Ultrasound controlled

Echogenic liposomes seem to constitute one of the most sensitive ultrasound-controlled release systems yet described, with ultrasound having been used to trigger release from several different echogenic liposomal drug delivery preparations such as tissue plasminogen activator (tPA) and papaverin (22, 23). 

Huang SL, McPherson DD, Macdonald RC (2008) A method to co-encapsulate gas and drugs in liposomes for ultrasound-controlled drug dehvery. Ultrasound Med Biol 34(8) 1272-1280... 

Ennis MG, MacErlean DP (1981) Biopsy of bowel wall pathology under ultrasound control. Gastrointest Radiol 15 17-20... 

Ultrasound Controllable protein release Specialized equipment for controlling the release... 

Hottot, A., Nakagawa, K., Andrieu, J., 2008. Effect of ultrasound-controlled nucleation on structural and morphological properties of freeze-dried manitol solution. Chem. Eng. Res. Des. 86 193-200. 

Koivukangas, Y., Louhisalmi, J., Alakuijala, H., and Oikarinen, J. (1993). Ultrasound-controlled neuronavigator-guided brain surgery, /. Neurosurg. 79, 36-42. 

Chuah SY (2000) Liver biopsy under ultrasound control implications for training. Gut 46 583-584... 

Gao, Z.-G., Fain, H. D., Rapoport, N. (2005). Controlled and targeted tumor chemotherapy by micellar-encapsulated drug and ultrasound, /. Control. Release, 102,203-222. 

In this paper, the performanees of laser-ultrasound are estimated in order to identify lacks of weld penetration. The laser-ultrasonic technique is applied to cylindrical metallic strucmres (few mm thick) in a single-sided control. The results obtained for different materials (gold-nickel alloy and tantalum) are presented by B-sean views for which the control configuration is discussed with regard to the thermal effects at the laser impact. This testing is performed for different lacks of weld penetration (up to 0.5 mm for a thickness of 2 mm) even in the presence of the weld bead, which corresponds to an actual industrial problem. 

Then, the weld depths penetration are controlled in a pulse-echo configuration because the weld bead (of width 2 mm) disturbs the detection when the pump and the probe beams are shifted of 2.2 mm. The results are presented in figure 8 (identical experimental parameters as in figure 7). The slow propagation velocities for gold-nickel alloy involve that the thermal component does not overlap the ultrasonic components, in particular for the echo due to the interaction with a lack of weld penetration. The acoustic response (V shape) is still well observed both for the slot of height 1.7 mm and for a weld depth penetration of 0.8 mm (lack of weld penetration of 1.7 mm), even with the weld bead. This is hopeful with regard to the difficulties encountered by conventional ultrasound in the case of the weld depths penetration. 

The weld depths penetration for gold-nickel alloy and tantalum cylinders have been well controlled by an entirely contactless ultrasound method. Nevertheless, the development of signal and image processing will allow to increase the resolution of the ultrasonic images. Moreover, in order to be able to size quite well the lacks of weld penetration, the simulation of the interaction beam-defect is presently developed in our laboratory. 

Shoe Delay. Defines the shoe, or wedge, delay, in tenths of microseconds, of the prohe being used. This control is used to adjust the zero point of time interval measurement to correspond to the instant that the ultrasound pulse enters the test piece. 

Eig. 9. A typical sonochemical apparatus with dkect immersion ultrasonic horn. Ultrasound can be easily introduced into a chemical reaction with good control of temperature and ambient atmosphere. The usual pie2oelectric ceramic is PZT, a lead 2kconate titanate ceramic. Similar designs for sealed... 

External Control. The use of external control to govern the release of dmgs from dehvery systems has largely been experimental. A number of mechanisms have been explored, and include external sources such as electrical currents, magnetism, ultrasound, temperature changes, and irradiation. 

The stereoselectivity of conjugate addition and cyclopropanation of the chiral nitrovinyldioxolanes 17 can be effectively controlled <96TL6307>, and good selectivity is observed in the ultrasound-promoted cycloaddition of nitrile oxides to alkenyldioxolanes 18 <95MI877,95JOC7701 >. Asymmetric Simmons-Smith cyclopropanation of 19 proceeds with... 

Figure 6.2 Two-step cutting of CNTs by hydrocarbon-assisted oxidation on silver clusters, followed by I-INO3 treatment mediated by ultrasound. The length of the CNTs is controlled through the Ag loading. (Reprinted with permission from [132], Copyright 2008, The Royal Society of Chemistry.)...

Ultrasound can thus be used to enhance kinetics, flow, and mass and heat transfer. The overall results are that organic synthetic reactions show increased rate (sometimes even from hours to minutes, up to 25 times faster), and/or increased yield (tens of percentages, sometimes even starting from 0% yield in nonsonicated conditions). In multiphase systems, gas-liquid and solid-liquid mass transfer has been observed to increase by 5- and 20-fold, respectively [35]. Membrane fluxes have been enhanced by up to a factor of 8 [56]. Despite these results, use of acoustics, and ultrasound in particular, in chemical industry is mainly limited to the fields of cleaning and decontamination [55]. One of the main barriers to industrial application of sonochemical processes is control and scale-up of ultrasound concepts into operable processes. Therefore, a better understanding is required of the relation between a cavitation coUapse and chemical reactivity, as weU as a better understanding and reproducibility of the influence of various design and operational parameters on the cavitation process. Also, rehable mathematical models and scale-up procedures need to be developed [35, 54, 55]. 

Figure 2 schematically presents a synthetic strategy for the preparation of the structured catalyst with ME-derived palladium nanoparticles. After the particles formation in a reverse ME [23], the hydrocarbon is evaporated and methanol is added to dissolve a surfactant and flocculate nanoparticles, which are subsequently isolated by centrifugation. Flocculated nanoparticles are redispersed in water by ultrasound giving macroscopically homogeneous solution. This can be used for the incipient wetness impregnation of the support. By varying a water-to-surfactant ratio in the initial ME, catalysts with size-controlled monodispersed nanoparticles may be obtained. 

We have been recently studying new pathways leading to polysilanes with low polydispersity and controlled structures. Our research is focused on three areas. The first one is low temperature reductive coupling in the presence of ultrasound. This leads to monomodal polymers with molecular weights in the range from Mn=50,000 to Mn=300,000 and polydispersities as low as Mw/Mn=1.20 (in addition to usually formed cyclic oligomers). 

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