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Simultaneous data from two interferometers separated by 16 km and synchronized within 100 ns was collected for a thunderstorm near Langmuir Lab on October 23, 2018. Analysis via triangulation follo...

In this paper we report the first close, high-resolution observations of downward-directed terrestrial gamma-ray flashes (TGFs) detected by the large-area Telescope Array cosmic ray observatory, obtained in conjunction with broadband VHF interferometer and fast electric field change measurements of the parent discharge. The results show that the TGFs occur during strong initial breakdown pulses (IBPs) in the first few milliseconds of negative cloud-to-ground and low-altitude intracloud flashes, and that the IBPs are produced by a newly-identified streamer-based discharge process called fast negative breakdown. The observations indicate the relativistic runaway electron avalanches (RREAs) responsible for producing the TGFs are initiated by embedded spark-like transient conducting events (TCEs) within the fast streamer system, and potentially also by individual fast streamers themselves. The TCEs are inferred to be the cause of impulsive sub-pulses that are characteristic features of classic IBP sferics. Additional development of the avalanches would be facilitated by the enhanced electric field ahead of the advancing front of the fast negative breakdown. In addition to showing the nature of IBPs and their enigmatic sub-pulses, the observations also provide a possible explanation for the unsolved question of how the streamer to leader transition occurs during the initial negative breakdown, namely as a result of strong currents flowing in the final stage of successive IBPs, extending backward through both the IBP itself and the negative streamer breakdown preceding the IBP., Comment: Typo fixed and reference added. Manuscript is 36 pages. Supplemental Information is 42 pages. This paper is to be published in the Journal of Geophysical Research: Atmospheres. Online data repository: Open Science Framework DOI: 10.17605/OSF.IO/Z3XDA

VHF radiation sources produced by positive breakdown during lightning discharges are generally considered to be both weak and slowly propagating. However, as VHF lightning mapping systems have become more sensitive, even this weak radiation can be mapped. In addition to being a faint process, positive breakdown often produces bursts of energetic activity. During the bursts, the VHF emission is extremely bright, and the breakdown propagates at much higher speeds. Here we present VHF interferometric and time–of–arrival measurements of such fast positive breakdown events produced during three example flashes. Electric field change measurements show that the fast breakdown process carries positive charge. The extent and velocity of the breakdown is estimated by converting the angular source locations provided by the interferometer into Cartesian coordinates using 3-dimensional lightning mapping observations of the flash as a guide. Fast positive breakdown events are found to extend 100–2400 m into virgin air beyond the tip of the preceding positive leader, at speeds of 0.9–9 ×107 m s−1. The observations expand upon earlier observations of such breakdown [Shao et al., 1995]“ and are similar to recently-reported results that fast positive breakdown is the cause of high-power narrow bipolar events (NBEs) [Rison et al., 2016].

Simple Summary Acting to preserve biodiversity can involve harming individual animals. It has recently been argued that conventional practice has placed too much emphasis on the preservation of collective entities, such as populations and species, at the expense of suffering for individuals. At least some advocates of the ‘Compassionate Conservation’ movement find any deployment of lethal measures in the interests of conservation to be unacceptable. This shifts the balance of priorities too far. While conservationists have a duty to minimise harm, and to use non-lethal measures where feasible, there will be serious implications for conservation if this movement were to be widely influential. Furthermore, the ‘do-no-harm’ maxim the compassionate conservationists advocate does not always promote the welfare of individual animals. Abstract Human activity affecting the welfare of wild vertebrates, widely accepted to be sentient, and therefore deserving of moral concern, is widespread. A variety of motives lead to the killing of individual wild animals. These include to provide food, to protect stock and other human interests, and also for sport. The acceptability of such killing is widely believed to vary with the motive and method. Individual vertebrates are also killed by conservationists. Whether securing conservation goals is an adequate reason for such killing has recently been challenged. Conventional conservation practice has tended to prioritise ecological collectives, such as populations and species, when their interests conflict with those of individuals. Supporters of the ‘Compassionate Conservation’ movement argue both that conservationists have neglected animal welfare when such conflicts arise and that no killing for conservation is justified. We counter that conservationists increasingly seek to adhere to high standards of welfare, and that the extreme position advocated by some supporters of ‘Compassionate Conservation’, rooted in virtue ethics, would, if widely accepted, lead to considerable negative effects for conservation. Conservation practice cannot afford to neglect consequences. Moreover, the do-no-harm maxim does not always lead to better outcomes for animal welfare.

Terrestrial Gamma-ray flashes (TGFs) are bursts of gamma-rays initiated in the Earth’s atmosphere by atmospheric lightning. The Terrestrial Gamma-ray flashes discussed in this work were detected at ground level between 2014 and 2018, by the Telescope Array Surface Detector (TASD), a lightning mapping array installed in 2013, and a broadband interferometer and fast sferics sensor installed in 2018. The TASD is a 700 square kilometer ultra high energy cosmic ray detector in the southwestern desert of Utah, U.S.A. It is composed of 507 (3 square meter) plastic scintillator detectors on a 1.2 km square grid. In 2013, a Lightning Mapping Array (LMA) detector and a Slow antenna (SA) were installed at the TASD site. The LMA is a three-dimensional total lightning location system, comprised of nine stations located within and around the TASD array. The SA records the electric field change in lightning discharges. The TASD has become one of the world leading instruments for detection of TGFs from the ground. The downward Gamma-ray showers observed by the TASD detector were all confined to the first 1-2 ms of intracloud and cloud to ground discharges, spanning an overall duration of several hundreds of microseconds. We hypothesize that the observed TGFs are similar to those detected by satellites, but that the TASD ground-based observations are able to detect both the temporal distribution at the source and the full footprint of the gamma shower on the ground. More importantly, the gamma ray bursts observations suggest that the TGFs were produced by one or two particularly energetic leader steps at the initial breakdown pulse (IBP) stage. To confirm such correspondence, an interferometer (INTF) and a fast antenna were installed a few kilometers east of the TASD detector on July 2018. With these additional lightning detection instruments in concert with the TASD cosmic ray observatory, LMA, and SA, we are able, to present, for the first time, observations of the TGFs clearly associated with the IBPs of downward cloud-to-ground flashes and intracloud flashes. This result sheds new light on the origins of Terrestrial Gamma-ray Flashes.

