1,444 research outputs found
Effectiveness of the global protected area network in representing species diversity
The Fifth World Parks Congress in Durban, South Africa, announced in September 2003 that the global network of protected areas now covers 11.5% of the planet's land surface. This surpasses the 10% target proposed a decade earlier, at the Caracas Congress, for 9 out of 14 major terrestrial biomes. Such uniform targets based on percentage of area have become deeply embedded into national and international conservation planning. Although politically expedient, the scientific basis and conservation value of these targets have been questioned. In practice, however, little is known of how to set appropriate targets, or of the extent to which the current global protected area network fulfils its goal of protecting biodiversity. Here, we combine five global data sets on the distribution of species and protected areas to provide the first global gap analysis assessing the effectiveness of protected areas in representing species diversity. We show that the global network is far from complete, and demonstrate the inadequacy of uniform—that is, 'one size fits all'—conservation targets
Fluctuations and Instabilities of Ferromagnetic Domain Wall pairs in an External Magnetic Field
Soliton excitations and their stability in anisotropic quasi-1D ferromagnets
are analyzed analytically. In the presence of an external magnetic field, the
lowest lying topological excitations are shown to be either soliton-soliton or
soliton-antisoliton pairs. In ferromagnetic samples of macro- or mesoscopic
size, these configurations correspond to twisted or untwisted pairs of Bloch
walls. It is shown that the fluctuations around these configurations are
governed by the same set of operators. The soliton-antisoliton pair has exactly
one unstable mode and thus represents a critical nucleus for thermally
activated magnetization reversal in effectively one-dimensional systems. The
soliton-soliton pair is stable for small external fields but becomes unstable
for large magnetic fields. From the detailed expression of this instability
threshold and an analysis of nonlocal demagnetizing effects it is shown that
the relative chirality of domain walls can be detected experimentally in thin
ferromagnetic films. The static properties of the present model are equivalent
to those of a nonlinear sigma-model with anisotropies. In the limit of large
hard-axis anisotropy the model reduces to a double sine-Gordon model.Comment: 15 pages RevTex 3.0 (twocolumn), 9 figures available on request, to
appear in Phys Rev B, Dec (1994
The Landau Pole and decays in the 331 bilepton model
We calculate the decay widths and branching ratios of the extra neutral boson
predicted by the 331 bilepton model in the framework of two
different particle contents. These calculations are performed taken into
account oblique radiative corrections, and Flavor Changing Neutral Currents
(FCNC) under the ansatz of Matsuda as a texture for the quark mass matrices.
Contributions of the order of are obtained in the branching
ratios, and partial widths about one order of magnitude bigger in relation with
other non- and bilepton models are also obtained. A Landau-like pole arise at
3.5 TeV considering the full particle content of the minimal model (MM), where
the exotic sector is considered as a degenerated spectrum at 3 TeV scale. The
Landau pole problem can be avoid at the TeV scales if a new leptonic content
running below the threshold at TeV is implemented as suggested by other
authors.Comment: 20 pages, 5 figures, LaTeX2
New evidence for strong nonthermal effects in Tycho's supernova remnant
For the case of Tycho's supernova remnant (SNR) we present the relation
between the blast wave and contact discontinuity radii calculated within the
nonlinear kinetic theory of cosmic ray (CR) acceleration in SNRs. It is
demonstrated that these radii are confirmed by recently published Chandra
measurements which show that the observed contact discontinuity radius is so
close to the shock radius that it can only be explained by efficient CR
acceleration which in turn makes the medium more compressible. Together with
the recently determined new value erg of the SN
explosion energy this also confirms our previous conclusion that a TeV
gamma-ray flux of erg/(cms) is to be expected from
Tycho's SNR. Chandra measurements and the HEGRA upper limit of the TeV
