scholarly journals Movement of the Flagella of Polytoma Uvella

1963 ◽  
Vol 40 (1) ◽  
pp. 149-156
Author(s):  
C. J. BROKAW
Keyword(s):  
Beat Frequency ◽  
Methyl Cellulose ◽  
Dark Field ◽  
Maximum Efficiency ◽  
Sinusoidal Wave ◽  
Low Frequencies ◽  
Atp Concentration ◽  
Wave Patterns ◽  
Internal Viscosity ◽  
Photographic Records

1. Dark-field photographic records of the wave patterns of moving flagella have been made using multiple-flash exposures at flash rates of up to 50 per sec. Patterns obtained from ATP-reactivated isolated flagella show reduced amplitude of bending, but are otherwise similar to those obtained from flagella under normal conditions. The co-ordination required to produce propagated waves of active bending appears to be preserved after isolation and reactivation. 2. Addition of methyl cellulose to the medium to increase the viscosity reduces the frequency of beat much more than the amplitude. This behaviour can be partially explained by an analysis of the equations for sinusoidal wave movement of flagella which shows that maximum efficiency of forward swimming will be obtained if the amplitude of beat is maintained greater than ½π times the wavelength, and variations in available power or viscosity are compensated by changes in beat frequency. 3. Wave patterns at low frequencies in low ATP concentrations are unlike those obtained when the frequency is reduced by increased viscosity. The effect of ATP concentration on beat frequency is not explained by an effect on the power available for beating or by an effect on the ‘internal viscosity‘ of the flagella.

scholarly journals Effects of viscosity and ATP concentration on the movement of reactivated sea-urchin sperm flagella

1975 ◽  
Vol 62 (3) ◽  
pp. 701-719 ◽  
Author(s):  
C. J. Brokaw
Keyword(s):  
Sea Urchin ◽  
Beat Frequency ◽  
Methyl Cellulose ◽  
Intrinsic Rate ◽  
Quantitative Agreement ◽  
Experimental Results ◽  
The Other ◽  
Bend Angle ◽  
Atp Concentration ◽  
Flagellar Beat

Spermatozoa from the sea urchin, Lytechinus pictus, can be demembranated with solutions containing Triton X-100 and 5mM-CaCl2 and reactivated in ATP solutions containing low concentrations (10(−9)M) Of free Ca2+ ion to give symmetrical bending wave movements, even at very low ATP concentrations. At ATP concentrations of 0.01-0.02 mM the reactivated spermatozoa have beat frequencies near 1 Hz, nearly normal bend angles, and wave-lengths about 50% longer than normal. 2. The effects of increased viscosity, obtained by addition of methyl cellulose to the reactivation solutions, on bend angle and beat frequency decrease with decreasing ATP concentration, and become almost undetectable at 0.01 mM ATP. On the other hand, the effect of increased viscosity on wavelength shows relatively little change with ATP concentration, although it is noticeably reduced at 0.01 mM ATP. 3. These observations suggest that the beat frequency at low ATP concentrations is determined by an intrinsic rate-limiting process, in contrast to the viscocity-limited behaviour at high beat frequencies. Quantitative agreement with the experimental results is obtained with a model in which ATP concentration and viscosity each determine the rates of one step in a two-step reaction cycle which determines the beat frequency. 4. Two other models which can qualitatively explain the effects of ATP concentration and viscosity on flagellar beat frequency fail to show quantitative agreement with the experimental results. In one of these models, ATP concentration determines the maximum rate of shear between filaments. In the other, ATP concentration determines a time delay which is required to bring the active moment into phase with the elastic moments which would be expected to dominate the bending resistance at low beat frequencies.

scholarly journals A Micro Swing Rotor Engine and the Preliminary Study of Its Thermodynamic Characteristics

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2684
Author(s):  
Chen Xia ◽  
Zhiguang Zhang ◽  
Guoping Huang ◽  
Tong Zhou ◽  
Jianhua Xu
Keyword(s):  
Power Systems ◽  
Thermal State ◽  
Engine Performance ◽  
Thermodynamic Characteristics ◽  
Practical Significance ◽  
Maximum Efficiency ◽  
Design Guideline ◽  
Engine Operation ◽  
Low Frequencies ◽  
Gap Height

