313 research outputs found
Placental blood transfusion in newborn babies reaches a plateau after 140 s: Further analysis of longitudinal survey of weight change
Get PDFObjective: With the introduction of active management of the third stage of labour in the 1960s, it became usual practice to clamp and cut the umbilical cord immediately following birth. The timing of this cord clamping is controversial, as blood may beneficially be transferred to the baby if clamping of the cord is delayed slightly. There is no agreement, however, on how long the delay should be before clamping the cord. This study aimed to establish when blood ceased to flow in the umbilical cord to determine how long to delay clamping of the umbilical cord following delivery of the term newborn to maximise placental transfusion. Methods: This observational study collected longitudinal weight measurements set in a hospital labour ward. A total of 26 mothers at term and their singleton babies participated in the study. In this reanalysis, the velocity of weight change over the first minutes of life determined by functional data analysis was estimated. Results: We found that the flow velocity in the umbilical cord was on average 0 at 125 s after placing the baby on the scales, which was typically 140 s after birth. Conclusions: To maximise placental transfusion, cord clamping should be delayed for at least 140 s following birth of the baby
An ecological approach to problems of Dark Energy, Dark Matter, MOND and Neutrinos
Full text linkModern astronomical data on galaxy and cosmological scales have revealed
powerfully the existence of certain dark sectors of fundamental physics, i.e.,
existence of particles and fields outside the standard models and inaccessible
by current experiments. Various approaches are taken to modify/extend the
standard models. Generic theories introduce multiple de-coupled fields A, B, C,
each responsible for the effects of DM (cold supersymmetric particles), DE
(Dark Energy) effect, and MG (Modified Gravity) effect respectively. Some
theories use adopt vanilla combinations like AB, BC, or CA, and assume A, B, C
belong to decoupled sectors of physics. MOND-like MG and Cold DM are often
taken as opposite frameworks, e.g. in the debate around the Bullet Cluster.
Here we argue that these ad hoc divisions of sectors miss important clues from
the data. The data actually suggest that the physics of all dark sectors is
likely linked together by a self-interacting oscillating field, which governs a
chameleon-like dark fluid, appearing as DM, DE and MG in different settings. It
is timely to consider an interdisciplinary approach across all semantic
boundaries of dark sectors, treating the dark stress as one identity, hence
accounts for several "coincidences" naturally.Comment: 12p, Proceedings to the 6-th Int. Conf. of Gravitation and Cosmology.
Neutrino section expande
Diagnosing Spin at the LHC via Vector Boson Fusion
Get PDFWe propose a new technique for determining the spin of new massive particles
that might be discovered at the Large Hadron Collider. The method relies on
pair-production of the new particles in a kinematic regime where the vector
boson fusion production mechanism is enhanced. For this regime, we show that
the distribution of the leading jets as a function of their relative azimuthal
angle can be used to distinguish spin-0 from spin-1/2 particles. We illustrate
this effect by considering the particular cases of (i) strongly-interacting,
stable particles and (ii) supersymmetric particles carrying color charge. We
argue that this method should be applicable in a wide range of new physics
scenarios.Comment: 5 pages, 4 figure
Limit on the mass of a long-lived or stable gluino
Full text linkWe reinterpret the generic CDF charged massive particle limit to obtain a
limit on the mass of a stable or long-lived gluino. Various sources of
uncertainty are examined. The -hadron spectrum and scattering cross sections
are modeled based on known low-energy hadron physics and the resultant
uncertainties are quantified and found to be small compared to uncertainties
from the scale dependence of the NLO pQCD production cross sections. The
largest uncertainty in the limit comes from the unknown squark mass: when the
squark -- gluino mass splitting is small, we obtain a gluino mass limit of 407
GeV, while in the limit of heavy squarks the gluino mass limit is 397 GeV. For
arbitrary (degenerate) squark masses, we obtain a lower limit of 322 GeV on the
gluino mass. These limits apply for any gluino lifetime longer than
ns, and are the most stringent limits for such a long-lived or stable gluino.Comment: 15 pages, 5 figures, accepted for publication in JHE
The Universal Real Projective Plane: LHC phenomenology at one Loop
Full text linkThe Real Projective Plane is the lowest dimensional orbifold which, when
combined with the usual Minkowski space-time, gives rise to a unique model in
six flat dimensions possessing an exact Kaluza Klein (KK) parity as a relic
symmetry of the broken six dimensional Lorentz group. As a consequence of this
property, any model formulated on this background will include a stable Dark
