[1] High-speed video camera records, with a temporal resolution of 20 μs and a spatial resolution of 2.4 m per pixel, of a downward negative lightning flash that terminated on a 440 m high building are examined. The attachment process in this flash exhibited an unexpected behavior in that the downward leader tip connected to the lateral surface of the~400 m upward connecting leader (UCL) below its tip. It appears that the effect of the downward leader on the UCL is significant, while the effect of the UCL on the downward leader is negligible, except for the final 80 μs preceding the beginning of the first return stroke. The ratio of speeds of the downward leader and the UCL tends to decrease with time, ranging from 1.8 to 0.12, although the lower 80-100 m or so of the UCL were too faint to allow speed measurements.

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*Multicast is a common method for distributing audio and video over the Internet. Since receivers are heterogeneous in processing capability, network bandwidth, and requirements for video quality, a single multicast stream is usually insufficient. A common strategy is to use layered video coding with multiple multicast groups. In this scheme, a receiver adjusts its video quality by selecting the number of multicast groups, and thereby video layers, it receives. Implementing this scheme requires the receivers to decide when to join a new group or leave a subscribed group. This paper presents a new solution to the join/leave problem using ThinStreams. In ThinStreams, a single video layer is multicast over several multicast groups, each with identical bandwidth. ThinStreams separates the coding scheme (i.e., the video layers) from control (i.e., the multicast groups), helping to bound network oscillations caused by receivers joining and leaving high bandwidth multicast groups.This work evaluates the join/leave algorithms used in ThinStreams using simulations and preliminary experiments on the MBONE. It also addresses fairness among independent video broadcasts and shows how to prevent interference between them.

Although free proline accumulation is a well-documented phenomenon in many plants in response to a variety of environmental stresses, and is proposed to play protective roles, high intracellular proline content, by either exogenous application or endogenous over-production, in the absence of stresses, is found to be inhibitory to plant growth. We have shown here that exogenous application of proline significantly induced intracellular Ca(2+) accumulation in tobacco and calcium-dependent ROS production in Arabidopsis seedlings, which subsequently enhanced salicylic acid (SA) synthesis and PR genes expression. This suggested that proline can promote a reaction similar to hypersensitive response during pathogen infection. Other amino acids, such as glutamate, but not arginine and phenylalanine, were also found to be capable of inducing PR gene expression. In addition, proline at concentration as low as 0.5 mM could induce PR gene expression. However, proline could not induce the expression of PDF1.2 gene, the marker gene for jasmonic acid signaling pathway. Furthermore, proline-induced SA production is mediated by NDR1-dependent signaling pathway, but not that mediated by PAD4. Our data provide evidences that exogenous proline, and probably some other amino acids can specifically induce SA signaling and defense response.