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- ENaC (3)
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- sodium channel (2)
The ability to breathe air represents a fundamental step in vertebrate evolution that was accompanied by several anatomical and physiological adaptations. The morphology of the air-blood barrier is highly conserved within air-breathing vertebrates. It is formed by three different plies, which are represented by the alveolar epithelium, the basal lamina, and the endothelial layer. Besides these conserved morphological elements, another common feature of vertebrate lungs is that they contain a certain amount of fluid that covers the alveolar epithelium. The volume and composition of the alveolar fluid is regulated by transepithelial ion transport mechanisms expressed in alveolar epithelial cells. These transport mechanisms have been reviewed extensively. Therefore, the present review focuses on the properties and functional significance of the alveolar fluid. How does the fluid enter the alveoli? What is the fate of the fluid in the alveoli? What is the function of the alveolar fluid in the lungs? The review highlights the importance of the alveolar fluid, its volume and its composition. Maintenance of the fluid volume and composition within certain limits is critical to facilitate gas exchange. We propose that the alveolar fluid is an essential element of the air-blood barrier. Therefore, it is appropriate to refer to this barrier as being formed by four plies, namely (1) the thin fluid layer covering the apical membrane of the epithelial cells, (2) the epithelial cell layer, (3) the basal membrane, and (4) the endothelial cells.
The vectorial transport of Na+ across epithelia is crucial for the maintenance of Na+ and water homeostasis in organs such as the kidneys, lung, or intestine. Dysregulated Na+ transport processes are associated with various human diseases such as hypertension, the salt-wasting syndrome pseudohypoaldosteronism type 1, pulmonary edema, cystic fibrosis, or intestinal disorders, which indicate that a precise regulation of epithelial Na+ transport is essential. Novel regulatory signaling molecules are gasotransmitters. There are currently three known gasotransmitters: nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S). These molecules are endogenously produced in mammalian cells by specific enzymes and have been shown to regulate various physiological processes. There is a growing body of evidence which indicates that gasotransmitters may also regulate Na+ transport across epithelia. This review will summarize the available data concerning NO, CO, and H2S dependent regulation of epithelial Na+ transport processes and will discuss whether or not these mediators can be considered as true physiological regulators of epithelial Na+ transport biology.
Wesch D, Althaus M, Miranda P, Cruz-Muros I, Fronius M, Gonzalez-Hernandez T, Clauss WG, de la Rosa DA, Giraldez T. Differential N termini in epithelial Na+ channel delta-subunit isoforms modulate channel trafficking to the membrane. Am J Physiol Cell Physiol 302: C868-C879, 2012. First published December 7, 2011; doi: 10.1152/ajpcell.00255.2011.-The epithelial Na+ channel (ENaC) is a heteromultimeric ion channel that plays a key role in Na+ reabsorption across tight epithelia. The canonical ENaC is formed by three analogous subunits, alpha, beta, and gamma. A fourth ENaC subunit, named delta, is expressed in the nervous system of primates, where its role is unknown. The human delta-ENaC gene generates at least two splice isoforms, delta(1) and delta(2), differing in the N-terminal sequence. Neurons in diverse areas of the human and monkey brain differentially express either delta(1) or delta(2), with few cells coexpressing both isoforms, which suggests that they may play specific physiological roles. Here we show that heterologous expression of delta(1) in Xenopus oocytes and HEK293 cells produces higher current levels than delta(2). Patch-clamp experiments showed no differences in single channel current magnitude and open probability between isoforms. Steady-state plasma membrane abundance accounts for the dissimilarity in macroscopic current levels. Differential trafficking between isoforms is independent of beta- and gamma-subunits, PY-motif-mediated endocytosis, or the presence of additional lysine residues in delta(2)-N terminus. Analysis of delta(2)-N terminus identified two sequences that independently reduce channel abundance in the plasma membrane. The delta(1) higher abundance is consistent with an increased insertion rate into the membrane, since endocytosis rates of both isoforms are indistinguishable. Finally, we conclude that delta-ENaC undergoes dynamin-independent endocytosis as opposed to alpha beta gamma-channels.
