196 research outputs found
Fractional Strings in (p,q) 5-brane and Quiver Matrix String Theory
We study the (p,q)5-brane dynamics from the viewpoint of Matrix string theory
in the T-dualized ALE background. The most remarkable feature in the
(p,q)5-brane is the existence of ``fractional string'', which appears as the
instanton of 5-brane gauge theory. We approach to the physical aspects of
fractional string by means of the two types of Matrix string probes: One of
which is that given in hep-th/9710065. As the second probe we present the
Matrix string theory describing the fractional string itself. We calculate the
moduli space metrics in the respective cases and argue on the specific
behaviors of fractional string. Especially, we show that the ``joining''
process of fractional strings can be realized as the transition from the
Coulomb branch to the Higgs branch of the fractional string probe. In this
argument, we emphasize the importance of some monodromies related with the
theta-angle of the 5-brane gauge theory.Comment: 21 pages, Late
First principles calculations of defect clustering in acceptor-doped BaZrO3
Acceptor-doped BaZrO3 shows high proton conductivity under wet atmosphere conditions and is a promising material used for a proton conductive electrolyte. Similar to other kinds of ionic conductors, however, carrier trapping by dopant occurs and suppresses conductivity of the acceptor-doped BaZrO3 [1]. The carrier trapping is an unavoidable phenomenon for ionic conductors because formation of charge carriers for ionic conduction is attributed to dopants with opposite charge states to the carriers. We have to understand and to control the carrier trapping behavior to optimize properties of ionic conductors.
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Efficacy and tolerability of topiramate-augmentation therapy for schizophrenia: a systematic review and meta-analysis of randomized controlled trials
Butterfly Tachyons in Vacuum String Field Theory
We use geometrical conformal field theory methods to investigate tachyon
fluctuations about the butterfly projector state in Vacuum String Field Theory.
We find that the on-shell condition for the tachyon field is equivalent to the
requirement that the quadratic term in the string-field action vanish on shell.
This further motivates the interpretation of the butterfly state as a D-brane.
We begin a calculation of the tension of the butterfly, and conjecture that
this will match the case of the sliver and further strengthen this
interpretation.Comment: 14 pages, 6 figures, revte
Oxygen affinity: the missing link enabling prediction of proton conductivities in doped barium zirconates
Proton-conducting oxides, specifically doped barium zirconates, have garnered much attention as electrolytes for solid-state electrochemical devices operable at intermediate temperatures (400–600 °C). In chemical terms, hydration energy, E_(hyd), and proton–dopant association energy, E_(as), are two key parameters that determine whether an oxide exhibits fast proton conduction, but to date ab initio studies have for the most part studied each parameter separately, with no clear correlation with proton conductivity identified in either case. Here, we demonstrate that the oxygen affinity, E_(O.dopant), defined as the energy released when an oxide ion enters an oxygen vacancy close to a dopant atom, is the missing link between these two parameters and correlates well with experimental proton conductivities in doped barium zirconates. Ab initio calculations of point defects and their complexes in Sc-, In-, Lu-, Er-, Y-, Gd-, and Eu-doped barium zirconates are used to determine E_(hyd), E_(as), E_(O.dopant), and the hydrogen affinity, EH.host, of each system. These four energy terms are related by E_(hyd) = E_(O.dopant) + 2E_(H.host) + 2E_(as). Complementary impedance spectroscopy measurements reveal that the stronger the calculated oxygen affinity of a system, the higher the proton conductivity at 350 °C. Although the proton trapping site is also an important factor, the results show that oxygen affinity is an excellent predictor of proton conductivity in these materials
Oxygen affinity: the missing link enabling prediction of proton conductivities in doped barium zirconates
