1,683 research outputs found
Phenomenology of the Equivalence Principle with Light Scalars
Light scalar particles with couplings of sub-gravitational strength, which
can generically be called 'dilatons', can produce violations of the equivalence
principle. However, in order to understand experimental sensitivities one must
know the coupling of these scalars to atomic systems. We report here on a study
of the required couplings. We give a general Lagrangian with five independent
dilaton parameters and calculate the "dilaton charge" of atomic systems for
each of these. Two combinations are particularly important. One is due to the
variations in the nuclear binding energy, with a sensitivity scaling with the
atomic number as . The other is due to electromagnetism. We compare
limits on the dilaton parameters from existing experiments.Comment: 5 page
How blebs and pseudopods cooperate during chemotaxis
Two motors can drive extension of the leading edge of motile cells: actin polymerization and myosin-driven contraction of the cortex, producing fluid pressure and the formation of blebs. Dictyostelium cells can move with both blebs and actin-driven pseudopods at the same time, and blebs, like pseudopods, can be orientated by chemotactic gradients. Here we ask how bleb sites are selected and how the two forms of projection cooperate. We show that membrane curvature is an important, yet overlooked, factor. Dictyostelium cells were observed moving under agarose, which efficiently induces blebbing, and the dynamics of membrane deformations were analyzed. Blebs preferentially originate from negatively curved regions, generated on the flanks of either extending pseudopods or blebs themselves. This is true of cells at different developmental stages, chemotaxing to either folate or cyclic AMP and moving with both blebs and pseudopods or with blebs only. A physical model of blebbing suggests that detachment of the cell membrane is facilitated in concave areas of the cell, where membrane tension produces an outward directed force, as opposed to pulling inward in convex regions. Our findings assign a role to membrane tension in spatially coupling blebs and pseudopods, thus contributing to clustering protrusions to the cell front
Toward a predictive understanding of Earthâs microbiomes to address 21st century challenges
© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in mBio 7 (2016): e00714-16, doi:10.1128/mBio.00714-16.Microorganisms have shaped our planet and its inhabitants for over 3.5 billion years. Humankind has had a profound influence on the biosphere, manifested as global climate and land use changes, and extensive urbanization in response to a growing population. The challenges we face to supply food, energy, and clean water while maintaining and improving the health of our population and ecosystems are significant. Given the extensive influence of microorganisms across our biosphere, we propose that a coordinated, cross-disciplinary effort is required to understand, predict, and harness microbiome function. From the parallelization of gene function testing to precision manipulation of genes, communities, and model ecosystems and development of novel analytical and simulation approaches, we outline strategies to move microbiome research into an era of causality. These efforts will improve prediction of ecosystem response and enable the development of new, responsible, microbiome-based solutions to significant challenges of our time.E.L.B. is supported by the Genomes-to-Watersheds Subsurface Biogeochemical
Research Scientific Focus Area, and T.R.N. is supported by
ENIGMA-Ecosystems and Networks Integrated with Genes and Molecular
Assemblies (http://enigma.lbl.gov) Scientific Focus Area, funded by
the U.S. Department of Energy (US DOE), Office of Science, Office of
Biological and Environmental Research under contract no. DE-AC02-
05CH11231 to Lawrence Berkeley National Laboratory (LBNL). M.E.M.
is also supported by the US DOE, Office of Science, Office of Biological
and Environmental Research under contract no. DE-AC02-05CH11231.
Z.G.C. is supported by National Science Foundation Integrative Organismal
Systems grant #1355085, and by US DOE, Office of Biological and
Environmental Research grant # DE-SC0008182 ER65389 from the Terrestrial
Ecosystem Science Program. M.J.B. is supported by R01 DK
090989 from the NIH. T.J.D. is supported by the US DOE Office of Scienceâs
Great Lakes Bioenergy Research Center, grant DE-FC02-
07ER64494. J.L.G. is supported by Alfred P. Sloan Foundation G 2-15-14023. R.K. is supported by grants from the NSF (DBI-1565057) and
NIH (U01AI24316, U19AI113048, P01DK078669, 1U54DE023789,
U01HG006537). K.S.P. is supported by grants from the NSF DMS-
1069303 and the Gordon & Betty Moore Foundation (#3300)
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 2.3â3.8)
and was stronger when blood samples for
H pylori serology were collected 10+ years
before cancer diagnosis (5.9; 3.4â10.3). H
pylori infection was not associated with an
altered overall risk of cardia cancer (1.0;
0.7â1.4).
