Corrugated diaphragm shape design study for hemocompatible pulsatile ventricular assist devices.

We aim to maximize the pumping volume of a pulsatile ventricular assist device, where the diaphragm is covered with an endothelial cell layer. These cells are estimated to survive a cyclic strain up to fifteen percent. To increase the pumping volume under this strain constraint we use an approach based on corrugation of the diaphragm in its reference configuration. The paper explains the parametrization scheme for finding corrugation shapes, addresses modeling and evaluation schemes and reports on the results of a parameter study. The results show that corrugated diaphragm shapes are effective for increasing pumping volumes under a strain constraint.

Action potential initiation and propagation: upstream influences on neurotransmission.

Axonal action potentials initiate the cycle of synaptic communication that is key to our understanding of nervous system functioning. The field has accumulated vast knowledge of the signature action potential waveform, firing patterns, and underlying channel properties of many cell types, but in most cases this information comes from somatic intracellular/whole-cell recordings, which necessarily measure a mixture of the currents compartmentalized in the soma, dendrites, and axon. Because the axon in many neuron types appears to be the site of lowest threshold for action potential initiation, the channel constellation in the axon is of particular interest. However, the axon is more experimentally inaccessible than the soma or dendrites. Recent studies have developed and applied single-fiber extracellular recording, direct intracellular recording, and optical recording techniques from axons toward understanding the behavior of the axonal action potential. We are starting to understand better how specific channels and other cellular properties shape action potential threshold, waveform, and timing: key elements contributing to downstream transmitter release. From this increased scrutiny emerges a theme of axons with more computational power than in traditional conceptualizations.

Time scales of adaptive behavior and motor learning in the presence of stochastic perturbations.

In this paper, the major assumptions of influential approaches to the structure of variability in practice conditions are discussed from the perspective of a generalized evolving attractor landscape model of motor learning. The efficacy of the practice condition effects is considered in relation to the theoretical influence of stochastic perturbations in models of gradient descent learning of multiple dimension landscapes. A model for motor learning is presented combining simulated annealing and stochastic resonance phenomena against the background of different time scales for adaptation and learning processes. The practical consequences of the model's assumptions for the structure of practice conditions are discussed, together with their implications for teaching and coaching.

Learning the pedalo locomotion task.

The authors examined the learning function of a multiple biomechanical degrees of freedom coordination task. Four adult participants practiced the pedalo locomotion task for 350 trials over 7 days. On the basis of the Cauchy theorem, the authors applied a movement pattern difference score that provides a measure of convergence to a fixed point as the criterion for quantifying learning. The findings showed a significant reduction of the movement pattern difference score over practice. Neither an exponential (0.11) nor a power law (0.10) function accommodated a large percentage of the variance of the pattern difference measure on individual learning functions, but the respective fits were higher, although not different, for movement time (.57, .55). Principal components analysis showed a decrease of components over practice; the analysis also showed that 3-5 components were required to accommodate 90% of the variance of the whole-body motion at the end of the final practice session. Those findings on the learning functions for movement and outcome scores are discussed in relation to the redundancy of the biomechanical system in moving to a dynamical stable fixed point in this task.

[Quality assurance and total quality management in residential home care]. / Qualitätssicherung und Qualitätsmanagement in der stationären Altenpflege.

Quality, quality assurance, and quality management have been important topics in residential care homes for several years. However, only as a result of reform processes in the German legislation (long-term care insurance, care quality assurance) is a systematic discussion taking place. Furthermore, initiatives and holistic model projects, which deal with the assessment and improvement of service quality, were developed in the field of care for the elderly. The present article gives a critical overview of essential developments. Different comprehensive approaches such as the implementation of quality management systems, nationwide expert-based initiatives, and developments towards professionalizing care are discussed. Empirically based approaches, especially those emphasizing the assessment of outcome quality, are focused on in this work. Overall, the authors conclude that in the past few years comprehensive efforts have been made to improve the quality of care. However, the current situation still requires much work to establish a nationwide launch and implementation of evidence-based quality assurance and quality management.

[Questioning of relatives--potentials for the internal quality management in institutions caring for the elderly]. / Angehörigenbefragungen - Potenziale für das interne Qualitätsmanagement in Altenpflegeeinrichtungen.

