214 research outputs found
Pairing collectivity in medium-mass neutron-rich nuclei near drip-line
We look for collective excitations originating from the strong surface
pairing in unstable nuclei near the neutron drip-line. The soft dipole
excitation is such a pairing mode as it exhibits a character of
core-vs-dineutron motion. Possibility of the hydrodynamic phonon mode (the
Anderson-Bogoliubov mode) is also discussed.Comment: 9 pages, a talk presented at Collective Motion in Nuclei under
Extreme Conditions (COMEX2), June 20-23, 2006, St. Goar, German
A novel S-sulfhydrated human serum albumin preparation suppresses melanin synthesis
Products of ultraviolet (UV) irradiation such as reactive oxygen species (ROS) and nitric oxide (NO) stimulate melanin synthesis. Reactive sulfur species (RSS) have been shown to have strong ROS and NO scavenging effects. However, the instability and low retention of RSS limit their use as inhibitors of melanin synthesis. The free thiol at Cys34 on human serum albumin (HSA) is highly stable, has a long retention and possess a high reactivity for RSS. We report herein on the developm ent of an HSA based RSS delivery system. Sulfane sulfur derivatives released from sodium polysulfides (Na 2 S n ) react readily with HSA. An assay for estimating the elimination of sulfide from polysulfide showed that almost all of the sulfur released from Na 2 S n bound to HSA. The Na 2 S n -treated HSA was found to efficiently scavenge ROS and NO produced from chemical reagents. The Na 2 S n -treated HSA was also found to inhibit melanin synthesis in B16 melanoma cells and this inhibition was independent of the number of added sulfur atoms. In B16 melanoma cells, the Na 2 S n -treated HSA also inhibited the levels of ROS and NO induced by UV radiation. Finally, the Na 2 S n -treated HSA inhibited melanin synthesis from L-DOPA and mushroom tyrosinase and suppressed the extent of aggregation of melanin pigments. These data suggest that Na 2 S n -treated HSA inhibits tyrosinase activity for melanin synthesis via two pathways; by directly inhibiting ROS signaling and by scavenging NO. These findings indicate that Na 2 S n -treated HSA has potential to be an attractive and effective candidate for use as a skin whitening agent
A toy model of open membrane field theory in constant 3-form flux
Based on an explicit computation of the scattering amplitude of four open
membranes in a constant 3-form background, we construct a toy model of the
field theory for open membranes in the large C field limit. It is a
generalization of the noncommutative field theories which describe open strings
in a constant 2-form flux. The noncommutativity due to the B-field background
is now replaced by a nonassociative triplet product. The triplet product
satisfies the consistency conditions of lattice 3d gravity, which is inherent
in the world-volume theory of open membranes. We show the UV/IR mixing of the
toy model by computing some Feynman diagrams. Inclusion of the internal degree
of freedom is also possible through the idea of the cubic matrix.Comment: 31 pages, latex, 2 eps figure
Pairing competition in a quasi-one-dimensional model of organic superconductors (TMTSF) in magnetic field
We microscopically study the effect of the magnetic field (Zeeman splitting)
on the superconducting state in a model for quasi-one-dimensional organic
superconductors (TMTSF). We investigate the competition between spin
singlet and spin triplet pairings and the
Fulde-Ferrell-Larkin-Ovchinnikov(FFLO) state by random phase approximation.
While we studied the competition by comparison with the eigenvalue of the gap
equation at a fixed temperature in our previous study (Phys. Rev. Lett.
\textbf{102} (2009) 016403), here we obtain both the for each pairing
state and a phase diagram in the (temperature)-(field)-(strength
of the charge fluctuation) space. The phase diagram shows that consecutive
transitions from singlet pairing to the FFLO state and further to
triplet pairing can occur upon increasing the magnetic field when
charge fluctuations coexist with spin fluctuations. In the FFLO state,
the singlet d-wave and triplet -wave components are strongly mixed
especially when the charge fluctuations are strong.Comment: 11 pages, 9 figure
Fulde-Ferrell-Larkin-Ovchinnikov State in Heavy Fermion Superconductors
The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is a novel superconducting
state in a strong magnetic field characterized by the formation of Cooper pairs
with nonzero total momentum (k \uparrow, -k+q \downarrow), instead of the
ordinary BCS pairs (k \uparrow, -k \downarrow). A fascinating aspect of the
FFLO state is that it exhibits inhomogeneous superconducting phases with a
spatially oscillating order parameter and spin polarization. The FFLO state has
been of interest in various research fields, not only in superconductors in
solid state physics, but also in neutral Fermion superfluid of ultracold atomic
gases and in color superconductivity in high energy physics. In spite of
extensive studies of various superconductors, there has been no undisputed
experimental verification of the FFLO state, mainly because of the very
stringent conditions required of the superconducting materials. Among several
classes of materials, certain heavy fermion and organic superconductors are
believed to provide conditions that are favorable to the formation of the FFLO
state. This review presents recent experimental and theoretical developments of
the FFLO state mainly in heavy fermion superconductors. In particular we
address the recently discovered quasi-two-dimensional superconductor CeCoIn_5,
which is a strong candidate for the formation of the FFLO state.Comment: 17 pages, 12 figures with jpsf2.cls, to be published in J. Phys. Soc.
