Anti-TTL monoclonal antibody, clone 4H6

The spatial distribution of relative humidity with respect to ice (RHI) in the boreal wintertime tropical tropopause layer (TTL, similar or equal to 14-18km) over the Pacific is examined with the measurements provided by the NASA Airborne Tropical TRopopause EXperiment. We also compare the measured RHI distributions with results from a transport and microphysical model driven by meteorological analysis fields. Notable features in the distribution of RHI versus temperature and longitude include (1) the common occurrence of RHI values near ice saturation over the western Pacific in the lower to middle TTL; (2) low RHI values in the lower TTL over the central and eastern Pacific; (3) common occurrence of RHI values following a constant mixing ratio in the middle to upper TTL (temperatures between 190 and 200K); (4) RHI values typically near ice saturation in the coldest airmasses sampled; and (5) RHI values typically near 100% across the TTL temperature range in air parcels with ozone mixing ratios less than 50ppbv. We suggest that the typically saturated air in the lower TTL over the western Pacific is likely driven by a combination of the frequent occurrence of deep convection and the predominance of rising motion in this region. The nearly constant water vapor mixing ratios in the middle to upper TTL likely result from the combination of slow ascent (resulting in long residence times) and wave-driven temperature variability. The numerical simulations generally reproduce the observed RHI distribution features, and sensitivity tests further emphasize the strong influence of convective input and vertical motions on TTL relative humidity.

Distributed Denial of Service (DDoS) attacks are one of the prominent network security attacks. In DDoS attack several machines send large amount of network traffic to the victim using spoofed IP address. Unfortunately there is no reliable technique to detect spoofed IP packets. In this paper we argue that, a proactive detection of spoofed IP packets will help in predicting DDoS attacks. In this paper we describe an event based detection method to identify spoofed IP packets. Our method works by proactively probing received packets for genuineness. Active probing technique uses inconsistencies in TTL values of received packets to decide whether the first packet was spoofed or genuine. We enumerate several possible spoofing scenarios with our detection method in place and identify its type based on the response to probing. Further, we study limitations of event based method and discuss ways to overcome those. We design and experiment with all spoofing scenarios in a real network setup and report the results. With few optimizations done to the probing strategy, the overhead incurred can be minimized considerably, which makes the proposed technique useful for detecting DDoS attacks. (C) 2017 Published by Elsevier Ltd.