The rapid progress in microelectromechanical system technology has facilitated great developments in micro heat engines, however, defects in these engines still need to be overcome. Thus, a novel four-stroke micro swing rotor engine (MSRE) that features the advantages of Wankel engine and the micro swing engine is proposed in this study. Kinematic and thermodynamic analyses of the MSRE were performed, and a preliminary experimental research was conducted. In the MSRE, the driver assembly was used to dominate the movements of the two rotors. By the design guideline adaptable to the engine operation principle, the volume of each chamber will vary in a sine-like waveform, which was validated by kinematic analyses. Then, a prototype in mesoscale was designed and fabricated. In consideration of the leakage effect, the thermodynamic characteristics of this engine were numerically investigated. Results indicate that the engine thermodynamic processes were seriously affected by leakage flow, especially when working at low frequencies. Gap height and operation frequency were the two dominant factors that affected engine performance. Under a certain gap height, the MSRE had to work at a specific frequency range and the corresponding optical values exist for engine efficiency and power. With a 20 μm height, the MSRE reached the maximum efficiency of 23.62% at 55 Hz and the maximum power of 3442 W at 95 Hz. Feasibility of the engine was further verified by an experimental test on the operation characteristics, including the cold state test with pressured air blow and the combustion test for engine operation at thermal state. This research lays a good foundation for future development of MSRE, which is of great practical significance for the progress in micro power systems.

scholarly journals Effects of adenylyl imidodiphosphate, a nonhydrolyzable adenosine triphosphate analog, on reactivated and rigor wave sea urchin sperm.

1978 ◽  
Vol 79 (3) ◽  
pp. 827-832 ◽  
Author(s):  
S M Penningroth ◽  
G B Witman
Keyword(s):  
Adenosine Triphosphate ◽  
Sea Urchin ◽  
Beat Frequency ◽  
Atp Binding ◽  
Flagellar Motility ◽  
Lytechinus Pictus ◽  
Cross Bridge ◽  
Atp Concentration ◽  
Sea Urchin Sperm

A nonhydrolyzable ATP analog, adenylyl imidodiphosphate (AMP-PNP), has been used to study the role of ATP binding in flagellar motility. Sea urchin sperm of Lytechinus pictus were demembranated, reactivated, and locked in "rigor waves" by a modification of the method of Gibbons and Gibbons (11). Rigor wave sperm relaxed within 2 min after addition of 4 micrometer ATP, and reactivated upon addition of 10-12 micrometer ATP. The beat frequency of the reactivated sperm varied with ATP concentration according to Michaelis-Menten kinetics ("Km" = 0.24 mM; "Vmax" = 44 Hz) and was competitively inhibited by AMP-PNP (Ki" approximately to 8.1 mM). Rigor wave sperm were completely relaxed (straightened) within 2 min by AMP-PNP at concentrations of 2-4 mM. The possibilities that relaxation in AMP-PNP was a result of ATP contamination, AMP-PNP hydrolysis, or lowering of the free Mg++ concentration were conclusively ruled out. The results suggest that dynein cross-bridge release is dependent upon ATP binding but not hydrolysis.

Sliding velocity between outer doublet microtubules of sea-urchin sperm axonemes

1980 ◽  
Vol 44 (1) ◽  
pp. 169-186
Author(s):  
Y. Yano ◽  
T. Miki-Noumura
Keyword(s):  
Polyethylene Glycol ◽  
Atpase Activity ◽  
Sea Urchin ◽  
High Efficiency ◽  
Dark Field ◽  
Video Tape ◽  
Sliding Velocity ◽  
Atp Concentration ◽  
Close Relationship ◽  
Hemicentrotus Pulcherrimus

