Optimal construction of compressed indexes for highly repetitive texts

We propose algorithms that, given the input string of length n over integer alphabet of size σ, construct the Burrows–Wheeler transform (BWT), the permuted longest-common-prefix (PLCP) array, and the LZ77 parsing in O(n/ logσ n + r polylog n) time and working space, where r is the number of runs in the BWT of the input. These are the essential components of many compressed indexes such as compressed suffix tree, FM-index, and grammar and LZ77-based indexes, but also find numerous applications in sequence analysis and data compression. The value of r is a common measure of repetitiveness that is significantly smaller than n if the string is highly repetitive. Since just accessing every symbol of the string requires Ω(n/ logσ n) time, the presented algorithms are time and space optimal for inputs satisfying the assumption n/r ∈ Ω(polylog n) on the repetitiveness. For such inputs our result improves upon the currently fastest general algorithms of Belazzougui (STOC 2014) and Munro et al. (SODA 2017) which run in O(n) time and use O(n/ logσ n) working space. We also show how to use our techniques to obtain optimal solutions on highly repetitive data for other fundamental string processing problems such as: Lyndon factorization, construction of run-length compressed suffix arrays, and some classical “textbook” problems such as computing the longest substring occurring at least some fixed number of times. Copyright © 2019 by SIAMPeer reviewe

Improved superlensing in two-dimensional photonic crystals with a basis

We study propagation of light in square and hexagonal two-dimensional photonic crystals. We show, that slabs of these crystals focus light with subwavelength resolution. We propose a systematic way to increase this resolution, at an essentially fixed frequency, by employing a hierarchy of crystals of the same structure, and the same lattice constant, but with an increasingly complex basis.Comment: 16 Pages, 5 Figure

High-frequency dielectric spectroscopy of batio3 core - silica shell nanocomposites: Problem of interdiffusion

Three types of BaTiO3 core - amorphous nano-shell composite ceramics were processed from the same core-shell powder by standard sintering, spark-plasma sintering and two-step sintering techniques and characterized by XRD, HRSEM and broad-band dielectric spectroscopy in the frequency range 10^3 - 10^13 Hz including the THz and IR range. The samples differed by porosity and by the amount of interdiffusion from the cores to shells, in correlation with their increasing porosity. The dielectric spectra were also calculated using suitable models based on effective medium approximation. The measurements revealed a strong dielectric dispersion below the THz range, which cannot be explained by the modeling, and whose strength was in correlation with the degree of interdiffusion. We assigned it to an effect of the interdiffusion layers, giving rise to a strong interfacial polarization. It appears that the high-frequency dielectric spectroscopy is an extremely sensitive tool for detection of any gradient layers and sample inhomogeneities even in dielectric materials with negligible conductivity

String attractors : Verification and optimization

String attractors [STOC 2018] are combinatorial objects recently introduced to unify all known dictionary compression techniques in a single theory. A set γ ⊆ [1.n] is a k-attractor for a string S ∈ Σn if and only if every distinct substring of S of length at most k has an occurrence crossing at least one of the positions in γ. Finding the smallest k-attractor is NP-hard for k ≥ 3, but polylogarithmic approximations can be found using reductions from dictionary compressors. It is easy to reduce the k-attractor problem to a set-cover instance where the string's positions are interpreted as sets of substrings. The main result of this paper is a much more powerful reduction based on the truncated suffix tree. Our new characterization of the problem leads to more efficient algorithms for string attractors: we show how to check the validity and minimality of a k-attractor in near-optimal time and how to quickly compute exact solutions. For example, we prove that a minimum 3-attractor can be found in O(n) time when |Σ| ∈ O(3+ϵ√log n) for some constant ϵ > 0, despite the problem being NP-hard for large Σ. © Dominik Kempa, Alberto Policriti, Nicola Prezza, and Eva Rotenberg.Peer reviewe

Magnetothermal Conductivity of Highly Oriented Pyrolytic Graphite in the Quantum Limit

We report on the magnetic field (0T$\le B \le 9$T) dependence of the longitudinal thermal conductivity $\kappa(T,B)$ of highly oriented pyrolytic graphite in the temperature range 5 K $\le T\le$ 20 K for fields parallel to the $c-$axis. We show that $\kappa(T,B)$ shows large oscillations in the high-field region (B > 2 T) where clear signs of the Quantum-Hall effect are observed in the Hall resistance. With the measured longitudinal electrical resistivity we show that the Wiedemann-Franz law is violated in the high-field regime.Comment: 4 Figures, to be published in Physical Review B (2003

