Open system control of dynamical transitions under the generalized Kruskal-Neishtadt-Henrard theorem.

Useful dynamical processes often begin through barrier-crossing dynamical transitions; engineering system dynamics in order to make such transitions reliable is therefore an important task for biological or artificial microscopic machinery. Here, we first show by example that adding even a small amount of back-reaction to a control parameter, so that it responds to the system's evolution, can significantly increase the fraction of trajectories that cross a separatrix. We then explain how a post-adiabatic theorem due to Neishtadt can quantitatively describe this kind of enhancement without having to solve the equations of motion, allowing systematic understanding and design of a class of self-controlling dynamical systems.

Hamiltonian active particles in an environment.

We examine a Hamiltonian system which represents an active particle that can move against an opposing external force by drawing energy from an internal depot while immersed in a noisy and dissipative environment. The Hamiltonian consists of two subsystems, one representing the active particle's motion and the other its depot of "fuel." We show that although the active particle loses some of its energy to dissipation from the environment, dissipation can also help to stabilize the dynamical process that makes the particle active. This raises the possibility that the internal mechanisms of active particles may not only be able to operate in noisy and dissipative environments, but may actually rely on the environment for their control.

Prethermalization with negative specific heat.

We study noncanonical relaxation in an aggregate of subsystems with negative specific heat. The Thirring instability drives the constituent subsystems towards the edges of their energy spectrum, so that the existence of a single adiabatic invariant results in structured noncanonical steady states that are spectacularly different from the grand-canonical prediction. For parameter regimes where this adiabatic invariance breaks down, the system exhibits prethermalization far away from integrability, with an unprecedented contrast between the prethermal- and thermal states.

Probabilistic Hysteresis in Integrable and Chaotic Isolated Hamiltonian Systems.

We propose currently feasible experiments using small, isolated systems of ultracold atoms to investigate the effects of dynamical chaos in the microscopic onset of irreversibility. A control parameter is tuned past a critical value, then back to its initial value; hysteresis appears as a finite probability that the atoms fail to return to their initial state even when the parameter sweep is arbitrarily slow. We show that an episode of chaotic dynamics during part of the sweep time produces distinctive features in the distribution of final states that will be clearly observable in experiments.

Social and community program approaches to participants: Exploring best practices.

This article presents the results of a deepened study of the best practices and outcomes of 15 programs (across 9 countries) that work with socioeconomically disadvantagedd communities. Using thematic analysis, we identified best practices that participants, community leaders, and professionals recognized as key. Data collection involved in loco observation and semistructured interviews with participants and professionals, and focus groups with professionals. Associated with best practices, programs adopted two central perspectives on approaching participants: approaching participants as users and approaching participants as contributors. Such approaches were crossed with best practices and outcomes identified througout the analysis. For programs that approached participants as users, the best practices were valuing, facilitating the access to resources, showing availability, and promoting competencies and openness, and the main outcome was participants' improved self-confidence. For programs that approached participants as contributors, the best practices were contributing, encouraging participation, valuing participants, becoming masters, and reciprocity, and the main outcome was participants having an impact.

Trajectories on the path to reciprocity-A theoretical framework for collaborating with socioeconomically disadvantaged communities.

The importance of cultivating connection to enhance individual, relational and collective well-being is gaining attention in the current literature on building community. Although these goals are being increasingly considered, the concept of reciprocity has been less prominent than may be warranted in the field of psychology. This article presents a theoretical framework on the dynamics of reciprocity which resulted from grounded theory (GT) research involving 2 complementary studies. The first study involved 22 participants from different socioeconomic backgrounds engaged in "reflecting-team with appreciative audiences" sessions (Madsen, 2007) in Portugal. The second study involved participant observation of 15 community programs recognized as good-practices in collaboration with socioeconomically disadvantaged participants, at national and international levels, across 9 countries. The theoretical framework emphasizes the centrality of building reciprocity for the development of individuals, families, communities, and programs. It integrates the trajectories of reciprocity; quadrants reflecting the standpoints assumed according to socioeconomic and cultural positions; basic social-psychological processes inherent to the process of building reciprocity; and characterizes different types of programs. The resulting framework is analyzed in relation to prior literature for a broader understanding of synergies and challenges, and the article concludes by suggesting implications for further research and practice. (PsycINFO Database Record

