The effect of oxidation state on the viscosity of melts in the system Na2O-FeO-Fe2O3-SiO2

The viscosities of two melts in the system Na2O-FeO-Fe2O3-SiO2 have been measured as a function of oxidation state. The experiments were conducted by concentric-cylinder viscometry, on melts equilibrated with gas mixtures in a vertical tube, gas-mixing furnace. Viscosity determinations were made during stepwise reduction and oxidation of the melts. 57Fe Mössbauer spectra were obtained on quenched melt samples recovered during the viscometry experiments. In addition, a series of loop fusion experiments were performed at calibrated ƒO2 values in order to relate viscosity determinations directly to ƒO2. The viscosities of acmite and NS4F40 (Na-rich and Si-poor relative to acmite) melts decrease with reduction of Fe in the melts, as nonlinear functions of , yielding a region of viscosity invariance at moderate to low values of (<0.4). The 57Fe Mössbauer spectra of quenched melts as a function of indicate the presence of one (network-modifying) ferrous species and two ferric species with ferric iron acting dominantly as a network-former in oxidized melts and dominantly as a network-modifier in reduced melts. The presence of two ferric iron species produces a minimum in the degree of polymerization of the melt at intermediate values of : the region of viscosity invariance corresponds to this minimum. If viscosity is positively correlated with polymerization for all values of then the viscosity of very reduced melts will increase with reduction, as the melt polymerizes. The effect of oxidation state on viscosity is large and illustrates that ferric iron should be considered as a separate component in calculation schemes for estimating the viscosity of natural magmas

Motility at the origin of life: Its characterization and a model

Due to recent advances in synthetic biology and artificial life, the origin of life is currently a hot topic of research. We review the literature and argue that the two traditionally competing "replicator-first" and "metabolism-first" approaches are merging into one integrated theory of individuation and evolution. We contribute to the maturation of this more inclusive approach by highlighting some problematic assumptions that still lead to an impoverished conception of the phenomenon of life. In particular, we argue that the new consensus has so far failed to consider the relevance of intermediate timescales. We propose that an adequate theory of life must account for the fact that all living beings are situated in at least four distinct timescales, which are typically associated with metabolism, motility, development, and evolution. On this view, self-movement, adaptive behavior and morphological changes could have already been present at the origin of life. In order to illustrate this possibility we analyze a minimal model of life-like phenomena, namely of precarious, individuated, dissipative structures that can be found in simple reaction-diffusion systems. Based on our analysis we suggest that processes in intermediate timescales could have already been operative in prebiotic systems. They may have facilitated and constrained changes occurring in the faster- and slower-paced timescales of chemical self-individuation and evolution by natural selection, respectively.Comment: 29 pages, 5 figures, Artificial Lif

Mens rea in joint enterprise: a role for endorsement?

This paper argues that the problems commonly associated with the joint enterprise doctrine might be alleviated by supplementing the cognitive mens rea standard of foresight with a volitional element that looks to how the defendant related to the foreseen risk. A re-examination of the case law suggests that a mens rea conception of foresight plus endorsement might be within interpretative reach. The paper considers possible objections to such a development but ultimately rejects them. It concludes that it is not necessary to wait for Parliament to put in place reforms: joint enterprise is a creature of the common law, and the common law is able to tame it unaided

Surviving the global information security war

Lessons for those running any organisation that wishes to survive the rising tide of online crime, by Philip Virg

Viscosities of melts in the Na2O---FeO---Fe2O3---SiO2 system and factors controlling relative viscosities of fully polymerized silicate melts

Na2O---B2O3---SiO2 and Na2O-Ga2O3 viscosities decrease in the order aluminosilicate > ferrosilicate, (galliosilicate ?) > borosilicate. Thp electronegativities of the trivalent cations are inversely correlated with the relative viscosities of melts in these systems. Similarly, the electronegativities of network-stabilizing cations are inversely correlated with melt viscosity for alkali and alkaline-earth aluminosilicate melt systems. The variation in the viscosity of tectosilicate melts is correlated with estimated average T-O-T bond angles, and exothermic heats of solution of quench glasses. Structural controls of viscosity discussed are tetrahedral ordering and relative bond strengths. The acmite component in natural, peralkaline, silicic volcanics will not contribute directly to high melt viscosities for these lavas

Pengaruh Kreativitas Mahasiswa dan Komunikasi Interpersonal dengan Dosen terhadap Prestasi Belajar Mahasiswa Prodi Pendidikan Ekonomi STKIP PGRI Sumatera Barat

This research was conducted in the study program of economic education STKIP PGRI West Sumatra, on the effect of student creativity and interpersonal communication with faculty on student achievement education department of economics. The purpose of this study were (1) To determine the effect of creativity of students on student achievement education department of economics STKIP PGRI West Sumatra. (2) To determine the effect of interpersonal communication with faculty on student learning achievement of the education department of economics STKIP PGRI West Sumatra. (3) To determine the effect of students creativity and interpersonal communication with faculty on student learning achievement of the education department of economics STKIP PGRI West Sumatra.The results of data analysis showed that (1) There is a positive and significant impact of student creativity on student achievement education department of economics STKIP PGRI West Sumatra, this is evidenced by the regression coefficient of 0.560, with a value of 4,927 t count> t table 1.6622 seen from sig 0.000 t table 0.000 1.6622 seen from the sig F table value of 3.10 and a significant of 0.002. Sig value <α, namely (0.000 <0.05)

Re-evaluation of the cation distribution in orthopyroxenes by the Moessbauer effect

Mossbauer spectra of orthopyroxenes at low temperature