Fiber-optical analogue of the event horizon

The physics at the event horizon resembles the behavior of waves in moving media. Horizons are formed where the local speed of the medium exceeds the wave velocity. We use ultrashort pulses in microstructured optical fibers to demonstrate the formation of an artificial event horizon in optics. We observed a classical optical effect, the blue-shifting of light at a white-hole horizon. We also show by theoretical calculations that such a system is capable of probing the quantum effects of horizons, in particular Hawking radiation.Comment: MEDIA EMBARGO. This paper is subject to the media embargo of Scienc

Distance-generalized Core Decomposition

The $k$-core of a graph is defined as the maximal subgraph in which every vertex is connected to at least $k$ other vertices within that subgraph. In this work we introduce a distance-based generalization of the notion of $k$-core, which we refer to as the $(k,h)$-core, i.e., the maximal subgraph in which every vertex has at least $k$ other vertices at distance $\leq h$ within that subgraph. We study the properties of the $(k,h)$-core showing that it preserves many of the nice features of the classic core decomposition (e.g., its connection with the notion of distance-generalized chromatic number) and it preserves its usefulness to speed-up or approximate distance-generalized notions of dense structures, such as $h$-club. Computing the distance-generalized core decomposition over large networks is intrinsically complex. However, by exploiting clever upper and lower bounds we can partition the computation in a set of totally independent subcomputations, opening the door to top-down exploration and to multithreading, and thus achieving an efficient algorithm

Dielectric resonances of ordered passive arrays

The electrical and optical properties of ordered passive arrays, constituted of inductive and capacitive components, are usually deduced from Kirchhoff's rules. Under the assumption of periodic boundary conditions, comparable results may be obtained via an approach employing transfer matrices. In particular, resonances in the dielectric spectrum are demonstrated to occur if all eigenvalues of the transfer matrix of the entire array are unity. The latter condition, which is shown to be equivalent to the habitual definition of a resonance in impedance for an array between electrodes, allows for a convenient and accurate determination of the resonance frequencies, and may thus be used as a tool for the design of materials with a specific dielectric response. For the opposite case of linear arrays in a large network, where periodic boundary condition do not apply, several asymptotic properties are derived. Throughout the article, the derived analytic results are compared to numerical models, based on either Exact Numerical Renormalisation or the spectral method.Comment: 12 pages, 12 figure

Sustainable farming with native rocks: the transition without revolution.

The development process which humanity passed through favored a series of conquests, reflected in the better quality of life and longevity, however, it also provoked upsets and severe transformation in the environment and in the human food security. Such process is driving the ecosystems to be homogeneous, and, therefore,the nutrients� supply, via nourishment. To change this panorama, the present work discusses the gains of incorporating the stonemeal technique as a strategic alternative to give back the essential fertile characteristics to the soils. This technology has the function of facilitating the rejuvenation of the soils and increasing the availability of the necessary nutrients to the full development of the plants which is a basic input for the proliferation of life in all its dimensions

A family of thermostable fungal cellulases created by structure-guided recombination

SCHEMA structure-guided recombination of 3 fungal class II cellobiohydrolases (CBH II cellulases) has yielded a collection of highly thermostable CBH II chimeras. Twenty-three of 48 genes sampled from the 6,561 possible chimeric sequences were secreted by the Saccharomyces cerevisiae heterologous host in catalytically active form. Five of these chimeras have half-lives of thermal inactivation at 63°C that are greater than the most stable parent, CBH II enzyme from the thermophilic fungus Humicola insolens, which suggests that this chimera collection contains hundreds of highly stable cellulases. Twenty-five new sequences were designed based on mathematical modeling of the thermostabilities for the first set of chimeras. Ten of these sequences were expressed in active form; all 10 retained more activity than H. insolens CBH II after incubation at 63°C. The total of 15 validated thermostable CBH II enzymes have high sequence diversity, differing from their closest natural homologs at up to 63 amino acid positions. Selected purified thermostable chimeras hydrolyzed phosphoric acid swollen cellulose at temperatures 7 to 15°C higher than the parent enzymes. These chimeras also hydrolyzed as much or more cellulose than the parent CBH II enzymes in long-time cellulose hydrolysis assays and had pH/activity profiles as broad, or broader than, the parent enzymes. Generating this group of diverse, thermostable fungal CBH II chimeras is the first step in building an inventory of stable cellulases from which optimized enzyme mixtures for biomass conversion can be formulated