The Telescope Array Surface Detector (TASD) in western Utah is designed for the measurement of Ultra-High-Energy Cosmic Rays (UHECRs) with characteristically low flux. During its ten years of operation, however, TASD recorded at least 24 bursts of gamma-ray showers, each consisting of two or more TASD events within a single millisecond of lightning activity. After implementation of specialized lightning detectors, the bursts were further correlated with lightning leaders preceding each stroke. We conclude that these bursts are downward Terrestrial Gamma Flashes (TGFs), similar to those observed by satellite. These data constitute the majority of all data on such events recorded from the ground. We are recreating observations using Geant4 simulations to better understand the properties of downward TGFs and the acceptance statistics of TASD. Acceleration mechanisms, for example, are poorly understood. Spectra from models such as Relativistic Runaway Electron Avalanche (RREA) and Fast Negative Breakdown (FNB) are used to generate a detector response to replicate empirical properties, especially the unique waveform timing and footprints seen at TASD. This also helps characterize the TASD acceptance and aperture for TGFs in a manner similar to cosmic ray studies.

Two sprite-producing thunderstorms were observed on 8 and 25 June 2012 in northeastern Colorado by a combination of low-light cameras, a lightning mapping array, polarimetric and Doppler radars, the National Lightning Detection Network, and charge moment change measurements. The 8 June event evolved from a tornadic hailstorm to a larger multicellular system that produced 21 observed positive sprites in 2 h. The majority of sprites occurred during a lull in convective strength, as measured by total flash rate, flash energy, and radar echo volume. Mean flash area spiked multiple times during this period; however, total flash rates still exceeded 60 min(sup 1), and portions of the storm featured a complex anomalous charge structure, with midlevel positive charge near 20degC. The storm produced predominantly positive cloud-to-ground lightning. All sprite-parent flashes occurred on the northeastern flank of the storm, where strong westerly upper level flow was consistent with advection of charged precipitation away from convection, providing a pathway for stratiform lightning. The 25 June event was another multicellular hailstorm with an anomalous charge structure that produced 26 positive sprites in less than 1 h. The sprites again occurred during a convective lull, with relatively weaker reflectivity and lower total flash rate but relatively larger mean flash area. However, all sprite parents occurred in or near convection and tapped charge layers in adjacent anvil cloud. The results demonstrate the sprite production by convective ground strokes in anomalously charged storms and also indicate that sprite production and convective vigor are inversely related in mature storms.

On the morning of 5 June 2013, two cameras of the SpriteCam network concurrently captured a red sprite with diffuse halo over a mesoscale convective system (MCS) passing the panhandle area of Oklahoma. This sprite was produced by a negative cloud-to-ground (CG) stroke with peak current of −103 kA in a manner different from previous observations in several aspects. First of all, the causative stroke of sprite is located by the National Lightning Detection Network (NLDN) in the trailing stratiform of MCS, instead of the deep convection typically for negative sprites. Second, the sprite-producing stroke was likely the first stroke of a multistroke negative CG flash (with ≥6 CG strokes) whose evolution was mainly confined in the lower part of thunderstorm; although the parent flash of sprite might contain relatively long in-cloud evolution prior to the first stroke, there is no evidence that the negative leader had propagated into the upper positive region of thundercloud as typically observed for the sprite-producing/class negative CG strokes. Third, as shown by the simulation with a two-dimensional full-wave electrodynamic model, although the impulse charge moment change (−190 C km) produced by the main stroke was not sufficient to induce conventional breakdown in the mesosphere, a second impulse charge transfer occurred with ~2 ms delay to cause a substantial charge transfer (−290 C km) so that the overall charge moment change (−480 C km) exceeded the threshold for sprite production; this is a scenario different from the typical case discussed by Li et al. (2012). As for the source of the second current pulse that played a critical role to produce the sprite, it could be an M component whose charge source was at least 9 km horizontally displaced from the main stroke or a negative CG stroke (with weak peak current for the return stroke) that was not detected by the NLDN.

The outcomes of species recovery programs have been mixed; high-profile population recoveries contrast with species-level extinctions. Each conservation intervention has its own challenges, but to inform more effective management it is imperative to assess whether correlates of wider recovery program success or failure can be identified. To contribute to evidence-based improvement of future conservation strategies, we conducted a global quantitative analysis of 48 mammalian recovery programs. We reviewed available scientific literature and conducted semistructured interviews with conservation professionals involved in different recovery programs to investigate ecological, management, and political factors associated with population recoveries or declines. Identifying and removing threats was significantly associated with increasing population trend and decreasing conservation dependence, emphasizing that populations are likely to continue to be compromised in the absence of effective threat mitigation and supporting the need for threat monitoring and adaptive management in response to new and potential threats. Lack of habitat and small population size were cited as limiting factors in 56% and 42% of recovery programs, respectively, and both were statistically associated with increased longer term dependence on conservation intervention, demonstrating the importance of increasing population numbers quickly and restoring and protecting habitat. Poor stakeholder coordination and management were also regularly cited by respondents as key weaknesses in recovery programs, indicating the importance of effective leadership and shared goals and management plans. Project outcomes were not influenced by biological or ecological variables such as body mass or habitat, which suggests that these insights into correlates of conservation success and failure are likely to be generalizable across mammals.

