Characterizing three types of negative narrow bipolar events in thunderstorms

© 2019 The Authors Data from fast antennas (FAs)with bandwidth of 16 Hz–2.5 MHz and VHF power sensors (Log-RF)with bandwidth of 186–192 MHz are used to examine negative narrow bipolar events, or NNBEs. The main focus is on low-altitude (8.0 km)NNBEs are also examined. The low-altitude NNBEs are found to have two types called NNBE(L)and NNBE(H). NNBE(L)s have a bipolar FA waveform typical of NBEs while NNBE(H)s have a unipolar FA waveform. It is hypothesized that NNBE(H)s may be weak versions of NNBE(L)s in which the second, overshoot part of the bipolar waveform is too weak to detect amid the FA sensor noise. Together the 33 NNBE(L)s and NNBE(H)s occurred at an average altitude of 6.2 km (range 4.6–7.8 km), had average range-normalized (to 100 km)amplitude of 0.4 V/m (range 0.06–1.5 V/m), and had average VHF power of 130 W (range 1–1300 W). These low-altitude NNBE properties are substantially smaller and weaker than the same properties of the high-altitude NNBEs and of positive NBEs that initiate intracloud (IC)flashes; these analyses indicate that -CG flashes are easier to initiate than IC flashes. Visual inspection of the FA and Log-RF data of 868 -CG flashes showed that only 33 flashes (4%)were preceded by either an NNBE(L)or NNBE(H), so 96% of the -CG flashes investigated probably did not begin with an NNBE

A study of lightning flash initiation prior to the first initial breakdown pulse

© 2018 The Authors This study examines the initiation of two intracloud (IC) and two cloud-to-ground (CG) lightning flashes using electric field change (FA) sensors and VHF (LogRF) sensors located at seven sites near Oxford, Mississippi, USA. For each flash the initiating event caused a pulse in the LogRF data and started an Initial E-Change (IEC) in the FA data. The initiating LogRF pulses had powers ~1 μs. Numerous LogRF pulses occurred during each IEC; these pulses had durations ≤3 μs. Fewer FA pulses occurred during each IEC; these pulses had durations of ≤7 μs. During each IEC, a few of the LogRF pulses were coincident with a FA pulse, and most such pairs of pulses enhanced the IEC; no IEC enhancing events occurred without such a coincident pair. Each flash had 1 or 2 IEC enhancing events soon after the initiating event and 1 or 2 enhancing events shortly before the first classic initial breakdown (IB) pulse occurred. The point dipole moments and durations of IECs of the two IC flashes were (–520C m, 620 μs) and (–770C m, 1790 μs) and for the two CG flashes were (9C m, 124 μs) and (36C m, 130 μs). We speculate that the LogRF events were positive corona streamers, that enhancing events occurred when a new streamer extended a previous streamer path, and that this process during the flash initiation developed a nascent channel needed for the negative breakdown of the IB pulses

A science plan for carbon cycle research in North American coastal waters. Report of the Coastal CARbon Synthesis (CCARS) community workshop, August 19-21, 2014

Workshop held August 19-21, 2014, Woods Hole, MARelative to their surface area, continental margins represent some of the largest carbon fluxes in the global ocean, but sparse and sporadic sampling in space and time makes these systems difficult to characterize and quantify. Recognizing the importance of continental margins to the overall North American carbon budget, terrestrial and marine carbon cycle scientists have been collaborating on a series of synthesis, carbon budgeting, and modeling exercises for coastal regions of North America, which include the Gulf of Mexico, the Laurentian Great Lakes (LGL), and the coastal waters of the Atlantic, Pacific, and Arctic Oceans. The Coastal CARbon Synthesis (CCARS) workshops and research activities have been conducted over the past several years as a partner activity between the Ocean Carbon and Biogeochemistry (OCB) Program and the North American Carbon Program (NACP) to synthesize existing data and improve quantitative assessments of the North American carbon budget.The authors of this science plan wish to acknowledge the generous support of NASA (NNX10AU78G) and NSF (OCE-1107285) for all of the CCARS activities, including a kickoff meeting (December 2010), a series of regional workshops (Atlantic coast, Gulf of Mexico, Pacific coast), and the final community workshop (August 2014)

CAG repeat expansion in Huntington disease determines age at onset in a fully dominant fashion

Objective: Age at onset of diagnostic motor manifestations in Huntington disease (HD) is strongly correlated with an expanded CAG trinucleotide repeat. The length of the normal CAG repeat allele has been reported also to influence age at onset, in interaction with the expanded allele. Due to profound implications for disease mechanism and modification, we tested whether the normal allele, interaction between the expanded and normal alleles, or presence of a second expanded allele affects age at onset of HD motor signs. Methods: We modeled natural log-transformed age at onset as a function of CAG repeat lengths of expanded and normal alleles and their interaction by linear regression. Results: An apparently significant effect of interaction on age at motor onset among 4,068 subjects was dependent on a single outlier data point. A rigorous statistical analysis with a wellbehaved dataset that conformed to the fundamental assumptions of linear regression (e.g., constant variance and normally distributed error) revealed significance only for the expanded CAG repeat, with no effect of the normal CAG repeat. Ten subjects with 2 expanded alleles showed an age at motor onset consistent with the length of the larger expanded allele. Conclusions: Normal allele CAG length, interaction between expanded and normal alleles, and presence of a second expanded allele do not influence age at onset of motor manifestations, indicating that the rate of HD pathogenesis leading to motor diagnosis is determined by a completely dominant action of the longest expanded allele and as yet unidentified genetic or environmental factors. Copyright © 2012 by AAN Enterprises, Inc