Electrolytic Nickel Impregnation of Porous Anodic Aluminum Oxide Films Using AC Voltage as Solar Selective Absorber

AbstractAnodized aluminum oxide films on aluminum substrates 1050 (99.5% Al) was impregnated with nickel by electrodeposition technique. In these paper, we report the synthesis of Ni using the galvanostat mode, and also some experimental modification in the frequency and voltage values, in order to optimize the amount content of Ni on aluminum substrate The data values of the total reflectance were analyzed in the visible solar spectrum and near infrared as a function of voltage, frequency and time of the impregnation process. Several experiments were performed in order to correlate these parameters with the nickel content in the bottom of the pores of the film and its reflectance properties. By morphological analysis found that samples with average nickel content of 10% of the total pore volume not exhibit good properties of a selective absorber, however the samples containing 60% of the total pore volume, present in the reflectance spectrum visible solar 5% and 90% in the infrared solar spectrum so it can be considered a good selective absorber films makes these coatings are prospects for implementation in solar collectors

Studying the benefits of using UML on software maintenance : an evidence-based approach

Including modelling as part of software development appears to have various benefits. Why then is it that not all companies use software modelling? One of the main reasons is that it requires up-front investments. From an economic point of view, any type of investment must be justified in terms of how much payback there will be at a later stage. This being the case, in the context of software projects, investment in modelling should be justified by benefits, such as improved productivity and improved product quality, which can be seen later during software development or maintenance. When such benefits are not tangible or foreseeable, modelling becomes a practice without clear added value for the system being developed. The problem, therefore, is how we can investigate and prove whether or not modelling, or some specific characteristics of modelling, provide any benefits during software development and maintenance. As long as this question remains unanswered, it will be difficult to motivate and justify modelling activities in real software projects. This thesis therefore contributes to partially answering these open questions by focusing the empirical research on the benefits of using UML modelling during software maintenance.Algorithms and the Foundations of Software technolog

Ectomicorrizas presentes en la plantación trufera “Los Quejigares” (Soria)

En este trabajo se describen las ectomicorrizas presentes en 16 plantas de Quercus ilex L. subsp. ballota (Desf.) Samp. de 22 años, de la finca de 600 ha que gestiona AROTZ-CATESA en el término municipal de Villaciervos (Soria). Además se presentan los porcentajes de micorrización de las ectomicorrizas más interesantes. Este estudio se incluye dentro del proyecto LIFE 99 ENV/E/000356 “Revalorización de bosques productores de trufa: un ejemplo de gestión sostenible”. SUMMARY: This study describes the ectomycorrhiza occurring in 16 twenty-two years old seedlings of Quercus ilex L. subsp. ballota (Desf.) Samp., in the plot of 600 ha that AROTZ-CATESA manages in of Villaciervos (Soria). Mycorrhization percentages of the most interesting ectomycorrhiza are also reported. This study is included in the project LIFE 99 ENV/E/000356 "Truffled Mediterranean forest improvement: an example of sustanaible management”

Hamiltonization of Nonholonomic Systems and the Inverse Problem of the Calculus of Variations

We introduce a method which allows one to recover the equations of motion of a class of nonholonomic systems by finding instead an unconstrained Hamiltonian system on the full phase space, and to restrict the resulting canonical equations to an appropriate submanifold of phase space. We focus first on the Lagrangian picture of the method and deduce the corresponding Hamiltonian from the Legendre transformation. We illustrate the method with several examples and we discuss its relationship to the Pontryagin maximum principle.Comment: 23 pages, accepted for publication in Rep. Math. Phy

Ectomycorrhizal status of a mature productive black truffle plantation

The truffle-plantation «Los Quejigares» was planted in 1971 by AROTZ-CATESA company. It is a 600 ha plot of Quercus ilexmycorrhizated with Tuber melanosporum at 1,250 m a.s.l. on calcareous soil. This plantation is the largest of the world and one of the eldest truffle-plantations of Spain and it is in full production. Knowledge of the mycorrhizal status of a mature black truffle plantation is significant for the improvement of truffle cultivation. Ectomycorrhizae were studied for knowing T. melanosporum persistence and diversity and abundance of other ectomycorrhizal types. Roots of 16 holmoaks were sampled, 12 trees produce truffle sporocarps and four did not. It was found a mean of about 35% of T. melanosporum ectomycorrhizae in the studied trees, being this significantly higher in the productive trees. Also, 105 more different ectomycorrhizal types were found. In spite of the high number of morphotypes found, it seems that they do not replace T. melanosporum, showing that there is a coexistence between species in the fungal community associated to the roots

Caracterización de ectomicorrizas en encinares productores de trufa negra del noreste de Soria

