Compact MCTDH wave functions for high-dimensional system-bath quantum dynamics.

We employ a simple multiconfiguration time-dependent Hartree (MCTDH) ansatz tailored to an effective-mode transformation of environmental variables that brings the bath into a linear chain form. In this form, important (primary) degrees of freedom can be easily identified and treated at a high correlation level, whereas secondary modes are left uncorrelated. The resulting approach scales linearly with the bath dimensions and allows us to easily access recurrence times much longer than usually possible, at a very small computational cost. Test calculations for model atom-surface problems show that the system dynamics is correctly reproduced in the relevant time window, and quantitative agreement is attained for energy relaxation and sticking, particularly in non-Markovian environments. These results pave the way for tackling realistic system-bath quantum dynamical problems on the picosecond scale.

Unraveling a Brownian particle's memory with effective mode chains.

Memory effects in quantum dynamical processes involving structured environments are presently difficult, if not impossible, to investigate using standard approaches. Progress can be made by transforming the environmental variables to a suitable chain representation which effectively performs a Markovian embedding of the dynamics. Here, we show that this effective-mode chain representation provides a unique way of unraveling the memory kernel κ(t) as a function of time. Truncated or Markov-closed chains with n effective modes exactly reproduce κ(t) to the 4nth order in time, up to an irrelevant constant of order κ(0)/n. These favorable convergence properties pave the way for efficient quantum simulations of fast (non-Markovian) processes by reduced dynamical models.

Communication: Universal Markovian reduction of Brownian particle dynamics.

Non-Markovian processes can often be turned Markovian by enlarging the set of variables. Here we show, by an explicit construction, how this can be done for the dynamics of a Brownian particle obeying the generalized Langevin equation. Given an arbitrary bath spectral density J(0), we introduce an orthogonal transformation of the bath variables into effective modes, leading stepwise to a semi-infinite chain with nearest-neighbor interactions. The transformation is uniquely determined by J(0) and defines a sequence {J(n)}(n∈N) of residual spectral densities describing the interaction of the terminal chain mode, at each step, with the remaining bath. We derive a simple one-term recurrence relation for this sequence and show that its limit is the quasi-Ohmic expression provided by the Rubin model of dissipation. Numerical calculations show that, irrespective of the details of J(0), convergence is fast enough to be useful in practice for an effective Ohmic reduction of the dissipative dynamics.

Painful rib syndrome. A variant of myofascial pain syndrome.

1. Painful rib syndrome has many similarities to a new classification of pain conditions called myofascial pain syndrome. Both conditions respond well to noninvasive, supportive nursing interventions. 2. Painful rib syndrome is characterized by pain in the upper abdomen or lower chest, a tender spot on the costal margin, and reproduction of pain when pressing on the tender spot or trigger point. 3. The most critical intervention is to explain the benign nature of the condition, and provide support that the pain is real and can be managed. Prognosis is not gender or age specific, but is related to treatment response. 4. Employees and their families living and working with pain syndromes need the nurses' ongoing support and advocacy. Pain syndromes are difficult to diagnose and treatment may not eliminate the pain.

Essential components of the short-term psychiatric unit.

TOPIC: How nurses can meet the priority needs of the acute care clients during inpatient psychiatric hospitalizations that average five days. PURPOSE: To assist acute care nursing staff in reorganizing their caregiving to maximize therapeutic gains of clients in a minimum period of time SOURCE: Personal experience. CONCLUSION: Success in the short-term unit depends not only on the ability of nurses to stabilize clients in crisis, but also on their ability to provide linkage with aftercare services so the therapeutic process can be continued.

Economic uncertainty: helping employees cope.

1. The loss or threat of losing a job may have profound physiological, psychological, and behavioral effects on employees. 2. Middle aged men deteriorate more in the first year after losing a job than younger or older men. 3. It is important that unemployed people make a commitment to purposeful activity and see work in a broader definition. 4. Parents may need reminding to praise their children more than usual and continue positive family activities and routines during times of unemployment.

Psychiatric emergencies in the workplace.

1. The functioning of depressed individuals is comparable with or worse than individuals with major chronic medical conditions. 2. A well thought-out and detailed plan in combination with a highly lethal method is indicative of an individual who is at risk for carrying out the act of suicide. 3. Many psychotic episodes begin with subtle changes in thinking. 4. Many manic employees' symptoms may be well controlled and they can be productive workers if they are managed on the medication lithium.