The upgraded VHF digital interferometer (VHF DITF) system is introduced which can continuously sample the radiation associated with lightning. A new processing technique was implemented which uses the distribution of slopes of the phase difference versus frequency to locate the radiation source. By using this technique, frequency components which are not due to lightning can be excluded and low as well as high amplitude sources are located. As a result, both positive breakdown and negative breakdown are located, and negative recoil leaders (recoil leaders) are visualized in great detail. The recoil leaders which continue into the positive charge region are seen to slow their propagation and dim their radiation as they cross the flash initiation region. Analysis of the relative received power of the different breakdown types, negative leaders, recoil leaders, and positive leaders, also can be made. In both the intracloud and cloud-to-ground flash, the modes of the distributions of received power for negative leaders, recoil leaders, and positive leaders were approximately the same. The brightest emissions seen from the positive leader were substantially lower than the brightest emission seen from the negative leader. The results also indicate that positive leaders as well as lower elevation negative leader emit more low frequency radiation than recoil leaders and high-elevation negative leaders. By continuously sampling the VHF waveform, the upgraded VHF DITF locates many weak sources which the previous system was not capable of locating.

The VHF Broadband Digital Interferometer developed by Osaka University has been improved to allow continuous sampling over the entire duration of a lightning flash and to utilize a generalized cross-correlation technique for determining the lightning source directions. Time series waveforms of 20-80 MHz signals received at three orthogonally located antennas are continuously digitized over multisecond intervals, as opposed to sequences of short-duration triggers. Because of the coherent nature of the measurements, radiation sources are located down into the ambient receiver and environmental noise levels, providing a quantum leap in the ability to study lightning discharge processes. When postprocessed using cross correlation, the measurements provide angular uncertainties less than 1 ! and time resolution better than 1!s. Special techniques have been developed to distinguish between actual lightning sources and noise events, with the result being that on the order of 50,000-80,000 radiation sources are located for a typical lightning flash. In this study, two-dimensional interferometer observations of a classic bilevel intracloud flash are presented and combined with three-dimensional Lightning Mapping Array observations to produce a quasi 3-D map of lightning activity with the time resolution of the interferometer. As an example of the scientific utility of the observations, results are presented for the 3-D progression speed of negative leaders associated with intracloud K-leaders.

[1] The temporal and spatial development of sprite-producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system (MCS) on 29 June 2011 near the Oklahoma Lightning Mapping Array (LMA). Sprites produced by a total of 26 lightning flashes were observed simultaneously on video from Bennett, Colorado and Hawley, Texas, enabling a triangulation of sprites in comparison with temporal development of parent lightning (in particular, negatively charged stepped leaders) in three-dimensional space. In general, prompt sprites produced within 20 ms after the causative stroke are less horizontally displaced (typically 30 km). However, both prompt and delayed sprites are usually centered within 30 km of the geometric center of relevant LMA sources (with affinity to negative stepped leaders) during the prior 100 ms interval. Multiple sprites appearing as dancing/jumping events associated with a single lightning flash could be produced either by distinct strokes of the flash, by a single stroke through a series of current surges superposed on an intense continuing current, or by both. Our observations imply that sprites elongated in one direction are sometimes linked to in-cloud leader structure with the same elongation, and sprites that were more symmetric were produced above the progression of multiple negative leaders. This suggests that the large-scale structure of sprites could be affected by the in-cloud geometry of positive charge removal. Based on an expanded dataset of 39 sprite-parent flashes by including more sprites recorded by one single camera over the same MCS, the altitude (above mean sea level, MSL) of positively charged cloud region tapped by sprite-producing strokes declined gradually from ~10 km MSL (−35°C) to around 6 km MSL (−10°C) as the MCS evolved through the mature stage. On average, the positive charge removal by causative strokes of sprites observed on 29 June is centered at 3.6 km above the freezing level or at 7.9 km above ground level.

[1] We report and analyze 3 years of lightning impulse charge moment change (iCMC) measurements obtained from an automated, real time lightning charge moment change network (CMCN). The CMCN combines U.S. National Lightning Detection Network (NLDN) lightning event geolocations with extremely low frequency (≲1 kHz) data from two stations to provide iCMC measurements across the entire United States. Almost 14 million lightning events were measured in the 3 year period. We present the statistical distributions of iCMC versus polarity and NLDN-measured peak current, including corrections for the detection efficiency of the CMCN versus peak current. We find a broad distribution of iCMC for a given peak current, implying that these parameters are at best only weakly correlated. Curiously, the mean iCMC does not monotonically increase with peak current, and in fact, drops for positive CG strokes above +150 kA. For all positive strokes, there is a boundary near 20 C km that separates seemingly distinct populations of high and low iCMC strokes. We also explore the geographic distribution of high iCMC lightning strokes. High iCMC positive strokes occur predominantly in the northern midwest portion of the U.S., with a secondary peak over the gulf stream region just off the U.S. east coast. High iCMC negative strokes are also clustered in the midwest, although somewhat south of most of the high iCMC positive strokes. This is a region far from the locations of maximum occurrence of high peak current negative strokes. Based on assumed iCMC thresholds for sprite production, we estimate that approximately 35,000 positive polarity and 350 negative polarity sprites occur per year over the U.S. land and near-coastal areas. Among other applications, this network is useful for the nowcasting of sprite-producing storms and storm regions.

This paper is a personal view, deriving from the knowledge base of the Arabian Peninsula’s fauna, the record on re-introduction of Arabian Oryx and Houbara Bustard, and selective conservation actions for the region’s species, to propose an ambitious vision for restoring the region’s key ecosystems through re-wilding, a holistic approach for biodiversity conservation. It is argued that the need is urgent and the time is right, and that various circumstances and opportunities are now favourable. The prospect is for the Arabian Peninsula to maintain its roles as home to specialised species, to continue to act as a sanctuary and crossroads for species from three major neighbouring biological realms, and to be a potential refuge in the face of climate change.

