First-principle solubilities of alkali and alkaline earth metals in Mg-B alloys

By devising a novel framework, we present a comprehensive theoretical study of solubilities of alkali (Li, Na, K, Rb, Cs) and alkaline earth (Be, Ca, Sr, Ba) metals in the he boron-rich Mg-B system. The study is based on first-principle calculations of solutes formation energies in MgB$_2$, MgB$_4$, MgB$_7$ alloys and subsequent statistical-thermodynamical evaluation of solubilities. The advantage of the approach consists in considering all the known phase boundaries in the ternary phase diagram. Substitutional Na, Ca, and Li demonstrate the largest solubilities, and Na has the highest (0.5-1 % in MgB$_7$ at $T=650-1000$ K). All the considered interstitials have negligible solubilities. The solubility of Be in MgB$_7$ can not be determined because the corresponding low-solubility formation energy is negative indicating the existence of an unknown ternary ground state. We have performed a high-throughput search of ground states in binary Mg-B, Mg-$A$, and B-$A$ systems, and we construct the ternary phase diagrams of Mg-B-$A$ alloys based on the stable binary phases. Despite its high temperature observations, we find that Sr$_{9}$Mg$_{38}$ is not a low-temperature equilibrium structure. We also determine two new possible ground states CaB$_{4}$ and RbB$_{4}$, not yet observed experimentally.Comment: 5 figure

Phorbol ester binding and phorol ester-induced arachidonic acid metabolism in a highly responsive murine fibrosarcoma cell line and in a less-responsive variant

Phorbol ester binding was examined in two lines of murine fibrosarcoma cells. The two cell lines were isolated from the same parent tumor but respond differentially to stimulation with phorbol esters. In one of the lines, these agents stimulate a rapid attachment and spreading response and induce directional migration. The other cell line does not migrate in response to stimulation with phorbol esters and the attachment and spreading response is slow. The cell line which responds actively to phorbol ester stimulation is highly malignant when injected into syngeneic animals while the other line is of low tumorigenicity and is virtually non-metastatic. In spite of these differences, both lines were found in the present study to bind [ 3 H]4β-phorbol-12β, 13α-dibutyrate in a receptor-mediated fashion. The characteristics of binding were virtually identical between the two cell lines. In additional studies, arachidonic acid metabolism was examined in the same two lines. In the highly responsive line, PMA stimulated a rapid release of [ 3 H]arachidonic acid and its conversion into cyclooxygenase and lipoxygenase products. In the less-responsive line, PMA stimulated a slower release of [ 3 H]arachidonic acid from prelabeled cells. The quantity of arachidonic acid metabolites produced was also much less. These studies suggest that the disparity between the two cell lines in their response to phorbol ester stimulation is not the result of differences in the initial interaction between the cells and ligand but may result from alterations in their signal transductance mechanism. This may be the result of inherent differences in capacity for arachidonic acid metabolism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42593/1/10585_2004_Article_BF00053473.pd

Viral Perturbations of Host Networks Reflect Disease Etiology

Many human diseases, arising from mutations of disease susceptibility genes (genetic diseases), are also associated with viral infections (virally implicated diseases), either in a directly causal manner or by indirect associations. Here we examine whether viral perturbations of host interactome may underlie such virally implicated disease relationships. Using as models two different human viruses, Epstein-Barr virus (EBV) and human papillomavirus (HPV), we find that host targets of viral proteins reside in network proximity to products of disease susceptibility genes. Expression changes in virally implicated disease tissues and comorbidity patterns cluster significantly in the network vicinity of viral targets. The topological proximity found between cellular targets of viral proteins and disease genes was exploited to uncover a novel pathway linking HPV to Fanconi anemia