14,405 research outputs found
Reproducibility of electrical caries measurements: A technical problem?
The currently available instrument for electrical detection of occlusal caries lesions {[}Electronic Caries Monitor (ECM)] uses a site-specific measurement with co-axial air drying. The reproducibility of this method has been reported to be fair to good. It was noticed that the measurement variation of this technique appeared to be non-random. It was the aim of this study to analyse how such a non-random reproducibility pattern arises and whether it could be observed for other operators and ECM models. Analysis of hypothetical measurement pairs showed that the pattern was related to measurements at the high and low end of the measurement range for the instrument. Data sets supplied by other researchers to a varying degree showed signs of a similar non-random pattern. These data sets were acquired at different locations, by different operators and using 3 different ECM models. The frequency distribution of measurements in all cases showed a single or double end-peaked distribution shape. It was concluded that the pattern was a general feature of the measurement method. It was tentatively attributed to several characteristics such as a high value censoring, insufficient probe contact and unpredictable probe contact. A different measurement technique, with an improved probe contact, appears to be advisable. Copyright (C) 2005 S. Karger AG, Basel
Understanding the agglomeration behavior of nickel laterite and gold ores using statistical design of experiments
pre-printThe drum agglomeration of nickel laterite and gold ores has been optimized through the design of experiments (DOE) using a Taguchi L16 (45) orthogonal array to determine the optimum conditions for maximizing average agglomerate size and minimizing the amount of fines. The effects of controllable operating factors including moisture content (nickel laterite ore: 34-37%; gold ore: 7-10%), retention time (2-3.5 min), drum speed (15-45% critical speed), drum load (nickel laterite ore: 8-32 %; gold ore: 6-22%) and acid concentration (150-600 g/L) on the performance of the agglomeration process were studied. For nickel laterite ore, maximum average agglomerate size and minimum percent fines (-1 mm) occurred under the following conditions: drum load (23.7%), moisture (36.5%), time (3 min), drum speed (30% critical speed) and acid concentration (150 g/L). Under the studied nickel laterite ore conditions, the most effective parameters for maximizing average agglomerate size and minimizing the amount of fines were found to be drum load and acid concentration, respectively. Drum speed had a statistically significant effect on minimizing the amount of fines. Maximum average agglomerate size and minimum percent fines (-1 mm) for gold ore occurred under the following conditions: drum load (19.3%), moisture (8.5%), time (2 min 15 s) and drum speed (40% critical). The most significant factors for maximizing average agglomerate size and minimizing the amount of fines for gold ore were found to be drum load, time and moisture
Several experimental realizations of symmetric phase-covariant quantum cloner of single-photon qubits
We compare several optical implementations of phase-covariant cloning
machines. The experiments are based on copying of the polarization state of a
single photon in bulk optics by special unbalanced beam splitter or by balanced
beam splitter accompanied by a state filtering. Also the all-fiber based setup
is discussed, where the information is encoded into spatial modes, i.e., the
photon can propagate through two optical fibers. Each of the four
implementations possesses some advantages and disadvantages that are discussed.Comment: 8 pages, 11 figure
Inaccurate clinical nodal staging of non-small-cell lung cancer: evidence fro mthe MRC LU22 multicentre randomised trial
Flotation chemistry and technology of nonsulfide minerals
Book ChapterThe dimensions of nonsulfide flotation technology extend in many directions, as might be expected from the diversity of the mineral classes, which include soluble salt minerals (potash, borax, and trona), semisoluble salt minerals (phosphate minerals, fluorite, calcite, and barite), and insoluble oxides/silicate minerals (iron oxide minerals, rutile, mica, quartz, and feldspar). Consequently, some flotation separations are accomplished from saturated brine, though other separations are achieved in solutions of rather low ionic strength. Also, certain nonsulfide minerals are naturally hydrophobic, such as talc, graphite, and coal. However, in general, the nonsulfide minerals are hydrophilic and require relatively high levels of collector addition on the order of 1 lb/ton to establish a hydrophobic surface state. In addition, the nonsulfide collectors generally are anionic or cationic surfactants, having hydrocarbon chains of 10 carbon atoms or greater. In many instances, the collector is sufficiently insoluble so that a distinct collector phase is present in the system, existing as a liquid dispersion or as a collector colloid. This situation further complicates the analysis of nonsulfide flotation chemistry. Thus, in some cases, the hydrophobic surface state is created by the adsorption of water-soluble collector species, though in others, the hydrophobic surface state is created by the wetting/spreading of insoluble collector oils or by the attachment of insoluble collector colloids. In view of the foregoing, it is evident that the flotation chemistry of nonsulfide minerals is distinctly different from the flotation chemistry/electrochemistry of sulfide minerals
Low rank positive partial transpose states and their relation to product vectors
It is known that entangled mixed states that are positive under partial
transposition (PPT states) must have rank at least four. In a previous paper we
presented a classification of rank four entangled PPT states which we believe
to be complete. In the present paper we continue our investigations of the low
rank entangled PPT states. We use perturbation theory in order to construct
rank five entangled PPT states close to the known rank four states, and in
order to compute dimensions and study the geometry of surfaces of low rank PPT
states. We exploit the close connection between low rank PPT states and product
vectors. In particular, we show how to reconstruct a PPT state from a
sufficient number of product vectors in its kernel. It may seem surprising that
the number of product vectors needed may be smaller than the dimension of the
kernel.Comment: 29 pages, 4 figure
Hydrogen bonding in substituted nitroanilines : isolated nets in 1,3-diamino-4-nitrobenzene and continuously interwoven nets in 3,5-dinitroaniline
Peer reviewedPublisher PD
Coordinate representation of particle dynamics in AdS and in generic static spacetimes
We discuss the quantum dynamics of a particle in static curved spacetimes in
a coordinate representation. The scheme is based on the analysis of the squared
energy operator E^2, which is quadratic in momenta and contains a scalar
curvature term. Our main emphasis is on AdS spaces, where this term is fixed by
the isometry group. As a byproduct the isometry generators are constructed and
the energy spectrum is reproduced. In the massless case the conformal symmetry
is realized as well. We show the equivalence between this quantization and the
covariant quantization, based on the Klein-Gordon type equation in AdS. We
further demonstrate that the two quantization methods in an arbitrary
(N+1)-dimensional static spacetime are equivalent to each other if the scalar
curvature terms both in the operator E^2 and in the Klein-Gordon type equation
have the same coefficient equal to (N-1)/(4N).Comment: 14 pages, no figures, typos correcte
Experimental asymmetric phase-covariant quantum cloning of polarization qubits
We report on two optical realizations of the asymmetric
phase-covariant cloning machines for polarization states of single photons. The
experimental setups combine two-photon interference and tunable polarization
filtering that enables us to control the asymmetry of the cloners. The first
scheme involves a special unbalanced bulk beam splitter exhibiting different
splitting ratios for vertical and horizontal polarizations, respectively. The
second implemented scheme consists of a balanced fiber coupler where photon
bunching occurs, followed by a free-space part with polarization filters. With
this later approach we were able to demonstrate very high cloning fidelities
which are above the universal cloning limit.Comment: 7 pages, 8 figure
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