8,037 research outputs found
Isospin Symmetry Breaking within the HLS Model: A Full () Mixing Scheme
We study the way isospin symmetry violation can be generated within the
Hidden Local Symmetry (HLS) Model. We show that isospin symmetry breaking
effects on pseudoscalar mesons naturally induces correspondingly effects within
the physics of vector mesons, through kaon loops. In this way, one recovers all
features traditionally expected from \rho-\omg mixing and one finds support
for the Orsay phase modelling of the e^+e^- \ra \pi^+ \pi^- amplitude. We
then examine an effective procedure which generates mixing in the whole ,
\omg, sector of the HLS Model. The corresponding model allows us to
account for all two body decays of light mesons accessible to the HLS model in
modulus and phase, leaving aside the \rho \ra \pi \pi and K^* \ra K \pi
modes only, which raise a specific problem. Comparison with experimental data
is performed and covers modulus and phase information; this represents 26
physics quantities successfully described with very good fit quality within a
constrained model which accounts for SU(3) breaking, nonet symmetry breaking in
the pseudoscalar sector and, now, isospin symmetry breaking.Comment: 38 pages, version published in Eur. Phys. J.
VMD, the WZW Lagrangian and ChPT: The Third Mixing Angle
We show that the Hidden Local Symmetry Model, supplemented with well-known
procedures for breaking flavor SU(3) and nonet symmetry, provides all the
information contained in the standard Chiral Perturbation Theory (ChPT)
Lagrangian . This allows to rely on radiative
decays of light mesons ( and ) in order to extract
some numerical information of relevance to ChPT: a value for , a quark mass ratio of , and a negligible
departure from the Gell-Mann--Okubo mass formula. The mixing angles are
and . We also give the values of all decay constants. It is shown that
the common mixing pattern with one mixing angle is actually quite
appropriate and algebraically related to the mixing pattern
presently preferred by the ChPT community. For instance the traditional
is functionally related to the ChPT and fulfills
. The vanishing of , supported by all
data on radiative decays, gives a novel relation between mixing angles and the
violation of nonet symmetry in the pseudoscalar sector. Finally, it is shown
that the interplay of nonet symmetry breaking through U(3) \ra SU(3)
U(1) satisfies all requirements of the physics of radiative decays without any
need for additional glueballs.Comment: 31 pages, 1 figur
Decoherence in Phase Space
Much of the discussion of decoherence has been in terms of a particle moving
in one dimension that is placed in an initial superposition state (a
Schr\"{o}dinger "cat" state) corresponding to two widely separated wave
packets. Decoherence refers to the destruction of the interference term in the
quantum probability function. Here, we stress that a quantitative measure of
decoherence depends not only on the specific system being studied but also on
whether one is considering coordinate, momentum or phase space. We show that
this is best illustrated by considering Wigner phase space where the measure is
again different. Analytic results for the time development of the Wigner
distribution function for a two-Gaussian Schrodinger "cat" state have been
obtained in the high-temperature limit (where decoherence can occur even for
negligible dissipation) which facilitates a simple demonstration of our
remarks.Comment: in press in Laser Phys.13(2003
A small molecule that induces assembly of a four way DNA junction at low temperature
Small molecules that induce the formation of higher order DNA structures have potential therapeutic and nanotechnology applications. Screening of a click library has identified the first compound to induce the formation of a Holliday junction structure at room temperature without the need for a high temperature annealing step
Vector Meson Mixing and Charge Symmetry Violation
We discuss the consistency of the traditional vector meson dominance (VMD)
model for photons coupling to matter, with the vanishing of vector meson-meson
and meson-photon mixing self-energies at q^2=0. This vanishing of vector mixing
has been demonstrated in the context of rho-omega mixing for a large class of
effective theories. As a further constraint on such models, we here apply them
to a study of photon-meson mixing and VMD. As an example we compare the
predicted momentum dependence of one such model with a momentum-dependent
version of VMD discussed by Sakurai in the 1960's. We find that it produces a
result which is consistent with the traditional VMD phenomenology. We conclude
that comparison with VMD phenomenology can provide a useful constraint on such
models.Comment: 7 pages, uses epsfig.sty. Publication details added to title pag
Smc5/6 is required for repair at collapsed replication forks.
In eukaryotes, three pairs of structural-maintenance-of-chromosome (SMC) proteins are found in conserved multisubunit protein complexes required for chromosomal organization. Cohesin, the Smc1/3 complex, mediates sister chromatid cohesion while two condensin complexes containing Smc2/4 facilitate chromosome condensation. Smc5/6 scaffolds an essential complex required for homologous recombination repair. We have examined the response of smc6 mutants to the inhibition of DNA replication. We define homologous recombination-dependent and -independent functions for Smc6 during replication inhibition and provide evidence for a Rad60-independent function within S phase, in addition to a Rad60-dependent function following S phase. Both genetic and physical data show that when forks collapse (i.e., are not stabilized by the Cds1Chk2 checkpoint), Smc6 is required for the effective repair of resulting lesions but not for the recruitment of recombination proteins. We further demonstrate that when the Rad60-dependent, post-S-phase Smc6 function is compromised, the resulting recombination-dependent DNA intermediates that accumulate following release from replication arrest are not recognized by the G2/M checkpoint
Making it work: A study of Australian expatriate language and cultural strategies for the workplace in Japan
Australia has maintained a steady and strong business relationship with Japan for over three decades. In fact, Japan ranks first in terms of important export markets for Australia. As a result, it can be assumed that, on a micro-level, the possibility of more expatriates from Australia being stationed in Japan will increase to facilitate business communication and transactions between Australian and Japanese companies. With the creation of multinational workplaces, including Australians and Japanese working together in Japan, comes an increasing necessity for Australian expatriates to have linguistic and cultural competence. While this has been identified in intercultural communication research, the implementations of such findings related to Japanese language proficiency and how it benefits Australian-Japanese workplace communication is seemingly sporadic despite the investment into Japanese language education by Australia
Inositol phosphatase SHIP1 is a primary target of miR-155
MicroRNA-155 (miR-155) has emerged as a critical regulator of immune cell development, function, and disease. However, the mechanistic basis for its impact on the hematopoietic system remains largely unresolved. Because miRNAs function by repressing specific mRNAs through direct 3âČUTR interactions, we have searched for targets of miR-155 implicated in the regulation of hematopoiesis. In the present study, we identify Src homology-2 domain-containing inositol 5-phosphatase 1 (SHIP1) as a direct target of miR-155, and, using gain and loss of function approaches, show that miR-155 represses SHIP1 through direct 3âČUTR interactions that have been highly conserved throughout evolution. Repression of endogenous SHIP1 by miR-155 occurred following sustained over-expression of miR-155 in hematopoietic cells both in vitro and in vivo, and resulted in increased activation of the kinase Akt during the cellular response to LPS. Furthermore, SHIP1 was also repressed by physiologically regulated miR-155, which was observed in LPS-treated WT versus miR-155â/â primary macrophages. In mice, specific knockdown of SHIP1 in the hematopoietic system following retroviral delivery of a miR-155-formatted siRNA against SHIP1 resulted in a myeloproliferative disorder, with striking similarities to that observed in miR-155-expressing mice. Our study unveils a molecular link between miR-155 and SHIP1 and provides evidence that repression of SHIP1 is an important component of miR-155 biology
Directed Percolation and Tandem Queues
We outline some of the connections which exist between directed site percolation and tandem queues, and show how these can be (and have been, although generally not in the language of queueing theory) used to explicit shape theorems for certain first and last passage percolation problems
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