Cluster analysis of flow cytometric list mode data on a personal computer

A cluster analysis algorithm, dedicated to analysis of flow cytometric data is described. The algorithm is written in Pascal and implemented on an MS-DOS personal computer. It uses k-means, initialized with a large number of seed points, followed by a modified nearest neighbor technique to reduce the large number of subclusters. Thus we combine the advantage of the k-means (speed) with that of the nearest neighbor technique (accuracy). In order to achieve a rapid analysis, no complex data transformations such as principal components analysis were used. \ud Results of the cluster analysis on both real and artificial flow cytometric data are presented and discussed. The results show that it is possible to get very good cluster analysis partitions, which compare favorably with manually gated analysis in both time and in reliability, using a personal computer

A new principle of cell sorting by using selective electroporation in a modified flow cytometer

When a strong electric field pulse of a few microseconds is applied to biological cells, small pores are formed in the cell membranes; this process is called electroporation. At high field strengths and/or long pulse durations the membranes will be damaged permanently. This eventually leads to cell kill. \ud We have developed a modified flow cytometer in which one can electroporate individual cells selected by optical analysis. The first experiments with this flow cytometer were designed to use it as a damaging sorter; we used electric pulses of 10 s and resulting field strengths of 2.0 and 3.2 X 106 V/m to kill K562 cells and lymphocytes respectively. The hydrodynamically focused cells are first optically analyzed in the usual way in a square flow channel. At the end of this channel the cells are forced to flow through a small Coulter orifice, into a wider region. If optical analysis indicates that a cell is unwanted, the cell is killed by applying a strong electric field across the Coulter orifice. The wanted living cells can be subsequently separated from the dead cells and cell fragments by a method suitable for the particular application (e.g., centrifugation, cell growth, density gradient, etc.). \ud The results of these first experiments demonstrate that by using very simple equipment, sorting by selective killing with electric fields is possible at rates of 1,000 cells/s with a purity of the sorted fraction of 99.9%

A flow cytometric study of the membrane potential of natural killer and k562 cells during the cytotoxic process

This study demonstrates that it is possible to investigate the membrane potential of interacting cells during the cytotoxic process using flow cytometry. Changes in the membrane potential of NK and K562 cells, involved in a cell-mediated cytotoxic process, were studied by standard and slit-scan flow cytometry, using the membrane potential sensitive fluorescent probe DiBAC4(3). The NK cells were labeled with a membrane marker (TR-18 or DiI) prior to incubation with K562 cells and the conjugates that were formed could be identified on the basis of the membrane marker fluorescence and light scattering signals. With a slit-scan technique we measured the membrane potential of each cell in a conjugate separately. The results show that depolarization of the K562 cell occurs as a consequence of the cytotoxic activity of the NK cell. This depolarization appears to be an early sign of cell damage because the cell membrane still remains impermeable to propidium iodide. Our data also indicate that depolarization of the NK cell occurs as a result of its cytotoxic activity

Emerging Artificial Societies Through Learning

The NewTies project is implementing a simulation in which societies of agents are expected to de-velop autonomously as a result of individual, population and social learning. These societies are expected to be able to solve environmental challenges by acting collectively. The challenges are in-tended to be analogous to those faced by early, simple, small-scale human societies. This report on work in progress outlines the major features of the system as it is currently conceived within the project, including the design of the agents, the environment, the mechanism for the evolution of language and the peer-to-peer infrastructure on which the simulation runs.Artificial Societies, Evolution of Language, Decision Trees, Peer-To-Peer Networks, Social Learning

Minimally invasive mitral valve surgery: a systematic safety analysis

Objective Minimally invasive surgery is increasingly adopted as an alternative to conventional sternotomy for mitral valve pathology in many centres worldwide. A systematic safety analysis based on a comprehensive list of pre-specified 30-day complications defined by the Mitral Valve Academic Consortium (MVARC) criteria is lacking. The aim of the current study was to systematically analyse the safety of minimally invasive mitral valve surgery in our centre based on the MVARC definitions. Methods All consecutive patients undergoing minimally invasive mitral valve surgery through right mini-thoracotomy in our institution within 10 years were studied retrospectively. The primary outcome was a composite of 30-day major complications based on MVARC definitions. Results 745 patients underwent minimally invasive mitral valve surgery (507 repair, 238 replacement), with a mean age of 62.9±12.3 years. The repair was successful in 95.8%. Overall 30-day mortality was 1.2% and stroke rate 0.3%. Freedom from any 30-day major complications was 87.2%, and independent predictors were left ventricular ejection fraction <50% (OR 1.78; 95% CI 1.02 to 3.02) and estimated glomerular filtration rate <60 mL/min/1.73 m 2 (OR 1.98; 95% CI 1.17 to 3.26). Conclusions Minimally invasive mitral valve surgery is a safe technique and is associated with low 30-day mortality and stroke rate

