373 research outputs found
Vacuum type of SU(2) gluodynamics in maximally Abelian and Landau gauges
The vacuum type of SU(2) gluodynamics is studied using Monte-Carlo
simulations in maximally Abelian (MA) gauge and in Landau (LA) gauge, where the
dual Meissner effect is observed to work. The dual Meissner effect is
characterized by the coherence and the penetration lengths. Correlations
between Wilson loops and electric fields are evaluated in order to measure the
penetration length in both gauges. The coherence length is shown to be fixed in
the MA gauge from measurements of the monopole density around the static
quark-antiquark pair. It is also shown numerically that a dimension 2 gluon
operator A^+A^-(s) and the monopole density has a strong correlation as
suggested theoretically. Such a correlation is observed also between the
monopole density and A^2(s)= A^+A^-(s) + A^3A^3(s) condensate if the remaining
U(1) gauge degree of freedom is fixed to U(1) Landau gauge (U1LA). The
coherence length is determined numerically also from correlations between
Wilson loops and A^+A^-(s) and A^2(s) in MA + U1LA gauge. Assuming that the
same physics works in the LA gauge, we determine the coherence length from
correlations between Wilson loops and A^2(s). Penetration lengths and coherence
lengths in the two gauges are almost the same. The vacuum type of the
confinement phase in both gauges is near to the border between the type 1 and
the type 2 dual superconductors.Comment: 13 pages, 22 figures, RevTeX 4 styl
Identification and Characterization of a Novel Polysaccharide Deacetylase C (PdaC) from Bacillus subtilis
Cell wall metabolism and cell wall modification are very important processes that bacteria use to adjust to various environmental conditions. One of the main modifications is deacetylation of peptidoglycan. The polysaccharide deacetylase homologue, Bacillus subtilis YjeA (renamed PdaC), was characterized and found to be a unique deacetylase. The pdaC deletion mutant was sensitive to lysozyme treatment, indicating that PdaC acts as a deacetylase. The purified recombinant and truncated PdaC from Escherichia coli deacetylated B. subtilis peptidoglycan and its polymer, (-GlcNAc-MurNAc[-L-Ala-D-Glu]-)(n). Surprisingly, RP-HPLC and ESI-MS/MS analyses showed that the enzyme deacetylates N-acetylmuramic acid (MurNAc) not GlcNAc from the polymer. Contrary to Streptococcus pneumoniae PgdA, which shows high amino acid sequence similarity with PdaC and is a zinc-dependent GlcNAc deacetylase toward peptidoglycan, there was less dependence on zinc ion for deacetylation of peptidoglycan by PdaC than other metal ions (Mn2+, Mg2+, Ca2+). The kinetic values of the activity toward B. subtilis peptidoglycan were K-m = 4.8 mM and k(cat) = 0.32 s(-1). PdaC also deacetylated N-acetylglucosamine (GlcNAc) oligomers with a K-m = 12.3 mM and k(cat) = 0.24 s(-1) toward GlcNAc(4). Therefore, PdaC has GlcNAc deacetylase activity toward GlcNAc oligomers and MurNAc deacetylase activity toward B. subtilis peptidoglycan.ArticleJOURNAL OF BIOLOGICAL CHEMISTRY. 287(13):9765-9776 (2012)journal articl
Three DNA polymerases, recruited by different mechanisms, carry out NER repair synthesis in human cells
Nucleotide excision repair (NER) is the most versatile DNA repair system that deals with the major UV photoproducts in DNA, as well as many other DNA adducts. The early steps of NER are well understood, whereas the later steps of repair synthesis and ligation are not. In particular, which polymerases are definitely involved in repair synthesis and how they are recruited to the damaged sites has not yet been established. We report that, in human fibroblasts, approximately half of the repair synthesis requires both polκ and polδ, and both polymerases can be recovered in the same repair complexes. Polκ is recruited to repair sites by ubiquitinated PCNA and XRCC1 and polδ by the classical replication factor complex RFC1-RFC, together with a polymerase accessory factor, p66, and unmodified PCNA. The remaining repair synthesis is dependent on polɛ, recruitment of which is dependent on the alternative clamp loader CTF18-RFC
Correlation between intercalated magnetic layers and superconductivity in pressurized EuFe2(As0.81P0.19)2
We report comprehensive high pressure studies on correlation between
intercalated magnetic layers and superconductivity in EuFe2(As0.81P0.19)2
single crystal through in-situ high pressure resistance, specific heat, X-ray
diffraction and X-ray absorption measurements. We find that an unconfirmed
magnetic order of the intercalated layers coexists with superconductivity in a
narrow pressure range 0-0.5GPa, and then it converts to a ferromagnetic (FM)
order at pressure above 0.5 GPa, where its superconductivity is absent. The
obtained temperature-pressure phase diagram clearly demonstrates that the
unconfirmed magnetic order can emerge from the superconducting state. In stark
contrast, the superconductivity cannot develop from the FM state that is
evolved from the unconfirmed magnetic state. High pressure X-ray absorption
(XAS) measurements reveal that the pressure-induced enhancement of Eu's mean
valence plays an important role in suppressing the superconductivity and tuning
the transition from the unconfirmed magnetic state to a FM state. The unusual
interplay among valence state of Eu ions, magnetism and superconductivity under
pressure may shed new light on understanding the role of the intercalated
magnetic layers in Fe-based superconductors
Semi-Static Hedging Based on a Generalized Reflection Principle on a Multi Dimensional Brownian Motion
On a multi-assets Black-Scholes economy, we introduce a class of barrier
options. In this model we apply a generalized reflection principle in a context
of the finite reflection group acting on a Euclidean space to give a valuation
formula and the semi-static hedge.Comment: Asia-Pacific Financial Markets, online firs
Experimental and theoretical evidence for pressure-induced metallization in FeO with the rock-salt type structure
Electrical conductivity of FeO was measured up to 141 GPa and 2480 K in a
laserheated diamond-anvil cell. The results show that rock-salt (B1) type
structured FeO metallizes at around 70 GPa and 1900 K without any structural
phase transition. We computed fully self-consistently the electronic structure
and the electrical conductivity of B1 FeO as a function of pressure and
temperature, and found that although insulating as expected at ambient
condition, B1 FeO metallizes at high temperatures, consistent with experiments.
The observed metallization is related to spin crossover
A list of all integrable 2D homogeneous polynomial potentials with a polynomial integral of order at most 4 in the momenta
We searched integrable 2D homogeneous polynomial potential with a polynomial
first integral by using the so-called direct method of searching for first
integrals. We proved that there exist no polynomial first integrals which are
genuinely cubic or quartic in the momenta if the degree of homogeneous
polynomial potentials is greater than 4.Comment: 22 pages, no figures, to appear in J. Phys. A: Math. Ge
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