Predicting velocity in bendway weir eddy fields

Rehabilitation of the Middle Rio Grande (MRG) in central New Mexico has become necessary because of changes in morphology resulting from the installation of dams, and because of habitat restoration considerations for the endangered Rio Grande silvery minnow (Hybognathus amarus). Bendway weirs are erosion control and channel‐stabilization structures placed transverse to the channel flow that have been increasingly used to prevent river migration while simultaneously enhancing aquatic habitat. Plans for rehabilitation along the MRG include the use of bendway weirs; however, past projects using these structures have relied on field experience and engineering judgment rather than specific design guidelines. A physical model of a reach of the MRG was constructed to develop empirical design equations for eddy velocities in bendway weir fields. Data from physical model simulations were used to develop two empirical expressions for predicting eddy velocities behind bendway weirs, along with two expressions for predicting velocities at the toe of installed weirs. These equations relate the velocity found after bendway weir installation to weir design characteristics and pre‐weir channel conditions. A designer can use the described approach to predict velocities in eddies and velocities at the toe of bendway weirs using only weir design variables and pre‐weir channel conditions, and thus avoid some of the uncertainty with weir design that previously existed. Copyright © 2009 John Wiley & Sons, Ltd.     

CATH--a hierarchic classification of protein domain structures

BACKGROUND: Protein evolution gives rise to families of structurally related proteins, within which sequence identities can be extremely low. As a result, structure-based classifications can be effective at identifying unanticipated relationships in known structures and in optimal cases function can also be assigned. The ever increasing number of known protein structures is too large to classify all proteins manually, therefore, automatic methods are needed for fast evaluation of protein structures. RESULTS: We present a semi-automatic procedure for deriving a novel hierarchical classification of protein domain structures (CATH). The four main levels of our classification are protein class (C), architecture (A), topology (T) and homologous superfamily (H). Class is the simplest level, and it essentially describes the secondary structure composition of each domain. In contrast, architecture summarises the shape revealed by the orientations of the secondary structure units, such as barrels and sandwiches. At the topology level, sequential connectivity is considered, such that members of the same architecture might have quite different topologies. When structures belonging to the same T-level have suitably high similarities combined with similar functions, the proteins are assumed to be evolutionarily related and put into the same homologous superfamily. CONCLUSIONS: Analysis of the structural families generated by CATH reveals the prominent features of protein structure space. We find that nearly a third of the homologous superfamilies (H-levels) belong to ten major T-levels, which we call superfolds, and furthermore that nearly two-thirds of these H-levels cluster into nine simple architectures. A database of well-characterised protein structure families, such as CATH, will facilitate the assignment of structure-function/evolution relationships to both known and newly determined protein structures.     

The ({beta}{alpha})8 glycosidases: sequence and structure analyses suggest distant evolutionary relationships

There are currently at least nine distinct glycosidase sequencefamilies which are all known to adopt a TIM barrel fold [Henrissat,B.and Davies,G. (1997) Curr. Opin. Struct. Biol., 7, 637–644].To explore the relationships between these enzymes and theirevolution, comprehensive sequence and structure comparisonswere performed, generating four distinct clusters. The firstcluster, S1, comprises the     

A test of subliminal symbiotic activation as a means of alleviating depression.

Thirty-six depressive subjects were randomly assigned to one of three treatment groups. Group 1 subjects received 60 subliminal presentations of a slide of two figures and the words MOMMY AND I ARE ONE for male subjects and DADDY AND I ARE ONE for female subjects. Group 2 subjects received 60 subliminal slide presentations of a single figure with the words PEOPLE ARE WALKING. Group 3 subjects did not receive a slide. A pretest and posttest Beck Depression Inventory was administered to assess depression increase or decrease. The "subliminal" therapy was carried out over four different sessions. The data show that Group 1 subjects significantly reduced depression scores from pretest to posttest, whereas the subjects in Groups 2 and 3 did not reduce depression scores. Discussion is centered on comparisons of the data with past findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Numerical analysis of density-induced segregation during die filling

In this study, segregation behaviour of binary granular mixtures with the same particle size but different densities during die filling in the presence of air was investigated using a combined discrete element method (DEM) and computational fluid dynamics (CFD) approach, in which the kinematics of particles was modelled using DEM, the motion of air was analysed using CFD and a two-way coupling of the particles and the air was incorporated. The depositions of powder from stationary and moving shoes into the die cavities of different geometries were simulated and the corresponding segregation behaviours were analysed. It has been found that, for die filling from a stationary shoe, the concentration distributions of the heavy and light particles along the die width mainly depend on the initial spatial distribution of the granular mixture in the shoe. For die filling from a moving shoe, a low concentration of light particles on the leading side of the die (referring to the direction of the shoe motion) is observed for die filling with a square die, in which the process is dominated by nose flow. The density difference can cause segregation along the die depth with a low concentration of light particles at the bottom. The presence of air enhances this segregation tendency by resisting the flow of light particles into the bottom of the die and causes a higher concentration of the light particles at the top. Finally, the segregation index, defined as the volume weighted root-mean-square deviation in the content of light particles, was introduced to quantify the degree of segregation in the horizontal and vertical directions. It has been found that the degree of segregation is determined by the presence of air and also the powder flow pattern.     

The effects of air and particle density difference on segregation of powder mixtures during die filling

Segregation of mono-disperse binary mixtures with different particle densities during die filling in the presence of air was numerically analysed using a coupled discrete element method (DEM) and computational fluid dynamics (CFD) approach. Die filling with powders of different particle density ratios (i.e. the ratio of the heavy particles to the light particles) at various shoe speeds was simulated, in order to explore the effects of air and particle density difference on segregation. For die filling from a stationary shoe, the air can induce significant segregation by hindering the deposition of light particles (i.e., air-sensitive particles). As the particle density ratio increases, the light particles are deposited into the die at even lower speeds compared with the heavy ones due to the effect of air drag, resulting in an increase in the degree of segregation. For die filling with a moving shoe, segregation occurs due to different post-collisional velocities resulting from different particle inertia; and the degree of segregation increases as the particle density ratio increases due to the increasing difference in particle inertia. It is found that, as the shoe velocity increases, the powder flow pattern changes from nose flow dominated to bulk flow dominated and the degree of segregation generally decreases. The effect of air is limited for nose flow dominated die filling because the air can easily evacuate through the gap between the die walls and flowing powder stream. When bulk flow dominates in die filling, the air can be entrapped in the die, which has a significant impact on the powder flow and segregation behaviours. Finally, the effect of interparticle friction on segregation was investigated.     

Channel size distribution of complex three-dimensional microstructures calculated from the topological characterization of isodistance structures

We present a novel approach for quantifying the channel size distribution (CSD) of complex three-dimensional microstructures. The CSD, which characterizes the probability of finding a channel bottleneck with a given size, is difficult to measure for materials with complex microstructures that are extensively interconnected. More importantly, insights about the physical properties of these materials, such as transport properties, may be provided by their CSD. The CSD is measured by topological characterization of a distance function, which is calculated from complex microstructural data using the level set method. The newly developed method for calculating CSD is shown to be robust such that it is applicable to both smooth and discontinuous (bi-level) data. The method is demonstrated by calculating the CSDs for three-dimensional microstructures formed through conserved (Cahn–Hilliard) and nonconserved (Allen–Cahn) dynamics. We found significant differences between the two structures in their characteristic channel size and the width of their distributions, even though their genera, a measure of connectivity, are almost identical. The CSD, which was not previously available for complex microstructures, will provide a new means to correlate properties of composite materials with their performance.