683 research outputs found
Cosmological Constraints on Dissipative Models of Inflation
(Abridged) We study dissipative inflation in the regime where the dissipative
term takes a specific form, \Gamma=\Gamma(\phi), analyzing two models in the
weak and strong dissipative regimes with a SUSY breaking potential. After
developing intuition about the predictions from these models through analytic
approximations, we compute the predicted cosmological observables through full
numerical evolution of the equations of motion, relating the mass scale and
scale of dissipation to the characteristic amplitude and shape of the
primordial power spectrum. We then use Markov Chain Monte Carlo techniques to
constrain a subset of the models with cosmological data from the cosmic
microwave background (WMAP three-year data) and large scale structure (SDSS
Luminous Red Galaxy power spectrum). We find that the posterior distributions
of the dissipative parameters are highly non-Gaussian and their allowed ranges
agree well with the expectations obtained using analytic approximations. In the
weak regime, only the mass scale is tightly constrained; conversely, in the
strong regime, only the dissipative coefficient is tightly constrained. A lower
limit is seen on the inflation scale: a sub-Planckian inflaton is disfavoured
by the data. In both weak and strong regimes, we reconstruct the limits on the
primordial power spectrum and show that these models prefer a {\it red}
spectrum, with no significant running of the index. We calculate the reheat
temperature and show that the gravitino problem can be overcome with large
dissipation, which in turn leads to large levels of non-Gaussianity: if
dissipative inflation is to evade the gravitino problem, the predicted level of
non-Gaussianity might be seen by the Planck satellite.Comment: 14 pages, 9 figures, Accepted by JCAP without text changes,
References adde
Conditional disruption of rictor demonstrates a direct requirement for mTORC2 in skin tumor development and continued growth of established tumors
These studies show for the first time that mTORC2 is essential for skin tumor development and maintenance of established tumors, but is dispensable for normal keratinocyte proliferation. They further suggest that mTORC2 controls pro-survival pathways in vitro and in tumor
Loss of miRNA biogenesis induces p19Arf-p53 signaling and senescence in primary cells
Dicer, an enzyme involved in microRNA (miRNA) maturation, is required for proper cell differentiation and embryogenesis in mammals. Recent evidence indicates that Dicer and miRNA may also regulate tumorigenesis. To better characterize the role of miRNA in primary cell growth, we generated Dicer-conditional mice. Ablation of Dicer and loss of mature miRNAs in embryonic fibroblasts up-regulated p19Arf and p53 levels, inhibited cell proliferation, and induced a premature senescence phenotype that was also observed in vivo after Dicer ablation in the developing limb and in adult skin. Furthermore, deletion of the Ink4a/Arf or p53 locus could rescue fibroblasts from premature senescence induced by Dicer ablation. Although levels of Ras and Myc oncoproteins appeared unaltered, loss of Dicer resulted in increased DNA damage and p53 activity in these cells. These results reveal that loss of miRNA biogenesis activates a DNA damage checkpoint, up-regulates p19Arf-p53 signaling, and induces senescence in primary cells
Experimental Probes of the Randall-Sundrum Infinite Extra Dimension
The phenomenological possibilities of the Randall-Sundrum non-compact extra
dimension scenario with the AdS horizon increased to approximately a millimeter
length, corresponding to an effective brane tension of TeV^4, are investigated.
The corrections to the Newtonian potential are found to be the only
observationally accessible probe of this scenario, as previously suggested in
the literature. In particular, the presence of the continuum of KK modes does
not lead to any observable collider signatures. The extent to which
experimental tests of Newtonian gravity can distinguish this scenario from the
scenario of Arkani-Hamed, Dimopoulos, and Dvali with one and two millimeter
size extra dimensions is explicitly demonstrated.Comment: 22 pages, 2 figures, references adde
Implementing paediatric appropriate use criteria for endotracheal suction to reduce complications in mechanically ventilated children with respiratory infections
BackgroundEndotracheal suction is used to maintain endotracheal tube patency. There is limited guidance to inform clinical practice for children with respiratory infections.ObjectiveThe objective of this study was to determine whether implementation of a paediatric endotracheal suction appropriate use guideline Paediatric AirWay Suction (PAWS) is associated with an increased use of appropriate and decreased use of inappropriate suction interventions.MethodsA mixed-method, pre-implementationâpost-implementation study was conducted between September 2021 and April 2022. Suction episodes in mechanically ventilated children with a respiratory infection were eligible. Using a structured approach, we implemented the PAWS guideline in a single paediatric intensive care unit. Evaluation included clinical (e.g., suction intervention appropriateness), implementation (e.g., acceptability), and cost outcomes (implementation costs). Associations between implementation of the PAWS guideline and appropriateness of endotracheal suction intervention use were investigated using generalised linear models.ResultsData from 439 eligible suctions were included in the analysis. Following PAWS implementation, inappropriate endotracheal tube intervention use reduced from 99% to 58%, an absolute reduction (AR) of 41% (95% confidence interval [CI]: 25%, 56%). Reductions were most notable for open suction systems (AR: 48%; 95% CI: 30%, 65%), 0.9% sodium chloride use (AR: 23%; 95% CI: 8%, 38%) and presuction and postsuction manual bagging (38%; 95% CI: 16%, 60%, and 86%; 95% CI: 73%, 99%), respectively. Clinicians perceived PAWS as acceptable and suitable for use.ConclusionsImplementation of endotracheal tube suction appropriate use guidelines in a mixed paediatric intensive care unit was associated with a large reduction in inappropriate suction intervention use in paediatric patients with respiratory infections
Large non-Gaussianity from two-component hybrid inflation
We study the generation of non-Gaussianity in models of hybrid inflation with
two inflaton fields, (2-brid inflation). We analyse the region in the parameter
and the initial condition space where a large non-Gaussianity may be generated
