Particle size modulation

In addition to the hardness and shape, particle size is another important property for an abrasive. Three relevant parameters that characterize a CMP slurry are mean particle size, particle-size distribution, and oversized particle count. The particle size modulates the material removal rate, WIWNU, and surface quality for both metal and nonmetal CMP. There are two CMP mechanisms that describe the relationship between particle size and removal rate. For a slurry containing extremely large particles, the indentation mechanism may dominate. More specifically, the material removal rate depends on the indentation volume. In other words, the volume of material removal per particle is directly proportional to the particle size. The net effect is that an increase in particle size leads to an increase in material removal rate. A slurry containing smaller particles will follow the contact-area mechanism... 

For the preparation of nanoparticles based on two aqueous phases at room temperature one phase contains chitosan and poly(ethylene oxide) and the other contains sodium tripolyphosphate. The particle size (200-1000 nm) and zeta potential (between -i- 20 mV and -l- 60 mV) could be modulated by varying the ratio chitosan/PEO-PPO. These nanoparticles have great proteinloading capacity and provide continuous release of the entrapped protein (particularly insulin) for up to one week [100,101]. 

High Performance Liquid Chromatographic (HPLC) Analysis. A Waters HPLC system (two Waters 501 pumps, automated gradient controller, 712 WISP, and 745 Data module) with a Shimadzu RF-535 fluorescence detector or a Waters 484 UV detector, and a 0.5 pm filter and a Rainin 30 x 4.6 mm Spheri-5 RP-18 guard column followed by a Waters 30 x 3.9 cm (10 pm particle size) p-Bondapak C18 column was used. The mobile phase consisted of a 45% aqueous solution (composed of 0.25% triethylamine, 0.9% phosphoric acid, and 0.01% sodium octyl sulfate) and 55% methanol for prazosin analysis or 40% aqueous solution and 60% methanol for naltrexone. The flow rate was 1.0 mL/min. Prazosin was measured by a fluorescence detector at 384 nm after excitation at 340 nm (8) and in vitro release samples of naltrexone were analyzed by UV detection at 254 nm. 

Depth profiling of a solid sample may be performed by varying the interferometer moving-mirror velocity (modulated IR radiation). By increasing the mirror velocity, the sampling depth varies, and surface studies may be performed. Limitations do exist, but the technique has proven to be quite effective for solid samples [21]. In addition, unlike diffuse reflectance sampling techniques, particle size has a minimal effect upon the photoacoustic measurement. 

Both LC modules and columns must withstand higher generated backpressures. Table 3.3 presents an overview of commercially available columns for use with particle sizes below 2.0 /.an. Wu17 cites additional manufacturers and the numbers increase continuously. According to Kofmann et al.,18... 

Fogli et al. developed and validated an HPLC method with fluorescence detection for simultaneous routine TDM of anthracyclines and their metabolites.27 They coupled a Waters LC Module I Plus system equipped with a WISP 416 autosampler with a Model 474 scanning fluorescence spectrophotometer. The stationary phase was a Supelcosil LC-CN column (250 x 4.6 mm, 5 /um particle size) with a /iBondapak-CN guard column. The mobile phase consisted of 50mM monobasic sodium phosphate buffer and acetonitrile (65 35 v/v), adjusted to pH 4.0 with phosphoric acid. The flow rate was 1 mL/min. The fluorescence detection was set at excitation wavelengths of 233, 254, and 480 nm and at an emission wavelength of 560 nm. 

Figure 6.3. Schematic of interference fringe region, measurement volume, Doppler burst signals, and effects of particle size on signal modulation.

The catalysts can be obtained by a coprecipitation method consisting of two steps (Figure 6.2). In the first step, a stable suspension of protected metal nanoparticles is obtained according to the method reported by Schulz and co-workers [75-77]. The metal particles are prepared in the presence of a highly water-soluble ionic surfactant which is able, due to its nature, to modulate the particle size and to prevent their aggregation. Modifying parameters such as pH, temperature and surfactant concentration, it is possible to tune the metal particle size [71]. Moreover, the role of the... 

In color picture tubes, the final color is formed by additive mixing of red, green, and blue light. Each of the three phosphors (Table 58) is excited by its own modulated electron beam and emits light of intensity corresponding to the particular degree of excitation. The phosphors for color picture tubes have an average particle size of 8-10 pm. 

Benincasa et al. (2003) also studied the effect of ionic strength and electrolyte composition on hydrodynamic characteristics of HS. The author s reported that components of different HS fractions behave like organic acids, but that the retention level of fractions with larger components may not be accurately modulated by varying mobile phase properties as these species are either totally retained in acidic phases or released before the void peak at pH 4.2. Authors concluded that pronounced differences exist in the physicochemical properties of some HS components even when particle sizes were similar. 

Gore, J. P. and Crowe, C. T. (1989). Effect of Particle Size on Modulating Turbulent Intensity. Int. J. Multiphase Flow, 15, 279. 

Figure 10 Measurement of the lifetime of NO molecules adsorbed on the Pd particles, (a) Stationary desorbed NO pulse in response to a square wave modulated NO beam at a frequency of 12.5 Hz. The continuous curve represents an exponential decay with a time constant t (from Ref. [91]). (b) Arrhenius plot of the life time t for two different Pd particles sizes (from Ref. [89]).

Gan, Q., Wang,T., Cochrane, C., and McCarron, P. (2005), Modulation of surface charge, particle size and morphological properties of chitosan-TPP nanoparticles intended for gene delivery, Colloids Surf. B. Biointerfaces, 44(2-3), 65-73. 

Whilst sulfate appears to be fundamental to haze formation, other wine components such as phenolic compounds remain as candidate haze modulators. One possibility is that white wine phenolic compounds affect the particle size of denatured aggregated proteins, possibly through crosslinking. Several researchers (Oh et al. 1980 Siebert et al. 1996b) have suggested a hydrophobic mechanism for the interaction between phenolic compounds and proteins, in which the protein has a fixed number of phenolic binding sites. More of these sites are exposed when the protein is denatured. 

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