604 research outputs found
Predation-driven biotic resistance fails to restrict the spread of a sessile rocky shore invader
The invasive barnacle Balanus glandula has progressively spread along the South African west coast. We used multiple approaches to assess the role of predation by indigenous
whelks in regulating this expansion. B. glandula abundance and distribution were monitored annually while field observations and laboratory experiments assessed the relative predation pressure on B. glandula and the native barnacle Notomegabalanus algicola. In the mid-shore, the whelks Trochia cingulata and Burnt1pena lagenaria fed on N. algicola most often despite the alien B. glandula covering a mean of 86% of the shore at this site. Lower on the shore, the same feeding pattern was evident, although N. algicola was spatially dominant. Feeding experiments revealed that small (mean Β± SD shell length: 13.9 Β± 0.3 mm) and large (19.6 Β± 0.5 mm) T. cingulata consumed up to 70% more N. algicola than B. glandula, displaying a significant avoidance of the alien. While small (15.5 Β± 0.5 mm) B. lagenaria displayed the same pattern, large individuals (27.7 Β± 0.4 mm) consumed equal numbers of the 2 barnacles. The avoidance of B. glandula may be explained by this species possessing thicker shell and opercular plates than N. algicola, while a narrow margin of vulnerable soft tissue around the circumference of the opercular plates makes the native an attractive prey choice. This study demonstrates that predation-driven biotic resistance has not contained the expansion of B. glandula along the South African coast
An outflow in the Seyfert ESO 362-G18 revealed by Gemini-GMOS/IFU observations
IndexaciΓ³n: Scopus.We present two-dimensional stellar and gaseous kinematics of the inner 0.7 Γ 1.2 kpc2 of the Seyfert 1.5 galaxy ESO 362-G18, derived from optical (4092-7338 Γ
) spectra obtained with the GMOS integral field spectrograph on the Gemini South telescope at a spatial resolution of β 170 pc and spectral resolution of 36 km s-1. ESO 362-G18 is a strongly perturbed galaxy of morphological type Sa or S0/a, with a minor merger approaching along the NE direction. Previous studies have shown that the [O III] emission shows a fan-shaped extension of β 10β²β² to the SE. We detect the [O III] doublet, [N II] and HΞ± emission lines throughout our field of view. The stellar kinematics is dominated by circular motions in the galaxy plane, with a kinematic position angle of β 137Β° and is centred approximately on the continuum peak. The gas kinematics is also dominated by rotation, with kinematic position angles ranging from 122Β° to 139Β°, projected velocity amplitudes of the order of 100 km s-1, and a mean velocity dispersion of 100 km s-1. A double-Gaussian fit to the [O III]Ξ»5007 and HΞ± lines, which have the highest signal to noise ratios of the emission lines, reveal two kinematic components: (1) a component at lower radial velocities which we interpret as gas rotating in the galactic disk; and (2) a component with line of sight velocities 100-250 km s-1 higher than the systemic velocity, interpreted as originating in the outflowing gas within the AGN ionization cone. We estimate a mass outflow rate of 7.4 Γ 10-2 Mβ yr-1 in the SE ionization cone (this rate doubles if we assume a biconical configuration), and a mass accretion rate on the supermassive black hole (SMBH) of 2.2 Γ 10-2 Mβ yr-1. The total ionized gas mass within βΌ84 pc of the nucleus is 3.3 Γ 105 Mβ; infall velocities of βΌ34 km s-1 in this gas would be required to feed both the outflow and SMBH accretion. Β© ESO 2018.https://www.aanda.org/articles/aa/abs/2018/06/aa31671-17/aa31671-17.htm
Homoclinic Bifurcations for the Henon Map
Chaotic dynamics can be effectively studied by continuation from an
anti-integrable limit. We use this limit to assign global symbols to orbits and
use continuation from the limit to study their bifurcations. We find a bound on
the parameter range for which the Henon map exhibits a complete binary