The gasotransmitter hydrogen sulphide decreases Na⁺ transport across pulmonary epithelial cells
(2012)
BACKGROUND AND PURPOSE The transepithelial absorption of Na(+) in the lungs is crucial for the maintenance of the volume and composition of epithelial lining fluid. The regulation of Na(+) transport is essential, because hypo- or hyperabsorption of Na(+) is associated with lung diseases such as pulmonary oedema or cystic fibrosis. This study investigated the effects of the gaseous signalling molecule hydrogen sulphide (H(2) S) on Na(+) absorption across pulmonary epithelial cells. EXPERIMENTAL APPROACH Ion transport processes were electrophysiologically assessed in Ussing chambers on H441 cells grown on permeable supports at air/liquid interface and on native tracheal preparations of pigs and mice. The effects of H(2)S were further investigated on Na(+) channels expressed in Xenopus oocytes and Na(+) /K(+)-ATPase activity in vitro. Membrane abundance of Na(+) /K(+)-ATPase was determined by surface biotinylation and Western blot. Cellular ATP concentrations were measured colorimetrically, and cytosolic Ca(2+) concentrations were measured with Fura-2. KEY RESULTS H(2)S rapidly and reversibly inhibited Na(+) transport in all the models employed. H(2)S had no effect on Na(+) channels, whereas it decreased Na(+) /K(+)-ATPase currents. H(2)S did not affect the membrane abundance of Na(+) /K(+)-ATPase, its metabolic or calcium-dependent regulation, or its direct activity. However, H(2)S inhibited basolateral calcium-dependent K(+) channels, which consequently decreased Na(+) absorption by H441 monolayers. CONCLUSIONS AND IMPLICATIONS H(2) S impairs pulmonary transepithelial Na(+) absorption, mainly by inhibiting basolateral Ca(2+)-dependent K(+) channels. These data suggest that the H(2)S signalling system might represent a novel pharmacological target for modifying pulmonary transepithelial Na(+) transport.
Malware is responsible for massive economic damage. Being the preferred tool for digital crime, botnets are becoming increasingly sophisticated, using more and more resilient, distributed infrastructures based on peer-to-peer (P2P) protocols. On the other side, current investigation techniques for malware and botnets on a technical level are time-consuming and highly complex. Fraunhofer FKIE is addressing this problem, researching new ways of intelligent process automation and information management for malware analysis in order to minimize the time needed to investigate these threats.
Today’s computer systems face a vast array of severe threats that are posed by automated attacks performed by malicious software as well as manual attacks by individual humans. These attacks not only differ in their technical implementation but may also be location-dependent. Consequentially, it is necessary to join the information from heterogeneous and distributed attack sensors in order to acquire comprehensive information on current ongoing cyber attacks.
Development and Validation of a Rapid and Reliable Method for TPMT Genotyping using real-time PCR
(2012)
Education is widely seen as an important means of addressing both national and international problems, such as political or religious extremism, poverty, and hunger. However, if developing countries are to become societies that can compete properly with Western industrialized countries, not only is a fundamental shift in thinking with regard to the value of education and more/better provision of teaching required, but strong support from other countries is needed as well. This article explores questions such as whether Western policymakers can avoid a repetition of some of the failures of the past few decades in terms of providing foreign aid; how educators and providers of educational scenarios and learning contents can foster and manage the creation of a worldwide knowledge society; and in particular, if the provision of open educational resources (OER) can realistically overcome the educational gap and foster educational justice.
Disorders of the degradation of branched chain amino acids: what is new in clinics and laboratories?
(2012)
Molybdenum cofactor deficiency (MoCD) is a rare inherited metabolic disorder characterized by severe and progressive neurological damage mainly caused by the loss of sulfite oxidase activity. Elevated urinary levels of sulfite, thiosulfate, and S-sulfocysteine (SSC) are hallmarks in the diagnosis of MoCD and sulfite oxidase deficiency (SOD). Recently, a first successful treatment of a human MoCD type A patient based on a substitution therapy with the molybdenum cofactor precursor cPMP has been reported, resulting in nearly complete normalization of MoCD biomarkers. Knowing the rapid progression of the disease symptoms in nontreated patients, an early diagnosis of MoCD as well as a sensitive method to monitor daily changes in SSC levels, a key marker of sulfite toxicity, is crucial for treatment outcome. Here, we describe a fast and sensitive method for the analysis of SSC in human urine samples using high performance liquid chromatography (HPLC). The analysis is based on precolumn derivatization with O-phthaldialdehyde (OPA) and separation on a C18 reverse phase column coupled to UV detection. The method was extended to human serum analysis and no interference with endogenous amino acids was found. Finally, SSC values from 45 pediatric urine, 75 adult urine, and 24 serum samples from control individuals as well as MoCD patients are reported. Our method represents a cost-effective technique for routine diagnosis of MoCD and SOD, and can be used also to monitor treatment efficiency in those sulfite toxicity disorders on a daily basis.
