1,859 research outputs found
Effects of intermediate scales on renormalization group running of fermion observables in an SO(10) model
In the context of non-supersymmetric SO(10) models, we analyze the
renormalization group equations for the fermions (including neutrinos) from the
GUT energy scale down to the electroweak energy scale, explicitly taking into
account the effects of an intermediate energy scale induced by a Pati--Salam
gauge group. To determine the renormalization group running, we use a numerical
minimization procedure based on a nested sampling algorithm that randomly
generates the values of 19 model parameters at the GUT scale, evolves them, and
finally constructs the values of the physical observables and compares them to
the existing experimental data at the electroweak scale. We show that the
evolved fermion masses and mixings present sizable deviations from the values
obtained without including the effects of the intermediate scale.Comment: Comments: 20 pages, 3 figures. Final version published in JHE
Risk assessment and suicide by patients with schizophrenia in secondary mental healthcare: a case-control study
Objectives: To investigate the role of risk assessment in predicting suicide in patients with schizophrenia spectrum disorders (SSDs) receiving secondary mental healthcare. We postulated that risk assessment plays a limited role in predicting suicide in these patients. Design: Retrospective case–control study. Setting: Anonymised electronic mental health record data from the South London and Maudsley National Health Service (NHS) Foundation Trust (SLaM) (London, UK) linked with national mortality data. Participants: In 242 227 SLaM service users up to 31 December 2013, 635 suicides were identified. 96 (15.1%) had a SSD diagnosis. Those who died before 1 January 2007 (n=25) were removed from the analyses. Thus, 71 participants with SSD who died from suicide over the study period (cases) were compared with 355 controls. Main outcome measure: Risk of suicide in relation to risk assessment ratings. Results: Cases were younger at first contact with services (mean±SD 34.5±12.6 vs 39.2±15.2) and with a higher preponderance of males (OR=2.07, 95% CI 1.18 to 3.65, p=0.01) than controls. Also, suicide occurred within 10 days after last contact with services in half of cases, with the most common suicide methods being hanging (14) and jumping (13). Cases were more likely to have the following ‘risk assessment’ items previously recorded: suicidal history (OR=4.42, 95% CI 2.01 to 9.65, p<0.001), use of violent method (OR=3.37, 95% CI 1.47 to 7.74, p=0.01), suicidal ideation (OR=3.57, 95% CI 1.40 to 9.07, p=0.01) and recent hospital discharge (OR=2.71, 95% CI 1.17 to 6.28, p=0.04). Multiple regression models predicted only 21.5% of the suicide outcome variance. Conclusions: Predicting suicide in schizophrenia is highly challenging due to the high prevalence of risk factors within this diagnostic group irrespective of outcome, including suicide. Nevertheless, older age at first contact with mental health services and lack of suicidal history and suicidal ideation are useful protective markers indicative of those less likely to end their own lives
Electrochemical Coupling of Biomass-derived Acids : New C8 Platforms for Renewable Polymers and Fuels
Electrolysis of biomass-derived carbonyl compounds is an alternative to condensation chemistry for supplying products with chain length >C6 for biofuel and renewable material production. Kolbe coupling of biomass-derived levulinic acid gives 2,7-octanedione, a new platform molecule only two low process-intensity steps removed from raw biomass. Hydrogenation to 2,7-octanediol provides a chiral secondary diol largely unknown to polymer chemistry, while intramolecular aldol condensation followed by hydrogenation yields branched cycloalkanes suitable for use as high-octane, cellulosic gasoline. Analogous electrolysis of an itaconic acid-derived methylsuccinic monoester gives chiral 2,5-dimethyladipic acid, another underutilized monomer due to lack of availability
New Physics in Bs -> J/psi phi: a General Analysis
Recently, the CDF and D0 collaborations measured indirect CP violation in Bs
-> J/psi phi and found a hint of a signal. If taken at face value, this can be
interpreted as a nonzero phase of Bs-Bsbar mixing (beta_s), in disagreement
with the standard model, which predicts that beta_s ~= 0. In this paper, we
argue that this analysis may be incomplete. In particular, there can be new
physics (NP) in the bbar -> sbar c cbar decay. If so, the value of beta_s is
different than for the case in which NP is assumed to be present only in the
mixing. We have examined several models of NP and found that, indeed, there can
be significant contributions to the decay. These effects are consistent with
measurements in B -> J/psi K* and Bd -> J/psi Ks. Due to the NP in the decay,
polarization-dependent indirect CP asymmetries and triple-product asymmetries
are predicted in Bs -> J/psi phi.Comment: 28 pages, JHEP, no figures. Considerable changes made. Abstract and
main text of paper modified to alter presentation. Appendix added. References
added. Conclusions unchanged
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Bridge-specific fragility analysis: when is it really necessary?
