Showing papers by "University of Graz published in 2007"

Simulation of networks of spiking neurons: A review of tools and strategies

Abstract: We review different aspects of the simulation of spiking neural networks. We start by reviewing the different types of simulation strategies and algorithms that are currently implemented. We next review the precision of those simulation strategies, in particular in cases where plasticity depends on the exact timing of the spikes. We overview different simulators and simulation environments presently available (restricted to those freely available, open source and documented). For each simulation tool, its advantages and pitfalls are reviewed, with an aim to allow the reader to identify which simulator is appropriate for a given task. Finally, we provide a series of benchmark simulations of different types of networks of spiking neurons, including Hodgkin-Huxley type, integrate-and-fire models, interacting with current-based or conductance-based synapses, using clock-driven or event-driven integration strategies. The same set of models are implemented on the different simulators, and the codes are made available. The ultimate goal of this review is to provide a resource to facilitate identifying the appropriate integration strategy and simulation tool to use for a given modeling problem related to spiking neural networks.

Successful implementation of user-centered game based learning in higher education: An example from civil engineering

Abstract: Goal: The use of an online game for learning in higher education aims to make complex theoretical knowledge more approachable. Permanent repetition will lead to a more in-depth learning. Objective: To gain insight into whether and to what extent, online games have the potential to contribute to student learning in higher education. Experimental setting: The online game was used for the first time during a lecture on Structural Concrete at Master's level, involving 121 seventh semester students. Methods: Pre-test/post-test experimental control group design with questionnaires and an independent online evaluation. Results: The minimum learning result of playing the game was equal to that achieved with traditional methods. A factor called ''joy'' was introduced, according to [Nielsen, J. (2002): User empowerment and the fun factor. In Jakob Nielsen's Alertbox, July 7, 2002. Available from http://www.useit.com/alertbox/20020707.html.], which was amazingly high. Conclusion: The experimental findings support the efficacy of game playing. Students enjoyed this kind of e-learning.

Phase structure of the Polyakov-quark-meson model

Abstract: The relation between the deconfinement and chiral phase transition is explored in the framework of a Polyakov-loop-extended two-flavor quark-meson (PQM) model. In this model the Polyakov loop dynamics is represented by a background temporal gauge field which also couples to the quarks. As a novelty an explicit quark chemical potential and ${N}_{f}$-dependence in the Polyakov loop potential is proposed by using renormalization group arguments. The behavior of the Polyakov loop as well as the chiral condensate as function of temperature and quark chemical potential is obtained by minimizing the grand canonical thermodynamic potential of the system. The effect of the Polyakov loop dynamics on the chiral phase diagram and on several thermodynamic bulk quantities is presented.

Volatiles of bacterial antagonists inhibit mycelial growth of the plant pathogen Rhizoctonia solani

Abstract: Bacterial antagonists are bacteria that negatively affect the growth of other organisms. Many antagonists inhibit the growth of fungi by various mechanisms, e.g., secretion of lytic enzymes, siderophores and antibiotics. Such inhibition of fungal growth may indirectly support plant growth. Here, we demonstrate that small organic volatile compounds (VOCs) emitted from bacterial antagonists negatively influence the mycelial growth of the soil-borne phytopathogenic fungus Rhizoctonia solani Kuhn. Strong inhibitions (99-80%) under the test conditions were observed with Stenotrophomonas maltophilia R3089, Serratia plymuthica HRO-C48, Stenotrophomonas rhizophila P69, Serratia odorifera 4Rx13, Pseudomonas trivialis 3Re2-7, S. plymuthica 3Re4-18 and Bacillus subtilis B2g. Pseudomonas fluorescens L13-6-12 and Burkholderia cepacia 1S18 achieved 30% growth reduction. The VOC profiles of these antagonists, obtained through headspace collection and analysis on GC-MS, show different compositions and complexities ranging from 1 to almost 30 compounds. Most volatiles are species-specific, but overlapping volatile patterns were found for Serratia spp. and Pseudomonas spp. Many of the bacterial VOCs could not be identified for lack of match with mass-spectra of volatiles in the databases.