Acogimiento residencial terapéutico para niños y adolescentes: una declaración de consenso del Grupo de Trabajo Internacional sobre Acogimiento Residencial Terapéutico / Therapeutic Residential Care for Children and Youth: A Consensus Statement of the International Work Group on Therapeutic Residential Care

En muchos países desarrollados a lo largo del mundo las intervenciones en acogimiento residencial para niños y adolescentes se encuentran en un momento de creciente debate. Ante esta situación, se organizó una cumbre internacional en Inglaterra (primavera de 2016) con expertos de 13 países para reflexionar sobre el acogimiento residencial terapéutico (ART). Se partió de la siguiente definición de ART: "el acogimiento residencial terapéutico implica el uso planificado de un ambiente de convivencia multidimensional, construido a propósito, diseñado para desarrollar o proveer tratamiento, educación, socialización, apoyo y protección a niños y jóvenes con necesidades reconocidas de salud mental o conductuales, en cooperación con sus familias y la colaboración de un amplio espectro recursos comunitarios formales e informales». La reunión se caracterizó por el intercambio de información y evidencias y la preparación de una agenda internacional de investigación. Además, se discutieron las bases para una declaración de consenso. Esta declaración, originalmente publicada en inglés y ahora reproducida en español, comprende, entre otras cuestiones, cinco principios básicos de acogimiento que de acuerdo con el grupo de trabajo en acogimiento residencial terapéutico deben guiar el acogimiento residencial de jóvenes que se preste en todo momento (AU)

In many developed countries around the world residential care interventions for children and adolescents have come under increasing scrutiny. Against this background an international summit was organised in England (spring 2016) with experts from 13 countries to reflect on therapeutic residential care (TRC). The following working definition of TRC was leading: «Therapeutic residential care involves the planful use of a purposefully constructed, multi-dimensional living environment designed to enhance or provide treatment, education, socialization, support, and protection to children and youth with identified mental health or behavioral needs in partnership with their families and in collaboration with a full spectrum of community based formal and informal helping resources». The meeting was characterised by exchange of information and evidence, and by preparing an international research agenda. In addition, the outlines of a consensus statement on TRC were discussed. This statement, originally published in English and now reproduced in a Spanish translation, comprises inter alia five basic principles of care that according to the Work Group on Therapeutic Residental Care should be guiding for residential youth care provided at any time (AU)

[Therapeutic Residential Care for Children and Youth: A Consensus Statement of the International Work Group on Therapeutic Residential Care].

Therapeutic Residential Care for Children and Youth: A Consensus Statement of the International Work Group on Therapeutic Residential Care. In many developed countries around the world residential care interventions for children and adolescents have come under increasing scrutiny. Against this background an international summit was organised in England (spring 2016) with experts from 13 countries to reflect on therapeutic residential care (TRC). The following working definition of TRC was leading: “Therapeutic residential care involves the planful use of a purposefully constructed, multi-dimensional living environment designed to enhance or provide treatment, education, socialization, support, and protection to children and youth with identified mental health or behavioral needs in partnership with their families and in collaboration with a full spectrum of community based formal and informal helping resources”. The meeting was characterised by exchange of information and evidence, and by preparing an international research agenda. In addition, the outlines of a consensus statement on TRC were discussed. This statement, originally published in English and now reproduced in a Spanish translation, comprises inter alia five basic principles of care that according to the Work Group on Therapeutic Residental Care should be guiding for residential youth care provided at any time.

Quantum Hamiltonian daemons: Unitary analogs of combustion engines.

