scholarly journals Global ground strike point characteristics in negative downward lightning flashes – part 1: Observations

2021 ◽  
Author(s):  
Dieter R. Poelman ◽  
Wolfgang Schulz ◽  
Stephane Pedeboy ◽  
Dustin Hill ◽  
Marcelo Saba ◽  
...  
Keyword(s):  
High Speed ◽  
Geometric Mean ◽  
Time Interval ◽  
Data Sets ◽  
Time Intervals ◽  
High Speed Video ◽  
Video Recordings ◽  
The World ◽  
Multiple Stroke ◽  
Interval Value

Abstract. Lightning properties of a total of 1174 negative downward lightning flashes are analyzed. The high-speed video recordings are taken in different regions around the world, including Austria, Brazil, South Africa and USA, and are analyzed in terms of flash multiplicity, duration, interstroke intervals and ground strike point (GSP) properties. Although the results vary among the data sets, the analysis reveals that a third of the flashes are single-stroke events, while the overall mean number of strokes per flash equals 3.67. From the video imagery an average of 1.56 GSPs per flash is derived, with about 60 % of the multiple stroke flashes striking ground in more than one place. It follows that the channel creating a GSP is re-used by a factor of 2.3. Multiple-stroke flashes last on average 371 ms, whereas the geometric mean (GM) interstroke interval value preceding strokes producing a new GSP is about 18 % greater than the GM value preceding subsequent strokes following a pre-existing channel. In addition, a positive correlation between the duration and multiplicity of the flash is presented. The characteristics of the subset of flashes exhibiting multiple GSPs is further examined. It follows that strokes with stroke order of two create a new GSP in 60 % of the cases, while this percentage quickly drops for higher order strokes. Further, the possibility to form a new channel to ground in terms of the number of strokes that conditioned the previous channel shows that approximately 88 % developed after the occurrence of only one stroke. Investigating the time intervals in the other 12 % of the cases when two or more strokes re-used the previous channel showed that the average interstroke time interval preceding a new channel is found to be more than twice the time difference between strokes that follow the previous channel.

scholarly journals Global ground strike point characteristics in negative downward lightning flashes – Part 1: Observations

2021 ◽  
Vol 21 (6) ◽  
pp. 1909-1919
Author(s):  
Dieter R. Poelman ◽  
Wolfgang Schulz ◽  
Stephane Pedeboy ◽  
Dustin Hill ◽  
Marcelo Saba ◽  
...  
Keyword(s):  
High Speed ◽  
Risk Estimation ◽  
Contact Point ◽  
Geometric Mean ◽  
Time Interval ◽  
Data Sets ◽  
Video Recordings ◽  
Lightning Channel ◽  
The Usa ◽  
Multiple Stroke

Abstract. Information about lightning properties is important in order to advance the current understanding of lightning, whereby the characteristics of ground strike points (GSPs) are in particular helpful to improving the risk estimation for lightning protection. Lightning properties of a total of 1174 negative downward lightning flashes are analyzed. The high-speed video recordings are taken in different regions, including Austria, Brazil, South Africa and the USA, and are analyzed in terms of flash multiplicity, duration, interstroke intervals and ground strike point properties. According to our knowledge this is the first simultaneous analysis of GSP properties in different regions of the world applying a common methodology. Although the results vary among the data sets, the analysis reveals that a third of the flashes are single-stroke events, while the overall mean number of strokes per flash equals 3.67. From the video imagery an average of 1.56 GSPs per flash is derived, with about 60 % of the multiple-stroke flashes striking the ground in more than one place. It follows that a ground contact point is struck 2.35 times on average. Multiple-stroke flashes last on average 371 ms, whereas the geometric mean (GM) interstroke interval value preceding strokes producing a new GSP is about 18 % greater than the GM value preceding subsequent strokes following a pre-existing lightning channel. In addition, a positive correlation between the duration and multiplicity of the flash is presented. The characteristics of the subset of flashes exhibiting multiple GSPs is further examined. It follows that strokes with a stroke order of 2 create a new GSP in 60 % of the cases, while this percentage quickly drops for higher-order strokes. Further, the possibility of forming a new lightning channel to ground in terms of the number of strokes that conditioned the previous lightning channel shows that approximately 88 % developed after the occurrence of only one stroke. Investigating the time intervals in the other 12 % of the cases when two or more strokes re-used the previous lightning channel showed that the average interstroke time interval preceding a new lightning channel is found to be more than twice the time difference between strokes that follow the previous lightning channel.