Blue jets, gigantic jets, cloud-to-cloud discharges and cloud-to-ground lightning are all electrical discharges from thunderclouds. An analysis of numerical simulations and observations of these phenomena places them all in a unifying framework. Thunderstorms occasionally produce upward discharges, called blue jets and gigantic jets, that propagate out of the storm top towards or up to the ionosphere1,2,3,4. Whereas the various types of intracloud and cloud-to-ground lightning are reasonably well understood, the cause and nature of upward discharges remains a mystery. Here, we present a combination of observational and modelling results that indicate two principal ways in which upward discharges can be produced. The modelling indicates that blue jets occur as a result of electrical breakdown between the upper storm charge and the screening charge attracted to the cloud top; they are predicted to occur 5–10 s or less after a cloud-to-ground or intracloud discharge produces a sudden charge imbalance in the storm. An observation is presented of an upward discharge that supports this basic mechanism. In contrast, we find that gigantic jets begin as a normal intracloud discharge between dominant mid-level charge and a screening-depleted upper-level charge, that continues to propagate out of the top of the storm. Observational support for this mechanism comes from similarity with ‘bolt-from-the-blue’ discharges5 and from data on the polarity of gigantic jets6. We conclude that upward discharges are analogous to cloud-to-ground lightning. Our explanation provides a unifying view of how lightning escapes from a thundercloud.

The Milu (Père David’s deer, Elaphurus davidianus) became extinct in China in the early 20th century but was reintroduced to the country. The reintroduced Milu escaped from a nature reserve and dispersed to the south of the Yangtze River. We monitored these accidentally escaped Milu from 1995 to 2012. The escaped Milu searched for vacant habitat patches as “stepping stones” and established refuge populations. We recorded 122 dispersal events of the escaped Milu. Most dispersal events occurred in 1998, 2003, 2006 and 2010. Milu normally disperse in March, July and November. Average dispersal distance was 14.08 ± 9.03 km, with 91.41% shorter than 25 km. After 5 generations, by the end of 2012, 300 wild Milu were scattered in refuge populations in the eastern and southern edges of the Dongting Lake. We suggest that population density is the ultimate cause for Milu dispersal, whereas floods and human disturbance are proximate causes. The case of the Milu shows that accidentally escaped animals can establish viable populations; however, the dispersed animals were subject to chance in finding “stepping stones”. The re-wilded Milu persist as a meta-population with sub-populations linked by dispersals through marginal habitats in an anthropogenic landscape.

Since 1998, Los Alamos National Laboratory (LANL) has deployed an array of fast electric field change sensors in New Mexico and Florida in support of LANL’s satellite lightning observations. In April 2004, all the sensors were significantly upgraded and improved, and a new array was deployed in north-central Florida. This paper describes the operations of the new array and reports the first 12 months of lightning observations. The new array is about 10 times more sensitive than the previous one and can capture millions of discharge events during a stormy day in Florida. In this paper, the array’s lightning location accuracy, minimum detectable peak current, and ratio of intracloud-to-cloud-to-ground flashes are analyzed. Some case studies that illustrate the storm evolution, lightning classification, and radar comparisons are presented. A new three-dimensional capability of the array is demonstrated.

The lightning data that are recorded with a three-dimensional lightning mapping array (LMA) are compared with data from an electric field change sensor (in this case a flat-plate antenna operated both as a “slow” and a “fast” antenna). The goal of these comparisons is to quantify any time difference that may exist between the initial responses of the two instruments to a lightning flash. The data consist of 136 flashes from two New Mexico thunderstorms. It is found that the initial radiation source detected by the LMA usually precedes the initial response of both the slow and fast antennas. In a small number of cases, the flat-plate antenna response precedes the initial LMA source, but by no more than 2 ms. The observations of such a close time coincidence suggest that the first LMA radiation source of each flash was located at or very near the flash-initiation point. Thus, the first LMA radiation source and the initial sequence of sources from a lightning flash can be used as remote sensing tools to give information about the magnitude of the electric field (relative to lightning-initiation thresholds) and the direction of the electric field at the initiation location.

The aim of this study was to review MRI findings of clinically suspected posterolateral corner knee injuries and their associated internal derangements. Sixteen knees in 15 patients who had evidence of a posterolateral corner knee injury on the physical exam underwent MRI to evaluate the posterolateral corner of the knee and to look for associated injuries. Two musculoskeletal radiologists reviewed the scans. Surgery was performed on 10 of the knees. Tibial plateau fractures were present in 6 knees; 5 of the fractures were anteromedial rim tibial plateau fractures. The popliteus muscle was injured in 13 knees and the biceps femoris in 6 knees. The lateral collateral ligament was ruptured in 12 knees. The posterior cruciate ligament was completely ruptured in 7 knees and avulsed from its tibial attachment in 1 knee. Eleven knees had a complete anterior cruciate ligament rupture. The anterior cruciate ligament was edematous without complete disruption of all fibers in 3 knees. There was excellent correlation between the MRI results and operative results in regard to the presence of a posterolateral corner injury of the knee (9 of the 10 knees had a posterolateral corner injury). In our study MRI readily detected posterolateral corner injuries. Posterolateral corner injuries of the knee are frequently associated with a variety of significant injuries, including cruciate ligament tears, meniscus tears, and fractures. Fractures of the peripheral anteromedial tibial plateau are not common; however, given their relatively common occurrence in this study, they may be an indicator of a posterolateral corner injury to the knee.

