Milling of Organic Solids in a Jet Mill. Part 2: Checking the Validity of the Predicted Rate of Breakage Function

The particle size distribution of fine chemicals in the solid state, like active pharmaceutical ingredients, is often a critical parameter. To achieve the desired particle size distribution, milling of such materials is usually the method of choice. Since these chemicals are often scarcely available, experimental optimization of milling is not possible. Therefore, a model to predict the milling conditions has been developed. The model estimates the rate of breakage function, and needs mechanical properties like hardness and yield strength as input to calculate the rate of breakage function. This paper attempts to check the validity of the model by a series of experiments. A comparison of the experimental results with the outcomes of the model using five different model compounds has been performed. It appears that the rate of breakage function can be estimated by: The model is able to rank the compounds by degree of fracture as an effect of milling. It was also possible to perform a quantitative prediction of the impact of milling pressure on the milling behavior. Finally, it appeared that the prediction of the large particles in the distribution was significantly better than small ones. Because the oversized material is usually the most critical parameter, the conclusion is that the model has acceptable practical applicability.     

An internal surface reversed phase column for the effective removal of humic acid interferences in the trace analysis of mecoprop in soils with coupled-column RPLC-UV

In the development of a screening method for the determination of residues of mecoprop in soils involving coupled-column RPLC-UV (228 nm) the cleanup performance of a 5 μm GFF-II internal surface reversed phase (ISRP, Pinkerton) analytical column (50 × 4.6 mm I.D.) as a first column was investigated. In comparison to an analytical C18 column the ISRP column substantially improved the separation between acidic analyte and co-extracted humic substances. Under the selected coupled-column conditions soil extracts obtained after hydrolysis with an aqueous alkaline solution, acidifying and centrifugation could be analyzed directly allowing the determination of mecoprop in soils to a level of about 0.02 mg/kg. A rapid concentration step on a 100 mg C18 solid phase extraction (SPE) cartridge was adopted into the procedure providing a limit of detection (S/N = 3) of 0.01 mg/kg of mecoprop in soil. The method was validated by analyzing freshly spiked soil samples and samples with aged residues. In case of freshly spiked samples the overall recovery was 87% (n = 18, spiked level 0.02–8.0 mg/kg) with a repeatability of 6.8% and a reproducibility of 8.3%. No significant decrease of the recovery was observed for samples with aged residues (n = 15, spiked level 0.1 and 8.0 mg/kg) during a storage of 29 days in the refrigerator at about 4?°C; a storage of 67 days provided a mean recovery of 76% (n = 14, spiked level 8.0 mg/kg).     

Polynomiality of primal-dual affine scaling algorithms for nonlinear complementarity problems

This paper provides an analysis of the polynomiality of primal-dual interior point algorithms for nonlinear complementarity problems using a wide neighborhood. A condition for the smoothness of the mapping is used, which is related to Zhu’s scaled Lipschitz condition, but is also applicable to mappings that are not monotone. We show that a family of primal-dual affine scaling algorithms generates an approximate solution (given a precision ε) of the nonlinear complementarity problem in a finite number of iterations whose order is a polynomial ofn, ln(1/ε) and a condition number. If the mapping is linear then the results in this paper coincide with the ones in Jansen et al., SIAM Journal on Optimization 7 (1997) 126–140. Research supported in part by Grant-in-Aids for Encouragement of Young Scientists (06750066) from the Ministry of Education, Science and Culture, Japan. Research supported by Dutch Organization for Scientific Research (NWO), grant 611-304-028     

Retrieving reflection responses by crosscorrelating transmission responses from deterministic transient sources: application to ultrasonic data

By crosscorrelating transmission recordings of acoustic or elastic wave fields at two points, one can retrieve the reflection response between these two points. This technique has previously been applied to measured elastic data using diffuse wave-field recordings. These recordings should be relatively very long. The retrieval can also be achieved by using deterministic transient sources with the advantage of using short recordings, but with the necessity of using many P-wave and S-wave sources. Here, it is shown how reflections were retrieved from the cross correlation of transient ultrasonic transmission data measured on a heterogeneous granite sample.