287 research outputs found
Production and carbonate dynamics of Halimeda incrassata (Ellis)Lamouroux altered by Thalassia testudinum Banks and Soland ex König
Ocean acidification poses a serious threat to a broad suite of calcifying organisms. Scleractinian corals and cal-
careous algae that occupy shallow, tropical waters are vulnerable to global changes in ocean chemistry be-
cause they already are subject to stressful and variable carbon dynamics at the local scale. For example, net
heterotrophy increases carbon dioxide concentrations, and pH varies with diurnal fluctuations in photosyn-
thesis and respiration. Few researchers, however, have investigated the possibility that carbon dioxide con-
sumption during photosynthesis by non-calcifying photoautotrophs, such as seagrasses, can ameliorate
deleterious effects of ocean acidi
fi
cation on sympatric calcareous algae. Naturally occurring variations in
the density of seagrasses and associated calcareous algae provide an ecologically relevant test of the hypoth-
esis that diel
fl
uctuations in water chemistry driven by cycles of photosynthesis and respiration within
seagrass beds create microenvironments that enhance macroalgal calci
fi
cation. In Grape Tree Bay off Little
Cayman Island BWI, we quanti
fi
ed net production and characterized calci
fi
cation for thalli of the calcareous
green alga
Halimeda incrassata
growing within beds of
Thalassia testudinum
with varying shoot densities. Re-
sults indicated that individual
H
.
incrassata
thalli were ~6% more calci
fi
ed in dense seagrass beds. On an areal
basis, however, far more calcium carbonate was produced by
H
.
incrassata
in areas where seagrasses were
less dense due to higher rates of production. In addition, diel pH regimes in vegetated and unvegetated
areas within the lagoon were not signi
fi
cantly different, suggesting a high degree of water exchange and
mixing throughout the lagoon. These results suggest that, especially in well-mixed lagoons, carbonate pro-
duction by calcareous algae may be more related to biotic interactions between seagrasses and calcareous
algae than to seagrass-mediated changes in local water chemistry
Dissemination of rat cytomegalovirus through infected granulocytes and monocytes in vitro and in vivo
The role of leukocytes in the in vivo dissemination of cytomegalovirus was studied in this experiment. Rat cytomegalovirus (RCMV) could be transferred to rat granulocytes and monocytes by cocultivation with RCMV-infected fibroblasts in vitro. Intravenous injection of purified infected granulocytes or monocytes resulted in a systemic infection in rats, indicating that our model is a powerful tool to gain further insight into CMV dissemination and the development of new antivirals
Multipartite entangled coherent states
We propose a scheme for generating multipartite entangled coherent states via
entanglement swapping, with an example of a physical realization in ion traps.
Bipartite entanglement of these multipartite states is quantified by the
concurrence. We also use the --tangle to compute multipartite entanglement
for certain systems. Finally we establish that these results for entanglement
can be applied to more general multipartite entangled nonorthogonal states.Comment: 7 pages, two figures. We added more detail discussions on the
generation of multipartite entangled coherent states and multipartite
entangelemen
Multipartite entangled states in coupled quantum dots and cavity-QED
We investigate the generation of multipartite entangled state in a system of
N quantum dots embedded in a microcavity and examine the emergence of genuine
multipartite entanglement by three different characterizations of entanglement.
At certain times of dynamical evolution one can generate multipartite entangled
coherent exciton states or multiqubit states by initially preparing the
cavity field in a superposition of coherent states or the Fock state with one
photon, respectively. Finally we study environmental effects on multipartite
entanglement generation and find that the decay rate for the entanglement is
proportional to the number of excitons.Comment: 9 pages, 4 figures, to appear in Phys. Rev.
