11,890 research outputs found
p21-activated kinases and gastrointestinal cancer
Abstractp21-activated kinases (PAKs) were initially identified as effector proteins downstream from GTPases of the Rho family. To date, six members of the PAK family have been discovered in mammalian cells. PAKs play important roles in growth factor signalling, cytoskeletal remodelling, gene transcription, cell proliferation and oncogenic transformation. A large body of research has demonstrated that PAKs are up-regulated in several human cancers, and that their overexpression is linked to tumour progression and resistance to therapy. Structural and biochemical studies have revealed the mechanisms involved in PAK signalling, and opened the way to the development of PAK-targeted therapies for cancer treatment. Here we summarise recent findings from biological and clinical research on the role of PAKs in gastrointestinal cancer, and discuss the current status of PAK-targeted anticancer therapies
A Minimal Type II Seesaw Model
We propose a minimal type II seesaw model by introducing only one
right-handed neutrino besides the triplet Higgs to the standard
model. In the usual type II seesaw models with several right-handed neutrinos,
the contributions of the right-handed neutrinos and the triplet Higgs to the CP
asymmetry, which stems from the decay of the lightest right-handed neutrino,
are proportional to their respective contributions to the light neutrino mass
matrix. However, in our minimal type II seesaw model, this CP asymmetry is just
given by the one-loop vertex correction involving the triplet Higgs, even
though the contribution of the triplet Higgs does not dominate the light
neutrino masses. For illustration, the Fritzsch-type lepton mass matrices are
considered.Comment: 5 pages, 4 figures, some points clarified, useful references added,
to appear in Phys. Rev.
Scales of Mass Generation for Quarks, Leptons and Majorana Neutrinos
We study 2 --> n inelastic fermion-(anti)fermion scattering into multiple
longitudinal weak gauge bosons and derive universal upper bounds on the scales
of fermion mass generation by imposing unitarity of the S-matrix. We place new
upper limits on the scales of fermion mass generation, independent of the
electroweak symmetry breaking scale. We find that the strongest 2 --> n limits
fall in a narrow range, 3-170 TeV (with n=2-24), depending on the observed
fermion masses.Comment: Phys. Rev. Lett.(in press), minor rewordin
Double Type-II Seesaw, Baryon Asymmetry and Dark Matter for Cosmic e^\pm Excesses
We construct a new realization of type-II seesaw for neutrino masses and
baryon asymmetry by extending the standard model with one light and two heavy
singlet scalars besides one Higgs triplet. The heavy singlets pick up small
vacuum expectation values to give a suppressed trilinear coupling between the
triplet and doublet Higgs bosons after the light singlet drives the spontaneous
breaking of lepton number. The Higgs triplet can thus remain light and be
accessible at the LHC. The lepton number conserving decays of the heavy
singlets can generate a lepton asymmetry stored in the Higgs triplet to account
for the matter-antimatter asymmetry in the Universe. We further introduce
stable gauge bosons from a hidden sector, which obtain masses and annihilate
into the Higgs triplet after spontaneous breaking of the associated non-Abelian
gauge symmetry. With Breit-Wigner enhancement, the stable gauge bosons can
simultaneously explain the relic density of dark matter and the cosmic
positron/electron excesses.Comment: 9 pages, 4 figures, minor rewording, final PRD version (in Press
General formula for the four-quark condensate and vacuum factorization assumption
By differentiating the dressed quark propagator with respect to a variable
background field, the linear response of the dressed quark propagator in the
presence of the background field can be obtained. From this general method,
using the vector background field as an illustration, we derive a general
formula for the four-quark condensate . This formula contains the
corresponding fully dressed vector vertex and it is shown that factorization
for holds only when the dressed vertex is taken to be the bare one.
This property also holds for all other type of four-quark condensate.Comment: Revtex4, 11 pages, no figure
Identifying Better Effective Higgsless Theories via W_L W_L Scattering
The three site Higgsless model has been offered as a benchmark for studying
the collider phenomenology of Higgsless models. In this talk, we present how
well the three site Higgsless model performs as a general representative of
Higgsless models in describing W_L W_L scattering, and which modifications can
make it more representative. We employ general sum rules relating the masses
and couplings of the Kaluza-Klein (KK) modes of the gauge fields in continuum
and deconstructed Higgsless models as a way to compare the different theories.
After comparing the three site Higgsless model to flat and warped continuum
Higgsless models, we analyze an extensions of the three site Higgsless model,
namely, the Hidden Local Symmetry (HLS) Higgsless model. We demonstrate that
W_LW_L scattering in the HLS Higgsless model can very closely approximate
scattering in the continuum models, provided that the parameter `a' is chosen
to mimic rho-meson dominance of pi-pi scattering in QCD
Loss of aboveground forest biomass and landscape biomass variability in Missouri, US
Disturbance regimes and forests have changed over time in the eastern United States. We examined effects of historical disturbance (circa 1813 to 1850) compared to current disturbance (circa 2004 to 2008) on aboveground, live tree biomass (for trees with diameters \u3e/= 13 cm) and landscape variation of biomass in forests of the Ozarks and Plains landscapes in Missouri, USA. We simulated 10,000 one-hectare plots using random diameters generated from parameters of diameter distributions limited to diameters \u3e/= 13 cm and random densities generated from density estimates. Area-weighted mean biomass density (Mg/ha) for historical forests averaged 116 Mg/ha, ranging from 54 Mg/ha to 357 Mg/ha by small scale ecological subsections within Missouri landscapes. Area-weighted mean biomass density for current forests averaged 82 Mg/ha, ranging from 66 Mg/ha to 144 Mg/ha by ecological subsection for currently forested land. Biomass density of current forest was greater than historical biomass density for only 2 of 23 ecological subsections. Current carbon sequestration of 292 TgC on 7 million ha of forested land is less than half of the estimated historical total carbon sequestration of 693 TgC on 12 million ha. Cumulative tree cutting disturbances over time have produced forests that have less aboveground tree biomass and are uniform in biomass compared to estimates of historical biomass, which varied across Missouri landscapes. With continued relatively low rates of forest disturbance, current biomass per ha will likely increase to historical levels as the most competitive trees become larger in size and mean number of trees per ha decreases due to competition and self-thinning. Restoration of large diameter structure and forested extent of upland woodlands and floodplain forests could fulfill multiple conservation objectives, including carbon sequestration
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