scholarly journals Collective intercellular communication through ultra-fast hydrodynamic trigger waves

2018 ◽  
Author(s):  
Arnold J. T. M. Mathijssen ◽  
Joshua Culver ◽  
M. Saad Bhamla ◽  
Manu Prakash
Keyword(s):  
Reynolds Numbers ◽  
Life Forms ◽  
Large Prey ◽  
Sensors And Actuators ◽  
Mechanosensitive Ion Channel ◽  
Spirostomum Ambiguum ◽  
A Chain ◽  
Large Predators ◽  
External Stimuli ◽  
Suction Flow

The biophysical relationships between sensors and actuators [1–5] have been fundamental to the development of complex life forms; Abundant flows are generated and persist in aquatic environments by swimming organisms [6–13], while responding promptly to external stimuli is key to survival [14–19]. Here, akin to a chain reaction [20–22], we present the discovery of hydrodynamic trigger waves in cellular communities of the protistSpirostomum ambiguum, propagating hundreds of times faster than the swimming speed. Coiling its cytoskeleton,Spirostomumcan contract its long body by 50% within milliseconds [23], with accelerations reaching 14g-forces. Surprisingly, a single cellular contraction (transmitter) is shown to generate long-ranged vortex flows at intermediate Reynolds numbers, which can trigger neighbouring cells, in turn. To measure the sensitivity to hydrodynamic signals (receiver), we further present a high-throughput suction-flow device to probe mechanosensitive ion channel gating [24] by back-calculating the microscopic forces on the cell membrane. These ultra-fast hydrodynamic trigger waves are analysed and modelled quantitatively in a universal framework of antenna and percolation theory [25, 26]. A phase transition is revealed, requiring a critical colony density to sustain collective communication. Our results suggest that this signalling could help organise cohabiting communities over large distances, influencing long-term behaviour through gene expression, comparable to quorum sensing [16]. More immediately, as contractions release toxins [27], synchronised discharges could also facilitate the repulsion of large predators, or conversely immobilise large prey. We postulate that beyond protists numerous other freshwater and marine organisms could coordinate with variations of hydrodynamic trigger waves.

Transition detection for laminar flow aircraft using microphones beneath the surface of laser drilled suction panels

2000 ◽  
Vol 214 (3) ◽  
pp. 143-155
Author(s):  
R V Barrett
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Laminar Flow ◽  
Reynolds Numbers ◽  
Suction Surface ◽  
Microphone Signal ◽  
High Background ◽  
Low Reynolds Numbers ◽  
High Background Noise ◽  
Suction Flow

The possibility of detecting transition through the very small laser drilled perforations in panels representing the suction surface of a hybrid laminar flow aircraft is examined. The method uses miniature microphones to detect changes to the noise received from the boundary layer. Tests using a flat plate rig in a low-turbulence wind tunnel at Reynolds numbers up to 3.8 million per metre, demonstrate that the boundary layer state can be defined in this manner, most simply through measurement of the root mean square (r.m.s.) of the microphone signal. It is shown that the r.m.s. reaches a peak in the transition zone and that when the boundary layer is fully turbulent the value is still significantly higher than it was before transition. Porosity in the range 0.8-6.4 percent was examined, with nominal hole diameters of 0.06 and 0.10 mm in 0.9 mm thick laser drilled suction surface specimens. Suction flow through the surface was found not adversely to affect the operation of the system. The experiment was limited to low Reynolds numbers because the high background noise in the wind tunnel made detection of the boundary layer element of the signal increasingly difficult to define as speed increased. It is considered that test in flight will be needed to prove fully the validity of the method. A preliminary design of an installation for this purpose is suggested that allows the suction flow to be maintained over the measuring region.

