22,411 research outputs found
Dark-matter dynamical friction versus gravitational-wave emission in the evolution of compact-star binaries
The measured orbital period decay of compact-star binaries, with
characteristic orbital periods ~days, is explained with very high
precision by the gravitational wave (GW) emission of an inspiraling binary in
vacuum. However, the binary gravitational binding energy is also affected by an
usually neglected phenomenon, namely the dark matter dynamical friction (DMDF)
produced by the interaction of the binary components with their respective DM
gravitational wakes. The entity of this effect depends on the orbital period
and on the local value of the DM density, hence on the position of the binary
in the Galaxy. We evaluate the DMDF produced by three different DM profiles:
the Navarro-Frenk-White (NFW), the non-singular-isothermal-sphere (NSIS) and
the Ruffini-Arg\"uelles-Rueda (RAR) profile based on self-gravitating keV
fermions. We first show that indeed, due to their Galactic position, the GW
emission dominates over the DMDF in the NS-NS, NS-WD and WD-WD binaries for
which measurements of the orbital decay exist. Then, we evaluate the conditions
under which the effect of DMDF on the binary evolution becomes comparable to,
or overcomes, the one of the GW emission. We find that, for instance for
-- NS-WD, --~ NS-NS, and
--~ WD-WD, located at 0.1~kpc, this occurs at orbital
periods around 20--30 days in a NFW profile while, in a RAR profile, it occurs
at about 100 days. For closer distances to the Galactic center, the DMDF effect
increases and the above critical orbital periods become interestingly shorter.
Finally, we also analyze the system parameters for which DMDF leads to an
orbital widening instead of orbital decay. All the above imply that a
direct/indirect observational verification of this effect in compact-star
binaries might put strong constraints on the nature of DM and its Galactic
distribution.Comment: 15 pages, 12 figures, 2 tables, accepted for publication in Phys.
Rev. D, 201
Heuristic Classification of Physical Theories based on Quantum Correlations
Taking quantum formalism as a point of reference and connection, we explore
the various possibilities that arise in the construction of physical theories.
Analyzing the distinct physical phenomena that each of them may describe, we
introduce the different types of hidden variables theories that correspond to
these physical phenomena. A hierarchical classification of the offered
theories, based on the degree of correlation between dichotomic observables in
bipartite systems, as quantified by a Bell type inequality, is finally
proposed.Comment: 13 pages, 2 figure
Non-stochastic behavior of atomic surface diffusion on Cu(111) at all temperatures
Atomic diffusion is usually understood as a succession of random, independent
displacements of an adatom over the surface's potential energy landscape.
Nevertheless, an analysis of Molecular Dynamics simulations of self-diffusion
on Cu(111) demonstrates the existence of different types of correlations in the
atomic jumps at all temperatures. Thus, the atomic displacements cannot be
correctly described in terms of a random walk model. This fact has a profound
impact on the determination and interpretation of diffusion coefficients.Comment: 5 figure
Interactive effects of solar UV radiation and ammonium on the biomass andnutritional compound production in tank cultivated Hydropuntia corne (Rhodophyta)
Figueroa et al. (2016) Acta Aquaculture 16, 331-332Introduction
Hydropuntia cornea is a red alga species cultivated in tanks under nitrogen enrichment with high biomass production and content of high value bioactive compounds (Figueroa et al., 2012; Robledo et al, 2014). In this study, the combined effects (2 Ă 2 factorial design) of solar radiation (in door (I), green house cutting off the UV radiation and out-door (O) with UV radiation) and nitrogen (ammonium) under high (HN) and low (LN) levels on biomass production (g DW m-2 d-1), biofiltration as Nitrogen uptake efficiency (NUE, %) and Nitrogen uptake rate (NUR, mmol N m-2 h-1), photosynthetic activity as maximal electron transport rate (ETRmax), starch content and antioxidant activity were analyzed in H.cornea grown in tanks for 35 days in the above mentioned conditions.
Material and methods
The red seaweed Hydropuntia cornea was cultivated in cylindrical tanks of 90 L (0.17 m2 superficial area) with open flow-through N and P-enrichment (5 NH4Cl: 1 KHPO4, in a concentration ranges between 50 - 250 ”M). Seaweed density assayed in tanks was 9 g FW L-1. Turnover rates were 64 and 6.4 vol d-1 in high and low flow rate, respectively. Photosynthetic activity was measured by using in vivo chlorophyll a fluorescence associated to photosystem II i.e. Electron transport rate (ETR) expressed as Όmol electrons m-2 s-1. Starch (%) was determined according to anthrone method (Brooks et al. 1986) and antioxidant activity was evaluated following ABTS method (Ree et al., 1999) and expressed as Trolox equivalent (ΌM TEAC g-1 DW).
