Mosquitoes are exceptional in their ability to pierce into human skin with a natural ultimate painless microneedle, named fascicle. Here the structure of the Aedes albopictus mosquito fascicle is obtained using a Scan...Mosquitoes are exceptional in their ability to pierce into human skin with a natural ultimate painless microneedle, named fascicle. Here the structure of the Aedes albopictus mosquito fascicle is obtained using a Scanning Electron Microscope (SEM), and the whole process of the fascicle inserting into human skin is observed using a high-speed video imaging technique. Direct measurements of the insertion force for mosquito fascicle to penetrate into human skin are reported. Results show that the mosquito uses a very low force (average 18 μN) to penetrate into the skin. This force is at least three orders of magnitude smaller than the reported lowest insertion force for an artificial microneedle with an ultra sharp tip to insert into the human skin. In order to understand the piercing mechanism of mosquito fascicle tip into human multilayer skin tissue, a numerical simulation is conducted to analyze the insertion process using a nonlinear finite element method. A good agreement occurs between the numerical results and the experimental measurements.展开更多
The architectural development of Acacia karroo conforms to Troll’s model. Growth of the branches is modular and sympodial with heteroblastic leaves on all long shoots of the tree, including the seedling. Axillary bud...The architectural development of Acacia karroo conforms to Troll’s model. Growth of the branches is modular and sympodial with heteroblastic leaves on all long shoots of the tree, including the seedling. Axillary buds tend to proliferate especially on flowering shoots where they form fascicles consisting of up to 10 inflorescences arranged in two parallel serial rows per leaf axil. Most axillary buds are sylleptic and basal buds which give rise to short shoots, each producing two to five cataphylls each season, but no flowers. Inflorescences are only produced on long shoots (modules) of the current season. After flowering the terminal part of the module aborts, trees are usually andromonoecious with capitate inflorescences containing 40 to 100 flowers each, with some male and some hermaphrodite. Some trees produce only male flowers. Anthesis in the same inflorescence, the same tree as well as amongst trees of the same community are synchronised and occur at intermittent intervals, each lasting three or more days at a time. Flowers are protogynous and pollen is produced in polyads, each consisting of 16 pollen grains. Ovaries contain 10 to 14 ovules each. The concave stigma has space for only one polyad which can fertilise all ovules in the ovary after a single pollination event. Fruit set is low with 0 to 10 fruits (pods) per inflorescence.展开更多
基金supported by the National Natural Science Foundation of China (No.10672035,No.90816025,No.10721062)SRFDP (No.20060141007)
文摘Mosquitoes are exceptional in their ability to pierce into human skin with a natural ultimate painless microneedle, named fascicle. Here the structure of the Aedes albopictus mosquito fascicle is obtained using a Scanning Electron Microscope (SEM), and the whole process of the fascicle inserting into human skin is observed using a high-speed video imaging technique. Direct measurements of the insertion force for mosquito fascicle to penetrate into human skin are reported. Results show that the mosquito uses a very low force (average 18 μN) to penetrate into the skin. This force is at least three orders of magnitude smaller than the reported lowest insertion force for an artificial microneedle with an ultra sharp tip to insert into the human skin. In order to understand the piercing mechanism of mosquito fascicle tip into human multilayer skin tissue, a numerical simulation is conducted to analyze the insertion process using a nonlinear finite element method. A good agreement occurs between the numerical results and the experimental measurements.
文摘The architectural development of Acacia karroo conforms to Troll’s model. Growth of the branches is modular and sympodial with heteroblastic leaves on all long shoots of the tree, including the seedling. Axillary buds tend to proliferate especially on flowering shoots where they form fascicles consisting of up to 10 inflorescences arranged in two parallel serial rows per leaf axil. Most axillary buds are sylleptic and basal buds which give rise to short shoots, each producing two to five cataphylls each season, but no flowers. Inflorescences are only produced on long shoots (modules) of the current season. After flowering the terminal part of the module aborts, trees are usually andromonoecious with capitate inflorescences containing 40 to 100 flowers each, with some male and some hermaphrodite. Some trees produce only male flowers. Anthesis in the same inflorescence, the same tree as well as amongst trees of the same community are synchronised and occur at intermittent intervals, each lasting three or more days at a time. Flowers are protogynous and pollen is produced in polyads, each consisting of 16 pollen grains. Ovaries contain 10 to 14 ovules each. The concave stigma has space for only one polyad which can fertilise all ovules in the ovary after a single pollination event. Fruit set is low with 0 to 10 fruits (pods) per inflorescence.
