Genetic Relatedness and Chemical Profiles in an Unusually Peaceful Eusocial Bee

Colonies of the stingless bee Tetragonilla collina frequently occur in unusually high densities and in direct neighborhood (nest aggregations), in rainforests of Southeast Asia. To investigate whether close relatedness and/or similar chemical profiles facilitate the co-occurrence of multiple T. collina colonies, we investigated aggressive behavior, genetic relatedness and cuticular hydrocarbon (CHC) profiles within and between colonies and nest aggregations. Although 17 out of 19 colonies within aggregations were largely unrelated, intraspecific aggression between different colonies was basically absent both within and among aggregations. This lack of aggression should favor social parasitism and hence the occurrence of unrelated individuals within a colony. However, low within-colony relatedness was found in only five out of 19 colonies where it may be explained by queen turnover or the occurrence of foreign workers. CHC profiles of colonies within and among aggregations were statistically different. However, many workers could chemically not be assigned to their maternal colony, indicating considerable overlap among colonies in odor profiles of workers. Moreover, odor profiles tended to be more similar within than among aggregations, although most colonies were unrelated. Thus, CHC profiles were a poor indicator of relatedness in T. collina. The lack of correlation between relatedness and chemical similarity in T. collina may be explained by the incorporation of resin-derived terpenes in their CHC profiles. The composition of these terpenes was highly similar among colonies, particularly within aggregations, hence potentially decreasing chemical distinctiveness and increasing behavioral tolerance.     

Female sex pheromone of the melonworm,Diaphania hyalinata (Lepidoptera: Pyralidae), and analysis of male responses to pheromone in a flight tunnel

Ten C₁₆ chain-length compounds were identified from heptane extracts of ovipositors of female melonworm,Diaphania hyalinata (L.). The major constituents of the extracts were (E)-11-hexadecenal and (E,E)-10,12-hexadecadienal [(E,E)-10,12–16:Ald] and the alcohols and acetates of these olefins were found in trace amounts (<2%). Extracts also contained traces of (E,Z)- and (Z,Z)-10,12-16:Ald, hexadecanal, and 1-hexadecanol. Analysis of the behavioral responses of males to synthetic mixtures of these compounds and responses to ovipositor extracts in a flight tunnel showed that a synthetic mixture of the 10 compounds elicited a behavioral repertoire from males that was indistinguishable from that elicited by ovipositor extract. Flight tunnel studies also indicated that six of the 10 compounds probably represent the essential components of the female's sex pheromone.Supported in part by USDA Cooperative Agreement No. 58-32U4-1-299. Scientific Article No. A-4073, Contribution No. 7058 of the Maryland Agricultural Experiment Station. Mention of a commercial product in this paper does not constitute a recommendation by the U.S. Department of Agriculture.     

Very fast ultracentrifugation of serum lipoproteins: influence on lipoprotein separation and composition

A very short run time and small sample volumes in the separation of lipoproteins by preparative ultracentrifugation are needed for several investigations. Recently, a very fast sequential separation method was described that needs only 100 min for one run in a centrifugal field of 625,000 x g. We studied the influence of centrifugal fields of this dimension on lipoprotein separation and lipoprotein particle integrity using a Beckman Optima TLX ultracentrifuge with a TLA-120.2 rotor. Rotor speed (120/90/60/30.10(3) rev./min) and run time (100 min/3 h/6.7 h/27 h) were selected in such a way that the product of centrifugal field and run time remained constant. The first conditions correspond to the very fast ultracentrifugation (VFU) procedure with a centrifugal field of 625,000 x g. Thirty different plasma samples covering a wide range of lipid and protein concentrations were separated in the course of two centrifugal runs at densities of 1.006 and 1.063 kg/l which yielded very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and the subnatant of low-density lipoproteins, including high-density lipoproteins (HDL) and concomitant sedimented plasma proteins. The major lipid components of the lipoproteins, triacylglycerols, free and esterified cholesterol, phospholipids and the apolipoproteins B and A-I, were estimated considering the masses of the tube contents after a slicing procedure. Measurements of lipids and proteins showed a very good recovery of better than 94% and 91%, respectively, and precision-within-series (coefficient of variation) of better than 4.2% and 6.5%, respectively. The effects of the rotor speed on the lipoprotein structure appeared to be weak. With increasing rotor speed, VLDL and LDL lipid constituents principally tended to decrease, whereas they increased in the subnatant of the LDL-run. The mean lipoprotein mass composition, considering the mass percentage of each measured particle constituent, did not show significant alterations. Total protein decreased in VLDL and in LDL and increased in the subnatant of the LDL-run. As checked by an enzyme-linked immunosorbent assay (ELISA) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), the protein effects were due to nearly complete disappearance of contaminating plasma proteins, especially albumin as the major contamination of VLDL and LDL. The apolipoproteins (apo) B-100, A-I, E and C-I to C-III remained nearly unaffected. The main advantages of VFU were the very short run time (cumulative flotation time is 3.4 h) and the elemination of albumin without repeated runs. The procedure was suitable for the assessment of lipid and protein constituents in lipoproteins from very small plasma samples (500 microliters).     