Spin squeezing and pairwise entanglement for symmetric multiqubit states
We show that spin squeezing implies pairwise entanglement for arbitrary
symmetric multiqubit states. If the squeezing parameter is less than or equal
to 1, we demonstrate a quantitative relation between the squeezing parameter
and the concurrence for the even and odd states. We prove that the even states
generated from the initial state with all qubits being spin down, via the
one-axis twisting Hamiltonian, are spin squeezed if and only if they are
pairwise entangled. For the states generated via the one-axis twisting
Hamiltonian with an external transverse field for any number of qubits greater
than 1 or via the two-axis counter-twisting Hamiltonian for any even number of
qubits, the numerical results suggest that such states are spin squeezed if and
only if they are pairwise entangled.Comment: 6 pages. Version 3: Small corrections were mad
The application of micro-Raman for the analysis of ochre artefacts from Mesolithic palaeo-lake Flixton
Ochre is an important mineral pigment used by prehistoric hunter-gatherers across the globe, and its use in the Mesolithic is no exception. Using optical microscopy and Raman spectroscopy with micrometre spatial resolution (micro-Raman), we present evidence that confirms unambiguously the use of ochre by hunter-gatherers at Mesolithic sites surrounding Palaeo-Lake Flixton, Vale of Pickering, North Yorkshire, UK. Our results suggest that people collected ochre and processed it in different ways, likely for diverse purposes. The quality and specificity of chemical characterisation possible with micro-Raman facilitates new avenues for further research on ochreous materials in Britain, including provenancing through chemical ‘fingerprinting’
Cartilage repair in an osteochondral defect in a rabbit model
Despite the fact that mesenchymal stem cells (MSC) offer clinical potential for osteoarthritis applications, retaining sufficient numbers of functional MSC at the site of injury for optimal repair still continues to be a major challenge. One method of overcoming this limitation is to create an artificial extracellular matrix or scaffold to hold the cells in place. Previous research suggests that biomaterials possessing an elastic modulus between 2-50MPa are suitable for functional cartilage repair. To this end, the main aim of this study was to examine the effect of scaffold mechanical properties on cartilage repair in a rabbit model in vivo
The G0 Experiment: Apparatus for Parity-Violating Electron Scattering Measurements at Forward and Backward Angles
In the G0 experiment, performed at Jefferson Lab, the parity-violating
elastic scattering of electrons from protons and quasi-elastic scattering from
deuterons is measured in order to determine the neutral weak currents of the
nucleon. Asymmetries as small as 1 part per million in the scattering of a
polarized electron beam are determined using a dedicated apparatus. It consists
of specialized beam-monitoring and control systems, a cryogenic hydrogen (or
deuterium) target, and a superconducting, toroidal magnetic spectrometer
equipped with plastic scintillation and aerogel Cerenkov detectors, as well as
fast readout electronics for the measurement of individual events. The overall
design and performance of this experimental system is discussed.Comment: Submitted to Nuclear Instruments and Method
Assessment of penetration of Ascorbyl Tetraisopalmitate into biological membranes by molecular dynamics
The present work, involves the simulation of the transport of a vitamin C derivative, Ascorbyl Tetraisopalmitate (ATI), through human skin by molecular dynamics. Percutaneous absorption of the ATI molecule through the infundibulum, an important route of absorption into the hair follicle of the human skin, has been modeled and compared with the stratum corneum membrane. The comparative study was done, using molecular dynamics with Martini force field. In infundibulum, a single ATI molecule require more time to penetrate, and the data obtained suggested that a high concentration of ATI molecule accelerated the process of penetration. In conclusion, the ATI molecule was found to have more affinity towards the stratum corneum as compared towards the infundibulum and it followed a straight pathway to penetrate (until 600 ns of simulation). In infundibulum, it showed less affinity, more mobility and followed a lateral pathway. Thus, this work contributes to a better understanding of the different molecular interactions during percutaneous absorption of active molecules in these two different types of biological membranes.The authors acknowledge financial support from the Brazilian agencies CAPES, Finep and Fapesp (Project FINEP 01.10.0661-00, FAPESP 2011/13250-0, FAPESP 2013/17247-9, FAPESP 2014/05975-2, CAPES 88887068264/2014-00), of Institute of Research and Development, University of Vale Paraíba
NN,N\Delta Couplings and the Quark Model
We examine mass-corrected SU(6) symmetry predictions in the quark model
relating vector, axial-vector and strong NN and N\Delta couplings, and
demonstrate that the experimental N\Delta value is significantly higher than
predicted in each case. Nevertheless the Goldberger-Treiman relation is
satisfied in both sectors. Possible origins of the discrepancy of the quark
model predictions with experiment are discussed.Comment: 22 pg. Latex file, figures available by reques
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