Defining the concept of mental dysregulation in patients requiring ambulance and/or emergency department care: protocol for a Delphi consensus study

Introduction From the patient and staff perspective, care delivery for patients experiencing a mental health problem in ambulance and emergency department (ED) settings is challenging. There is no uniform and internationally accepted concept to reflect people with a mental health problem who require emergency care, be it for, or as a result of, a mental health or physical health problem. On initial presentation to the emergency service provider (ambulance or ED), the cause of their healthcare condition/s (mental health and/or physical health) is often initially unknown. Due to this (1) the prevalence and range of underlying causes (mental and/or physical) of the patients presenting condition is unknown; (2) misattribution of physical symptoms to a mental health problem can occur and (3) diagnosis and treatment of the initial somatic complaint and cause(s) of the mental/physical health problem may be hindered. This study will name and define a new concept: 'mental dysregulation' in the context of ambulance and ED settings. Methods and analysis A Delphi study, informed by a rapid literature review, will be undertaken. For the literature review, a steering group (ie, persons with lived experience, ED and mental health clinicians, academics) will systematically search the literature to provide a working definition of the concept: mental dysregulation. Based on this review, statements will be generated regarding (1) the definition of the concept; (2) possible causes of mental dysregulation and (3) observable behaviours associated with mental dysregulation. These statements will be rated in three Delphi rounds to achieve consensus by an international expert panel (comprising persons with lived experience, clinicians and academics). Ethics and dissemination This study has been approved by the Medical Ethical Committee of the University of Applied Sciences Utrecht (reference number: 258-000-2023_Geurt van der Glind). Results will be disseminated via peer-reviewed journal publication(s), scientific conference(s) and to key stakeholders

Armoede in kaart 2018

Armoede in Kaart 2018 is de tweede editie van de SCP-reeks over armoede in de vorm van een digitale publicatie. Iedere ‘pagina’ geeft antwoord op een onderzoeksvraag, zoals: Wat is armoede? Hoeveel armen zijn er in Nederland? Welke groepen lopen het meeste risico op armoede? En hoeveel komt een arm huishouden tekort? Het onderzoek is gebaseerd op gegevens uit 2016. Deze editie is beperkt tot de kerncijfers over armoede; in 2019 volgt een uitgebreidere versie

Armoede in kaart 2019

Armoede in kaart 2019 is de derde editie van de SCP-reeks over armoede in de vorm van een digitale publicatie. Iedere ‘pagina’ geeft antwoord op een onderzoeksvraag, zoals: Wat is armoede? Hoeveel armen zijn er in Nederland? Welke groepen lopen het meeste risico op armoede? En hoeveel komt een arm huishouden tekort? Extra in deze editie is de informatie over het aantal armen per gemeente in Nederland. Het onderzoek is gebaseerd op gegevens uit 2017

ANALYSIS: Software for Graphical Analysis of Multidimensional Flow Cytometric List Mode Data

A computer program for graphical analysis of multidimensional flow cytometric list mode data is described. The program offers one-, two-, and three-dimensional inspection of an amount of data that is only limited by disk space. Subpopulations within the original data set can be identified by setting one or more two-dimensional AND gates around them. The order of measurement can be used as a parameter for evaluation of time-dependent processes. Other new parameters can be made by zooming in on a parameter, logarithmic transformation, or division of two parameters. The program is written in Turbo Pascal and it can run on any MS-DOC PC with an EGA/VGA resolution screen

Competition for imperfect consumers

This lecture provides a selective discussion of some issues in the economics of competition for imperfect consumers. Limited consumer awareness – about what deals are on offer, or about the consequences of purchasing decisions – is a central feature of many markets. Consumer imperfection can give rise to market power, but can also co-exist with strong rivalry between firms, and then is more for ‘consumer policy’ than competition policy. Two recent court cases illustrate some of the issues involved. The lecture then reviews a line of theoretical work on competition for imperfect consumers. The analysis highlights some policy tradeoffs, and a key theme is how patterns of consumer awareness matter for patterns of competition among firms