363 research outputs found
Production of a pseudo-scalar Higgs boson at hadron colliders at next-to-next-to leading order
The production cross section for pseudo-scalar Higgs bosons at hadron
colliders is computed at next-to-next-to-leading order (NNLO) in QCD. The
pseudo-scalar Higgs is assumed to couple only to top quarks. The NNLO effects
are evaluated using an effective lagrangian where the top quarks are integrated
out. The NNLO corrections are similar in size to those found for scalar Higgs
boson production.Comment: 20 pages, 6 figures, JHEP style, Minor changes, Journal reference
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Biomass and nutrient dynamics associated with slash fires in neotropical dry forests
Unprecedented rates of deforestation and biomass burning in tropical dry forests are dramatically influencing biogeochemical cycles, resulting in resource depletion, declines in biodiversity, and atmospheric pollution. We quantified the effects of defores- tation and varying levels of slash-fire severity on nutrient losses and redistribution in a second-growth tropical dry forest ("Caatinga") near Serra Talhada, Pernambuco, Brazil. Total aboveground biomass prior to burning was 74 Mg/ha. Nitrogen and phosphorus concentrations were highest in litter, leaves attached to slash, and fine wood debris (<0.64 cm diameter). While these components comprised only 30% of the prefire aboveground biomass, they accounted for -60% of the aboveground pools of N and P. Three experi- mental fires were conducted during the 1989 burning season. In these treatments con- sumption was 78, 88, and 95% of the total aboveground biomass. As much as 96% of the prefire aboveground N and C pools and 56% of the prefire aboveground P pool was lost during combustion processes. Nitrogen losses exceeded 500 kg/ha and P losses exceeded 20 kg/ha in the fires of the greatest severity. With increasing fire severity, the concentrations of N and P in ash decreased while the concentration of Ca increased. This indicates greater amounts of these nutrients were volatilized (i.e., greater ecosystem losses occurred) with increasing fire severity. Following fire, up to 47% of the residual aboveground N and 84% of the residual aboveground P were in the form of ash, which was quickly lost from the site via wind erosion. Fires appeared to have a minor immediate effect on total N, C, or P in the soils. However, soils in forests with no history of cultivation had significantly higher concentrations of C and P than second-growth forests. Based upon the measured losses of nutrients from these single slash-burning events, it would likely require a century
or more of fallow for reaccumulation to occur. However, current fallow periods in this region are 15 yr or less
Soft and virtual corrections to pp -> H + X at NNLO
The contributions of virtual corrections and soft gluon emission to the
inclusive Higgs production cross section pp -> H + X are computed at
next-to-next-to-leading order in the heavy top quark limit. We show that this
part of the total cross section is well behaved in the sense of perturbative
convergence, with the NNLO corrections amounting to an enhancement of the NLO
cross section by \sim 5% for LHC and 10-20% for the Tevatron. We compare our
results with an existing estimate of the full NNLO effects and argue that an
analytic evaluation of the hard scattering contributions is needed.Comment: 16 pages, 7 figures, 16 ps files embedded with epsf. Minor
modifications: references and note added, results unchange
Lrg1 Regulates β (1, 3)-Glucan Masking in Candida albicans through the Cek1 MAP Kinase Pathway
Candida albicans is among the most prevalent opportunistic human fungal pathogens. The ability to mask the immunogenic polysaccharide β (1,3)-glucan from immune detection via a layer of mannosylated proteins is a key virulence factor of C. albicans. We previously reported that hyperactivation of the Cek1 mitogen-activated protein (MAP) kinase pathway promotes β (1,3)-glucan exposure. In this communication, we report a novel upstream regulator of Cek1 activation and characterize the impact of Cek1 activity on fungal virulence. Lrg1 encodes a GTPase-activating protein (GAP) that has been suggested to inhibit the GTPase Rho1. We found that disruption of LRG1 causes Cek1 hyperactivation and β (1,3)-glucan unmasking. However, when GTPase activation was measured for a panel of GTPases, the lrg1ΔΔ mutant exhibited increased activation of Cdc42 and Ras1 but not Rho1 or Rac1. Unmasking and Cek1 activation in the lrg1ΔΔ mutant can be blocked by inhibition of the Ste11 MAP kinase kinase kinase (MAPKKK), indicating that the lrg1ΔΔ mutant acts through the canonical Cek1 MAP kinase cascade. In order to determine how Cek1 hyperactivation specifically impacts virulence, a doxycycline-repressible hyperactive STE11ΔN467 allele was expressed in C. albicans. In the absence of doxycycline, this allele overexpressed STE11ΔN467, which induced production of proinflammatory tumor necrosis factor alpha (TNF-α) from murine macrophages. This in vitrophenotype correlates with decreased colonization and virulence in a mouse model of systemic infection. The mechanism by which Ste11ΔN467 causes unmasking was explored with RNA sequencing (RNA-Seq) analysis. Overexpression of Ste11ΔN467 caused upregulation of the Cph1 transcription factor and of a group of cell wall-modifying proteins which are predicted to impact cell wall architecture
Hepatitis C viral evolution in genotype 1 treatment-naĂŻve and treatment-experienced patients receiving telaprevir-based therapy in clinical trials
Background: In patients with genotype 1 chronic hepatitis C infection, telaprevir (TVR) in combination with peginterferon and ribavirin (PR) significantly increased sustained virologic response (SVR) rates compared with PR alone. However, genotypic changes could be observed in TVR-treated patients who did not achieve an SVR.
