5,308 research outputs found
Chalcophile Element Constraints on the Sulfur Content of the Martian Mantle
The sulfur content of the Martian mantle is critical to understanding volcanic volatiles supplied to the surface of Mars and possibly climate. In the absence of Martian mantle rocks, sulfur content of the mantle has been inferred from S contents of Martian meteorites or from sedimentary sulfate abundances. Estimates of the sulfur content of the Martian mantle vary from 390-2,000 ppm, all of which are higher than that of the terrestrial mantle (~250 ppm;). Residual sulfide in the Martian mantle controls the distribution of chalcophile elements during partial melting. In this study, we report new analyses of Martian meteorites, and use the incompatible behavior of As, Tl and Pb to infer the sulfide mode of the Martian mantle using a different set of assumptions than those of prior studies
Tin Abundances Require that Chassignites Originated from Multiple Magmatic Bodies Distinct from Nakhlites
Meteorites from Mars lack field context but chemical and chronologic studies have revealed remarkable links between nakhlites and chassignites. A widely held consensus is that nakhlites and chassignites originated from a large, single differentiated flow or shallow intrusive [1-5]. An Ar-Ar study assumed multiple flows based on resolvable age differences between meteorites [6], but did not address the possibility of differential cooling in a large, shallowly emplaced intrusion [1]. REE abundances in pyroxenes from nakhlites and Chassigny led [7] to argue for derivation of these rocks from distinct magmas. Volatile abundances (F, Cl, OH) in chlorapatites indicated that the entire suite of nakhlites and chassignites experienced hydrothermal interaction with a single fluid supporting a single body origin [4]. The discovery of a new chassignite, NWA 8694, extended the Mg# range from 80-54, providing a closer link to nakhlites but revealed the petrological difficulty of fractionating a single body of liquid to yield a series of olivine cumulates with such a large Mg# range [8]. When mafic magmas are emplaced into the crust, crustal assimilation can impart distinct elemental signatures if the country rock has experienced sedimentary or hydrothermal processing [9]. In this work, we used Sn abundances of nakhlites and chassignites to show that these rocks were crystallized from distinct magma batches, providing vital contextual clues to their origin
A determination of the strange quark mass for unquenched clover fermions using the AWI
Using the O(a) Symanzik improved action an estimate is given for the strange
quark mass for unquenched (nf=2) QCD. The determination is via the axial Ward
identity (AWI) and includes a non-perturbative evaluation of the
renormalisation constant. Numerical results have been obtained at several
lattice spacings, enabling the continuum limit to be taken. Results indicate a
value for the strange quark mass (in the MSbar-scheme at a scale of 2GeV) in
the range 100 - 130MeV.Comment: 6 pages, contribution to Lattice2005(Hadron spectrum and quark
masses), uses PoS.cl
A Determination of the Lambda Parameter from Full Lattice QCD
We present a determination of the QCD parameter Lambda in the quenched
approximation (n_f=0) and for two flavours (n_f=2) of light dynamical quarks.
The calculations are performed on the lattice using O(a) improved Wilson
fermions and include taking the continuum limit. We find Lambda_{n_f=0} =
259(1)(20) MeV and Lambda_{n_f=2} = 261(17)(26) MeV}, using r_0 = 0.467 fm to
set the scale. Extrapolating our results to five flavours, we obtain for the
running coupling constant at the mass of the Z boson alpha_s(m_Z) =
0.112(1)(2). All numbers refer to the MSbar scheme.Comment: 25 pages, 9 figure
Moir\'e patterns in quantum images
We observed moir\'e fringes in spatial quantum correlations between twin
photons generated by parametric down-conversion. Spatially periodic structures
were nonlocally superposed giving rise to beat frequencies typical of moir\'e
patterns. This result brings interesting perspectives regarding metrological
applications of such a quantum optical setup.Comment: 4 pages, 5 figure
Determination of Lambda in quenched and full QCD - an update
We present an update on our previous determination of the Lambda parameter in
QCD. The main emphasis is on results for two flavours of light dynamical
quarks, where we can now almost double the amount of data used, including
values at smaller lattice spacings. The calculations are performed using
improved Wilson fermions. Little change is found to previous numerical values.Comment: Lattice2004(spectrum), Fermilab, June 21-26, 2004, 3 page
Manipulation Strategies for the Rank Maximal Matching Problem
We consider manipulation strategies for the rank-maximal matching problem. In
the rank-maximal matching problem we are given a bipartite graph such that denotes a set of applicants and a set of posts. Each
applicant has a preference list over the set of his neighbours in
, possibly involving ties. Preference lists are represented by ranks on the
edges - an edge has rank , denoted as , if post
belongs to one of 's -th choices. A rank-maximal matching is one in which
the maximum number of applicants is matched to their rank one posts and subject
to this condition, the maximum number of applicants is matched to their rank
two posts, and so on. A rank-maximal matching can be computed in time, where denotes the number of applicants, the
number of edges and the maximum rank of an edge in an optimal solution.
A central authority matches applicants to posts. It does so using one of the
rank-maximal matchings. Since there may be more than one rank- maximal matching
of , we assume that the central authority chooses any one of them randomly.
Let be a manipulative applicant, who knows the preference lists of all
the other applicants and wants to falsify his preference list so that he has a
chance of getting better posts than if he were truthful. In the first problem
addressed in this paper the manipulative applicant wants to ensure that
he is never matched to any post worse than the most preferred among those of
rank greater than one and obtainable when he is truthful. In the second problem
the manipulator wants to construct such a preference list that the worst post
he can become matched to by the central authority is best possible or in other
words, wants to minimize the maximal rank of a post he can become matched
to
International Lattice Data Grid
We propose the co-ordination of lattice QCD grid developments in different
countries to allow transparent exchange of gauge configurations in future,
should participants wish to do so. We describe briefly UKQCD's XML schema for
labelling and cataloguing the data. A meeting to further develop these ideas
will be held in Edinburgh on 19/20 December 2002, and will be available over
AccessGrid.Comment: Lattice2002(plenary
Calculation of Finite Size Effects on the Nucleon Mass in Unquenched QCD using Chiral Perturbation Theory
The finite size effects on nucleon masses are calculated in relativistic
chiral perturbation theory. Results are compared with two-flavor lattice
results.Comment: talk at Confinement03, 5 pages latex, 3 figures. Assignment of 2 data
points to incorrect data sets in plot 1 and of 1 data point in plot 2
corrected. 1 fm lattice result updated. Conclusions unchange
- …