Investigation of dielectric properties of LixNa₁₋xNbO₃ ceramics for x = 1 and x=4

The a.c. electrical response of LixNa₁₋xNbO₃ (LNN) solid solution in low frequency range (100 Hz–20 kHz) has been analysed as a function of temperature (300 K–750 K). A complex picture of the dependence of the studied properties on the chemical composition has been obtained. The data indicate the presence of relaxation and transport processes as well as their thermally activated character.Досліджено електричний відгук в змінному полі твердих розчинів LixNa₁₋xNbO₃ (LNN) як функцію температури (300 K–750 K) в низькочастотній області (100 Hz–20 kHz). Отримано комплексну картину залежності досліджених величин від хімічного складу. Отримані дані свідчать про наявність релаксаційних і транспортних процесів та про тепловий характер їх активації

Spin-Boson Hamiltonian and Optical Absorption of Molecular Dimers

An analysis of the eigenstates of a symmetry-broken spin-boson Hamiltonian is performed by computing Bloch and Husimi projections. The eigenstate analysis is combined with the calculation of absorption bands of asymmetric dimer configurations constituted by monomers with nonidentical excitation energies and optical transition matrix elements. Absorption bands with regular and irregular fine structures are obtained and related to the transition from the coexistence to a mixing of adiabatic branches in the spectrum. It is shown that correlations between spin states allow for an interpolation between absorption bands for different optical asymmetries.Comment: 15 pages, revTeX, 8 figures, accepted for publication in Phys. Rev.

Which assessment tools address the categories of the Brief ICF Core Set for Hand Conditions?

Introduction The purpose of this study was to explore whether assessment tools address aspects that are relevant according to the Brief ICF Core Set for Hand Conditions (BICF-CS). Methods Assessment tools meant to assess functioning and/or environmental factors in adults with hand conditions were reviewed. MEDLINE and CINAHL databases, previously published reviews, the book Clinical Assessment Recommendations of the ASHT, and websites of assessment tools were used for the content comparison and linking to the 23 categories of the BICF-CS. The updated version of the linking rules was applied by two reviewers. Results Forty-six assessment tools, known within the areas of hand therapy and hand surgery, were linked to the 23 categories of the BICF-CS. Regarding Body functions and body structures, the categories that were most frequently addressed were b730 “Muscle power functions,” b280 “Sensation of pain,” b710 “Mobility of joint functions,” and s730 “Structure of upper extremity.” Regarding Activities and Participation, d440 “Fine hand use” was addressed mostly and 25 assessment tools (with a total of 146 items) were linked to this category. Regarding Environmental Factors, only one assessment tool was identified that could be linked to two categories. Fifteen points of discussion were encountered in the linking process. Conclusions Content comparison of 46 assessment tools revealed that 19 of the 23 categories of the BICF-CS were addressed. The environmental factors were hardly addressed

AGN and starbursts at high redshift: High resolution EVN radio observations of the Hubble Deep Field

We present deep, wide-field European VLBI Network (EVN) 1.6 GHz observations of the Hubble Deep Field (HDF) region with a resolution of 0.025 arcseconds. Above the 210 microJy/beam (5sigma) detection level, the EVN clearly detects two radio sources in a field that encompasses the HDF and part of the Hubble Flanking Fields (HFF). The sources detected are: VLA J123644+621133 (a z=1.013, low-luminosity FR-I radio source located within the HDF itself) and VLA J123642+621331 (a dust enshrouded, optically faint, z=4.424 starburst system). A third radio source, J123646+621404, is detected at the 4sigma level. The VLBI detections of all three sources suggest that most of the radio emission of these particular sources (including the dusty starburst) is generated by an embedded AGN.Comment: 4 pages, 1 figure; Accepted by Astron. & Astrophys Letters ... See http://www.nfra.nl/~mag/hdf_evn.htm

Renyi-Wehrl entropies as measures of localization in phase space

We generalize the concept of the Wehrl entropy of quantum states which gives a basis-independent measure of their localization in phase space. We discuss the minimal values and the typical values of these R{enyi-Wehrl entropies for pure states for spin systems. According to Lieb's conjecture the minimal values are provided by the spin coherent states. Though Lieb's conjecture remains unproven, we give new proofs of partial results that may be generalized for other systems. We also investigate random pure states and calculate the mean Renyi-Wehrl entropies averaged over the natural measure in the space of pure quantum states.Comment: 18 pages, no figures, some improved versions of main proofs, added J.referenc

Survey of Planetary Nebulae at 30 GHz with OCRA-p

We report the results of a survey of 442 planetary nebulae at 30 GHz. The purpose of the survey is to develop a list of planetary nebulae as calibration sources which could be used for high frequency calibration in future. For 41 PNe with sufficient data, we test the emission mechanisms in order to evaluate whether or not spinning dust plays an important role in their spectra at 30 GHz. The 30-GHz data were obtained with a twin-beam differencing radiometer, OCRA-p, which is in operation on the Torun 32-m telescope. Sources were scanned both in right ascension and declination. We estimated flux densities at 30 GHz using a free-free emission model and compared it with our data. The primary result is a catalogue containing the flux densities of 93 planetary nebulae at 30 GHz. Sources with sufficient data were compared with a spectral model of free-free emission. The model shows that free-free emission can generally explain the observed flux densities at 30 GHz thus no other emission mechanism is needed to account for the high frequency spectra.Comment: 10 pages, 7 Postscript figures, to be published in A&

Geometry of the 3-Qubit State, Entanglement and Division Algebras

We present a generalization to 3-qubits of the standard Bloch sphere representation for a single qubit and of the 7-dimensional sphere representation for 2 qubits presented in Mosseri {\it et al.}\cite{Mosseri2001}. The Hilbert space of the 3-qubit system is the 15-dimensional sphere $S^{15}$, which allows for a natural (last) Hopf fibration with $S^8$ as base and $S^7$ as fiber. A striking feature is, as in the case of 1 and 2 qubits, that the map is entanglement sensitive, and the two distinct ways of un-entangling 3 qubits are naturally related to the Hopf map. We define a quantity that measures the degree of entanglement of the 3-qubit state. Conjectures on the possibility to generalize the construction for higher qubit states are also discussed.Comment: 12 pages, 2 figures, final versio

Transition from antibunching to bunching for two dipole-interacting atoms

It is known that there is a transition from photon antibunching to bunching in the resonance fluorescence of a driven system of two two-level atoms with dipole-dipole interaction when the atomic distance decreases and the other parameters are kept fixed. We give a simple explanation for the underlying mechanism which in principle can also be applied to other systems. PACS numbers 42.50.Ar, 42.50FxComment: Submitted to Phys. Rev. A; 15 pages Latex + 4 figure