Roche lobe effects on the atmospheric loss from "Hot Jupiters"

Abstract: Context. A study of the mass loss enhancement for very close “Hot Jupiters” due to the gravitational field of the host star is presented. Aims. The influence of the proximity to a planet of the Roche lobe boundary on the critical temperature for blow-off conditions for estimating the increase of the mass loss rate through hydrodynamic blow-off for close-in exoplanets is investigated. Methods. We consider the gravitational potential for a star and a planet along the line that joins their mass centers and the energy balance equation for an evaporating planetary atmosphere including the effect of the stellar tidal force on atmospheric escape. Results. By studying the effect of the Roche lobe on the atmospheric loss from short-periodic gas giants we derived reasonably accurate approximate formulas to estimate atmospheric loss enhancement due to the action of tidal forces on a “Hot Jupiter” and to calculate the critical temperature for the onset of “geometrical blow-off”, which are valid for any physical values of the Roche lobe radial distance. Using these formulas, we found that the stellar tidal forces can enhance the hydrodynamic evaporation rate from TreS-1 and OGLE-TR-56b by about 2 fold, while for HD 209458b we found an enhancement of about 50%. For similar exoplanets which are closer to their host star than OGLE-TR-56b, the mass loss enhancement can be even larger. Moreover, we showed that the effect of the Roche lobe allows “Hot Jupiters” to reach blow-off conditions at temperatures which are less than expected due to the stellar X-ray and EUV heating.

Long acting insulin analogues versus NPH insulin (human isophane insulin) for type 2 diabetes mellitus

Abstract: Background Despite indications from epidemiological trials that higher blood glucose concentrations are associated with a higher risk for developing micro- and macrovascular complications, evidence for a beneficial effect of antihyperglycaemic therapy in patients with type 2 diabetes mellitus is conflicting. Two large studies, the United Kingdom Prospective Diabetes Study (UKPDS) and the University Group Diabetes Program (UGDP), did not find a reduction of cardiovascular endpoints through improvement of metabolic control. The theoretical benefits of newer insulin analogues might result in fewer macrovascular and microvascular events. Objectives To assess the effects of long-term treatment with long-acting insulin analogues (insulin glargine and insulin detemir) compared to NPH insulin in patients with type 2 diabetes mellitus. Search methods Studies were obtained from computerised searches of MEDLINE, EMBASE, The Cochrane Library and communication with experts in the field as well as insulin producing companies. Selection criteria Studies were included if they were randomised controlled trials in adults with diabetes mellitus type 2 and had a trial duration of at least 24 weeks. Data collection and analysis Two authors independently assessed trial quality and extracted data. Pooling of studies by means of random-effects meta-analyses was performed. Main results Six studies comparing insulin glargine to NPH (Neutral Protamine Hagedorn) insulin and two studies comparing insulin detemir to NPH insulin were identified. In these trials, 1715 patients were randomised to insulin glargine and 578 patients to insulin detemir. Duration of the included trials ranged from 24 to 52 weeks. Metabolic control, measured by glycosylated haemoglobin A1c (HbA1c) as a surrogate endpoint, and adverse effects did not differ in a clinical relevant way between treatment groups. While no statistically significant difference for severe hypoglycaemia rates was shown in any of the trials, the rate of symptomatic, overall and nocturnal hypoglycaemia was statistically significantly lower in patients treated with either insulin glargine or detemir. No evidence for a beneficial effect of long-acting analogues on patient-oriented outcomes like mortality, morbidity, quality of life or costs could be obtained. Authors' conclusions Our analysis suggests, if at all only a minor clinical benefit of treatment with long-acting insulin analogues for patients with diabetes mellitus type 2 treated with "basal" insulin regarding symptomatic nocturnal hypoglycaemic events. Until long-term efficacy and safety data are available, we suggest a cautious approach to therapy with insulin glargine or detemir.

