RESUMEN
When a qubit or spin interacts with others under a many-body Hamiltonian, the information it contains progressively scrambles. Here, nuclear spins of an adamantane crystal are used as a quantum simulator to monitor such dynamics through out-of-time-order correlators, while a Loschmidt echo (LE) asses how weak perturbations degrade the information encoded in these increasingly complex states. Both observables involve the implementation of a time-reversal procedure which, in practice, involves inverting the sign of the effective Hamiltonian. Our protocols use periodic radio frequency pulses to modulate the natural dipolar interaction implementing a Hamiltonian that can be scaled down at will. Meanwhile, experimental errors and strength of perturbative terms remain constant and can be quantified through the LE. For each scaling factor, information spreading occurs with a timescale, T_{2}, inversely proportional to the local second moment of the Hamiltonian. We find that, when the reversible interactions dominate over the perturbations, the information scrambled among up to 10^{2} spins can still be recovered. However, we find that the LE decay rate cannot become smaller than a critical value 1/T_{3}≈(0.15±0.02)/T_{2}, which only depends on the interactions themselves, and not on the perturbations. This result shows the emergence of a regime of intrinsic irreversibility in accordance to a central hypothesis of irreversibility, hinted from previous experiments.
RESUMEN
In this work, we overview time-reversal nuclear magnetic resonance (NMR) experiments in many-spin systems evolving under the dipolar Hamiltonian. The Loschmidt echo (LE) in NMR is the signal of excitations which, after evolving with a forward Hamiltonian, is recovered by means of a backward evolution. The presence of non-diagonal terms in the non-equilibrium density matrix of the many-body state is directly monitored experimentally by encoding the multiple quantum coherences. This enables a spin counting procedure, giving information on the spreading of an excitation through the Hilbert space and the formation of clusters of correlated spins. Two samples representing different spin systems with coupled networks were used in the experiments. Protons in polycrystalline ferrocene correspond to an 'infinite' network. By contrast, the liquid crystal N-(4-methoxybenzylidene)-4-butylaniline in the nematic mesophase represents a finite proton system with a hierarchical set of couplings. A close connection was established between the LE decay and the spin counting measurements, confirming the hypothesis that the complexity of the system is driven by the coherent dynamics.
RESUMEN
UNLABELLED: The health organisations have moved from being centred on the professionals and are now centred on users and their expectations. The new health institutions want to know patients' perception of the quality of the care received, with particular respect to the information received, consent and decision making. It is necessary to have available measuring instruments that explore the different components of the process of information, consent and decision making. BACKGROUND: To identify the dimensions related to the process of information, consent and decision making of most importance to patients and susceptible to evaluation by questionnaire. SUBJECTS AND METHODS: Adult persons who have been hospitalised for at least two days. Qualitative study using semi-structured interviews. RESULTS: The participants wish to be informed and to participate in decision making; they do not know the meaning of the charter of patients' rights; they wish to share the whole care process with their family; written information is incomprehensible to them; and they feel that their pain and discomfort do not receive appropriate attention. CONCLUSION: It would be convenient to include the following dimensions in the questionnaires on satisfaction: a) the possibility of clarifying doubts; b) real knowledge of the rights and duties of patients; c) participation by the family in the care process; d) continuity of the same informer throughout hospitalisation; d) degree of understanding of the written information; e) involvement in decision making; and f) attention to pain and discomfort.
Asunto(s)
Hospitalización , Satisfacción del Paciente , Adolescente , Adulto , Anciano , Femenino , Humanos , Masculino , Sistemas de Registros Médicos Computarizados , Persona de Mediana Edad , Participación del Paciente , Encuestas y CuestionariosRESUMEN
The nursing profession has always placed great importance on the ethical requirements linked to its activities. However, the understanding and content to these activities has evolved over the course of history. Two approaches have been developed as the principal issues of nursing ethics: the ethics of virtue and the ethics of principles. The first approach enquires into the attitudes that must be held by a person in order to act as a good nurse. The second follows an inverse course and considers the actions and principles that must be respected in order to be a good professional. An approach that harmonises both perspectives must pose the following questions: What do we understand by nursing care? On what ethical principles is this form of understanding care based? What moral attitudes are related to caring correctly? In a modern professional model, the definition and exercise of care necessarily include consideration of team work. Similarly, carrying out a good caring function, that is to say quality nursing, requires apprenticeship on the one hand, and, on the other, the assimilation of the attitudes that are required in a person involved in caring. Both elements improve the capacity of the professionals to prevent and resolve ethical conflicts in the practice of care.