Spin projection chromatography

We formulate the many-body spin dynamics at high temperature within the non-equilibrium Keldysh formalism. For the simplest XY interaction, analytical expressions in terms of the one particle solutions are obtained for linear and ring configurations. For small rings of even spin number, the group velocities of excitations depend on the parity of the total spin projection. This should enable a dynamical filtering of spin projections with a given parity i.e. a Spin projection chromatography.Comment: 13 pages, 3 figure

Concentrations of some toxic and trace elements in wild boar (Sus scrofa) organs and tissues in different areas of the Province of Viterbo, Central Italy

The aim of the present study was to determine heavy metal reference levels for exposure and risk assessment studies on a local scale. We measured lead (Pb), chromium (Cr), zinc (Zn), copper (Cu) and cadmium (Cd) content in edible tissues and organs of wild boars harvested in dif- ferent areas of the Province of Viterbo, Central Italy. The average levels of cadmium recorded in 75 wild boars were 0.085, 0.079 and 1.052 mg Cd kg–1 wet weight (w.w.) in the liver, muscle and kidney, respectively. The majority of the muscle samples and some of the liver samples contained levels of heavy metal that were over the legal limit [EU Maximum Residue Levels (MRLs)] for pigs. Our data are similar to or lower than the val- ues reported in most of the available literature. For Pb concentration, the average values record- ed were 0.318, 0.126 and 0.298 mg kg–1 w.w. in the liver, muscle and kidney, respectively. The sam- ples that were non-compliant with regulatory limits (MRLs) for pigs were registered only for muscle. Available data on the presence of Pb con- tent in game meat report lower values than ours, most likely because the area around the bullet path was avoided while sampling. The average values of total Cr were 0.141, 0.139 and 0.097 mg kg–1 w.w. in the liver, muscle and kidney, respec- tively. For Zn, the mean values were 49.76, 53.21 and 32.46 mg kg–1 w.w. in the liver, muscle and kidney, respectively. Cu content was 46.12, 12.20 and 5.64 mg Cu kg–1 w.w. in the liver, muscle and kidney, respectively. The results obtained have been validated on the basis of the scarce and inconsistent Italian literature available and on international studies

Decoherence as attenuation of mesoscopic echoes in a spin-chain channel

An initial local excitation in a confined quantum system evolves exploring the whole system, returning to the initial position as a mesoscopic echo at the Heisenberg time. We consider a two weakly coupled spin chains, a spin ladder, where one is a quantum channel while the other represents an environment. We quantify decoherence in the quantum channel through the attenuation of the mesoscopic echoes. We evaluate decoherence rates for different ratios between sources of amplitude fluctuation and dephasing in the inter-chain interaction Hamiltonian. The many-body dynamics is seen as a one-body evolution with a decoherence rate given by the Fermi golden rule.Comment: 12 pages, 7 figure

Quantum parallelism as a tool for ensemble spin dynamics calculations

Efficient simulations of quantum evolutions of spin-1/2 systems are relevant for ensemble quantum computation as well as in typical NMR experiments. We propose an efficient method to calculate the dynamics of an observable provided that the initial excitation is "local". It resorts a single entangled pure initial state built as a superposition, with random phases, of the pure elements that compose the mixture. This ensures self-averaging of any observable, drastically reducing the calculation time. The procedure is tested for two representative systems: a spin star (cluster with random long range interactions) and a spin ladder.Comment: 5 pages, 3 figures, improved version of the manuscrip

A multipurpose leguminous plant for the mediterranean countries: Leucaena leucocephala as an alternative protein source: a review

SIMPLE SUMMARY: The need to address the shortage of protein ingredients linked to both territoriality and growing demand pushes research to focus attention on alternative protein sources, both vegetable and animal (insects). This review describes the characteristics, uses, strengths, and weaknesses of Leucaena leucocephala, a legume that can be used in the zootechnical field as an alternative to traditional protein sources for feed formulation. ABSTRACT: In tropical and subtropical regions, as well as in the internal and/or marginal Mediterranean areas, one of the most important problems related to animal production is represented by the inadequate nutritional supplies. The low productivity of the animals, often connected to reduced annual growth, is, in fact, not infrequently attributable to the low nitrogen content and the high fiber content of the local plant species and crop residues that constitute the base ingredients of the rations commonly adopted by farmers. The use of the supplementation with arboreal and shrub fodder, although often containing anti-nutritional factors and toxins that limit its use, could be a profitable way to alleviate the nutritional deficiencies of the basic diets. Leucaena leucocephala (Lam.) De Wit is native to Central America and widely naturalized in the majority of Latin American countries. It is a legume suitable for tropical and subtropical environments including the countries of the Mediterranean area. Moreover, its spread is desirable if we consider the multiple uses to which it is suitable, the considerable amount of biomass produced, and its role in preserving the environment. The aim of this work was to highlight the characteristics of Leucaena that can justify its wide diffusion. A structured analysis of strengths and weaknesses was performed accordingly. Being a good protein source for feeding livestock, it could be a species to be introduced in the inland areas of the Mediterranean countries as an alternative protein source; the limit represented by the presence of anti-nutritional factors could be overcome by feed processing and by launching targeted research programs

