994 research outputs found
Relativistic two-pion exchange nucleon-nucleon potential: configuration space
We have recently performed a relativistic chiral expansion of the
two-pion exchange potential, and here we explore its configuration space
content. Interactions are determined by three families of diagrams, two of
which involve just and , whereas the third one depends on
empirical coefficients fixed by subthreshold data. In this sense, the
calculation has no adjusted parameters and gives rise to predictions, which are
tested against phenomenological potentials. The dynamical structure of the
eight leading non-relativistic components of the interaction is investigated
and, in most cases, found to be clearly dominated by a well defined class of
diagrams. In particular, the central isovector and spin-orbit, spin-spin, and
tensor isoscalar terms are almost completely fixed by just and .
The convergence of the chiral series in powers of the ratio (pion mass/nucleon
mass) is studied as a function of the internucleon distance and, for 1 fm,
found to be adequate for most components of the potential. An important
exception is the dominant central isoscalar term, where the convergence is
evident only for 2.5 fm. Finally, we compare the spatial behavior of the
functions that enter the relativistic and heavy baryon formulations of the
interaction and find that, in the region of physical interest, they differ by
about 5%.Comment: 27 pages, 33 figure
Recent advances in the theory of nuclear forces
After a brief historical review, we present recent progress in our
understanding of nuclear forces in terms of chiral effective field theory.Comment: 6 pages, 2 figures; talk at International Symposium on Correlations
Dynamics in Nuclei, University of Tokyo, Japan, 31 January-4 February, 200
Efeito do aquecimento global sobre a comunidade microbiana do solo.
A relação entre as comunidades microbianas do solo e o aquecimento global pode ser vista de duas formas. Na primeira, os microrganismos contribuem para a emissão de gases de efeito estufa, sendo os principais atores nos processos de ciclagem de nutrientes e de fluxos globais de CO2, CH4 e N2. Na segunda, é importante entender como o aquecimento global, resultado das mudanças climáticas, afeta a comunidade microbiana do solo. Considerando que a elevação do CO2, temperatura e precipitação são fatores importantes que influenciam as comunidades do solo, neste capítulo serão discutidos seus efeitos na comunidade microbiana do solo de forma geral e nos patógenos existentes nos solos no contexto do aquecimento global
Entropic Entanglement Criteria for Continuous Variables
We derive several entanglement criteria for bipartite continuous variable
quantum systems based on the Shannon entropy. These criteria are more sensitive
than those involving only second-order moments, and are equivalent to
well-known variance product tests in the case of Gaussian states. Furthermore,
they involve only a pair of quadrature measurements, and will thus should prove
extremely useful the experimental identification of entanglement.Comment: 4 pages, 2 figure
Effects from inhomogeneities in the chiral transition
We consider an approximation procedure to evaluate the finite-temperature
one-loop fermionic density in the presence of a chiral background field which
systematically incorporates effects from inhomogeneities in the chiral field
through a derivative expansion. We apply the method to the case of a simple
low-energy effective chiral model which is commonly used in the study of the
chiral phase transition, the linear sigma-model coupled to quarks. The
modifications in the effective potential and their consequences for the bubble
nucleation process are discussed.Comment: 11 pages, 5 figures. v2: appendix and references added, published
versio
Editorial: Advancements in the Understanding of Anthropogenic Impacts on the Microbial Ecology and Function of Aquatic Environments
Aquatic environments are important ecosystems providing multiple services to humankind and directly affecting economic income worldwide. These ecosystems have increasingly been threatened by changes in global climate and diverse anthropogenic activities—from agriculture to industry (Häder et al., 2020). In general, the continuous exploitation of aquatic ecosystems has caused severe impacts on biological diversity despite some efforts to control habitat exploitation via local legislation (Popper et al., 2020). For instance, the leaching of pollutants and chemical hazards, the eutrophisation caused by extensive use of chemicals in agriculture and aquaculture, changes in land use, and the disposal of urban wastes; are the major factors responsible for most of the anthropogenic impacts on these ecosystems worldwide (Cotta et al., 2019). As such, properly monitoring the effects of these human activities is critical to aid the early detection of potential chemicals and activities with large impacts in aquatic ecosystems. Besides, advances in ecological research can provide the basis for developing new strategies of remediation and recovery of impacted systems (Taketani et al., 2010)
Rizobactérias halotolerantes/halofílicas isoladas de plantas halofílicas pioneiras de salinas do semiárido brasileiro.
Rhizosphere microbial community manipulation under salted soil by the inoculation of Pseudomonas sp CMAA 1215 in Zea mays.
Soil salinity reduces the soil organic carbon stock, the microbial biomass and activity and modifies the biogeochemical cycle and the microbial diversity. Osmotic stress caused by ethylene on plants can be reduced using 1-aminocyclopropane-1-carboxylate (ACC) deaminase plant growth promoting bacteria (PGPR) producers. Studies of PGPR and commercially strains are based only on the growth of the plant without concern about modification of the microbial community. This scenario has shown an increasing need to study the ecological functions of bacterial community on salted soil and to develop new technologies to reduce environmental impacts and waste of natural resources. Our aim was to study the influence of the Pseudomonas sp. CMAA1215, a known ACC deaminase on rhizosphere bacteria community of Zea mays under saline soil by sequencing the rhizosphere metagenome. The NMDS of the OTU table (ANOSIM p<0.01) discriminate all the treatments (with and without inoculation under salted and non-salted soils) indicating a modification of the bacteria community by inoculation or by soil salinization. The main groups of the rhizosphere that had the abundance increased by Pseudomonas inoculation were Acidobacteriales, Solibacteriales, Bacillales and Rhizobiales. The relative abundance of Rhodospirillales (Alphaproteobacteria) and Chthoniobacterales (Spartobacteria) was stimulated by the inoculation only under higher salinization. The inoculation can be important to stimulate other PGPR under saline soil or microbes that are not benefic to plants
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