2,417 research outputs found
The contamination status of trace metals in Sinop coast of the Black Sea, Turkey
The concentration of some heavy metals in sediment from the Sinop coasts of the Black Sea were measured to monitor metal pollution in 2013. The distribution of the heavy metals in sediments of the Black Sea shows a variable pattern. The objectives of the present study were to elucidate the distribution of heavy metals such as Cu, Pb, Zn, Ni, Mn, Fe, As, Cd, Cr, Hg and Co in sediment from Sinop coast of the Black Sea. In order to determine the quality of sediment in the Black Sea, pollution levels of the metals were evaluated using the enrichment factor technique (EF). The lowest EF values were between 0-5 in Cu, Fe, Zn, Ni, Cd, Pb, Mn and Co. These values did not have statistically significant differences. As, Cr and Hg concentrations were estimated relatively higher enrichment values than other the metals. The results indicated that contamination of surface sediments in Sinop Coast is dominated by As (10.2-7.4 mg.kg-1), Cr (67-374 mg.kg-1) and Hg (0.07-0.03 mg.kg-1) and to a lesser extent Cu (7.24- 5.09 mg.kg-1), Fe (1.76-1.12%), Zn (19.3-13.8 mg.kg-1), Ni (16.2-12.5 mg.kg-1), Cd (0.06-0.04 mg.kg-1), Pb (7.12-6.32 mg.kg-1), Mn (470-227 mg.kg-1), Co (9.5-5.9 mg.kg-1). Also, the requirement of age determination is of great importance to assess the extent of the anthropogenic contribution in pollution
Can Electric Field Induced Energy Gaps In Metallic Carbon Nanotubes?
The low-energy electronic structure of metallic single-walled carbon nanotube
(SWNT) in an external electric field perpendicular to the tube axis is
investigated. Based on tight-binding approximation, a field-induced energy gap
is found in all (n, n) SWNTs, and the gap shows strong dependence on the
electric field and the size of the tubes. We numerically find a universal
scaling that the gap is a function of the electric field and the radius of
SWNTs, and the results are testified by the second-order perturbation theory in
weak field limit. Our calculation shows the field required to induce a 0.1
gap in metallic SWNTs can be easily reached under the current
experimental conditions. It indicates a kind of possibility to apply nanotubes
to electric signal-controlled nanoscale switching devices
Probabilistic teleportation and entanglement matching
Teleportation may be taken as sending and extracting quantum information
through quantum channels. In this report, it is shown that to get the maximal
probability of exact teleportation through partially entangled quantum
channels, the sender (Alice) need only to operate a measurement which satisfy
an ``entanglement matching'' to this channel. An optimal strategy is also
provided for the receiver (Bob) to extract the quantum information by adopting
general evolutions.Comment: 3.5 pages, No figure
Green Function on the q-Symmetric Space SU_q(2)/U(1)
Following the introduction of the invariant distance on the non-commutative
C-algebra of the quantum group SU_q(2), the Green function and the Kernel on
the q-homogeneous space M=SU(2)_q/U(1) are derived. A path integration is
formulated. Green function for the free massive scalar field on the
non-commutative Einstein space R^1xM is presented.Comment: Plain Latex, 19
Numerical observation of non-axisymmetric vesicles in fluid membranes
By means of Surface Evolver (Exp. Math,1,141 1992), a software package of
brute-force energy minimization over a triangulated surface developed by the
geometry center of University of Minnesota, we have numerically searched the
non-axisymmetric shapes under the Helfrich spontaneous curvature (SC) energy
model. We show for the first time there are abundant mechanically stable
non-axisymmetric vesicles in SC model, including regular ones with intrinsic
geometric symmetry and complex irregular ones. We report in this paper several
interesting shapes including a corniculate shape with six corns, a
quadri-concave shape, a shape resembling sickle cells, and a shape resembling
acanthocytes. As far as we know, these shapes have not been theoretically
obtained by any curvature model before. In addition, the role of the
spontaneous curvature in the formation of irregular crenated vesicles has been
studied. The results shows a positive spontaneous curvature may be a necessary
condition to keep an irregular crenated shape being mechanically stable.Comment: RevTex, 14 pages. A hard copy of 8 figures is available on reques
Spatial Current Patterns, Dephasing and Current Imaging in Graphene Nanoribbons
Using the non-equilibrium Keldysh Green's function formalism, we investigate
the local, non-equilibrium charge transport in graphene nanoribbons (GNRs). In
particular, we demonstrate that the spatial current patterns associated with
discrete transmission resonances sensitively depend on the GNRs' geometry,
size, and aspect ratio, the location and number of leads, and the presence of
dephasing. We identify a relation between the spatial form of the current
patterns, and the number of degenerate energy states participating in the
charge transport. Furthermore, we demonstrate a principle of superposition for
the conductance and spatial current patterns in multiple-lead configurations.