Environmentally induced Quantum Dynamical Phase Transition in the spin swapping operation

Quantum Information Processing relies on coherent quantum dynamics for a precise control of its basic operations. A swapping gate in a two-spin system exchanges the degenerate states |+,-> and |-,+>. In NMR, this is achieved turning on and off the spin-spin interaction b=\Delta E that splits the energy levels and induces an oscillation with a natural frequency \Delta E/\hbar. Interaction of strength \hbar/\tau_{SE}, with an environment of neighboring spins, degrades this oscillation within a decoherence time scale \tau_{\phi}. While the experimental frequency \omega and decoherence time \tau_{\phi} were expected to be roughly proportional to b/\hbar and \tau_{SE} respectively, we present here experiments that show drastic deviations in both \omega and \tau_{\phi}. By solving the many spin dynamics, we prove that the swapping regime is restricted to \Delta E \tau_{SE} > \hbar. Beyond a critical interaction with the environment the swapping freezes and the decoherence rate drops as 1/\tau_{\phi} \propto (b/\hbar)^2 \tau_{SE}. The transition between quantum dynamical phases occurs when \omega \propto \sqrt{(b/\hbar)^{2}-(k/\tau_{SE})^2} becomes imaginary, resembling an overdamped classical oscillator. Here, 0<k^2<1 depends only on the anisotropy of the system-environment interaction, being 0 for isotropic and 1 for XY interactions. This critical onset of a phase dominated by the Quantum Zeno effect opens up new opportunities for controlling quantum dynamics.Comment: Final version. One figure and some equations corrected, 10 pages, 4 figure

particle size evaluation of total mixed rations in intensive beef production systems

AbstractSamples of total mixed ration (TMR) were collected periodically in 15 beef cattle farms and submitted to a nutritional and particle size evaluation. Samples of faeces were taken and analysed for pH, consistency, colour and visually ranked for corn residues (Corn Residue Index) from 4 (totally digested) to 0 (very high presence of maize residues). Dry matter (DM), crude protein (CP), and ash content of TMR for Limousine were higher than that for Charolaise while an opposite situation was observed for crude fiber (CF). Particle size analysis of TMR showed an higher content of small ( 19.0 mm) particles in Charolaise than in Limousine TMR. From May to September a general increase of larger fractions and a reduction of the smaller ones were observed, as a consequence of empirical practices of TMR formulation during summer. Faeces characteristics did not show any difference between breeds (overall mean pH: 6.00 vs 6.13; Corn Residue Index: 2.90 vs 3.24, respectively for Charolaise a..

Perfect state transfers by selective quantum interferences within complex spin networks

We present a method that implement directional, perfect state transfers within a branched spin network by exploiting quantum interferences in the time-domain. That provides a tool to isolate subsystems from a large and complex one. Directionality is achieved by interrupting the spin-spin coupled evolution with periods of free Zeeman evolutions, whose timing is tuned to be commensurate with the relative phases accrued by specific spin pairs. This leads to a resonant transfer between the chosen qubits, and to a detuning of all remaining pathways in the network, using only global manipulations. As the transfer is perfect when the selected pathway is mediated by 2 or 3 spins, distant state transfers over complex networks can be achieved by successive recouplings among specific pairs/triads of spins. These effects are illustrated with a quantum simulator involving 13C NMR on Leucine's backbone; a six-spin network.Comment: 5 pages, 3 figure

Comparing Catalysts of the Direct Synthesis of Hydrogen Peroxide in Organic Solvent: is the Measure of the Product an Issue?

The direct synthesis of hydrogen peroxide has been for about 20 years a hot topic in \u201cgreen\u201d catalysis. Several methods, which are well established to measure the concentration of hydrogen peroxide in water are also applied to the analysis of reaction mixtures from the direct synthesis of H2O2. However, this step could not be always straightforward, because these mixtures contain almost invariably organic solvents and, sometimes, selectivity enhancers which can interfere in some, at the least, of the most popular titrimetric methods. This work presents a comparative investigation of iodometry, cerimetry, permanganometry (titrimetric methods) and spectrophotometric analysis of TiIV/H2O2 adduct, as applied to analysis of hydrogen peroxide produced by its direct synthesis. They account for more than 90 % of the competent literature since 2000. Their pros and cons are highlighted to provide a guideline for the choice of the best possible method of analysis and for the comparison of catalytic results assessed in different ways in the context of the direct synthesis of hydrogen peroxide