Antarctic meteorites: MIL 07687 and ALHA 77307 - A novel approach of in-situ micro-XRD study of the matrix

第6回極域科学シンポジウム[OA] 南極隕石11月16日（月）　国立国語研究所 2階 講

A 20‐year study of melt processes over Larsen C Ice Shelf using a high‐resolution regional atmospheric model: Part 2, Drivers of surface melting

Quantifying the relative importance of the atmospheric drivers of surface melting on the Larsen C ice shelf is critical in the context of recent and future climate change. Here, we present analysis of a new multi-decadal, high-resolution model hindcast using the Met Office Unified Model (MetUM), described in part 1 of this study. We evaluate the contribution of various atmospheric conditions in order to identify and rank, for the first time, the most significant causes of melting over the recent past. We find the primary driver of surface melting on Larsen C is solar radiation. Foehn events are the second most important contributor to surface melting, especially in non-summer seasons when less solar radiation is received at the surface of the ice shelf. Thirdly, cloud influences surface melting via its impact on the surface energy balance (SEB); when the surface temperature is warm enough, cloud can initiate or prolong periods of melting. Lastly, large-scale circulation patterns such as the Southern Annular Mode (SAM), El Niño Southern Oscillation (ENSO) and Amundsen Sea Low (ASL) control surface melting on Larsen C by influencing the local meteorological conditions and SEB. These drivers of melting interact and overlap, for example, the SAM influences the frequency of foehn, commonly associated with leeside cloud clearances and sunnier conditions. Ultimately, these drivers matter because sustained surface melting on Larsen C could destabilise the ice shelf via hydrofracturing, which would have consequences for the fate of the ice shelf and sea levels worldwide

First-principles Calculation of the Formation Energy in MgO-CaO Solid Solutions

The electronic structure and total energy were calculated for ordered and disordered MgO-CaO solid solutions within the multiple scattering theory in real space and the local density approximation. Based on the dependence of the total energy on the unit cell volume the equilibrium lattice parameter and formation energy were determined for different solution compositions. The formation energy of the solid solutions is found to be positive that is in agreement with the experimental phase diagram, which shows a miscibility gap.Comment: 11 pages, 3 figure

A mutli-technique search for the most primitive CO chondrites

As part of a study to identify the most primitive COs and to look for weakly altered CMs amongst the COs, we have conducted a multi-technique study of 16 Antarctic meteorites that had been classified as primitive COs. For this study, we have determined: (1) the bulk H, C and N abundances and isotopes, (2) bulk O isotopic compositions, (3) bulk modal mineralogies, and (4) for some selected samples the abundances and compositions of their insoluble organic matter (IOM). Two of the 16 meteorites do appear to be CMs – BUC 10943 seems to be a fairly typical CM, while MIL 090073 has probably been heated. Of the COs, DOM 08006 appears to be the most primitive CO identified to date and is quite distinct from the other members of its pairing group. The other COs fall into two groups that are less primitive than DOM 08006 and ALH 77307, the previously most primitive CO. The first group is composed of members of the DOM 08004 pairing group, except DOM 08006. The second group is composed of meteorites belonging to the MIL 03377 and MIL 07099 pairing groups. These two pairing groups should probably be combined. There is a dichotomy in the bulk O isotopes between the primitive (all Antarctic finds) and the more metamorphosed COs (mostly falls). This dichotomy can only partly be explained by the terrestrial weathering experienced by the primitive Antarctic samples. It seems that the more equilibrated samples interacted to a greater extent with 16O-poor material, probably water, than the more primitive meteorites

Monetary Policy Rules and Directions of Causality: a Test for the Euro Area

Using a VAR model in first differences with quarterly data for the euro zone, the study aims to ascertain whether decisions on monetary policy can be interpreted in terms of a “monetary policy rule” with specific reference to the so-called nominal GDP targeting rule (Hall and Mankiw, 1994; McCallum, 1988; Woodford, 2012). The results obtained indicate a causal relation proceeding from deviation between the growth rates of nominal gross domestic product (GDP) and target GDP to variation in the three-month market interest rate. The same analyses do not, however, appear to confirm the existence of a significant inverse causal relation from variation in the market interest rate to deviation between the nominal and target GDP growth rates. Similar results were obtained on replacing the market interest rate with the European Central Bank refinancing interest rate. This confirmation of only one of the two directions of causality does not support an interpretation of monetary policy based on the nominal GDP targeting rule and gives rise to doubt in more general terms as to the applicability of the Taylor rule and all the conventional rules of monetary policy to the case in question. The results appear instead to be more in line with other possible approaches, such as those based on post Keynesian analyses of monetary theory and policy and more specifically the so-called solvency rule (Brancaccio and Fontana, 2013, 2015). These lines of research challenge the simplistic argument that the scope of monetary policy consists in the stabilization of inflation, real GDP, or nominal income around a “natural equilibrium” level. Rather, they suggest that central banks actually follow a more complex purpose, which is the political regulation of the financial system with particular reference to the relations between creditors and debtors and the related solvency of economic units

Advances in ab-initio theory of Multiferroics. Materials and mechanisms: modelling and understanding