Measuring hadron properties at finite temperature

We estimate the numbers and mass spectra of observed lepton and kaon pairs produced from $\phi$ meson decays in the central rapidity region of an Au+Au collision at lab energy 11.6 GeV/nucleon. The following effects are considered: possible mass shifts, thermal broadening due to collisions with hadronic resonances, and superheating of the resonance gas. Changes in the dilepton mass spectrum may be seen, but changes in the dikaon spectrum are too small to be detectable.Comment: 9 pages (revtex), 3 figures (uuencoded postscript

Calidad microbiológica de una fórmula enteral lista para usar

Indexación: ScieloTo determinate and compare the microbiological quality of a ready to use enteral formula (EF): liquid ADN™ during different periods of time. Methods: The study was developed in the Hospital formula-preparing room. Twenty liters of EF were delivered in 40 plastic sterile bottles using aseptic technique, and were maintained at room temperature during 24 hours. Feed samples of 50 ml at time 0 and at 24 hours were obtained and frozen at _70º C, until they were investigated (40 feed samples of EF were cultivated at preparation time 0, and 24 hours). Mesophile count (Me), total coliform (TC) and faecal coliform (FC) bacteria were investigated. The feed samples were analized at the Microbiologic Laboratory of CESMEC. The microbial quality standards (MQS) were at time 0: < 10² UFC/ml of (Me), and no (TC) and (FC). At 24 hours: < 10³ UFC/ml of (Me), < 10 UFC/ml of (TC) and no (FC).The statistical data analysis was done using Stata program and Z test was used for proportions. The level of p < 0,05 was considered statistically significant. Results: The average of fulfilment (MQS) for liquid ADN™ at time 0, and 24 hours was 100% and 95% (p = 0,3) for Me. TC got 100% fulfilment (MQS) at any time. FC were not detected at any time. Conclusions: Liquid ADN™can be hung during 24 hours at room temperature.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-10182004000400005&nrm=is

Seasonal and interannual variability of cladoceran communities in two peri-alpine lakes: uncoupled response to the 2003 heat wave

Seasonal and interannual dynamics of cladoceran species were analyzed during the period 1995–2003 in two deep peri-alpine lakes morphologically different but subjected to similar regional climatic forcing. The seasonal succession of cladoceran species was characterized and the impact of extreme climatic events on the annual pattern of species succession was assessed. Using a multivariate method, we show that the cladoceran species display marked seasonality patterns that differed in the two lakes. The differences observed between the lakes were driven by their trophic state, the plankton species composition and the abundance of predators. We show that the sensitivity of the annual pattern of species succession to extreme weather changes, illustrated by the 2003 heat wave, differs markedly in these two lakes. In Lake Annecy, the annual pattern of cladoceran succession observed in 2003 is not different from the one usually observed. In contrast, in Lake Geneva, the annual pattern recorded in 2003 is unusual and characterized by the maintenance of herbivorous cladocera during summer. These findings underline the need to consider the morphology of lakes and trophic state in the assessment of ecological responses to global warming. Our results contribute to the debate about the predictability of the impacts of climate change on aquatic ecosystems, and their extrapolation from one site to another

POPLMark reloaded: Mechanizing proofs by logical relations

We propose a new collection of benchmark problems in mechanizing the metatheory of programming languages, in order to compare and push the state of the art of proof assistants. In particular, we focus on proofs using logical relations (LRs) and propose establishing strong normalization of a simply typed calculus with a proof by Kripke-style LRs as a benchmark. We give a modern view of this well-understood problem by formulating our LR on well-typed terms. Using this case study, we share some of the lessons learned tackling this problem in different dependently typed proof environments. In particular, we consider the mechanization in Beluga, a proof environment that supports higher-order abstract syntax encodings and contrast it to the development and strategies used in general-purpose proof assistants such as Coq and Agda. The goal of this paper is to engage the community in discussions on what support in proof environments is needed to truly bring mechanized metatheory to the masses and engage said community in the crafting of future benchmarks

Noise in laser speckle correlation and imaging techniques

We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera. We show that the noise scales as 1/N in all cases and that it is sensitive to correlations of signals corresponding to adjacent pixels as well as to the effective time averaging (due to the finite sampling time) and spatial averaging (due to the finite pixel size). Our results provide a guide to estimation of noise level in such applications as the multi-speckle dynamic light scattering, time-resolved correlation spectroscopy, speckle visibility spectroscopy, laser speckle imaging etc.Comment: submitted 14 May 201