389 research outputs found
Dimeric SecA Couples the Preprotein Translocation in an Asymmetric Manner
The Sec translocase mediates the post-translational translocation of a number of preproteins through the inner membrane in bacteria. In the initiatory translocation step, SecB targets the preprotein to the translocase by specific interaction with its receptor SecA. The latter is the ATPase of Sec translocase which mediates the post-translational translocation of preprotein through the protein-conducting channel SecYEG in the bacterial inner membrane. We examined the structures of Escherichia coli Sec intermediates in solution as visualized by negatively stained electron microscopy in order to probe the oligomeric states of SecA during this process. The symmetric interaction pattern between the SecA dimer and SecB becomes asymmetric in the presence of proOmpA, and one of the SecA protomers predominantly binds to SecB/proOmpA. Our results suggest that during preprotein translocation, the two SecA protomers are different in structure and may play different roles
When Anomaly Mediation is UV Sensitive
Despite its successes---such as solving the supersymmetric flavor
problem---anomaly mediated supersymmetry breaking is untenable because of its
prediction of tachyonic sleptons. An appealing solution to this problem was
proposed by Pomarol and Rattazzi where a threshold controlled by a light field
deflects the anomaly mediated supersymmetry breaking trajectory, thus evading
tachyonic sleptons. In this paper we examine an alternate class of deflection
models where the non-supersymmetric threshold is accompanied by a heavy,
instead of light, singlet. The low energy form of this model is the so-called
extended anomaly mediation proposed by Nelson and Weiner, but with potential
for a much higher deflection threshold. The existence of this high deflection
threshold implies that the space of anomaly mediated supersymmetry breaking
deflecting models is larger than previously thought.Comment: 14 pages, 1 figure (version to appear in JHEP
Technical challenges of providing record linkage services for research
Background: Record linkage techniques are widely used to enable health researchers to gain event based longitudinal information for entire populations. The task of record linkage is increasingly being undertaken by specialised linkage units (SLUs). In addition to the complexity of undertaking probabilistic record linkage, these units face additional technical challenges in providing record linkage âas a serviceâ for research. The extent of this functionality, and approaches to solving these issues, has had little focus in the record linkage literature. Few, if any, of the record linkage packages or systems currently used by SLUs include the full range of functions required. Methods: This paper identifies and discusses some of the functions that are required or undertaken by SLUs in the provision of record linkage services. These include managing routine, on-going linkage; storing and handling changing data; handling different linkage scenarios; accommodating ever increasing datasets. Automated linkage processes are one way of ensuring consistency of results and scalability of service. Results: Alternative solutions to some of these challenges are presented. By maintaining a full history of links, and storing pairwise information, many of the challenges around handling âopenâ records, and providing automated managed extractions are solved. A number of these solutions were implemented as part of the development of the National Linkage System (NLS) by the Centre for Data Linkage (part of the Population Health Research Network) in Australia.Conclusions: The demand for, and complexity of, linkage services are growing. This presents as a challenge to SLUs as they seek to service the varying needs of dozens of research projects annually. Linkage units need to be both flexible and scalable to meet this demand. It is hoped the solutions presented here can help mitigate these difficulties
Soft branes in supersymmetry-breaking backgrounds
We revisit the analysis of effective field theories resulting from
non-supersymmetric perturbations to supersymmetric flux compactifications of
the type-IIB superstring with an eye towards those resulting from the
backreaction of a small number of anti-D3-branes. Independently of the
background, we show that the low-energy Lagrangian describing the fluctuations
of a stack of probe D3-branes exhibits soft supersymmetry breaking, despite
perturbations to marginal operators that were not fully considered in some
previous treatments. We take this as an indication that the breaking of
supersymmetry by anti-D3-branes or other sources may be spontaneous rather than
explicit. In support of this, we consider the action of an anti-D3-brane
probing an otherwise supersymmetric configuration and identify a candidate for
the corresponding goldstino.Comment: 36+5 pages. References added, minor typos correcte
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
Mixed Mediation of Supersymmetry Breaking with Anomalous U(1) Gauge Symmetry
Models with anomalous U(1) gauge symmetry contain various superfields which
can have nonzero supersymmetry breaking auxiliary components providing the
origin of soft terms in the visible sector, e.g. the U(1) vector superfield,
the modulus or dilaton superfield implementing the Green-Schwarz anomaly
cancellation mechanism, U(1)-charged but standard model singlet matter
superfield required to cancel the Fayet-Iliopoulos term, and finally the
supergravity multiplet. We examine the relative strength between these
supersymmetry breaking components in a simple class of models, and find that
various different mixed mediations of supersymmetry breaking, involving the
modulus, gauge, anomaly and D-term mediations, can be realized depending upon
the characteristics of D-flat directions and how those D-flat directions are
stabilized with a vanishing cosmological constant. We identify two parameters
which represent such properties and thus characterize how the various
mediations are mixed. We also discuss the moduli stabilization and soft terms
in a variant of KKLT scenario, in which the visible sector K\"ahler modulus is
stabilized by the D-term potential of anomalous U(1) gauge symmetry.Comment: 30 pages, 5 figure
Why do women invest in pre-pregnancy health and care? A qualitative investigation with women attending maternity services
Background Despite the importance attributed to good pre-pregnancy care and its potential to improve pregnancy and child health outcomes, relatively little is known about why women invest in pre-pregnancy health and care. We sought to gain insight into why women invested in pre-pregnancy health and care. Methods We carried out 20 qualitative in-depth interviews with pregnant or recently pregnant women who were drawn from a survey of antenatal clinic attendees in London, UK. Interviewees were purposively sampled to include high and low investors in pre-pregnancy health and care, with variation in age, partnership status, ethnicity and pre-existing medical conditions. Data analysis was conducted using the Framework method. Results We identified three groups in relation to pre-pregnancy health and care: 1) The âpreparedâ group, who had high levels of pregnancy planning and mostly positive attitudes to micronutrient supplementation outside of pregnancy, carried out pre-pregnancy activities such as taking folic acid and making changes to diet and lifestyle. 2) The âpoor knowledgeâ group, who also had high levels of pregnancy planning, did not carry out pre-pregnancy activities and described themselves as having poor knowledge. Elsewhere in their interviews they expressed a strong dislike of micronutrient supplementation. 3) The âabsent pre-pregnancy periodâ group, had the lowest levels of pregnancy planning and also expressed anti-supplement views. Even discussing the pre-pregnancy period with this group was difficult as responses to questions quickly shifted to focus on pregnancy itself. Knowledge of folic acid was poor in all groups. Conclusion Different pre-pregnancy care approaches are likely to be needed for each of the groups. Among the âpreparedâ group, who were proactive and receptive to health messages, greater availability of information and better response from health professionals could improve the range of pre-pregnancy activities carried out. Among the âpoor knowledgeâ group, better response from health professionals might yield greater uptake of pre-pregnancy information. A different, general health strategy might be more appropriate for the âabsent pre-pregnancy periodâ group. The fact that general attitudes to micronutrient supplementation were closely related to whether or not women invested in pre-pregnancy health and care was an unanticipated finding and warrants further investigation.This report is independent research commissioned and funded by the Department of Health Policy Research Programme Pre-Pregnancy Health and Care in England: Exploring Implementation and Public Health Impact, 006/0068
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