Bulk Axions, Brane Back-reaction and Fluxes

Extra-dimensional models can involve bulk pseudo-Goldstone bosons (pGBs) whose shift symmetry is explicitly broken only by physics localized on branes. Reliable calculation of their low-energy potential is often difficult because it requires details of the stabilization of the extra dimensions. In rugby ball solutions, for which two compact extra dimensions are stabilized in the presence of only positive-tension brane sources, the effects of brane back-reaction can be computed explicitly. This allows the calculation of the shape of the low-energy pGB potential and response of the extra dimensional geometry as a function of the perturbing brane properties. If the pGB-dependence is a small part of the total brane tension a very general analysis is possible, permitting an exploration of how the system responds to frustration when the two branes disagree on what the proper scalar vacuum should be. We show how the low-energy potential is given by the sum of brane tensions (in agreement with common lore) when only the brane tensions couple to the pGB. We also show how a direct brane coupling to the flux stabilizing the extra dimensions corrects this result in a way that does not simply amount to the contribution of the flux to the brane tensions. We calculate the mass of the would-be zero mode, and briefly describe several potential applications, including a brane realization of `natural inflation,' and a dynamical mechanism for suppressing the couplings of the pGB to matter localized on the branes. Since the scalar can be light enough to be relevant to precision tests of gravity (in a technically natural way) this mechanism can be relevant to evading phenomenological bounds.Comment: 36 pages, JHEP styl

The walkthrough method : an approach to the study of apps

Software applications (apps) are now prevalent in the digital media environment. They are the site of significant sociocultural and economic transformations across many domains, from health and relationships to entertainment and everyday finance. As relatively closed technical systems, apps pose new methodological challenges for sociocultural digital media research. This paper describes a method, grounded in a combination of science and technology studies with cultural studies, through which researchers can perform a critical analysis of a given app. The method involves establishing an app’s environment of expected use by identifying and describing its vision, operating model, and modes of governance. It then deploys a walkthrough technique to systematically and forensically step through the various stages of app registration and entry, everyday use, and discontinuation of use. The walkthrough method establishes a foundational corpus of data upon which can be built a more detailed analysis of an app’s intended purpose, embedded cultural meanings, and implied ideal users and uses. The walkthrough also serves as a foundation for further user-centred research that can identify how users resist these arrangements and appropriate app technology for their own purposes

A promoting early presentation intervention increases breast cancer awareness in older women after 2 years: a randomised controlled trial

BACKGROUND: We have developed the Promoting Early Presentation (PEP) Intervention to equip older women with the knowledge, skills, confidence and motivation to present promptly with breast symptoms, and thereby improve survival from breast cancer. The PEP Intervention consists of a 10-min interaction between a radiographer and an older woman, supported by a booklet. Our previous report showed that at 1 year, the PEP intervention increased the proportion who were breast cancer aware compared with usual care.METHODS: We randomised 867 women aged 67-70 years attending for their final routine appointment on the National Health Service Breast Screening Programme to receive the PEP Intervention, a booklet alone or usual care. The primary outcome was breast cancer awareness measured using a validated questionnaire asking about knowledge of breast cancer symptoms, knowledge that the risk of breast cancer increases with age and breast checking behaviour.RESULTS: At 2 years, the PEP Intervention increased the proportion who were breast cancer aware compared with usual care (21 vs 6%; odds ratio 8.1, 95% confidence interval 2.7-25.0).CONCLUSIONS: The uniquely large and sustained effect of the PEP Intervention on breast cancer awareness increases the likelihood that a woman will present promptly should she develop breast cancer symptoms up to many years later. British Journal of Cancer (2011) 105, 18-21. doi: 10.1038/bjc.2011.205 www.bjcancer.com Published online 7 June 2011 (C) 2011 Cancer Research U

Studying the Salt Dependence of the Binding of σ70 and σ32 to Core RNA Polymerase Using Luminescence Resonance Energy Transfer

