Rotor speed determination

During the actual preparation of the GPC/SEC gel, there are several noteworthy items in the procedure. When combining aqueous and organic phases, always pour the organic phase into the water phase as the reverse procedure produces very large particles. This mixture must be held at 40°C to prevent the initiator from starting the reaction before the right size particles are formed. Rotor speed determines the particle size of the spheres the faster the speed the smaller the particles. Constant torque mixers produce the best results with more narrow particle-size distributions. The initial mixture should be stirred at 300-400 rpm to ensure a particle-size distribution from 2 to 20 yam. 

The rotor speed of the scaled up tower is based on maintaining the same specific power input number as used on the pilot column it can be determined by substituting the specific values into the relationship ... 

The male and female rotors act much like any bladed or gear unit. The number of lobes on the male rotor multiplied by the actual male shaft speed determines the rotor-passing frequency. In most cases, there are more lobes on the female than on the male. To ensure inclusion of all passing frequencies, the rotor-passing frequency of the female shaft also should be calculated. The passing frequency is equal to the number of lobes on the female rotor multiplied by the actual female shaft speed. 

The CALCULATION function provides a variety of routine calculations performed in most ultracentrifugation laboratories. Included are dilution calculations for sucrose, a pelleting time calculation, and a calculation for determining rotor speed reductions for salt gradients. As with the INFORMATION function, the CALCULATION function is a support tool in the effort to efficiently design and carry out a separation. 

The magnitude and location of the test unbalance(s) shall be determined from a calibration of the rotor s sensitivity to unbalance. The calibration shall be performed by obtaining the vibration orbits at each bearing, filtered to rotor speed (IX), during two trial runs as follows ... 

The thickness of the liquid film on the rotor packing helps determine mass transfer rates. Film thickness can be shown to be inversely proportional to rotor speed to the 0.8 power (17). Visual measurements using a video camera attached to the rotor show a water film thickness of 20-80 microns on foam metal packing and 10 microns on wire gauze packing (15). Theoretical models estimate similar film thickness values (13,18,19). Film flow is expected to be laminar. In addition to rotor speed, liquid flow rate and fluid properties affect the film thickness (14). 

The lipoprotein density that should be employed in Eq. (2) is the buoyant density, which is the density at which the sedimentation coefficient is equal to zero. The buoyant density was obtained experimentally by measuring the sedimentation coefficient at several solvent densities and extrapolating to zero. Kahlon et al. (1982) have shown that the buoyant densities, which they call the a densities, vary with the rotor speed of the centrifuge, reflecting the different compressibilities of water and lipid. In order to convert the lipoprotein density, as determined from its composition, to the buoyant density at a rotor speed of 52,640, the data of Kahlon et al. (1982) were used calculate a correction factor of 0.0016 g/ml, which was added to the compositional densities. The values of buoyant densities listed in Table 11 have been calculated by adding 0.0016 g/ml to the density values determined from their compositions. 

Standard mixing conditions were to melt blend the samples at 300 C for five minutes at a rotor speed of 40 RPM. The effect of mixing history on the structure of the LCP/LCP blends has not been investigated in the present work. Such a study has been reported by Mehta and Baird (i ).The samples were, then, given two minutes at 5 RPM followed by programming the rotor speed to 100 RPM in a two minute period. The speed is, then, instantaneously lowered back down to 5 RPM in two minutes. This is followed by two minutes at 5 RPM to determine whether the ramp test has affected the sample i n any way. 

Average molecular weights were determined for the acetylated lignin samples from sedimentation equilibrium at different rotor speeds and positions in the cell... 

Paucidisperse acetylated methylated and underivatized kraft lignin fractions were selected for absolute molecular weight determinations at 8 x lO g/liter concentrations in DMF and aqueous O.lOMNaOH, respectively, using the Beckman Optima XL-A analytical ultracentrifuge. The partial specific volumes of the solute species (0.744 cm Vg), and densities p of solvent or solution were measured with a Paar 60/602 digital density meter. The sedimentation curves were scaimed at two wavelengths (280 and 320 nm) after equilibrium had been reached at more than one suitable rotor speed the effective baseline at 600 nm was subtracted from each set of sedimentation equilibrium data to correct for... 

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