An efficient technique of texture representation in segmentation-based image coding schemes

In segmentation-based image coding techniques the image to be compressed is first segmented. Then, the information is coded describing the shape and the interior of the regions. A new method to encode the texture obtained in segmentation-based coding schemes is presented. The approach combines 2-D linear prediction and stochastic vector quantization. To encode a texture, a linear predictor is computed first. Next, a codebook following the prediction error model is generated and the prediction error is encoded with VQ. In the decoder, the error image is decoded first and then filtered as a whole, using the prediction filter. Hence, correlation between pixels is not lost from one block to another and a good reproduction quality can be achieved.Peer ReviewedPostprint (published version

Photodegradation Mechanisms of Tetraphenyl Butadiene Coatings for Liquid Argon Detectors

We report on studies of degradation mechanisms of tetraphenyl butadiene (TPB) coatings of the type used in neutrino and dark matter liquid argon experiments. Using gas chromatography coupled to mass spectrometry we have detected the ultraviolet-blocking impurity benzophenone (BP). We monitored the drop in performance and increase of benzophenone concentration in TPB plates with exposure to ultraviolet (UV) light, and demonstrate the correlation between these two variables. Based on the presence and initially exponential increase in the concentration of benzophenone observed, we propose that TPB degradation is a free radical-mediated photooxidation reaction, which is subsequently confirmed by displaying delayed degradation using a free radical inhibitor. Finally we show that the performance of wavelength-shifting coatings of the type envisioned for the LBNE experiment can be improved by 10-20%, with significantly delayed UV degradation, by using a 20% admixture of 4-tert-Butylcatechol.Comment: 12 pages, 9 figures. Submitted to JINS

Snake Venomics and Antivenomics of Bothrops diporus, a Medically Important Pitviper in Northeastern Argentina

Snake species within genus Bothrops are responsible for more than 80% of the snakebites occurring in South America. The species that cause most envenomings in Argentina, B. diporus, is widely distributed throughout the country, but principally found in the Northeast, the region with the highest rates of snakebites. The venom proteome of this medically relevant snake was unveiled using a venomic approach. It comprises toxins belonging to fourteen protein families,be ing dominated by PI- and PIII-SVMPs, PLA2 molecules, BPP-like peptides, L-amino acid oxidase and serine proteinases. This toxin profile largely explains the characteristic pathophysiological effects of bothropic snakebites observed in patients envenomed by B. diporus. Antivenomic analysis of the SAB antivenom (Instituto Vital Brazil) against the venom of B. diporus showed that this pentabothropic antivenom efficiently recognized all the venom proteins and exhibited poor affinity towards the small peptide (BPPs and tripeptide inhibitors of PIII-SVMPs) components of the venom.Fil: Gay, Claudia Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; ArgentinaFil: Sanz, Libia. Instituto de Biomedicina de Valencia; EspañaFil: Calvete, Juan J.. Instituto de Biomedicina de Valencia; EspañaFil: Pla, Davinia. Instituto de Biomedicina de Valencia; Españ

Per la pau de les nacions : una pàgina d'història

Abstract not availabl

Statistical Analysis of Genealogical Trees for Polygamic Species

Repetitions within a given genealogical tree provides some information about the degree of consanguineity of a population. They can be analyzed with techniques usually employed in statistical physics when dealing with fixed point transformations. In particular we show that the tree features strongly depend on the fractions of males and females in the population, and also on the offspring probability distribution. We check different possibilities, some of them relevant to human groups, and compare them with simulations.Comment: 2 eps figs, Fig.2 changed to meet cond-mat size criteri

Exploring quantum chaos with a single nuclear spin

Most classical dynamical systems are chaotic. The trajectories of two identical systems prepared in infinitesimally different initial conditions diverge exponentially with time. Quantum systems, instead, exhibit quasi-periodicity due to their discrete spectrum. Nonetheless, the dynamics of quantum systems whose classical counterparts are chaotic are expected to show some features that resemble chaotic motion. Among the many controversial aspects of the quantum-classical boundary, the emergence of chaos remains among the least experimentally verified. Time-resolved observations of quantum chaotic dynamics are particularly rare, and as yet unachieved in a single particle, where the subtle interplay between chaos and quantum measurement could be explored at its deepest levels. We present here a realistic proposal to construct a chaotic driven top from the nuclear spin of a single donor atom in silicon, in the presence of a nuclear quadrupole interaction. This system is exquisitely measurable and controllable, and possesses extremely long intrinsic quantum coherence times, allowing for the observation of subtle dynamical behavior over extended periods. We show that signatures of chaos are expected to arise for experimentally realizable parameters of the system, allowing the study of the relation between quantum decoherence and classical chaos, and the observation of dynamical tunneling.Comment: revised and published versio

Seawater intrusion and coastal groundwater resources management. Examples from two Mediterranean regions: Catalonia and Sardinia

Seawater intrusion is a natural phenomenon that allows the encroachment of saline water into aquifers. Nevertheless, many human actions along the coastline, in particular groundwater withdrawal, enhance this process and finally cause the salinization of groundwater resources. Here we review the hydrogeological basis of seawater intrusion and describe specific cases in Catalonia and Sardinia, as examples of environmental problems and water management actions. We emphasize the origin of salinization and the hydrogeological details of each case, as well as the solutions that have been implemented to prevent groundwater salinization

Organized crime behavior of shell-company networks in procurement: prevention insights for policy and reform

In recent years, the analysis of economic crime and corruption in procurement has benefited from integrative studies that acknowledge the interconnected nature of the procurement ecosystem. Following this line of research, we present a networks approach for the analysis of shell-companies operations in procurement that makes use of contracting and ownership data under one framework to gain knowledge about the organized crime behavior that emerges in this setting. In this approach, ownership and management data are used to identify connected components in shell-company networks that, together with the contracting data, allows to develop an alternative representation of the traditional buyer-supplier network: the module-component bipartite network, where the modules are groups of buyers and the connected components are groups of suppliers. This is applied to two documented cases of procurement corruption in Mexico characterized by the involvement of large groups of shell-companies in the misappropriation of millions of dollars across many sectors. We quantify the economic impact of single versus connected shell-companies operations. In addition, we incorporate metrics for the diversity of operations and favoritism levels. This paper builds into the quantitative organized crime in the private sector studies and contributes by proposing a networks approach for preventing fraud and understanding the need for legal reforms.Comment: Corruption; fraud; public procurement; shell-companies; ownership; organized crime; network analysi