870 research outputs found
Population strategies to decrease sodium intake : a global cost-effectiveness analysis
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Political Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 69-77).Excessive sodium consumption is both prevalent and very costly in many countries around the world. Recent research has found that more than 90% of the world's adult population live in countries with mean intakes exceeding the World Health Organization's recommendation, and that more than a million deaths every year may be attributable to excess sodium. This study uses a simulation model to estimate, for the first time, the cost-effectiveness of government interventions to reduce population sodium consumption in every country in the world. It reveals substantial heterogeneity in cost-effectiveness by country that has never before been identified, and illustrates, also for the first time, the sensitivity of intervention efficacy to the theoretical-minimum-risk exposure distribution of sodium intake. The study makes a number of additional contributions. It offers a comprehensive appraisal of the methodological strengths and limitations of the surveys, imputation models, randomized controlled trials, prospective cohort studies, meta-analyses, and simulation models that together constitute the evidence base for public health recommendations on sodium intake, as well as for this study's own analysis. These methodological issues, some raised for the first time, are evaluated systematically to allow the relative quality of each input to be assessed and to inform prioritization of further research. The study also uses economic theory to ground a discussion of the proper nature and scope of government policies targeting population sodium consumption, and presents an up-to-date survey of sodium reduction initiatives around the world.by Michael William Webb.S.M
Dark Energy and Neutrino Mass Limits from Baryogenesis
In this brief report we consider couplings of the dark energy scalar, such as
Quintessence to the neutrinos and discuss its implications in studies on the
neutrino mass limits from Baryogenesis. During the evolution of the dark energy
scalar, the neutrino masses vary, consequently the bounds on the neutrino
masses we have here differ from those obtained before.Comment: 5 pages,3 figures. Version accepted for publication in Phys. Rev.
Time Variations in the Scale of Grand Unification
We study the consequences of time variations in the scale of grand
unification, , when the Planck scale and the value of the unified coupling
at the Planck scale are held fixed. We show that the relation between the
variations of the low energy gauge couplings is highly model dependent. It is
even possible, in principle, that the electromagnetic coupling varies,
but the strong coupling does not (to leading approximation). We
investigate whether the interpretation of recent observations of quasar
absorption lines in terms of time variation in can be accounted for by
time variation in . Our formalism can be applied to any scenario where a
time variation in an intermediate scale induces, through threshold corrections,
time variations in the effective low scale couplings.Comment: 14 pages, revtex4; Updated observational results and improved
statistical analysis (section IV); added reference
Chaotic scalar fields as models for dark energy
We consider stochastically quantized self-interacting scalar fields as
suitable models to generate dark energy in the universe. Second quantization
effects lead to new and unexpected phenomena is the self interaction strength
is strong. The stochastically quantized dynamics can degenerate to a chaotic
dynamics conjugated to a Bernoulli shift in fictitious time, and the right
amount of vacuum energy density can be generated without fine tuning. It is
numerically observed that the scalar field dynamics distinguishes fundamental
parameters such as the electroweak and strong coupling constants as
corresponding to local minima in the dark energy landscape. Chaotic fields can
offer possible solutions to the cosmological coincidence problem, as well as to
the problem of uniqueness of vacua.Comment: 30 pages, 3 figures. Replaced by final version accepted by Phys. Rev.
Primordial Nucleosynthesis as a Test of the Friedmann Equation in the Early Universe
In the standard hot big bang model, the expansion of the early universe is
given by the Friedmann equation with an energy density dominated by
relativistic particles. Since in a variety of models this equation is altered,
we introduce modifications in the Friedmann equation and show that we can
constrain them using big bang nucleosynthesis data. When there is no
neutrino/antineutrino asymmetry these modifications are tightly bounded but in
presence of an asymmetry the bounds become much looser. As an illustration, we
apply our results to a model where the second and third families couple to
gravity differently than the first family (non-universal gravity).Comment: 6 figures. Revised version. Matches with the accepted one for
publication in PR
Gastric cancer and Helicobacter pylori: a combined analysis of 12 case control studies nested within prospective cohorts
BACKGROUND: The magnitude of the association
between Helicobacter pylori and
incidence of gastric cancer is unclear. H
pylori infection and the circulating antibody
response can be lost with development
of cancer; thus retrospective studies
are subject to bias resulting from classifi-
cation of cases as H pylori negative when
they were infected in the past.
AIMS: To combine data from all case control
studies nested within prospective
cohorts to assess more reliably the relative
risk of gastric cancer associated with H
pylori infection.To investigate variation in
relative risk by age, sex, cancer type and
subsite, and interval between blood sampling
and cancer diagnosis.