Using a dark-field microscope equipped with a high-efficiency TV camera including a video tape-recorder, we recorded the sliding movement between outer doublet microtubules of the demembranated axonemes of sea-urchin (Pseudocentrotus depressus and Hemicentrotus pulcherrimus) sperm flagella by adding ATP and trypsin at 25 degrees C. The time and length of the sliding doublet microtubules from axonemes were measured directly from the image on the picture monitor from the video tape. The sliding velocity was almost constant in the range from 0 to 2% polyethylene glycol concentration in the reactivation medium and decreased a little at more than 2%. We prepared various lengths of axoneme fragments by homogenizing whole axonemes and found that the shorter fragments showed similar sliding velocity to that of longer ones at less than 200 microM ATP, but slightly decreased speed at more than 500 microM. ATP. The sliding movement sometimes stopped and the percentage of sliding axonemes was lower below 2 micrograms/ml trypsin. Above 3 micrograms/ml, the process appeared to be more like disintegration than sliding movement, which may be due to excess digestion by trypsin. Sliding speed was therefore measured in a reactivation medium containing 2% polyethylene glycol with the addition of ATP and 2 micrograms/ml trypsin. The velocity increased in proportion to the increase in ATP concentration. Vmax was approximately 14 micrograms/s at 2 mM ATP. In order to compare the Km for the sliding velocity with that of the ATPase activity of the axonemes, we measured ATPase activity of axonemes prepared and assayed under conditions in which sliding movement in the axonemes could be induced. Neither the curve of ATPase activity nor the curve of sliding velocity plotted against ATP concentration obeyed Michaelis-Menten kinetics. The close relationship between ATPase activity and sliding velocity suggested that ‘sliding-movement-coupled ATPase activity’ may well be reflected in the axoneme ATPase reported here.

Tuna robotics: A high-frequency experimental platform exploring the performance space of swimming fishes

2019 ◽  
Vol 4 (34) ◽  
pp. eaax4615 ◽  
Author(s):  
J. Zhu ◽  
C. White ◽  
D. K. Wainwright ◽  
V. Di Santo ◽  
G. V. Lauder ◽  
...  
Keyword(s):  
High Frequency ◽  
High Performance ◽  
Swimming Performance ◽  
Beat Frequency ◽  
Cost Of Transport ◽  
Low Frequencies ◽  
Atlantic Mackerel ◽  
Performance Space ◽  
Wide Range ◽  
Tail Beat

Tuna and related scombrid fishes are high-performance swimmers that often operate at high frequencies, especially during behaviors such as escaping from predators or catching prey. This contrasts with most fish-like robotic systems that typically operate at low frequencies (< 2 hertz). To explore the high-frequency fish swimming performance space, we designed and tested a new platform based on yellowfin tuna (Thunnus albacares) and Atlantic mackerel (Scomber scombrus). Body kinematics, speed, and power were measured at increasing tail beat frequencies to quantify swimming performance and to study flow fields generated by the tail. Experimental analyses of freely swimming tuna and mackerel allow comparison with the tuna-like robotic system. The Tunabot (255 millimeters long) can achieve a maximum tail beat frequency of 15 hertz, which corresponds to a swimming speed of 4.0 body lengths per second. Comparison of midline kinematics between scombrid fish and the Tunabot shows good agreement over a wide range of frequencies, with the biggest discrepancy occurring at the caudal fin, primarily due to the rigid propulsor used in the robotic model. As frequency increases, cost of transport (COT) follows a fish-like U-shaped response with a minimum at ~1.6 body lengths per second. The Tunabot has a range of ~9.1 kilometers if it swims at 0.4 meter per second or ~4.2 kilometers at 1.0 meter per second, assuming a 10–watt-hour battery pack. These results highlight the capabilities of high-frequency biological swimming and lay the foundation to explore a fish-like performance space for bio-inspired underwater vehicles.

Sum and Difference Frequencies in Vibration of High Speed Rotating Machinery

1972 ◽  
Vol 94 (1) ◽  
pp. 181-184 ◽  
Author(s):  
F. F. Ehrich
Keyword(s):  
Spectral Analysis ◽  
Gas Turbine ◽  
High Speed ◽  
Beat Frequency ◽  
Difference Frequency ◽  
Wave Form ◽  
Low Frequencies ◽  
Frequency Wave ◽  
Excitation Frequencies ◽  
The Difference

A vibration incident on a gas turbine engine was noted where two major excitation frequencies were involved—an excitation synchronous with rotor rotation, associated with rotor unbalance, and an asynchronous excitation associated with fluid inadvertently trapped in the rotor. Spectral analysis of the vibration wave form revealed not only the two base excitation frequencies, but also a component at the difference frequency. A mechanism for generating such a difference frequency is hypothesized—the truncation of the basic “beat frequency” wave form by virtue of clearance in the rotor bearing system. Fourier analysis of the hypothesized excitation wave form indicates that components at difference frequency are indeed generated, and also at the sum frequency and a spectrum of higher harmonics and side band frequencies. The hypothesized wave form’s spectral analysis bears a remarkable resemblance to the measured spectrum, except that low frequencies appear to have been greatly amplified in the experimental case, and high frequencies attenuated. This latter fact is attributed to the transmission characteristics of the gas turbine stator system, and is probably responsible for the lack of precise correspondence between the measured and hypothesized wave forms.

