3-Hydroxy-2-butanone and the first encounter fight in the male lobster cockroach, Nauphoeta cinerea

Although agonistic behavior in the male lobster cockroach, Nauphoeta cinerea, has been known for more than 40 years, this is the first study to directly collect and quantify the emitted pheromones. In the present study, emitted volatile pheromones were collected from each male pair for 60 min during the first encounter fight and identified and quantified by gas chromatography–mass spectrometry. The major compound collected was 3-hydroxy-2-butanone (3H-2B). The strength of the attack by the dominant male was classified into three categories from weakest (C) to strongest (A). Of the 92 pairs, eight (8.7%) showed no agonistic interactions, and the amount of 3H-2B collected was 121.8±37.7 ng/male pair. In the five pairs (5.4%) displaying attack strength C, the amount of 3H-2B collected was 689.6±273.7 ng/male pair, and the attack duration was 9.6±2.4 min. In the 53 pairs (57.6%) showing attack strength B, the corresponding values were 5396.2±449.0 ng/male pair and 22.7±1.6 min, while those for the 26 pairs (28.3%) showing attack strength A were 7910.4±1120.6 ng/male pair and 24.9±2.9 min. For both attack strengths A and B, a linear relationship was found between the amount of 3H-2B collected and attack duration, suggesting that the longer the duration of the attack, the more 3H-2B was emitted. In addition, the rate of 3H-2B emission for attack strength A was significantly higher than that for attack strength B. Using Vaseline-coating, we demonstrated that, in the first encounter fight, the 3H-2B was emitted by the dominant male.     

Local population size in a flightless insect: importance of patch structure-dependent mortality

In spatially heterogeneous systems, utilizing population models to integrate the effects of multiple population rates can yield powerful insights into the relative importance of the component rates. The relative importance of demographic rates and dispersal in shaping the distribution of the western tussock moth (Orgyia vetusta) among patches of its host plant was explored using stage-structured population models. Tussock moth dispersal occurs passively in first-instar larvae and is poor or absent in all other life stages. Spatial surveys suggested, however, that moth distribution is not well explained by passive dispersal; moth populations were greater on small patches and on isolated ones. Further analysis showed that several local demographic rates varied significantly with patch characteristics. Two mortality factors in particular may explain the observed patterns. First, crawler mortality both increased with patch size and was density-dependent. A single-patch difference equation model showed mortality related to patch size is strong enough to overcome the homogenizing effect of density dependence; greater equilibrium densities were predicted for smaller patches. Second, although three rates were found to vary with local patch density, only pupal parasitism by a chalcid wasp could potentially account for higher moth abundances on isolated patches. A spatially explicit simulation model of the multiple-patch system showed that spatial variation in pupal parasitism is indeed strong enough to generate such a pattern. These results demonstrate that habitat spatial structure can affect multiple population processes simultaneously, and even relatively low attack rates imposed on a reproductively valuable life stage of the host can have a dominant effect on population distribution among habitat patches.     

Characterization of contamination in and toxicities of a shipyard area in Hong Kong

This is the first integrated study on the contaminant characterization and toxicities of a shipyard area. This site in Hong Kong contained 3.6-33.4 mg kg(-1) dichlorodiphenyltrichloroethane and 5-79 g kg(-1) oil and grease. Other pollutants exceeding the Dutch intervention values were total polyaromatic hydrocarbons, total petroleum hydrocarbons, and metals Cu, Pb and Zn. These pollutants persisted partially owing to the poor fertility with <125 mg N kg(-1) and <530 mg P kg(-1) typical of coastal soil. Sediments collected within 100 m also showed contamination exceeding the China and Hong Kong intervention levels. The shipyard soil killed two bacteria Pseudomonas stutzeri and Acinetobacter sp. isolated from a clean coastal soil, inhibited germination of three exogenous plants Triticum aestivum, Brassica chinense and Lolium perenne, and inhibited proliferation of three indigenous bacteria: Methylobacterium sp., Pseudomonas aeruginosa and Bacillus cereus. Thus, ex situ remediation was needed.     

