V1 non-linear properties emerge from local-to-global non-linear ICA

It has been argued that the aim of non-linearities in different visual and auditory mechanisms may be to remove the relations between the coefficients of the signal after global linear ICA-like stages. Specifically, in Schwartz and Simoncelli (2001), it was shown that masking effects are reproduced by fitting the parameters of a particular non-linearity in order to remove the dependencies between the energy of wavelet coefficients. In this work, we present a different result that supports the same efficient encoding hypothesis. However, this result is more general because, instead of assuming any specific functional form for the non-linearity, we show that by using an unconstrained approach, masking-like behavior emerges directly from natural images. This result is an additional indication that Barlow's efficient encoding hypothesis may explain not only the shape of receptive fields of V1 sensors but also their non-linear behavior.     

Variation of the lipids and fatty acids in marine shrimps consumed in Venezuela

There are three marine shrimp species in the Venezuelan internal market, two of them are native species, from fisheries, Farfantapenaeus brasiliensis and Litopenaeus schmitti, and one is an exotic species and farmed, L. vannamei. The objectives of this paper were to determine the possible variation of lipid content and fatty acid composition of these species, even under different culture conditions (e.g. feed used). The lipid content in all the species are higher (5 to 10 times) that the data from previous papers deal with marine shrimps, ranged from 4.8 to 10.9%, suggesting that its impact in the human health should be reviewed. At the same time, there were detected differences between the lipid content and fatty acids composition of the species. Wild L. schmitti had the highest lipid content (10.9%), following by wild F. brasiliensis (9.0%), cultured L. schmitti (4.8% to 7.1%) and cultured L. vannamei (5.1% to 6.2%). On the other hand, L. schmitti fed on commercial feed had the highest proportion of EPA and/or DHA, following by L. vannamei fed on the experimental feed, wild L. schmitti and fed with the experimental feed and wild F. brasiliensis.     

Contribution to the hydrothermal synthesis of zeolite beta and its modifications with gallium

The zeolite beta is a crystalline synthetic aluminosilicate with wide-pore size (6 to 9 Å) and a Si/Al ratio from 5 to 100. In this study, we have investigated the influence of several synthesis parameters on the physicochemical properties of the materials. The synthesis of zeolite beta has been performed by hydrothermal method, the aluminum source and gallium content in the structure being variable. The structural characterization was carried out by means of X-ray diffraction, SEM and ²⁷Al and ⁷¹Ga MAS NMR spectroscopy. When the aluminum sulfate is used as aluminium source, zeolite beta with higher crystallinity is generated. All the samples showed a XRD pattern similar to crystalline zeolite beta and the ²⁷Al and ⁷¹Ga MAS NMR spectrum demonstrated that the incorporation of both heteroatoms was efficient.     

Mechanical behavior of glass fiber-reinforced Nylon-6 syntactic foams and its Young's modulus numerical study

Glass fiber-reinforced Nylon-6 syntactic foams (GRSF) were fabricated by melt mixing, adding silane-modified hollow glass microspheres (HGMf) at 5, 10, 15, and 20 wt% and an impact modifier at 15 wt. Tensile test results showed that the foam's strength increased with the addition of HGMs but started to decrease when the volume fraction of the spheres was higher than 18 vol% (10 wt%). To elucidate the reinforcement mechanism, a numerical simulation of GRSF was carried out. It revealed that HGMs progressively become the reinforcement phase of GRSFs, as their volume fraction increased due to the load transfer occurring more readily in the HGMs than the fiber, which is expected to be the reinforcement. Hence, for a desired weight-strength ratio, thicker walls are necessary to delay the elastic relaxation of the microspheres and the impairing of the composite as a whole in the context of strength. HGMs with relative wall thickness τ = 0.04 produce an impairing on Young's modulus, if the volume fraction of microspheres is exceeded than 18 vol% because the microspheres are not able to endure increased loads. In addition, a significant reduction of the density was observed by up to 12% in the GRSFs with 30 wt% of both fibers and HGMs. The insight gained of GRSFs role and the numerical simulation achieved through this work, is a significant step toward developing applications of these lightweight materials, since they show good combination of strength, toughness, density, and thermal insulation performance, which can be useful in the automotive, aeronautical and sports industries.     