Methods: Population sequence analysis of the NS3•4A region was performed in patients who did not achieve SVR with TVR-based treatment.
Results: Resistant variants were observed after treatment with a telaprevir-based regimen in 12% of treatment-naĂŻve patients (ADVANCE; T12PR arm), 6% of prior relapsers, 24% of prior partial responders, and 51% of prior null responder patients (REALIZE, T12PR48 arms). NS3 protease variants V36M, R155K, and V36M+R155K emerged frequently in patients with genotype 1a and V36A, T54A, and A156S/T in patients with genotype 1b. Lower-level resistance to telaprevir was conferred by V36A/M, T54A/S, R155K/T, and A156S variants; and higher-level resistance to telaprevir was conferred by A156T and V36M+R155K variants. Virologic failure during telaprevir treatment was more common in patients with genotype 1a and in prior PR nonresponder patients and was associated with higher-level telaprevir-resistant variants. Relapse was usually associated with wild-type or lower-level resistant variants. After treatment, viral populations were wild-type with a median time of 10 months for genotype 1a and 3 weeks for genotype 1b patients.
Conclusions: A consistent, subtype-dependent resistance profile was observed in patients who did not achieve an SVR with telaprevir-based treatment. The primary role of TVR is to inhibit wild-type virus and variants with lower-levels of resistance to telaprevir. The complementary role of PR is to clear any remaining telaprevir-resistant variants, especially higher-level telaprevir-resistant variants. Resistant variants are detectable in most patients who fail to achieve SVR, but their levels decline over time after treatment
Triad representation of the Chern-Simons state in quantum gravity
We investigate a triad representation of the Chern-Simons state of quantum
gravity with a non-vanishing cosmological constant. It is shown that the
Chern-Simons state, which is a well-known exact wavefunctional within the
Ashtekar theory, can be transformed to the real triad representation by means
of a suitably generalized Fourier transformation, yielding a complex integral
representation for the corresponding state in the triad variables. It is found
that topologically inequivalent choices for the complex integration contour
give rise to linearly independent wavefunctionals in the triad representation,
which all arise from the one Chern-Simons state in the Ashtekar variables. For
a suitable choice of the normalization factor, these states turn out to be
gauge-invariant under arbitrary, even topologically non-trivial
gauge-transformations. Explicit analytical expressions for the wavefunctionals
in the triad representation can be obtained in several interesting asymptotic
parameter regimes, and the associated semiclassical 4-geometries are discussed.
In restriction to Bianchi-type homogeneous 3-metrics, we compare our results
with earlier discussions of homogeneous cosmological models. Moreover, we
define an inner product on the Hilbert space of quantum gravity, and choose a
natural gauge-condition fixing the time-gauge. With respect to this particular
inner product, the Chern-Simons state of quantum gravity turns out to be a
non-normalizable wavefunctional.Comment: Latex, 30 pages, 1 figure, to appear in Phys. Rev.
Designing for emergence and innovation: Redesigning design
We reveal the surprising and counterintuitive truth that the design process, in and
of itself, is not always on the forefront of innovation. Design is a necessary but
not a sufficient condition for the success of new products and services. We
intuitively sense a connection between innovative design and emergence. The
nature of design, emergence and innovation to understand their interrelationships
and interdependencies is examined. We propose that design must harness the
process of emergence; for it is only through the bottom-up and massively
iterative unfolding of emergence that new and improved products and services
are successfully refined, introduced and diffused into the marketplace.
The relationships among design, emergence and innovation are developed.
What designers can learn from nature about emergence and evolution that will
impact the design process is explored. We examine the roles that design and
emergence play in innovation. How innovative organizations can incorporate
emergence into their design process is explored.
We demarcate the boundary between invention and innovation. We also
articulate the similarities and differences of design and emergence. We then
develop the following three hypotheses:
Hypothesis 1: “An innovative design is an emergent design.”
Hypothesis 2: “A homeostatic relationship between design and emergence is a
required condition for innovation.”Hypothesis 3: “Since design is a cultural activity and culture is an emergent
phenomenon, it follows that design leading to innovation is also an emergent
phenomenon”
We provide a number of examples of how design and emergence have worked
together and led to innovation. Examples include the tool making of early man;
the evolutionary chain of the six languages speech, writing, math, science,
computing and the Internet; the Gutenberg printing press and techniques of
collaborative filtering associated with the Internet.
We close by describing the relationship between human and naturally “designed”
systems and the notion a key element of a design is its purpose as is the case
with a living organism
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