A Note on Key Agreement and Non-Interactive Commitments

We observe that any key agreement protocol satisfying perfect completeness, regardless of its round complexity, can be used to construct a non-interactive commitment scheme. This observation simplifies the cryptographic assumptions required for some protocols that utilize non-interactive commitments and removes the need for ad-hoc constructions of non-interactive commitments from specific assumptions such as Learning with Errors

Detecting communities of triangles in complex networks using spectral optimization

The study of the sub-structure of complex networks is of major importance to relate topology and functionality. Many efforts have been devoted to the analysis of the modular structure of networks using the quality function known as modularity. However, generally speaking, the relation between topological modules and functional groups is still unknown, and depends on the semantic of the links. Sometimes, we know in advance that many connections are transitive and, as a consequence, triangles have a specific meaning. Here we propose the study of the modular structure of networks considering triangles as the building blocks of modules. The method generalizes the standard modularity and uses spectral optimization to find its maximum. We compare the partitions obtained with those resulting from the optimization of the standard modularity in several real networks. The results show that the information reported by the analysis of modules of triangles complements the information of the classical modularity analysis.Comment: Computer Communications (in press

A unique bacteriohopanetetrol stereoisomer of marine anammox

Anaerobic ammonium oxidation (anammox) is a major process of bioavailable nitrogen removal from marine systems. Previously, a bacteriohopanetetrol (BHT) isomer, with unknown stereochemistry, eluting later than BHT using high performance liquid chromatography (HPLC), was detected in ‘Ca. Scalindua profunda’ and proposed as a biomarker for anammox in marine paleo-environments. However, the utility of this BHT isomer as an anammox biomarker is hindered by the fact that four other, non-anammox bacteria are also known to produce a late-eluting BHT stereoisomer. The stereochemistry in Acetobacter pasteurianus, Komagataeibacter xylinus and Frankia sp. was known to be 17β, 21β(H), 22R, 32R, 33R, 34R (BHT-34R). The stereochemistry of the late-eluting BHT in Methylocella palustris was unknown. To determine if marine anammox bacteria produce a unique BHT isomer, we studied the BHT distributions and stereochemistry of known BHT isomer producers and of previously unscreened marine (‘Ca. Scalindua brodeae’) and freshwater (‘Ca. Brocadia sp.’) anammox bacteria using HPLC and gas chromatographic (GC) analysis of acetylated BHTs and ultra high performance liquid chromatography (UHPLC)-high resolution mass spectrometry (HRMS) analysis of non-acetylated BHTs. The 34R stereochemistry was confirmed for the BHT isomers in Ca. Brocadia sp. and Methylocella palustris. However, ‘Ca. Scalindua sp.’ synthesise a stereochemically distinct BHT isomer, with still unconfirmed stereochemistry (BHT-x). Only GC analysis of acetylated BHT and UHPLC analysis of non-acetylated BHT distinguished between late-eluting BHT isomers. Acetylated BHT-x and BHT-34R co-elute by HPLC. As BHT-x is currently only known to be produced by ‘Ca. Scalindua spp.’, it may be a biomarker for marine anammox

Ensaio do anel para avaliação do comportamento do coeficiente de atrito da liga de alumínio AA6351

