A High-Throughput Solver for Marginalized Graph Kernels on GPU

We present the design and optimization of a linear solver on General Purpose GPUs for the efficient and high-throughput evaluation of the marginalized graph kernel between pairs of labeled graphs. The solver implements a preconditioned conjugate gradient (PCG) method to compute the solution to a generalized Laplacian equation associated with the tensor product of two graphs. To cope with the gap between the instruction throughput and the memory bandwidth of current generation GPUs, our solver forms the tensor product linear system on-the-fly without storing it in memory when performing matrix-vector dot product operations in PCG. Such on-the-fly computation is accomplished by using threads in a warp to cooperatively stream the adjacency and edge label matrices of individual graphs by small square matrix blocks called tiles, which are then staged in registers and the shared memory for later reuse. Warps across a thread block can further share tiles via the shared memory to increase data reuse. We exploit the sparsity of the graphs hierarchically by storing only non-empty tiles using a coordinate format and nonzero elements within each tile using bitmaps. Besides, we propose a new partition-based reordering algorithm for aggregating nonzero elements of the graphs into fewer but denser tiles to improve the efficiency of the sparse format.We carry out extensive theoretical analyses on the graph tensor product primitives for tiles of various density and evaluate their performance on synthetic and real-world datasets. Our solver delivers three to four orders of magnitude speedup over existing CPU-based solvers such as GraKeL and GraphKernels. The capability of the solver enables kernel-based learning tasks at unprecedented scales

Charge confinement and Klein tunneling from doping graphene

In the present work, we investigate how structural defects in graphene can change its transport properties. In particular, we show that breaking of the sublattice symmetry in a graphene monolayer overcomes the Klein effect, leading to confined states of massless Dirac fermions. Experimentally, this corresponds to chemical bonding of foreign atoms to carbon atoms, which attach themselves to preferential positions on one of the two sublattices. In addition, we consider the scattering off a tensor barrier, which describes the rotation of the honeycomb cells of a given region around an axis perpendicular to the graphene layer. We demonstrate that in this case the intervalley mixing between the Dirac points emerges, and that Klein tunneling occurs.Comment: 11 pages, 5 figure

Local maximizers of generalized convex vector-valued functions

Any local maximizer of an explicitly quasiconvex real-valued function is actually a global minimizer, if it belongs to the intrinsic core of the function's domain. In this paper we show that similar properties hold for componentwise explicitly quasiconvex vector-valued functions, with respect to the concepts of ideal, strong and weak optimality. We illustrate these results in the particular framework of linear fractional multicriteria optimization problems.Any local maximizer of an explicitly quasiconvex real-valued function is actually a global minimizer, if it belongs to the intrinsic core of the function's domain. In this paper we show that similar properties hold for componentwise explicitly quasiconvex vector-valued functions, with respect to the concepts of ideal, strong and weak optimality. We illustrate these results in the particular framework of linear fractional multicriteria optimization problems

Spatial Evolutionary Generative Adversarial Networks

Generative adversary networks (GANs) suffer from training pathologies such as instability and mode collapse. These pathologies mainly arise from a lack of diversity in their adversarial interactions. Evolutionary generative adversarial networks apply the principles of evolutionary computation to mitigate these problems. We hybridize two of these approaches that promote training diversity. One, E-GAN, at each batch, injects mutation diversity by training the (replicated) generator with three independent objective functions then selecting the resulting best performing generator for the next batch. The other, Lipizzaner, injects population diversity by training a two-dimensional grid of GANs with a distributed evolutionary algorithm that includes neighbor exchanges of additional training adversaries, performance based selection and population-based hyper-parameter tuning. We propose to combine mutation and population approaches to diversity improvement. We contribute a superior evolutionary GANs training method, Mustangs, that eliminates the single loss function used across Lipizzaner's grid. Instead, each training round, a loss function is selected with equal probability, from among the three E-GAN uses. Experimental analyses on standard benchmarks, MNIST and CelebA, demonstrate that Mustangs provides a statistically faster training method resulting in more accurate networks

Механизмы внутристентового рестеноза анализируемые путём коронарной ангиографии и внутрикоронарной ультрасонографии

