19,965 research outputs found
Effective Interaction Techniques for the Gamow Shell Model
We apply a contour deformation technique in momentum space to the newly
developed Gamow shell model, and study the drip-line nuclei 5He, 6He and 7He. A
major problem in Gamow shell-model studies of nuclear many-body systems is the
increasing dimensionality of many-body configurations due to the large number
of resonant and complex continuum states necessary to reproduce bound and
resonant state energies. We address this problem using two different effective
operator approaches generalized to the complex momentum plane. These are the
Lee-Suzuki similarity transformation method for complex interactions and the
multi-reference perturbation theory method. The combination of these two
approaches results in a large truncation of the relevant configurations
compared with direct diagonalization. This offers interesting perspectives for
studies of weakly bound systems.Comment: 18 pages, 17 figs, Revtex
Sticky Particles and Stochastic Flows
Gaw\c{e}dzki and Horvai have studied a model for the motion of particles
carried in a turbulent fluid and shown that in a limiting regime with low
levels of viscosity and molecular diffusivity, pairs of particles exhibit the
phenomena of stickiness when they meet. In this paper we characterise the
motion of an arbitrary number of particles in a simplified version of their
model
Toward identification of larval sailfish (Istiophorus platypterus), white marlin (Tetrapturus albidus), and blue marlin (Makaira nigricans) in the western North Atlantic Ocean*
The identification of larval istiophorid billfishes from the western North Atlantic Ocean has long been problematic. In the present study, a molecular technique was used to positively identify 27 larval white marlin (Tetrapturus albidus), 96 larval blue marlin (Makaira nigricans), and 591
larval sailfish (Istiophorus platypterus) from the Straits of Florida and the Bahamas. Nine morphometric measurements were taken for a subset of larvae (species known), and lower
jaw pigment patterns were recorded on a grid. Canonical variates analysis (CVA) was used to reveal the extent
to which the combination of morphometric, pigment pattern, and month of capture information was diagnostic to species level. Linear regression revealed species-specific relationships between the ratio of snout length to eye orbit diameter and standard length (SL). Confidence limits about these relationships served as defining characters for sailfish >10 mm SL and for blue and white marlin >17 mm SL.
Pigment pattern analysis indicated that 40% of the preflexion blue marlin examined possessed a characteristic
lower jaw pigment pattern and that 62% of sailfish larvae were identifiable by lower jaw pigments alone. An identification key was constructed based on pigment patterns, month of capture, and relationships between SL and the ratio of snout length to eye orbit diameter. The key yielded identifications for 69.4% of 304 (blind
sample) larvae used to test it; only one of these identifications was incorrect. Of the 93 larvae that could not be identified by the key, 71 (76.3%) were correctly identified with CVA. Although identif ication of certain
larval specimens may always require molecular techniques, it is encouraging that the majority (92.4%) of istiophorid larvae examined were ultimately identifiable from external
characteristics alone
A comparison of cortical and trabecular bone from C57 Black 6 mice using Raman spectroscopy
Peer reviewedPostprin
Momentum dependence of drag coefficients and heavy flavour suppression in quark gluon plasma
The momentum dependence of the drag coefficient of heavy quarks propagating
through quark gluon plasma (QGP) has been evaluated. The results have been used
to estimate the nuclear suppression factor of charm and bottom quarks in QGP.
We observe that the momentum dependence of the transport coefficients plays
crucial role in the suppression of the heavy quarks and consequently in
discerning the properties of QGP using heavy flavours as a probe. We show that
the large suppression of the heavy quarks observed at RHIC and LHC is
predominantly due to the radiative losses. The suppression of in Pb+Pb
collisions at LHC energy - recently measured by the ALICE collaboration has
also been studied.Comment: Minor changes in the tex
Site-selective measurement of coupled spin pairs in an organic semiconductor
From organic electronics to biological systems, understanding the role of intermolecular interactions between spin pairs is a key challenge. Here we show how such pairs can be selectively addressed with combined spin and optical sensitivity. We demonstrate this for bound pairs of spin-triplet excitations formed by singlet fission, with direct applicability across a wide range of synthetic and biological systems. We show that the site sensitivity of exchange coupling allows distinct triplet pairs to be resonantly addressed at different magnetic fields, tuning them between optically bright singlet (S=0) and dark triplet quintet (S=1,2) configurations: This induces narrow holes in a broad optical emission spectrum, uncovering exchange-specific luminescence. Using fields up to 60 T, we identify three distinct triplet-pair sites, with exchange couplings varying over an order of magnitude (0.3–5 meV), each with its own luminescence spectrum, coexisting in a single material. Our results reveal how site selectivity can be achieved for organic spin pairs in a broad range of systems
Ohmic and step noise from a single trapping center hybridized with a Fermi sea
We show that single electron tunneling devices such as the Cooper-pair box or
double quantum dot can be sensitive to the zero-point fluctuation of a single
trapping center hybridized with a Fermi sea. If the trap energy level is close
to the Fermi sea and has line-width \gamma > k_B T, its noise spectrum has an
Ohmic Johnson-Nyquist form, whereas for \gamma < k_B T the noise has a
Lorentzian form expected from the semiclassical limit. Trap levels above the
Fermi level are shown to lead to steps in the noise spectrum that can be used
to probe their energetics, allowing the identification of individual trapping
centers coupled to the device.Comment: Revised version to appear in Phys. Rev. Let
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