Rb-Sr Isotopic Studies Of Antarctic Lherzolitic Shergottite Yamato 984028

Yamato 984028 is a Martian meteorite found in the Yamato Mountains of Antarctica. It is classified as a lherzolitic shergottite and petrographically resembles several other lherzolitic shergottites, i.e. ALHA 77005, LEW 88516, Y-793605 and Y-000027/47/97 [e.g. 2-5]. These meteorites have similarly young crystallization ages (152-185 Ma) as enriched basaltic shergottites (157-203 Ma), but have very different ejection ages (approximately 4 Ma vs. approximately 2.5 Ma), thus they came from different martian target crater areas. Lherzolitic shergottites have mg-values approximately 0.70 and represent the most mafic olivine-pyroxene cumulates. Their parental magmas were melts derived probably from the primitive Martian mantle. Here we present Rb-Sr isotopic data for Y-984028 and compare these data with those obtained from other lherzolitic and olivine-phyric basaltic shergottites to better understand the isotopic characteristics of their primitive mantle source regions. Corresponding Sm-Nd analyses for Y-984028 are in progress

Possible Origins of Magmatic and Isotopic Heterogeneity in Zagami.

第3回極域科学シンポジウム/第35回南極隕石シンポジウム 11月29日（木） 国立国語研究所 2階講

The Chemical and Ionization Conditions in Weak Mg II Absorbers

We present an analysis of the chemical and ionization conditions in a sample of 100 weak Mg II absorbers identified in the VLT/UVES archive of quasar spectra. Using a host of low ionization lines associated with each absorber in this sample, and on the basis of ionization models, we infer that the metallicity in a significant fraction of weak Mg II clouds is constrained to values of solar or higher, if they are sub-Lyman limit systems. Based on the observed constraints, we present a physical picture in which weak Mg II absorbers are predominantly tracing two different astrophysical processes/structures. A significant population of weak Mg II clouds, those in which N(Fe II) is much less than N(Mg II), identified at both low (z ~ 1) and high (z ~ 2) redshift, are potentially tracing gas in the extended halos of galaxies, analogous to the Galactic high velocity clouds. These absorbers might correspond to alpha-enhanced interstellar gas expelled from star-forming galaxies, in correlated supernova events. On the other hand, N(FeII) approximately equal to N(Mg II) clouds, which are prevalent only at lower redshifts (z < 1.5), must be tracing Type Ia enriched gas in small, high metallicity pockets in dwarf galaxies, tidal debris, or other intergalactic structures.Comment: 35 pages (including tables & figures). Accepted for publication in ApJ. A high resolution version of the paper is available at "http://www.astro.wisc.edu/~anand/weakMgII.pdf

Leading Temperature Corrections to Fermi Liquid Theory in Two Dimensions

We calculate the basic parameters of the Fermi Liquid: the scattering vertex, the Landau interaction function, the effective mass, and physical susceptibilities for a model of two-dimensional (2D) fermions with a short ranged interaction at non-zero temperature. The leading temperature dependences of the spin components of the scattering vertex, the Landau function, and the spin susceptibility are found to be linear. T-linear terms in the effective mass and in the ``charge-sector''- quantities are found to cancel to second order in the interaction, but the cancellation is argued not to be generic. The connection with previous studies of the 2D Fermi-Liquid parameters is discussed.Comment: 4 pages, 1 figur

New Mechanism for Electronic Energy Relaxation in Nanocrystals

The low-frequency vibrational spectrum of an isolated nanometer-scale solid differs dramatically from that of a bulk crystal, causing the decay of a localized electronic state by phonon emission to be inhibited. We show, however, that an electron can also interact with the rigid translational motion of a nanocrystal. The form of the coupling is dictated by the equivalence principle and is independent of the ordinary electron-phonon interaction. We calculate the rate of nonradiative energy relaxation provided by this mechanism and establish its experimental observability.Comment: 4 pages, Submitted to Physical Review

Rb-Sr, Sm-Nd and Ar-Ar isotopic systematics of Antarctic nakhlite Yamato 000593

sotopic analysis of the newly found Antarctic nakhlite Yamato (Y) 000593 yields a Rb-Sr age of 1.30±0.02Ga with an initial ^(87)Sr/^(86)Sr of 0.702525±0.000027, a Sm-Nd age of 1.31±0.03Ga with an initial ε_(Nd) of + 16.0±0.2 and an Ar-Ar isochron age of <=1.36Ga. The concordancy of these three ages and Rb-Sr and Sm-Nd initial isotopic signatures strongly suggest that Y000593 crystallized from low Rb/Sr, light REE-depleted source materials ～1.31Ga ago. The crystallization age of Y000593 is compared with the age data of non-Antarctic nakhlites (Nakhla, Governador Valadares, Lafayette and Northwest Africa 998) and Chassigny. The initial Sr and Nd isotopic signatures suggest that Lafayette and Y000593 were co-magmatic or at least came from very similar magmas. Cosmogenic ^(36)Ar concentrations in Y000593 resemble those in other nakhlites. The similarities in crystallization and ejection ages and in petrologic features suggest the nakhlites were derived from similar source regions, and launch pairing of nakhlites and Chassigny. The Rb-Sr data for Y000593 show that the isotopic system is disturbed by pre-terrestrial alteration of olivine. Although many of the acid-leached residues of mineral fractions fall along the 1.30Ga Rb-Sr isochron, leached olivine does not. This indicates the lack of isotopic equilibrium between the olivine fractions and the secondary alteration phases. A tie-line between two olivine leachates provides a calculated "age" of 650±80Ma with an initial ^(87)Sr/^(86)Sr of ～0.70465, which gives a hint for the isotopic signatures of local brine as well as the timing of an aqueous alteration event on the Martian surface