Black truffle sporocarp production is determined, amongst many other factors, by an optimum mycorrhization degree in the roots of the host-tree. This process is triggered in balance with other fungal species that does not inhibit its sporocarp production. So, there is an ectomycorrhizal fungal community associated with the black truffle sporocarp productive host-trees that runs as any other living beings community, producing a certain fungal biodiversity and establishing connections in dynamic balance that will evolve. The absence of black truffle sporocarps production in some host-trees will be determined by its ectomycorrhiza absence, or because between the fungal community there are one or more species that inhibit this process or displace it. With the aim of study those topics, the ectomycorrhizae present in 23 adult holmoak trees (Quercus ilex subsp. ballota (Desf.) Samp.) of seven Tuber melanosporum Vittad. productive areas in the North-West of Soria (inner Spain) are characterized and quantified. During the spring and the autumn of 1999 and 2000, black truffle productive and non-productive holmoaks were studied following the global method (Verlhac et al., 1990, La truffe guide pratique). Ectomycorrhizal types were characterized following the guidelines of Agerer (1999). Tuber melanosporum, T. aestivum Vittad., T. brumale Vittad., Cenococcum geophylum Fr., Pisolithus arrhizus (Scop.) Rauscher, Cantharellus tubaeformis (Bull.) Fr., Hebeloma cf. sinapizans (Fr.) Sacc., Tomentella galzinii Bourdot, AD type, Cortinarius sp., Hebeloma sp. and Scleroderma sp. and many others Telephorales, Tuberales and Boletales ectomycorrhizal types were found. Tuber melanosporum mycorrhizae are present both in productive and non-productive hosttrees, as it happens for T. aestivum, while T. brumale ectomycorrhizae are only present in nonproductive holmoaks. The rest of identified ectomycorrhizal types are present in productive and non-productive host-trees

Smooth Paths on Three Dimensional Lattice

A particular class of random walks with a spin factor on a three dimensional cubic lattice is studied. This three dimensional random walk model is a simple generalization of random walk for the two dimensional Ising model. All critical diffusion constants and associated critical exponents are calculated. Continuum field theories such as Klein-Gordon, Dirac and massive Chern-Simons theories are constructed near several critical points.Comment: 7 pages,NUP-A-94-

Biological validation of coenzyme Q redox state by HPLC-EC measurement: relationship between coenzyme Q redox state and coenzyme Q content in rat tissues

AbstractThe properties of coenzymes Q (CoQ9 and CoQ10) are closely linked to their redox state (CoQox/total CoQ)×100. In this work, CoQ redox state was biologically validated by high performance liquid chromatography-electrochemical measurement after modulation of mitochondrial electron flow of cultured cells by molecules increasing (rotenone, carbonyl cyanide chlorophenylhydrazone) or decreasing (antimycin) CoQ oxidation. The tissue specificity of CoQ redox state and content were investigated in control and hypoxic rats. In control rats, there was a strong negative linear regression between tissular CoQ redox state and CoQ content. Hypoxia increased CoQ9 redox state and decreased CoQ9 content in a negative linear relationship in the different tissues, except the heart and lung. This result demonstrates that, under conditions of mitochondrial impairment, CoQ redox control is tissue-specific

A Generalization of Chaplygin's Reducibility Theorem

In this paper we study Chaplygin's Reducibility Theorem and extend its applicability to nonholonomic systems with symmetry described by the Hamilton-Poincare-d'Alembert equations in arbitrary degrees of freedom. As special cases we extract the extension of the Theorem to nonholonomic Chaplygin systems with nonabelian symmetry groups as well as Euler-Poincare-Suslov systems in arbitrary degrees of freedom. In the latter case, we also extend the Hamiltonization Theorem to nonholonomic systems which do not possess an invariant measure. Lastly, we extend previous work on conditionally variational systems using the results above. We illustrate the results through various examples of well-known nonholonomic systems.Comment: 27 pages, 3 figures, submitted to Reg. and Chaotic Dy

Vector Bin Packing with Multiple-Choice

We consider a variant of bin packing called multiple-choice vector bin packing. In this problem we are given a set of items, where each item can be selected in one of several $D$-dimensional incarnations. We are also given $T$ bin types, each with its own cost and $D$-dimensional size. Our goal is to pack the items in a set of bins of minimum overall cost. The problem is motivated by scheduling in networks with guaranteed quality of service (QoS), but due to its general formulation it has many other applications as well. We present an approximation algorithm that is guaranteed to produce a solution whose cost is about $\ln D$ times the optimum. For the running time to be polynomial we require $D=O(1)$ and $T=O(\log n)$. This extends previous results for vector bin packing, in which each item has a single incarnation and there is only one bin type. To obtain our result we also present a PTAS for the multiple-choice version of multidimensional knapsack, where we are given only one bin and the goal is to pack a maximum weight set of (incarnations of) items in that bin