Water skating in the larvae of dixella aestivalis (Diptera) and hydrobius fuscipes (Coleoptera)

1999 ◽  
Vol 202 (7) ◽  
pp. 845-853
Author(s):  
J. Brackenbury
Keyword(s):  
High Speed ◽  
The Body ◽  
Water Interface ◽  
Body Movements ◽  
Chironomid Larvae ◽  
High Speed Video ◽  
Adhesive Organ ◽  
Video Recordings ◽  
Air Water Interface

The kinematics of locomotion was investigated in the aquatic larvae of Dixella aestivalis and Hydrobius fuscipes with the aid of high-speed video recordings. Both insects are able to skate on the surface of the water using the dorso-apical tracheal gill as an adhesive organ or ‘foot’. Progress relies on the variable adhesion of the foot between ‘slide’ and ‘hold’ periods of the locomotory cycle. The flexural body movements underlying skating in D. aestivalis can be derived directly from the figure-of-eight swimming mechanism used in underwater swimming. The latter is shown to be similar to figure-of-eight swimming in chironomid larvae. This study shows how the deployment of a ‘foot’ enables simple side-to-side flexural movements of the body to be converted into effective locomotion at the air-water interface.

scholarly journals Debunking the viper's strike: harmless snakes kill a common assumption

2016 ◽  
Vol 12 (3) ◽  
pp. 20160011 ◽  
Author(s):  
David A. Penning ◽  
Baxter Sawvel ◽  
Brad R. Moon
Keyword(s):  
High Speed ◽  
Past Century ◽  
Loss Of Consciousness ◽  
Common Assumption ◽  
Motor Responses ◽  
High Speed Video ◽  
The Past ◽  
Venomous Snakes ◽  
Video Recordings ◽  
Very High

To survive, organisms must avoid predation and acquire nutrients and energy. Sensory systems must correctly differentiate between potential predators and prey, and elicit behaviours that adjust distances accordingly. For snakes, strikes can serve both purposes. Vipers are thought to have the fastest strikes among snakes. However, strike performance has been measured in very few species, especially non-vipers. We measured defensive strike performance in harmless Texas ratsnakes and two species of vipers, western cottonmouths and western diamond-backed rattlesnakes, using high-speed video recordings. We show that ratsnake strike performance matches or exceeds that of vipers. In contrast with the literature over the past century, vipers do not represent the pinnacle of strike performance in snakes. Both harmless and venomous snakes can strike with very high accelerations that have two key consequences: the accelerations exceed values that can cause loss of consciousness in other animals, such as the accelerations experienced by jet pilots during extreme manoeuvres, and they make the strikes faster than the sensory and motor responses of mammalian prey and predators. Both harmless and venomous snakes can strike faster than the blink of an eye and often reach a target before it can move.

Terrestrial locomotion in the black-billed magpie: kinematic analysis of walking, running and out-of-phase hopping

2000 ◽  
Vol 203 (14) ◽  
pp. 2159-2170 ◽  
Author(s):  
M. Verstappen ◽  
P. Aerts ◽  
R. Van Damme
Keyword(s):  
Kinematic Analysis ◽  
High Speed ◽  
Bird Species ◽  
Pica Pica ◽  
Terrestrial Locomotion ◽  
High Speed Video ◽  
Video Recordings ◽  
Flexion Extension

The inter-limb kinematic patterns of walking, running and out-of-phase hopping in black-billed magpies (Pica pica) were studied using high-speed video recordings. The flexion/extension patterns of the joints were similar between the gait types, suggesting that the within-leg control of the angular excursions is similar. This result is further supported by the fact that running and hopping are alternative gaits at speeds higher than walking; however, magpies show a preference for hopping. Moreover, only small differences occur between the kinematic patterns of the two limbs during out-of-phase hopping, during which the legs are believed to have different functions. The hindlimb kinematic patterns of magpies are like those of other flying and more terrestrial bird species; however, striking differences are found in comparison with humans at the level of the internal angles. This is probably due to the differences in the morphology and configuration of their legs.

