Increasing the simulation performance of large-scale evacuations using parallel computing techniques based on domain decomposition

Evacuation simulation has the potential to be used as part of a decision support system during large-scale incidents to provide advice to incident commanders. To be viable in these applications, it is essential that the simulation can run many times faster than real time. Parallel processing is a method of reducing run times for very large computational simulations by distributing the workload amongst a number of processors. This paper presents the development of a parallel version of the rule based evacuation simulation software buildingEXODUS using domain decomposition. Four Case Studies (CS) were tested using a cluster, consisting of 10 Intel Core 2 Duo (dual core) 3.16 GHz CPUs. CS-1 involved an idealised large geometry, with 20 exits, intended to illustrate the peak computational speed up performance of the parallel implementation, the population consisted of 100,000 agents; the peak computational speedup (PCS) was 14.6 and the peak real-time speedup (PRTS) was 4.0. CS-2 was a long area with a single exit area with a population of 100,000 agents; the PCS was 13.2 and the PRTS was 17.2. CS-3 was a 50 storey high rise building with a population of 8000/16,000 agents; the PCS was 2.48/4.49 and the PRTS was 17.9/12.9. CS-4 is a large realistic urban area with 60,000/120,000 agents; the PCS was 5.3/6.89 and the PRTS was 5.31/3.0. This type of computational performance opens evacuation simulation to a range of new innovative application areas such as real-time incident support, dynamic signage in smart buildings and virtual training environments

Assorted effects of TGFβ and chondroitinsulfate on p38 and ERK1/2 activation levels in human articular chondrocytes stimulated with LPS

SummaryObjectivesInadequate cellular response of chondrocytes to stress frequently terminates in osteoarthritis (OA). Adequate response is fundamentally modulated by concerted cytokine signaling events, directing degradation and synthesis of cartilage on articular surfaces where and whenever necessary. Transforming growth factor (TGF)β is a prominent mediator in cartilage anabolism, although particular catabolic activities are occasionally reported. Clearly, before the TGFβ signal gets through to the gene regulatory machinery, cross talk with modulators occurs.MethodWe tested the hypothesis whether chondroitinsulfate (CS) modulates cell signaling. TGFβ and/or soluble CS was added to human articular chondrocytes (HACs) and activation of p38 and extracellular signal related kinase (ERK)1/2 was determined by immunoblot analysis. Expression levels of mRNA of matrix metalloproteinase (MMP)-2, -3 and -13 were determined by real-time polymerase chain reaction (PCR).ResultsNo significant effects were observed unless cells were stimulated with lipopolysaccharide (LPS), invigorating catabolic metabolism in chondrocytes. LPS effects, however, were profoundly modulated by TGFβ, CS and both applied in combination. Most prominent, the silencing of p38 stress signal by CS was superimposable to that of TGFβ. Phospho-ERK1/2 levels were raised by TGFβ three-fold over LPS induced levels. In contrast, CS treatment, alone or combined with TGFβ, reduced phosphorylation significantly below LPS induced levels. Finally, suppression of LPS induced MMP-13 mRNA levels resulted with CS.ConclusionSoluble CS modulates signaling events in chondrocytes concurrent with MMP-13 down regulation. The effects observed suggest a feedback signaling mechanism cross talking with TGFβ-signal pathways and may serve an explanation, on the cellular level, for the beneficial effects found in clinical studies with pharmacologic application of CS

Entwicklung und Validierung der in vivo zeitharmonischen Ultraschall-Elastografie des menschlichen Gehirns für die klinische Anwendung

