Bulk segregant analysis

VILLAR, M., LEFEVRE, F., BRADSHAW, H.D., DUCROS, E.T., Molecular genetics of rust resistance in poplars Melampsora larici-populina Kleb Populus sp) by bulked segregant analysis in a 2x2 factorial mating design. Genetics, 1996, 143, 531-536. 

Michelmore, R. W., Paran, I, and Kesseli, R, V. (1991) Identification of markers linked to disease resistance by bulked segregant analysis a rapid method to detect markers in specific genomic regions using segregating populations. Proc Natl. Acad. Sci USA 88,9828-9832. 

An example of an analysis done on polysilicon and single-crystal Czochralski silicon (CZ) is shown in Table 1. As can be seen, polysilicon, which was used to grow the crystal, is dirtier than the CZ silicon. This is expected, since segregation coefficients limit the incorporation of each element into the crystal boule during the crystal growth process. All values shown in the table are from bulk analysis. Table 2 shows NAA data obtained in an experiment where surface analysis was accom-... 

Ion beams provide useful information either as a diagnostic tool or as a precision etching method in adhesion research. The combination ISS/SIMS method used along with other techniques such as SEM provides a powerful tool for elemental analysis of surface composition. These results, as well as earlier work in this laboratory, indicate that the surface composition can be significantly different from the bulk due to contamination, selective chemical etching and segregation. These same techniques also provide an analysis of the mode of failure in adhesive joints. Many failures classified as "adhesive" on the basis of visual inspection are frequently mixed mode failures or failures at a new interface containing elements of both adhesives and adherend. 

D. Wallace and B. Kratochvil, Visman equations in the design of sampling plans for chemical analysis of segregated bulk materials, Anal. Chem., 59 226 (1987). 

In essence, the test battery should include XRPD to characterize crystallinity of excipients, moisture analysis to confirm crystallinity and hydration state of excipients, bulk density to ensure reproducibility in the blending process, and particle size distribution to ensure consistent mixing and compaction of powder blends. Often three-point PSD limits are needed for excipients. Also, morphic forms of excipients should be clearly specified and controlled as changes may impact powder flow and compactibility of blends. XRPD, DSC, SEM, and FTIR spectroscopy techniques may often be applied to characterize and control polymorphic and hydrate composition critical to the function of the excipients. Additionally, moisture sorption studies, Raman mapping, surface area analysis, particle size analysis, and KF analysis may show whether excipients possess the desired polymorphic state and whether significant amounts of amorphous components are present. Together, these studies will ensure lotto-lot consistency in the physical properties that assure flow, compaction, minimal segregation, and compunction ability of excipients used in low-dose formulations. 

In catalysis it is important not only to be able to study the surface region of the catalyst itself, but also any adlayer that may be present. The latter may arise from adsorption or preferential segregation of one component from the bulk to the surface. The spatial distribution of the elements at the surface can be obtained from scanning AES. Experiments, in which the surface is progressively eroded, e.g., by ion-bombardment, with surface analysis by AES, XPS or ISS carried out after various times, may provide concentration-depth profiles of the chemical species. 

A more dramatic failure results in peel strengths of 0-10 g/mm and is characterized as an adhesive failure at the polyimide/metal oxide interface.This was the only failure mode observed in Ti and Zr films. Isotopically tagged water used with SIMS analysis shows that on annealing water reacts with the Ti with oxygen segregating to the metal/polyimide interface and hydrogen penetrating into the bulk of the Ti, in these samples. 

It is also an effect which is very difficult to quantify. The most successful quantitative methods are MEIS and LEED 1(E) especially when the latter technique is coupled with LEIS. However, these techniques rely on single crystal measurements which may have limited relevance to measurements on bimetallic nanoparticles. Nonetheless, the ability to achieve layer by layer compositional analysis under the influence of an adsorbate means that MEIS data helps to explain why segregation is observed even at relatively low temperatures where bulk diffusion is extremely slow. Activation barriers for near-surface to surface diffusion must be significantly lower than bulk diffusion barriers. 

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