The State-Of-The-Art of the Coagulation/ Flocculation Process

This report has been prepared with the idea of briefly summarizing the most important principles underlying the coagulations/flocculation process as it applies to water and wastewater treatment. The production of potable water from a supply which has been contaminated by naturally-occurring or man-made pollutants has been an object of concern throughout history. Several broad aspects have been considered in the report, such as the history, the nature and physical chemistry of colloidal particles, the theories of and the factors affecting coagulation/flocculation, and control of the coagulation/flocculation process. It is advisable for those persons engaged in the dynamic environmental sciences to occasionally review the basic principles having to do with the processes being employed. In this light, this report provides a cursory review of pertinent literature with regard to the history, the stoichiomentry and physical mechanisms involved, the techniques of process control and an assessment of the state-of-the-art of the coagulation/flocculation process. Of course, this discussion could have been written more extensive detail, but the volume of such an enterprise would be excessive. For those desiring further information, and extensive bibliography of references has been appended

Mitotic mechanics and mechanisms of the budding yeast Saccharomyces cerevisiae

Successful cell division requires the equal segregation of the replicated genome. This process is carried out by a cellular machine known as the mitotic spindle, which is largely conserved across eukaryotes. I have used the budding yeast Saccharomyces cerevisiae as a model organism to better understand the mechanics of the mitotic spindle and the mechanisms that coordinate events during mitosis. Prior to segregation, sister chromatids form bi-polar attachments to microtubules nucleated from the two spindle pole bodies. These attachments are mediated by the kinetochores which link centromeric DNA to microtubules. Biorientation of sister chromatids results in their alignment at the spindle equator, a state known as metaphase. During metaphase, spindle length remains stable. This stability has been largely attributed to the activity of microtubule motors in the spindle. I have taken an alternative approach to dissecting the forces within the metaphase spindle by examining the role of chromatin structure of sister chromatids. By lowering chromatin packaging, I have shown that spindle length is directly regulated by the stretching of pericentric chromatin. This result demonstrates that chromatin is an important structural member of the metaphase spindle. Following metaphase, chromosomes segregate and the cell undergoes cell division to produce two daughter cells. I found that during anaphase, a fraction of inner kinetochore proteins re-localizes to the spindle midzone. This re-localization requires the activity of a yet unidentified motor. Mutation of the inner kinetochore protein Ndc10p results in defects in spindle stability and cell division. This mechanism of spatial regulation of kinetochore proteins appears to contribute to the coordination of chromosome segregation, spindle elongation, and cell division

Pericentric Chromatin Is an Elastic Component of the Mitotic Spindle

Prior to chromosome segregation, the mitotic spindle bi-orients and aligns sister chromatids along the metaphase plate. During metaphase, spindle length remains constant, suggesting that spindle forces (inward and outward) are balanced. The contribution of microtubule motors, regulators of microtubule dynamics, and cohesin to spindle stability has been previously studied. In this study, we examine the contribution of chromatin structure on kinetochore positioning and spindle length control. Following nucleosome depletion, by either histone H3 or H4 repression, spindle organization was examined using live cell fluorescence microscopy

Chemical genetics of \u3ci\u3ePlasmodium falciparum\u3c/i\u3e

Malaria caused by Plasmodium falciparum is a disease that is responsible for 880,000 deaths per year worldwide. Vaccine development has proved difficult and resistance has emerged for most antimalarial drugs. To discover new antimalarial chemotypes, we have used a phenotypic forward chemical genetic approach to assay 309,474 chemicals. Here we disclose structures and biological activity of the entire library—many of which showed potent in vitro activity against drug-resistant P. falciparum strains—and detailed profiling of 172 representative candidates. A reverse chemical genetic study identified 19 new inhibitors of 4 validated drug targets and 15 novel binders among 61 malarial proteins. Phylochemogenetic profiling in several organisms revealed similarities between Toxoplasma gondii and mammalian cell lines and dissimilarities between P. falciparum and related protozoans. One exemplar compound displayed efficacy in a murine model. Our findings provide the scientific community with new starting points for malaria drug discovery

Design Features of a Mitotic Spindle: Balancing Tension and Compression at a Single Microtubule Kinetochore Interface in Budding Yeast

Accurate segregation of duplicated chromosomes ensures that daughter cells get one and only one copy of each chromosome. Errors in chromosome segregation result in aneuploidy and have severe consequences on human health. Incorrect chromosome number and chromosomal instability are hallmarks of tumor cells. Hence, segregation errors are thought to be a major cause of tumorigenesis. A study of the physical mechanical basis of chromosome segregation is essential to understand the processes that can lead to errors. Tremendous progress has been made in recent years in identifying the proteins necessary for chromosome movement and segregation, but the mechanism and structure of critical force generating components and the molecular basis of centromere stiffness remain poorly understood

Molecular architecture of the kinetochore-microtubule attachment site is conserved between point and regional centromeres

Point and regional centromeres specify a unique site on each chromosome for kinetochore assembly. The point centromere in budding yeast is a unique 150-bp DNA sequence, which supports a kinetochore with only one microtubule attachment. In contrast, regional centromeres are complex in architecture, can be up to 5 Mb in length, and typically support many kinetochore-microtubule attachments. We used quantitative fluorescence microscopy to count the number of core structural kinetochore protein complexes at the regional centromeres in fission yeast and Candida albicans. We find that the number of CENP-A nucleosomes at these centromeres reflects the number of kinetochore-microtubule attachments instead of their length. The numbers of kinetochore protein complexes per microtubule attachment are nearly identical to the numbers in a budding yeast kinetochore. These findings reveal that kinetochores with multiple microtubule attachments are mainly built by repeating a conserved structural subunit that is equivalent to a single microtubule attachment site