The osmolality of nonionic, iodinated contrast agents as an important factor for renal safety
(2012)
Software testing in web services environment faces different challenges in comparison with testing in traditional software environments. Regression testing activities are triggered based on software changes or evolutions. In web services, evolution is not a choice for service clients. They have always to use the current updated version of the software. In addition test execution or invocation is expensive in web services and hence providing algorithms to optimize test case generation and execution is vital. In this environment, we proposed several approach for test cases' selection in web services' regression testing. Testing in this new environment should evolve to be included part of the service contract. Service providers should provide data or usage sessions that can help service clients reduce testing expenses through optimizing the selected and executed test cases.
Oft wird die Gewinnung von Gastärzten aus dem Ausland als Möglichkeit zur kurz- und mittelfristigen Deckung des Ärztebedarfs in Kliniken in Erwägung gezogen. Die hohen Anforderungen von Landesprüfungsämtern, Arbeitsagenturen, Ausländerbehörden und Botschaften erweisen sich sowohl für Ärzte als auch Kliniken als schwer überwindbare Hürden. Insbesondere Sprachschwierigkeiten sowie mangelhafte fachliche und kulturelle Kenntnisse der internationalen Ärzte sind ohne professionelle Unterstützung kaum zu kompensieren.
In a research project funded by the German Research Foundation, meteorologists, data publication experts, and computer scientists optimised the publication process of meteorological data and developed software that supports metadata review. The project group placed particular emphasis on scientific and technical quality assurance of primary data and metadata. At the end, the software automatically registers a Digital Object Identifier at DataCite. The software has been successfully integrated into the infrastructure of the World Data Center for Climate, but a key was to make the results applicable to data publication processes in other sciences as well.
The criteria for assessing the quality of rubber materials are the polymer or copolymer composition and the additives. These additives include plasticizers, extender oils, carbon black, inorganic fillers, antioxidants, heat and light stabilizers, processing aids, cross-linking agents, accelerators, retarders, adhesives, pigments, smoke and flame retardants, and others. Determination of additives in polymers or copolymers generally requires the extraction of these substances from the matrix as a first step, which can be challenging, and the subsequent analysis of the extracted additives by gas chromatography (GC), GC–mass spectrometry (MS), high performance liquid chromatography (HPLC), HPLC–MS, capillary electrophoresis, thin-layer chromatography, and other analytical techniques. In the present work, nitrile rubber materials were studied using direct analytical flash pyrolysis hyphenated to GC and electrospray ionization MS in both scan and selected ion monitoring modes to demonstrate that this technique is a good tool to identify the organic additives in nitrile rubber.
In this paper, various enhanced sales forecast methodologies and models for the automobile market are presented. The methods used deliver highly accurate predictions while maintaining the ability to explain the underlying model at the same time. The representation of the economic training data is discussed, as well as its effects on the newly registered automobiles to be predicted. The methodology mainly consists of time series analysis and classical Data Mining algorithms, whereas the data is composed of absolute and/or relative market-specific exogenous parameters on a yearly, quarterly, or monthly base. It can be concluded that the monthly forecasts were especially improved by this enhanced methodology using absolute, normalized exogenous parameters. Decision Trees are considered as the most suitable method in this case, being both accurate and explicable. The German and the US-American automobile market are presented for the evaluation of the forecast models.
In this work, preceramic papers containing 85 wt% Al2O3 were heat-treated at 1600 °C to obtain paper-derived ceramics. In order to increase the preceramic paper density prior to sintering, the papers were calendered at different roll temperatures and pressures. The influences of the calendering parameters on the microstructure and mechanical properties of the preceramic papers and the paper-derived ceramics were investigated. It was expected that especially the mechanical properties of the papers and derived ceramics would be improved by calendering.
