76 research outputs found
Superconformal Flavor Simplified
A simple explanation of the flavor hierarchies can arise if matter fields
interact with a conformal sector and different generations have different
anomalous dimensions under the CFT. However, in the original study by Nelson
and Strassler many supersymmetric models of this type were considered to be
'incalculable' because the R-charges were not sufficiently constrained by the
superpotential. We point out that nearly all such models are calculable with
the use of a-maximization. Utilizing this, we construct the simplest
vector-like flavor models and discuss their viability. A significant constraint
on these models comes from requiring that the visible gauge couplings remain
perturbative throughout the conformal window needed to generate the
hierarchies. However, we find that there is a small class of simple flavor
models that can evade this bound.Comment: 43 pages, 1 figure; V3: small corrections and clarifications,
references adde
FCNC Effects in a Minimal Theory of Fermion Masses
As a minimal theory of fermion masses we extend the SM by heavy vectorlike
fermions, with flavor-anarchical Yukawa couplings, that mix with chiral
fermions such that small SM Yukawa couplings arise from small mixing angles.
This model can be regarded as an effective description of the fermionic sector
of a large class of existing flavor models and thus might serve as a useful
reference frame for a further understanding of flavor hierarchies in the SM.
Already such a minimal framework gives rise to FCNC effects through exchange of
massive SM bosons whose couplings to the light fermions get modified by the
mixing. We derive general formulae for these corrections and discuss the bounds
on the heavy fermion masses. Particularly stringent bounds, in a few TeV range,
come from the corrections to the Z couplings.Comment: 19 pages, 1 figur
Flavour in supersymmetry: horizontal symmetries or wave function renormalisation
We compare theoretical and experimental predictions of two main classes of
models addressing fermion mass hierarchies and flavour changing neutral
currents (FCNC) effects in supersymmetry: Froggatt-Nielsen (FN) U(1) gauged
flavour models and Nelson-Strassler/extra dimensional models with hierarchical
wave functions for the families. We show that whereas the two lead to identical
predictions in the fermion mass matrices, the second class generates a stronger
suppression of FCNC effects. We prove that, whereas at first sight the FN setup
is more constrained due to anomaly cancelation conditions, imposing unification
of gauge couplings in the second setup generates conditions which precisely
match the mixed anomaly constraints in the FN setup. Finally, we provide an
economical extra dimensional realisation of the hierarchical wave functions
scenario in which the leptonic FCNC can be efficiently suppressed due to the
strong coupling (CFT) origin of the electron mass.Comment: 23 page
Support for smoke-free policies in the Cyprus hospitality industry
Objectives
The present study used attitudinal and behavioural indicators to measure support for smoke-free policies among employers and employees in the hospitality industry in Cyprus.
Methods
A representative sample of 600 participants (95 % response rate) completed anonymous structured questionnaires on demographic variables, smoking status, exposure to second-hand smoke at work and related health beliefs, social norms, and smoke-free policy support.
Results
Participants were predominantly males (68.3 %), with a mean age of 40 years (SD = 12.69), and 39.7 % were employers/owners of the hospitality venue. Analysis of variance showed that employers and smokers were less supportive of smoke-free policies, as compared to employees and non-smokers. Linear regression models showed that attitudes towards smoke-free policy were predicted by smoking status, SHS exposure and related health beliefs, and social norm variables. Logistic regression analysis showed that willingness to confront a policy violator was predicted by SHS exposure, perceived prevalence of smoker clients, and smoke-free policy attitudes.
Conclusions
SHS exposure and related health beliefs, and normative factors should be targeted by interventions aiming to promote policy support in the hospitality industry in Cyprus
Coping with genetic diversity: the contribution of pathogen and human genomics to modern vaccinology
Instrumentation for fluorescence lifetime measurement using photon counting
We describe the evolution of HORIBA Jobin Yvon IBH Ltd, and its time-correlated single-photon counting (TCSPC) products, from university research beginnings through to its present place as a market leader in fluorescence lifetime spectroscopy. The company philosophy is to ensure leading-edge research capabilities continue to be incorporated into instruments in order to meet the needs of the diverse range of customer applications, which span a multitude of scientific and engineering disciplines. We illustrate some of the range of activities of a scientific instrument company in meeting this goal and highlight by way of an exemplar the performance of the versatile DeltaFlex instrument in measuring fluorescence lifetimes. This includes resolving fluorescence lifetimes down to 5 ps, as frequently observed in energy transfer, nanoparticle metrology with sub-nanometre resolution and measuring a fluorescence lifetime in as little as 60 μs for the study of transient species and kinetics
Genomic-based-breeding tools for tropical maize improvement
Maize has traditionally been the main staple diet in the Southern Asia and Sub-Saharan Africa and widely grown by millions of resource poor small scale farmers. Approximately, 35.4 million hectares are sown to tropical maize, constituting around 59% of the developing worlds. Tropical maize encounters tremendous challenges besides poor agro-climatic situations with average yields recorded <3 tones/hectare that is far less than the average of developed countries. On the contrary to poor yields, the demand for maize as food, feed, and fuel is continuously increasing in these regions. Heterosis breeding introduced in early 90 s improved maize yields significantly, but genetic gains is still a mirage, particularly for crop growing under marginal environments. Application of molecular markers has accelerated the pace of maize breeding to some extent. The availability of array of sequencing and genotyping technologies offers unrivalled service to improve precision in maize-breeding programs through modern approaches such as genomic selection, genome-wide association studies, bulk segregant analysis-based sequencing approaches, etc. Superior alleles underlying complex traits can easily be identified and introgressed efficiently using these sequence-based approaches. Integration of genomic tools and techniques with advanced genetic resources such as nested association mapping and backcross nested association mapping could certainly address the genetic issues in maize improvement programs in developing countries. Huge diversity in tropical maize and its inherent capacity for doubled haploid technology offers advantage to apply the next generation genomic tools for accelerating production in marginal environments of tropical and subtropical world. Precision in phenotyping is the key for success of any molecular-breeding approach. This article reviews genomic technologies and their application to improve agronomic traits in tropical maize breeding has been reviewed in detail
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