Hamiltonian daemons have recently been defined classically as small, closed Hamiltonian systems which can exhibit secular energy transfer from high-frequency to low-frequency degrees of freedom (steady downconversion), analogous to the steady transfer of energy in a combustion engine from the high terahertz frequencies of molecular excitations to the low kilohertz frequencies of piston motion [L. Gilz, E. P. Thesing, and J. R. Anglin, Phys. Rev. E 94, 042127 (2016)2470-004510.1103/PhysRevE.94.042127]. Classical daemons achieve downconversion within a small, closed system by exploiting nonlinear resonances; the adiabatic theorem permits their operation but imposes nontrivial limitations on their efficiency. Here we investigate a simple example of a quantum mechanical daemon. In the correspondence regime it obeys similar efficiency limits to its classical counterparts, but in the strongly quantum mechanical regime the daemon operates in an entirely different manner. It maintains an engine-like behavior in a distinctly quantum mechanical form: a weight is lifted at a steady average speed through a long sequence of quantum jumps in momentum, at each of which a quantum of fuel is consumed. The quantum daemon can cease downconversion at any time through nonadiabatic Landau-Zener transitions, and continuing operation of the quantum daemon is associated with steadily growing entanglement between fast and slow degrees of freedom.

Hamiltonian analogs of combustion engines: A systematic exception to adiabatic decoupling.

Workhorse theories throughout all of physics derive effective Hamiltonians to describe slow time evolution, even though low-frequency modes are actually coupled to high-frequency modes. Such effective Hamiltonians are accurate because of adiabatic decoupling: the high-frequency modes "dress" the low-frequency modes, and renormalize their Hamiltonian, but they do not steadily inject energy into the low-frequency sector. Here, however, we identify a broad class of dynamical systems in which adiabatic decoupling fails to hold, and steady energy transfer across a large gap in natural frequency ("steady downconversion") instead becomes possible, through nonlinear resonances of a certain form. Instead of adiabatic decoupling, the special features of multiple time scale dynamics lead in these cases to efficiency constraints that somewhat resemble thermodynamics.

Minimal Fokker-Planck theory for the thermalization of mesoscopic subsystems.

We explore a minimal paradigm for thermalization, consisting of two weakly coupled, low dimensional, nonintegrable subsystems. As demonstrated for Bose-Hubbard trimers, chaotic ergodicity results in a diffusive response of each subsystem, insensitive to the details of the drive exerted on it by the other. This supports the hypothesis that thermalization can be described by a Fokker-Planck equation. We also observe, however, that Levy-flight type anomalies may arise in mesoscopic systems, due to the wide range of time scales that characterize 'sticky' dynamics.

Quantum kinetic theory of collisionless superfluid internal convection.

Superfluids can transport heat via simultaneous opposite flows of their spatially interpenetrating condensate and noncondensate components. While this internal convection is usually described within Landau's phenomenological two-fluid hydrodynamics, we apply quantum kinetic theory to a dilute Bose gas held between thermal reservoirs at different temperatures and show that the phenomenon also appears in collisionless kinetic regimes and should be directly observable in currently feasible experiments on trapped ultracold vapors.

Collisions in zero temperature Fermi gases.

We examine the collisional behavior of two-component Fermi gases released at zero temperature from a harmonic trap. Using a phase-space formalism to calculate the collision rate during expansion, we find that Pauli blocking plays only a minor role for momentum changing collisions. As a result, for a large scattering cross section, Pauli blocking will not prevent the gas from entering the collisionally hydrodynamic regime. In contrast to the bosonic case, hydrodynamic expansion at very low temperatures is therefore not evidence for fermionic superfluidity.

Bose-Einstein condensation of atomic gases.

The early experiments on Bose-Einstein condensation in dilute atomic gases accomplished three long-standing goals. First, cooling of neutral atoms into their motional ground state, thus subjecting them to ultimate control, limited only by Heisenberg's uncertainty relation. Second, creation of a coherent sample of atoms, in which all occupy the same quantum state, and the realization of atom lasers - devices that output coherent matter waves. And third, creation of a gaseous quantum fluid, with properties that are different from the quantum liquids helium-3 and helium-4. The field of Bose-Einstein condensation of atomic gases has continued to progress rapidly, driven by the combination of new experimental techniques and theoretical advances. The family of quantum-degenerate gases has grown, and now includes metastable and fermionic atoms. Condensates have become an ultralow-temperature laboratory for atom optics, collisional physics and many-body physics, encompassing phonons, superfluidity, quantized vortices, Josephson junctions and quantum phase transitions.