ECOSYSTEMS CAN BE MODELED AT MANY different hierarchical levels. The phenomenon being simulated has a context represented by the next higher level of ecosystem organization, as well as driving mechanisms represented by the next lower level of ecosystem organization. In this sense, the level at which mechanisms are represented in models of tree crowns depends on the crown attributes or processes...

Inundative releases of beneÞcial insects are frequently used to suppress pest insects but not commonly attempted as amethod of weed biological control because of the difÞculty in obtaining the required large numbers of insects. The successful establishment of a ßea beetle complex, mixed Aphthona lacertosa (Rosenhauer) and Aphthona nigriscutus Foundras (87 and 13%, respectively), for the control...

Sixteen lipophilic N-(X)sulfonyl carbamoyl lariat ethers with polyether ring sizes of 12-crown-4, 14-crown-4, 15-crown-5, and 18-crown-6 are utilized for competitive alkali metal cation extractions from aqueous solutions into chloroform. Variation of the electron-withdrawing properties of X in the series of methyl, phenyl, 4-nitrophenyl, and trifluoromethyl allows the influence of the acidity o...

The effects of the interaction between the operational sex ratio (OSR) and a resource (i.e. oviposition site) on mating dynamics have rarely been considered. We examined the effect of the resource presence and its interaction, with the effect of OSR on copulation duration in Rhagoletis juglandis, a tephritid fly species characterized by a resource-defence mating system in which males defend ter...

Segregation distorters located on sex chromosomes are predicted to sweep to fixation and cause extinction via a shortage of one sex, but in nature they are often found at low, stable frequencies. One potential resolution to this longstanding puzzle involves female multiple mating (polyandry). Because many meiotic drivers severely reduce the sperm competitive ability of their male carriers, fema...

Inundative releases of beneficial insects are frequently used to suppress pest insects but not commonly attempted as a method of weed biological control because of the difficulty in obtaining the required large numbers of insects. The successful establishment of a flea beetle complex, mixed Aphthona lacertosa (Rosenhauer) and Aphthona nigriscutus Foundras (87 and 13%, respectively), for the con...

Coleoid cephalopod molluscs comprise squid, cuttlefish and octopuses, and represent nearly the entire diversity of modern cephalopods. Sophisticated adaptations such as the use of colour for camouflage and communication, jet propulsion and the ink sac highlight the unique nature of the group. Despite these striking adaptations, there are clear parallels in ecology between coleoids and bony fish...

The British Columbian Ministry of Forests proposed an auction design to achieve fair market prices for its standing timber. Because the Crown owns almost all the standing timber in British Columbia, the Ministry proposed to auction a portion of that timber, and use the auction prices to set stumpage rates for timber under long-term tenure. In this manner, the private industry, and not the Crown...

Logistic regression equations predicting the probability that a tree will die from natural causes-insects, diseases, intertree competition-within 10 years have been developed for California red fir (Abies magnifica) and white fir (A. concolor). The equations, like those with a 5-year prediction period already developed for these species, are based on analysis of crown and bole characteristics o...

BACKGROUND/AIM Few studies have assessed the incidence and risk factors to crown fractures in preschool children. The aim of this study was to estimate the incidence of crown fracture in the primary dentition over a 1-year follow-up period, identify risk factors, and test the hypothesis that children with previous crown fracture are more prone to experience further cases of crown fracture indep...