During the summer of 2000, the Severe Thunderstorm Electrification and Precipitation Study (STEPS) program deployed a three-dimensional Lightning Mapping Array (LMA) near Goodland, Kansas. Video confirmation of sprites triggered by lightning within storms traversing the LMA domain were coordinated with extremely low frequency (ELF) transient measurements in Rhode Island and North Carolina. Two techniques of estimating changes in vertical charge moment (Mq) yielded averages of ;800 and ;950 C km for 13 sprite-parent positive polarity cloud-to-ground strokes (1CGs). Analyses of the LMA’s very high frequency (VHF) lightning emissions within the two mesoscale convective systems (MCSs) show that 1CGs did not produce sprites until the centroid of the maximum density of lightning radiation emissions dropped from the upper part of the storm (7‐11.5 km AGL) to much lower altitudes (2‐5 km AGL). The average height of charge removal (Zq) from 15 sprite-parent 1CGs during the late mature phase of one MCS was 4.1 km AGL. Thus, the total charges lowered by spriteparent 1CGs were on the order of 200 C. The regional 08C isotherm was located at about 4.0 km AGL. This suggests a possible linkage between sprite-parent CGs and melting-layer/brightband charge production mechanisms in MCS stratiform precipitation regions. These cases are supportive of the conceptual MCS spriteproduction models previously proposed by two of the authors (Lyons and Williams).

A variety of storm top electrical discharges have been observed using several types of low-light imagers, film, and the human eye. Recently, a video recorded an unprecedented, bright blue upward discharge from a tropical thunderstorm top near Puerto Rico. The event reached the base of the ionosphere. The horizontal dimensions of cloud top discharges can range from 100 m to several kilometers. Upward extents vary from 100 m to 70 km. Shapes include “points” of light, upwardly flaring trumpets, and narrow, vertical, lightning-like channels, some topped with expanding blue, flame-like features. Visual appearances range from brilliant white lightning-like channels to a grainy, almost particulate appearing jets of dim blue light, and sometimes as a blue flame within which a brilliant white channel appears. The classical blue jet is at the lower limit of human night vision whereas some upward discharges have been clearly seen during daylight. Cloud top “pixies” last no longer than 16.7 ms, whereas upward lightn...

The outcomes of species recovery programs have been mixed; high-profile population recoveries contrast with species-level extinctions. Each conservation intervention has its own challenges, but to inform more effective management it is imperative to assess whether correlates of wider recovery program success or failure can be identified. To contribute to evidence-based improvement of future conservation strategies, we conducted a global quantitative analysis of 48 mammalian recovery programs. We reviewed available scientific literature and conducted semistructured interviews with conservation professionals involved in different recovery programs to investigate ecological, management, and political factors associated with population recoveries or declines. Identifying and removing threats was significantly associated with increasing population trend and decreasing conservation dependence, emphasizing that populations are likely to continue to be compromised in the absence of effective threat mitigation and supporting the need for threat monitoring and adaptive management in response to new and potential threats. Lack of habitat and small population size were cited as limiting factors in 56% and 42% of recovery programs, respectively, and both were statistically associated with increased longer term dependence on conservation intervention, demonstrating the importance of increasing population numbers quickly and restoring and protecting habitat. Poor stakeholder coordination and management were also regularly cited by respondents as key weaknesses in recovery programs, indicating the importance of effective leadership and shared goals and management plans. Project outcomes were not influenced by biological or ecological variables such as body mass or habitat, which suggests that these insights into correlates of conservation success and failure are likely to be generalizable across mammals.

A digital broadband interferometer (INTF), based on a system developed at Osaka University [1], but with an upgraded streaming digitizer system, has been deployed at Langmuir Laboratory for the past four summers. The upgraded system allows lightning to be located continuously in time over a broad range of source powers. The data are processed using a cross correlation based algorithm and further enhanced using maximum likelihood windowing functions. The resulting 2D images are highly detailed, having sub-microsecond time resolution as well as good angular resolution that allow the development of positive and negative leaders to be examined in detail. Continuously radiating events such as K-changes and dart leaders are imaged in their entirety, and impulsive events associated with stepping can be isolated in time. The continuous INTF is a highly complementary instrument to the New Mexico Tech Mapping Array (LMA). The LMA locates impulsive VHF radiation events accurately in 3D with up to 10 microsecond time resolution, while the INTF locates both continuous and impulsive radiating events with sub-microsecond resolution in 2D. The combined datasets provide more complete observations and understanding of lightning processes than obtained by either system alone. Ambiguities in the interferometer data arising from sources moving towards or away from the interferometer are removed. The timing resolution of the LMA is improved to that of the interferometer. Continuously radiating emissions such as K-changes and dart leaders can be mapped in 3D. The combined continuous INTF and LMA system is proving to be a very powerful tool for the study of lightning electrical breakdown processes. A number of previously unobserved phenomena have been discovered using the INTF. Of significant importance is the observation of fast (5 × 107 m/s) positive breakdown which radiates strongly in the VHF. Fast positive streamers, about 500 m long, are often observed as the first event in a lightning flash, and may be the mechanism which initiates lightning. Fast positive breakdown, typically several kilometers long, is also observed following return strokes of negative CG ashes, propagating into regions of previously un-ionized air.

Summary Coiled-tubing drilling (CTD) has thrived in recent years on the North Slope of Alaska. To date, CTD has sidetracked more than 250 wells in a continuous program of activity since 1995. In that time, Alaska has become a proving ground for CTD tools and techniques. CTD has matured into a highly efficient and economical means of sidetracking wells on the North Slope. Key reasons for the success of the program include continuous use, which allows rapid learning; a culture of technical innovation; effective performance-based service contracts; the right people with the right expertise; and the vision and support of senior management. This paper summarizes the performance improvements realized in North Slope CTD operations, detailing how the tools and techniques have changed. Applying new technologies and improving existing tools are major levers of CTD progress. Major performance improvement areas include window milling, bottomhole assembly (BHA) reliability, and lost circulation. Reliability improvements in equipment and persistent innovation will continue to fuel CTD's underlying economic performance in Alaska. Included in this paper is a discussion of the remaining problems associated with through-tubing, slim-hole drilling with CTD technology. Examples of new CTD technologies being used or about to be implemented in Alaska will also be presented.