EXPLORATORY STUDY ON AIRBAG SUITABILITY FOR LOW ENGINE CAPACITY MOTORCYCLES

2016 ◽  
Vol 78 (4) ◽  
Author(s):  
Aqbal Hafeez Ariffin ◽  
Mohd Syazwan Solah ◽  
Azhar Hamzah ◽  
Mohd Hafzi Md Isa ◽  
Zulhaidi Mohd Jawi ◽  
...  
Keyword(s):  
Exploratory Study ◽  
High Speed ◽  
Side Impact ◽  
Test Results ◽  
Passenger Cars ◽  
High Speed Video ◽  
Video Recordings ◽  
Motorcycle Crashes ◽  
Crash Tests ◽  
Engine Capacity

Motorcyclist constituted more than 50% of road deaths in Malaysia. Statistics showed that most fatal motorcyclist crashes involved passenger cars: with sideswipe or side impact reported to be the most frequent crash configurations. Many related studies have been performed to completely understand such motorcycle crashes which resulted in many safety inventions. These include installation of airbag onto motorcycle to study its effectiveness in potentially reducing motorcyclist’s injury. However, previous related studies known mainly dealt airbag’s effectiveness for large cc motorcycles. Hence, an exploratory study was conducted to study airbag’s suitability in mitigating rider’s injury during collision for motorcycle with low engine capacity (cc). Two different full-scale crash tests of motorcycle (with and without mounted airbag) side-impacting passenger car were conducted in accordance to ISO 13232. The test results in terms of high-speed video recordings (crash kinematics), motorcycle damage profiles and dummy injuries were analysed and discussed. It could be suggested from the results obtained that an airbag system for low cc motorcycle is feasible and further study is needed for better airbag concept and design which could reduce motorcyclist injury during collision.

Symbiotic interactions between ciliates (Ciliophora) and diatoms (Bacillariophyceae)

2020 ◽  
Vol 68 (1) ◽  
Author(s):  
Fernando Gomez
Keyword(s):  
High Speed ◽  
Living Organism ◽  
Free Living ◽  
Symbiotic Associations ◽  
High Speed Video ◽  
Video Recordings ◽  
Morphological Adaptations ◽  
Obligate Mutualism ◽  
Vorticella Oceanica ◽  
Tropical Sea

Introduction: Diatoms and ciliates are important components of the marine plankton community, and some species are able to develop symbiotic associations in the tropical seas. Objective: To describe the nature of the symbioses, the morphological adaptations of the members, and the possible ecological advantages of the symbiotic life versus the free-living forms. Methods: Plankton samples were collected from Mediterranean and Caribbean Seas, and the South Atlantic Ocean. Consortia were examined during laboratory incubations, including studies of the motility and the feeding currents by high-speed video recordings, and culture tests of the species as symbiotic or free-living forms. Results: The consortia of the diatoms Chaetoceros dadayi and C. tetrastichon with the tintinnid Eutintinnus spp., and C. coarctatus with the peritrich ciliate Vorticella oceanica are examples of an obligate mutualism. The cultures of the host diatoms as free-living organism were unsuccessful. The consortia between Eutintinnus lususundae and the diatoms Chaetoceros peruvianus, Hemiaulus hauckii, H. membranaceus, and Thalassionema sp. are facultative symbioses. These are examples of three or four partner consortia because Hemiaulus spp. is the host of the diazotrophic cyanobacteria Richelia intracellularis. Other example of facultative three partner consortium is the peritrich ciliate Zoothamnium pelagicum with an ectobiont bacteria, and the diatom Licmophora sp. The barrel-shaped chains of the diatom Fragilariopsis dolious encircled the lorica of Salpingella spp., while these chains were almost flat in the free-living stage. The peritrich ciliate Pseudovorticella coscinodisci lives on large pelagic diatoms such as Coscinodiscus and Palmerina. These symbioses are facultative for the diatoms, but they extended their survival under unfavorable conditions. High-speed video recordings of the consortium of Vorticella oceanica and Chaetoceros coarctatus revealed that during the stalk contraction the zooid of reached 5 400 body length s-1, being the fastest organism with respect to its size. The consortia of Chaetoceros densus and an undescribed species of Vorticella is re-discovered. Conclusions: These symbioses have allowed that the sessile peritric ciliates colonize the pelagic environment and the proliferation of diatoms with a polar origin in the tropical sea.

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