Proton-conducting oxides, specifically doped barium zirconates, have garnered much attention as electrolytes for solid-state electrochemical devices operable at intermediate temperatures (400–600 °C). In chemical terms, hydration energy, E_(hyd), and proton–dopant association energy, E_(as), are two key parameters that determine whether an oxide exhibits fast proton conduction, but to date ab initio studies have for the most part studied each parameter separately, with no clear correlation with proton conductivity identified in either case. Here, we demonstrate that the oxygen affinity, E_(O.dopant), defined as the energy released when an oxide ion enters an oxygen vacancy close to a dopant atom, is the missing link between these two parameters and correlates well with experimental proton conductivities in doped barium zirconates. Ab initio calculations of point defects and their complexes in Sc-, In-, Lu-, Er-, Y-, Gd-, and Eu-doped barium zirconates are used to determine E_(hyd), E_(as), E_(O.dopant), and the hydrogen affinity, EH.host, of each system. These four energy terms are related by E_(hyd) = E_(O.dopant) + 2E_(H.host) + 2E_(as). Complementary impedance spectroscopy measurements reveal that the stronger the calculated oxygen affinity of a system, the higher the proton conductivity at 350 °C. Although the proton trapping site is also an important factor, the results show that oxygen affinity is an excellent predictor of proton conductivity in these materials
Proton trapping in yttrium-doped barium zirconate
The environmental benefits of fuel cells have been increasingly appreciated in recent years. Among candidate electrolytes for solid-oxide fuel cells, yttrium-doped barium zirconate has garnered attention because of its high proton conductivity, particularly in the intermediate-temperature region targeted for cost-effective solid-oxide fuel cell operation, and its excellent chemical stability. However, fundamental questions surrounding the defect chemistry and macroscopic proton transport mechanism of this material remain, especially in regard to the possible role of proton trapping. Here we show, through a combined thermogravimetric and a.c. impedance study, that macroscopic proton transport in yttrium-doped barium zirconate is limited by proton–dopant association (proton trapping). Protons must overcome the association energy, 29 kJ mol^(−1), as well as the general activation energy, 16 kJ mol^(−1), to achieve long-range transport. Proton nuclear magnetic resonance studies show the presence of two types of proton environment above room temperature, reflecting differences in proton–dopant configurations. This insight motivates efforts to identify suitable alternative dopants with reduced association energies as a route to higher conductivities
Constraints on effective Lagrangian of D-branes from non-commutative gauge theory
It was argued that there are two different descriptions of the effective
Lagrangian of gauge fields on D-branes by non-commutative gauge theory and by
ordinary gauge theory in the presence of a constant B field background. In the
case of bosonic string theory, however, it was found in the previous works that
the two descriptions are incompatible under the field redefinition which
relates the non-commutative gauge field to the ordinary one found by Seiberg
and Witten. In this paper we resolve this puzzle to observe the necessity of
gauge-invariant but B-dependent correction terms involving metric in the field
redefinition which have not been considered before. With the problem resolved,
we establish a systematic method under the alpha' expansion to derive the
constraints on the effective Lagrangian imposed by the compatibility of the two
descriptions where the form of the field redefinition is not assumed.Comment: 39 pages, LaTeX2e, no figures; v2: Appendix B corrected, minor
changes; v3: Abstract, Introduction and Section 5 revised to emphasize our
new results, minor changes, references updated, version to be published in
Nucl. Phys.
Transient and permanent gene transfer into the brain of the teleost fish medaka (Oryzias latipes) using human adenovirus and the Cre-loxP system
AbstractIn this study, we demonstrated that human type-5 adenovirus infected the brain of the teleost fish, medaka (Oryzias latipes), in vivo. Injection of adenoviral vector into the mesencephalic ventricle of medaka larvae induced the expression of reporter genes in some parts of the telencephalon, the periventricular area of the mesencephalon and diencephalon, and the cerebellum. Additionally, the Cre-loxP system works in medaka brains using transgenic medaka carrying a vector containing DsRed2, flanked by loxP sites under control of the β-actin promoter and downstream promoterless enhanced green fluorescent protein (EGFP). We demonstrated that the presence of green fluorescence depended on injection of adenoviral vector expressing the Cre gene and confirmed that EGFP mRNA was transcribed in the virus-injected larvae
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