Confusion in the interpretation of standard-speed video observations of optical flashes above intense cloud-to-ground lightning discharges has persisted for a number of years. New high-speed (3000 frames per second) image-intensified video recordings are used along with theoretical modeling to elucidate the optical signatures of elves and sprites. In particular, a brief diffuse flash sometimes observed to accompany or precede more structured sprites in standard-speed video is shown to be a normal component of sprite electrical breakdown and to be due entirely to the quasi-electrostatic thundercloud field (sprites), rather than the lightning electromagnetic pulse (elves). These “sprite halos” are expected to be produced by large charge moment changes occurring over relatively short timescales (∼1 ms), in accordance with their altitude extent of ∼70 to 85 km. The relatively short duration of this upper, diffuse component of sprites makes it difficult to detect and to discriminate from elves and Rayleigh-scattered light using normal-speed video systems. Modeled photometric array signatures of elves and sprites are contrasted and shown to be consistent with observations. Ionization in the diffuse portion of sprites may be a cause of VLF scattering phenomena known as early/fast VLF events.

On August 14, 1998, 3 separate daytime sprite events were detected via a unique extremely low frequency (ELF) sprite signature. The onset of the sprite ELF signatures was delayed by 11.0–13.2 ms from positive cloud-to-ground strokes which had attained exceptionally large charge moment (charge times height) changes of 3900–6100 C·km. It is shown that a charge moment change of 6100 C·km may have been sufficient for conventional breakdown at ≃54 km altitude, assuming an experimentally measured ion conductivity profile of Holzworth et al., [1985]. The daytime sprites themselves contained unusually large charge moment changes of ≃2800 C·km, ≃1200 C·km, and ≃910 C·km.

High altitude air breakdown, manifested as “red sprites,” is reported in close association with negative cloud-to-ground lightning (−CG) on at least two occasions above an unusual storm on August 29, 1998. Data from high speed photometry, low-light-level video, and receivers of lightning electromagnetic signatures in the frequency range 10 Hz to 20 kHz are used to establish the association and indicate that the causative −CG discharges effected unusually large vertical charge moment changes (ΔMQv) of up to 1550 C · km in 5 ms. The existence of sprites caused by −CG's, rather than the regularly associated +CG's, has immediate implications for sprite models and observations.

We analyze synchronized high speed video images and ELF-VLF radio emissions from 11 sprite clusters observed on 6 October 1997. Quantitative analysis shows that vertical lightning charge moment changes of 150–1100 C · km occurred before the optical emissions reached their peak with delays of 2–11 ms from the lightning discharge. This threshold unexpectedly decreases with increasing delay from parent lightning to peak emissions. We also find that sprite charge moment change and minimum sprite altitude are not well correlated with the vertical charge moment change in the parent discharge. These observations do not agree well with present sprite generation models, and we suggest that streamer development and horizontal lightning charge motion can play a significant role in sprite generation.

High speed video of sprites show that they are typically initiated at an altitude of about 75 km and usually develop simultaneously upwards and downwards from the point of origin with an initial columniform shape. The initial development of sprites appears to be dominated by corona streamers with velocities in excess of 107 m/s. Many of the observed characteristics are consistent with a conventional breakdown mechanism for both sprite initiation and initial sprite development.

Observations of radio emissions from thunderstorms were made during the summer of 1996 using two arrays of sensors located in northern New Mexico. The first array consisted of three fast electric field change meters separated by distances of 30 to 230 km. The second array consisted of three broadband (3 to 30 MHz) HF data acquisition systems separated by distances of 6 to 13 km. Differences in signal times of arrival at multiple stations were used to locate the sources of received signals. Relative times of arrival of signal reflections from the ionosphere and Earth were used to determine source heights. A distinct class of short-duration electric field change emissions was identified and characterized. The emissions have previously been termed narrow positive bipolar pulses (NPBPs). NPBPs were emitted from singular intracloud discharges that occurred in the most active regions of three thunderstorms located in New Mexico and west Texas. The discharges occurred at altitudes between 8 and 11 km above mean sea level. NEXRAD radar images show that the NPBP sources were located in close proximity to high reflectivity storm cores where reflectivity values were in excess of 40 dBZ. NPBP electric field change waveforms were isolated, bipolar, initially positive pulses with peak amplitudes comparable to those of return stroke field change waveforms. The mean FWHM (full width at half maximum) of initial NPBP field change pulses was 4.7 μs. The HF emissions associated with NPBPs were broadband noise-like radiation bursts with a mean duration of 2.8 μs and amplitudes 10 times larger than emissions from typical intracloud and cloud-to-ground lightning processes. Calculations indicate that the events represent a distinct class of singular, isolated lightning discharges that have limited spatial extents of 300 to 1000 m and occur in high electric field regions. The unique radio emissions produced by these discharges, in combination with their unprecedented physical characteristics, clearly distinguish the events from other types of previously observed thunderstorm electrical processes.

