A Review of Ant Cuticular Hydrocarbons

We compared the published cuticular hydrocarbon (CHC) profiles of 78 ant species across 5 subfamilies. Almost 1,000 CHCs have been described for these species, composing 187 distinct homologous series and ten hydrocarbon groups. In descending order of occurrence were: n-alkanes > monomethylalkanes > dimethylalkanes > alkenes > dienes>> trimethylalkanes>> methylalkenes > methylalkadienes > trienes > tetramethylalkanes. Odd chain lengths and positions of methyl or double bonds at odd carbon numbers were far more numerous than even chain-length compounds or bond positions. Although each species possess its own unique pattern of CHCs, we found no association between CHC profile and phylogeny. The production of the biosynthetically complex compounds (e.g., methyl branched dienes) by the most primitive living ant suggests that the basic genetic architecture required to produce the rich diversity of CHCs was already present prior to their adaptive radiation. Unlike the ubiquitous n-alkanes and monomethylalkanes, there is a huge diversity of species-specific dimethylalkanes that makes them likely candidates for species and nest-mate discrimination signals.     

The effects of filler size on the properties of thermoplastic polyolefin blends

The effects of filler size on the properties of a thermoplastic polyolefin (TPO) blend were examined by using wollastonite and talc with particle sizes ranging from 1.2 to 40 μm. While addition of filler produced significant changes in the mechanical properties of the blend, filler size affected only impact strength. However, filler size, filler coating, and injection speed had a major effect on the surface properties of the blend. Faster injection produced denser “shear zone layers” which exhibited better scratch resistance and poorer paint adhesion than those obtained with slower injection. Scartch resistance and paint adhesion also decreased with increasing filler particle size. Filler coatings altered the scratch and adhesion properties of the polypropylene (PP) blends.     

Plasma Sprayed Metal-Ceramic Coatings and Modification of Their Structure with Pulsed Electron Beam Irradiation

Composite powder obtained from mechanically crushed titanium carbide—metal binder cermet compacts deserves special mention for plasma spraying of wear-resistant coatings. However, cermet coatings sprayed using this powder have comparatively high porosity. The porosity causes the mechanical strength of the coating to largely deteriorate, and it also lowers the strength of the bond between the coating and the substrate. Computational and physical experiments were performed in this area to reveal the possibilities offered by pulsed electron beam irradiation for structural modification of 70 vol.%TiC-(Ni-Cr) powder coatings. The authors evaluated optimal values of process parameters for suitability in implementing a controlled thermal treatment of coatings under conditions of solid-liquid interaction of components in the cermet composition with each other and with the steel substrate. Evolution of the structure and physical properties of the cermet coatings under rapid heating and following cooling in a wide range of temperatures typical of pulsed irradiation conditions have been examined.     

Effect of electrolytic oxidation and hydrogenation on the magnetization distribution and magnetic properties of ribbons of amorphous soft magnetic iron-based alloys

The effect of electrolytic oxidation and hydrogenation on the magnetization distribution and magnetic properties of ribbons of amorphous soft magnetic iron-based alloys has been investigated on the example of the Fe₇₇Ni₁Si₉B₁₃ and Fe₈₁B₁₃Si₄C₂ alloys. The results of the investigation showed that hydrogenation and oxidation of the surface of the ribbon lead to changes in the magnetic properties, which agree with changes in its magnetic state. A decrease in the volume of domains with orthogonal magnetization observed upon oxidation is caused by the large effective diameter of oxygen atoms inducing a higher level of planar tensile stresses upon incorporation into the ribbon surface. A reduction (observed in both cases) in the volume fraction of domains with a planar magnetization oriented along the ribbon axis is connected with the appearance of pseudo-uniaxial tension in the plane of the ribbon across its axis, since the concentration of atoms incorporated into the surface is enchanced in this direction. The interaction of the surface of the ribbon at room temperature with vapor leads to identical changes in the magnetic characteristics and redistribution of magnetization in its plane.     

A goal programming model for aggregate production planning with resource utilization constraint

This paper addresses the aggregate production planning problem with different operational constraints, including production capacity, workforce level, factory locations, machine utilization, storage space and other resource limitations. Three production plants in North America and one in China are considered simultaneously. A pre-emptive goal programming model is developed to maximize profit, minimize repairing cost and maximize machine utilization of the Chinese production plant hierarchically. A set of data from a surface and materials science company is used to test the effectiveness and the efficiency of the proposed model. Results illustrate the flexibility and the robustness of the proposed model by adjusting goal priorities with respect to importance of each objective and the aspiration level with respect to desired target values.     

Selective deficits in reflective cognition of polydrug abusers: Preliminary findings.

The goal of this study was to determine if drug abusers exhibited specific deficits in reflective cognition similar to that observed in detoxified alcoholics who were otherwise cognitively intact. Fifteen drug abusers and 15 non-drug-abusing control participants were administered a series of cognitive tests, which assessed various learning and memory functions. Drug abusers did not differ from controls with respect to most cognitive domains. However, drug abusers exhibited selective deficits in processing unstructured information and in inhibiting intrusion errors during word recall. Such deficits in reflective functioning may play a role in the initiation of drug use or maintenance of drug dependence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transmission of a bending torque at a tight joint

To obtain a better idea of the influence of various factors on the probability of fretting corrosion in a tight joint, the tangential pliability of the joint is taken into account. The factors considered are the flexural stress of the shaft; the pressure at the contact surface; the mean height of the microprojections at the contact surfaces; and the length of the joint.     

Effects of scenery, lighting, glideslope, and experience on timing the landing flare.

This study examined three visual strategies for timing the initiation of the landing flare based on perceptions of either: (a) a critical height above ground level; (b) a critical runway width angle (Ψ); or (c) a critical time-to-contact (TTC) with the runway. Visual displays simulated landing approaches with trial-to-trial variations in glideslope, lighting, and scene detail. Twenty-four participants (8 private pilots, 8 student pilots, and 8 nonpilots) were instructed to initiate the flare when they perceived that their TTC with the runway (30 m wide by 840 m long) had reached a critical value of 2 seconds. Our results demonstrated a significant effect of flight experience on flare timing accuracy and dominance of the height-based strategy over the runway-width-angle and TTC-based strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)