Genetic similarity promotes evolution of cooperation under lethal intergroup competition

Altruism (helping others at a cost to oneself) may evolve via group selection if the cost of altruism to the individual is compensated for by growth differences among groups when (1) there is high genetic variation among members of different groups; (2) more altruistic groups grow faster and (3) between-group migration is low. Nevertheless, group selection may not fully explain the actual evolution of helping behaviour if between-group migration was sufficiently common to have reduced between-group genetic variance. Lethal intergroup competition, which amplifies such growth differences between groups, appears to have been frequent in humans'; ancestral environments and could bear importantly on the evolution of altruism. Here we show that between-group migration and resulting genetic similarity can promote the evolution of costly helping behavior in the context of lethal intergroup conflict, albeit by selection at the individual level and not by group selection. The standard group selection models do not capture such basic elements of lethal intergroup competition as the possibility of an individual's altruism being critical to the group's success when that possibility is inversely proportional to genetic variation among members of the competing groups

Steric Influences in Octahedral Cohaloximes. The Crystal and Molecular Structure of trans-methylhis(dimethylglyoximato) (phosphite)cobalt(III) Complexs with Phosphite=P(OMe)2Ph and P(OMe)Ph2

The crystal structures of the title compounds, (P(OMe)2Ph)Co( DH)2Me (I) and (P(0Me)Ph2)Co(DH)2Me (II), are reported. Compound I crystallizes in the orthorhombic system, space group Pbca, with cell parameters a = 14.652(7), b = 26.45(1) and c = 11.330(6) A and z = 8; compound II crystallizes in the monoclinic system, space group P21 with cell parameters a = 9.423(7), b = 15.184(8), c = 8.948 (7) A and ~ = 100.50(9)0 , Z = 2. Both structures were solved by conventional Patterson and Fourier methods and refined by the block diagonal least-squares method to final R values of 0.033(1) and 0.034(II), using 2108 for I and 2063 for II independent reflections with I > 30\u27(1). In both compounds the cobalt atom has a distorted octahedral geometry, the two DH units occupying the equatorial positions and Me and the P-ligand the axial ones. The Co-C and Co- P bond lengths are 2.013(5) and 2.287(1) A in I and 2.019(6) and 2.352(1) A in II, respectively. Linear correlation between Co-P bond lengths and Tolman\u27s cone angles in the series RaPCo(DH)2Me is found, with the exception of the P(OMe)Ph2 derivative. Furthermore, the linear relationship between the above Co-P distances and those reported for analogous chloro-derivatives, already found for phosphines, is valid for I but not for II

Steric Influences in Octahedral Cohaloximes. The Crystal and Molecular Structure of trans-methylhis(dimethylglyoximato) (phosphite)cobalt(III) Complexs with Phosphite=P(OMe)2Ph and P(OMe)Ph2

The crystal structures of the title compounds, (P(OMe)2Ph)Co( DH)2Me (I) and (P(0Me)Ph2)Co(DH)2Me (II), are reported. Compound I crystallizes in the orthorhombic system, space group Pbca, with cell parameters a = 14.652(7), b = 26.45(1) and c = 11.330(6) A and z = 8; compound II crystallizes in the monoclinic system, space group P21 with cell parameters a = 9.423(7), b = 15.184(8), c = 8.948 (7) A and ~ = 100.50(9)0 , Z = 2. Both structures were solved by conventional Patterson and Fourier methods and refined by the block diagonal least-squares method to final R values of 0.033(1) and 0.034(II), using 2108 for I and 2063 for II independent reflections with I > 30\u27(1). In both compounds the cobalt atom has a distorted octahedral geometry, the two DH units occupying the equatorial positions and Me and the P-ligand the axial ones. The Co-C and Co- P bond lengths are 2.013(5) and 2.287(1) A in I and 2.019(6) and 2.352(1) A in II, respectively. Linear correlation between Co-P bond lengths and Tolman\u27s cone angles in the series RaPCo(DH)2Me is found, with the exception of the P(OMe)Ph2 derivative. Furthermore, the linear relationship between the above Co-P distances and those reported for analogous chloro-derivatives, already found for phosphines, is valid for I but not for II

A mathematical model for the sequestering of chemical contaminants by magnetic particles

A mathematical model is developed and implemented to characterize the pickup of various liquid chemical contaminants by polyethylene-coated magnetic particles. The model and its associated experimental and analytical protocols were applied to a wide range of liquid chemicals in order to gain insights into the physical basis for the pickup phenomenon. The characteristics of the pickup isotherms range between “ideal” and “nonideal” behaviors that are reflected in the mathematical model by a single parameter, �0, where �0=1 corresponds to ideal behavior and �0�1 corresponds to a departure from idealized behavior that is directly quantified by the magnitude of �0. The parameter �0 is also related to the efficiency of pickup, and since most isotherms observed in the study deviate from ideality, the high efficiency of pickup observed in these systems has been attributed in part to this deviation. The proposed model and its associated experimental and analytical protocols demonstrate great potential for the systematic evaluation of the uptake of chemical contaminants using magnetic particle technology

Towards Enhanced Performance Thin-film Composite Membranes via Surface Plasma Modification

Advancing the design of thin-film composite membrane surfaces is one of the most promising pathways to deal with treating varying water qualities and increase their long-term stability and permeability. Although plasma technologies have been explored for surface modification of bulk micro and ultrafiltration membrane materials, the modification of thin film composite membranes is yet to be systematically investigated. Here, the performance of commercial thin-film composite desalination membranes has been significantly enhanced by rapid and facile, low pressure, argon plasma activation. Pressure driven water desalination tests showed that at low power density, flux was improved by 22% without compromising salt rejection. Various plasma durations and excitation powers have been systematically evaluated to assess the impact of plasma glow reactions on the physico-chemical properties of these materials associated with permeability. With increasing power density, plasma treatment enhanced the hydrophilicity of the surfaces, where water contact angles decreasing by 70% were strongly correlated with increased negative charge and smooth uniform surface morphology. These results highlight a versatile chemical modification technique for post-treatment of commercial membrane products that provides uniform morphology and chemically altered surface properties