Parameter estimation for a phenomenological model of the cardiac action potential

The action potential (ap) of a cardiac cell is made up of a complex balance of ionic currents which flow across the cell membrane in response to electrical excitation of the cell. Biophysically detailed mathematical models of the ap have grown larger in terms of the variables and parameters required to model new findings in subcellular ionic mechanisms. The fitting of parameters to such models has seen a large degree of parameter and module re-use from earlier models. An alternative method for modelling electrically exciteable cardiac tissue is a phenomenological model, which reconstructs tissue level ap wave behaviour without subcellular details. A new parameter estimation technique to fit the morphology of the ap in a four variable phenomenological model is presented. An approximation of a nonlinear ordinary differential equation model is established that corresponds to the given phenomenological model of the cardiac ap. The parameter estimation problem is converted into a minimisation problem for the unknown parameters. A modified hybrid Nelder–Mead simplex search and particle swarm optimization is then used to solve the minimisation problem for the unknown parameters. The successful fitting of data generated from a well known biophysically detailed model is demonstrated. A successful fit to an experimental ap recording that contains both noise and experimental artefacts is also produced. The parameter estimation method’s ability to fit a complex morphology to a model with substantially more parameters than previously used is established.

Phenomenological modeling of cell-to-cell and beat-to-beat variability in isolated Guinea Pig ventricular myocytes

Experimental action potential (AP) recordings in isolated ventricular myoctes display significant temporal beat-to-beat variability in morphology and duration. Furthermore, significant cell-to-cell differences in AP also exist even for isolated cells originating from the same region of the same heart. However, current mathematical models of ventricular AP fail to replicate the temporal and cell-to-cell variability in AP observed experimentally. In this study, we propose a novel mathematical framework for the development of phenomenological AP models capable of capturing cell-to-cell and temporal variabilty in cardiac APs. A novel stochastic phenomenological model of the AP is developed, based on the deterministic Bueno-Orovio/Fentonmodel. Experimental recordings of AP are fit to the model to produce AP models of individual cells from the apex and the base of the guinea-pig ventricles. Our results show that the phenomenological model is able to capture the considerable differences in AP recorded from isolated cells originating from the location. We demonstrate the closeness of fit to the available experimental data which may be achieved using a phenomenological model, and also demonstrate the ability of the stochastic form of the model to capture the observed beat-to-beat variablity in action potential duration.

Parental experience of childhood cancer using Interpretative Phenomenological Analysis

Whilst survival rates for childhood cancer have improved dramatically over the past three decades, it is still a devastating diagnosis for family members and an illness which severely disrupts the lifestyle of the family unit. Developing an understanding of the impact of the illness on the family is crucial to better support families’ deal with the demands of the illness. In this study 9 families in which a child was diagnosed with cancer were interviewed twice over a 12 month period, approximately 6 months apart. Using Interpretative Phenomenological Analysis (IPA), a semi-structured interview was used to explicate parent’s experience of childhood cancer. The results revealed 5 super ordinate themes; (1) a pivotal moment in time, (2) the experience of adaptation in relation to having a sick child, (3) the nature of support, (4) re-evaluation of values during a critical life experience and (5) the experience of optimism and altruism. Findings indicate that parents express both negative and positive experiences as they re-evaluate the meaning and purpose of life, seek to redefine themselves, often in terms of priorities, relationships, sense of community, and achieve degrees of optimism and altruism. Implications for addressing the needs of parents and for further research are discussed.

A phenomenological model for the structure-composition relationship of the high Tc cuprates based on simple chemical principles

A simple phenomenological model for the relationship between structure and composition of the high Tc cuprates is presented. The model is based on two simple crystal chemistry principles: unit cell doping and charge balance within unit cells. These principles are inspired by key experimental observations of how the materials accommodate large deviations from stoichiometry. Consistent explanations for significant HTSC properties can be explained without any additional assumptions while retaining valuable insight for geometric interpretation. Combining these two chemical principles with a review of Crystal Field Theory (CFT) or Ligand Field Theory (LFT), it becomes clear that the two oxidation states in the conduction planes (typically d8 and d9) belong to the most strongly divergent d-levels as a function of deformation from regular octahedral coordination. This observation offers a link to a range of coupling effects relating vibrations and spin waves through application of Hund’s rules. An indication of this model’s capacity to predict physical properties for HTSC is provided and will be elaborated in subsequent publications. Simple criteria for the relationship between structure and composition in HTSC systems may guide chemical syntheses within new material systems.

