Factors controlling the tentacle and polyp expansion behaviour of selected temperate Anthozoa

2006 ◽  
Vol 86 (5) ◽  
pp. 977-992 ◽  
Author(s):  
James J. Bell ◽  
Claire Shaw ◽  
John R. Turner
Keyword(s):  
Predator Avoidance ◽  
Current Flow ◽  
Time Of Day ◽  
High Current ◽  
Light Levels ◽  
Turbulent Flow Regime ◽  
Flow Turbulence ◽  
Predator Abundance ◽  
Expansion Behaviour ◽  
Anemonia Viridis

Although the factors influencing patterns of expansion and contraction of polyps and tentacles for tropical anthozoans has been well described there is still little information for temperate species. This study investigated the patterns of tentacle and polyp expansion behaviour of nine species of temperate Anthozoa in response to current flow, turbulence, food availability and time of day (light) at Lough Hyne Marine Nature Reserve (Ireland). In the absence of current flow, Metridium senile, Caryophyllia smithii, Alcyonium hibernicum and Corynactis viridis exhibited nocturnal expansion of polyps or tentacles with contraction occurring in the daytime, while Alcyonium digitatum, Actinia equina and Cerianthus lloydii showed no differences between light and dark periods. The symbiont containing species Anthopleura ballii and Anemonia viridis expanded or raised their tentacles during daylight hours (tentacle contraction is not possible for A. viridis), although in shallow waters (3 m) Anthopleura ballii tentacles were contracted at midday (highest light levels) presumably to prevent damage from ultraviolet radiation. The contraction of tentacles during light periods was considered a predator avoidance response since zooplankton availability did not vary between light and dark periods, while predator abundance (particularly fish) is greater during daylight. Even though M. senile, Alcyonium hibernicum and Corynactis viridis showed little expansion during daylight periods in the absence of current flow, tentacles and polyps were expanded at midday during periods of high current flow. A greater number of expanded polyps and tentacles were also recorded for A. digitatum, Anemonia viridis and Cerianthus lloydii during high flow conditions compared with periods of low/no flow (Caryophyllia smithii not examined). Actinia equina only exhibited tentacle expansion in response to the creation of a turbulent flow regime, which was determined from laboratory observations. Since species demonstrating contraction during daylight in the absence of current flow expanded their tentacles and polyps when subjected to high current flow, the need for feeding appears to be more important than predator avoidance in controlling expansion behaviour.

Electrode conduction processes in air plasmas

1962 ◽  
Vol 13 (3) ◽  
pp. 465-477 ◽  
Author(s):  
D. W. George ◽  
H. K. Messerle
Keyword(s):  
Magnetic Field ◽  
Shock Tube ◽  
Current Flow ◽  
Electronic Conductivity ◽  
The Other ◽  
High Current ◽  
Air Plasma ◽  
Air Plasmas ◽  
Current Densities

Using an electrically driven shock tube with initial pressures of 0.1 to 1.0 mm Hg and shock speeds of about Mach 12 to 15, the resistance of an air plasma between two parallel probes has been measured by two different techniques and the results compared. In one, external voltages of from 0 to 100 V were applied to the probes and in the other, electromagnetically induced voltages of from 0 to 25 V were produced by the plasma's motion in a magnetic field of up to 3500 G. In either case the resistance was found to decrease as the current flow increased and was consistent with the equilibrium electronic conductivity of the air plasma at high current densities.