The study of protein-protein interactions is becoming increasingly important for understanding the regulation of many cellular processes. The ability to quantify the strength with which two binding partners interact is desirable but the accurate determination of equilibrium binding constants is a difficult process. The use of Luminescence Resonance Energy Transfer (LRET) provides a homogeneous binding assay that can be used for the detection of protein-protein interactions. Previously, we developed an LRET assay to screen for small molecule inhibitors of the interaction of σ70 with theβ' coiled-coil fragment (amino acids 100–309). Here we describe an LRET binding assay used to monitor the interaction of E. coli σ70 and σ32 with core RNA polymerase along with the controls to verify the system. This approach generates fluorescently labeled proteins through the random labeling of lysine residues which enables the use of the LRET assay for proteins for which the creation of single cysteine mutants is not feasible. With the LRET binding assay, we are able to show that the interaction of σ70 with core RNAP is much more sensitive to NaCl than to potassium glutamate (KGlu), whereas the σ32 interaction with core RNAP is insensitive to both salts even at concentrations >500 mM. We also find that the interaction of σ32 with core RNAP is stronger than σ70 with core RNAP, under all conditions tested. This work establishes a consistent set of conditions for the comparison of the binding affinities of the E.coli sigma factors with core RNA polymerase. The examination of the importance of salt conditions in the binding of these proteins could have implications in both in vitro assay conditions and in vivo function

Long-lived charged Higgs at LHC as a probe of scalar Dark Matter

We study inert charged Higgs boson $H^\pm$ production and decays at LHC experiments in the context of constrained scalar dark matter model (CSDMM). In the CSDMM the inert doublet and singlet scalar's mass spectrum is predicted from the GUT scale initial conditions via RGE evolution. We compute the cross sections of processes $pp\to H^+H^-,\, H^\pm S_i^0$ at the LHC and show that for light $H^\pm$ the first one is dominated by top quark mediated 1-loop diagram with Higgs boson in s-channel. In a significant fraction of the parameter space $H^\pm$ are long-lived because their decays to predominantly singlet scalar dark matter (DM) and next-to-lightest (NL) scalar, $H^\pm\to S_{\text{DM, NL}} ff',$ are suppressed by the small singlet-doublet mixing angle and by the moderate mass difference $\Delta M=M_{H^+}-M_{\text{DM}} .$ The experimentally measurable displaced vertex in $H^\pm$ decays to leptons and/or jets and missing energy allows one to discover the $H^+H^-$ signal over the huge $W^+W^-$ background. We propose benchmark points for studies of this scenario at the LHC. If, however, $H^\pm$ are short-lived, the subsequent decays $S_{\text{NL}}\to S_{\text{DM}} f\bar f$ necessarily produce additional displaced vertices that allow to reconstruct the full $H^\pm$ decay chain.Comment: 15 pages, 5 figure

On theories of enhanced CP violation in B_s,d meson mixing

The DO collaboration has measured a deviation from the standard model (SM) prediction in the like sign dimuon asymmetry in semileptonic b decay with a significance of 3.2 sigma. We discuss how minimal flavour violating (MFV) models with multiple scalar representations can lead to this deviation through tree level exchanges of new MFV scalars. We review how the two scalar doublet model can accommodate this result and discuss some of its phenomenology. Limits on electric dipole moments suggest that in this model the coupling of the charged scalar to the right handed u-type quarks is suppressed while its coupling to the d-type right handed quarks must be enhanced. We construct an extension of the MFV two scalar doublet model where this occurs naturally.Comment: 10 pages, 7 figures, v3 final JHEP versio

New insights on above ground biomass and forest attributes in tropical montane forests

Despite the potential of tropical montane forests to store and sequester substantial amounts of carbon, little is known about the above ground biomass (AGB) and the factors affecting it in these ecosystems, especially in Africa. We investigated the height-diameter allometry, AGB, and related differences in AGB to taxonomic and structural forest attributes in three distinct forest types (dry, mixed species and elfin) in three mountains of northern Kenya. We established 24 permanent plots (20 m × 100 m) and sampled all trees ≥10 cm diameter following standard Rainfor protocols. We identified that different height-diameter allometric models could be used for different forests types, with the exception of the Michaelis–Menten model. In our study area, model choice had little effects on AGB estimates. In general, mixed forests had greater AGB than other forest types: in Mt Nyiro AGB estimates were 611, 408 and 241 Mg ha−1 for mixed, elfin and dry forests respectively. Forests in Mt Nyiro, the highest mountain had greater AGB than in the other mountains. In our study area, differences in AGB were related to forest structure attributes, with little influence of taxonomic attributes. The mixed and elfin forests in Mt Nyiro, dominated by Podocarpus latifolius and Faurea saligna contained comparable AGB to lowland rainforests, highlighting the importance of tropical montane forests as large carbon stock, which could be released if converted to another land cover type