Warum wir tun, was andere wollen: Psychologische Determinanten informeller Macht in Organisationen
(2012)
Auf dem Weg zur Promotion: Zur Benachteiligung von Fachhochschul-Absolventinnen und -Absolventen
(2012)
Das Team aus Sascha Czornohus, Katrin Dobersalske, Fabian Heuel und Nina Petrow bearbeitet mit seinem „Aufsatz Auf dem Weg zur Promotion: Strukturelle Benachteiligung von Fachhochschul-Absolventinnen und -Absolventen“ ein hochschulpolitisch brisantes und daher sensibles Thema, das die Hochschulpolitik inzwischen in offener Auseinandersetzung beschäftigt. Seit die Forschung unstreitig zu den Aufgaben der Fachhochschulen zählt, Promotion zu den Berufungsvoraussetzungen an ihnen gehört und alle Professoren an Universitäten ausgebildet wurden, wurde die Forderung nach Promotionszugängen für die Master-Absolventen der Fachhochschulen immer lauter. Teillösungen wurden gefunden, aber die Debatte wird breiter und umfasst inzwischen (auf dem Hintergrund der Profil- und Schwerpunktbildung mit sehr unterschiedlichem Ausbau der Fächer) die Frage, ob überhaupt ganzen Hochschulen das Promotionsrecht verliehen werden sollte oder von Fachbereich zu Fachbereich verschieden – auch bei Universitäten. Die Überzeugung, dass die Verteilung des Promotionsrechts in Deutschland überprüft werden sollte, breitet sich aus. Das HSW ist an der breiteren Diskussion dieses Themas interessiert.
Handlungsspielräume zur Gestaltung nachhaltiger Mobilität werden unzulänglich genutzt. Wissenschaftliche Erkenntnisse aus Gesundheit, Umwelt und Verkehr finden zögerlich Eingang in Verkehrspolitik. Konkurrenz der Ministerien für Wirtschaft, Verkehr, Umwelt und Gesundheit hindert an der Wahrnehmung der Wertschöpfung nachhaltiger Mobilität. Bemühungen um eine Entlastung der Innenstädte sind von effizienter Prävention weit entfernt, externe Kosten werden ignoriert. Biokraftstoffpflanzungen (mit Raubbau an Regenwäldern) erhöhen die Emissionen der industrialisierten Landwirtschaft und ruinieren Wasserressourcen. Diese Verschiebung in andere klimagasrelevante Produktionsbereiche verschlimmert die globalen CO2-Bilanzen. Wenige Einzelfälle sind verkehrs-ökologisch am Verursacherprinzip orientiert (z. B. in Österreich). Die WHO stellt Wissen bereit, unerwünschte Effekte vermeidbar zu machen. Über vermeidbare Gesundheitsfolgekosten (Atemwegserkrankungen, Übergewicht) liegt zwar genügend Material vor. Transdisziplinäre Betrachtungen der Wertschöpfung werden aber als nicht umsetzbar abqualifiziert.
Human mesenchymal stem cells (hMSCs) are considered a promising cell source for regenerative medicine, because they have the potential to differentiate into a variety of lineages among which the mesoderm-derived lineages such adipo- or osteogenesis are investigated best. Human MSCs can be harvested in reasonable to large amounts from several parts of the patient’s body and due to this possible autologous origin, allorecognition can be avoided. In addition, even in allogenic origin-derived donor cells, hMSCs generate a local immunosuppressive microenvironment, causing only a weak immune reaction. There is an increasing need for bone replacement in patients from all ages, due to a variety of reasons such as a new recreational behavior in young adults or age-related diseases. Adipogenic differentiation is another interesting lineage, because fat tissue is considered to be a major factor triggering atherosclerosis that ultimately leads to cardiovascular diseases, the main cause of death in industrialized countries. However, understanding the differentiation process in detail is obligatory to achieve a tight control of the process for future clinical applications to avoid undesired side effects. In this review, the current findings for adipo- and osteo-differentiation are summarized together with a brief statement on first clinical trials.
