On Khovanov's cobordism theory for su(3) knot homology

We reconsider the su(3) link homology theory defined by Khovanov in math.QA/0304375 and generalized by Mackaay and Vaz in math.GT/0603307. With some slight modifications, we describe the theory as a map from the planar algebra of tangles to a planar algebra of (complexes of) `cobordisms with seams' (actually, a `canopolis'), making it local in the sense of Bar-Natan's local su(2) theory of math.GT/0410495. We show that this `seamed cobordism canopolis' decategorifies to give precisely what you'd both hope for and expect: Kuperberg's su(3) spider defined in q-alg/9712003. We conjecture an answer to an even more interesting question about the decategorification of the Karoubi envelope of our cobordism theory. Finally, we describe how the theory is actually completely computable, and give a detailed calculation of the su(3) homology of the (2,n) torus knots.Comment: 49 page

The Role of Landscapes and Landmarks in Bee Navigation: A Review.

The ability of animals to explore landmarks in their environment is essential to their fitness. Landmarks are widely recognized to play a key role in navigation by providing information in multiple sensory modalities. However, what is a landmark? We propose that animals use a hierarchy of information based upon its utility and salience when an animal is in a given motivational state. Focusing on honeybees, we suggest that foragers choose landmarks based upon their relative uniqueness, conspicuousness, stability, and context. We also propose that it is useful to distinguish between landmarks that provide sensory input that changes ("near") or does not change ("far") as the receiver uses these landmarks to navigate. However, we recognize that this distinction occurs on a continuum and is not a clear-cut dichotomy. We review the rich literature on landmarks, focusing on recent studies that have illuminated our understanding of the kinds of information that bees use, how they use it, potential mechanisms, and future research directions

In situ transmission electron microscopy study on the epitaxial growth of CoSi2 on Si(111) at temperatures below 150 °C

We report an in situ transmission electron microscopy study on the epitaxial growth of CoSi2 on Si(111) from a 10-nm-thick amorphous mixture of Co and Si in the ratio 1:2 which was formed by codeposition of Co and Si near room temperature. Nuclei of CoSi2 are observed in the as-deposited film. These nuclei are epitaxial and extend through the whole film thickness. Upon annealing, these columnar epitaxial CoSi2 grains grow laterally at temperatures as low as 50 °C. The kinetics of this lateral epitaxial growth was studied at temperatures between 50 and 150 °C. The activation energy of the growth process is 0.8±0.1 eV

Thiamethoxam impairs honey bee visual learning, alters decision times, and increases abnormal behaviors.

Learning is important for honey bee fitness and the pollination services that they provide. Neonicotinoid pesticides impair learning, fitness, colony health, and pollination, but most studies on how they affect bee learning have focused on olfactory learning. We tested the effects of field realistic doses of 0.8 ng/bee and 1.34 ng/bee of the neonicotinoid pesticide, thiamethoxam (TMX), on bee visual learning. We adapted a T-maze bioassay and classically conditioned bees to associate sugar reward with a simulated flower color (blue or yellow light) in a choice assay. At 1.34 ng/bee, TMX significantly reduced correct choices in the final learning trial as compared to the control treatment. There was no TMX effect in our 1-h memory test. We found stronger effects on decision time and abnormal behaviors. TMX decreased bee decision times, a potential byproduct of induced hyperactivity since bees walked to make choices. Behaviors (falling, trembling, and rapid abnormal movements) were significantly increased by both TMX doses as compared to the control treatment. These results suggest that the effects of neonicotinoids on bee visual learning should be further studied and incorporated into Risk Assessment protocols

Combined nutritional stress and a new systemic pesticide (flupyradifurone, Sivanto®) reduce bee survival, food consumption, flight success, and thermoregulation.

Flupyradifurone (FPF, Sivanto®) is a new butenolide insecticide that, like the neonicotinoids, is a systemic nicotinic acetylcholine receptor (nAChR) agonist. However, FPF is considered bee-safe (according to standard Risk Assessment tests), and is thus a potential solution to the adverse effects of other pesticides on beneficial insects. To date, no studies have examined the impact of nutritional stress (decreased food diversity and quality) and FPF exposure on bee health although both stressors can occur, especially around agricultural monocultures. We therefore tested the effects of a field-realistic FPF concentration (4 ppm, FPFdaily dose = 241 ± 4 ng/bee/day, 1/12 of LD50) and nutritional stress (nectar with low-sugar concentrations) on honey bee (Apis mellifera L.) mortality, food consumption, thermoregulation, flight success (unsuccessful vs. successful), and flight ability (duration, distance, velocity). Flight and thermoregulation are critical to colony health: bees fly to collect food and reproduce, and they thermoregulate to increase flight efficiency and to rear brood. We studied the effects across seasons because seasonality can influence bee sensitivity to environmental stress. We demonstrate that, depending upon season and nutritional stress, FPF can reduce bee survival (-14%), food consumption (-14%), thermoregulation (-4%, i.e. hypothermia), flight success (-19%), and increase flight velocity (+13%). Because pesticide exposure and nutritional stress can co-occur, we suggest that future studies and pesticide risk assessments consider both seasonality and nutritional stress when evaluating pesticide safety for bees

Does the waggle dance help honey bees to forage at greater distances than expected for their body size?

A honey bee colony has been likened to an oil company. Some members of the company or colony prospect for valuable liquid resources. When these are discovered other group members can be recruited to exploit the resource. The recruitment of nestmates to a specific location where there is a patch of flowers should change the economics of scouting, that is, the search for new resource patches. In particular, communication is predicted to make scouting at longer distances worthwhile because a profitable resource patch, once discovered, will enhance the foraging not only of the discoverer but also of nestmates that can be directed to the patch. By virtue of having large colonies and dance communication, honey bees are predicted to be able to profitably scout, and hence forage, at greater distances from the nest than either solitary bees or social bees without communication. We test this hypothesis by first examining existing data on foraging distance to evaluate whether honey bees do indeed forage at greater distances than other bees given their body size. Second, we present a simple cost-benefit analysis of scouting which indicates that communication causes longer range scouting to be more profitable. Overall, our analyses are supportive, but not conclusive, that honey bees forage further than would be expected given their size and that the waggle dance is a cause of the honey bee's exceptional foraging range

Examining the identity of the post-80s generation in Hong Kong through Cantopop

published_or_final_versionMedia, Culture and Creative CitiesMasterMaster of Social Sciences in Media, Culture and Creative Citie