Rb-Sr and Sm-Nd dating of olivine-phyric shergottite Yamato 980459: Petrogenesis of depleted shergottites

Martian meteorite Yamato (Y) 980459 has undergone terrestrial weathering in Antarctica. The weathering has affected the Sm-Nd isotopic system. Acid-washed pyroxenes, whole rock and quenched glass samples define a Sm-Nd isochron age of 472±47 (±2σ) Ma and a high initial εNd value of +36.9±2.2 (±2σ). Both values are indisguishable from those reported for the other olivine-phyric depleted shergottite DaG 476. The Rb-Sr system of Y980459 shows even more terrestrial disturbance. The same acid-washed samples, which have a narrow Rb/Sr variation of only～10%, do not yield an Rb-Sr isochron. However, the weighted average of nine samples yields a good initial ^(87)Sr/^(86)Sr ratio value of 0.701384±0.000021 (±2σ) at 472Ma. This value is only slightly higher, by 1-2 ε-units, than that estimated from plagioclase data for DaG 476. Calculations for a two-stage model for Sr and Nd isotopic evolution indicate that Y980459 came from a depleted mantle reservoir with ^(147)Sm/^(144)Nd=～0.266 and ^(87)Rb/^(86)Sr=～0.04, similar to the DaG 476 source. A three-stage model calculation suggests that the REE abundances and Nd isotopic systematics of Y980459 could be produced by partial melting of high ^(147)Sm/^(144)Nd garnet-rich residues which were formed after the extraction of LREE-rich, nakhlite-like melts from a postulated garnet-clinopyroxene-olivine source having ^(147)Sm/^(144)Nd=～0.235

39Ar - 40Ar Studies of Lherzolitic Shergottites Yamato 000097 and 984028

Yamato 984028 (Y984028) was discovered by the Japanese Antarctic Research Expedition (JARE) in 1998 and recently classified as a lherzolitic shergottite with large pyroxene oikocrysts enclosing rounded olivine and chromites. It also contains shock veining and maskelynite. Y984028 is paired with the more recent lherzolitic shergottite finds Y000027/47/97 based on similarities in mineralogy and chemistry, as well as isotopic composition. We present here the studied Ar-39-Ar-40 of Y-984028 whole rock (WR) and pyroxene (Px), in order to gain better understanding of trapped Ar components with a comparison of the possibly-paired Y000097 Ar release

Drude Weight of the Two-Dimensional Hubbard Model -- Reexamination of Finite-Size Effect in Exact Diagonalization Study --

The Drude weight of the Hubbard model on the two-dimensional square lattice is studied by the exact diagonalizations applied to clusters up to 20 sites. We carefully examine finite-size effects by consideration of the appropriate shapes of clusters and the appropriate boundary condition beyond the imitation of employing only the simple periodic boundary condition. We successfully capture the behavior of the Drude weight that is proportional to the squared hole doping concentration. Our present result gives a consistent understanding of the transition between the Mott insulator and doped metals. We also find, in the frequency dependence of the optical conductivity, that the mid-gap incoherent part emerges more quickly than the coherent part and rather insensitive to the doping concentration in accordance with the scaling of the Drude weight.Comment: 9 pages with 10 figures and 1 table. accepted in J. Phys. Soc. Jp

Perturbations of Noise: The origins of Isothermal Flows

We make a detailed analysis of both phenomenological and analytic background for the "Brownian recoil principle" hypothesis (Phys. Rev. A 46, (1992), 4634). A corresponding theory of the isothermal Brownian motion of particle ensembles (Smoluchowski diffusion process approximation), gives account of the environmental recoil effects due to locally induced tiny heat flows. By means of local expectation values we elevate the individually negligible phenomena to a non-negligible (accumulated) recoil effect on the ensemble average. The main technical input is a consequent exploitation of the Hamilton-Jacobi equation as a natural substitute for the local momentum conservation law. Together with the continuity equation (alternatively, Fokker-Planck), it forms a closed system of partial differential equations which uniquely determines an associated Markovian diffusion process. The third Newton law in the mean is utilised to generate diffusion-type processes which are either anomalous (enhanced), or generically non-dispersive.Comment: Latex fil