The biological effects of bilirubin, still poorly understood, are concentration-dependent ranging from cell protection to toxicity. Here we present data that at high nontoxic physiological concentrations, bilirubin inhibits growth of proliferating human coronary artery smooth muscle cells by three events. It impairs the activation of Raf/ERK/MAPK pathway and the cellular Raf and cyclin D1 content that results in retinoblastoma protein hypophosphorylation on amino acids S608 and S780. These events impede the release of YY1 to the nuclei and its availability to regulate the expression of genes and to support cellular proliferation. Moreover, altered calcium influx and calpain II protease activation leads to proteolytical degradation of transcription factor YY1. We conclude that in the serum-stimulated human vascular smooth muscle primary cell cultures, bilirubin favors growth arrest, and we propose that this activity is regulated by its interaction with the Raf/ERK/MAPK pathway, effect on cyclin D1 and Raf content, altered retinoblastoma protein profile of hypophosphorylation, calcium influx, and YY1 proteolysis. We propose that these activities together culminate in diminished 5 S and 45 S ribosomal RNA synthesis and cell growth arrest. The observations provide important mechanistic insight into the molecular mechanisms underlying the transition of human vascular smooth muscle cells from proliferative to contractile phenotype and the role of bilirubin in this transition.
Transient up-regulation of P2 receptors influence differentiation of human mesenchymal stem cells
(2012)
After more than twenty years of research, the molecular events of apoptotic cell death can be succinctly stated; different pathways, activated by diverse signals, increase the activity of proteases called caspases that rapidly and irreversibly dismantle condemned cell by cleaving specific substrates. In this time the ideas that apoptosis protects us from tumourigenesis and that cancer chemotherapy works by inducing apoptosis also emerged. Currently, apoptosis research is shifting away from the intracellular events within the dying cell to focus on the effect of apoptotic cells on surrounding tissues. This is producing counterintuitive data showing that our understanding of the role of apoptosis in tumourigenesis and cancer therapy is too simple, with some interesting and provocative implications. Here, we will consider evidence supporting the idea that dying cells signal their presence to the surrounding tissue and, in doing so, elicit repair and regeneration that compensates for any loss of function caused by cell death. We will discuss evidence suggesting that cancer cell proliferation may be driven by inappropriate or corrupted tissue-repair programmes that are initiated by signals from apoptotic cells and show how this may dramatically modify how we view the role of apoptosis in both tumourigenesis and cancer therapy.
Sicherheit im Fährverkehr
(2012)
People with type 2 Diabetes have an elevated risk for developing cardiovascular disease (CVD) for which dyslipidemia is the major contributor. Diabetic patients have characteristic pattern of dyslipidemia with decreased level of high density lipoprotein cholesterol (HDL-C) and elevated triglycerides (TG) level. However, in diabetes mellitus, low density lipoprotein cholesterol (LDL-C) which is used as one of the markers for the risk of CVD, is underestimated so in such cases the levels of non-High density lipoprotein cholesterol (non-HDL-C) can be a stronger predictor of CVD as it strongly correlates with atherogenic lipoproteins. Therefore, an attempt has been made to evaluate the level of non-HDL-C as a newer marker for the risk of cardiovascular disease and to fi nd out the pattern of dyslipidemia in diabetes mellitus. The present study comprised of 82 type 2 Diabetic cases and 81 non-diabetic controls. Among the diabetics, the majority of the subjects (61.0%) were HDL-C dyslipidemic. However, among the controls, the maximum numbers of individuals (40.7%) were TG dyslipidemic. Diabetics have signifi cantly elevated ratio of total cholesterol to high density lipoprotein cholesterol (TC/HDL-C) and the signifi cant increased levels of non-high density lipoprotein cholesterol (non-HDL-C) compared to controls which can be used as markers of dyslipidemia and can also be used to predict the risk of cardiovascular disease in type 2 Diabetes Mellitus.
Anfang Januar 2007 trat in Nordrhein-Westfalen (NRW) das Hochschulfreiheitsgesetz (HFG) in Kraft. Mit dem HFG hat sich die Landesregierung in NRW weit aus der Detailsteuerung der Hochschulen zurückgezogen und tritt lediglich noch für existenzielle Schadensereignisse ein. So sind die Hochschulen – Universitäten und Fachhochschulen – in NRW keine staatlichen Einrichtungen mehr, sondern Körperschaften des öffentlichen Rechts in staatlicher Trägerschaft. Hiermit folgt das neue Hochschulgesetz dem hochschulpolitischen Paradigmenwechsel von einem staatlich geplanten, weitgehend einheitlich gestalteten System zu einem durch Profilbildung und Wettbewerb geprägten Hochschulsystem. In diesem Artikel werden die damit verbundenen Problemstellungen und Lösungsoptionen aufgezeigt und als Empfehlung die Einführung eines Chancen- und Risikomanagements beschrieben.
