989 research outputs found
Circular strings, wormholes and minimum size
The quantization of circular strings in an anti-de Sitter background
spacetime is performed, obtaining a discrete spectrum for the string mass. A
comparison with a four-dimensional homogeneous and isotropic spacetime coupled
to a conformal scalar field shows that the string radius and the scale factor
have the same classical solutions and that the quantum theories of these two
models are formally equivalent. However, the physically relevant observables of
these two systems have different spectra, although they are related to each
other by a specific one-to-one transformation. We finally obtain a discrete
spectrum for the spacetime size of both systems, which presents a nonvanishing
lower bound.Comment: 11 pages, LaTeX2e, minor change
The burn severity and plant recovery relationship affect the biological and chemical soil properties of Pinus halepensis Mill. stands in the short and midterms after wildfire
In the Mediterranean Basin, changes in climate and fire regime (increased recurrence and severity) reduce
ecosystem services after wildfires by increasing soil degradation and losses in plant diversity. Our study was a
biological approach to relate soil properties to vegetation recovery and burn severity. We focused our study on
the natural recovery of the soil-plant interphase in Pinus halepensis Mill. forests located in the SE of Iberian
Peninsula, a semiarid climate. We included some chemical properties 3 years after fire (available phosphorus (P)
and soil organic carbon (Corg), among others), and biological soil indicators 3 and 5 years after fire (i.e. basal
soil respiration (BSR), microbial biomass carbon (Cmic), carbon mineralization coefficient (Cmineral), metabolic
quotient (qCO2) and microbial quotient (Cmic:Corg)). We analyzed the activity of three different enzymes: urease
(UR), phosphatase (PHP) and β-glucosidase (GLU).
The changes in most chemical properties were ephemeral, but P and Corg showed higher values in burned
areas, and the highest were found for low-moderate severity. Plant recovery was the triggering factor for the
recovery of Corg and biological soil function. Burn severity and time after fire influenced Cmic and the
Cmic:Corg, which were higher for moderate-high severity 3 years later, but were below the unburned values 5
years after fire. The microbial activities of GLU and UR were recovered in burned areas 5 years after fire. The
PHP values lowered according to higher burn severity and time after fire. The soil ecological trends obtained by a
principal component analysis revealed a relationship linking GLU, BSR and qCO2 that explained soil response to
burn severity. PHP, Cmic and Cmic:Corg explained most of the variability related to time after fire.
Our results provide insights into how burn severity, in Mediterranean fire-prone Aleppo pine stands,
modulated the natural plant recovery linked to soil biochemical and microbiological response to fire. High burn
severity limited natural vegetation recovery, and both reduced biological soil functionality. This knowledge can
be implemented in post-fire planning to apply post-fire management (for mitigation and restoration) in which
the “no intervention” tool should be contemplated. These findings provide information to be applied in adaptive
forest management to improve the resilience of vulnerable ecosystems and to reduce burn severity in future fire
events.This study was supported by a research award provided by the Instituto Estudios Albacetenses (IEA2016-Daniel Moya) and funds provided to the Forest Ecology Research Group by the University Castilla-La Mancha.The authors also thank the Spanish Institute for Agricultural and Food Research and Technology (INIA) for the funding awarded through National Research Projects GEPRIF (RTA2014-00011-C06), POSTFIRE_CARE (CGL2016-75178-C2-1-R) financed by the Spanish Research Agency (AIE), and the European Union for European Funding for Regional Development (FEDER)
Temporal characterisation of soil-plant natural recovery related to fire severity in burned Pinus halepensis Mill. forests
Despite Mediterranean ecosystems' high resilience to fire, both climate and land use change, and alterations in fire regimes increase their vulnerability to fire by affecting the long-term natural recovery of ecosystem services. The objective of this work is to study the effects of fire severity on biochemical soil indicators, such as chemical composition or enzymatic activity, related to time after fire and natural vegetation recovery (soil-plant interphase). Soil samples from three wildfires occurring 3, 15 and 21 years ago were taken in the south-eastern Iberian Peninsula (semiarid climate). Sampling included three fire severity levels in naturally regenerated (and changing to shrublands) Pinus halepensis Mill. forests.
In the short-term post-fire period, phosphorus concentration, electrical conductivity and urease activity were positively linked to fire severity, and also influenced β-glucosidade activity in a negative relationship. During the 15–21-year post-fire period, the effects related to medium-high fire severity were negligible and soil quality indicators were linked to natural regeneration success. The results showed that most soil properties recovered in the long term after fire (21 years).
