Micropores and biofilms of soils may protect bacteria against chemical stress, predation, and competition phenomena, explaining the great diversity and robustness of soil microbial communities and functions. We used sequential dispersion/density gradient centrifugation to separate free and loosely attached cells (FLA) from strongly attached cells (SA). The two fractions of the soils communities...

AuNPs ranging in 20 to 300 nm size were synthesized at a room temperature using Yucca filamentosa leaf extract. Diverse nanomaterial morphologies were obtained by varying the extract concentration, reaction pH, and temperature. While low volumes of extract (0.25 and 0.5 mL) induced the formation of microscale Au sheets with edge length greater than 1 μm, high volumes yielded spherical particles...

Watson and Crick (1953), and Kornberg (1967). The author assumes no prior knowledge. For example when discussing the observations of Meselson and Stahl not only does he include the usual symbolic illustrations of semiconservative DNA replication, but also a figure of equilibrium density gradient centrifugation. Each chapter ends with a summary of the observations presented which answer the orig...

The origin of the density heterogeneity of platelets was studied by measuring the survival of density subpopulations of rabbit platelets separated by discontinuous Stractan density gradient centrifugation. When a total population of 5tCr-labeled platelets was injected into recipient rabbits. the relative specific radioactivity of the most dense platelets decreased rapidly. In contrast. that of ...

Preparations of nucleic acids obtained by extraction of mouse liver, HeLa cells and cell fractions with phenol and deoxycholate have been characterized with regard to the differential solubility of ribonucleic acid and deoxyribonucleic acid in ethanol, density-gradient centrifugation and the presence of high-molecular-weight contaminants. Ribonucleic acid obtained by this method is less soluble...

The decline of species richness from equator to pole, or latitudinal diversity gradient (LDG), is nearly universal among clades of living organisms, yet whether it was such a pervasive pattern in the geologic past remains uncertain. Here, we calculate the strength of the LDG for terrestrial mammals in North America over the past 65 My, using 27,903 fossil occurrences of Cenozoic terrestrial mam...

Time-lapse resistivity measurements and groundwater geochemistry were used to study salinity effect on groundwater aquifer at the ex-promontory-land of Carey Island in Malaysia. Resistivity was measured by ABEM Terrameter SAS4000 and ES10-64 electrode selector. Relationship between earth resistivity and total dissolved solids (TDS) was derived, and with resistivity images, used to identify wate...

Breakage and fractionation of respiratory competent yeast in the presence of ethidium bromide, and subsequent centrifugation of a detergent lysate of the mitochondrial fraction by the dye-buoyant-density technique, results in the isolation of closed-circular DNA. After removal of bound dye, this DNA has two components when analyzed by equilibrium buoyant density in the analytical ultracentrifug...

One way of improving the resolution of particles by size is to minimize the difference in RCF between the top and bottom of the sample. Practically this is achieved by layering the sample as a narrow band over a continuous density gradient. This is called rate-zonal gradient (sedimentation velocity) centrifugation; the conditions are chosen such that ρρ always remains greater than ρl. In a cont...