[1] We report observations of two negative polarity gigantic jets sufficiently near very high‐frequency (VHF) lightning mapping networks that the associated lightning characteristics and charge transfer could be investigated. In both cases the gigantic jet‐producing flash began as ordinary intracloud lightning with upper level channels attempting to exit the cloud, and then produced the upward gigantic jet. Neither flash had developed channels to ground, confirming that the major charge transfer during gigantic jets occurred between the cloud and ionosphere. The leader progression of one event was detected at altitudes above 20 km, demonstrating the possibility of detecting and tracking the propagation of negative jets above the cloud with VHF techniques. Citation: Lu, G., et al. (2011), Lightning development associated with two negative gigantic jets, Geophys. Res. Lett., 38, L12801

The chlorination of a series of α,β-unsaturated ketones and esters by Cl2 in CH3OH, with and without acid scavengers such as N-chlorosuccinimide (NCS), pyridine and 2,6-lutidine, is described. Methyl vinyl ketone and cyclohex-2-enone have also been chlorinated in ethanol. Mixtures of Markovnikov(M) and anti-Markovnikov(AM) methoxy chlorides and dichlorides are formed in most cases; phenyl vinyl ketone gives no M products in the absence of pyridine, M methoxy chloride is not formed with (E-)-4-chlorobut-3-en-2-one under any conditions, pyridine has no effect on the product ratios and methyl 3-chlorobut-2-enoate forms only dichloride. Chlorination of the ketones in the presence of the pyridines results in a significant increase in the M regioisomer (except for methyl isopropenyl ketone and the ketones mentioned), giving M:AM ratios which are similar to the corresponding esters. Ratios for the esters are not affected significantly by pyridine. We ascribe the effect of the pyridine bases to the elimination of acid and the acid-catalysed mechanism, permitting the chlorination to occur via a carbon–carbon π-bond (chloronium ion) mechanism. The rate of chlorination of methyl vinyl ketone is retarded by pyridine but is still considerably faster than methyl acrylate. NCS, in contrast to N-bromosuccinimide (NBS) reported previously, has no effect on the M:AM ratio. The chlorination of methyl vinyl ketone with NCS and HCl gives markedly different results from Cl2.

[1] A two-dimensional axisymmetric model of charge relaxation in the conducting atmosphere is used in conjunction with a probabilistic lightning model to demonstrate how realistic cloud electrodynamics lead to the development of blue and gigantic jets. The model accounts for time-dependent conduction currents and screening charges formed under the influence of the thundercloud charge sources. Particular attention is given to numerical modeling of the screening charges near the cloud boundaries. The modeling results demonstrate the important role of the screening charges in local enhancement of the electric field and/or reduction of net charge in the upper levels of the thundercloud. The charge relaxation model presented in this work confirms the previous results obtained with a simpler model by Krehbiel et al. (2008), specifically that the accumulation of screening charges near the thundercloud top produces a charge configuration leading to the initiation of blue jets, while the effective mixing of these charges with the upper thundercloud charge may lead to the formation of gigantic jets.

The syntheses of the orthogonally protected N 3 -(carboxymethyl)-2,3-L-diaminopropanoic acids 18, 19, and 20 and O-(carboxymethyl)-L-serines 35 and 38 are described. All of the diaminopropanoic acids were prepared via reductive amination of the known oxazolidine aldehyde 9. The carboxymethyl serines were prepared via O-alkylation of N-CBZ-L-serine. To enable incorporation of these amino acids into cyclic peptides, protecting group schemes were designed for compatibility with either Boc or Fmoc solid-phase peptide synthesis

The chlorination of a series of α,β-unsaturated ketones and esters by Cl2 in CH3OH, with and without acid scavengers such as N-chlorosuccinimide (NCS), pyridine and 2,6-lutidine, is described. Methyl vinyl ketone and cyclohex-2-enone have also been chlorinated in ethanol. Mixtures of Markovnikov(M) and anti-Markovnikov(AM) methoxy chlorides and dichlorides are formed in most cases; phenyl vinyl ketone gives no M products in the absence of pyridine, M methoxy chloride is not formed with (E-)-4-chlorobut-3-en-2-one under any conditions, pyridine has no effect on the product ratios and methyl 3-chlorobut-2-enoate forms only dichloride. Chlorination of the ketones in the presence of the pyridines results in a significant increase in the M regioisomer (except for methyl isopropenyl ketone and the ketones mentioned), giving M:AM ratios which are similar to the corresponding esters. Ratios for the esters are not affected significantly by pyridine. We ascribe the effect of the pyridine bases to the elimination of acid and the acid-catalysed mechanism, permitting the chlorination to occur via a carbon–carbon π-bond (chloronium ion) mechanism. The rate of chlorination of methyl vinyl ketone is retarded by pyridine but is still considerably faster than methyl acrylate. NCS, in contrast to N-bromosuccinimide (NBS) reported previously, has no effect on the M:AM ratio. The chlorination of methyl vinyl ketone with NCS and HCl gives markedly different results from Cl2.

Emerging real-time capabilities using sensitive ULF/ELF/VLF magnetic receivers can monitor the impulse charge moment changes (iΔMq) of cloud-to-ground lightning strokes (CGs) over large regions. This provides a means to detect the parent CGs of the most common of the transient luminous events (TLEs) – sprites (often preceded by halos.) As iΔMq values grow larger than 100 C km, +CGs have a rapidly increasing probability of producing mesospheric sprites. If the iΔMq value of a +CG is >300 C km, there is a >75–80% chance this CG stroke initiates a sprite. Curiously, while negative iΔMq values of this size are much less common, they do occur. Yet on only a rare occasions have –CGs been documented to initiate a sprite over continental stroms (the so-called polarity paradox). The total charge moment change required to initiate sprites is believed to be at least ∼500 C km. Also, the great majority of sprite initiations are delayed after the return stroke by much more than the 2 ms time period used in the iΔMq estimates. This suggests that while both positive and negative CGs may have relatively large iΔMq values, due to the relatively low amperage continuing currents in the negative discharges, only +CGs have large enough continuing currents to routinely reach breakdown values and initiate sprites. While both CG polarities can theoretically initiate sprites, perhaps a somewhat higher breakdown threshold may exist for –CGs, and/or reduced streamer development makes them more difficult to detect optically? Preliminary climatologies of iΔMq for the U.S. are presented. The technique employed in the U.S. utilizes the National Lightning Detection Network for geolocation, allowing placement of >80–90% of sprite parent +CGs. Global lightning location systems such as the Worldwide Lightning Location Network (WWLLN) appear to detect approximately 25% of the CGs producing U.S. sprites, suggesting the possibility of employing such systems elsewhere.