These outcomes will help managers and stakeholders to implement management tools to stabilise soils and to restore burned ecosystems affected by medium-high fire severity. Such knowledge can be considered in adaptive forest management to reduce the negative effects of wildfires and desertification, and to improve the resilience of vulnerable ecosystems in a global change scenario.This study was supported by a grant for research initiation provided by the Excma. Diputación Albacete (DIPU4-AB2015) and by the funds provided by University Castilla-La Mancha to the Forest Ecology Research Group.The authors with to thank the Spanish Institute for Agricultural and Food Research and Technology (INIA) for the funding awarded through National Research Projects GEPRIF (RTA2014-00011-C06)
Desarrollo de la Red Aerobiológica de Castilla y León (RACYL)
XV lnternational A.P.L.E. Symposium of Palynolog
Dual regulation of the T-type Ca2+ current by serum albumin and β-estradiol in mammalian spermatogenic cells
AbstractThis study provides evidence for a novel mechanism of voltage-gated Ca2+ channel regulation in mammalian spermatogenic cells by two agents that affect sperm capacitation and the acrosome reaction (AR). Patch-clamp experiments demonstrated that serum albumin induced an increase in Ca2+ T current density in a concentration-dependent manner, and significant shifts in the voltage dependence of both steady-state activation and inactivation of the channels. These actions were not related to the ability of albumin to remove cholesterol from the membrane. In contrast, β-estradiol significantly inhibited Ca2+ channel activity in a concentration-dependent and essentially voltage-independent fashion. In mature sperm this dual regulation may influence capacitation and/or the AR
New aspects in the biology of fish pathogen Photobacterium damselae subsp. piscicida: pili, motility and adherence to solid surfaces
New GTC spectroscopic data and a statistical study to better constrain the redshift of the BL Lac RGB J2243 + 203
We present new spectroscopic data of the BL Lac RGB 2243 + 203, and its surroundings, obtained with the OSIRIS Multi Object Spectrograph (MOS) mounted in the Gran Telescopio Canarias (GTC). The spectra of neither the BL Lac nor its host galaxy show any spectral feature, thus hindering direct determination of its redshift. The spectroscopic redshift distribution of objects in the MOS field of view shows four galaxies with redshift between 0.5258 and 0.5288. We make use of a statistical analysis to test the possibility that the targeted BL Lac may be a member of that group. By using the spectroscopic redshifts obtained with our GTC observations, we found that this probability is between 86 and 93 per cent.Fil: Rosa González, D. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Muriel, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Mayya, Y. D.. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Aretxaga, I.. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Becerra González, J.. Instituto de Astrofisica de Canarias; EspañaFil: Carramiñana, Alberto. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Méndez-Abreu, J.. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Vega, O. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Terlevich, E-. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Coutiño de León, S.. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Furniss, A.. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Longinotti, A. L.. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Terlevich, R. J.. Instituto Nacional de Astrofísica, Optica y Electrónica; MéxicoFil: Pichel, Ana Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Rovero, Adrian Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Donzelli, Carlos Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentin
Nearby early-type galaxies with ionized gas VI. The Spitzer-IRS view
We present low resolution Spitzer-IRS spectra of 40 ETGs, selected from a
sample of 65 ETGs showing emission lines in their optical spectra. We
homogeneously extract the mid-infrared (MIR) spectra, and after the proper
subtraction of a "passive" ETG template, we derive the intensity of the ionic
and molecular lines and of the polycyclic aromatic hydrocarbon emission
features. We use MIR diagnostic diagrams to investigate the powering mechanisms
of the ionized gas. The mid-infrared spectra of early-type galaxies show a
variety of spectral characteristics. We empirically sub-divide the sample into
five classes of spectra with common characteristics. Class-0, accounting for
20% of the sample, are purely passive ETGs with neither emission lines nor PAH
features. Class-1 show emission lines but no PAH features, and account for
17.5% of the sample. Class-2, in which 50% of the ETGs are found, as well as
having emission lines, show PAH features with unusual ratios, e.g. 7.7
{\mu}m/11.3 {\mu}m \leq 2.3. Class-3 objects have emission lines and PAH
features with ratios typical of star-forming galaxies. 7.5% of objects fall in
this class, likely to be objects in a starburst/post-starburst regime. Class-4,
containing only 5% of the ETGs, is dominated by a hot dust continuum. The
diagnostic diagram [Ne III]15.55{\mu}m/[Ne II]12.8{\mu}m vs. [S
III]33.48{\mu}m/[Si II]34.82{\mu}m, is used to investigate the different
mechanisms ionizing the gas. If we exclude NGC 3258 where a starburst seems
present, most of our ETGs contain gas ionized via either AGN-like or shock
phenomena, or both. Most of the spectra in the present sample are classified as
LINERs in the optical window. The proposed MIR spectral classes show
unambiguously the manifold of the physical processes and ionization mechanisms,
from star formation, low level AGN activity, to shocks, present in LINER
nuclei.Comment: Accepted for publication in Astronomy and Astrophysic
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