Dynamic processes visualization

Transportable high-current KEC-25M betatron on 25 MeV energy with power dose of radiation on 1 m away from the target of 30 Gr/min is the source of penetrating radiation intended for flaw detection in field conditions and radiation visualization of dynamic processes [2]. 

G.V.Akulov, V.I.Bogdashkin, V.A.Moskalev, V.L.Nikolaev, A.V.Tzimbalist, V.V.Shashov, V.G.Shestakov - Mobile betatron installation on energy of 25 MeV for radiative visualization of dynamic processes and flaw detection in field conditions. Atomic science and technique problems. Electrophysical equipment. -1987,v.23,p. 19-21. 

The accuracy achieved through ab initio quantum mechanics and the capabilities of simulations to analyze structural elements and dynamical processes in every detail and separately from each other have not only made the simulations a valuable and sometimes indispensable basis for the interpretation of experimental studies of systems in solution, but also opened the access to hitherto unavailable data for solution processes, in particular those occurring on the picosecond and subpicosecond timescale. The possibility to visualize such ultrafast reaction dynamics appears another great advantage of simulations, as such visualizations let us keep in mind that chemistry is mostly determined by systems in continuous motion rather than by the static pictures we are used to from figures and textbooks. It can be stated, therefore, that modern simulation techniques have made computational chemistry not only a universal instrument of investigation, but in some aspects also a frontrunner in research. At least for solution chemistry this seems to be recognizable from the few examples presented here, as many of the data would not have been accessible with contemporary experimental methods. 

In a third paper by the Bernard and Holm group, visual studies (in a sand-packed capillary tube, 0.25 mm in diameter) and gas tracer measurements were also used to elucidate flow mechanisms ( ). Bubbles were observed to break into smaller bubbles at the exits of constrictions between sand grains (see Capillary Snap-Off, below), and bubbles tended to coalesce in pore spaces as they entered constrictions (see Coalescence, below). It was concluded that liquid moved through the film network between bubbles, that gas moved by a dynamic process of the breakage and formation of films (lamellae) between bubbles, that there were no continuous gas path, and that flow rates were a function of the number and strength of the aqueous films between the bubbles. As in the previous studies (it is important to note), flow measurements were made at low pressures with a steady-state method. Thus, the dispersions studied were true foams (dispersions of a gaseous phase in a liquid phase), and the experimental technique avoided long-lived transient effects, which are produced by nonsteady-state flow and are extremely difficult to interpret. 

Advances in light microscopy have allowed the magnification of objects up to 1,000 times their original size and improved the resolution of the human eye from 0.1 mm to 0.2 Xm (see Table 1 for a comparison of the different visualization techniques). With the aid of histochemical, fluorescence, and autoradiographic methods, in particular, the use of light microscopy in the biological sciences has revealed the substructure of tissues and dynamic processes within cells. 

Thu molecular mechanism of action of vitamin A in the visual process has been under investigation for many years. Wald in 1(168 and Morton in 1972" characterized this mechanism of action. The chemistry of vision was reviewed comprehensively in Accotmi.t of Clwmical Research (1975) by numerous investigators. These reviews include theoretical studies of the visual chromophorc. characleri/alion of ihfldopsin in synthetic systems, dynamic processes in vertebrate rod visual pigments and their membranes, and the dynamics of the visual protein opsin. ""... 

The thermal properties of polymers are important for many applications. Therefore, direct probing of polymers on the micro- and nanoscale may provide important insight for the practitioner. One can differentiate several thermal options for AFM visualization of dynamic processes and quantification of thermal properties and transitions. While heatable probes that offer nanoscale resolution have only recently become available,2 temperature control stages are available in many commercial devices. However, simple devices can also be built according to the requirements. In the most common set-ups, the sample is heated from below by some heating device. 

The Use of Expectation Values of Resonance Operators to Visualize Dynamic Processes. 697... 

The structural characterization of electrode surfaces on the mesoscopic scale is a prerequisite for the elucidation of mesoscopic effects on electrochemical reactivity. The most straightforward approach to access the mesoscopic scale is the application of scanning probes under in-situ electrochemical conditions. Three different applications of STM have been discussed, namely the structural characterization of model electrodes, the visualization of dynamic processes on the nanometer-scale, and the defined modification of electrode surfaces. 

Note that phase transitions are significantly controlled by delicate potential management, and observation of dynamic processes for 2D molecular aggregation would allow us to visually understand the thermodynamic balance based on intermolecular interactions and perpendicular interactions between adsorbates and substrates. 

It should also be noted that the method of surface attachment may also have an influence the properties of the biomolecule of interest. For example, while covalent attachment may facilitate the structural investigation of isolated biomolecular species, such a strong attachment may be disadvantageous if the user wishes to subsequently visualize any dynamic processes of this molecule, as they may be hindered/prevented. For the observation of such dynamic processes the use of immobilization methods such as weak electrostatic interaction is therefore more usual, and in this type of experiment thorough investigation and optimization of the immobilization process is absolutely essential. 

The investigation of fast processes, such as electron motions in atoms or molecules, radiative or collision-induced decays of excited levels, isomerization of excited molecules, or the relaxation of an optically pumped system toward thermal equilibrium, opens the way to study in detail the dynamic properties of excited atoms and molecules. A thorough knowledge of dynamical processes is of fundamental importance for many branches of physics, chemistry, or biology. Examples are predissociation rates of excited molecules, femtosecond chemistry, or the understanding of the visual process and its different steps from the photoexcitation ofrhodopsin molecules in the retina cells to the arrival of electrical nerve pulses in the brain. 

The second volume of Laser Spectroscopy covers the different experimental techniques, necessary for the sensitive detection of small concentrations of atoms or molecules, for Doppler-free spectroscopy, laser-Raman-spectroscopy, doubleresonance techniques, multi-photon spectroscopy, coherent spectroscopy and time-resolved spectroscopy. In these fields the progress of the development of new techniques and improved experimental equipment is remarkable. Many new ideas have enabled spectroscopists to tackle problems which could not be solved before. Examples are the direct measurements of absolute frequencies and phases of optical waves with frequency combs, or time resolution within the attosecond range based on higher harmonics of visible femtosecond lasers. The development of femtosecond non-collinear optical parametric amplifiers (NOPA) has considerably improved time-resolved measurements of fast dynamical processes in excited molecules and has been essential for detailed investigations of important processes, such as the visual process in the retina of the eye or the photosynthesis in chlorophyl molecules. 

Thus, the qualitative (visual) analysis gives ground to make preliminary conclusions concerning the most probable pathways of reagent conversion to reaction products. However, the specificity of isotope response is dependent on the reaction mechanism and may be distorted by the action of gas dynamic processes in the reactor as well as by the nonideality of the input signal. 

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