203 research outputs found
Stressed, but not defenceless: no obvious influence of irradiation levels on antifeeding and antifouling defences of tropical macroalgae
The production of defence metabolites is assumed to be costly in metabolic terms. If this holds true, low-light stress should reduce the ability of seaweeds to defend themselves chemically against herbivory and fouling. We investigated the effect of energy limitation on the defensive status of seaweeds by assessing their attractiveness to mesograzers and their activity against a bivalve macrofouler in comparison with non-stressed conspecifics. The macroalgae Codium decorticatum (Woodw.) M. Howe, Osmundaria obtusiloba (C. Agardh) R. E. Norris, Pterocladiella capillacea (S. G. Gmel.) Santel. and Hommer., Sargassum vulgare C. Agardh and Stypopodium zonale (Lamour.) Papenf. collected at the southeastern Brazilian coast were exposed to six levels of irradiation (between 1 and 180 μmol photons m−2 s−1) for 10–14 days. After this period, algae from all treatment levels were: (a) processed as artificial food and offered to an amphipod community dominated by Elasmopus brasiliensis Dana and (b) extracted to test for differences in settlement rates of the fouling mussel Perna perna L. on filter paper loaded with the crude extracts. Generally, photosynthesis rates and growth were reduced under low light conditions. Attractiveness to herbivores and macrofoulers, however, was insensitive to energy limitation. We discuss possible explanations for the observed absence of a relationship between light availability and algal defence including the change in nutritional value of the algal tissue, the allocation of resources towards defence instead of growth and the absence of costs for defence
Drinking water treatment by multistage filtration on a household scale: Efficiency and challenges
The Power of the Higgs Mechanism: Higher-Derivative BLG Theories
We use the novel Higgs mechanism of arXiv:0803.3218 to determine the leading
higher-derivative corrections to the Euclidean N = 8 Bagger-Lambert-Gustavsson
field theory. The result matches that previously found for Lorentzian
3-algebras, pointing to a universal answer for all maximally supersymmetric
3-algebra theories. We also comment on the extension to the
lower-supersymmetric case of ABJM theory.Comment: 32 pages, Latex; v2: reference adde
Janus Field Theories from Non-Linear BF Theories for Multiple M2-Branes
We integrate the nonpropagating B_{\mu} gauge field for the non-linear BF
Lagrangian describing N M2-branes which includes terms with even number of the
totally antisymmetric tensor M^{IJK} in arXiv:0808.2473 and for the two-types
of non-linear BF Lagrangians which include terms with odd number of M^{IJK} as
well in arXiv:0809:0985. For the former Lagrangian we derive directly the
DBI-type Lagrangian expressed by the SU(N) dynamical A_{\mu} gauge field with a
spacetime dependent coupling constant, while for the low-energy expansions of
the latter Lagrangians the B_{\mu} integration is iteratively performed. The
derived Janus field theory Lagrangians are compared.Comment: 16 pages, LaTex, no figure
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Forage mass production and grazing loss of sorghum hybrid in response to the density of the sowing and the spacing between planting lines
Aversão alimentar condicionada para o controle da intoxicação por Ipomoea carnea subsp. fistulosa em caprinos
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