Research of the suction flow control on wings at low Reynolds numbers

2017 ◽  
Vol 232 (8) ◽  
pp. 1515-1528 ◽  
Author(s):  
Dongli Ma ◽  
Guanxiong Li ◽  
Muqing Yang ◽  
Shaoqi Wang
Keyword(s):  
Flow Control ◽  
Aerodynamic Force ◽  
Separation Bubble ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Flow State ◽  
Laminar Separation ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
Suction Flow

Laminar separation and transition have significant effects on aerodynamic characteristics of the wing under the condition of low Reynolds numbers. Using the flow control methods to delay and eliminate laminar separation has great significance. This study uses the method combined with water tunnel test and numerical calculation to research the effects of suction flow control on the flow state and aerodynamic force of the wing at low Reynolds numbers. The effects of suction flow rate and suction location on laminar separation, transition and aerodynamic performance of the wing are further researched. The results of the research show that, the suction can control laminar separation and transition effectively, when the suction holes are in the interior of the separation bubble, and close to the separation point, the suction has the best control effect. When the Reynolds number is Re = 3.0 × 105, the suction flow control can make the lift-to-drag ratio of the wing increase by 8.62%, and the aerodynamic characteristics of the wing are improved effectively.

Study of Mechanism for Wear Adjustment with Electro Wedge Brake

2014 ◽  
Vol 625 ◽  
pp. 712-716 ◽  
Author(s):  
Dong Hwan Shin ◽  
Tae Sang Park ◽  
Sung Ho Jin ◽  
Jeon Il Moon ◽  
Seung Han Yang
Keyword(s):  
Cost Effective ◽  
Hydraulic Cylinder ◽  
The Other ◽  
Brake System ◽  
Sensors And Actuators ◽  
Uniform Distance ◽  
Adjustment Mechanism ◽  
Hydraulic Brake ◽  
A Chain ◽  
Gap Sensors

Electro wedge brake (EWB) have been suggested and improved for enhancing the braking efficiency and reducing the weight and power of actuating motor than electro mechanical brake (EMB). This is due to self-reinforcement features of the wedge mechanism. On the other hand, the conventional hydraulic brake system has the passive wear adjustment without any sensors and actuators. This is because of the sealing rubber which is disposed between the hydraulic cylinder and piston, and supply the piston’s same restoring strokes regardless of pad’s wear amounts. This feature leads to the uniform distance between the disc and the pad. In comparison, electronic brake systems such as EMB and EWB don’t have the hydraulic piston and cylinder with the sealing rubber. Therefore the electronic brake systems cannot use the function of this passive wear adjustment. However, if the electronic brake system has gap sensors for detecting distances between the pad and the disc, and actuators for keeping the uniform distances between the pad and the disc, then the brake system can have the function of wear adjustments. One of our research goals is the embodiment of cost-effective and feasible wear adjustment mechanism which is proper to EWB. In this paper, as a chain of EWB’s development, we describe the proposed mechanism for wear adjustment with EWB. Further we describe the feasibility of this mechanism with the simulation study.

Sensitivity amplification in biochemical systems

1982 ◽  
Vol 15 (3) ◽  
pp. 555-591 ◽  
Author(s):  
A. Goldbeter ◽  
D. E. Koshland
Keyword(s):  
Blood Clotting ◽  
Biological Systems ◽  
Hormonal Control ◽  
Efficient Control ◽  
Biochemical Systems ◽  
Environmental Variations ◽  
A Chain ◽  
External Stimuli ◽  
Regulatory Properties ◽  
Similar Organization

The sensitivity of biological systems to changes in environmental stimuli is connected with their regulatory properties. In order to achieve efficient control, these systems must respond to minute environmental variations by amplifying external stimuli to yield a significant response. To that end, biochemical systems have often evolved to a cascade organization in which the product of the nth reaction in a chain acts as a catalyst in subsequent transformations. The amplification properties of such cascades were first noticed in the process of blood clotting (MacFarlane, 1964, 1969) and visual excitation (Wald, 1965). Later on, a similar organization was noticed in hormonal control of metabolism (Bowness, 1964; Stadtman & Chock, 1977, 1978; Chock, Rhee & Stadtman, 1980).

