Generalized Shortest Path Kernel on Graphs

We consider the problem of classifying graphs using graph kernels. We define a new graph kernel, called the generalized shortest path kernel, based on the number and length of shortest paths between nodes. For our example classification problem, we consider the task of classifying random graphs from two well-known families, by the number of clusters they contain. We verify empirically that the generalized shortest path kernel outperforms the original shortest path kernel on a number of datasets. We give a theoretical analysis for explaining our experimental results. In particular, we estimate distributions of the expected feature vectors for the shortest path kernel and the generalized shortest path kernel, and we show some evidence explaining why our graph kernel outperforms the shortest path kernel for our graph classification problem.Comment: Short version presented at Discovery Science 2015 in Banf

On the Gold Standard for Security of Universal Steganography

While symmetric-key steganography is quite well understood both in the information-theoretic and in the computational setting, many fundamental questions about its public-key counterpart resist persistent attempts to solve them. The computational model for public-key steganography was proposed by von Ahn and Hopper in EUROCRYPT 2004. At TCC 2005, Backes and Cachin gave the first universal public-key stegosystem - i.e. one that works on all channels - achieving security against replayable chosen-covertext attacks (SS-RCCA) and asked whether security against non-replayable chosen-covertext attacks (SS-CCA) is achievable. Later, Hopper (ICALP 2005) provided such a stegosystem for every efficiently sampleable channel, but did not achieve universality. He posed the question whether universality and SS-CCA-security can be achieved simultaneously. No progress on this question has been achieved since more than a decade. In our work we solve Hopper's problem in a somehow complete manner: As our main positive result we design an SS-CCA-secure stegosystem that works for every memoryless channel. On the other hand, we prove that this result is the best possible in the context of universal steganography. We provide a family of 0-memoryless channels - where the already sent documents have only marginal influence on the current distribution - and prove that no SS-CCA-secure steganography for this family exists in the standard non-look-ahead model.Comment: EUROCRYPT 2018, llncs styl

Abstracts from the 20th International Symposium on Signal Transduction at the Blood-Brain Barriers

https://deepblue.lib.umich.edu/bitstream/2027.42/138963/1/12987_2017_Article_71.pd

Identification of phenomena preceding blower surge by means of pressure spectral maps

In this paper the concept of 'quasi-dynamic' pressure measurements is introduced and used in order to obtain compressor spectral maps describing the process of surge onset in a centrifugal blower. In the experimental rig pressure signals were recorded at several throttling valve positions and subjected to Fourier analysis. The results are shown in the form of contour maps with frequency on the horizontal and control valve opening on the vertical axis. The maps allow the frequencies dominating at consecutive stages of entering surge to be distinguished. Moreover, comparison of the maps, obtained at different pressure tappings allowed the point of instability onset to be determined. Research confirmed that the first disturbances appeared in the inlet recirculation zone much before the surge. The scale of the disturbances was considerable, amplitude increased about 10 times together with an immediate rise of its mean value. On the other hand, flow structure was not regular as no dominating frequency was detected. When the flow rate continued to decrease the instabilities propagated throughout the impeller towards the diffuser and certain frequency peaks appeared suggesting the formation of regular flow structures. At deep surge spectrum is dominated by one peak that is in good agreement with frequency of the corresponding Helmholtz resonator. Moreover, due to the high accuracy of the 'quasi-dynamic' method it was possible to recognise the damped forms of non-stable phenomena were present in stable working conditions

Path coupling using stopping times

We analyse the mixing time of Markov chains using path coupling with stopping times. We apply this approach to two hypergraph problems. We show that the Glauber dynamics for independent sets in a hypergraph mixes rapidly as long as the maximum degree Δ of a vertex and the minimum size m of an edge satisfy m ≥ 2Δ +1. We also state results that the Glauber dynamics for proper q-colourings of a hypergraph mixes rapidly if m ≥ 4 and q > Δ, and if m = 3 and q ≥1.65Δ. We give related results on the hardness of exact and approximate counting for both problems

Changing the electrochemical properties low-carbon steel upon absorption of hydrogen

W artykule przedstawiono ocenę podatności stali DC01 i S235 w stanie dostawy na niszczenie wodorowe. Ocenę badanych gatunków stali niskowęglowych przeprowadzono na podstawie przebiegu zmian wartości potencjałów elektrodowych oraz wartości SEM utworzonych galwanicznych ogniw wodorowych w funkcji czasu. Stwierdzono, że stal S235 w stanie dostawy wykazuje większą skłonność do niszczenia wodorowego aniżeli stal DC01.The article presents an assessment of the susceptibility of steel DC01 and S235 able to supply the destruction of hydrogen. The evaluation of the species tested low carbon steel was based on the courses of changes in the electrode potentials and SEM values of galvanic cells formed hydrogen as a function of time. It was conlluded that steel S235 in the delivery condition is more prone to hydrogen degradation than steel DC01

Green pyomelanin-mediated synthesis of gold nanoparticles: Modelling and design, physico-chemical and biological characteristics

Background: Synthesis of nanoparticles (NPs) and their incorporation in materials are amongst the most studied topics in chemistry, physics and material science. Gold NPs have applications in medicine due to their antibacterial and anticancer activities, in biomedical imaging and diagnostic test. Despite chemical synthesis of NPs are well characterized and controlled, they rely on the utilization of harsh chemical conditions and organic solvent and generate toxic residues. Therefore, greener and more sustainable alternative methods for NPs synthesis have been developed recently. These methods use microorganisms, mainly yeast or yeast cell extract. NPs synthesis with culture supernatants are most of the time the preferred method since it facilitates the purification scheme for the recovery of the NPs. Extraction of NPs, formed within the cells or cell-wall, is laborious, time-consuming and are not cost effective. The bioactivities of NPs, namely antimicrobial and anticancer, are known to be related to NPs shape, size and size distribution. Results: Herein, we reported on the green synthesis of gold nanoparticles (AuNPs) mediated by pyomelanin purified from the yeast Yarrowia lipolytica. A three levels four factorial Box-Behnken Design (BBD) was used to evaluate the influence of temperature, pH, gold salt and pyomelanin concentration on the nanoparticle size distribution. Based on the BBD, a quadratic model was established and was applied to predict the experimental parameters that yield to AuNPs with specific size. The synthesized nanoparticles with median size value of 104 nm were of nanocrystalline structure, mostly polygonal or spherical. They exhibited a high colloidal stability with zeta potential of - 28.96 mV and a moderate polydispersity index of 0.267. The absence of cytotoxicity of the AuNPs was investigated on two mammalian cell lines, namely mouse fibroblasts (NIH3T3) and human osteosarcoma cells (U2OS). Cell viability was only reduced at AuNPs concentration higher than 160 μg/mL. Moreover, they did not affect on the cell morphology. Conclusion: Our results indicate that different process parameters affect significantly nanoparticles size however with the mathematical model it is possible to define the size of AuNPs. Moreover, this melanin-based gold nanoparticles showed neither cytotoxicity effect nor altered cell morphology. © 2019 The Author(s)