18,553 research outputs found
Some aspects of analytical chemistry as applied to water quality assurance techniques for reclaimed water: The potential use of X-ray fluorescence spectrometry for automated on-line fast real-time simultaneous multi-component analysis of inorganic pollutants in reclaimed water
The potential use of isotopically excited energy dispersive X-ray fluorescence (XRF) spectrometry for automated on line fast real time (5 to 15 minutes) simultaneous multicomponent (up to 20) trace (1 to 10 parts per billion) analysis of inorganic pollutants in reclaimed water was examined. Three anionic elements (chromium 6, arsenic and selenium) were studied. The inherent lack of sensitivity of XRF spectrometry for these elements mandates use of a preconcentration technique and various methods were examined, including: several direct and indirect evaporation methods; ion exchange membranes; selective and nonselective precipitation; and complexation processes. It is shown tha XRF spectrometry itself is well suited for automated on line quality assurance, and can provide a nondestructive (and thus sample storage and repeat analysis capabilities) and particularly convenient analytical method. Further, the use of an isotopically excited energy dispersive unit (50 mCi Cd-109 source) coupled with a suitable preconcentration process can provide sufficient sensitivity to achieve the current mandated minimum levels of detection without the need for high power X-ray generating tubes
Worldliness: how do we live with others? Universality-as-multiplicity
The ifa conference "Cultures of We" held on 13 September 2017 in Berlin cut to the core of world politics today. It asked: How can we stay true to the principle of equality, as enshrined in the Universal Declaration of Human Rights (UDHR), when "othering" has resurged in identity and politics validated by a newly-vocal narrative of "us versus them?" Populist movements formalized by Brexit in the United Kingdom in June 2016 and the election of Donald J. Trump to the US presidency five months later march in lock-step with other racist-nationalist regimes in the Philippines, Turkey, Austria, and so on. Many pockets of Scandinavia, previously models of liberal tolerance, also exhibit similar sympathies. Renewed commitment to the UDHR will not suffice, I’m afraid. Its insistence on singularity to convey universality sinks the proposition
Quantum contextuality for a relativistic spin-1/2 particle
The quantum predictions for a single nonrelativistic spin-1/2 particle can be
reproduced by noncontextual hidden variables. Here we show that quantum
contextuality for a relativistic electron moving in a Coulomb potential
naturally emerges if relativistic effects are taken into account. The
contextuality can be identified through the violation of noncontextuality
inequalities. We also discuss quantum contextuality for the free Dirac electron
as well as the relativistic Dirac oscillator.Comment: REVTeX4, 5 page
Operator-sum representation of time-dependent density operators and its applications
We show that any arbitrary time-dependent density operator of an open system
can always be described in terms of an operator-sum representation regardless
of its initial condition and the path of its evolution in the state space, and
we provide a general expression of Kraus operators for arbitrary time-dependent
density operator of an -dimensional system. Moreover, applications of our
result are illustrated through several examples.Comment: 4 pages, no figure, brief repor
Orbital symmetry fingerprints for magnetic adatoms in graphene
In this paper, we describe the formation of local resonances in graphene in
the presence of magnetic adatoms containing localized orbitals of arbitrary
symmetry, corresponding to any given angular momentum state. We show that
quantum interference effects which are naturally inbuilt in the honeycomb
lattice in combination with the specific orbital symmetry of the localized
state lead to the formation of fingerprints in differential conductance curves.
In the presence of Jahn-Teller distortion effects, which lift the orbital
degeneracy of the adatoms, the orbital symmetries can lead to distinctive
signatures in the local density of states. We show that those effects allow
scanning tunneling probes to characterize adatoms and defects in graphene.Comment: 15 pages, 11 figures. Added discussion about the multi-orbital case
and the validity of the single orbital picture. Published versio
Matter-wave bistability in coupled atom-molecule quantum gases
We study the matter-wave bistability in coupled atom-molecule quantum gases,
in which heteronuclear molecules are created via an interspecies Feshbach
resonance involving either two-species Bose or two-species Fermi atoms at zero
temperature. We show that the resonant two-channel Bose model is equivalent to
the nondegenerate parametric down-conversion in quantum optics, while the
corresponding Fermi model can be mapped to a quantum optics model that
describes a single-mode laser field interacting with an ensemble of
inhomogeneously broadened two-level atoms. Using these analogy and the fact
that both models are subject to the Kerr nonlinearity due to the two-body
s-wave collisions, we show that under proper conditions, the population in the
molecular state in both models can be made to change with the Feshbach detuning
in a bistable fashion.Comment: 6 pages, 5 figure
Multi-Component Bell Inequality and its Violation for Continuous Variable Systems
Multi-component correlation functions are developed by utilizing d-outcome
measurements. Based on the multi-component correlation functions, we propose a
Bell inequality for bipartite d-dimensional systems. Violation of the Bell
inequality for continuous variable (CV) systems is investigated. The violation
of the original Einstein-Podolsky-Rosen state can exceed the Cirel'son bound,
the maximal violation is 2.96981. For finite value of squeezing parameter,
violation strength of CV states increases with dimension d. Numerical results
show that the violation strength of CV states with finite squeezing parameter
is stronger than that of original EPR state.Comment: 5 pages and 1 figure, rewritten version, accepted by Phys. Rev.
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