Quantum chaos with spin-chains in pulsed magnetic fields

Recently it was found that the dynamics in a Heisenberg spin-chain subjected to a sequence of periodic pulses from an external, parabolic, magnetic field can have a close correspondence with the quantum kicked rotor (QKR). The QKR is a key paradigm of quantum chaos; it has as its classical limit the well-known Standard Map. It was found that a single spin excitation could be converted into a pair of non-dispersive, counter-propagating spin coherent states equivalent to the accelerator modes of the Standard Map. Here we consider how other types of quantum chaotic systems such as a double-kicked quantum rotor or a quantum rotor with a double-well potential might be realized with spin chains; we discuss the possibilities regarding manipulation of the one-magnon spin waves.Comment: 10 pages, 4 figures. Submitted to PTP special issue for QMC200

Optimal choice of Voluntary traceability as a food risk management tool

Traceability systems are information tools implemented within and between firms in food chains to improve logistics and transparency or to reduce total food safety damage costs. Information about location and condition of products is critical when food safety incidents arise. This paper uses a principal-agent model to investigate the optimal choice of voluntary traceability in terms of precision of information on a given attribute at each link of a food chain. The results suggest that four scenarios may emerge for the supply chain depending on the costs of a system and whether or not the industry can internalize total food safety damages: no traceability, traceability for one link, equal traceability for all links, or different positive traceability levels across all links.Traceability, food safety, principal-agent model, Food Consumption/Nutrition/Food Safety,

The Economics of Traceability for Multi-Ingredient Products: A Network Approach

The consumption of multi-ingredient foods is increasing across the globe as consumers spend less time preparing meals. Traceability is now extensively used to reduce information imperfections in food markets and recent EU law suggests it will be implemented for manufactured meals as well. We present a model developed to understand how information on different ingredients flows through supply chains for multi-ingredient food products. The network model has three tiers linked by contracts for levels of quality and information. The model is useful for analyzing tradeoffs and network effects emerging in the choice of traceability levels.Traceability, multi-ingredient foods, network models, Food Consumption/Nutrition/Food Safety,

Traceability Adoption at the Farm Level: An Empirical Analysis of the Portuguese Pear Industry

Traceability is becoming a condition for doing business in European food markets. Retailers are adopting standards that are more stringent than what is mandatory. An example is EurepGAP, a quality standard for good agricultural practices that includes traceability as a main requirement. We analyze EurepGAP implementation in the Portuguese pear industry and find that implementation cannot be distinguished from sales to British supermarkets. Discrete choice models show the odds of traceability adoption increase with farm size and previous compliance with quality assurance schemes, while farm productivity has a negative impact on the probability of adoption.Research and Development/Tech Change/Emerging Technologies,

Construction of a non-standard quantum field theory through a generalized Heisenberg algebra

We construct a Heisenberg-like algebra for the one dimensional quantum free Klein-Gordon equation defined on the interval of the real line of length $L$. Using the realization of the ladder operators of this type Heisenberg algebra in terms of physical operators we build a 3+1 dimensional free quantum field theory based on this algebra. We introduce fields written in terms of the ladder operators of this type Heisenberg algebra and a free quantum Hamiltonian in terms of these fields. The mass spectrum of the physical excitations of this quantum field theory are given by $\sqrt{n^2 \pi^2/L^2+m_q^2}$, where $n= 1,2,...$ denotes the level of the particle with mass $m_q$ in an infinite square-well potential of width $L$.Comment: Latex, 16 page

Classical diffusion in double-delta-kicked particles

We investigate the classical chaotic diffusion of atoms subjected to {\em pairs} of closely spaced pulses (`kicks) from standing waves of light (the $2\delta$-KP). Recent experimental studies with cold atoms implied an underlying classical diffusion of type very different from the well-known paradigm of Hamiltonian chaos, the Standard Map. The kicks in each pair are separated by a small time interval $\epsilon \ll 1$, which together with the kick strength $K$, characterizes the transport. Phase space for the $2\delta$-KP is partitioned into momentum `cells' partially separated by momentum-trapping regions where diffusion is slow. We present here an analytical derivation of the classical diffusion for a $2\delta$-KP including all important correlations which were used to analyze the experimental data. We find a new asymptotic ($t \to \infty$) regime of `hindered' diffusion: while for the Standard Map the diffusion rate, for $K \gg 1$, $D \sim K^2/2[1- J_2(K)..]$ oscillates about the uncorrelated, rate $D_0 =K^2/2$, we find analytically, that the $2\delta$-KP can equal, but never diffuses faster than, a random walk rate. We argue this is due to the destruction of the important classical `accelerator modes' of the Standard Map. We analyze the experimental regime $0.1\lesssim K\epsilon \lesssim 1$, where quantum localisation lengths $L \sim \hbar^{-0.75}$ are affected by fractal cell boundaries. We find an approximate asymptotic diffusion rate $D\propto K^3\epsilon$, in correspondence to a $D\propto K^3$ regime in the Standard Map associated with 'golden-ratio' cantori.Comment: 14 pages, 10 figures, error in equation in appendix correcte

Representation of Nelson Algebras by Rough Sets Determined by Quasiorders

In this paper, we show that every quasiorder $R$ induces a Nelson algebra $\mathbb{RS}$ such that the underlying rough set lattice $RS$ is algebraic. We note that $\mathbb{RS}$ is a three-valued {\L}ukasiewicz algebra if and only if $R$ is an equivalence. Our main result says that if $\mathbb{A}$ is a Nelson algebra defined on an algebraic lattice, then there exists a set $U$ and a quasiorder $R$ on $U$ such that $\mathbb{A} \cong \mathbb{RS}$.Comment: 16 page

Estado Confusional Agudo após Corticoterapia Inalada

Background: The connection between corticotherapy and neuropsychiatric symptoms is widely known, being one of the first questions we need to assess when presenting with first episode psychiatric symptoms or confusional state. Aims: To date, data on cases related to inhaled corticotherapy and neuropsychiatric effects is scarce. In this paper we describe a rare case in a young woman. Methods: The clinical case presented led us to try to understand the data published on the subject in order to discuss it in greater length. Results and Conclusions: We present and discuss a 27-year-old patient’s case, with no previous psychiatric disease, who was admitted to our Psychiatric ward after the onset of severe acute behavioural disturbance characterized by aggressiveness, visual and auditory hallucinatory activity, misidentification and altered conscience status. It was later found that seven days earlier she had been prescribed inhaled corticotherapy for a minor respiratory infection. A few days after corticotherapy withdrawal, the clinical symptoms improved significantly.info:eu-repo/semantics/publishedVersio