Selective transport of neurotransmitters and modulators by distinct volume-regulated LRRC8 anion channels

In response to swelling, mammalian cells release chloride and organic osmolytes through VRAC volume-regulated anion channels. VRACs are heteromers of LRRC8A and other LRRC8 isoforms (B-E) which are co-expressed in HEK293 and most other cells. The spectrum of VRAC substrates and its dependence on particular LRRC8 isoforms remains largely unknown. We show that besides the osmolytes taurine and myo-inositol, LRRC8 channels transport the neurotransmitters glutamate, aspartate and GABA and the co-activator D-serine. HEK293 cells engineered to express defined subsets of LRRC8 isoforms were used to elucidate the subunit-dependence of transport. Whereas LRRC8D was crucial for the translocation of overall neutral compounds like myo-inositol, taurine and GABA and sustained the transport of positively charged lysine, flux of negatively charged aspartate was equally well supported by LRRC8E. Disruption of LRRC8B or LRRC8C failed to decrease transport rates of all investigated substrates, but their inclusion into LRRC8 heteromers influenced VRAC's substrate preference. This suggested that individual VRACs can contain three or more different LRRC8 subunits, a conclusion confirmed by sequential co-immunoprecipitations. Our work suggests a composition-dependent role of VRACs in extracellular signal transduction

Strong exciton-plasmon coupling in semiconducting carbon nanotubes

We study theoretically the interactions of excitonic states with surface electromagnetic modes of small-diameter (~1 nm) semiconducting single-walled carbon nanotubes. We show that these interactions can result in strong exciton-surface-plasmon coupling. The exciton absorption line shape exhibits Rabi splitting ~0.1 eV as the exciton energy is tuned to the nearest interband surface plasmon resonance of the nanotube. We also show that the quantum confined Stark effect may be used as a tool to control the exciton binding energy and the nanotube band gap in carbon nanotubes in order, e.g., to bring the exciton total energy in resonance with the nearest interband plasmon mode. The exciton-plasmon Rabi splitting we predict here for an individual carbon nanotube is close in its magnitude to that previously reported for hybrid plasmonic nanostructures artificially fabricated of organic semiconductors on metallic films. We expect this effect to open up paths to new tunable optoelectronic device applications of semiconducting carbon nanotubes.Comment: 22 pages, 8 figures, accepted for PR

Bygging av ny E-18 over Farriseidet: Fare for forurensning av drikkevannsinntakene i Farris

Det er gjennomført beregninger og modellsimuleringer av i hvilken grad anleggsvirksomheten i forbindelse med å lage ny E-18 over Farriseidet vil kunne forurense vanninntakene til Larvik og Omegn Vannverk (LOV), og Vestfold Interkommunale Vannverk (VIV). Det er først og fremst tilgrumsing fra avrenning av sølevann (leire og boreslam) som vil være problemet, og at dette kan skape problemer for vannbehandlingen. Selve grumset er ikke giftig. Det er simulert tre scenarier, der 1) er om vannhåndteringen går etter planen, 2) vannhåndteringen går bare sånn halvveis etter planen, og 3) er et «worst case scenario» det kommer et skybrudd av en ukes varighet (400 mm) under innsjøens høstsirkulasjon under scenario 2. Det er tatt utgangspunkt i at man ikke kan akseptere mer enn 1 mg/l partikulært materiale i vanninntakene. Man få ha scenario 3 for å få så høy partikkelkonsentrasjon i vanninntaket til det nærmeste vannverket, LOV. Sannsynligheten for at dette skal skje, er imidlertid svært liten. Det ser med andre ord ut til at anleggsvirksomheten ikke vil med føre problemer for vannverkene forutsatt at man gjør vannhåndteringen slik man har beskrevet/fortalt oss forut for denne simuleringen.Statens Vegvesen Sø

Experimental Investigation of the Nature of the Knee in the Primary Cosmic Ray Energy Spectrum with the GAMMA experiment

We present preliminary results obtained by a novel difference method for the study of the nature of the knee in the energy spectrum of the primary cosmic radiation. We have applied this method to data from the GAMMA experiment in Armenia. The analysis provides evidence for the possible existence of a nearby source of primary cosmic rays in the Southern hemisphere.Comment: 17 pages, 5 figure