during slow-roll inflation which is generally characterised by a large f_NL,
tau_NL and a small g_NL. For certain parameter values we can satisfy
tau_NL>>f_NL^2. The bispectrum is of the local type but may have a significant
scale dependence. We show that the loop corrections to the power spectrum and
bispectrum are suppressed during inflation, if one assume that the fields
follow a classical background trajectory. We also include the effect of the
waterfall field, which can lead to a significant change in the observables
after the waterfall field is destabilised, depending on the couplings between
the waterfall and inflaton fields.Comment: 16 pages, 6 figures; v2: comments and references added, typos
corrected, matches published versio
Cosmology of Brane Models with Radion Stabilization
We analyze the cosmology of the Randall-Sundrum model and that of compact
brane models in general in the presence of a radius stabilization mechanism. We
find that the expansion of our universe is generically in agreement with the
expected effective four dimensional description. The constraint (which is
responsible for the appearance of non-conventional cosmologies in these models)
that must be imposed on the matter densities on the two branes in the theory
without a stabilized radius is a consequence of requiring a static solution
even in the absence of stabilization. Such constraints disappear in the
presence of a stablizing potential, and the ordinary FRW
(Friedmann-Robertson-Walker) equations are reproduced, with the expansion
driven by the sum of the physical values of the energy densities on the two
branes and in the bulk. For the case of the Randall-Sundrum model we examine
the kinematics of the radion field, and find that corrections to the standard
FRW equations are small for temperatures below the weak scale. We find that the
radion field has renormalizable and unsuppressed couplings to Standard Model
particles after electroweak symmetry breaking. These couplings may have
important implications for collider searches. We comment on the possibility
that matter off the TeV brane could serve as a dark matter candidate.Comment: 35 pages, Late
COâMRSA Infections in Australia Cost $3.5B Per Annum
Introduction The health and economic burdens of community-onset methicillin resistant Staphylococcus aureus (CO-MRSA) infections are needed to inform policy, planning and evidence-based practice. We aimed to synthesise data from a range of public sources to generate the first estimate of the national incidence and cost of CO-MRSA infections. Methods Incidences of CO-MRSA skin and soft tissue (SSTI), lower respiratory tract (LRTI) and bloodstream (BSI) infections were calculated for regions of Australia using data from existing literature and correspondence with specialists. Simulations estimated costs using treatment models developed for children and adults in primary or tertiary care settings and including bed-stay, diagnostics, procedures, mortalities and loss of productivity. Results Annually, in Australia there were found to be 3702 CO-MRSA SSTIs, 559 CO-MRSA BSIs and 425 CO-MRSA LRTIs, occupying 147,000 bed-days, including 1600 bed-days in intensive care. Incidence ranged from 4 /100,000 person-years in Tasmania to 243 /100,000 person-years in central Australia. CO-MRSA cost 1.9b, with bed occupancies accounting for â„94%. Conclusion This was the first evaluation of the health and economic burden of CO-MRSA in Australia. We found a need for increased and more consistent data collection for a significant and expensive disease. Disclosure of Interest Statement: This research was funded by NHMRC grant GNT1027589
Single-Scale Natural SUSY
We consider the prospects for natural SUSY models consistent with current
data. Recent constraints make the standard paradigm unnatural so we consider
what could be a minimal extension consistent with what we now know. The most
promising such scenarios extend the MSSM with new tree-level Higgs interactions
that can lift its mass to at least 125 GeV and also allow for flavor-dependent
soft terms so that the third generation squarks are lighter than current bounds
on the first and second generation squarks. We argue that a common feature of
almost all such models is the need for a new scale near 10 TeV, such as a scale
of Higgsing or confinement of a new gauge group. We consider the question
whether such a model can naturally derive from a single mass scale associated
with supersymmetry breaking. Most such models simply postulate new scales,
leaving their proximity to the scale of MSSM soft terms a mystery. This
coincidence problem may be thought of as a mild tuning, analogous to the usual
mu problem. We find that a single mass scale origin is challenging, but suggest
that a more natural origin for such a new dynamical scale is the gravitino
mass, m_{3/2}, in theories where the MSSM soft terms are a loop factor below
m_{3/2}. As an example, we build a variant of the NMSSM where the singlet S is
composite, and the strong dynamics leading to compositeness is triggered by
masses of order m_{3/2} for some fields. Our focus is the Higgs sector, but our
model is compatible with a light stop (with the other generation squarks heavy,
or with R-parity violation or another mechanism to hide them from current
searches). All the interesting low-energy mass scales, including linear terms
for S playing a key role in EWSB, arise dynamically from the single scale
m_{3/2}. However, numerical coefficients from RG effects and wavefunction
factors in an extra dimension complicate the otherwise simple story.Comment: 32 pages, 3 figures; version accepted by JHE
Phenomenological Implications of Deflected Mirage Mediation: Comparison with Mirage Mediation
We compare the collider phenomenology of mirage mediation and deflected
mirage mediation, which are two recently proposed "mixed" supersymmetry
breaking scenarios motivated from string compactifications. The scenarios
differ in that deflected mirage mediation includes contributions from gauge
mediation in addition to the contributions from gravity mediation and anomaly
mediation also present in mirage mediation. The threshold effects from gauge
mediation can drastically alter the low energy spectrum from that of pure
mirage mediation models, resulting in some cases in a squeezed gaugino spectrum
and a gluino that is much lighter than other colored superpartners. We provide
several benchmark deflected mirage mediation models and construct model lines
as a function of the gauge mediation contributions, and discuss their discovery
potential at the LHC.Comment: 29 pages, 9 figure
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