Efficient high-voltage protection in the electric catfish

2021 ◽  
Vol 224 (4) ◽  
pp. jeb239855 ◽  
Author(s):  
Georg Welzel ◽  
Stefan Schuster
Keyword(s):  
High Voltage ◽  
High Speed ◽  
Ancient Egypt ◽  
Protective Mechanisms ◽  
Sensorimotor Processing ◽  
Degree Of Protection ◽  
Electric Shocks ◽  
Involuntary Muscle Contraction ◽  
Species Specific ◽  
Rule Out

ABSTRACTFor thousands of years, starting with detailed accounts from ancient Egypt, the African electric catfish (Malapteruridae) has been renowned for its ability to hunt and to defend itself with powerful electric shocks. Surprisingly, the degree to which electric catfish are protected against their own or external electric shocks, how specific any protection would be to the species-specific waveform and whether a discharging catfish has to actively prepare for the onset of its high-voltage discharges has never been analysed. Here, we used digital high-speed video to record catfish during their own discharges or as they were exposed to external discharges, employing goldfish to carefully calibrate the efficiency of all discharges. Electric catfish show a remarkable degree of protection against high voltages: both self-produced and external electric shocks that heavily affected control goldfish failed to evoke involuntary muscle contraction or to affect sensorimotor processing. Even a commercial electrofishing device, set to efficiently immobilise and narcotise fish, failed to have any effect on the electric catfish. Our findings rule out several protective mechanisms and demonstrate a highly efficient and versatile shielding whose nature is presently unclear.

Design Aspects of a High-Speed High-Voltage PMSM for Aerospace Application

2017 ◽  
Vol 10 (3) ◽  
pp. 122
Author(s):  
Flur Ismagilov ◽  
Nikita Uzhegov ◽  
Vyacheslav Vavilov ◽  
Denis Gusakov
Keyword(s):  
High Voltage ◽  
High Speed ◽  
Aerospace Application

A High-Voltage High-Speed AC Switch Based on Controlled Vacuum Surge Arresters

2018 ◽  
Vol 4 (4) ◽  
pp. 4-13
Author(s):  
Vladimir A. SIDOROV ◽  
◽  
Gennady D. DOMASHENKO ◽  
Marat R. AKHMETGAREYEV ◽  
Yurii V. SHCHERBAKOV ◽  
...  
Keyword(s):  
High Voltage ◽  
High Speed ◽  
Surge Arresters

scholarly journals The Optimization of Alternating Current Electrospun PA 6 Solutions Using a Visual Analysis System

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2098
Author(s):  
Tomas Kalous ◽  
Pavel Holec ◽  
Jakub Erben ◽  
Martin Bilek ◽  
Ondrej Batka ◽  
...  
Keyword(s):  
High Voltage ◽  
High Speed ◽  
Visual Analysis ◽  
Polyamide 6 ◽  
Alternating Current ◽  
Sine Wave ◽  
Electrospinning Process ◽  
Camera System ◽  
Polymeric Solutions ◽  
Analysis System

The electrospinning process that produces fine nanofibrous materials have a major disadvantage in the area of productivity. However, alternating current (AC) electrospinning might help to solve the problem via the modification of high voltage signal. The aforementioned productivity aspect can be observed via a camera system that focuses on the jet creation area and that measures the average lifespan. The paper describes the optimization of polyamide 6 (PA 6) solutions and demonstrates the change in the behavior of the process following the addition of a minor dose of oxoacid. This addition served to convert the previously unspinnable (using AC) solution to a high-quality electrospinning solution. The visual analysis of the AC electrospinning of polymeric solutions using a high-speed camera and a programmable power source was chosen as the method for the evaluation of the quality of the process. The solutions were exposed to high voltage applying two types of AC signal, i.e., the sine wave and the step change. All the recordings presented in the paper contained two sets of data: firstly, camera recordings that showed the visual expression of electrospinning and, secondly, signal recordings that provided information on the data position in the signal function.

scholarly journals Inhibition of Primary Photosynthesis in Desiccating Antarctic Lichens Differing in Their Photobionts, Thallus Morphology, and Spectral Properties

2021 ◽  
Vol 9 (4) ◽  
pp. 818
Author(s):  
Miloš Barták ◽  
Josef Hájek ◽  
Alla Orekhova ◽  
Johana Villagra ◽  
Catalina Marín ◽  
...  
Keyword(s):  
Spectral Reflectance ◽  
Quantum Yields ◽  
Specific Response ◽  
Variable Fluorescence ◽  
Protective Mechanisms ◽  
Quenching Analysis ◽  
Relative Water ◽  
Species Specific ◽  
Kinetics Of ◽  
Reflectance Data

