Si doped and undoped chromium nitride coatings: a comparative study of physical properties

Chromium nitride and silicon doped chromium nitride thin films have been deposited by r.f. reactive magnetron sputtering. This study corresponds to the investigation of the influence of processing parameters and of the addition of silicon on the chromium nitride matrix on the properties of the produced films. The characterization of the coatings was performed by X-ray diffraction (XRD), and nano-indentation experiments. Results concerning the crystalline phases, crystal orientation/texture, crystallite size, mechanical properties and their correlations, are presented. The increase of the nitrogen partial pressure in the working atmosphere produces changes from a body-centered cubic (bcc) Cr structure, to hexagonal Cr2N, to face-centered cubic (fcc) CrN structure. The CrN crystallites evidence a fcc (111) preferred orientation. The highest hardness is achieved in a coating with dominant CrN phase (45 GPa) with a crystallite size around 18 nm. The addition of Si, in the films with CrN dominant phase, maintains the CrN (111) preferred orientation and produces changes in films hardness, depending on deposition conditions

Acessos de mandioca açucarada coletados no Nordeste paraense possuem o mesmo genótipo detectado por marcadores microssatélites.

A mandioca é encontrada na região Norte do Brasil e é usada como fonte de subsistência para muitas famílias. A mandioca açucarada ou mandiocaba, é um tipo de mandioca que armazena em suas raízes, além do amido, açúcares livres como reservas. Atualmente, vêm recebendo destaque pelo seu potencial para uso na fabricação de álcool combustível, devido ao acúmulo de glicose que pode ser convertida em etanol diretamente. Foi realizado teste para avaliar a diversidade genética de acessos de mandiocas açucaradas coletadas em diferentes locais do estado do Pará mantidos no banco de germoplasma da Embrapa Amazônia Oriental. Foi realizada a genotipagem molecular de nove acessos de mandioca açucarada e um acesso de mandioca brava com marcadores microssatélites. Para isso, foram utilizados 13 primers microssatélites e a corrida dos produtos amplificados foi realizada em géis de poliacrilamida 6%. Após a análise dos géis, foi verificado que todas as nove amostras de mandioca açucarada possuíam o mesmo genótipo, sendo verificada baixa variabilidade genética para esse grupo de mandiocas

On Deciding Local Theory Extensions via E-matching

Satisfiability Modulo Theories (SMT) solvers incorporate decision procedures for theories of data types that commonly occur in software. This makes them important tools for automating verification problems. A limitation frequently encountered is that verification problems are often not fully expressible in the theories supported natively by the solvers. Many solvers allow the specification of application-specific theories as quantified axioms, but their handling is incomplete outside of narrow special cases. In this work, we show how SMT solvers can be used to obtain complete decision procedures for local theory extensions, an important class of theories that are decidable using finite instantiation of axioms. We present an algorithm that uses E-matching to generate instances incrementally during the search, significantly reducing the number of generated instances compared to eager instantiation strategies. We have used two SMT solvers to implement this algorithm and conducted an extensive experimental evaluation on benchmarks derived from verification conditions for heap-manipulating programs. We believe that our results are of interest to both the users of SMT solvers as well as their developers

Magnetic monopole and string excitations in a two-dimensional spin ice

We study the magnetic excitations of a square lattice spin-ice recently produced in an artificial form, as an array of nanoscale magnets. Our analysis, based upon the dipolar interaction between the nanomagnetic islands, correctly reproduces the ground-state observed experimentally. In addition, we find magnetic monopole-like excitations effectively interacting by means of the usual Coulombic plus a linear confining potential, the latter being related to a string-like excitation binding the monopoles pairs, what indicates that the fractionalization of magnetic dipoles may not be so easy in two dimensions. These findings contrast this material with the three-dimensional analogue, where such monopoles experience only the Coulombic interaction. We discuss, however, two entropic effects that affect the monopole interactions: firstly, the string configurational entropy may loose the string tension and then, free magnetic monopoles should also be found in lower dimensional spin ices; secondly, in contrast to the string configurational entropy, an entropically driven Coulomb force, which increases with temperature, has the opposite effect of confining the magnetic defects.Comment: 8 pages. Accepted by Journal of Applied Physics (2009