Open Source ERP-Systeme
(2012)
Mit Free and Open Source Software können die IT-Kosten in erheblichem Umfang gesenkt werden. Wegen ihres hohen Durchdringungsgrades in Unternehmen und des damit verbundenen Kostenblocks gilt dies insbesondere für Free and Open Source (FOS-) ERP-Systeme. Zwar sind die Verbreitung und die Akzeptanz von FOS-ERP-Systemen in den letzten Jahren schon stark angewachsen, durch eine verbesserte Markttransparenz lassen sich aber noch weitere Potenziale erschließen. Bestehende Marktübersichten für FOS-ERP-Systeme sind jedoch wenig umfassend. Vor diesem Hintergrund wurde ein Marktspiegel mit detaillierten Angaben zu den verschiedenen FOS-ERP-Systemen erstellt.
ERP systems are being used throughout the whole enterprise and are therefore responsible for a high percentage of IT expenses. The use of Free and Open Source ERP systems (FOS ERP systems) can help to reduce these IT costs. Though the acceptance of FOS ERP systems has increased enormously in the last years, even more entreprises would use FOS ERP systems to support their order processing, if the FOS ERP market was more transparent. Existing market surveys are less comprehensive. Therefore, a detailed market guide was developed.
We present our approach to extend a Virtual Reality software framework towards the use for Augmented Reality applications. Although VR and AR applications have very similar requirements in terms of abstract components (like 6DOF input, stereoscopic output, simulation engines), the requirements in terms of hardware and software vary considerably. In this article we would like to share the experience gained from adapting our VR software framework for AR applications. We will address design issues for this task. The result is a VR/AR basic software that allows us to implement interactive applications without fixing their type (VR or AR) beforehand. Switching from VR to AR is a matter of changing the configuration file of the application. We also give an example of the use of the extended framework: Augmenting the magnetic field of bar magnets in physics classes. We describe the setup of the system and the real-time calculation of the magnetic field, using a GPU.
Using virtual environment systems for road safety education requires a realistic simulation of road traffic. Current traffic simulations are either too restricted in their complexity of agent behavior or focus on aspects not important in virtual environments. More importantly, none of them are concerned with modeling misbehavior of traffic participants which is part of every-day traffic and should therefore not be neglected in this context. We present a concept for a traffic simulation that addresses the need for more realistic agent behavior with regard to road safety education. The two major components of this concept are a simulation of persistent agents which minimizes computational overhead and a model of cognitive processes of human drivers combined with psychological personality profiles to allow for individual behavior and misbehavior.
The relative contributions of radial and laminar optic flow to the perception of linear self-motion
(2012)
When illusory self-motion is induced in a stationary observer by optic flow, the perceived distance traveled is generally overestimated relative to the distance of a remembered target (Redlick, Harris, & Jenkin, 2001): subjects feel they have gone further than the simulated distance and indicate that they have arrived at a target's previously seen location too early. In this article we assess how the radial and laminar components of translational optic flow contribute to the perceived distance traveled. Subjects monocularly viewed a target presented in a virtual hallway wallpapered with stripes that periodically changed color to prevent tracking. The target was then extinguished and the visible area of the hallway shrunk to an oval region 40° (h) × 24° (v). Subjects either continued to look centrally or shifted their gaze eccentrically, thus varying the relative amounts of radial and laminar flow visible. They were then presented with visual motion compatible with moving down the hallway toward the target and pressed a button when they perceived that they had reached the target's remembered position. Data were modeled by the output of a leaky spatial integrator (Lappe, Jenkin, & Harris, 2007). The sensory gain varied systematically with viewing eccentricity while the leak constant was independent of viewing eccentricity. Results were modeled as the linear sum of separate mechanisms sensitive to radial and laminar optic flow. Results are compatible with independent channels for processing the radial and laminar flow components of optic flow that add linearly to produce large but predictable errors in perceived distance traveled.
