549 research outputs found
Lead-oxygen closed-loop battery system
Calculations show that battery can deliver up to 35 watt-hours per pound, conventional lead-acid batteries deliver 10 to 15 watt-hours per pound. Weight reduction is due to replacement of solid lead-peroxide electrodes with metal current-collector screen, catalyst, and Teflon membrane
Crystal field states of Kondo lattice heavy fermions CeRuSn3 and CeRhSn3
Inelastic neutron scattering experiments have been carried out to determine
the crystal field states of the Kondo lattice heavy fermions CeRuSn3 and
CeRhSn3. Both the compounds crystallize in LaRuSn3-type cubic structure (space
group Pm-3n) in which the Ce atoms occupy two distinct crystallographic sites
with cubic (m-3) and tetragonal (-4m.2) point symmetries. The INS data of
CeRuSn3 reveal the presence of a broad excitation centered around 6-8 meV which
is accounted by a model based on crystal electric field (CEF) excitations. On
the other hand, the INS data of isostructural CeRhSn3 reveal three CEF
excitations around 7.0, 12.2 and 37.2 meV. The neutron intensity sum rule
indicates that the Ce ions at both cubic and tetragonal Ce sites are in Ce3+
state in both CeRuSn3 and CeRhSn3. The CEF level schemes for both the compounds
are deduced. We estimate the Kondo temperature T_K = 3.1(2) K for CeRuSn3 from
neutron quasielastic linewidth in excellent agreement with that determined from
the scaling of magnetoresistance which gives T_K = 3.2(1) K. For CeRhSn3 the
neutron quasielastic linewidth gives T_K = 4.6 K. For both CeRuSn3 and CeRhSn3,
the ground state of Ce3+ turns out to be a quartet for the cubic site and a
doublet for the tetragonal site.Comment: 12 pages, 13 figures, 2 tables, to appear in Phys. Rev.
Resolution of Acute Hydrocephalus and Migration of Neurocysticercosis Cyst with External Ventricular Drainage
Neurocysticercosis is endemic in the developing world, but is becoming more common in the US due to immigration. A 24-year-old man presented with acute hydrocephalus and headaches, nausea, and vomiting. Head CT revealed a 3rd ventricular cyst and immunological studies were suggestive of neurocysticercosis. EVD placement resulted in migration of the cyst interiorly and superiorly with return of normal CSF flow by MRI and resolution of symptoms. Review of this condition is important given increasing incidence in the United States
On Binary Matroid Minors and Applications to Data Storage over Small Fields
Locally repairable codes for distributed storage systems have gained a lot of
interest recently, and various constructions can be found in the literature.
However, most of the constructions result in either large field sizes and hence
too high computational complexity for practical implementation, or in low rates
translating into waste of the available storage space. In this paper we address
this issue by developing theory towards code existence and design over a given
field. This is done via exploiting recently established connections between
linear locally repairable codes and matroids, and using matroid-theoretic
characterisations of linearity over small fields. In particular, nonexistence
can be shown by finding certain forbidden uniform minors within the lattice of
cyclic flats. It is shown that the lattice of cyclic flats of binary matroids
have additional structure that significantly restricts the possible locality
properties of -linear storage codes. Moreover, a collection of
criteria for detecting uniform minors from the lattice of cyclic flats of a
given matroid is given, which is interesting in its own right.Comment: 14 pages, 2 figure
Hamming weights and Betti numbers of Stanley-Reisner rings associated to matroids
To each linear code over a finite field we associate the matroid of its
parity check matrix. We show to what extent one can determine the generalized
Hamming weights of the code (or defined for a matroid in general) from various
sets of Betti numbers of Stanley-Reisner rings of simplicial complexes
associated to the matroid
On character generators for simple Lie algebras
We study character generating functions (character generators) of simple Lie
algebras. The expression due to Patera and Sharp, derived from the Weyl
character formula, is first reviewed. A new general formula is then found. It
makes clear the distinct roles of ``outside'' and ``inside'' elements of the
integrity basis, and helps determine their quadratic incompatibilities. We
review, analyze and extend the results obtained by Gaskell using the Demazure
character formulas. We find that the fundamental generalized-poset graphs
underlying the character generators can be deduced from such calculations.
