How generic are null spacetime singularities?

The spacetime singularities inside realistic black holes are sometimes thought to be spacelike and strong, since there is a generic class of solutions (BKL) to Einsteins equations with these properties. We show that null, weak singularities are also generic, in the following sense: there is a class of vacuum solutions containing null, weak singularities, depending on 8 arbitrary (up to some inequalities) analytic initial functions of 3 spatial coordinates. Since 8 arbitrary functions are needed (in the gauge used here) to span the generic solution, this class can be regarded as generic

Low-Complexity LP Decoding of Nonbinary Linear Codes

Linear Programming (LP) decoding of Low-Density Parity-Check (LDPC) codes has attracted much attention in the research community in the past few years. LP decoding has been derived for binary and nonbinary linear codes. However, the most important problem with LP decoding for both binary and nonbinary linear codes is that the complexity of standard LP solvers such as the simplex algorithm remains prohibitively large for codes of moderate to large block length. To address this problem, two low-complexity LP (LCLP) decoding algorithms for binary linear codes have been proposed by Vontobel and Koetter, henceforth called the basic LCLP decoding algorithm and the subgradient LCLP decoding algorithm. In this paper, we generalize these LCLP decoding algorithms to nonbinary linear codes. The computational complexity per iteration of the proposed nonbinary LCLP decoding algorithms scales linearly with the block length of the code. A modified BCJR algorithm for efficient check-node calculations in the nonbinary basic LCLP decoding algorithm is also proposed, which has complexity linear in the check node degree. Several simulation results are presented for nonbinary LDPC codes defined over Z_4, GF(4), and GF(8) using quaternary phase-shift keying and 8-phase-shift keying, respectively, over the AWGN channel. It is shown that for some group-structured LDPC codes, the error-correcting performance of the nonbinary LCLP decoding algorithms is similar to or better than that of the min-sum decoding algorithm.Comment: To appear in IEEE Transactions on Communications, 201

Hydrogen absorption properties of amorphous (Ni0.6Nb0.4−yTay)100−xZrx membranes

Ni based amorphous materials have great potential as hydrogen purification membranes. In the present work the melt spun (Ni0.6Nb0.4−yTay)100−xZrx with y=0, 0.1 and x=20, 30 was studied. The result of X-ray diffraction spectra of the ribbons showed an amorphous nature of the alloys. Heating these ribbons below T < 400 °C, even in a hydrogen atmosphere (1−10 bar), the amorphous structure was retained. The crystallization process was characterized by differential thermal analysis and the activation energy of such process was obtained. The hydrogen absorption properties of the samples in their amorphous state were studied by the volumetric method, and the results showed that the addition of Ta did not significantly influence the absorption properties, a clear change of the hydrogen solubility was observed with the variation of the Zr content. The values of the hydrogenation enthalpy changed from ~37 kJ/mol for x=30 to ~9 kJ/mol for x=20. The analysis of the volumetric data provides the indications about the hydrogen occupation sites during hydrogenation, suggesting that at the beginning of the absorption process the deepest energy levels are occupied, while only shallower energy levels are available at higher hydrogen content, with the available interstitial sites forming a continuum of energy levels

A Collagen‐Glycosaminoglycan‐Fibrin Scaffold For Heart Valve Tissue Engineering Applications

The field of heart valve biology and tissue engineering a heart valve continue to expand. The presentatio ns at this meeting reflect the advances made in both areas due to the multi-disciplinary approach taken by many laboratories

A New Reinforced Fibrin Collagen Glycosaminoglycan Material to Resist Tissue Contraction in Heart Valves

A crosslinked, multicomponent scaffold of collagen, GAG and fibrin has been characterised for heart valve applications. Fibrin gels reinforced with a 0.75% collagen, 0.044% GAG scaffolds can resist VSMC induced contraction significantly more than fibrin-only gels, while allowing cell proliferation and maintaining excellent cell viability. This improvement in structural integrity may facilitate the use of fibrin based materials for heart valve tissue engineering

Experimentation of Electrospray Methodology with Carbon Nanotubes

The focus of the research was design, economically building, and testing of an electrospray platform which will be employed to deposit uniform coatings of carbon nanomaterials to large surfaces. Electrospray, also known as electrohydrodynamic spray or e-spray, is a liquid atomization technique that can generate fine droplets to produce coatings with a high degree of uniformity. The carbon nanotubes (CNTs) and graphene dispersions in water are particularly attractive due to their bulk processing, ease of storage, freedom for tuning the concentration, and for their potential applications in biology and aerospace. This Electrospray platform will be used to apply CNT films, with varying quantities of graphene, that will carry a charge across non-conductive surfaces to act as a de-icing element for aircraft and spacecraft structures. This platform will be utilized for coating large area of non-conductive surfaces which will carry a charge across the structure to act as a de-icing element for aircraft and spacecraft structures

Blowtooth: a provocative pervasive game for smuggling virtual drugs through real airport security

In this paper we describe a pervasive game, Blowtooth, in which players use their mobile phones to hide virtual drugs on nearby airline passengers in real airport check-in queues. After passing through airport security, the player must find and recover their drugs from the innocent bystanders, without them ever realizing they were involved in the game. The game explores the nature of pervasive game playing in environments that are not, generally, regarded as playful or “fun”. This paper describes the game’s design and implementation as well as an evaluation conducted with participants in real airports. It explores the players’ reactions to the game through questionnaire responses and in-game activity. The technologies used in Blowtooth are, intentionally, simple in order for the enjoyment of the game to be reliant more on the physical environment rather than the enabling technologies. We conclude that situating pervasive games in unexpected and challenging environments, such as international airports, may provide interesting and unique gaming experiences for players. In addition, we argue that pervasive games benefit most from using the specific features and nature of interesting real-world environments rather than focusing on the enabling technologies

Development of Electrospray for Applications of Nanomaterials

The focus of the research was design, economically building, and testing of an electrospray platform which will be employed to deposit uniform coatings of carbon nanomaterials to large surfaces. Electrospray, also known as electrohydrodynamic spray or e-spray, is a liquid atomization technique that can generate fine droplets to produce coatings with a high degree of uniformity. The carbon nanotubes (CNTs) and graphene dispersions in water are particularly attractive due to their bulk processing, ease of storage, freedom for tuning the concentration, and for their potential applications in biology and aerospace. The substrates such as polyethylene terephthalate (PET), Kapton tape, and non-metallic surfaces have been utilized for coating. The characterization methods include measurement of the roughness, the toughness of the films, scanning electron microscope for imaging, resistance, and transmittance of the films (for PET and Kapton). This platform will be utilized for coating large area of non-conductive surfaces which will carry a charge across the structure to act as a de-icing element for aircraft and spacecraft structures

Response of the Brazilian gravitational wave detector to signals from a black hole ringdown

It is assumed that a black hole can be disturbed in such a way that a ringdown gravitational wave would be generated. This ringdown waveform is well understood and is modelled as an exponentially damped sinusoid. In this work we use this kind of waveform to study the performance of the SCHENBERG gravitational wave detector. This first realistic simulation will help us to develop strategies for the signal analysis of this Brazilian detector. We calculated the signal-to-noise ratio as a function of frequency for the simulated signals and obtained results that show that SCHENBERG is expected to be sensitive enough to detect this kind of signal up to a distance of $\sim 20\mathrm{kpc}$.Comment: 5 pages, 4 figures, Amaldi 5 Conference Proceedings contribution. Submitted to Class. Quantum Gra