Extreme sports are good for your health : a phenomenological understanding of fear and anxiety in extreme sport

Extreme sports are traditionally explored from a risk-taking perspective which often assumes that participants do not experience fear. In this paper we explore participants’ experience of fear associated with participation in extreme sports. An interpretive phenomenological method was used with 15 participants. Four themes emerged: experience of fear, relationship to fear, management of fear, and fear and self transformation. Participant’s experience of extreme sports was revealed in terms of intense fear but this fear was integrated and experienced as a potentially meaningful and constructive event in their lives. The findings have implications for understanding fear as a potentially transformative process.

A phenomenological study of dream interpretation among the Xhosa-speaking people in rural South Africa

Psychologists investigating dreams in non-Western cultures have generally not considered the meanings of dreams within the unique meaning-structure of the person in his or her societal context. The study was concerned with explicating the indigenous system of dream interpretation of the Xhosa-speaking people, as revealed by acknowledged dream experts, and elaborating upon the life-world of the participants. Fifty dreams and their interpretations were collected from participants, who were traditional healers and their clients. A phenomenological methodology was adopted in explicating the data. Themes explicated included : the physiognomy of the dreamer's life-world as revealed by significant dreams, the interpretation of significant dreams as revealed through action, and human bodiliness as revealed in dream interpretations. The participants' approach to dreams is not based upon an explicit theory, but upon an immediate and pathic understanding of the dream phenomenon. The understanding is based upon the interpreter's concrete understanding of the life-world, which includes the possibility of cosmic integration and continuity between personal and trans-personal realms of being

An interpretative phenomenological analysis of participation in a pro-anorexia Internet site and its relationship to disordered eating

Pro-anorexia Internet sites aim to promote, support and discuss anorexia nervosa. Media coverage has raised concerns that sites may increase the level of eating disorders. This research examines the meaning of participation in a pro-anorexia Internet site and its relationship with disordered eating by using an interpretative phenomenological analysis of fifteen separate message ‘threads’ followed over a six-week period. Four themes were identified: (1) tips and techniques; (2) ‘ana’ v. anorexia nervosa; (3) social support; and (4) need for anorexia. Findings suggest participation was multi-purpose, providing a coping function in relation to weight loss, and the contribution of sites to increased levels of eating disorders is not inevitable.

The search for freedom in extreme sports : a phenomenological exploration

Participation in extreme sports is continuing to grow, yet there is still little understanding of participant motivations in such sports. The purpose of this paper is to report on one aspect of motivation in extreme sports, the search for freedom. The study utilized a hermeneutic phenomenological methodology. Fifteen international extreme sport participants who participated in sports such as BASE jumping, big wave surfing, extreme mountaineering, extreme skiing, rope free climbing and waterfall kayaking were interviewed about their experience of participating in an extreme sport. Results reveal six elements of freedom: freedom from constraints, freedom as movement, freedom as letting go of the need for control, freedom as the release of fear, freedom as being at one, and finally freedom as choice and responsibility. The findings reveal that motivations in extreme sport do not simply mirror traditional images of risk taking and adrenaline and that motivations in extreme sports also include an exploration of the ways in which humans seek fundamental human values.

An interpretative phenomenological analysis of stress and well-being in Emergency Medical Dispatchers

This study explored the stress and wellbeing of Emergency Medical Dispatchers (EMD) who remotely provide crisis intervention to medical emergencies through telehealth support. Semi-structured interviews with 16 EMDs were conducted and Interpretative Phenomenological Analysis was used to identify themes in the data. These results indicated that despite their physical distance from the crisis scene, EMDs can experience vicarious trauma through acute and cumulative exposure to traumatic incidents and their perceived lack of control which can expound feelings of helplessness. Three superordinate themes of operational stress and trauma, organisational stress, and posttraumatic growth were identified. Practical implications are suggested to enable emergency services organisations to counteract this job related stress and promote more positive mental health outcomes.

