7,333 research outputs found
Incoherent control and entanglement for two-dimensional coupled systems
We investigate accessibility and controllability of a quantum system S
coupled to a quantum probe P, both described by two-dimensional Hilbert spaces,
under the hypothesis that the external control affects only P. In this context
accessibility and controllability properties describe to what extent it is
possible to drive the state of the system S by acting on P and using the
interaction between the two systems. We give necessary and sufficient
conditions for these properties and we discuss the relation with the entangling
capability of the interaction between S and P. In particular, we show that
controllability can be expressed in terms of the SWAP operator, acting on the
composite system, and its square root.Comment: Latex, 13 page
Multiscale models of colloidal dispersion of particles in nematic liquid crystals
We use homogenization theory to develop a multiscale model of colloidal dispersion of particles in nematic liquid crystals under weak-anchoring conditions. We validate the model by comparing it with simulations by using the Landau–de Gennes free energy and show that the agreement is excellent. We then use the multiscale model to study the effect that particle anisotropy has on the liquid crystal: spherically symmetric particles always reduce the effective elastic constant. Asymmetric particles introduce an effective alignment field that can increase the Fredericks threshold and decrease the switch-off time
Development of an innovative method for the evaluation of fungal contamination of surfaces
The objective of this technical report is to compare the ability to capture fungal spores through samples performed with three different methods: Rodac contact plates, cotton pad and a pad prepared with a dusting cloth (DC pads) selected from those available on the market. The tests were conducted using a suspension of Aspergillus niger conidia equal to 0.5 MacFarland diluted 1/30, 1/40, 1/50, 1/100. With each of these dilutions 3 sterile tiles of stainless steel were contaminated, each divided into 16 small squares, in the center of which 0.1 ml of the dilution chosen was placed and left to dry (for a total of 12 sheets). In addition, we have used other 6 tiles to repeat the experience with dilutions 1/40 and 1/50. A total of 288 squared surfaces were contaminated: 96 of these were sampled with Rodac contact plates, 96 with cotton pads and 96 with DC and then inseminated in Petri plates. Sabouraud dextrose agar was used as culture medium for the first 12 plates, while, for the other 6 plates Sabouraud dextrose agar added with lecithin and polysorbate 80 was used. All plates were incubated at 37 degrees for 18 hours. To estimate the differences among the sampling methods and the dilutions tested, multiple linear regression was used. The analysis showed that the number of colonies harvested at dilution 1/40 is 13% higher (P = 0.09) than the number harvested at dilution 1/50 and the number of colonies harvested at dilution 1/30 is 6% higher than dilution 1/50 (P = 0.52). With regard to the comparison between the number of colonies harvested with Rodac contact plates, with cotton pads and DC pads, regression analysis shows that cotton pads harvest a number of fungal cfu 5 times higher than those detected with Rodac plates, while DC pads harvest a number of fungal ufc 6 times higher than those detected with Rodac plates (P < 0.00005). These results, although preliminary, indicate that DC pads are a sensitive and simple approach for the environmental control of fungal contamination
Surviving on Mars: test with LISA simulator
We present the biological results of some experiments performed in the Padua
simulators of planetary environments, named LISA, used to study the limit of
bacterial life on the planet Mars. The survival of Bacillus strains for some
hours in Martian environment is shortly discussed.Comment: To be published on Highlights of Astronomy, Volume 15 XXVIIth IAU
General Assembly, August 2009 Ian F Corbett, ed. 2 pages, 1 figur
A General Framework for Recursive Decompositions of Unitary Quantum Evolutions
Decompositions of the unitary group U(n) are useful tools in quantum
information theory as they allow one to decompose unitary evolutions into local
evolutions and evolutions causing entanglement. Several recursive
decompositions have been proposed in the literature to express unitary
operators as products of simple operators with properties relevant in
entanglement dynamics. In this paper, using the concept of grading of a Lie
algebra, we cast these decompositions in a unifying scheme and show how new
recursive decompositions can be obtained. In particular, we propose a new
recursive decomposition of the unitary operator on qubits, and we give a
numerical example.Comment: 17 pages. To appear in J. Phys. A: Math. Theor. This article replaces
our earlier preprint "A Recursive Decomposition of Unitary Operators on N
Qubits." The current version provides a general method to generate recursive
decompositions of unitary evolutions. Several decompositions obtained before
are shown to be as a special case of this general procedur
PIXE and ToF-SIMS analysis of streaker samplers filters
This paper presents methodological innovations introduced in the characterisation of urban aerosol collected in Italy in a recent campaign. Two complementary ion beam analysis (IBA) techniques were used to analyse Nuclepore filters used in continuous streaker samplers to collect airborne particles in four Italian towns. Na to Pb elemental concentrations were obtained by particle induced X-ray emission (PIXE), while time of flight secondary ion mass spectrometry (ToF-SIMS) produced, on the same samples, time trends for several elements and molecular fragments. In addition, light attenuation measurements were used as a tracer for black carbon. The data produced by these three techniques was merged into a unique data set to address the characterisation of particulate matter sources. Correlations between elemental concentration trends (PIXE) and relative trends for molecular fragments (ToF-SIMS) and black carbon (light attenuation) have been studied by cluster and principal component analysis
MARINE AND NORMARINE TRACE FOSSILS AND PLANT ROOTS IN A REGRESSIONAL SETTING (PLEISTOCENE, ITALY)
The sedimentary structures occurring in one of the Pleistocene marine terraces at the Ionian coast, indicate a shoaling upward trend from the shoreface of a sandy beach to nonmarine conditions. Four main facies have been recognized. Facies A consists of hummocky cross-bedded sands representing a wave-dominated nearshore environment. Physical and biological structures of facies B are suggestive of an abrupt reduction in energy level, possibly related to the establishment of shallow protected environments. Features of facies C suggest a stable environment of upper shoreface but strongly influenced by continental supplies. Upward, this facies passes into sediments deposited in continental conditions. The last facies (D) is related to moist or wet terrestrial environments. Bioturbation levels of facies A to C are in general low. Facies D, however, is well bioturbated, having an ichnofabric dominated by Taenidium isp. Sparse, vertical roots of vascular plants extended in many cases to at least 3 m below the base of facies D. Particularly unusual is the close association of large Taenidium isp. and vertical roots, where the trace fossil is clustered tightly around the plant, in some cases to more than 1 m below the water-sediment interface
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