Ultrastructural characteristics of spermatogenesis in Pallas's mastiff bat, Molossus molossus (Chiroptera: Molossidae)

Despite the large number of species, their wide distribution, and unique reproductive characteristics, Neotropical bats have been poorly studied, and important aspects of the reproduction of these animals have not been elucidated. We made an ultrastructural analysis of spermatogenesis in Molossus molossus (Molossidae). The process of spermatogonial differentiation is similar to that found in other bats and is also relatively similar to that of Primates, with three main spermatogonia types: A(d), A(p), and B. Meiotic divisions proceed similarly to those of most mammals, and spermiogenesis is clearly divided into 12 steps, in the middle of the range known for bats (9-16 steps). Formation of the acrosome is similar to that known from other mammals; however, the ultrastructure of spermatozoa was found to have unique characteristics, including many wavy acrosomal projections on its surface, which seems to be specific for the family Molossidae. Comparing the ultrastructure of the spermatozoon of M. molossus with other bats already study, we observed that three characters vary: morphology of the outer dense fibers, of the perforatorium, and of the spermatozoon head. The great similarity of morphological characters between M. molossus and Platyrrhinus lineatus suggests that M. molossus is more closely related to the Phyllostomidae than to the Rhinolophidae and the Vespertilionidae.     

Improved Accuracy of the Inherent Shrinkage Method for Fast and More Reliable Welding Distortion Calculations

This paper describes the implementation of a simple strategy adopted for the inherent shrinkage method (ISM) to predict welding-induced distortion. This strategy not only makes it possible for the ISM to reach accuracy levels similar to the detailed transient analysis method (considered the most reliable technique for calculating welding distortion) but also significantly reduces the time required for these types of calculations. This strategy is based on the sequential activation of welding blocks to account for welding direction and transient movement of the heat source. As a result, a significant improvement in distortion prediction is achieved. This is demonstrated by experimentally measuring and numerically analyzing distortions in two case studies: a vane segment subassembly of an aero-engine, represented with 3D-solid elements, and a car body component, represented with 3D-shell elements. The proposed strategy proves to be a good alternative for quickly estimating the correct behaviors of large welded components and may have important practical applications in the manufacturing industry.     

Estimating the upcrossings index

For stationary sequences, under general dependence restrictions, any limiting point process for time normalized upcrossings of high levels is a compound Poisson process, i.e., there is a clustering of high upcrossings, where the underlying Poisson points represent cluster positions and the multiplicities correspond to cluster sizes. For such classes of stationary sequences, there exists the upcrossings index η, 0≤η≤1, which is directly related to the extremal index θ, 0≤θ≤1, for suitable high levels. In this paper, we consider the problem of estimating the upcrossings index η for a class of stationary sequences satisfying a mild oscillation restriction. For the proposed estimator, properties such as consistency and asymptotic normality are studied. Finally, the performance of the estimator is assessed through simulation studies for autoregressive processes and case studies in the fields of environment and finance. Comparisons with other estimators derived from well known estimators of the extremal index are also presented.     

Iberian universities: a characterisation from ESI rankings

The access to bibliographic and citation databases allows to evaluate scientific performance, and provides useful means of general characterisation. In this paper we investigate the clustering of Iberian universities, resulting from the similarity in the number and specific nature of the scientific disciplines given by the Essential Science Indicators database. A further refining of the analysis, as provided by PCA, clearly reveals the relationship between the universities and the scientific disciplines in the main groups. Similarity between universities is not dictated only by the number of areas in the ranking, but also stems from the nature of the ranked scientific areas and the specific combination in each university.     

Metaheuristic optimization frameworks: a survey and benchmarking

This paper performs an unprecedented comparative study of Metaheuristic optimization frameworks. As criteria for comparison a set of 271 features grouped in 30 characteristics and 6 areas has been selected. These features include the different metaheuristic techniques covered, mechanisms for solution encoding, constraint handling, neighborhood specification, hybridization, parallel and distributed computation, software engineering best practices, documentation and user interface, etc. A metric has been defined for each feature so that the scores obtained by a framework are averaged within each group of features, leading to a final average score for each framework. Out of 33 frameworks ten have been selected from the literature using well-defined filtering criteria, and the results of the comparison are analyzed with the aim of identifying improvement areas and gaps in specific frameworks and the whole set. Generally speaking, a significant lack of support has been found for hyper-heuristics, and parallel and distributed computing capabilities. It is also desirable to have a wider implementation of some Software Engineering best practices. Finally, a wider support for some metaheuristics and hybridization capabilities is needed.     

Fly ash addition in clayey materials to improve the quality of solid bricks

The technical quality of two compositionally different groups of solid bricks fired between 800 and 1000 °C was evaluated. Five weight percentage of fly ash was added to both groups and they were compared with similar bricks with no added fly ash.The textures of the bricks with fly ash were very similar to the textures of those without it, except that the samples with the additive contained spherical fly ash particles with diameters ranging from 0.1 to 10 μm. These particles led to a reduction in the density of the bricks and a substantial improvement in their durability, with less decay being caused by salt crystallization in the pores. This is because fly ash causes a reduction in the number of micropores, the pores that make porous materials most vulnerable to salt-induced decay. Use of this additive could have practical implications as a means of recycling and for achieving cost savings in brick production.     

Towards occupant-centric simulation-aided building design: a case study

ABSTRACT

This paper aims at illustrating the importance of occupant modelling for decision-making during the building design process. It identifies the energy implications of conventional ways of modelling occupants for the design of office buildings. Furthermore, it presents a step towards bridging the gap between the research efforts and conventional practices within the field of building performance simulation (BPS) aided design. The paper first describes occupant-related assumptions that were made during the design process of a case study office building, obtained via stakeholder interviews. Then, the impact of these assumptions on the design decisions is examined through a simulation-based investigation. The stakeholder interviews revealed that professionals from each design discipline made significantly different assumptions about occupants. The simulation results showed that assumptions about occupants and their behaviour impacted predicted energy savings of some design decisions by a factor of five or more.     

Form birefringence and turbidity of polystyrene/poly(methyl methacrylate) blends in slit dies and planar contractions

The birefringence and turbidity of a polystyrene/poly(methyl methacrylate) (PMMA) blend, with the concentration of the PMMA dispersed phase ranging up to 1%, were measured in both a slit channel with a constant cross section and a planar hyperbolic contraction/expansion (8:1:8). The measurements were performed by the attachment of a modular rheo‐optical die to a twin‐screw extruder. The optical arrangement had a red light‐emitting diode as the source and two photoresistors, with one of them measuring the turbidity and the other one measuring the transmitted intensity between cross‐polarizers. The experimental procedure consisted of the stopping of the extruder feeding, while the screw rotation was kept constant. Because the form birefringence could be associated with the shape of the droplets, these measurements were used to infer information about the PMMA droplet deformation and breakup. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44066.     

Uncalibrated visual servoing using the fundamental matrix

This paper describes a new algorithm for visual control of an uncalibrated 3 DOF joint system, using two weakly calibrated fixed cameras. The algorithm estimates on-line the Image Jacobian, a matrix which linearly relates joint velocity and image feature velocity. In our experiments we prove that by using the fundamental matrix, robustness of the estimation in the presence of noise is significantly increased with respect to already existing algorithms in specialized literature.