520 research outputs found
DBI Galileon and Late time acceleration of the universe
We consider 1+3 dimensional maximally symmetric Minkowski brane embedded in a
1+4 dimensional maximally symmetric Minkowski background. The resulting 1+3
dimensional effective field theory is of DBI (Dirac-Born-Infeld) Galileon type.
We use this model to study the late time acceleration of the universe. We study
the deviation of the model from the concordance \Lambda CDM behaviour. Finally
we put constraints on the model parameters using various observational data.Comment: 16 pages, 7 eps figures, Latex Style, new references added, corrected
missing reference
Galileons as Wess-Zumino Terms
We show that the galileons can be thought of as Wess-Zumino terms for the
spontaneous breaking of space-time symmetries. Wess-Zumino terms are terms
which are not captured by the coset construction for phenomenological
Lagrangians with broken symmetries. Rather they are, in d space-time
dimensions, d-form potentials for (d+1)-forms which are non-trivial co-cycles
in Lie algebra cohomology of the full symmetry group relative to the unbroken
symmetry group. We introduce the galileon algebras and construct the
non-trivial (d+1)-form co-cycles, showing that the presence of galileons and
multi-galileons in all dimensions is counted by the dimensions of particular
Lie algebra cohomology groups. We also discuss the DBI and conformal galileons
from this point of view, showing that they are not Wess-Zumino terms, with one
exception in each case.Comment: 49 pages. v2 minor changes, version appearing in JHE
Quantum corrections to generic branes: DBI, NLSM, and more
We study quantum corrections to hypersurfaces of dimension embedded
in generic higher-dimensional spacetimes. Manifest covariance is maintained
throughout the analysis and our methods are valid for arbitrary co-dimension
and arbitrary bulk metric. A variety of theories which are prominent in the
modern amplitude literature arise as special limits: the scalar sector of
Dirac-Born-Infeld theories and their multi-field variants, as well as generic
non-linear sigma models and extensions thereof. Our explicit one-loop results
unite the leading corrections of all such models under a single umbrella. In
contrast to naive computations which generate effective actions that appear to
violate the non-linear symmetries of their classical counterparts, our
efficient methods maintain manifest covariance at all stages and make the
symmetry properties of the quantum action clear. We provide an explicit
comparison between our compact construction and other approaches and
demonstrate the ultimate physical equivalence between the superficially
different results
Effect of Nenas honey supplementation on the oxidative status of undergraduate students
Honey is a dietary antioxidant as it contains phenolic compounds, such as flavonoids and phenolic acids. Antioxidants are non-nutritive, biologically active ingredients in food that reduce oxidative stress. The antioxidant content in each type of honey varies depending on its source. This study was aimed to determine the effect of Nenas honey supplementation on the oxidative status of a group of healthy medical students. They were divided into two groups; control (n=10) and supplemented (n=13), where 1 tablespoon of Nenas honey was given each day. Blood sampling was done at baseline, 1st and 2nd month of the study for determination of DNA damage and antioxidant enzyme activities, such as superoxide dismutase (SOD), glutathione peroxidise (GPx), and catalase (CAT). Results showed that Nenas honey increased the level of DNA damage at the 1st month but reduced it significantly at the 2nd month as compared to control. GPx and CAT activities also decreased significantly with honey supplementation throughout the study, though no changes were observed in SOD activity. Fasting glucose levels remained within the normal range with honey supplementation. In conclusion, Nenas honey decreases oxidative stress which leads to a reduction of antioxidant enzyme activities in the body
Body condition scoring of Bornean banteng in logged forests
© The Author(s) 2016. Background The Bornean banteng (Bos javanicus lowi) is an endangered subspecies that often inhabits logged forest; however very little is known about the effects of logging on their ecology, despite the differing effects this has on other ungulate species. A body condition scoring system was created for the Bornean banteng using camera trap photographs from five forests in Sabah, Malaysia, with various past and present management combinations to establish if banteng nutrition suffered as a result of forest disturbance. Results One hundred and eleven individuals were photographed over 38,009 camera trap nights from April 2011 to June 2014 in five forests. Banteng within forests that had a recent history of reduced-impact logging had higher body condition scores than banteng within conventionally logged forest. Conversely, when past logging was conducted using a conventional technique and the period of forest regeneration was relatively long; the banteng had higher body condition scores. Conclusion The body condition scoring system is appropriate for monitoring the long-term nutrition of the Bornean banteng and for evaluating the extent of the impact caused by present-day reduced-impact logging methods. Reduced-impact logging techniques give rise to individuals with the higher body condition scores in the shorter term, which then decline over time. In contrast the trend is opposite for conventional logging, which demonstrates the complex effects of logging on banteng body condition scores. This is likely to be due to differences in regeneration between forests that have been previously logged using differing methods