Electrical and Magnetic Properties of NiZn Ferrite Prepared by Conventional and Solar Sintering

The electrical properties of polycrystalline NiZn ferrite, Zn_0.44Ni_0.38Fe_2.18O₄, were investigated by impedance spectroscopy over the frequency and temperature ranges, 5 Hz to 2 MHz and 10–600 K and by magnetic permeability measurements at room temperature. Samples were sintered in either conventional or solar furnaces followed by quenching or slow cooling to ambient temperature. Depending on processing conditions, the room‐temperature electrical resistivity of conventionally sintered samples varied by seven orders of magnitude, from 5 ohm cm for a sample quenched from 1250°C to 10 Mohm cm for a sample quenched from 400°C. These differences were attributed to variations in oxygen content of the ferrite which decreased with increasing quench temperature. Oxygen deficiency led to mixed valence of Fe in the octahedral B sites of the spinel structure and was responsible for high electronic conductivity with low activation energy at low temperatures in oxygen‐deficient samples. By contrast, in oxygen‐stoichiometric samples, Fe on the tetrahedral A sites was believed to be divalent and Fe on the octahedral B sites to be entirely trivalent. Electron hopping between A and B sites had much higher activation energy and dominated the conductivity at high temperature for all samples. Samples sintered in the solar furnace were much more conductive than ones that were slow‐cooled after conventional sintering and this is attributed to the relatively rapid cooling rate after exposure in the solar furnace, which preserved some of the oxygen deficiency present at high temperature. For the same reason, samples that were slow cooled in N₂ were also much more conductive. Solar‐sintered samples with higher density (96%) had higher real permeability than slow‐cooled, conventionally sintered ones (86%) mainly due to a combination of their lower resistivity and higher density. Resistivity seems to have a greater correlation with the imaginary permeability than density has.     

Acetylated Trivalent Mannobioses: Chemical Modification,Structural Elucidation,and Biological Evaluation

People suffering from allergies can be treated with repeated injections of increasing amounts of a specific allergen. This type of specific immunotherapy is currently the only way to treat the underlying pathological immune response associated with an allergy. The approach can afford long‐lasting protection, but the process takes 3–5 years, can produce allergic reactions, and in severe cases treatment is often aborted due to anaphylaxis. However, treatment can be optimized with the use of specific adjuvants that modify the immune response, its duration, and that increase the production of the correct type of antibodies. In the pursuit of such adjuvants, two new trivalent acetylated β‐(1→2)‐linked mannobioses based on a previously discovered lead molecule were prepared. The new molecules, along with the previously developed lead, were investigated by rigorous NMR and molecular modeling experiments in order to elucidate their behavior and preferred conformations in solution. Furthermore, the molecules were subjected to a biological investigation in which their immunostimulatory properties were evaluated by assessing their effect on the production of T_H2‐type cytokine interleukin‐4 (IL‐4) and T_reg pro‐inflammatory cytokine tumor necrosis factor (TNF). Treatment of peripheral mononuclear blood cell cultures from patients suffering from birch allergy with birch allergen Bet v induced a strong IL‐4 response, whereas the same treatment together with the trivalent acetylated mannobioses caused significant suppression of the induced IL‐4.     

Fuzzy approach to the intelligent management of virtual spaces.

This paper presents research carried out toward the improvement of current virtual environments from an intelligent systems approach. A novel architecture to solve vague queries that allows users to find objects and scenes in virtual environments is described. As a base, a new virtual worlds representation model and an associated fuzzy querying approach are used. The new representation model adds a semantic level to the usual models, providing more suitable environments for the interaction with users. The query solver is able to work with queries expressing the vagueness inherent to human conceptualization of visual perception (for example, tall tree, a park with many tall trees, or a park bench near approximately five tall trees). The system has been developed and evaluated with user experiments, where comparison with navigation and keyword-based query approaches have been realized. The results of this study show that the proposed architecture is more powerful and intuitive for finding the targets.     

Programming Grid Applications with GRID Superscalar

The aim of GRID superscalar is to reduce the development complexity of Grid applications to the minimum, in such a way that writing an application for a computational Grid may be as easy as writing a sequential application. Our assumption is that Grid applications would be in a lot of cases composed of tasks, most of them repetitive. The granularity of these tasks will be of the level of simulations or programs, and the data objects will be files. GRID superscalar allows application developers to write their application in a sequential fashion. The requirements to run that sequential application in a computational Grid are the specification of the interface of the tasks that should be run in the Grid, and, at some points, calls to the GRID superscalar interface functions and link with the run-time library.GRID superscalar provides an underlying run-time that is able to detect the inherent parallelism of the sequential application and performs concurrent task submission. In addition to a data-dependence analysis based on those input/output task parameters which are files, techniques such as file renaming and file locality are applied to increase the application performance. This paper presents the current GRID superscalar prototype based on Globus Toolkit 2.x, together with examples and performance evaluation of some benchmarks.