In seismic assessment of bridges the research focus has recently shifted on the derivation of bridge-specific fragility curves that account for the effect of different geometry, structural system, component and soil properties, on the seismic behaviour. In this context, a new, component-based methodology for the derivation of bridge-specific fragility curves has been recently proposed by the authors, with a view to overcoming the inherent difficulties in assessing all bridges of a road network and the drawbacks of existing methodologies, which use the same group of fragility curves for bridges within the same typological class. The main objective of this paper is to critically assess the necessity of bridge-specific fragility analysis, starting from the effect of structure-specific parameters on component capacity (limit state thresholds), seismic demand, and fragility curves. The aforementioned methodology is used to derive fragility curves for all bridges within an actual road network, with a view to investigating the consistency of adopting generic fragility curves for bridges that fall within the same class and quantifying the degree of over- or under-estimation of the probability of damage when generic bridge classes are considered. Moreover, fragility curves for all representative bridges of the analysed concrete bridge classes are presented to illustrate the differentiation in bridge fragility for varying structural systems, bridge geometry, total bridge length and maximum pier height. Based on the above, the relevance of bridge-specific fragility analysis is assessed, and pertinent conclusions are drawn
Evolution of spiral and scroll waves of excitation in a mathematical model of ischaemic border zone
Abnormal electrical activity from the boundaries of ischemic cardiac tissue
is recognized as one of the major causes in generation of ischemia-reperfusion
arrhythmias. Here we present theoretical analysis of the waves of electrical
activity that can rise on the boundary of cardiac cell network upon its
recovery from ischaemia-like conditions. The main factors included in our
analysis are macroscopic gradients of the cell-to-cell coupling and cell
excitability and microscopic heterogeneity of individual cells. The interplay
between these factors allows one to explain how spirals form, drift together
with the moving boundary, get transiently pinned to local inhomogeneities, and
finally penetrate into the bulk of the well-coupled tissue where they reach
macroscopic scale. The asymptotic theory of the drift of spiral and scroll
waves based on response functions provides explanation of the drifts involved
in this mechanism, with the exception of effects due to the discreteness of
cardiac tissue. In particular, this asymptotic theory allows an extrapolation
of 2D events into 3D, which has shown that cells within the border zone can
give rise to 3D analogues of spirals, the scroll waves. When and if such scroll
waves escape into a better coupled tissue, they are likely to collapse due to
the positive filament tension. However, our simulations have shown that such
collapse of newly generated scrolls is not inevitable and that under certain
conditions filament tension becomes negative, leading to scroll filaments to
expand and multiply leading to a fibrillation-like state within small areas of
cardiac tissue.Comment: 26 pages, 13 figures, appendix and 2 movies, as accepted to PLoS ONE
2011/08/0
Neutral Gauge Boson Contributions to the Dimuon Charge Asymmetry in B Decays
Recently, the D0 Collaboration measured the CP-violating like-sign dimuon
charge asymmetry in neutral B decays, finding a 3.2sigma difference from the
standard-model (SM) prediction. A non-SM charge asymmetry a_sl^s suggests a
new-physics (NP) contribution to Bs-Bsbar mixing. In this case, in order to
explain the measured value of a_sl^s within its 1sigma range, NP must be
present in Gamma_12^s, the absorptive part of the mixing. In this paper, we
examine whether such an explanation is possible in models with flavor-changing
Z (ZFCNC) or Z' (Z'FCNC) gauge bosons. The models must also reproduce the
measured values of the indirect CP asymmetry S_psi-phi in Bs -> J/psi phi, and
Delta Gamma_s, the Bs-Bsbar width difference. We find that the ZFCNC model
cannot reproduce the present measured values of S_psi-phi and a_sl^s within
their 1sigma ranges. On the other hand, in the Z'FCNC model, the values of all
three observables can be simultaneously reproduced.Comment: 18 pages, 7 figures, JHEP format. Some ZFCNC equations corrected,
ZFCNC analysis redone, references added, conclusions unchange
Is Our Universe Natural?