These graphs, introduced by Baclawski and Towber, can be simplified for the
purposes of constructing the character generator. The generating functions can
be written easily using the simplified versions, and associated Demazure
expressions. The rank-two algebras are treated in detail, but we believe our
results are indicative of those for general simple Lie algebras.Comment: 50 pages, 11 figure
Calculated corrections to superallowed Fermi beta decay: New evaluation of the nuclear-structure-dependent terms
The measured -values for superallowed nuclear
-decay can be used to obtain the value of the vector coupling constant
and thus to test the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. An
essential requirement for this test is accurate calculations for the radiative
and isospin symmetry-breaking corrections that must be applied to the
experimental data. We present a new and consistent set of calculations for the
nuclear-structure-dependent components of these corrections. These new results
do not alter the current status of the unitarity test -- it still fails by more
than two standard deviations -- but they provide calculated corrections for
eleven new superallowed transitions that are likely to become accessible to
precise measurements in the future. The reliability of all calculated
corrections is explored and an experimental method indicated by which the
structure-dependent corrections can be tested and, if necessary, improved.Comment: Revtex4, one figur
Towards a fullerene-based quantum computer
Molecular structures appear to be natural candidates for a quantum
technology: individual atoms can support quantum superpositions for long
periods, and such atoms can in principle be embedded in a permanent molecular
scaffolding to form an array. This would be true nanotechnology, with
dimensions of order of a nanometre. However, the challenges of realising such a
vision are immense. One must identify a suitable elementary unit and
demonstrate its merits for qubit storage and manipulation, including input /
output. These units must then be formed into large arrays corresponding to an
functional quantum architecture, including a mechanism for gate operations.
Here we report our efforts, both experimental and theoretical, to create such a
technology based on endohedral fullerenes or 'buckyballs'. We describe our
successes with respect to these criteria, along with the obstacles we are
currently facing and the questions that remain to be addressed.Comment: 20 pages, 13 figs, single column forma
Fibrinogen Chains Intrinsic to the Brain
We observed fine fibrin deposition along the paravascular spaces in naive animals, which increased dramatically following subarachnoid hemorrhage (SAH). Following SAH, fibrin deposits in the areas remote from the hemorrhage. Traditionally it is thought that fibrinogen enters subarachnoid space through damaged blood brain barrier. However, deposition of fibrin remotely from hemorrhage suggests that fibrinogen chains Aα, Bβ, and γ can originate in the brain. Here we demonstrate in vivo and in vitro that astroglia and neurons are capable of expression of fibrinogen chains. SAH in mice was induced by the filament perforation of the circle of Willis. Four days after SAH animals were anesthetized, transcardially perfused and fixed. Whole brain was processed for immunofluorescent (IF) analysis of fibrin deposition on the brain surface or in brains slices processed for fibrinogen chains Aα, Bβ, γ immunohistochemical detection. Normal human astrocytes were grown media to confluency and stimulated with NOC-18 (100 μM), TNF-α (100 nM), ATP-γ-S (100 μM) for 24 h. Culture was fixed and washed/permeabilized with 0.1% Triton and processed for IF. Four days following SAH fibrinogen chains Aα IF associated with glia limitans and superficial brain layers increased 3.2 and 2.5 times (p < 0.05 and p < 0.01) on the ventral and dorsal brain surfaces respectively; fibrinogen chains Bβ increased by 3 times (p < 0.01) on the dorsal surface and fibrinogen chain γ increased by 3 times (p < 0.01) on the ventral surface compared to sham animals. Human cultured astrocytes and neurons constitutively expressed all three fibrinogen chains. Their expression changed differentially when exposed for 24 h to biologically significant stimuli: TNFα, NO or ATP. Western blot and RT-qPCR confirmed presence of the products of the appropriate molecular weight and respective mRNA. We demonstrate for the first time that mouse and human astrocytes and neurons express fibrinogen chains suggesting potential presence of endogenous to the brain fibrinogen chains differentially changing to biologically significant stimuli. SAH is followed by increased expression of fibrinogen chains associated with glia limitans remote from the hemorrhage. We conclude that brain astrocytes and neurons are capable of production of fibrinogen chains, which may be involved in various normal and pathological processes
Linking global CGE models with sectoral models to generate baseline scenarios: Approaches, opportunities and pitfalls
When modelling medium and long-term challenges we need a reference path of economic development (the so-called baseline). Because sectoral models often offer a more fundamental understanding of future developments for specific sectors, many CGE modeling teams have adopted different kinds of linking approaches to sectoral models to generate baselines. We systematically compare and discuss approaches of linking CGE models for the baseline calibration procedure, and discuss best practices and pitfalls. We identify different types of linking approaches which we divide into a) links with partial equilibrium models, and b) links with non-economic models. These two types of linking approaches are then analyzed with respect to e.g. the degree of linkage, information exchanged, as well as compromises in aggregations and definitions. Based on this, we discuss potential drawbacks and conclude with suggestions for best practices and research recommendations
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