The allometry of cannibalism in piscivorous fishes

2003 ◽  
Vol 60 (5) ◽  
pp. 594-602 ◽  
Author(s):  
Francis Juanes
Keyword(s):  
Upper Bound ◽  
Prey Size ◽  
Trophic Niche ◽  
Large Prey ◽  
Predator Species ◽  
Size Dependent ◽  
Predator Size ◽  
Large Databases ◽  
Widespread Phenomenon ◽  
Large Predators

Cannibalism is a widespread phenomenon that can have strong population and community effects. In this study, I compare the prey size – predator size relationships of diets with and without cannibalized prey for four piscivorous species and five populations that are commonly cannibalistic and where large databases exist. I then examine the resultant trophic niche breadths (range of relative prey size consumed) to quantify whether inclusion of cannibalized prey in the diet slows down the decline in trophic niche breadth that many large predators exhibit as they grow. When comparing diets including cannibalized prey with those without, consistent differences were found among all predator species. In all cases, the slope of the upper bound of the predator size – prey size scatters was larger for cannibal predators compared with noncannibals, suggesting selectivity for larger cannibal prey, which may be driven by higher rates of size-dependent capture success with familiar prey. The slopes of the upper bounds of the cannibal relative prey size vs. predator size scatter also tended to be larger than the upper-bound slopes for diets without conspecific prey. Finally, for all species, mean trophic breadth of diets including cannibalized prey were larger than those not including cannibal prey, suggesting that relatively large prey sizes may always be available for cannibals.

scholarly journals Advanced Functional Materials for Intelligent Thermoregulation in Personal Protective Equipment

Polymers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3711
Author(s):  
Alireza Saidi ◽  
Chantal Gauvin ◽  
Safa Ladhari ◽  
Phuong Nguyen-Tri
Keyword(s):  
Personal Protective Equipment ◽  
Functional Materials ◽  
Polymeric Materials ◽  
Protective Equipment ◽  
Sensors And Actuators ◽  
Physical Hazards ◽  
Current State ◽  
Smart Textile ◽  
Improved Performance ◽  
External Stimuli

The exposure to extreme temperatures in workplaces involves physical hazards for workers. A poorly acclimated worker may have lower performance and vigilance and therefore may be more exposed to accidents and injuries. Due to the incompatibility of the existing standards implemented in some workplaces and the lack of thermoregulation in many types of protective equipment that are commonly fabricated using various types of polymeric materials, thermal stress remains one of the most frequent physical hazards in many work sectors. However, many of these problems can be overcome with the use of smart textile technologies that enable intelligent thermoregulation in personal protective equipment. Being based on conductive and functional polymeric materials, smart textiles can detect many external stimuli and react to them. Interconnected sensors and actuators that interact and react to existing risks can provide the wearer with increased safety, protection, and comfort. Thus, the skills of smart protective equipment can contribute to the reduction of errors and the number and severity of accidents in the workplace and thus promote improved performance, efficiency, and productivity. This review provides an overview and opinions of authors on the current state of knowledge on these types of technologies by reviewing and discussing the state of the art of commercially available systems and the advances made in previous research works.

scholarly journals Advanced Functional Materials for Intelligent Thermoregulation in Personal Protective Equipment

2021 ◽  
Author(s):  
Alireza Saidi ◽  
Chantal Gauvin ◽  
Safa Ladhari ◽  
Phuong Nguyen -Tri
Keyword(s):  
Personal Protective Equipment ◽  
Functional Materials ◽  
Protective Equipment ◽  
Sensors And Actuators ◽  
Physical Hazards ◽  
Current State ◽  
Smart Textile ◽  
Improved Performance ◽  
External Stimuli ◽  
Made In

The exposure to extreme temperatures in workplaces involves physical hazards for workers. A poorly acclimated worker may have lower performance and vigilance and may therefore be more exposed to accidents and injuries. Due to the incompatibility of the existing standards implemented in some workplaces and the lack of thermoregulation in many protective equipment, thermal stress remains one of the most frequent physical hazards in many work sectors. However, many of these problems can be overcome with the use of smart textile technologies that enable intelligent thermoregulation in personal protective equipment. Smart textiles can detect, react and adapt to many external stimuli. Interconnected sensors and actuators that interact and react to existing risks can provide the wearer with increased safety, protection and comfort. Thus, the skills of smart protective equipment can contribute to the reduction of errors and the number and severity of accidents in the workplace, and thus promote improved performance, efficiency and productivity.This review provides an overview and opinions of authors on the current state of knowledge on these types of technologies by reviewing and discussing the state of the art of commercially available systems and the advances made in previous research works.

scholarly journals Anisotropic nanocomposite films of hydroxypropylcellulose and graphene oxide with multi-responsiveness