The German care quality assurance law ("Pflege-Qualitätssicherungs-Gesetz", PQsG) calls for internal quality management in residential care facilities. Empirical surveys with residents, their relatives and employees are essential to get transparency and to assess the quality of service. Within the scope of the present study more than 1400 relatives of residents of 31 residential care institutions were surveyed. Therefore in preliminary studies a questionnaire for the relatives was developed, which collects data concerning quality aspects on various aspects (for example care, staff, medical care, cooperation with relatives). On the average, relatives judged the quality of the institutions as good. The overall mean of 2.2 (scale values between 1.8 ["administration/management"] and 2.5 ["care"]) reveals a positive aspect, but there is substantial variation between institutions. Empirical surveys are important tools for internal quality management. Among other things, their results can be used as input for specific quality circle work and thus for continuous improvement. Used continually in the sense of a routine-monitoring system, surveys can also serve to evaluate quality management procedures.

Time scales in motor learning and development.

A theoretical framework based on the concepts and tools of nonlinear dynamical systems is advanced to account for both the persistent and transitory changes traditionally shown for the learning and development of motor skills. The multiple time scales of change in task outcome over time are interpreted as originating from the system's trajectory on an evolving attractor landscape. Different bifurcations between attractor organizations and transient phenomena can lead to exponential, power law, or S-shaped learning curves. This unified dynamical account of the functions and time scales in motor learning and development offers several new hypotheses for future research on the nature of change in learning theory.

MitoTracker labeling in primary neuronal and astrocytic cultures: influence of mitochondrial membrane potential and oxidants.

MitoTracker dyes are fluorescent mitochondrial markers that covalently bind free sulfhydryls. The impact of alterations in mitochondrial membrane potential (Delta Psi(m)) and oxidant stress on MitoTracker staining in mitochondria in cultured neurons and astrocytes has been investigated. p-(Trifluoromethoxy) phenyl-hydrazone (FCCP) significantly decreased MitoTracker loading, except with MitoTracker Green in neurons and MitoTracker Red in astrocytes. Treatment with FCCP after loading increased fluorescence intensity and caused a relocalization of the dyes. The magnitude of these effects was contingent on which MitoTracker, cell type and dye concentration were used. H(2)O(2) pretreatment led to a consistent increase in neuronal MitoTracker Orange and Red and astrocytic MitoTracker Green and Orange fluorescence intensity. H(2)O(2) exposure following loading increased MitoTracker Red fluorescence in astrocytes. In rat brain mitochondria, high concentrations of MitoTracker dyes uncoupled respiration in state 4 and inhibited maximal respiration. Thus, loading and mitochondrial localization of the MitoTracker dyes can be influenced by loss of Delta Psi(m) and increased oxidant burden. These dyes can also directly inhibit respiration. Care must be taken in interpreting data collected using MitoTrackers dyes as these dyes have several potential limitations. Although MitoTrackers may have some value in identifying the location of mitochondria within cultured neurons and astrocytes, their sensitivity to Delta Psi(m) and oxidation negates their use as markers of mitochondrial dynamics in healthy cultures.

Astrocytes are more resistant than neurons to the cytotoxic effects of increased [Zn(2+)](i).

Increased intracellular free Zn(2+) ([Zn(2+)](i)) is toxic to neurons. Glia are more resistant to Zn(2+)-mediated toxicity; however, it is not known if this is because glia are less permeable to Zn(2+) or if glia possess intrinsic mechanisms that serve to buffer or extrude excess [Zn(2+)](i). We used the Zn(2+)-selective ionophore pyrithione to directly increase [Zn(2+)](i) in both neurons and astrocytes. In neurons, a 5-min exposure to 1 microM extracellular Zn(2+) in combination with pyrithione produced widespread toxicity, whereas extensive astrocyte injury was not observed until extracellular Zn(2+) was increased to 10 microM. Measurements with magfura-2 demonstrated that pyrithione increased [Zn(2+)](i) to similar levels in both cell types. We also measured how increased [Zn(2+)](i) affects mitochondrial membrane potential (Deltapsi(m)). In astrocytes, but not in neurons, toxic [Zn(2+)](i) resulted in an acute loss of Deltapsi(m), suggesting that mitochondrial dysregulation may be an early event in [Zn(2+)](i)-induced astrocyte but not neuronal death.

Persistent activation of ERK contributes to glutamate-induced oxidative toxicity in a neuronal cell line and primary cortical neuron cultures.