Massive Gravity on de Sitter and Unique Candidate for Partially Massless Gravity
We derive the decoupling limit of Massive Gravity on de Sitter in an
arbitrary number of space-time dimensions d. By embedding d-dimensional de
Sitter into d+1-dimensional Minkowski, we extract the physical helicity-1 and
helicity-0 polarizations of the graviton. The resulting decoupling theory is
similar to that obtained around Minkowski. We take great care at exploring the
partially massless limit and define the unique fully non-linear candidate
theory that is free of the helicity-0 mode in the decoupling limit, and which
therefore propagates only four degrees of freedom in four dimensions. In the
latter situation, we show that a new Vainshtein mechanism is at work in the
limit m^2\to 2 H^2 which decouples the helicity-0 mode when the parameters are
different from that of partially massless gravity. As a result, there is no
discontinuity between massive gravity and its partially massless limit, just in
the same way as there is no discontinuity in the massless limit of massive
gravity. The usual bounds on the graviton mass could therefore equivalently
well be interpreted as bounds on m^2-2H^2. When dealing with the exact
partially massless parameters, on the other hand, the symmetry at m^2=2H^2
imposes a specific constraint on matter. As a result the helicity-0 mode
decouples without even the need of any Vainshtein mechanism.Comment: 30 pages. Some clarifications and references added. New subsection
'Symmetry and Counting in the Full Theory' added. New appendix 'St\"uckelberg
fields in the Na\"ive approach' added. Matches version published in JCA
Anthropometrically determined nutritional status of urban primary schoolchildren in Makurdi, Nigeria
<p>Abstract</p> <p>Background</p> <p>No information exists on the nutritional status of primary school children residing in Makurdi, Nigeria. It is envisaged that the data could serve as baseline data for future studies, as well as inform public health policy. The aim of this study was to assess the prevalence of malnutrition among urban school children in Makurdi, Nigeria.</p> <p>Methods</p> <p>Height and weight of 2015 (979 boys and 1036 girls), aged 9-12 years, attending public primary school in Makurdi were measured and the body mass index (BMI) calculated. Anthropometric indices of weight-for-age (WA) and height-for-age (HA) were used to estimate the children's nutritional status. The BMI thinness classification was also calculated.</p> <p>Results</p> <p>Underweight (WAZ < -2) and stunting (HAZ < -2) occurred in 43.4% and 52.7%, respectively. WAZ and HAZ mean scores of the children were -0.91(SD = 0.43) and -0.83 (SD = 0.54), respectively. Boys were more underweight (48.8%) than girls (38.5%), and the difference was statistically significant (p = 0.024; p < 0.05). Conversely, girls tend to be more stunted (56.8%) compared to boys (48.4%) (p = 0.004; p < 0.05). Normal WAZ and HAZ occurred in 54.6% and 44.2% of the children, respectively. Using the 2007 World Health Organisation BMI thinness classification, majority of the children exhibited Grade 1 thinness (77.3%), which was predominant at all ages (9-12 years) in both boys and girls. Gender wise, 79.8% boys and 75.0% girls fall within the Grade I thinness category. Based on the WHO classification, severe malnutrition occurred in 31.3% of the children.</p> <p>Conclusions</p> <p>There is severe malnutrition among the school children living in Makurdi. Most of the children are underweight, stunted and thinned. As such, providing community education on environmental sanitation and personal hygienic practices, proper child rearing, breast-feeding and weaning practices would possibly reverse the trends.</p
Interacting Spin-2 Fields
We construct consistent theories of multiple interacting spin-2 fields in
arbitrary spacetime dimensions using a vielbein formulation. We show that these
theories have the additional primary constraints needed to eliminate potential
ghosts, to all orders in the fields, and to all orders beyond any decoupling
limit. We postulate that the number of spin-2 fields interacting at a single
vertex is limited by the number of spacetime dimensions. We then show that, for
the case of two spin-2 fields, the vielbein theory is equivalent to the
recently proposed theories of ghost-free massive gravity and bi-metric gravity.
The vielbein formulation greatly simplifies the proof that these theories have
an extra primary constraint which eliminates the Boulware-Deser ghost.Comment: 42 pages, 3 figures. v3 alternative argument using constrained
spatial vielbeins has been removed (see footnote 3
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