Utilizing Dark Field Electron Microscopy to Produce Lantern Slides

1974 ◽  
Vol 32 ◽  
pp. 116-117
Author(s):  
J. N. Meador ◽  
C. N. Sun ◽  
H. J. White
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Dark Field ◽  
Limiting Factor ◽  
Clinical Laboratories ◽  
Field Electron ◽  
Time Element ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Dark Field Micrographs

The electron microscope is being utilized more and more in clinical laboratories for pathologic diagnosis. One of the major problems in the utilization of the electron microscope for diagnostic purposes is the time element involved. Recent experimentation with rapid embedding has shown that this long phase of the process can be greatly shortened. In rush cases the making of projection slides can be eliminated by taking dark field electron micrographs which show up as a positive ready for use. The major limiting factor for use of dark field micrographs is resolution. However, for conference purposes electron micrographs are usually taken at 2.500X to 8.000X. At these low magnifications the resolution obtained is quite acceptable.

Protamine-DNA interaction

1978 ◽  
Vol 36 (2) ◽  
pp. 200-201
Author(s):  
D.P. Bazett-Jones ◽  
F.P. Ottensmeyer
Keyword(s):  
Small Volume ◽  
Double Helix ◽  
Dna Interaction ◽  
Dark Field ◽  
Sperm Head ◽  
Nuclear Proteins ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Dna Double Helix ◽  
Positively Charged

Dark field electron microscopy has been used for the study of the structure of individual macromolecules with a resolution to at least the 5Å level. The use of this technique has been extended to the investigation of structure of interacting molecules, particularly the interaction between DNA and fish protamine, a class of basic nuclear proteins of molecular weight 4,000 daltons.Protamine, which is synthesized during spermatogenesis, binds to chromatin, displaces the somatic histones and wraps up the DNA to fit into the small volume of the sperm head. It has been proposed that protamine, existing as an extended polypeptide, winds around the minor groove of the DNA double helix, with protamine's positively-charged arginines lining up with the negatively-charged phosphates of DNA. However, viewing protamine as an extended protein is inconsistent with the results obtained in our laboratory.

Evaluation of the dark field method for large association of spread DNA

1978 ◽  
Vol 36 (2) ◽  
pp. 190-191
Author(s):  
Douglas C. Barker
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Mitochondrial Dna ◽  
Extraction Method ◽  
Field Method ◽  
Dark Field ◽  
Kinetoplast Dna ◽  
Field Electron ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A number of satisfactory methods are available for the electron microscopy of nicleic acids. These methods concentrated on fragments of nuclear, viral and mitochondrial DNA less than 50 megadaltons, on denaturation and heteroduplex mapping (Davies et al 1971) or on the interaction between proteins and DNA (Brack and Delain 1975). Less attention has been paid to the experimental criteria necessary for spreading and visualisation by dark field electron microscopy of large intact issociations of DNA. This communication will report on those criteria in relation to the ultrastructure of the (approx. 1 x 10-14g) DNA component of the kinetoplast from Trypanosomes. An extraction method has been developed to eliminate native endonucleases and nuclear contamination and to isolate the kinetoplast DNA (KDNA) as a compact network of high molecular weight. In collaboration with Dr. Ch. Brack (Basel [nstitute of Immunology), we studied the conditions necessary to prepare this KDNA Tor dark field electron microscopy using the microdrop spreading technique.

Thin Pyrolytic Graphite Films for Electron Microscope Substrates

1971 ◽  
Vol 29 ◽  
pp. 226-227 ◽  
Author(s):  
George H. N. Riddle ◽  
Benjamin M. Siegel
Keyword(s):  
Vacuum Chamber ◽  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Graphite Substrate ◽  
Nickel Substrate ◽  
Routine Procedure ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.

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