Oxidative stress can trigger neuronal cell death and has been implicated in several chronic neurological diseases and in acute neurological injury. Oxidative toxicity can be induced by glutamate treatment in cells that lack ionotrophic glutamate receptors, such as the immortalized HT22 hippocampal cell line and immature primary cortical neurons. Previously, we found that neuroprotective effects of geldanamycin, a benzoquinone ansamycin, in HT22 cells were associated with a down-regulation of c-Raf-1, an upstream activator of the extracellular signal-regulated protein kinases (ERKs). ERK activation, although often attributed strictly to neuronal cell survival and proliferation, can also be associated with neuronal cell death that occurs in response to specific insults. In this report we show that delayed and persistent activation of ERKs is associated with glutamate-induced oxidative toxicity in HT22 cells and immature primary cortical neuron cultures. Furthermore, we find that U0126, a specific inhibitor of the ERK-activating kinase, MEK-1/2, protects both HT22 cells and immature primary cortical neuron cultures from glutamate toxicity. Glutamate-induced ERK activation requires the production of specific arachidonic acid metabolites and appears to be downstream of a burst of reactive oxygen species (ROS) accumulation characteristic of oxidative stress in HT22 cells. However, inhibition of ERK activation reduces glutamate-induced intracellular Ca(2+) accumulation. We hypothesize that the precise kinetics and duration of ERK activation may determine whether downstream targets are mobilized to enhance neuronal cell survival or ensure cellular demise.

Non-linear mechanisms in the brain.

Non-linear dynamical models of brain activity can describe the spontaneous emergence of large-scale coherent structures both in a temporal and spatial domain. We discuss a number of discrete time dynamical neuron models that illustrate some of the mechanisms involved. Of special interest is the phenomenon of spatio-temporal stochastic resonance in which coherent structures emerge as a result of the interaction of the neuronal system with external noise at a given level punitive data. We then discuss the general role of stochastic noise in brain dynamics and how similar concepts can be studied in the context of networks of connected brains on the Internet.

Dental public health for the 21st century: implications for specialty education and practice.

A panel of public health practitioners sponsored by the Health Resources and Services Administration met December 6-8, 1994, to examine current roles and responsibilities for dental public health workers and to recommend changes in education and training to meet challenges posed by an evolving health care system. Overall, at least the same number, if not more, dental public health personnel will be needed in the future. While some new roles were identified, the panel felt that only small numbers of personnel will be needed to fill these new roles. Not all of these roles necessarily require a dental degree. The panel felt that a need exists for more academicians for dental schools, schools of public health, dental public health residencies, and dental hygiene programs; oral epidemiologists and health services researchers; health educators; and specialists in utilization review/outcomes assessment, dental informatics, nutrition, program evaluation, and prevention. To meet these personnel needs: (1) dental public health residency programs should be structured to meet the educational needs of working public health dentists with MPH degrees through on-the-job residency programs; (2) the standards for advanced specialty education programs in dental public health should be made sufficiently flexible to include dentists who have advanced education and the requisite core public health courses; (3) flexible MPH degree programs must be available because of the rising debt of dental students and the decreased numbers of graduating dentists; (4) loan repayment should be available for dentists who have pursued public health training and are working in state or local health departments; and (5) standards for advanced education in dental public health should be developed for dental hygienists.

Consumer satisfaction with dental care: where have we been, where are we going?

This paper reviews research developments in the area of dental patient satisfaction over the past three decades, contrasts these with comparable developments in medicine, and suggests directions for future work in the dental arena. The conclusion of the review is that developments in managed care in medicine have stimulated a level of effort in patient satisfaction measures that have gone well beyond that in managed dental care. Analogous work in dentistry is needed as managed dental care plans grow in number.

The Sequential Structure of Movement Outcome in Learning a Discrete Timing Task.

The sequential structure of discrete movement outcomes in an elbow-flexion movement task was examined with a crossed design of 2 movement-time (125 and 500 ms) and 2 range-of-motion (5° and 20°) conditions over sets of 200 trials of practice. Traditional analyses of error score techniques, time-series analyses of the quantitative raw and differenced data, and a symbolic dynamic analysis of qualitative events arising from the data were conducted. The differenced data revealed a consistent order over 3-trial strings that was more apparent with larger steps in the data scores, but quantitative time-series and symbolic dynamic analyses of the raw movement-time data showed weaker relations. There were a few patterns of structure evident in the raw data time-series that were a function of the movement condition and the skill level of the subject. The analyses of the movement-time scores revealed that, in learning the discrete timing task, there is more order apparent in the intrinsic frame of reference of the difference scores than in the extrinsic frame of reference.

A survey of ethical dilemmas and practical problems encountered by practicing dentists.

Dental practice has been subject to many changes in recent years, including third-party involvement, infection control requirements and a rise in litigation. The authors conducted a broad-based national survey of practitioners to learn their views on the ethical and practical problems facing today's dentist.