Matter candidate. Loop corrections play a crucial role because they remove mass
degeneracy in the tiers of KK modes and induce new couplings which mediate
decays. We study the full one loop structure of the corrections by means of
counter-terms localised on the two singular points. As an application, the
phenomenology of the (2,0) and (0,2) tiers is discussed at the LHC. We identify
promising signatures with single and di-lepton, top antitop and 4 tops: in the
dilepton channel, present data from CMS and ATLAS may already exclude KK masses
up to 250 GeV, while by next year they may cover the whole mass range preferred
by WMAP data.Comment: 45 pages, 3 figure
Dirac Leptogenesis with a Non-anomalous Family Symmetry
Full text linkWe propose a model for Dirac leptogenesis based on a non-anomalous
gauged family symmetry. The anomaly cancellation conditions are
satisfied with no new chiral fermions other than the three right-handed
neutrinos, giving rise to stringent constraints among the charges. Realistic
masses and mixing angles are obtained for all fermions. The model predicts
neutrinos of the Dirac type with naturally suppressed masses. Dirac
leptogenesis is achieved through the decay of the flavon fields. The cascade
decays of the vector-like heavy fermions in the Froggatt-Nielsen mechanism play
a crucial role in the separation of the primodial lepton numbers. We find that
a large region of parameter space of the model gives rise to a sufficient
cosmological baryon number asymmetry through Dirac leptogenesis.Comment: 8 pages, 8 figures, version to appear in JHE
Estimating the number needed to treat from continuous outcomes in randomised controlled trials: methodological challenges and worked example using data from the UK Back Pain Exercise and Manipulation (BEAM) trial
Get PDFBackground
Reporting numbers needed to treat (NNT) improves interpretability of trial results. It is unusual that continuous outcomes are converted to numbers of individual responders to treatment (i.e., those who reach a particular threshold of change); and deteriorations prevented are only rarely considered. We consider how numbers needed to treat can be derived from continuous outcomes; illustrated with a worked example showing the methods and challenges.
Methods
We used data from the UK BEAM trial (n = 1, 334) of physical treatments for back pain; originally reported as showing, at best, small to moderate benefits. Participants were randomised to receive 'best care' in general practice, the comparator treatment, or one of three manual and/or exercise treatments: 'best care' plus manipulation, exercise, or manipulation followed by exercise. We used established consensus thresholds for improvement in Roland-Morris disability questionnaire scores at three and twelve months to derive NNTs for improvements and for benefits (improvements gained+deteriorations prevented).
Results
At three months, NNT estimates ranged from 5.1 (95% CI 3.4 to 10.7) to 9.0 (5.0 to 45.5) for exercise, 5.0 (3.4 to 9.8) to 5.4 (3.8 to 9.9) for manipulation, and 3.3 (2.5 to 4.9) to 4.8 (3.5 to 7.8) for manipulation followed by exercise. Corresponding between-group mean differences in the Roland-Morris disability questionnaire were 1.6 (0.8 to 2.3), 1.4 (0.6 to 2.1), and 1.9 (1.2 to 2.6) points.
Conclusion
In contrast to small mean differences originally reported, NNTs were small and could be attractive to clinicians, patients, and purchasers. NNTs can aid the interpretation of results of trials using continuous outcomes. Where possible, these should be reported alongside mean differences. Challenges remain in calculating NNTs for some continuous outcomes
Higgs and non-universal gaugino masses: no SUSY signal expected yet?
Get PDFSo far, no supersymmetric particles have been detected at the Large Hadron
Collider (LHC). However, the recent Higgs results have interesting implications
for the SUSY parameter space. In this paper, we study the consequences of an
LHC Higgs signal for a model with non-universal gaugino masses in the context
of SU(5) unification. The gaugino mass ratios associated with the higher
representations produce viable spectra that are largely inaccessible to the
current LHC and direct dark matter detection experiments. Thus, in light of the
Higgs results, the non-observation of SUSY is no surprise.Comment: supplementary file containing plots with log priors in ancillary
files. v2: added some comments on more general settings and references,
accepted for publication in JHE
The Curious Adventure of the Ultrahigh Energy Cosmic Rays
Get PDFThese lectures discuss the mysteries involving the production and
extragalactic propagation of ultrahigh energy cosmic rays and suggested
possible solutions.Comment: Lectures given at the D. Chalonge Euroschool, Erice, Italy, November
2000, 25 pages, 7 ps figs., expanded revision with color fig.
The Full Two-Loop R-parity Violating Renormalization Group Equations for All Minimal Supersymmetric Standard Model Couplings
Full text linkWe present the full two-loop -functions for the minimal supersymmetric
standard model couplings, extended to include R-parity violating couplings
through explicit R-parity violation
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