Local Current Flow in Mixed-Phase Silicon Solar Cells and Correlation to Light-Induced Open-Circuit Voltage Enhancement

2006 ◽  
Vol 910 ◽  
Author(s):  
Baojie Yan ◽  
C.-S. Jiang ◽  
H. R. Moutinho ◽  
M. M. Al-Jassim ◽  
Jeffrey Yang ◽  
...  
Keyword(s):  
Solar Cells ◽  
Current Flow ◽  
Volume Fraction ◽  
Cell Structure ◽  
Open Circuit ◽  
Phase Region ◽  
Mixed Phase ◽  
High Current ◽  
Conductive Atomic Force Microscopy ◽  
Local Current

AbstractWe use conductive atomic force microscopy (C-AFM) to measure the local current flow in the mixed-phase hydrogenated silicon n-i-p solar cell structure without the top ITO contact. The forward biased C-AFM images reveal that for the fully amorphous region the current is very low on the entire surface. However, high current spikes appear in the mixed-phase region, where the current spikes are correlated to the formation of nanocrystallite aggregations with a diameter of ~500 nm. Furthermore, the density of the current spikes increases from the mixed-phase to the substantially nanocrystalline regions. The nanocrystallite aggregation supports our previously proposed parallel-connected two-diode model for Voc drops with crystalline volume fraction and light-induced Voc increase in the mixed-phase solar cells. Adding a 50-nm thick a-Si:H buffer layer between the p and i layers significantly reduces the magnitude of the high current spikes, even the top morphology appears unaffected. This result is also consistent with the previously proposed two-diode model for explaining the carrier transport in the mixed-phase solar cells.

Variation in dive behavior of Cuvier’s beaked whales with seafloor depth, time-of-day, and lunar illumination

2020 ◽  
Vol 644 ◽  
pp. 199-214 ◽  
Author(s):  
J Barlow ◽  
GS Schorr ◽  
EA Falcone ◽  
D Moretti
Keyword(s):  
Surface Waters ◽  
Predator Avoidance ◽  
Time Of Day ◽  
Maximum Depth ◽  
Near Surface ◽  
Beaked Whales ◽  
Energetic Constraints ◽  
The Mean ◽  
Ziphius Cavirostris ◽  
Foraging Time

Depth distributions were analyzed from a study of 19 Cuvier’s beaked whales Ziphius cavirostris that were tagged with satellite transmitting instruments off southern California, USA. Over 113000 depth measurements were made over the equivalent of ~200 sampling days. The mean foraging depth was 1182 m (SD = 305 m), and the mean of the maximum depth of all foraging dives was 1427 m (SD = 298 m). Mean foraging depths increased with seafloor depths up to a maximum of ~1300 m at a seafloor depth of 1900 m, but decreased slightly to a mean of ~1200 m at seafloor depths of 2000-4000 m. Near-bottom habitat appears to be important for foraging; whales spent ~30% of their foraging time within 200 m of the bottom at seafloor depths of 1000-2000 m. However, little foraging time was spent near the bottom at seafloor depths greater than 2000 m. The percentage of time spent at near-surface depths (<50 m) was more than twice as high at night (25%) than during the day (12%). Lunar light also appears to affect diving, with 28% of dark nights and only 17% of brightly moonlit nights spent at these near-surface depths. The apparent avoidance of surface waters during daytime and on brightly moonlit nights is consistent with avoidance of visual predators. A considerably greater fraction of time was spent foraging at night (24.8%) than during the day (15.7%), possibly due to energetic constraints imposed by predator avoidance during the day.

Structural Analysis of Aquaculture Nets: Comparison and Validation of Different Numerical Modelling Approaches

2014 ◽  
Author(s):  
Heidi Moe-Føre ◽  
Per Christian Endresen ◽  
Karl Gunnar Aarsæther ◽  
Jørgen Jensen ◽  
Martin Føre ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Current Flow ◽  
Cross Flow ◽  
Structural Response ◽  
Parameter Study ◽  
High Current ◽  
Hydrodynamic Load ◽  
Physical Model Tests ◽  
Wake Effects ◽  
Drag Term

The performance of three different numerical methods were compared and evaluated against data from physical model tests. A parameter study of a simplified net cage model subjected to a steady flow was performed by all methods, varying the net solidity and the flow velocity. The three numerical methods applied models based on springs, trusses or triangular finite elements. Hydrodynamic load calculations were based on the drag term in Morison’s equation and the cross-flow principle. Different approaches to account for wake effects were applied. In general, the presented numerical methods should be able to calculate loads and deformations within acceptable tolerance limits for low to intermediate current flow velocities and net solidities, while numerical analyses of high solidity nets subjected to high current velocities tend to overpredict the drag loads acting on the structure. To accurately estimate hydrodynamic loads and structural response of net structures with high projected solidity, new knowledge and methods are needed.

