Direct mechanical effects, methods

Class 3-Methods Based on Direct Mechanical Effects. These include the use of acoustical probes [57-71], acoustic impedance measurements [72—75], acoustic fluxmeter [76], the measurement of radiation forces [17,21,77—112], the distortion of liquid surface [ 113-115], surface cleaning, dispersive effects, emulsification [ 116-118], erosion [ 19,22,119-125], mass transfer measurements (electrochemical probe) [26,129], absorption methods [93,132], particle velocity measurements [132], and optical methods [133-141],... 

Lasers are the precision tools of photochemistry and they have been used to both pump (initiate) and probe (analyse) chemical processes on time-scales that are short enough to allow the direct observation of intramolecular motion and fragmentation (i.e. on the femtosecond time-scale). Thus, laser-based techniques provide us with one of the most direct and effective methods for investigating the mechanisms and dynamics of fundamental processes, such as photodissociation, photoionization and unimolecu-lar reactions. Avery wide variety of molecular systems have now been studied using laser techniques, and only a few selected examples can be described here. 

Methods based on direct mechanical effects, including measurements using acoustic probes, optical methods and acoustic impedance, radiation forces, liquid surface distortion or particle velocity measurements. 

In this chapter we take a careful look at the phenomenon of electrical conductivity of materials, particularly electrolytic solutions. In the first section, the nature of electrical conductivity and its relation to the electrolyte composition and temperature is developed. The first section and the second (which deals with the direct-current contact methods for measuring conductance) introduce the basic considerations and techniques of conductance measurement. This introduction to conductance measurements is useful to the scientist, not only for electrolytic conductance, but also for understanding the applications of common resistive indicator devices such as thermistors for temperature, photoconductors for light, and strain gauges for mechanical distortion. The third section of this chapter describes the special techniques that are used to minimize the effects of electrode phenomena on the measurement of electrolytic conductance. In that section you will encounter the most recent solutions to the problems of conductometric measurements, the solutions that have sparked the resurgent interest in analytical conductometry. 

To establish the molecular thermodynamic model for uniform systems based on concepts from statistical mechanics, an effective method by combining statistical mechanics and molecular simulation has been recommended (Hu and Liu, 2006). Here, the role of molecular simulation is not limited to be a standard to test the reliability of models. More directly, a few simulation results are used to determine the analytical form and the corresponding coefficients of the models. It retains the rigor of statistical mechanics, while mathematical difficulties are avoided by using simulation results. The method is characterized by two steps (1) based on a statistical-mechanical derivation, an analytical expression is obtained first. The expression may contain unknown functions or coefficients because of mathematical difficulty or sometimes because of the introduced simplifications. (2) The form of the unknown functions or unknown coefficients is then determined by simulation results. For the adsorption of polymers at interfaces, simulation was used to test the validity of the weighting function of the WDA in DFT. For the meso-structure of a diblock copolymer melt confined in curved surfaces, we found from MC simulation that some more complex structures exist. From the information provided by simulation, these complex structures were approximated as a combination of simple structures. Then, the Helmholtz energy of these complex structures can be calculated by summing those of the different simple structures. 

For a long time the main topic of research in the area of sensitivity analysis was to find an accurate and effective method for the calculation of local concentration sensitivities. This question now seems to be settled, and the decoupled direct method (ddm) is generally considered the best numerical method. All the main combustion simulation packages such as CHEMKIN, LSENS, RUNIDL and FACSIMILE calculate sensitivities as well as the simulation results and, therefore, many publications contain sensitivity calculations. However, usually very little information is actually deduced from the sensitivity results. It is surprising that the application of principal component analysis is not widespread, since it is a simple postprocessing method which can be used to extract a lot of information from the sensitivities about the structure of the kinetic mechanism. Also, methods for parameter estimation should always be preceded by the principal component analysis of the concentration sensitivity matrix. 

Fig. 3. Property of gene delivery with BLs and US exposure (a) Schema of transfection mechanism by BLs and US. The mechanical effect based on the disruption of BLs by US exposure, which results in generation of some pores on plasma membrane, is associated with direct delivery of extracellular plasmid DNA into cytosol, (b) Luciferase expression in COS-7 cells transfected by BLs and US. COS-7 cells (1x10 cells/500 pLAube) were mixed wifh pCMV-Luc (5 pg) and BLs (60 pg). The cell mixture was exposed with US (Frequency 2 MHz, Duty 50%, Burst rate 2 Hz, Intensity 2.5 W/ cm. Time 10 s). The cells were washed and cultured for 2 days. Affer fhaf, luciferase acfivify was measured, (c) Effecf of US condition on transfection efficiency with BLs. COS-7 cells were exposed with US (Frequency 2 MHz, Duty 50%, Burst rate 2 Hz, Intensity 2.5 W/cm Time 0,1, 5,10 s) in the presence of pCMV-Luc (0.25 pg) and BLs (60 pg). Luciferase activity was measured as above, (d) Effect of serum on transfection efficiency of BLs. COS-7 cells in the medium containing EBS (0,10, 30, 50% (v/v)) were treated with US (Erequency 2 MHz, Duty 50%, Burst rate 2 Hz, Intensity 2.5 W/cm, Time 10 s), pCMV-Luc (0.25 pg) and BLs (60 pg) or transfected with lipoplex of pCMV-Luc (0.25 pg) and lipofectin (1.25 pg). (e) In vitro gene delivery to various types of cell using BLs and US. The method of gene delivery was same as above. S-180 mouse sarcoma cells, Colon26 mouse colon adenocarcinoma cells, B16BL6 mouse melanoma cells, Jurkat human T cell line, HUVEC human umbilical endothelial cells. Luciferase activity was measured as above. <10 RLU/mg protein, <10 RLU/mg protein Each data represents the mean S.D. n=3). L PEG-liposomes, LF Lipotectin...

The preceding methods are all in some way related to the mechanical effects of ultrasound. It is also possible to make direct measurements of mass transfer... 

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