25,927 research outputs found
Partition coefficient of phosphorus between liquid metal and silicate melt with implications for the Martian magma ocean
No full textPhosphorus in Martian mantle is believed to be five to ten times more abundant than in Earth's mantle, and the distribution of this essential ingredient for life between different deep reservoirs is critical for understanding the habitability of the red planet. In this study, we investigated the behavior of phosphorus in a Martian magma ocean scenario, and measured the partition coefficient of phosphorus (DP) between liquid metal and silicate melt within the pressure range of 3–8 GPa, temperatures between 1973 and 2173 K and oxygen fugacity ranging from −1.5 to ~ −2.5 as normalized to the iron-wüstite oxygen buffer. Our results show DP increasing with pressure but decreasing with temperature. A decrease of oxygen fugacity has a negative effect on DP. The moderately siderophile character of phosphorus indicates that the Martian core might be an important reservoir of phosphorous. Based on our experimental results and phosphorus abundance in Martian mantle and bulk Mars, a minimum pressure of 5.8–10.4 GPa is estimated at the base of Martian magma ocean or during the impact melting if a contribution from the late accretion scenario is taken into account. The shallow Martian magma ocean would avail the preservation of volatiles after the rapid solidification of the planet
Magnetic properties of Fe-ions in Transition metal substituted gamma-TFe3N (T=Co, Ni, Mn)
No full textFe, Ni and Co nitrides with perovskite structures are conducting ferromagnets with high mechanical resistance, low coercitivity and large saturation moments, suitable for exploitation in magnetic and magnetoresistive devices. Promising applications in high density recording media and sensors require tailoring nanostructures from the parent bulk compound/alloy, with the largest possible unit cell magnetization. This depends on the combined effects of unit cell volume, local symmetry and T–Fe ions interaction that we investigate by spin-polarized all electron FPLMTO calculations. We simulate systematically bulk Fe3N unit cells with substitutional T atoms at FeI (corner) or FeII (face) site to ascertain the interplay of T-Fe (electronic), T-N ( volumic) and T-Fe-N (volumic and electronic) interactions. The magnetic moments per atom and f.u. are calculated at i) three values of the experimental lattice parameter (in a.u.) a0= 7.1715 [1], a1=7.1753 [2], a2=7.1621 [3], and ii) for different XC-approximations. The conditions that in Fe4N lead to the formation of saturated (corner) and unsaturated (face) moments are found also in the alloys considered here. This twofold behaviour is less pronounced in CoFe3N but striking in MnFe3 where also spin flip of the Mn moments occurs. MnFe3N is the only compound where Mn substitution of Fe induces a quite dramatic decrease of the other Fe moment
Spatially-localized time dependent solutions including turbulence and their interactions in 2D Kolmogorov flow
No full textIn 2D Kolmogorov flow in small aspect ratio domains, spatially-localized solutions such as kink, traveling or time-dependent kink-antikink pars coexist. However, the conservation of the flow rate in the y direction strongly restrict combination of localized solutions and their positioning. We find that by adding a homogeneous flow U y their positioning is controlled and each of localized solutions including a spatially-localized chaos is isolated. Numerical results suggest that these isolated solutions can be elements constructing a whole flow
The Tradition of Telling and the Desire of Showing in Ge Fei’s ‘Fictional Minds’
Full text linkThis paper examines Ge Fei 格非’s attempt to reconcile the inner world oh his characters and the outward reality in his in his recent trilogy,
Renmian taohua 人面桃花 (Peach Blossom-beauty, 2004), Shanhe ru meng 山河入梦 (Mountains and Rivers Fall Asleep, 2007) and Chunjin jiangnan 春尽江南 (End of Spring in Jiangnan, 2011). Since his novel, Diren 敌人 (The Enemy, 1991), Ge Fei has focussed on the individual search to negotiate between his/her own subjectivity and the objective world around. Pesaro tries to show how the author, in depicting history and the reality as perceived by these fictional centres of consciousness, tends to gradually move from an indirect approach to a direct one. Chen Zhongyi 陈众议 (2012) points out the inner contradiction of Ge Fei’s style, which he defines as ‘classical’ (gudian 古典) and ‘avant-garde’ (xianfeng 先锋) at the same time, actually, as Pesaro points out, a sophisticated merging of both styles rather than a contradiction, ‘the sublimation of some modernist techniques within a more traditional, essentially Chinese, narrative frame.’ Ge Fei choses to narrate the human mind in its complexity and in its constant interaction with the outer world by combining traditional subjectivity and implicitness with modern devices such as stream of consciousness, the descriptions of actions and objects, and the use of poetry to represent emotions and mental activities. Thus he creates a completely new and independent narrative style, achieving both continuity and discontinuity with Chinese tradition
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
Full text linkIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
The compression behavior of blödite at low and high temperature up to ∼10 GPa. Implications for the stability of hydrous sulfates on icy planetary bodies
No full textRecent satellite inferences of hydrous sulfates as recurrent minerals on the surface of icy planetary bodies
link with the potential mineral composition of their interior. Blödite, a mixed Mg-Na sulfate, is here
taken as representative mineral of icy satellites surface to investigate its crystal structure and stability at
conditions of the interior of icy bodies. To this aim we performed in situ synchrotron angle-dispersive
X-ray powder diffraction experiments on natural blödite at pressures up to ∼10.4 GPa and temperatures
from ∼118.8 K to ∼490.0 K using diamond anvil cell technique to investigate the compression behavior
and establish a low-to-high temperature equation of state that can be used as reference when modeling
the interior of sulfate-rich icy satellites such as Ganymede.
The experimentally determined volume expansivity, α, varies from 7.6 (7) 10−5 K−1 at 0.0001 GPa
(from 118.8 to 413.15 K) to 2.6 (3) 10−5 K−1 at 10 GPa (from 313.0 to 453.0 K) with a δα/δP coefficient = −5.6(9)10−6 GPa−1 K−1.
The bulk modulus calculated from the least squares fitting of P-V data on the isotherm at 413 K using
a second-order Birch - Murnaghan equation of state is 38(5) GPa, which gives the value of δK/δT equal to
0.01(5) GPa K−1. The thermo-baric behavior of blödite appears strongly anisotropic with c lattice parameter being more deformed with respect to a and b.
Thermogravimetric analyses performed at ambient pressure showed three endotherms at 413 K, 533 K
and 973 K with weight losses of approximately 11%, 11% and 43% caused by partial dehydration, full dehydration and sulfate decomposition respectively. Interestingly, no clear evidence of dehydration was observed up to ∼453 K and ∼10.4 GPa, suggesting that pressure acts to stabilize the crystalline structure of
blödite.
The data collected allow to write the following equation of state,
V(P, T)=V0[1+7.6(7)10−5T−0.026(3)P−5.6(9)10−6PT−6.6(9)10−6PT)]
from which the density of blödite can be determined at conditions of the mantle of the large icy
satellites of Jupiter.
Blödite has higher density, bulk modulus and thermal stability than similar hydrous sulfates (e.g.
mirabilite and epsomite) implying, therefore, a different contribution of these minerals to the extent of
deep oceans in icy planets and their distribution over the local geotherm
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