We demonstrate that scanning tunneling microscopy (STM) can be employed to
image spatial current paths in GNR with atomic resolution, providing important
insight into the form of local charge transport. Finally, we investigate the
effects of dephasing on the spatial current patterns, and show that with
decreasing dephasing time, the current patterns evolve smoothly from those of a
ballistic quantum network to those of classical resistor network.Comment: 25 pages, 12 figure
Polarization of Radiation in Multipole Jaynes-Cummings Model
We discuss the spatial properties of quantum radiation emitted by a multipole
transition in a single atom. The qualitative difference between the
representations of plane and spherical waves of photons is examined. In
particular, the spatial inhomogeneity of the zero-point oscillations of
multipole field is shown. We show that the vacuum noise of polarization is
concentrated in a certain vicinity of atoms where it strongly exceeds the level
predicted by the representation of the plane waves. A new general polarization
matrix is proposed. It is shown that the polarization and its vacuum noise
strongly depend on the distance from the source.Comment: 23 pages, 3 figure
Quantum key distribution via quantum encryption
A quantum key distribution protocol based on quantum encryption is presented
in this Brief Report. In this protocol, the previously shared
Einstein-Podolsky-Rosen pairs act as the quantum key to encode and decode the
classical cryptography key. The quantum key is reusable and the eavesdropper
cannot elicit any information from the particle Alice sends to Bob. The concept
of quantum encryption is also discussed.Comment: 4 Pages, No Figure. Final version to appear in PR
Squeezing and entanglement in continous variable systems
Based on total variance of a pair of Einstein-Podolsky-Rosen (EPR) type
operators, the generalized EPR entangled states in continuous variable systems
are defined. We show that such entangled states must correspond with two-mode
squeezing states whether these states are Gaussian or not and whether they are
pure or not. With help of the relation between the total variance and the
entanglement, the degree of such entanglement is also defined. Through
analyzing some specific cases, we see that this method is very convenient and
easy in practical application. In addition, an entangled state with no
squeezing is studied, which reveals that there certainly exist something
unknown about entanglement in continuous variable systems.Comment: 5 page
Searching for Multijet Resonances at the LHC
Recently it was shown that there is a class of models in which colored vector
and scalar resonances can be copiously produced at the Tevatron with decays to
multijet final states, consistent with all experimental constraints and having
strong discovery potential. We investigate the collider phenomenology of TeV
scale colored resonances at the LHC and demonstrate a strong discovery
potential for the scalars with early data as well as the vectors with
additional statistics. We argue that the signal can be self-calibrating and
using this fact we propose a search strategy which we show to be robust to
systematic errors typically expected from Monte Carlo background estimates. We
model the resonances with a phenomenological Lagrangian that describes them as
bound states of colored vectorlike fermions due to new confining gauge
interactions. However, the phenomenological Lagrangian treatment is quite
general and can represent other scenarios of microscopic physics as well.Comment: 28 pages, 13 figures, pdflatex. Discussion of background expanded,
minor modifications made. Version to appear in JHE
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