It goes without saying that we are stuck with the universe we have.
Nevertheless, we would like to go beyond simply describing our observed
universe, and try to understand why it is that way rather than some other way.
Physicists and cosmologists have been exploring increasingly ambitious ideas
that attempt to explain why certain features of our universe aren't as
surprising as they might first appear.Comment: Invited review for Nature, 11 page
A realistic pattern of fermion masses from a five-dimensional SO(10) model
We provide a unified description of fermion masses and mixing angles in the
framework of a supersymmetric grand unified SO(10) model with anarchic Yukawa
couplings of order unity. The space-time is five dimensional and the extra flat
spatial dimension is compactified on the orbifold ,
leading to Pati-Salam gauge symmetry on the boundary where Yukawa interactions
are localised. The gauge symmetry breaking is completed by means of a rather
economic scalar sector, avoiding the doublet-triplet splitting problem. The
matter fields live in the bulk and their massless modes get exponential
profiles, which naturally explain the mass hierarchy of the different fermion
generations. Quarks and leptons properties are naturally reproduced by a
mechanism, first proposed by Kitano and Li, that lifts the SO(10) degeneracy of
bulk masses in terms of a single parameter. The model provides a realistic
pattern of fermion masses and mixing angles for large values of . It
favours normally ordered neutrino mass spectrum with the lightest neutrino mass
below 0.01 eV and no preference for leptonic CP violating phases. The right
handed neutrino mass spectrum is very hierarchical and does not allow for
thermal leptogenesis. We analyse several variants of the basic framework and
find that the results concerning the fermion spectrum are remarkably stable.Comment: 30 pages, 7 figures, 4 table
Deficiency in origin licensing proteins impairs cilia formation: implications for the aetiology of meier-gorlin syndrome
Mutations in ORC1, ORC4, ORC6, CDT1, and CDC6, which encode proteins required for DNA replication origin licensing, cause Meier-Gorlin syndrome (MGS), a disorder conferring microcephaly, primordial dwarfism, underdeveloped ears, and skeletal abnormalities. Mutations in ATR, which also functions during replication, can cause Seckel syndrome, a clinically related disorder. These findings suggest that impaired DNA replication could underlie the developmental defects characteristic of these disorders. Here, we show that although origin licensing capacity is impaired in all patient cells with mutations in origin licensing component proteins, this does not correlate with the rate of progression through S phase. Thus, the replicative capacity in MGS patient cells does not correlate with clinical manifestation. However, ORC1-deficient cells from MGS patients and siRNA-mediated depletion of origin licensing proteins also have impaired centrosome and centriole copy number. As a novel and unexpected finding, we show that they also display a striking defect in the rate of formation of primary cilia. We demonstrate that this impacts sonic hedgehog signalling in ORC1-deficient primary fibroblasts. Additionally, reduced growth factor-dependent signaling via primary cilia affects the kinetics of cell cycle progression following cell cycle exit and re-entry, highlighting an unexpected mechanism whereby origin licensing components can influence cell cycle progression. Finally, using a cell-based model, we show that defects in cilia function impair chondroinduction. Our findings raise the possibility that a reduced efficiency in forming cilia could contribute to the clinical features of MGS, particularly the bone development abnormalities, and could provide a new dimension for considering developmental impacts of licensing deficiency
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