Effects of worker size on the dynamics of fire ant tunnel construction

Social insects work together to complete tasks. However, different individuals within a colony may vary in task proficiency. We investigated if fire ant (Solenopsis invicta) worker body size influenced the ability to construct tunnels—a key component of subterranean nests. We monitored excavation by worker groups in a substrate of small wetted glass particles in quasi-two-dimensional arenas. Morphological and network features of the tunnel system were measured. Total tunnel area did not differ significantly between groups of large and small workers, although the tunnel area of control sized workers was significantly larger than that of large workers. Moreover, large workers created wider but shorter tunnels, with slower growth rate of tunnel number. However, edge–vertex scaling and degree distribution of the tunnel network were similar across all treatments. In all cases, the amount of excavated material was correlated with the number of active workers. Our study reveals that morphological features of excavated tunnels show modest variation when constructed by workers of varying sizes, but topological features associated with the tunnel network are conserved. These results suggest that important behavioural aspects of tunnel construction—and thus nest building—are similar among morphologically distinct members of fire ant societies.     

Comparison of calculations for interplanar distances in a crystal lattice

The derivations for the general formulae of lattice interplanar distances are reviewed along with the methods using elementary geometry, intermediate Cartesian axes, and reciprocal lattice vectors. To highlight the characteristics of these three methods and the connections between them, examples for the simple cases such as orthorhombic, hexagonal, and rhombohedral systems are included. Calculations from reciprocal space are established from those from direct space with heavily involved mathematics for which details are seldom included in crystallography monographs. The only geometric method found in the literature for the interplanar distances in a crystal lattice is derived for a few specific simple cases with cos²α?+?cos²β?+?cos²γ?=?1, where α, β, and γ are the angles between the normal to the plane and the axes of a orthogonal system. However, the geometric method introduced in this work is a newly developed method and this method is complementary to other methods including the advanced contemporary reciprocal method. The connections between Cartesian and crystal coordinate systems, for angular relationships and the volume of unit cell are revealed. The interplanar spacing in non-primitive lattice and crystals are also discussed.     

Experimental and theoretical assessment of the inhibiting action of <Emphasis Type="Italic">Aspilia africana</Emphasis> extract on corrosion aluminium alloy AA3003 in hydrochloric acid

The adsorption of Aspilia africana extract and subsequent corrosion inhibition of aluminium alloy AA3003 in hydrochloric acid solutions have been investigated using gravimetric and electrochemical techniques. Inhibition efficiency increased with extract concentration and temperature rise. Polarization studies revealed that the extract essentially inhibited the cathodic reaction. An adsorption mechanism involving physisorption and chemisorption of extract constituents at low and high temperatures, respectively, has been proposed from the trend of adsorption-free energies. Quantum chemical computations and molecular dynamics simulations described the individual contributions of some extract constituents to the observed inhibiting effect.     

Towards a contingent approach of customer involvement in defence projects: An exploratory study

This paper reports the main results of an exploratory, multiple case study investigating customer involvement practices in system development projects in the Israeli defence industry. The study proposes and examines a theoretical contingency model regarding the effect of customer involvement modes on project success, moderated by project characteristics. It focuses specifically on the working mode of customers' representatives along the continuum between external supervision to full participation in project activities.     

A survey of tagging techniques for music,speech and environmental sound

Sound tagging has been studied for years. Among all sound types, music, speech, and environmental sound are three hottest research areas. This survey aims to provide an overview about the state-of-the-art development in these areas. We discuss about the meaning of tagging in different sound areas at the beginning of the journey. Some examples of sound tagging applications are introduced in order to illustrate the significance of this research. Typical tagging techniques include manual, automatic, and semi-automatic approaches. After reviewing work in music, speech and environmental sound tagging, we compare them and state the research progress to date. Research gaps are identified for each research area and the common features and discriminations between three areas are discovered as well. Published datasets, tools used by researchers, and evaluation measures frequently applied in the analysis are listed. In the end, we summarise the worldwide distribution of countries dedicated to sound tagging research for years.     

Learning non-monotonic additive value functions for multicriteria decision making

Multiattribute additive value functions constitute an important class of models for multicriteria decision making. Such models are often used to rank a set of alternatives or to classify them into pre-defined groups. Preference disaggregation techniques have been used to construct additive value models using linear programming techniques based on the assumption of monotonic preferences. This paper presents a methodology to construct non-monotonic value function models, using an evolutionary optimization approach. The methodology is implemented for the construction of multicriteria models that can be used to classify the alternatives in pre-defined groups, with an application to credit rating.