Within the broad class of multiferroics (compounds showing a coexistence of magnetism and ferroelectricity), we focus on the subclass of "improper electronic ferroelectrics", i.e. correlated materials where electronic degrees of freedom (such as spin, charge or orbital) drive ferroelectricity. In particular, in spin-induced ferroelectrics, there is not only a {\em coexistence} of the two intriguing magnetic and dipolar orders; rather, there is such an intimate link that one drives the other, suggesting a giant magnetoelectric coupling. Via first-principles approaches based on density functional theory, we review the microscopic mechanisms at the basis of multiferroicity in several compounds, ranging from transition metal oxides to organic multiferroics (MFs) to organic-inorganic hybrids (i.e. metal-organic frameworks, MOFs)Comment: 22 pages, 9 figure

Alteration conditions on the CM and CV parent bodies – Insights from hydrothermal experiments with the CO chondrite Kainsaz

This study simulates the hydrothermal conditions that existed on carbonaceous chondrite planetesimals in the early solar system. Our experiments are relevant to alteration conditions that existed on the CV parent body and the late stage oxidizing alteration of the CM chondrites. We conducted 11 alteration experiments using chips of the CO3 chondrite Kainsaz. Water was added to each chip and sealed in separate Teflon reaction vessels for 175 days. Samples were altered at different initial water-to-rock ratios (W/R: 0.2–0.8) and temperatures (50 °C and 150 °C). Isotopically doped 17O-rich heavy water (δ17O: +64.5‰) was used in five runs. All samples experienced pronounced alteration under a partially open system environment where gases were able to escape the reaction vessels. The style of alteration (Fe-alkali metasomatism) is similar in all cases. The principal alteration minerals formed are Fe-oxyhydroxides (goethite) and Fe-oxides (magnetite), with smaller quantities of Fe-sulphides. Minor phases formed include fayalite, sulphates (gypsum and Fe-sulphate) and calcite. Nanophase, poorly crystalline phyllosilicates formed in the high-temperature samples but are absent from the low-temperature experiments. In all instances, Mg-rich chondrule silicates remained chemically unaltered although some grains suffered hydrothermal fracture. Chondrule mesostases remained largely unaffected. By contrast, kamacite readily dissolved, acting as a source of Fe and Ni for the fluid phase. A new generation of nanophase Fe-sulphides formed within the matrix, while pre-existing pyrrhotite group sulphides experienced Ni enrichment ( 10 at%) were formed in the 150 °C samples, most likely by sulphidation of taenite. Matrix alteration cemented grains together, reducing porosity. The fine-grained matrix shows highly variable degrees of alteration, with minimally altered matrix in direct contact with regions of heavily altered matrix. Chondrule fine-grained rims (FGRs) were preferentially altered. These textures imply that the unaltered matrix readily reacted with the fluid phase, resulting in an efficient depletion of dissolved ions (Fe2+ and S2-), limiting reactivity until further primary phases were dissolved. At larger length-scales the distribution of heavily altered matrix reveals the presence of large ∼100 µm wide channels that meander through the specimens. Their textures resemble features seen in some CM chondrites and the ungrouped CO-like chondrite MIL 07687. We suggest that alteration fronts developed by sustained rapid reaction of matrix with dissolved cations in solution. Our observations provide a mechanism for the establishment and maintenance of geochemical microenvironments on chondritic asteroids. The effects of open system loss notwithstanding, our experiments demonstrate that more advanced alteration is correlated with higher initial W/R ratios. The use of 17O-rich doped water allowed the isotopic effects of aqueous alteration to be observed. Bulk rock compositions evolved towards the initial water composition, reflecting the incorporation of heavy O into hydrated minerals. Additionally, altered samples shifted in δ18O space, reflecting the competing effects of water–mineral fractionation and mass fractionation due to the preferential escape of isotopically light water

Erasmus Language students in a British University – a case study

Students’ assessment of their academic experience is actively sought by Higher Education institutions, as evidenced in the National Student Survey introduced in 2005. Erasmus students, despite their growing numbers, tend to be excluded from these satisfaction surveys, even though they, too, are primary customers of a University. This study aims to present results from bespoke questionnaires and semi-structured interviews with a sample of Erasmus students studying languages in a British University. These methods allow us insight into the experience of these students and their assessment as a primary customer, with a focus on language learning and teaching, university facilities and student support. It investigates to what extent these factors influence their levels of satisfaction and what costs of adaptation if any, they encounter. Although excellent levels of satisfaction were found, some costs affect their experience. They relate to difficulties in adapting to a learning methodology based on a low number of hours and independent learning and to a guidance and support system seen as too stifling. The results portray this cohort’s British University as a well-equipped and well-meaning but ultimately overbearing institution, which may indicate that minimising costs can eliminate some sources of dissatisfaction

Gauge and Scheme Dependence of Mixing Matrix Renormalization

We revisit the issue of mixing matrix renormalization in theories that include Dirac or Majorana fermions. We show how a gauge-variant on-shell renormalized mixing matrix can be related to a manifestly gauge-independent one within a generalized ${\bar {\rm MS}}$ scheme of renormalization. This scheme-dependent relation is a consequence of the fact that in any scheme of renormalization, the gauge-dependent part of the mixing-matrix counterterm is ultra-violet safe and has a pure dispersive form. Employing the unitarity properties of the theory, we can successfully utilize the afore-mentioned scheme-dependent relation to preserve basic global or local symmetries of the bare Lagrangian through the entire process of renormalization. As an immediate application of our study, we derive the gauge-independent renormalization-group equations of mixing matrices in a minimal extension of the Standard Model with isosinglet neutrinos.Comment: 31 pages, LaTeX, uses axodraw.st