Results
Maximal photosynthetic production (ETRmax) increased throughout the culture time. (Fig. 1.A). After 35 d culture, ETRmax was higher under HN than that under LN both under in door and out door conditions (Fig.1A). However, biomass production expressed as g DW m-2 d-1 decreased throughout the experimental time (Fig 1.B). After 35d culture the highest biomass production was reached under HN-O and the lowest under LN-O although the differences were not so high (Fig.1B). The maximal efficiency of N assimilation (NUE %) was greater under LN (98%) than that under HN treatment (72%). NUE decreased throughout the time although after 35 d a clear increase was observed (Table 1). In contrast, the maximal nitrogen uptake rate (NUR) was higher under HN (45.5 mmol N m-2 h-1) than that under LN (25.8 mmol N m-2 h-1). The highest values of both NUE and NUR were obtained under solar radiation (outdoor treatments). Starch ranged from 25.1% (LN-I, 21 d) to 49.6 % (LN-O, 28 d) whereas the highest antioxidant activity was reached under LN-O after 21 d culture (68.5 ÎŒM TEAC g-1 DW). After 35d the highest level was again under LN-O (65.2 ÎŒM TEAC g-1 DW) followed by HN-O treatment (57.3 ÎŒM TEAC g-1 DW).Discussion and conclusions
Ammonium supply, simulating fishpond effluents, and full solar irradiation (presence of UV radiation) have a positive effect on photosynthetic rate as ETRmax. The decrease in biomass production in spite of the increase of photosynthetic activity and nitrogen uptake rate is explained because the algae through the time could inverse more energy for the accumulation of metabolites (starch and antioxidant compounds) that that for growth. In any case the highest accumulation of starch and antioxidant activity were observed in the treatments associated to the greatest stress conditions i.e LN and outdoor culture due to UVR can negatively affect biological processes related to growth. As expected, under HN supply NUE was lower than that under LN but NUR was the reverse. H. cornea grown in simulated fishpond effluents displays a high biofiltration rate of inorganic N and accumulates commercially N compounds, as the photoprotector-antioxidant substances, mycosporine-like aminoacids (Figueroa et al., 2012) and C-compounds for nutritional uses or bioethanol production. In this study, the antioxidant activity was much higher than that reported in other seaweeds (Matanjun et al., 2008). H. cornea can be cultured and used to remove nutrient-rich fishpond effluents from aquaculture industries and besides, this biomass provides compounds of high added value for the biotechnology industry.
References
Brooks, J.R., Griffin, V.K., Kattan, M.W. 1986.A modified method for total carbohydrate analysisof glucose syrups, maltodextrins and other starch hydrolysis products. Cereal Chem 63:465-466.
Figueroa, F. L., Korbee, N., Abdala, R., Jerez, C. G., LĂłpez-de la Torre, M., GĂŒenaga, L., GĂłmez-Pinchetti, J. L. 2012. Biofiltration of fishpond effluents and accumulation of N-compounds (phycobiliproteins and mycosporine-like amino acids) versus C-compounds (polysaccharides) in Hydropuntia cornea (Rhodophyta). Marine Pollution Bulletin, 64(2), 310-318.
Matanjun, P., Mohamed, S., Mustapha, N.M., Ming, C.H. 2008. Antioxidant activities and phenolics content of eight species of seaweeds from north Borneo. J Appl Phycol 20:367â373.
Re, R., Pellegrini, N., Proteggente, A., Pannala, A.,Yang,M., Rice-Evans, C. 1999. Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free Radic Biol Med 26:1231â1237.
Robledo, D., NavarroâAngulo, L., Valdes Lozano, D., FreileâPelegrĂn, Y. 2014. Nutrient removal efficiency of Hydropuntia cornea in an integrated closed recirculation system with pink shrimp Farfantepenaeus brasiliensis. Aquaculture Research, 45(10), 1648-1658Universidad de MĂĄlaga.Campus de Excelencia Internacional Andalucia Tech
An updated catalog of OH-maser-emitting planetary nebulae
Aims. We studied the characteristics of planetary nebulae (PNe) that show
both OH maser and radio continuum emission (hereafter OHPNe). These have been
proposed to be very young PNe, and therefore, they could be key objects for
understanding the formation and evolution of PNe. Methods. We consulted the
literature searching for interferometric observations of radio continuum and OH
masers toward evolved stars, including the information from several surveys. We
also processed radio continuum and OH maser observations toward PNe in the Very
Large Array data archive. The high positional accuracy provided by
interferometric observations allow us to confirm or reject the association
between OH maser and radio continuum emission. Results. We found a total of six
PNe that present both OH maser and radio continuum emissions, as confirmed with
radio interferometric observations. These are bona fide OHPNe. The confirmed
OHPNe present a bipolar morphology in resolved images of their ionized emission
at different wavelengths, suggesting that the OH maser emission in PNe is
related to nonspherical mass-loss phenomena. The OH maser spectra in PNe
present a clear asymmetry, tending to show blueshifted emission with respect to
the systemic velocity. Their infrared colors suggest that most of these objects
are very young PNe. OHPNe do not form a homogeneous group, and seem to
represent a variety of different evolutionary stages. We suggest that OH masers
pumped in the AGB phase may disappear during the post-AGB phase, but reappear
once the source becomes a PN and its radio continuum emission is amplified by
the OH molecules. Therefore, OH maser emission could last significantly longer
than the previously assumed 1000 yr after the end of the AGB phase. This maser
lifetime may be longer in PNe with more massive central stars, which ionize a
larger amount of gas in the envelope.Comment: 16 pages, 5 figures, 4 tables. Accepted for publication by Astronomy
& Astrophysic
The innermost regions of the jet in NRAO 150. Wobbling or internal rotation?
NRAO 150 is a very bright millimeter to radio quasar at redshift =1.52 for
which ultra-high-resolution VLBI monitoring has revealed a counter-clockwise
jet-position-angle wobbling at an angular speed /yr in the
innermost regions of the jet. In this paper we present new total and linearly
polarized VLBA images at 43 GHz extending previous studies to cover the
evolution of the jet in NRAO 150 between 2006 and early 2009. We propose a new
scenario to explain the counter-clockwise rotation of the jet position angle
based on a helical motion of the components in a jet viewed faced-on. This
alternative scenario is compatible with the interpretation suggested in
previous works once the indetermination of the absolute position of the
self-calibrated VLBI images is taken into account. Fitting of the jet
components motion to a simple internal rotation kinematical model shows that
this scenario is a likely alternative explanation for the behavior of the
innermost regions in the jet of NRAO 150.Comment: 5 pages, 4 figures, Presented in 'The Innermost Regions of
Relativistic Jets and Their Magnetic Fields' conference. Granada, Spain, 201
- âŠ