Carbonyl emissions from commercial cooking sources in Hong Kong

Cooking fumes are an important carbonyl emission source, especially in a highly urbanized city, such as Hong Kong. Cooking exhaust from 15 commercial kitchens of a variety of cooking styles was sampled and analyzed for a suite of 13 carbonyl compounds. Carbonyl compositions were varied among the different cooking styles. Formaldehyde was generally the most abundant carbonyl, and its contribution to the total carbonyl amount on a molar basis ranged from 12 to 60%. Acrolein was also found to be an abundant carbonyl in the cooking exhaust. The highest contribution by acrolein to the total carbonyls was found to be 30% in the exhaust of a western-style steak restaurant. Long-chain saturated carbonyls, that is, heptanal, octanal, and nonanal, accounted for a significant fraction (> 40%) of the total carbonyls in kitchens that always used heated cooking oils. Two dicarbonyls, glyoxal and methylglyoxal, had a various presence in the cooking emissions, ranging from negligible to 10%. The presence of benzaldehyde and tolualdehyde was mostly negligible in the sampled kitchen exhaust. Annual emission rates of both individual carbonyls and total carbonyls were estimated for various types of commercial kitchens. Local-style fast-food shops contributed the highest total carbonyl emissions per year mainly because of the large number of this kind of restaurant in Hong Kong. The citywide annual emission rates of the three most toxic carbonyls, formaldehyde, acetaldehyde, and acrolein, were estimated assuming that the limited number of sampled restaurants were representative of the average restaurants. Such estimates of carbonyl emission rates were comparable to the estimated carbonyl emissions from vehicular sources, suggesting the importance of commercial cooking as a source for carbonyls in Hong Kong.     

Effects of Electron-Beam Irradiation and Ultraviolet Light (365 nm) on Polylactic Acid Plastic Films

Strips of Ca-I [polylactic acid (PLA) monolayer plastic films from Cargill Dow Polymers LLC, Minnetonka, MN] cut in the machine and nonmachine directions were irradiated with an electron beam using a CIRCLE III Linear Accelerator (MeV Industries S.A., Jouy-en-Josas, Cedex, France). The effects of 33-kGy irradiation on the physical properties of the Ca-I strips were studied. In addition, the effects of ultraviolet (UV) light (365-nm) illumination on the degradation of three PLA plastic films, Ch-I (PLA monolayer plastic films from Chronopol, Golden, CO), GII (PLA trilayer plastic films from Cargill Dow Polymers LLC), MN), and Ca-I (PLA monolayer plastic films from Cargill Dow Polymers LLC) were analyzed by a modified ASTM D5208-91 method. Results showed that irradiation had decreased the weight-average molecular weight (M _w), stress at break, percentage of elongation, and strain energy of Ca-I by 35.5, 26.7, 32.3, and 44.8%, respectively (P < 0.01). The shelf life of the irradiated Ca-I strips at 5°C and <20 ± 5% RH was about 6 months. The degradation rate of Ch-I, GII, and Ca-I with no UV light treatment at 55°C and 10% RH was 2512, 5618, and 3785 M _w/week, respectively. Under the UV light illumination (365 nm), the degradation rate of Ch-I, GII, and Ca-I, was 2982, 8722, and 7467 M _w/week, respectively. Hence, the degradation rate of GII and Ca-I was increased 55 and 97% by UV light (P < 0.008), respectively. This trend was not observed in Ch-I because its starting M _w (78,000 g/mol) was close to the tensile strength lost range (50,000 to 75,000 g/mol) of PLA films. To our knowledge, this is the first study to demonstrate that UV light does further enhance the degradation of PLA films.     

Synthesis and characterisation of potassium polytitanate for photocatalytic degradation of crystal violet

Potassium titanate nanostructures were synthesised by hydrothermal treatment of TiO2 （P25） in KOH and H2O2. As-produced powders were characterised by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption-desorption methods. Longitudinally-oriented-wire-like structures with a length up to several micrometres and diameters ranging from 10 to 30 nm were obtained. Larger size fibrous nanowires resulting from the hydrotherrnal treatment showed high affinity in adsorbing crystal violet （CV）, which was mainly due to their high surface area. The photocatalytic bleaching of CV solution revealed that the wires are photoactive under ultraviolet light irradiation. Macroporous nanowires are considered as effective adsorbents of CV, capable of photocatalvtic degradation, and they can be easily separated from the solution by settling.