Dynamic instability in resonant tunneling

We show that an instability may be present in resonant tunneling through a quantum well in one, two and three dimensions, when the resonance lies near the emitter Fermi level. A simple semiclassical model which simulates the resonance and the projected density of states by a nonlinear conductor, the Coulomb barrier by a capacitance, and the time evolution by an iterated map, is used. The model reproduces the observed hysteresis in such devices, and exhibits a series of bifurcations leading to fast chaotic current fluctuations.Comment: 7 pages, 2 figure

Dynamic instabilities in resonant tunneling induced by a magnetic field

We show that the addition of a magnetic field parallel to the current induces self sustained intrinsic current oscillations in an asymmetric double barrier structure. The oscillations are attributed to the nonlinear dynamic coupling of the current to the charge trapped in the well, and the effect of the external field over the local density of states across the system. Our results show that the system bifurcates as the field is increased, and may transit to chaos at large enough fields.Comment: 4 pages, 3 figures, accepted in Phys. Rev. Letter

Dynamical description of the buildup process in resonant tunneling: Evidence of exponential and non-exponential contributions

The buildup process of the probability density inside the quantum well of a double-barrier resonant structure is studied by considering the analytic solution of the time dependent Schr\"{o}dinger equation with the initial condition of a cutoff plane wave. For one level systems at resonance condition we show that the buildup of the probability density obeys a simple charging up law, $| \Psi (\tau) / \phi | =1-e^{-\tau /\tau_0},$ where $\phi$ is the stationary wave function and the transient time constant $\tau_0$ is exactly two lifetimes. We illustrate that the above formula holds both for symmetrical and asymmetrical potential profiles with typical parameters, and even for incidence at different resonance energies. Theoretical evidence of a crossover to non-exponential buildup is also discussed.Comment: 4 pages, 2 figure

Outcomes and outcome measures used in evaluation of communication training in oncology - a systematic literature review, an expert workshop, and recommendations for future research

BACKGROUND: Communication between health care provider and patients in oncology presents challenges. Communication skills training have been frequently developed to address those. Given the complexity of communication training, the choice of outcomes and outcome measures to assess its effectiveness is important. The aim of this paper is to 1) perform a systematic review on outcomes and outcome measures used in evaluations of communication training, 2) discuss specific challenges and 3) provide recommendations for the selection of outcomes in future studies. METHODS: To identify studies and reviews reporting on the evaluation of communication training for health care professionals in oncology, we searched seven databases (Ovid MEDLINE, CENTRAL, CINAHL, EMBASE, PsychINFO, PsychARTICLES and Web of Science). We extracted outcomes assessed and the respective assessment methods. We held a two-day workshop with experts (n = 16) in communication theory, development and evaluation of generic or cancer-specific communication training and/or outcome measure development to identify and address challenges in the evaluation of communication training in oncology. After the workshop, participants contributed to the development of recommendations addressing those challenges. RESULTS: Out of 2181 references, we included 96 publications (33 RCTs, 2 RCT protocols, 4 controlled trials, 36 uncontrolled studies, 21 reviews) in the review. Most frequently used outcomes were participants\u27 training evaluation, their communication confidence, observed communication skills and patients\u27 overall satisfaction and anxiety. Outcomes were assessed using questionnaires for participants (57.3%), patients (36.0%) and observations of real (34.7%) and simulated (30.7%) patient encounters. Outcomes and outcome measures varied widely across studies. Experts agreed that outcomes need to be precisely defined and linked with explicit learning objectives of the training. Furthermore, outcomes should be assessed as broadly as possible on different levels (health care professional, patient and interaction level). CONCLUSIONS: Measuring the effects of training programmes aimed at improving health care professionals\u27 communication skills presents considerable challenges. Outcomes as well as outcome measures differ widely across studies. We recommended to link outcome assessment to specific learning objectives and to assess outcomes as broadly as possible

European guidelines for training in consultation-liaison psychiatry and psychosomatics: report of the EACLPP Workgroup on Training in Consultation-Liaison Psychiatry and Psychosomatics

OBJECTIVE: The European Association of Consultation-Liaison Psychiatry and Psychosomatics (EACLPP) has organized a workgroup to establish consensus on the contents and organization of training in consultation-liaison (C-L) for psychiatric and psychosomatic residents. METHODS: Initially, a survey among experts has been conducted to assess the status quo of training in C-L in different European countries. In several consensus meetings, the workgroup discussed aims, core contents, and organizational issues of standards of training in C-L. Twenty C-L specialists in 14 European countries participated in a Delphi procedure answering a detailed consensus checklist, which included different topics under discussion. RESULTS: Consensus on the following issues has been obtained: (1) all residents in psychiatry or psychosomatics should be exposed to C-L work as part of their clinical experience; (2) a minimum of 6 months of full-time (or equivalent part-time) rotation to a C-L department should take place on the second part of residency; (3) advanced training should last for at least 12 months; (4) supervision of trainees should be clearly defined and organized; and (5) trainees should acquire knowledge and skills on the following: (a) assessment and management of psychiatric and psychosomatic disorders or situations (e.g., suicide/self-harm, somatization, chronic pain and psychiatric disorders, and abnormal illness behavior in somatically ill patients); (b) crisis intervention and psychotherapy methods appropriate for medically ill patients; (c) psychopharmacology in physically ill patients; (d) communication with severely ill patients and dying patients, as well as with medical staff; (e) promotion of coordination of care for complex patients across several disciplines; and (f) organization of C-L service in relation to general hospital and/or primary care. In addition, the workgroup elaborated recommendations on the form of training and on assessment of competency. CONCLUSION: This document is a first step towards establishing recognized training in C-L psychiatry and psychosomatics across the European Union