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
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Probiotics, prebiotics, and the host microbiome: the science of translation
Recent advances in our understanding of the community structure and function of the human microbiome have implications for the potential role of probiotics and prebiotics in promoting human health. A group of experts recently met to review the latest advances in microbiota/microbiome research and discuss the implications for development of probiotics and prebiotics, primarily as they relate to effects mediated via the intestine. The goals of the meeting were to share recent advances in research on the microbiota, microbiome, probiotics, and prebiotics, and to discuss these findings in the contexts of regulatory barriers, evolving healthcare environments, and potential effects on a variety of health topics, including the development of obesity and diabetes; the long-term consequences of exposure to antibiotics early in life to the gastrointestinal (GI) microbiota; lactose intolerance; and the relationship between the GI microbiota and the central nervous system, with implications for depression, cognition, satiety, and mental health for people living in developed and developing countries. This report provides an overview of these discussions
Human Impacts on Forest Biodiversity in Protected Walnut-Fruit Forests in Kyrgyzstan
We used a spatially explicit model of forest dynamics, supported by empirical field data and socioeconomic data, to examine the impacts of human disturbances on a protected forest landscape in Kyrgyzstan. Local use of 27 fruit and nut species was recorded and modeled. Results indicated that in the presence of fuelwood cutting with or without grazing, species of high socioeconomic impor- tance such as Juglans regia, Malus spp., and Armeniaca vulgaris were largely eliminated from the landscape after 50â150 yr. In the absence of disturbance or in the presence of grazing only, decline of these species occurred at a much lower rate, owing to competi- tive interactions between tree species. This suggests that the current intensity of fuelwood harvesting is not sustainable. Conversely, cur- rent grazing intensities were found to have relatively little impact on forest structure and composition, and could potentially play a positive role in supporting regeneration of tree species. These results indicate that both positive and negative impacts on biodiversity can arise from human populations living within a protected area. Potentially, these could be reconciled through the development of participatory approaches to conservation management within this reserve, to ensure the maintenance of its high conservation value while meeting human needs
A minimum estimate for the incidence of gastric cancer in Eastern Kenya
We documented available information concerning incident cases of gastric cancer in part of Kenya's Eastern Province between 1991 and 1993. By reviewing the records of all major health facilities in the area, 200 cases of gastric carcinoma were found giving an annual average crude incidence rate of 7.01 per 100â000 males and 3.7 for females (world age-standardised rates, 14.3 for males and 7.1 for females). There is likely to be underascertainment of cases especially among those aged over 65 years. Previous incidence estimates for the same area of Kenya were reviewed and a 10-fold increase in the recorded indirectly standardised incidence rate between the periods 1965â70 and 1991â93 was noted but this may be due to improved diagnostic facilities. The recent rates in this part of Kenya are comparable to Eastern European rates and similar to those recorded in other highland regions of Africa. © 2001 Cancer Research Campaig
Elucidating the aetiology of human Campylobacter coli infections
Peer reviewedPublisher PD
Extracting invariant characteristics of sketch maps: Towards place query-by-sketch
In geography, invariant aspects of sketches are essential to study because they reflect the human perception of real-world places. A person's perception of a place can be ex-pressed in sketches. In this article, we quantitatively and qualitatively analyzed the characteristics of single objects and characteristics among objects in sketches and the real world to find reliable invariants that can be used to establish references/correspondences between sketch and world in a matching process. These characteristics include category, shape, name, and relative size of each object. Moreover, quantity and spatial relationshipsâsuch as topological, or-dering, and location relationshipsâamong all objects are also analyzed to assess consistency between sketched and actual places. The approach presented in this study extracts the reliable invariants for query-by-sketch and prioritizes their relevance for a sketch-map matching process
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