Control of low-density gypsy moth (Lepidoptera: Lymantriidae) populations by mating disruption with pheromone

This four-year study demonstrated that low-density populations of the gypsy moth,Lymantria dispar (L.), were effectively suppressed by annual aerial application of 75 g of racemic disparlure per hectare formulated in plastic laminate flakes. These tests also showed that, when plots were treated with 150 g of pheromone per hectare in 1990 only and left untreated for the following three years, populations continued to be suppressed in 1991–1993 as compared with the controls. Although none of the plots were treated in 1994, population assessment continued and showed that the gypsy moth population density remained low in the plots that had been treated annually for the preceding four years. The laminate flakes released an average of 0.48 g disparlure per day per hectare from each of the two applications in 1990, and 0.72 g per day per hectare from the single application in each of the following three years (1991–1993). Only 27–40% of the applied pheromone dose was emitted during male moth flight.     

The deposition of group III nitrides on silicon substrates

The reaction between silicon substrates and ammonia present in the systems GaCl (AlCl₃)-NH₃-H₂ (He) during the vapour phase epitaxy of Group III nitrides has been investigated. Silicon was treated with an NH₃-HCl-H₂ mixture at a constant temperature in the range873–1273 K. Using electron spectroscopy for chemical analysis measurements layers of Si₃N₄ and Si₃N₄-SiO₂ were detected at the silicon surface. Reflection high energy electron diffraction tests indicated the amorphous nature of this passivating layer which was found partially or completely to prevent epitaxial deposition of the Group III nitrides. The deposits of GaN on Si(111) and Si(100) were either polycrystalline or textured and an amorphous Si₃N₄-SiO₂ interface was found.     

Stepwise current-driven release of attogram quantities of copper iodide encapsulated in carbon nanotubes

Encapsulated nanograins of copper iodide have been sequentially discharged from individual carbon nanotubes. Using a high resolution electron microscope equipped with a two-terminal electrical measurements unit, it was possible to manipulate the filling contents with precisions of a few attograms at a time. Changes in electrical resistance and filling ratio were followed in tandem and in real-time. It is shown that the pulsed release of the halide is directly related to the overall conductance of the filled nanotube.     

Optical topometry of surfaces with locally changing materials,layers and contaminations Part 2: Fringe projection topometry

Conventional topometry evaluation procedures applied to surfaces with locally changing materials or layer structures can result in significant errors in the topometric heights. A new theoretical approach, developed for two-beam interferometry in part 1, is now applied to fringe projection topometry, where the oblique incidence of two or three partial plane-wave components has to be considered. Important effects of contrast and phase are presented and applied to some surface structures, and errors in the measured surface height are calculated.     

Effect of Carbon‐Based Materials on the Early Hydration of Tricalcium Silicate

Two types of carbon‐based materials, i.e., mesoporous carbon and HNO₃‐oxidized carbon nanotubes, with nearly the same specific surface area and abundant in surface oxygen‐containing functional groups were selected in order to examine their effect on the hydration of tricalcium silicate (C₃S), the main portland cement component, in early stages. Different methods, including XPS and TG‐MS analyses, electrokinetic potential measurements, as well as determination of adsorption capacity for calcium ions from aqueous solutions, were used to investigate the physicochemical surface properties of the selected carbon‐based materials. It was found that the carbon‐based materials with high specific surface area and rich in oxygen‐containing functional groups on their surfaces have a catalytic effect on early C₃S hydration. It was observed that the modification of C₃S paste with the selected materials added in high concentrations (1 wt% and higher) led to an increase in the rate and degree of C₃S hydration in the early stages. The mechanism of early C₃S hydration accelerated by carbon‐based materials rich in surface functional groups was clarified by the example of the mesoporous carbon. It was found that the oxygen‐containing functional groups present on the carbon surface have both an influence on the content of calcium ions in the aqueous phase of the C₃S paste and an indirect positive effect in relation to the specific surface of C₃S.