gamma-ray flux together limit the source distance to kpc.Comment: 5 pages, 4 figures. Accepted for publication in Astrophysics and
Space Science, Proc. of "The Multi-Messenger Approach to High-Energy
Gamma-ray Sources (Third Workshop on the Nature of Unidentified High-Energy
Sources)", Barcelona, July 4-7, 200
Magnetothemopower study of quasi two-dimensional organic conductor -(BEDT-TTF)KHg(SCN)
We have used a low-frequency magneto-thermopower (MTEP) method to probe the
high magnetic field ground state behavior of
-(BEDT-TTF)KHg(SCN) along all three principal crystallographic
axes at low temperatures. The thermopower tensor coefficients (
and ) have been measured to 30 T, beyond the anomalous low temperature,
field-induced transition at 22.5 T. We find a significant anisotropy in the
MTEP signal, and also observe large quantum oscillations associated with the de
Haas - van Alphen effect. The anisotropy indicates that the ground state
properties are clearly driven by mechanisms that occur along specific
directions for the in-plane electronic structure. Both transverse and
longitudinal magnetothermopower show asymptotic behavior in field, which can be
explained in terms of magnetic breakdown of compensated closed orbits.Comment: 9 pages, 10 figure
Social Cohesion, Structural Holes, and a Tale of Two Measures
EMBARGOED - author can archive pre-print or post-print on any open access repository after 12 months from publication. Publication date is May 2013 so embargoed until May 2014.This is an author’s accepted manuscript (deposited at arXiv arXiv:1211.0719v2 [physics.soc-ph] ), which was subsequently published in Journal of Statistical Physics May 2013, Volume 151, Issue 3-4, pp 745-764. The final publication is available at link.springer.com http://link.springer.com/article/10.1007/s10955-013-0722-
Freezability genetics in rabbit semen
[EN] The aim of this study was to estimate the heritability of semen freezability and to estimate the genetic correlation between frozen-thawed sperm traits and the growth rate in a paternal rabbit line. Estimated heritabilities showed that frozen-thawed semen traits are heritable (ranged between 0.08 and 0.15). In the case of Live-FT (percentage of viable sperm after freezing), the estimated heritability is the highest one, and suggests the possibility of effective selection. After the study of genetic correlations it seems that daily weight gain (DG) was negatively correlated with sperm freezability, but no further conclusions could be drawn due to the high HPD95%. More data should be included in order to obtain better accuracy for the estimates of these genetic correlations. If the results obtained at present study were confirmed, it would imply that selection for DG could alter sperm cell membranes or seminal plasma composition, both components related to sperm cryoresistance. (C) 2017 Elsevier Inc. All rights reserved.This work was supported by the Generalitat Valenciana research program (Prometeo II 2014/036). Lavara R. acknowledges the partial support received from Generalitat Valenciana under VALid program (APOST/2014/034) and from Ministry of Economy and Competitiveness under subprogramme "Formation posdoctoral" (FPDI-2013-16707).Lavara García, R.; Moce Cervera, ET.; Baselga Izquierdo, M.; Vicente Antón, JS. (2017). Freezability genetics in rabbit semen. Theriogenology. 102:54-58. https://doi.org/10.1016/j.theriogenology.2017.07.013S545810
Violation of the Nernst heat theorem in the theory of thermal Casimir force between Drude metals
We give a rigorous analytical derivation of low-temperature behavior of the
Casimir entropy in the framework of the Lifshitz formula combined with the
Drude dielectric function. An earlier result that the Casimir entropy at zero
temperature is not equal to zero and depends on the parameters of the system is
confirmed, i.e. the third law of thermodynamics (the Nernst heat theorem) is
violated. We illustrate the resolution of this thermodynamical puzzle in the
context of the surface impedance approach by several calculations of the
thermal Casimir force and entropy for both real metals and dielectrics.
Different representations for the impedances, which are equivalent for real
photons, are discussed. Finally, we argue in favor of the Leontovich boundary
condition which leads to results for the thermal Casimir force that are
consistent with thermodynamics.Comment: 24 pages, 3 figures, accepted for publication in Phys. Rev.
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