77 % accuracy rates in the literature. Our code is publicly available at https://github.com/ImagingLab/ICIAR2018Comment: 10 pages, 5 figures, ICIAR 2018 conferenc

Diagonal deformations of thin center vortices and their stability in Yang-Mills theories

The importance of center vortices for the understanding of the confining properties of SU(N) Yang-Mills theories is well established in the lattice. However, in the continuum, there is a problem concerning the relevance of center vortex backgrounds. They display the so called Savvidy-Nielsen-Olesen instability, associated with a gyromagnetic ratio $g^{(b)}_m=2$ for the off-diagonal gluons. In this work, we initially consider the usual definition of a {\it thin} center vortex and rewrite it in terms of a local color frame in SU(N) Yang-Mills theories. Then, we define a thick center vortex as a diagonal deformation of the thin object. Besides the usual thick background profile, this deformation also contains a frame defect coupled with gyromagnetic ratio $g^{(d)}_m=1$, originated from the charged sector. As a consequence, the analysis of stability is modified. In particular, we point out that the defect should stabilize a vortex configuration formed by a pair of straight components separated by an appropriate finite distance.Comment: 20 pages, LaTe

Spin 3 cubic vertices in a frame-like formalism

Till now most of the results on interaction vertices for massless higher spin fields were obtained in a metric-like formalism using completely symmetric (spin-)tensors. In this, the Lagrangians turn out to be very complicated and the main reason is that the higher the spin one want to consider the more derivatives one has to introduce. In this paper we show that such investigations can be greatly simplified if one works in a frame-like formalism. As an illustration we consider massless spin 3 particle and reconstruct a number of vertices describing its interactions with lower spin 2, 1 and 0 ones. In all cases considered we give explicit expressions for the Lagrangians and gauge transformations and check that the algebra of gauge transformations is indeed closed.Comment: 17 pades, no figure

Hong Kong chapter report

Yiu-ming Cheung from Hong Kong Baptist University, China, and Michael Chau from The University of Hong Kong, China, has discussed significant facts of the IEEE (Hong Kong) Computational Intelligence Chapter report. The Hong Kong Chapter, founded in 2003, is aimed at coordinating and supporting work and stimulating the public's interests in the field of Computational Intelligence in the city. They have organized many activities that can be classified in four categories, such as conference co-organization and sponsorship, academic seminars, industry visits, and student project/paper competition, to meet their goal. The Chapter organized several academic seminars on topics regarding computational intelligence for enabling the members and the local community a communication channel to share their expertise and intelligence. The Chapter also organized several industry visits for making the members aware of the latest development of computational intelligence technologies in the industry.published_or_final_versio

Intelligent spider for Internet searching

As World Wide Web (WWW) based Internet services become more popular, information overload also becomes a pressing research problem. Difficulties with searching on the Internet get worse as the amount of information that is available increases. A scalable approach to support Internet search is critical to the success of Internet services and other current or future national information infrastructure (NII) applications. A new approach to build an intelligent personal spider (agent), which is based on automatic textual analysis of Internet documents, is proposed. Best first search and genetic algorithm have been tested to develop the intelligent spider. These personal spiders are able to dynamically and intelligently analyze the contents of the users' selected homepages as the starting point to search for the most relevant homepages based on the links and indexing. An intelligent spider must have the capability to make adjustments according to progress of searching in order to be an intelligent agent. However, the current searching engines do not have communication between the users and the robots. The spider presented in the paper uses Java to develop the user interface such that the users can adjust the control parameters according to the progress and observe the intermediate results. The performances of the genetic algorithm based and best first search based spiders are also reported.published_or_final_versio

Single donor ionization energies in a nanoscale CMOS channel

One consequence of the continued downwards scaling of transistors is the reliance on only a few discrete atoms to dope the channel, and random fluctuations of the number of these dopants is already a major issue in the microelectonics industry. While single-dopant signatures have been observed at low temperature, studying the impact of only one dopant up to room temperature requires extremely small lengths. Here, we show that a single arsenic dopant dramatically affects the off-state behavior of an advanced microelectronics field effect transistor (FET) at room temperature. Furthermore, the ionization energy of this dopant should be profoundly modified by the close proximity of materials with a different dielectric constant than the host semiconductor. We measure a strong enhancement, from 54meV to 108meV, of the ionization energy of an arsenic atom located near the buried oxide. This enhancement is responsible for the large current below threshold at room temperature and therefore explains the large variability in these ultra-scaled transistors. The results also suggest a path to incorporating quantum functionalities into silicon CMOS devices through manipulation of single donor orbitals

LGP2 plays a critical role in sensitizing mda-5 to activation by double-stranded RNA.

The DExD/H box RNA helicases retinoic acid-inducible gene-I (RIG-I) and melanoma differentiation associated gene-5 (mda-5) sense viral RNA in the cytoplasm of infected cells and activate signal transduction pathways that trigger the production of type I interferons (IFNs). Laboratory of genetics and physiology 2 (LGP2) is thought to influence IFN production by regulating the activity of RIG-I and mda-5, although its mechanism of action is not known and its function is controversial. Here we show that expression of LGP2 potentiates IFN induction by polyinosinic-polycytidylic acid [poly(I:C)], commonly used as a synthetic mimic of viral dsRNA, and that this is particularly significant at limited levels of the inducer. The observed enhancement is mediated through co-operation with mda-5, which depends upon LGP2 for maximal activation in response to poly(I:C). This co-operation is dependent upon dsRNA binding by LGP2, and the presence of helicase domain IV, both of which are required for LGP2 to interact with mda-5. In contrast, although RIG-I can also be activated by poly(I:C), LGP2 does not have the ability to enhance IFN induction by RIG-I, and instead acts as an inhibitor of RIG-I-dependent poly(I:C) signaling. Thus the level of LGP2 expression is a critical factor in determining the cellular sensitivity to induction by dsRNA, and this may be important for rapid activation of the IFN response at early times post-infection when the levels of inducer are low