Ambient intelligence in assisted living: enable elderly people to handle future interfaces

Abstract: Ambient Assisted Living is currently one of the important research and development areas, where accessibility, usability and learning plays a major role and where future interfaces are an important concern for applied engineering. The general goal of ambient assisted living solutions is to apply ambient intelligence technology to enable people with specific demands, e.g. handicapped or elderly, to live in their preferred environment longer. Due to the high potential of emergencies, a sound emergency assistance is required, for instance assisting elderly people with comprehensive ambient assisted living solutions sets high demands on the overall system quality and consequently on software and system engineering - user acceptance and support by various userinterfaces is an absolute necessity. In this article, we present an Assisted Living Laboratory that is used to train elderly people to handle modern interfaces for Assisted Living and evaluate the usability and suitability of these interfaces in specific situations, e.g., emergency cases.

Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. II. CME-induced ion pick up of Earth-like exoplanets in close-in habitable zones.

Abstract: Atmospheric erosion of CO2 -rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M s...

Miocene Central Paratethys stratigraphy - current status and future directions

Abstract: The complex geodynamic history of the Paratethys periodically fostered the evolution of a highly endemic biota with only limited exchange between the neighboring Mediterranean and Indo-Pacific provinces. The resulting very peculiar fossil assemblages forced the introduction of a regional chronostratigraphic subdivision for the Western/Central and Eastern Paratethys respectively. For the Central Paratethys we present a summarized and updated database for the individual stages, and we review the current status for correla- tion with the Mediterranean stratigraphic framework. The Miocene Central Paratethys stages were defined on exclusively paleontological criteria in type sections (holostratotypes and faciostratotypes). They are all bounded by either sedimentary hiatuses or distinct facies changes, inferred to mark lowstands in sea level, and not a single boundary stratotype has been defined. Some correlating tie-points to the Mediterranean succession are based on calcareous nannoplankton and planktonic foraminifers; magnetostratigraphic correlation is very limited. All stages can be assigned to the putatively third-order sea level cycles, with the Eggenburgian, Badenian and Pannonian Stages each spanning three cycles and the Ottnangian, Karpatian, and Sarmatian one each. The Karpatian/Badenian boundary correlates with the Burdigalian/Langhian (Early/Middle Miocene) boundary, and the Sarmatian/Pannonian boundary correlates with the Serravallian/Tortonian (Middle/Late Miocene) boundary. The correlation to third-order cycles and the detection of astronomical signals suggest that not only a regional but also a strong global signal is present in the rock record of the Central Paratethys. Since the current defi- nition of a stage includes its global spread, formally defined regional stages are redundant and therefore also not necessary for the Central Paratethys. However, if stages are essentially regional, then a regional scale as for Central Paratethys would be much more appropriate.

Biogeographic responses to geodynamics: A key study all around the Oligo–Miocene Tethyan Seaway ☆

Abstract: Extensive terrestrial exchanges were initiated by the closure of the Tethyan Seaway during the Early Miocene. Proboscideans are among the most prominent African immigrants, which arrived in Eurasia about 19 Ma ago via the ‘‘Gomphotherium Landbridge’’. Several distinct waves of continental migrations, however, document that the formation of this landbridge was a multiphase process. Until the closure, a marine faunal exchange was enabled via the Mesopotamian Trough and the Zagros Basin, as reflected by contributions of Indonesian corals in the Iranian basins and by the occurrence of ‘‘western’’ gastropods in Pakistan and India. Nevertheless, the emergence of the landbridge was preceded in the marine biosphere by first biogeographic divergences on both sides of the seaway already during Oligocene times (e.g. within the tridacnines and strombids). Around the closure event, the breakdown of biogeographic relations was near-complete and the Proto-Mediterranean faunas bear little in common with those of the Indo-West Pacific Region (IWPR). Some of the discussed examples suggest that the Western Tethys Region (WTR) had acted as centre of origin and diversity during Oligocene and Early Miocene times. After the closure of the seaway, this centre had shifted to the southeast, heralding the enormous biodiversity of the modern IWPR. Some originally WTR elements managed to follow this shift and formed the Miocene stock for the modern IWPR faunas. In contrast, the marine fauna in the Mediterranean cul-de-sac suffered strong impoverishment due to the Miocene cooling, the Messinian Salinity Crisis and the late Pliocene and Pleistocene glacials – a fact which might explain the receptivity of the Mediterranean Sea for Lessepsian migrants. This synthesis tries to document the practical problem of recognising biogeographic patterns despite the heterochronous developments in different systematic groups, which, in addition, are often obscured by a stratigraphically incomplete and geographically patchy fossil record. r 2007 Elsevier GmbH. All rights reserved.

