Strengths of sulfur-basalt concretes

Sulfur used in bonding high strength basalt aggregates to form sulfur-basalt concrete

Phase Diagrams of Quasispecies Theory with Recombination and Horizontal Gene Transfer

We consider how transfer of genetic information between individuals influences the phase diagram and mean fitness of both the Eigen and the parallel, or Crow-Kimura, models of evolution. In the absence of genetic transfer, these physical models of evolution consider the replication and point mutation of the genomes of independent individuals in a large population. A phase transition occurs, such that below a critical mutation rate an identifiable quasispecies forms. We generalize these models of quasispecies evolution to include horizontal gene transfer. We show how transfer of genetic information changes the phase diagram and mean fitness and introduces metastability in quasispecies theory, via an analytic field theoretic mapping.Comment: 5 pages, 1 figure, to appear in Physics Review Letter

Fermi Liquids and the Luttinger Integral

The Luttinger Theorem, which relates the electron density to the volume of the Fermi surface in an itinerant electron system, is taken to be one of the essential features of a Fermi liquid. The microscopic derivation of this result depends on the vanishing of a certain integral, the Luttinger integral $I_{\rm L}$, which is also the basis of the Friedel sum rule for impurity models, relating the impurity occupation number to the scattering phase shift of the conduction electrons. It is known that non-zero values of $I_{\rm L}$ with $I_{\rm L}=\pm\pi/2$, occur in impurity models in phases with non-analytic low energy scattering, classified as singular Fermi liquids. Here we show the same values, $I_{\rm L}=\pm\pi/2$, occur in an impurity model in phases with regular low energy Fermi liquid behavior. Consequently the Luttinger integral can be taken to characterize these phases, and the quantum critical points separating them interpreted as topological.Comment: 5 pages 7 figure

Duramycin-induced calcium release in cancer cells

Introduction: Duramycin through binding with phosphatidylethanolamine (PE) has shown potential to be an effective anti-tumour agent. However its mode of action in relation to tumour cells is not fully understood. Methods: PE expression on the surface of a panel of cancer cell lines was analysed using duramycin and subsequent antibody labelling then analysed by flow cytometry. Cell viability was also assessed via flow cytometry using annexin V and propidium iodide (PI). Calcium ion (Ca²⁺) release by tumour cells in response to duramycin was determined by spectrofluorometry following incubation with Fluo-3, AM. Confocal microscopy was performed on the cancer cell line AsPC-1 to assess real time cell response to duramycin treatment. Results: Duramycin was able to detect cell surface PE expression on all 15 cancer cell lines screened, which was shown to be duramycin concentration dependent. However higher concentrations induced necrotic cell death. Duramycin induced calcium ion (Ca²⁺) release from the cancer cell lines also in a concentration and time dependent manner. Confocal microscopy showed an influx of PI into the cells over time and induced morphological changes. Conclusion: Duramycin induces Ca²⁺ release from cancer cell lines in a time and concentration dependent relationship

Temperature dependence of the phonon entropy of vanadium

The phonon density-of-states (DOS) of elemental vanadium was measured at elevated temperatures by inelastic neutron scattering. The phonon softening predicted by thermal expansion against the bulk modulus is much larger than the measured shifts in phonon energies. We conclude that the phonon anharmonicities associated with thermal expansion are largely canceled by effects from phonon-phonon scattering. Prior measurements of the heat capacity and calculations of the electronic entropy of vanadium are assessed, and consistency requires an explicit temperature dependence of the phonon DOS. Using data from the literature, similar results are found for chromium, niobium, titanium, and zirconium