The aim of this paper is a comparative study about the influence of lubricants on the friction coefficient of aluminum alloy AA6351. The friction has a significant effect on the deformation of the material, changing the compression strength and wear of the matrix and the piece. Choosing a lubricant able to reduce friction interface piece/matrix provides tool life gain and consequently improves the manufacturing profit margin. For the forging of aluminum alloys are recommended lubricants based on graphite and water or graphite and oil. On this study, three commercial lubricants were tested: a graphited (Aerodag G), a synthetic (Synd Forg 100-A) and an oil-based (Dechelub 5562). The methodology consists on obtaining specimens ring shaped, ring test in hydraulic press changing the lubricants, computer program simulation for the acquisition of the calibration curves and comparison of results. Comparing the experimental data with the curves obtained by simulation, we found that, among the three lubricants tested, the best performer was the synthetic, followed by oil-based lubricant. The graphite based lubricant had the worst performance. Key words: aluminum, friction, computer simulation and lubrication.O objetivo deste trabalho e realizar um estudo comparativo sobre a influencia de lubrificantes no coeficiente de atrito da liga de alumínio AA6351. O atrito tem um efeito significativo na deformação do material, alterando a forca de compressão e o desgaste da matriz e da peca. A escolha de um lubrificante com eficiência na redução do atrito da interface peca/matriz aumenta à vida útil da ferramenta e, consequentemente, melhora a margem de lucro quando em produção industrial. Para o forjamento de ligas de alumínio, recomendam-se lubrificantes à base de grafite e água ou grafite e óleo. Neste estudo, três lubrificantes comerciais foram testados: grafitado (Aerodag G), sintético (Synd Forg 100-A) e um a base de óleo (Dechelub 5562). A metodologia adotada: obtenção de corpos de prova, ensaio do anel em prensa hidráulica variando-se os lubrificantes, simulação em programa computacional para aquisição das curvas de calibração e comparação dos resultados. Comparando os dados experimentais com as curvas obtidas por simulação foi verificado que, entre os três lubrificantes testados, o sintético obteve o melhor desempenho, seguido do lubrificante à base de óleo. O lubrificante à base de grafite obteve um desempenho inferior para essa aplicação. Palavras-chave: alumínio, atrito, simulação computacional e lubrificação

Estudo do efeito da rugosidade superficial sobre o coeficiente de atrito no ensaio de compressão do anel

The evaluation of the tribological conditions, among which the friction by means of simple models are questionable because the influence of superficial roughness and strength of materials, among other factors, is not considered. This paper presents a detailed analysis on the influence of surface roughness on friction at the specimen/die interface. The studies are based on experimental data obtained by the ring compression test, which they were compared with results of simulations and the calibration curves of friction modeled in finite element software. A series of ring compression tests was performed to obtain the friction coefficient for various ranges of surface roughness of the specimen.Key words: ring compression test, surface roughness, friction coefficient, numerical simulation.A avaliação das condições tribológicas, dentre elas o atrito por meio de modelos simples é questionável porque a influência da rugosidade superficial e resistência de materiais, entre outros fatores, não é considerada. Este trabalho apresenta uma análise detalhada da influência da rugosidade superficial sobre o atrito na interface peça/matriz. Os estudos estão baseados em dados experimentais obtidos por meio do ensaio de compressão do anel, os quais foram comparados com os resultados de simulações e com as curvas de calibração de atrito modeladas em software de elementos finitos. Uma série de ensaios de compressão do anel foi realizada para obter os coeficientes de atrito para diversas faixas de rugosidade superfi cial do corpo de prova.Palavras-chave: ensaio de compressão do anel, rugosidade superficial, coeficiente de atrito, simulação numérica

The Grizzly, April 10, 2008

Baby Dies from Lack of Medical Attention, Parents Charged • Relay is Here! • Dancing at Lughnasa Opens at UC • Yes, It\u27s a Positions Article • Airband\u27s 25th Raises $3100 for the Laurel House • Senior\u27s Helpful Hints for Class Registration • Glancing at the Future of Collegeville • Men\u27s Golf Swings into Season • Track Teams Win Goucher Classichttps://digitalcommons.ursinus.edu/grizzlynews/1761/thumbnail.jp

The Grizzly, April 24, 2008

Ursinus College Dance Company Kicks Off Tonight! • CoSA at UC! • Charity Events in the Classroom • Red Sky in Morning • Another Collegeville Restaurant Review: BonJung • Ursinus Graduate Awarded Watson Fellowship • Achievement Gap: Close to Home • Opinions: Bush / Clinton Dynasty? • Weekend Success and Dubb Appreciation Week • UC Softball Flying High After Wins Against Gettysburg • Great Success Strikes Men\u27s Laxhttps://digitalcommons.ursinus.edu/grizzlynews/1763/thumbnail.jp