METHODS: Studies were eligible if blood
samples for H pylori serology were collected
before diagnosis of gastric cancer in
cases. Identified published studies and two
unpublished studies were included. Individual
subject data were obtained for
each. Matched odds ratios (ORs) and 95%
confidence intervals (95% CI) were calculated
for the association between H pylori
and gastric cancer.
RESULTS: Twelve studies with 1228 gastric
cancer cases were considered. The association
with H pylori was restricted to noncardia
cancers (OR 3.0; 95% CI 2.3–3.8)
and was stronger when blood samples for
H pylori serology were collected 10+ years
before cancer diagnosis (5.9; 3.4–10.3). H
pylori infection was not associated with an
altered overall risk of cardia cancer (1.0;
0.7–1.4).
CONCLUSIONS: These results suggest that
5.9 is the best estimate of the relative risk
of non-cardia cancer associated with H
pylori infection and that H pylori does not
increase the risk of cardia cancer. They
also support the idea that when H pylori
status is assessed close to cancer diagnosis,
the magnitude of the non-cardia
association may be underestimated
Mutational analysis of human CEACAM1: the potential of receptor polymorphism in increasing host susceptibility to bacterial infection
A common overlapping site on the N-terminal IgV-like domain of human carcinoembryonic antigen (CEA)-related cell adhesion molecules (CEACAMs) is targeted by several important human respiratory pathogens. These include Neisseria meningitidis (Nm) and Haemophilus influenzae (Hi) that can cause disseminated or persistent localized infections. To define the precise structural features that determine the binding of distinct pathogens with CEACAMs, we have undertaken molecular modelling and mutation of the receptor molecules at previously implicated key target residues required for bacterial binding. These include Ser-32, Tyr-34, Val-39, Gln-44 and Gln-89, in addition to Ile-91, the primary docking site for the pathogens. Most, but not all, of these residues located adjacent to each other in a previous N-domain model of human CEACAM1, which was based on REI, CD2 and CD4. In the current studies, we have refined this model based on the mouse CEACAM1 crystal structure, and observe that all of the above residues form an exposed continuous binding region on the N-domain. Examination of the model also suggested that substitution of two of these residues 34 and 89 could affect the accessibility of Ile-91 for ligand binding. By introducing selected mutations at the positions 91, 34 and 89, we confirmed the primary importance of Ile-91 in all bacterial binding to CEACAM1 despite the inter- and intraspecies structural differences between the bacterial CEACAM-binding ligands. The studies further indicated that the efficiency of binding was significantly enhanced for specific strains by mutations such as Y34F and Q89N, which also altered the hierarchy of Nm versus Hi strain binding. These studies imply that distinct polymorphisms in human epithelial CEACAMs have the potential to decrease or increase the risk of infection by the receptor-targeting pathogens
Quantifying heterogeneous responses of fish community size structure using novel combined statistical techniques
To understand changes in ecosystems, the appropriate scale at which to study them must be determined. Large marine ecosystems (LMEs) cover thousands of square kilometres and are a useful classification scheme for ecosystem monitoring and assessment. However, averaging across LMEs may obscure intricate dynamics within. The purpose of this study is to mathematically determine local and regional patterns of ecological change within an LME using empirical orthogonal functions (EOFs). After using EOFs to define regions with distinct patterns of change, a statistical model originating from control theory is applied (Nonlinear AutoRegressive Moving Average with eXogenous input – NARMAX) to assess potential drivers of change within these regions. We have selected spatial data sets (0.5° latitude × 1°longitude) of fish abundance from North Sea fisheries research surveys (spanning 1980–2008) as well as of temperature, oxygen, net primary production and a fishing pressure proxy, to which we apply the EOF and NARMAX methods. Two regions showed significant changes since 1980: the central North Sea displayed a decrease in community size structure which the NARMAX model suggested was linked to changes in fishing; and the Norwegian trench region displayed an increase in community size structure which, as indicated by NARMAX results, was primarily linked to changes in sea-bottom temperature. These regions were compared to an area of no change along the eastern Scottish coast where the model determined the community size structure was most strongly associated to net primary production. This study highlights the multifaceted effects of environmental change and fishing pressures in different regions of the North Sea. Furthermore, by highlighting this spatial heterogeneity in community size structure change, important local spatial dynamics are often overlooked when the North Sea is considered as a broad-scale, homogeneous ecosystem (as normally is the case within the political Marine Strategy Framework Directive)
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