Factors affecting the mechanical properties of mica-filled polypropylenes

Water-ground Phlogopite mica (Kemira Siilinjarvi phlogopite) has been evaluated as a reinforcing filler in polypropylene. The major factors which influence the composite strength and modulus include the size, aspect ratio, and uniformity of the mica flakes. Aqueous delamination permits the production of very small flakes (less than 44 microns diameter) with aspect ratios near 50. Such small flakes impart greater tensile and modulus values to polypropylene than larger flakes and the former can also be reprocessed many times without any deterioration of properties. Surface treatment is necessary for adequate dispersion and coupling, particularly with the finely divided mica fillers. Other properties such as the heat-distortion temperature, fracture toughness, and gas permeability are also influenced by the mean size and aspect ratio of the mica filler. Guidelines are presented to indicate the preferred characteristics of mica fillers for optimum performance.     

Fractal dimension applied to plant identification

This article discusses methods to identify plants by analysing leaf complexity based on estimating their fractal dimension. Leaves were analyzed according to the complexity of their internal and external shapes. A computational program was developed to process, analyze and extract the features of leaf images, thereby allowing for automatic plant identification. Results are presented from two experiments, the first to identify plant species from the Brazilian Atlantic forest and Brazilian Cerrado scrublands, using fifty leaf samples from ten different species, and the second to identify four different species from genus Passiflora, using twenty leaf samples for each class. A comparison is made of two methods to estimate fractal dimension (box-counting and multiscale Minkowski). The results are discussed to determine the best approach to analyze shape complexity based on the performance of the technique, when estimating fractal dimension and identifying plants.     

Solving functional reliability issue for an optical electrostatic switch

In this paper, we report the advantage of using AC actuating signal for driving micro electro mechanical systems actuators instead of DC voltages. The study is based upon micro mirror devices used in digital mode for optical switching operation. When the pull-in effect is used, charge injection occurs when the micro mirror is maintained in the deflected position. To avoid this effect, a geometrical solution is to realize grounded landing electrodes which are electro-statically separated from the control electrodes. Another solution is the use of AC signal which eliminates charge injection particularly if a bipolar signal is used. Long-term experiments have demonstrated the reliability of such a signal command to avoid injection of electric charges.     

On a novel interpretation of PVC antiplasticization based on some local chain conformations

Summary The transition of a poly(vinyl chloride) after either nucleophilic substitution to various extents or plasticization with distinct amounts of diocytl phthalate has been measured by Dynamical Mechanical Thermal Analysis. Both sets of experiments are shown to result in similar loss of transition. The results are argued in the light of prior work on the substitution mechanism determining role of the mmr chain segments at the end of isotactic sequences. They strongly suggest the mmr structures to interact specifically with plasticizer thereby becoming stiffer (antiplasticization).     

Skeleton computation of orthogonal polyhedra

Skeletons are powerful geometric abstractions that provide useful representations for a number of geometric operations. The straight skeleton has a lower combinatorial complexity compared with the medial axis. Moreover, while the medial axis of a polyhedron is composed of quadric surfaces the straight skeleton just consist of planar faces. Although there exist several methods to compute the straight skeleton of a polygon, the straight skeleton of polyhedra has been paid much less attention. We require to compute the skeleton of very large datasets storing orthogonal polyhedra. Furthermore, we need to treat geometric degeneracies that usually arise when dealing with orthogonal polyhedra. We present a new approach so as to robustly compute the straight skeleton of orthogonal polyhedra. We follow a geometric technique that works directly with the boundary of an orthogonal polyhedron. Our approach is output sensitive with respect to the number of vertices of the skeleton and solves geometric degeneracies. Unlike the existing straight skeleton algorithms that shrink the object boundary to obtain the skeleton, our algorithm relies on the plane sweep paradigm. The resulting skeleton is only composed of axis‐aligned and 45° rotated planar faces and edges.     

Unraveling Membrane Perturbations Caused by the Bacterial Riboregulator Hfq

Hfq is a pleiotropic regulator that mediates several aspects of bacterial RNA metabolism. The protein notably regulates translation efficiency and RNA decay in Gram-negative bacteria, usually via its interaction with small regulatory RNAs. Previously, we showed that the Hfq C-terminal region forms an amyloid-like structure and that these fibrils interact with membranes. The immediate consequence of this interaction is a disruption of the membrane, but the effect on Hfq structure was unknown. To investigate details of the mechanism of interaction, the present work uses different in vitro biophysical approaches. We show that the Hfq C-terminal region influences membrane integrity and, conversely, that the membrane specifically affects the amyloid assembly. The reported effect of this bacterial master regulator on membrane integrity is discussed in light of the possible consequence on small regulatory RNA-based regulation.     

Cover Fire emissions from the Orinoco river delta

To assess changes in spatial heterogeneity of non-anthropogenically disturbed rainforests, we compared lacunarity of Landsat MSS imagery over the Peruvian lowlands from the 1970s and 1980s. The organizational patterns associated with lower NDVI values were found to be significantly more clumped during the 1970s whereas those associated with higher NDVI values became more clumped during the 1980s. These spatial dynamics suggest that these rainforests represent non-equilibrium systems at coarse hierarchical levels which are typically thought to be stable at decadal intervals.     

Practitioner's Insight: Learning to Manage Emerging Technologies

New management techniques and policies need to be developed in order for more effective commercialization of emerging technologies.     

High efficiency coupling technique for planar photonic crystalwaveguides

A high efficiency coupling technique for photonic crystal waveguides is proposed. The technique is based on setting a single defect within a tapered photonic crystal waveguide. Simulation results show that the optimised scheme maximises the power transmission up to 87.5% at a wavelength of λ = 1.55 μm for a 0.5 μm-long photonic crystal taper