Jpn. (Special Topics - Frontiers of Novel Superconductivity in Heavy Fermion
Compounds
Analysis of the anti-tumor effect of cetuximab using protein kinetics and mouse xenograft models
<p>Abstract</p> <p>Background</p> <p>The binding of EGFR and its ligands leads to autophosphorylation of receptor tyrosine kinase as well as subsequent activation of signal transduction pathways that are involved in regulating cellular proliferation, differentiation, and survival. An EGFR inhibitor, cetuximab binds to EGFR and consequently blocks a variety of cellular processes. <it>KRAS</it>/<it>BRAF </it>mutations are known to be associated with a low response rate to cetuximab. In the present study, to clarify the anti-tumor mechanisms of cetuximab, we evaluated the <it>KRAS</it>/<it>BRAF </it>status, phosphorylation level of the EGFR pathway, and the tumor suppression effect in vivo, using a human colon cancer cell line HT29, which exhibited the highest EGFR expression in response to the cetuximab therapy among the 6 colorectal cancer cell lines tested.</p> <p>Findings</p> <p>The conventional growth suppression assay did not work efficiently with cetuximab. EGF, TGF-α, and IGF activated the EGFR/MAPK cell signaling pathway by initiating the phosphorylation of EGFR. Cetuximab partially inhibited the EGFR/MAPK pathway induced by EGF, TGF-α, and IGF. However, cetuximab exposure induced the EGFR, MEK, and ERK1/2 phosphorylation by itself. Mouse xenograft tumor growth was significantly inhibited by cetuximab and both cetuximab-treated and -untreated xenograft specimens exhibited phosphorylations of the EGFR pathway proteins.</p> <p>Conclusions</p> <p>We have confirmed that cetuximab inhibited the EGFR/MAPK pathway and reduced tumor growth in the xenografts while the remaining tumor showed EGFR pathway activation. These results suggest that: ( i ) The effect of cetuximab in growth signaling is not sufficient to induce complete growth suppression in vitro; ( ii ) time-course monitoring may be necessary to evaluate the effect of cetuximab because EGFR signaling is transmitted in a minute order; and ( iii ) cetuximab treatment may have cells acquired resistant selectively survived in the heterogeneous cancer population.</p
GWAS of bipolar disorder
Genome-wide association studies (GWASs) have identified several susceptibility loci for bipolar disorder (BD) and shown that the genetic architecture of BD can be explained by polygenicity, with numerous variants contributing to BD. In the present GWAS (Phase I/II), which included 2964 BD and 61 887 control subjects from the Japanese population, we detected a novel susceptibility locus at 11q12.2 (rs28456, P=6.4 × 10−9), a region known to contain regulatory genes for plasma lipid levels (FADS1/2/3). A subsequent meta-analysis of Phase I/II and the Psychiatric GWAS Consortium for BD (PGC-BD) identified another novel BD gene, NFIX (P best=5.8 × 10−10), and supported three regions previously implicated in BD susceptibility: MAD1L1 (P best=1.9 × 10−9), TRANK1 (P best=2.1 × 10−9) and ODZ4 (P best=3.3 × 10−9). Polygenicity of BD within Japanese and trans-European-Japanese populations was assessed with risk profile score analysis. We detected higher scores in BD cases both within (Phase I/II) and across populations (Phase I/II and PGC-BD). These were defined by (1) Phase II as discovery and Phase I as target, or vice versa (for ‘within Japanese comparisons’, Pbest~10−29, R2~2%), and (2) European PGC-BD as discovery and Japanese BD (Phase I/II) as target (for ‘trans-European-Japanese comparison,’ Pbest~10−13, R2~0.27%). This ‘trans population’ effect was supported by estimation of the genetic correlation using the effect size based on each population (liability estimates~0.7). These results indicate that (1) two novel and three previously implicated loci are significantly associated with BD and that (2) BD ‘risk’ effect are shared between Japanese and European populations
The Physics of the B Factories
This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C
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