horseshoe as well as a subshift of finite type. We classify homoclinic
bifurcations, and study those for the area preserving case in detail. Simple
forcing relations between homoclinic orbits are established. We show that a
symmetry of the map gives rise to constraints on certain sequences of
homoclinic bifurcations. Our numerical studies also identify the bifurcations
that bound intervals on which the topological entropy is apparently constant.Comment: To appear in PhysicaD: 43 Pages, 14 figure
From Majorana theory of atomic autoionization to Feshbach resonances in high temperature superconductors
The Ettore Majorana paper - Theory of incomplete P triplets- published in
1931, focuses on the role of selection rules for the non-radiative decay of two
electron excitations in atomic spectra, involving the configuration interaction
between discrete and continuum channels. This work is a key step for
understanding the 1935 work of Ugo Fano on the asymmetric lineshape of two
electron excitations and the 1958 Herman Feshbach paper on the shape resonances
in nuclear scattering arising from configuration interaction between many
different scattering channels. The Feshbach resonances are today of high
scientific interest in many different fields and in particular for ultracold
gases and high Tc superconductivity.Comment: 13 pages, 7 figures. Journal of Superconductivity and Novel Magnetism
to be publishe
Solidification of Al-Sn-Cu based immiscible alloys under intense shearing
The official published version of the Article can be accessed from the link below - Copyright @ 2009 The Minerals, Metals & Materials Society and ASM InternationalThe growing importance of Al-Sn based alloys as materials for engineering applications
necessitates the development of uniform microstructures with improved performance. Guided by the recently thermodynamically assessed Al-Sn-Cu system, two model immiscible alloys, Al-45Sn-10Cu and Al-20Sn-10Cu, were selected to investigate the effects of intensive melt shearing provided by the novel melt conditioning by advanced shear technology (MCAST) unit on the uniform dispersion of the soft Sn phase in a hard Al matrix. Our experimental results have confirmed that intensive melt shearing is an effective way to achieve fine and uniform
dispersion of the soft phase without macro-demixing, and that such dispersed microstructure can be further refined in alloys with precipitation of the primary Al phase prior to the demixing reaction. In addition, it was found that melt shearing at 200 rpm and 60 seconds will be adequate to produce fine and uniform dispersion of the Sn phase, and that higher shearing speed and prolonged shearing time can only achieve minor further refinement.This work is funded by the EPSRC and
DT
ΠΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΠ΅ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΡΡ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠ² ΠΈΡΡΠΎΡΠ½ΠΈΠΊΠ° ΡΠ΅Π½ΡΠ³Π΅Π½ΠΎΠ²ΡΠΊΠΎΠ³ΠΎ ΠΈΠ·Π»ΡΡΠ΅Π½ΠΈΡ Π½Π° Π±Π°Π·Π΅ ΠΌΠ°Π»ΠΎΠ³Π°Π±Π°ΡΠΈΡΠ½ΠΎΠ³ΠΎ ΡΡΠΊΠΎΡΠΈΡΠ΅Π»Ρ ΡΠ»Π΅ΠΊΡΡΠΎΠ½ΠΎΠ²
ΠΡΠΎΠ²Π΅Π΄Π΅Π½ΠΎ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΡΠΏΠ΅ΠΊΡΡΠΎΠ² ΡΠ΅Π½ΡΠ³Π΅Π½ΠΎΠ²ΡΠΊΠΎΠ³ΠΎ ΠΈΠ·Π»ΡΡΠ΅Π½ΠΈΡ, Π³Π΅Π½Π΅ΡΠΈΡΡΠ΅ΠΌΠΎΠ³ΠΎ ΡΠ»Π΅ΠΊΡΡΠΎΠ½Π°ΠΌΠΈ Ρ ΡΠ½Π΅ΡΠ³ΠΈΠ΅ΠΉ 4β¦10 ΠΡΠ Π² ΠΌΠΈΡΠ΅Π½ΡΡ
ΠΈΠ· ΡΠ°Π·Π»ΠΈΡΠ½ΡΡ
ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»ΠΎΠ² ΠΈ ΡΠ°Π·Π½ΠΎΠΉ ΡΠΎΠ»ΡΠΈΠ½Ρ. ΠΠΏΡΠ΅Π΄Π΅Π»Π΅Π½Ρ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΡΠ΅ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΡ ΠΌΠΈΡΠ΅Π½ΠΈ-ΠΊΠΎΠ½Π²Π΅ΡΡΠΎΡΠ° Π΄Π»Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΡ Π΅Π΅ Π² ΠΌΠ΅Π΄ΠΈΡΠΈΠ½ΡΠΊΠΈΡ
ΠΈΡΡΠΎΡΠ½ΠΈΠΊΠ°Ρ
ΠΌΠΎΠ½ΠΎΡ
ΡΠΎΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠ΅Π½ΡΠ³Π΅Π½ΠΎΠ²ΡΠΊΠΎΠ³ΠΎ ΠΈΠ·Π»ΡΡΠ΅Π½ΠΈΡ Π½Π° Π±Π°Π·Π΅ ΠΌΠ°Π»ΠΎΠ³Π°Π±Π°ΡΠΈΡΠ½ΡΡ
ΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΡΡ
ΡΡΠΊΠΎΡΠΈΡΠ΅Π»Π΅ΠΉ. ΠΡΠΎΠ²Π΅Π΄Π΅Π½Ρ ΠΎΡΠ΅Π½ΠΊΠΈ ΠΈΠ½ΡΠ΅Π½ΡΠΈΠ²Π½ΠΎΡΡΠΈ ΠΈΠ·Π»ΡΡΠ΅Π½ΠΈΡ ΠΈ ΡΡΠ°Π²Π½Π΅Π½ΠΈΠ΅ ΠΈΡΡΠΎΡΠ½ΠΈΠΊΠΎΠ² Π½Π° Π±Π°Π·Π΅ ΡΠ°Π·Π½ΡΡ
ΡΡΠΊΠΎΡΠΈΡΠ΅Π»Π΅ΠΉ
- β¦