Alum flocculation and bioflocculation of activated sludge for vacuum filtration

This study investigated the relationship between sludge loading rate, COD-to-nitrogen ratio of influent waste, and maximum difference in specific resistance as a result of chemical conditioning (DeltaZ). It also related DeltaZ to sludge carbohydrate content, protein content, and surface charge. This research also explored the necessity of chemical conditioning when an activated sludge exhibits excellent bioflocculation characteristics.     

A model for the filterability of activated sludge supported by mixed-liquor biochemical data

A predictive model was developed to estimate the dewatering characteristics of waste-activated sludges. This model utilizes the COD-nitrogen ratio of the wastewater and the organic loading rate of the process to predict sludge filterability in terms of specific resistance. A completely mixed, continuous flow secondary treatment process with solids recycle was used for the cultivation of activated sludges. The sludge wasted from this process was used in Buchner funnel specific resistance determinations. The basic concepts involved in the development of the model were supported by sludge carbohydrate, protein, and surface charge data.     

Linkage of loci affecting a murine liver protein and arylsulfatase B to chromosome 13

As-1 is the putative structural locus for murine arylsulfatase B, and Lth-1 determines the presence or absence of a 35 000 dalton acidic liver protein. As-1 and Lth-1 were found to be closely linked using recombinant inbred (RI) strains. Both loci were found to have been cotransferred with the pearl (pe) coat color mutation (chromosome 13) in the B6.C3H pe/pe congenic strain. The linkage relationships between pe, Lth-1, and As-1 were further defined in a backcross. On the basis of the RI data, the congenic strain result, and the backcross data, the following genetic distances were estimated: pe--As-1, 7.1 +/- 4.0 cM; As-1--Lth-1, 2.5 +/- 1.0 cM; and pe--Lth-1, less than 6.9 cM. As-1 and Lth-1 are the first biochemically defined loci to be added to the chromosome 13 linkage map.     

Nif- Hup- mutants of Rhizobium japonicum.

Two H2 uptake-negative (Hup-) Rhizobium japonicum mutants were obtained that also lacked symbiotic N2 fixation (acetylene reduction) activity. One of the mutants formed green nodules and was deficient in heme. Hydrogen oxidation activity in this mutant could be restored by the addition of heme plus ATP to crude extracts. Bacteroid extracts from the other mutant strain lacked hydrogenase activity and activity for both of the nitrogenase component proteins. Hup+ revertants of the mutant strains regained both H2 uptake ability and nitrogenase activity.     

Membrane potentials associated with Ca-induced K conductance in human red blood cells: Studies with a fluorescent oxonol dye,WW 781

Summary A divalent anionic dye, bis-[3-methyl-1-p-sulfophenyl-5-pyrazolone-(4)]-pentamethine oxonol (WW 781) is a rapidly responding fluorescent indicator of KCl diffusion potentials induced in human red blood cells with valinomycin, gramicidin, and with the Ca ionophore A 23187 in the presence of external Ca. WW 781 has a sensitivity of 0.13% F/mV, a detection limit of 10 mV, a response time of less than 1 sec, and exhibits a decrease in fluorescence intensity upon hyperpolarization without detectable shifts in absorption or emission peaks. This dye does not perturb the normal resting potential, and unlike the slow permeant cyanine dyes, does not inhibit Ca-induced K conductance in human red blood cells. However, WW 781 does stimulate Ca-induced unidirectional Rb efflux. With Ca plus A 23187, the initial rapid change in dye fluorescence is sensitive to [Ca] _o and to [A 23187], is reversible with excess EGTA, and is inhibited by quinine, oligomycin, and by trifluoperazine. A biphasic dependence of hyperpolarization on K _o is evident at pH 6, where the ionic selectivity of activation is K, Rb>Cs>Na and that of conductance is K, Rb>Cs. Conditions were defined which permitted continuous monitoring ofE _m for at least 10 min, and the time dependence of the Ca-induced potentials was characterized. Since the properties of the Ca-induced changes in dye fluorescence correlate well with the known characteristics of Ca-induced K permeability, we conclude that WW 781 is a useful indicator of changes inE _m, provided that sufficient controls are employed to separate direct effects of Ca on dye fluorescence from the effects ofE _m on fluorescence.     

'DNA snapback' peptides

Thermal denaturation studies show that 10-15% of the calf thymus DNA in the heat denatured (Tyr-Gly-Tyr-Gly-Tyr)-DNA complex renatures spontaneously after colling. The double-strandness of this DNA was verified by its resistance to single-strand Neurospora endonuclease and by its elution profile on hydroxypatite columns. The renatured DNA isolated by the latter technique was found to contain 56% GC compared to the 41% GC content of the whole thymus DNA. Alternating tryptophanyl-glycyl and histidyl-glycyl peptides also catalyze the same renaturation. A linear correlation was found between the thermal stabilization afforded to the DNA by the various peptides and their ability to "catalyze" DNA strand renaturation.     

Molecular map of Chromosome 19 including three genes affecting bleeding time: ep,ru, and bm

The mouse ruby eye (ru) and pale ear (ep) pigment dilution genes cause platelet storage pool deficiency (SPD) and prolonged bleeding times. The brachymorphic (bm) gene, in addition to causing skeletal abnormalities, is also associated with prolonged bleeding times. All three hemorrhagic genes are found within 10 cM on Chromosome (Chr) 19. In this study, 15 microsatellite markers and five cDNAs, spanning 21 cM of Chr 19, were mapped in relation to the bm, ep, and ru genes in 457 progeny of an interspecific backcross utilizing the highly inbred strain PWK derived from the Mus musculus musculus species. Several markers were found to be closely linked to the three genes and should be useful as entry points in their eventual molecular identification.