For the case when the abstraction of instantaneous state transitions is adopted, this paper proposes to start fault detection and isolation in an engineering system from a single time-invariant causality bond graph representation of a hybrid model. To that end, the paper picks up on a long-known proposal to model switching devices by a transformer modulated by a Boolean variable and a resistor in fixed conductance causality accounting for its ON resistance. Bond graph representations of hybrid system models developed in this way have been used so far mainly for the purpose of simulation. The paper shows that they can well constitute an approach to the bond-graph-based quantitative fault detection and isolation of hybrid models. Advantages are that the standard sequential causality assignment procedure can be a used without modification. A single set of analytical redundancy relations valid for all physically feasible system modes can be (automatically) derived from the bond graph. Stiff model equations due to small values of the ON resistance in the switch model may be avoided by symbolic reformulation of equations and letting the ON resistance of some switches tend to zero, turning them into ideal switches.
First, for two examples considered in the literature, it is shown that the approach proposed in this paper can produce the same analytical redundancy relations as were obtained from a hybrid bond graph with controlled junctions and the use of a sequential causality assignment procedure especially for fault detection and isolation purpose. Moreover, the usefulness of the proposed approach is illustrated in two case studies by its application to standard switching circuits extensively used in power electronic systems and by simulation of some fault scenarios. The approach, however, is not confined to the fault detection and isolation of such systems. Analytically validated simulation results obtained by means of the program Scilab give confidence in the approach.
A bond graph representation of switching devices known for a long time has been a modulated transformer with a modulus b(t)∈{0,1}∀t≥0 in conjunction with a resistor R:Ron accounting for the ON-resistance of a switch considered non-ideal. Besides other representations, this simple model has been used in bond graphs for simulation of the dynamic behaviour of hybrid systems. A previous article of the author has proposed to use the transformer–resistor pair in bond graphs for fault diagnosis in hybrid systems. Advantages are a unique bond graph for all system modes, the application of the unmodified standard Sequential Causality Assignment Procedure, fixed computational causalities and the derivation of analytical redundancy relations incorporating ‘Boolean’ transformer moduli so that they hold for all system modes. Switches temporarily connect and disconnect model parts. As a result, some independent storage elements may temporarily become dependent, so that the number of state variables is not time-invariant. This article addresses this problem in the context of modelling and simulation of fault scenarios in hybrid systems. In order to keep time-invariant preferred integral causality at storage ports, residual sinks previously introduced by the author are used. When two storage elements become dependent at a switching time instance ts, a residual sink is activated. It enforces that the outputs of two dependent storage elements become immediately equal by imposing the conjugate3 power variable of appropriate value on their inputs. The approach is illustrated by the bond graph modelling and simulation of some fault scenarios in a standard three-phase switched power inverter supplying power into an RL-load in a delta configuration. A well-developed approach to model-based fault detection and isolation is to evaluate the residual of analytical redundancy relations. In this article, analytical redundancy relation residuals have been computed numerically by coupling a bond graph of the faulty system to one of the non-faulty systems by means of residual sinks. The presented approach is not confined to power electronic systems but can be used for hybrid systems in other domains as well. In further work, the RL-load may be replaced by a bond graph model of an alternating current motor in order to study the effect of switch failures in the power inverter on to the dynamic behaviour of the motor.
This article concerns with the accessibility of Business process modelling tools (BPMo tools) and business process modelling languages (BPMo languages). Therefore the reader will be introduced to business process management and the authors' motivation behind this inquiry. Afterwards, the paper will reflect problems when applying inaccessible BPMo tools. To illustrate these problems the authors distinguish between two different categories of issues and provide practical examples. Finally the article will present three approaches to improve the accessibility of BPMo tools and BPMo languages.
Jede Führungskraft hat ein bestimmtes Menschenbild, das ihre Arbeit und den Umgang mit den Mitarbeitern prägt. Diese Menschenbilder sind auch einem historischen Wandel unterworfen. Denn im Lauf der Jahrzehnte haben sich unsere Vorstellungen vom Menschen als Mitarbeiter grundlegend gewandelt. Welche Konsequenzen dieser Wandel für die Mitarbeiterführung hat, untersucht der folgende Artikel.