A new xenobiotic-induced mouse model of sclerosing cholangitis and biliary fibrosis.

Abstract: Xenobiotics and drugs may lead to cholangiopathies and biliary fibrosis, but the underlying mechanisms are largely unknown. Therefore, we aimed to characterize the cause and consequences of hepatobiliary injury and biliary fibrosis in 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-fed mice as a novel model of xenobiotic-induced cholangiopathy. Liver morphology, markers of inflammation, cell proliferation, fibrosis, bile formation, biliary porphyrin secretion, and hepatobiliary transporter expression were studied longitudinally in DDC- and control diet-fed Swiss albino mice. DDC feeding led to increased biliary porphyrin secretion and induction of vascular cell adhesion molecule, osteopontin, and tumor necrosis factor-α expression in bile duct epithelial cells. This was associated with a pronounced pericholangitis with a significantly increased number of CD11b-positive cells, ductular reaction, and activation of periductal myofibroblasts, leading to large duct disease and a biliary type of liver fibrosis. After 4 weeks, we constantly observed intraductal porphyrin pigment plugs. Glutathione and phospholipid excretion significantly decreased over time. Expression of Ntcp, Oatp4, and Mrp2 was significantly reduced, whereas Bsep expression remained unchanged and adaptive Mrp3 and Mrp4 expression was significantly induced. We demonstrate that DDC feeding in mice leads to i) a reactive phenotype of cholangiocytes and bile duct injury, ii) pericholangitis, periductal fibrosis, ductular reaction, and consequently portal-portal bridging, iii) down-regulation of Mrp2 and impaired glutathione excretion, and iv) segmental bile duct obstruction. This model may be valuable to investigate the mechanisms of xenobiotic-induced chronic cholangiopathies and its sequels including biliary fibrosis.

Actinic keratosis is an early in situ squamous cell carcinoma: a proposal for reclassification.

Abstract: The term actinic keratosis (AK) describes a sun-induced, clinical erythematous lesion covered with scale, but does not provide an understanding of the biology or histopathology of the lesion. Consequently, several classification systems for AK have been suggested, but as yet no consensus has been reached. These systems strive to correlate the pathological and clinical features to better provide physicians with the most accurate information to enable correct decisions to be made regarding treatments, Prognosis and metastatic potential. AK is a clinical description that has a histological diagnosis consistent with squamous cell carcinoma (SCC) in situ. We recommend an AK classification system that describes these lesions as squamous cell carcinomas (SCCs), using the terminology 'early in situ SCC Type AK I', 'early in situ SCC type AK II' and 'in situ SCC Type AK III', there by giving clinicians better guidance for diagnosis and specific treatment recommendations.

Accuracy of anthropometric indicators of obesity to predict cardiovascular risk.