Mutations in protocadherin 15 and cadherin 23 affect tip links and mechanotransduction in mammalian sensory hair cells

Immunocytochemical studies have shown that protocadherin-15 (PCDH15) and cadherin-23 (CDH23) are associated with tip links, structures thought to gate the mechanotransducer channels of hair cells in the sensory epithelia of the inner ear. The present report describes functional and structural analyses of hair cells from Pcdh15av3J (av3J), Pcdh15av6J (av6J) and Cdh23v2J (v2J) mice. The av3J and v2J mice carry point mutations that are predicted to introduce premature stop codons in the transcripts for Pcdh15 and Cdh23, respectively, and av6J mice have an in-frame deletion predicted to remove most of the 9th cadherin ectodomain from PCDH15. Severe disruption of hair-bundle morphology is observed throughout the early-postnatal cochlea in av3J/av3J and v2J/v2J mice. In contrast, only mild-to-moderate bundle disruption is evident in the av6J/av6J mice. Hair cells from av3J/av3J mice are unaffected by aminoglycosides and fail to load with [3H]-gentamicin or FM1-43, compounds that permeate the hair cell's mechanotransducer channels. In contrast, hair cells from av6J/av6J mice load with both FM1-43 and [3H]-gentamicin, and are aminoglycoside sensitive. Transducer currents can be recorded from hair cells of all three mutants but are reduced in amplitude in all mutants and have abnormal directional sensitivity in the av3J/av3J and v2J/v2J mutants. Scanning electron microscopy of early postnatal cochlear hair cells reveals tip-link like links in av6J/av6J mice, substantially reduced numbers of links in the av3J/av3J mice and virtually none in the v2J/v2J mice. Analysis of mature vestibular hair bundles reveals an absence of tip links in the av3J/av3J and v2J/v2J mice and a reduction in av6J/av6J mice. These results therefore provide genetic evidence consistent with PCDH15 and CDH23 being part of the tip-link complex and necessary for normal mechanotransduction

AC-conductance of a quantum wire with electron-electron interaction

The complex ac-response of a quasi-one dimensional electron system in the one-band approximation with an interaction potential of finite range is investigated. It is shown that linear response is exact for this model. The influence of the screening of the electric field is discussed. The complex absorptive conductance is analyzed in terms of resistive, capacitive and inductive behaviors.Comment: 13 pages, REVTeX, 7 eps figures, to appear in Phys. Rev.

Variational Methods for Biomolecular Modeling

Structure, function and dynamics of many biomolecular systems can be characterized by the energetic variational principle and the corresponding systems of partial differential equations (PDEs). This principle allows us to focus on the identification of essential energetic components, the optimal parametrization of energies, and the efficient computational implementation of energy variation or minimization. Given the fact that complex biomolecular systems are structurally non-uniform and their interactions occur through contact interfaces, their free energies are associated with various interfaces as well, such as solute-solvent interface, molecular binding interface, lipid domain interface, and membrane surfaces. This fact motivates the inclusion of interface geometry, particular its curvatures, to the parametrization of free energies. Applications of such interface geometry based energetic variational principles are illustrated through three concrete topics: the multiscale modeling of biomolecular electrostatics and solvation that includes the curvature energy of the molecular surface, the formation of microdomains on lipid membrane due to the geometric and molecular mechanics at the lipid interface, and the mean curvature driven protein localization on membrane surfaces. By further implicitly representing the interface using a phase field function over the entire domain, one can simulate the dynamics of the interface and the corresponding energy variation by evolving the phase field function, achieving significant reduction of the number of degrees of freedom and computational complexity. Strategies for improving the efficiency of computational implementations and for extending applications to coarse-graining or multiscale molecular simulations are outlined.Comment: 36 page

The Yeast Cell Fusion Protein Prm1p Requires Covalent Dimerization to Promote Membrane Fusion

Prm1p is a multipass membrane protein that promotes plasma membrane fusion during yeast mating. The mechanism by which Prm1p and other putative regulators of developmentally controlled cell-cell fusion events facilitate membrane fusion has remained largely elusive. Here, we report that Prm1p forms covalently linked homodimers. Covalent Prm1p dimer formation occurs via intermolecular disulfide bonds of two cysteines, Cys-120 and Cys-545. PRM1 mutants in which these cysteines have been substituted are fusion defective. These PRM1 mutants are normally expressed, retain homotypic interaction and can traffic to the fusion zone. Because prm1-C120S and prm1-C545S mutants can form covalent dimers when coexpressed with wild-type PRM1, an intermolecular C120-C545 disulfide linkage is inferred. Cys-120 is adjacent to a highly conserved hydrophobic domain. Mutation of a charged residue within this hydrophobic domain abrogates formation of covalent dimers, trafficking to the fusion zone, and fusion-promoting activity. The importance of intermolecular disulfide bonding informs models regarding the mechanism of Prm1-mediated cell-cell fusion