Regeneration rates of a sublittoral demosponge

2002 ◽  
Vol 82 (1) ◽  
pp. 169-170 ◽  
Author(s):  
James J. Bell
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Current Flow ◽  
Water Flow Rate ◽  
High Current ◽  
Food Material ◽  
Regeneration Rate ◽  
Cliona Celata ◽  
Potential Food ◽  
Lough Hyne

The effect of water flow rate on the regeneration rate of the temperate sponge Cliona celata was investigated at two sites experiencing fast and slight current flow respectively at Lough Hyne, Co. Cork, Ireland. Faster regeneration rates were found in sponges living in high current areas which may be due to an increased amount of potential food material per unit time and the possibility of entrained water flow.

Modeling of Polysilicon Resistors, P-N Junction Diodes and Mosfet's

1984 ◽  
Vol 33 ◽  
Author(s):  
A. N. Khondker ◽  
S. S. Ahmed ◽  
T. Liou ◽  
D. M. Kim
Keyword(s):  
Carrier Lifetime ◽  
Current Flow ◽  
Dopant Concentration ◽  
High Current ◽  
Ohmic Conduction ◽  
Direction Parallel ◽  
Mos Devices ◽  
Wide Range ◽  
Conduction Channel ◽  
Channel Region

ABSTRACTConductivity in bulk polysilicon is discussed, applicable over a wide range of dopant concentration, temperature, grain size and trap density. The I-V behavior in a lateral poly p-n junction is analytically modeled, incorporating the effects of carrier lifetime operative in crystalline grain and amorphous conducting boundary. In particular, the extremely short carrier lifetime within the grain boundary is shown to provide an ohmic conduction channel in a direction parallel to current flow. This ohmic current can account for the unusually high current levels observed at small applied voltages. Also, the shift of the threshold voltage of MOS devices, as influenced by grain traps near the channel region, is analysed.

Put a Stop to High Current Flow

2012 ◽  
Vol 115 (1123) ◽  
pp. 394-395
Author(s):  
Tomohiko JIMBO
Keyword(s):  
Current Flow ◽  
High Current

scholarly journals Simulating Physiological Potentials of Daylight Variables in Lighting Design

2022 ◽  
Vol 14 (2) ◽  
pp. 881
Author(s):  
Mimi Ravn ◽  
Gabriela Mach ◽  
Ellen Kathrine Hansen ◽  
Georgios Triantafyllidis
Keyword(s):  
Vertical Plane ◽  
Holistic Approach ◽  
Lighting Design ◽  
Time Of Day ◽  
Physiological Effects ◽  
Smart Building ◽  
Light Levels ◽  
Orientation Time ◽  
Specific Factors ◽  
Sky Conditions

A holistic approach to daylight dynamics in our built environment can have beneficial outcomes for both physiological and visual effects on humans. Simulations of how daylight variables affect light levels on the horizontal work plane are compared to their physiological effects, measured as melanopic EDI (Melanopic Equivalent Daylight Illuminance) on a vertical plane. The melanopic EDI levels were calculated in a simulated office space in ALFA software (Adaptive Lighting for Alertness) employing the daylight variables of orientation, time of day, season, sky conditions and spatial orientation. Results were analyzed for how daylight design can contribute to the physiological effects of dynamic light in office buildings. Daylight is shown to be a sufficient light source in the majority of cases to meet the recommended values of EDI and provide the suggested horizontal lx level according to the Danish Standards. A mapping of daylight conditions, focusing on the specific factors presented here, can provide guidelines in the design process and future smart building systems. The complex interrelationship between these parameters is important to acknowledge when working with daylight dynamics as a sustainable element in architecture and lighting design.

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