[1] Characteristics of lightning flashes in three storms are compared to simultaneous electric field (E) measurements at various altitudes to examine three hypotheses. The first is the idea that horizontal lightning branches propagate at altitudes near potential extrema (or wells). The analyses show that horizontal lightning activity and potential extrema are coincident in time and altitude, and so are consistent with the idea that lightning moves charges into potential wells as a means of using a storm's electrostatic energy to drive a lightning flash's dielectric breakdown processes. Second, these data are used to verify the usual interpretation of breakdown polarity of lightning radiation sources detected by the Lightning Mapping Array. The third hypothesis investigated is that normal cloud-to-ground flashes have a period of preliminary breakdown if and only if a potential well for negative charge exists between the altitudes of flash initiation and ground. The analyses show that in 14 flashes when a low-level well was indicated, the period of preliminary breakdown before the first return stroke lasted an average of 117 ms, considerably longer than the average lifetime of a stepped leader. In 15 flashes in which no low-level well was indicated, the time between initiation and first return stroke averaged 15 ms.

[1] Atmospheric electric field change (sferic) waveforms were detected at Los Alamos Sferic Array stations in association with terrestrial gamma-ray flashes (TGFs). Five TGF sferic waveforms detected at sufficiently close range were all found to be consistent with a positive-polarity intracloud (+IC) discharge process which transported electrons upward. The amplitudes of the events were among the top 5% of IC discharge flashes. Altitudes obtained from ionosphere reflections for two of the closer events were found to be 13.6 km and 11.5 km. These altitudes are lower than expected if one assumes that the sferic was near the source of the gamma-rays. One of the sferics was an energetic narrow bipolar event which occurred near the inferred onset of a flash, suggesting that the preceding TGF may correspond to the actual onset.

[1] We report observations and analysis of 30 kHz radio emissions (sferics) from lightning discharges associated with 26 terrestrial gamma ray flashes (TGFs) recorded by the RHESSI satellite over the Caribbean and Americas, between 1500 and 4000 km away from the magnetic field sensors located at Duke University. Thirteen of the TGFs are found to occur within −3/+1 ms of lightning discharges of positive polarity from the direction of the RHESSI subsatellite point, strongly indicating that the TGFs are linked to these discharges. The event timing and sferic direction finding reveals that the discharges occur within a ∼300 km radius circle around the RHESSI subsatellite point. Although the positive polarity of all 13 discharges is consistent with runaway breakdown, the lightning charge moment changes are approximately two orders of magnitude smaller than present high altitude runaway breakdown theory predicts. Implications of these measurements are discussed.

Concentrations of large numbers of endemic species have been singled out in prioritization exercises as significant areas for global biodiversity conservation. This paper describes bird and mammal endemicity in Indo-Pacific ecoregions. An ecoregion is a relatively large unit of land or water that contains a distinct assemblage of natural communities. We prioritize 133 ecoregions according to their levels of endemicity, and explain how variables such as biome type, whether the ecoregion is on an island or continental mass, montane or non-montane, correlate with the proportion of the total species assemblage that are endemic. Following an exploratory principal components analysis we classify all ecoregions according to the relationship between numbers of endemics and overall species richness. Endemicity is negatively correlated with species richness. We show that plotting the logit transformation of the endemicity of birds and mammals against log of species richness is a more effective and useful way of identifying important ecoregions than simply ordering ecoregions by the proportion of endemic species, or any other single measure. The plot, divided into 16 regions corresponding to the quartiles of the two variables, was used to identify ecoregions of high conservation value. These are the ecoregions with the highest endemicity and lowest species richness. Further analysis shows that island and montane ecoregions, regardless of their biome type, are by far the most important for endemic species.

The purpose of this study was to provide clinical and radiographic evaluation after a minimum of two years in patients who had an anterior cervical corpectomy and a fibular allograft strut. Nineteen patients returned for a follow-up visit which included independent radiographic evaluation as well as completing a Visual Analogue Scale and Oswestry and Short-Form 36 questionnaires. The categories of fusion were as follows: 1) definitely fused (84%) 2) questionably fused (11%) 3) definitely not fused (5%). The average VAS was 29 mm (range 0-85). The Oswestry Back Scores showed relatively low levels of significant pain with an average score of 29 (range 0-73). Anterior cervical corpectomy followed by an allograft fibular strut provides for relatively high rates of arthrodesis without severe loss of height or sagittal alignment at long term radiographic follow-up.

For over a century, numerous undocumented reports have appeared about unusual large-scale luminous phenomena above thunderclouds1,2,3,4,5,6 and, more than 80 years ago, it was suggested that an electrical discharge could bridge the gap between a thundercloud and the upper atmosphere7,8. Since then, two classes of vertically extensive optical flashes above thunderclouds have been identified—sprites9,10,11 and blue jets12,13,14. Sprites initiate near the base of the ionosphere, develop very rapidly downwards at speeds which can exceed 107 m s-1 (ref. 15), and assume many different geometrical forms16,17,18,19. In contrast, blue jets develop upwards from cloud tops at speeds of the order of 105 m s-1 and are characterized by a blue conical shape12,13,14. But no experimental data related to sprites or blue jets have been reported which conclusively indicate that they establish a direct path of electrical contact between a thundercloud and the lower ionosphere. Here we report a video recording of a blue jet propagating upwards from a thundercloud to an altitude of about 70 km, taken at the Arecibo Observatory, Puerto Rico. Above an altitude of 42 km—normally the upper limit for blue jets and the lower terminal altitude for sprites—the flash exhibited some features normally observed in sprites. As we observed this phenomenon above a relatively small thunderstorm cell, we speculate that it may be common and therefore represent an unaccounted for component of the global electric circuit.