Inflation and dark matter in two Higgs doublet models

We consider the Higgs inflation in the extension of the Standard Model with two Higgs doublets coupled to gravity non-minimally. In the presence of an approximate global U(1) symmetry in the Higgs sector, both radial and angular modes of neutral Higgs bosons drive inflation where large non-Gaussianity is possible from appropriate initial conditions on the angular mode. We also discuss the case with single-field inflation for which the U(1) symmetry is broken to a Z_2 subgroup. We show that inflationary constraints, perturbativity and stability conditions restrict the parameter space of the Higgs quartic couplings at low energy in both multi- and single-field cases. Focusing on the inert doublet models where Z_2 symmetry remains unbroken at low energy, we show that the extra neutral Higgs boson can be a dark matter candidate consistent with the inflationary constraints. The doublet dark matter is always heavy in multi-field inflation while it can be light due to the suppression of the co-annihilation in single-field inflation. The implication of the extra quartic couplings on the vacuum stability bound is also discussed in the light of the recent LHC limits on the Higgs mass.Comment: (v1) 28 pages, 8 figures; (v2) 29 pages, a new subsection 3.3 added, references added and typos corrected, to appear in Journal of High Energy Physic

MFV Reductions of MSSM Parameter Space

The 100+ free parameters of the minimal supersymmetric standard model (MSSM) make it computationally difficult to compare systematically with data, motivating the study of specific parameter reductions such as the cMSSM and pMSSM. Here we instead study the reductions of parameter space implied by using minimal flavour violation (MFV) to organise the R-parity conserving MSSM, with a view towards systematically building in constraints on flavour-violating physics. Within this framework the space of parameters is reduced by expanding soft supersymmetry-breaking terms in powers of the Cabibbo angle, leading to a 24-, 30- or 42-parameter framework (which we call MSSM-24, MSSM-30, and MSSM-42 respectively), depending on the order kept in the expansion. We provide a Bayesian global fit to data of the MSSM-30 parameter set to show that this is manageable with current tools. We compare the MFV reductions to the 19-parameter pMSSM choice and show that the pMSSM is not contained as a subset. The MSSM-30 analysis favours a relatively lighter TeV-scale pseudoscalar Higgs boson and $\tan \beta \sim 10$ with multi-TeV sparticles.Comment: 2nd version, minor comments and references added, accepted for publication in JHE

Oligomerization of the E. coli Core RNA Polymerase: Formation of (α2ββ'ω)2–DNA Complexes and Regulation of the Oligomerization by Auxiliary Subunits

In this work, using multiple, dissimilar physico-chemical techniques, we demonstrate that the Escherichia coli RNA polymerase core enzyme obtained through a classic purification procedure forms stable (α2ββ'ω)2 complexes in the presence or absence of short DNA probes. Multiple control experiments indicate that this self-association is unlikely to be mediated by RNA polymerase-associated non-protein molecules. We show that the formation of (α2ββ'ω)2 complexes is subject to regulation by known RNA polymerase interactors, such as the auxiliary SWI/SNF subunit of RNA polymerase RapA, as well as NusA and σ70. We also demonstrate that the separation of the core RNA polymerase and RNA polymerase holoenzyme species during Mono Q chromatography is likely due to oligomerization of the core enzyme. We have analyzed the oligomeric state of the polymerase in the presence or absence of DNA, an aspect that was missing from previous studies. Importantly, our work demonstrates that RNA polymerase oligomerization is compatible with DNA binding. Through in vitro transcription and in vivo experiments (utilizing a RapAR599/Q602 mutant lacking transcription-stimulatory function), we demonstrate that the formation of tandem (α2ββ'ω)2–DNA complexes is likely functionally significant and beneficial for the transcriptional activity of the polymerase. Taken together, our findings suggest a novel structural aspect of the E. coli elongation complex. We hypothesize that transcription by tandem RNA polymerase complexes initiated at hypothetical bidirectional “origins of transcription” may explain recurring switches of the direction of transcription in bacterial genomes