Five macrolichens of different thallus morphology from Antarctica (King George Island) were used for this ecophysiological study. The effect of thallus desiccation on primary photosynthetic processes was examined. We investigated the lichens’ responses to the relative water content (RWC) in their thalli during the transition from a wet (RWC of 100%) to a dry state (RWC of 0%). The slow Kautsky kinetics of chlorophyll fluorescence (ChlF) that was recorded during controlled dehydration (RWC decreased from 100 to 0%) and supplemented with a quenching analysis revealed a polyphasic species-specific response of variable fluorescence. The changes in ChlF at a steady state (Fs), potential and effective quantum yields of photosystem II (FV/FM, ΦPSII), and nonphotochemical quenching (NPQ) reflected a desiccation-induced inhibition of the photosynthetic processes. The dehydration-dependent fall in FV/FM and ΦPSII was species-specific, starting at an RWC range of 22–32%. The critical RWC for ΦPSII was below 5%. The changes indicated the involvement of protective mechanisms in the chloroplastic apparatus of lichen photobionts at RWCs of below 20%. In both the wet and dry states, the spectral reflectance curves (SRC) (wavelength 400–800 nm) and indices (NDVI, PRI) of the studied lichen species were measured. Black Himantormia lugubris showed no difference in the SRCs between wet and dry state. Other lichens showed a higher reflectance in the dry state compared to the wet state. The lichen morphology and anatomy data, together with the ChlF and spectral reflectance data, are discussed in relation to its potential for ecophysiological studies in Antarctic lichens.

STEPPING PATTERNS IN ANTS - INFLUENCE OF BODY MORPHOLOGY

1994 ◽  
Vol 192 (1) ◽  
pp. 107-118 ◽  
Author(s):  
C Zollikofer
Keyword(s):  
High Speed ◽  
Functional Relationship ◽  
Coordination Pattern ◽  
Leg Length ◽  
Leg Extension ◽  
Size Dependent ◽  
Tripod Gait ◽  
Locomotory Behaviour ◽  
Species Specific ◽  
Coordination Patterns

The locomotory behaviour of 12 ant species belonging to four different genera (Formicinae: Cataglyphis, Formica, Lasius; Myrmicinae: Myrmica) was studied by filming individuals during walking on smoked-glass plates. Subsequent multivariate analyses of walking kinematics and footfall positions showed marked species-specific as well as size-dependent differences in the locomotory behaviour. The geometric properties of the footfall patterns resulting from the alternating tripod gait scale to leg dimensions in a geometric manner. At high speed, footprint distances between succeeding tripods exceed maximum leg extension, indicating that ants are 'trotting' from one tripod to the next one with intermittent aerial phases. In at least one species (Cataglyphis bombycina), there is evidence for quadrupedal locomotion at the highest speed. The functional relationship between stride length (s, the distance between successive footprints of the same foot) and speed (v) was best described by a curvilinear model, s=avb. Exponent b ranges from 0.3 to 0.6 and reveals differences between species. Within species, exponent b is constant, whereas factor a scales to leg length. Females and males show metachronal interleg coordination patterns rather than the alternating tripod coordination pattern seen in workers of the same species.

4H-SIC Dmosfets for High Frequency Power Switching Applications

2003 ◽  
Vol 764 ◽  
Author(s):  
Sei-Hyung Ryu ◽  
Anant K. Agarwal ◽  
James Richmond ◽  
John W. Palmour
Keyword(s):  
High Voltage ◽  
High Speed ◽  
High Performance ◽  
High Frequency Power ◽  
Power Devices ◽  
Power Switching ◽  
High Speed Switching ◽  
Unipolar Devices ◽  
Very High ◽  
Frequency Power

AbstractVery high critical field, reasonable bulk electron mobility, and high thermal conductivity make 4H-Silicon carbide very attractive for high voltage power devices. These advantages make high performance unipolar switching devices with blocking voltages greater than 1 kV possible in 4H-SiC. Several exploratory devices, such as vertical MOSFETs and JFETs, have been reported in SiC. However, most of the previous works were focused on high voltage aspects of the devices, and the high speed switching aspects of the SiC unipolar devices were largely neglected. In this paper, we report on the static and dynamic characteristics of our 4H-SiC DMOSFETs. A simple model of the on-state characteristics of 4H-SiC DMOSFETs is also presented.

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