scholarly journals Waveform shape near Mach cone arrival for the pressure perturbation created by a modulated laser beam moving over a water surface at supersonic speed

1982 ◽  
Vol 71 (S1) ◽  
pp. S13-S13
Author(s):  
Allan D. Pierce
Keyword(s):  
Laser Beam ◽  
Water Surface ◽  
Pressure Perturbation ◽  
Supersonic Speed

Centroid drift of laser beam propagation through a water surface with wave turbulence

2020 ◽  
Vol 59 (20) ◽  
pp. 6210 ◽  
Author(s):  
Jun Li ◽  
Jianghua Luo ◽  
Shangbin Li ◽  
Xiuhua Yuan
Keyword(s):  
Laser Beam ◽  
Water Surface ◽  
Beam Propagation ◽  
Wave Turbulence ◽  
Laser Beam Propagation

scholarly journals Effects of the Wavenumber Spectrum of a Sea Surface on Laser Beam Reflection

1979 ◽  
Vol 32 (5) ◽  
pp. 469 ◽  
Author(s):  
DM Phillips
Keyword(s):  
Laser Beam ◽  
Water Surface ◽  
Pulsed Laser ◽  
Sea Surface ◽  
Beam Diameter ◽  
The Mean ◽  
Wavenumber Spectrum ◽  
Beam Reflection ◽  
Depth Sounding ◽  
Pulsed Laser Beam

The angular and temporal distributions of energy in the reflection of a pulsed laser beam from a sea surface depend on the diameter of the beam and on the wavenumber spectrum of the water surface. Theoretical expressions are derived for the influence on the reflection of the mean height and slope of waves in the illuminated area as well as the variation of the height and slope within this area. The results are applied to airborne lasers for wave height profiling, altimetry and water depth sounding. The optimum beam diameter depends on both the application and the wavenumber pectrum of the water surface.

scholarly journals Phenomenon of a single cause of the cluster-dipole nature of the observability of the area of hydrophysical disturbances from a submarine moving object by a laser beam and radar signal

2019 ◽  
pp. 62-71
Author(s):  
Vladimir Ivanovich Polenin
Keyword(s):  
Liquid Crystals ◽  
Laser Beam ◽  
Electromagnetic Radiation ◽  
Water Surface ◽  
Moving Object ◽  
Sea Surface ◽  
Radar Signal ◽  
Similar Nature ◽  
Radar Station ◽  
Underwater Object

Relationships of cause and effect which are the cornerstone of the phenomenon of observability of area of hydrophysical indignations from an underwater moving object, including its exit to a sea surface when lighting the area in the thickness of water by a laser beam and radiation of the sea surface over an object with a radar station signal are described in the article. In the stationary marine environment the laser beam creates a backscattering signal of a fixed level. In the area of hydrodynamic indignations from an underwater moving object the signal of a backscattering of variable brightness to the relevant structure and level of indignations is seen. The similar phenomenon of a backscattering of the electromagnetic radiation of radar station that creates glare effects on the screen of radar station in a zone of an exit of hydrodynamic indignations is observed on a water surface. It is shown that these phenomenons have similar nature caused by the change of dimensional orientation of dipoles of molecules and liquid crystals clusters of water in the field of the hydrodynamic indignations accompanying the moving of an underwater object. Establishing of this characteristic, in case of its confirmation by test data, meets the requirements of qualification of opening.

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

Two-photon excitation microscopy in cellular biophysics

1995 ◽  
Vol 53 ◽  
pp. 62-63
Author(s):  
David W. Piston ◽  
Brian D. Bennett ◽  
Robert G. Summers
Keyword(s):  
Confocal Microscopy ◽  
Laser Beam ◽  
Duty Cycle ◽  
Excited Electronic State ◽  
Input Power ◽  
Two Photon ◽  
Simultaneous Absorption ◽  
Photon Excitation ◽  
Very High ◽  
Two Photon Excitation

Two-photon excitation microscopy (TPEM) provides attractive advantages over confocal microscopy for three-dimensionally resolved fluorescence imaging and photochemistry. Two-photon excitation arises from the simultaneous absorption of two photons in a single quantitized event whose probability is proportional to the square of the instantaneous intensity. For example, two red photons can cause the transition to an excited electronic state normally reached by absorption in the ultraviolet. In practice, two-photon excitation is made possible by the very high local instantaneous intensity provided by a combination of diffraction-limited focusing of a single laser beam in the microscope and the temporal concentration of 100 femtosecond pulses generated by a mode-locked laser. Resultant peak excitation intensities are 106 times greater than the CW intensities used in confocal microscopy, but the pulse duty cycle of 10-5 maintains the average input power on the order of 10 mW, only slightly greater than the power normally used in confocal microscopy.

The atomic-force microscope and its future in biology

1993 ◽  
Vol 51 ◽  
pp. 704-705
Author(s):  
Jean-Paul Revel
Keyword(s):  
Silicon Nitride ◽  
Laser Beam ◽  
Atomic Force Microscope ◽  
Scanning Tunneling Microscope ◽  
Point Of View ◽  
Scanning Tunneling ◽  
Close Relative ◽  
Tunneling Microscope ◽  
Atomic Force ◽  
Sharp Point

The last few years have been marked by a series of remarkable developments in microscopy. Perhaps the most amazing of these is the growth of microscopies which use devices where the place of the lens has been taken by probes, which record information about the sample and display it in a spatial from the point of view of the context. From the point of view of the biologist one of the most promising of these microscopies without lenses is the scanned force microscope, aka atomic force microscope.This instrument was invented by Binnig, Quate and Gerber and is a close relative of the scanning tunneling microscope. Today's AFMs consist of a cantilever which bears a sharp point at its end. Often this is a silicon nitride pyramid, but there are many variations, the object of which is to make the tip sharper. A laser beam is directed at the back of the cantilever and is reflected into a split, or quadrant photodiode.

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