Although the coronary angiography remains a proven method of in-stent restenosis assessment, intracoronary ultrasound (IVUS) is underlined as a method of better coronary lesion indices evaluation. This study was aimed as an attempt at relevant in-stent restenosis mechanisms estimation via concomitant using of IVUS and coronary angiography. These exams were applied to 47 patients having 54 bare metallic and eluting stents. Obtained results indicated different mechanisms of restenosis development in bare metallic and eluting stents. The neointima hyperplasia and negative artery remodeling in metallic stent restenosis are more expressed. Likewise, the IVUS method appears as a feasible tool of the coronary plaque area determination and guiding of stent implantation during angioplasty. The last aspect is especially important in the case of coronary artery diameter less than 3 mm.Хотя коронарная ангиография продолжает оставаться апробированным методом выявления внутристентового рестеноза, внутрикоронарная ультрасонография (IVUS) выделяется как метод лучшего определения показателей коронарных поражений. С целью анализа механизмов развития рестеноза эти два метода были использованы на 47 больных, имеющих 54 имплантированных металлических и фармакологических стентов. Полученные данные показывают наличие различных механизмов развития рестеноза металлических и фармакологических стентов. Гиперплазия неоинтимы и негативное ремоделирование артерии более выражены в металлических стентах. Метод IVUS представляется достоверным способом определения размеров коронарной бляшки и контроля имплантации стента, особенно, когда диаметр коронарной артерии меньше 3 мм

KrP laser CVD of chromium oxide by photodissociation of Cr(CO)(6)

This work reports on the synthesis of chromium oxide thin films prepared by photodissociation of Cr(CO)(6) in an oxidizing atmosphere, using a pulsed UV laser (KrF, lambda = 248 nm). The experimental conditions, which should enable the synthesis of CrO2, are discussed and results on the deposition of CrxOy films on Al2O3 (0001) substrates are presented

Intracoronary optical coherence tomography

The cardiovascular departments of the hospital of Holy Pope Giovanni XXIII in Bergamo, Italy and of the Institute of Cardiology in Chisinau, the Republic of Moldova have a fruitful history of collaboration in the field of interventional cardiology and intracoronary imaging in particular. We have recently expanded our collaboration by adding the method of Optical Coherence Tomography (OCT) into the armamentarium of imaging in the catheterization laboratory. OCT is an innovative, real time, tomographic imaging modality able to visualize tissues at microstructure level. It delivers the rays of near-infrared light through the wall of the coronary artery using small diameter optical fibres. The light that illuminates the vessel is absorbed and backscattered or reflected by the structures of the tissues with different degrees of density, thus creating an image with an axial resolution of 10-20 µm. This technology allows acquiring high definition images of long segments of coronaries for a few seconds. For the time being, OCT is mainly used in the researches, providing insights into the pathophysiology of the atherosclerotic plaque and the vascular response to stenting. It also has a potential for clinical application, such as pre-interventional evaluation of coronary arteries, procedures guidance and follow-up assessment of vascular healing after the stent implantation. A joined database has been created by the two institutions in an effort to study in vivo the morphology of the coronary arteries in different pathologies. This review is focused on the potential fields of application of OCT in different clinical and scientific institutions

In-stent restenosis in the drug eluting stent assayed by optical coherence tomography

Hospital of Holy Pope Giovanni XXIII, Bergamo, Italy, Department of Interventional Cardiology, Institute of Cardiology, Chisinau, the Republic of MoldovaBackground: In order to study the mechanisms and morphological aspects of the in-stent restenosis (ISR) have been evaluated restenosis lesions referred to drug eluting stent (DES) of the first generation using optical coherence tomography technique (OCT). Material and methods: The study underwent 39 patients with ISR induced recurrent angina or acute coronary syndrome including 66 stents from which were: 44 stents (28 patients) of the first generation of DES (19 – Cypher TM and 23 – Taxus®), and 22 stents (11 patients) of the second DES generation (9 Xience TM 2 Promus TM), 10 ZES (Resolute TM), and one stent Nobori TM. Has been made quantitative and morphological analysis of tissue pattern of ISR using the following OCT criteria: 1) morphologically homogenous neointima; 2)morphologically heterogeneous neointima; and 3) neoatherosclerosis. Results: It has been established that in the first generation of DES morphological homogenous pattern was present in both ISR developed after 1 year and later. However, the optical aspect with heterogeneous presentation had a prevalence decline in dynamics. The heterogeneous model had a higher prevalence in actual generation of DES in both incipient (< 1 year) and late presentation. Conclusions: The phenomenon of neoatherosclerosis has presented a significantly less frequency in the late restenosis of actual generation of DES. Our results suggest that restenosis phenomenon in actual generation of DES has a different morphological and evolution pattern in time in comparison with ISR of the first generation of DES

LOCATION ATTRIBUTES OF EMERGING ECONOMIES: AN ANALYSIS USING PRINCIPAL COMPONENTS

Our paper investigates the location attributes of a large sample of emerging economies from the perspective of foreign direct investments and multinational companies presence abroad. We use several macroeconomic variables that take into account the relevant location attributes for the decision of multinational companies to invest abroad and include them in a Principal Components Analysis to reveal the most relevant locational attributes or combination of such attributes that influence the decision of multinational companies to invest abroad. We find that only four variables had the most important contributions to the principal components: GDP per capita, international reserves, mobile phones subscriptions and labour force. Labour force is the variable that contributes the most to the first factor and its contribution grows in importance as we depart from 1994. At the same time GDP per capita has become less important in recent years