RSC Advances ◽  
2019 ◽  
Vol 9 (49) ◽  
pp. 28876-28885
Author(s):  
Zhimin Ying ◽  
Xiao Ying Lin ◽  
Cong Du ◽  
Si Yu Zheng ◽  
Zi Liang Wu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
Nanocomposite Films ◽  
Sensors And Actuators ◽  
Anisotropic Mechanical Properties ◽  
Potential Applications ◽  
External Stimuli ◽  
Blade Coating

Nanocomposite films fabricated by blade-coating possess anisotropic mechanical properties and multi-responsiveness to external stimuli, affording potential applications as sensors and actuators.

scholarly journals Suction feeding performance and prey escape response interact to determine feeding success in larval fish

2019 ◽  
Author(s):  
Noam Sommerfeld ◽  
Roi Holzman
Keyword(s):  
Early Development ◽  
Escape Response ◽  
High Speed ◽  
Sparus Aurata ◽  
Larval Fish ◽  
Reynolds Numbers ◽  
Larval Performance ◽  
Larval Feeding ◽  
Large Prey ◽  
Feeding Success

AbstractThe survival of larval marine fishes during early development is strongly dependent on their ability to capture prey. Most larval fish capture prey by expanding their mouth cavity, generating a “suction flow” that draws the prey into their mouth. Larval fish dwell in a hydrodynamic regime of low Reynolds numbers, which has been shown to impede their ability to capture non-evasive prey. However, the marine environment is characterized by an abundance of evasive prey such as Copepods. These organisms can sense the hydrodynamic disturbance created by approaching predators and perform high-acceleration escape maneuvers. Using a 3D high-speed video system, we characterized the interaction between 8-33 day post hatchingSparus auratalarvae and prey from a natural zooplankton assemblage that contained evasive prey, and assessed the factors that determine the outcome of these interactions. Larvae showed strong selectivity for large prey that was moving prior to the initialization of the strike. As previously shown in studies with non-evasive prey, larval feeding success increased with increasing Reynolds numbers. However, larval feeding success was also strongly dependent on the prey’s escape response. Feeding success was lower for larger, more evasive prey, indicating that larvae might be challenged in capturing their preferred prey. The kinematics of successful strikes resulted in shorter response time but higher hydrodynamic signature available for the prey. Thus, despite being “noisier”, successful strikes on evasive prey depended on preceding the prey’s escape response. Our results show that larval performance, rather than larval preferences, determines their diet during early development.

Influence of Cell Wall Composition on the Fossilisation of Bacteria and the Implications for the Search for Early Life Forms

1997 ◽  
Vol 161 ◽  
pp. 491-504 ◽  
Author(s):  
Frances Westall
Keyword(s):  
Cell Wall ◽  
Life Forms ◽  
Cation Binding ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Transmission Electron ◽  
Hydrothermal Sediments ◽  
Identification Of Bacteria ◽  
The Difference

AbstractThe oldest cell-like structures on Earth are preserved in silicified lagoonal, shallow sea or hydrothermal sediments, such as some Archean formations in Western Australia and South Africa. Previous studies concentrated on the search for organic fossils in Archean rocks. Observations of silicified bacteria (as silica minerals) are scarce for both the Precambrian and the Phanerozoic, but reports of mineral bacteria finds, in general, are increasing. The problems associated with the identification of authentic fossil bacteria and, if possible, closer identification of bacteria type can, in part, be overcome by experimental fossilisation studies. These have shown that not all bacteria fossilise in the same way and, indeed, some seem to be very resistent to fossilisation. This paper deals with a transmission electron microscope investigation of the silicification of four species of bacteria commonly found in the environment. The Gram positiveBacillus laterosporusand its spore produced a robust, durable crust upon silicification, whereas the Gram negativePseudomonas fluorescens, Ps. vesicularis, andPs. acidovoranspresented delicately preserved walls. The greater amount of peptidoglycan, containing abundant metal cation binding sites, in the cell wall of the Gram positive bacterium, probably accounts for the difference in the mode of fossilisation. The Gram positive bacteria are, therefore, probably most likely to be preserved in the terrestrial and extraterrestrial rock record.

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