The phenomenological approach : a framework to design markets

An approach is proposed and applied to five industries to prove how phenomenology can be valuable in rethinking consumer markets (Popp & Holt, 2013). The purpose of this essay is to highlight the potential implications that 'phenomenological thinking' brings for competitiveness and innovation (Sanders, 1982), hence helping managers being more innovative in their strategic marketing decisions (i.e. market creation, positioning, branding). Phenomenology is in fact a way of thinking − besides and before being a qualitative research procedure − a very practical exercise that strategic managers can master and apply in the same successful way as other scientists have already done in their fields of study (e.g. sociology, psychology, psychiatry, and anthropology). Two fundamental considerations justify this research: a lack of distinctiveness among firms due to high levels of competition and consumers no longer knowing what they want (i.e. no more needs). The authors will show how the classical mental framework generally used to study markets by practitioners appears on the one hand to be established and systematic in the life of a company, while on the other is no longer adequate to meet the needs of innovation required to survive. To the classic principles of objectivity, generality, and psycho-sociology the authors counterpose the imaginary, eidetic-phenomenological reduction, and an existential perspective. From a theoretical point of view, this paper introduces a set of functioning rules applicable to achieve innovation in any market and useful to identify cultural practices inherent in the act of consumption.

The role of counselling in healing from sexual assault in childhood from the phenomenological perspective of men and women

Serious Childhood Sexual Assault (CSA) has the potential for a wide range of extreme difficulties, not only in childhood but for many years to come. However, the lasting negative impacts are not inevitable and with the right help, those who have experienced CSA can go on to enjoy whole and fulfilling lives. The question posed in this research is “What comprises “the right help”? The present study qualitatively investigated the narratives of men and women with regard to what was deemed important components of counselling which facilitated their healing from childhood sexual assault. Participants consisted of 21 women and 11 men who had sought both individual and group counselling to work through issues stemming from traumatic sexual assault in childhood. Findings presented here describe three superordinate themes which were essential in the healing process, incorporating abuse-specific, client-specific and practitioner-specific components. A final superordinate theme of negative experiences in counselling is also presented, describing unhelpful or negative counselling experiences. Similarities between men and women as to the important components of counselling was remarkable, however important gender differences were also observed.

Pathways to peace : a phenomenological exploration of the processes of healing and posttraumatic growth following childhood sexual assault

This thesis explored pathways to healing in men and women who experienced traumatic sexual abuse in childhood and considered themselves to be in a place of wellness. The thesis synthesises current knowledge in this area and has produced a number of models with direct implications for clinical practice. This unique work has also contributed to advancing theoretical understanding of healing following sexual assault.

Melt electrospinning of poly(epsilon-caprolactone) scaffolds: Phenomenological observations associated with collection and direct writing

Melt electrospinning and its additive manufacturing analogue, melt electrospinning writing (MEW), are two processes which can produce porous materials for applications where solvent toxicity and accumulation in solution electrospinning are problematic. This study explores the melt electrospinning of poly(ε-caprolactone) (PCL) scaffolds, specifically for applications in tissue engineering. The research described here aims to inform researchers interested in melt electrospinning about technical aspects of the process. This includes rapid fiber characterization using glass microscope slides, allowing influential processing parameters on fiber morphology to be assessed, as well as observed fiber collection phenomena on different collector substrates. The distribution and alignment of melt electrospun PCL fibers can be controlled to a certain degree using patterned collectors to create large numbers of scaffolds with shaped macroporous architectures. However, the buildup of residual charge in the collected fibers limits the achievable thickness of the porous template through such scaffolds. One challenge identified for MEW is the ability to control charge buildup so that fibers can be placed accurately in close proximity, and in many centimeter heights. The scale and size of scaffolds produced using MEW, however, indicate that this emerging process will fill a technological niche in biofabrication.

Different phenomenological theories and their abilities to describe the interdiffusion process in a binary system during multiphase growth

There are essentially two different phenomenological models available to describe the interdiffusion process in binary systems in the olid state. The first of these, which is used more frequently, is based on the theory of flux partitioning. The second model, developed much more recently, uses the theory of dissociation and reaction. Although the theory of flux partitioning has been widely used, we found that this theory does not account for the mobility of both species and therefore is not suitable for use in most interdiffusion systems. We have first modified this theory to take into account the mobility of both species and then further extended it to develop relations or the integrated diffusion coefficient and the ratio of diffusivities of the species. The versatility of these two different models is examined in the Co-Si system with respect to different end-member compositions. From our analysis, we found that the applicability of the theory of flux partitioning is rather limited but the theory of dissociation and reaction can be used in any binary system.