Abstract: Context: Obesity is associated with various cardiovascular risk factors. The body mass index (BMI) is the standard measure of overweight and obesity. However, more recently, waist to hip ratio (WHR) or waist circumference (WC) as more sensitive measures for visceral obesity have been proposed to be more indicative of cardiovascular risk. Objective: This study was performed to test the predictive value of anthropometric parameters for the presence of several cardiovascular risk conditions. Design: The DETECT (Diabetes Cardiovascular Risk-Evaluation: Targets and Essential Data for Commitment of Treatment) study is a cross-sectional, clinical-epidemiological study. Participants: We studied 5377 unselected subjects (2016 men, 3361 women) without arteriosclerotic disease, aged 20–79 yr, from the DETECT laboratory sample. Setting: This study was conducted by primary care physicians. Intervention: We measured anthropometric parameters and assessed cardiovascular risk by clinical examination, patient history, and...

Epidemiology and aetiology of basal cell carcinoma.

Abstract: Basal cell carcinoma (BCC) is a malignant epithelial neoplasm of the skin preferentially affecting male caucasians and is rarely observed in patients with more intense skin pigmentation. A characteristic feature of BCCs are their extremely low risk to metastasize. Epidemiological data indicate that the overall incidence is increasing worldwide significantly by about 3-10% per annum.(1-3) Based on the increasing incidence of this usually not life-threatening tumour BCC appears to develop into a growing public health problem. This review elucidates the risk factors for the development and for the progression of BCC leading to an improved understanding of this tumour.

Exact and approximative imaging methods for photoacoustic tomography using an arbitrary detection surface.

Abstract: Two universal reconstruction methods for photoacoustic (also called optoacoustic or thermoacoustic) computed tomography are derived, applicable to an arbitrarily shaped detection surface. In photoacoustic tomography acoustic pressure waves are induced by illuminating a semitransparent sample with pulsed electromagnetic radiation and are measured on a detection surface outside the sample. The imaging problem consists in reconstructing the initial pressure sources from those measurements. The first solution to this problem is based on the time reversal of the acoustic pressure field with a second order embedded boundary method. The pressure on the arbitrarily shaped detection surface is set to coincide with the measured data in reversed temporal order. In the second approach the reconstruction problem is solved by calculating the far-field approximation, a concept well known in physics, where the generated acoustic wave is approximated by an outgoing spherical wave with the reconstruction point as center. Numerical simulations are used to compare the proposed universal reconstruction methods with existing algorithms.

Towards peakless, reproducible and long-acting insulins. An assessment of the basal analogues based on isoglycaemic clamp studies.

Abstract: While the advantages of the two basal insulin analogues, glargine and detemir, over neutral protamine Hagedorn are well established, the relative merit of the two compared with each other has been a matter of some controversy. The two analogues are popularly perceived to differ from each other in their pharmacodynamic (PD) profiles, in particular with regard to 'flatness' and duration of action. The aim of this review, therefore, is to give a complete overview on the available PD data of both analogues as derived with the glucose clamp technique. In order to improve parity across studies, a common definition for duration of action (time from injection to plasma glucose >8.3 mmol/l) was applied and study data were recalculated when necessary. Despite differences in methodological details, the results of most clamp studies were very consistent. Glargine and detemir both typically show a gentle rise and fall in glucose-lowering action over time. Duration of action with both analogues is dose dependent, but in the clinically relevant range of 0.35-0.8 U/kg it is close to 24 h in people with type 1 diabetes and in excess of this in people with type 2 diabetes. While both analogues seem to be very similar with regard to the mean shape of their PD profile and duration of action, detemir shows less within-subject variability in its metabolic effect. These findings in experimental glucose clamp studies are consistent with observations in clinical trials and support routine once daily use with either analogue, in particular in people with type 2 diabetes.

Microwave‐Assisted Synthesis under Continuous‐Flow Conditions

Abstract: Microwave-assisted chemistry is about to change the art and practice of synthesis performed in many academic and industrial laboratories. One of the major drawbacks of this enabling technology is the difficulty associated with scale-up. Because of the limited penetration depth of microwaves into absorbing media, the solution to scale-up lies in continuous-flow processing. In this review we summarize the current state of the art in this field and present an overview on published examples of microwave-assisted synthesis using continuous-flow and stop-flow processing in custom-built or commercially available microwave reactors.