Motivation: In neurology, the determination of intracranial pressure (ICP) is of central importance for the diagnosis of brain damage. However, reliable ICP measurements are realized by invasive techniques such as lumbar puncture or surgically implanted pressure probes. Cerebral stiffness (CS) measured by elastography could be a parameter sensitive to ICP variations. However, CS is currently measured exclusively by magnetic resonance elastography, which is associated with long examinations and limited availability. Time harmonic shear wave excitation used in magnetic resonance elastography combined with transcranial ultrasound (cerebral THE) can provide reproducible and stable elastograms over a large field-of-view in real-time. Initial applications of cerebral THE in healthy volunteers during performance of the Valsalva maneuver demonstrated sensitivity of CS to blood flow and pressure changes in the brain. The goal of this PhD project was to optimize and validate cerebral THE that I previously developed to quantify CS, identify it as a marker of cerebral perfusion, and provide initial evidence for the potential clinical application of the method as a noninvasive technique for estimating ICP. Methods: To this end, I conducted two studies in healthy volunteers aimed at artificial manipulation of cerebral blood flow: (i) I investigated the effect of hypercapnia during breathing of carbon dioxide-enriched gas and (ii) the effect of dehydration and oral rehydration on CS measured by cerebral THE. Finally, I applied cerebral THE in a pilot clinical study in patients with idiopathic intracranial hypertension (IIH) who underwent lumbar puncture (LP) along with invasive quantification of cerebrospinal fluid (CSF) opening pressure and, if necessary, CSF drainage. Results: Hypercapnia increased CS by 6 ± 4% above baseline. In contrast, dehydration of healthy volunteers resulted in a decrease in CS of 4 ± 2%, whereas CS returned to baseline after oral rehydration. In patients with IIH, CS was 16 ± 5% higher than in healthy volunteers and correlated positively with CSF opening pressure (r = 0:69, p < 0:001). Approximately 30 min after LP, patients’ CS values were within the range of CS values in healthy volunteers. Conclusion: Cerebral THE proved to be a reproducible, stable imaging technique for real-time determination of CS. This project demonstrated that changes in CS are closely associated with changes in cerebral perfusion and ICP. These results suggest that cerebral THE may be a promising noninvasive diagnostic tool for determining ICP in routine clinical practice.Motivation: In der Neurologie ist die Bestimmung des intrakraniellen Drucks (ICP) von zentraler Bedeutung für die Diagnose von Hirnschäden. Zuverlässige ICP-Messungen werden jedoch durch invasive Techniken wie die Lumbalpunktion oder chirurgisch implantierte Drucksonden realisiert. Die mittels Elastografie gemessene zerebrale Steifigkeit (CS) könnte ein Parameter sein, der empfindlich auf ICP-Schwankungen reagiert. Allerdings wird die CS derzeit ausschließlich mit der Magnetresonanz-Elastografie gemessen, die mit langen Untersuchungen und begrenzter Verfügbarkeit verbunden ist. Zeitharmonische Scherwellenanregung, wie sie in der Magnetresonanz-Elastografie verwendet wird, kombiniert mit transkraniellem Ultraschall (zerebrale THE) kann reproduzierbare, stabile Elastogramme über ein großes Sichtfeld in Echtzeit liefern. Erste Anwendungen der zerebralen THE bei gesunden Probanden während der Durchführung des Valsalva-Manövers zeigten, dass die CS empfindlich auf Blutflussund Druckänderungen im Gehirn reagiert. Ziel dieses Promotionsprojekts war die Optimierung und Validierung der zerebralen THE, welche ich zuvor entwickelt habe, um CS zu quantifizieren, als Marker für zerebrale Perfusion zu identifizieren und erste Beweise für die potenzielle klinische Anwendung der Methode als nichtinvasive Technik zur Abschätzung des ICP zu liefern. Methoden: Zu diesem Zweck führte ich zwei Studien an gesunden Probanden durch, welche die künstliche Manipulation des zerebralen Blutflusses zum Ziel hatten: (i) Ich untersuchte die Auswirkung von Hyperkapnie während der Atmung von mit Kohlendioxid angereichertem Gas und (ii) die Auswirkung von Dehydrierung und oraler Rehydrierung auf die durch zerebrale THE gemessene CS. Schließlich habe ich die zerebrale THE in einer klinischen Pilotstudie bei Patienten mit idiopathischer intrakranieller Hypertension (IIH) angewandt, bei denen eine Lumbalpunktion (LP) zusammen mit einer invasiven Quantifizierung des Liquoröffnungsdrucks und, falls erforderlich, einer Liquordrainage durchgeführt wurde. Ergebnisse: Hyperkapnie erhöhte den CS um 6 4% über den Ausgangswert. Im Gegensatz dazu führte die Dehydratation gesunder Probanden zu einem Rückgang des CS um 4 2%, während der CS nach oraler Rehydrierung wieder den Ausgangswert erreichte. Bei Patienten mit IIH war die CS um 16 5% höher als bei gesunden Probanden und korrelierte positiv mit dem Liquoröffnungsdruck (r = 0:69, p < 0:001). Etwa 30 Minuten nach der LP lagen die CS Werte der Patienten im Bereich der CS Werte gesunder Probanden. Schlussfolgerung: Die zerebrale THE erwies sich als reproduzierbares, stabiles bildgebendes Verfahren zur Echtzeit-Bestimmung der CS. Dieses Projekt zeigte, dass Änderungen des CS eng mit Änderungen der zerebralen Perfusion und des ICP verbunden sind. Diese Ergebnisse deuten darauf hin, dass die zerebrale THE ein vielversprechendes nichtinvasives Diagnoseinstrument zur Bestimmung des ICP in der klinischen Routinepraxis sein könnte

How to find real-world applications for compressive sensing

The potential of compressive sensing (CS) has spurred great interest in the research community and is a fast growing area of research. However, research translating CS theory into practical hardware and demonstrating clear and significant benefits with this hardware over current, conventional imaging techniques has been limited. This article helps researchers to find those niche applications where the CS approach provides substantial gain over conventional approaches by articulating lessons learned in finding one such application; sea skimming missile detection. As a proof of concept, it is demonstrated that a simplified CS missile detection architecture and algorithm provides comparable results to the conventional imaging approach but using a smaller FPA. The primary message is that all of the excitement surrounding CS is necessary and appropriate for encouraging our creativity but we all must also take off our "rose colored glasses" and critically judge our ideas, methods and results relative to conventional imaging approaches.Comment: 10 page

Application of compressed sensing to the simulation of atomic systems

Compressed sensing is a method that allows a significant reduction in the number of samples required for accurate measurements in many applications in experimental sciences and engineering. In this work, we show that compressed sensing can also be used to speed up numerical simulations. We apply compressed sensing to extract information from the real-time simulation of atomic and molecular systems, including electronic and nuclear dynamics. We find that for the calculation of vibrational and optical spectra the total propagation time, and hence the computational cost, can be reduced by approximately a factor of five.Comment: 7 pages, 5 figure

An ontological approach for recovering legacy business content

Legacy Information Systems (LIS) pose a challenge for many organizations. On one hand, LIS are viewed as aging systems needing replacement; on the other hand, years of accumulated business knowledge have made these systems mission-critical. Current approaches however are often criticized for being overtly dependent on technology and ignoring the business knowledge which resides within LIS. In this light, this paper proposes a means of capturing the business knowledge in a technology agnostic manner and transforming it in a way that reaps the benefits of clear semantic expression - this transformation is achieved via the careful use of ontology. The approach called Content Sophistication (CS) aims to provide a model of the business that more closely adheres to the semantics and relationships of objects existing in the real world. The approach is illustrated via an example taken from a case study concerning the renovation of a large financial system and the outcome of the approach results in technology agnostic models that show improvements along several dimensions