Showing papers by "University of Graz published in 2010"

Total Generalized Variation

Abstract: The novel concept of total generalized variation of a function $u$ is introduced, and some of its essential properties are proved. Differently from the bounded variation seminorm, the new concept involves higher-order derivatives of $u$. Numerical examples illustrate the high quality of this functional as a regularization term for mathematical imaging problems. In particular this functional selectively regularizes on different regularity levels and, as a side effect, does not lead to a staircasing effect.

Precipitation downscaling under climate change: Recent developments to bridge the gap between dynamical models and the end user

Abstract: Precipitation downscaling improves the coarse resolution and poor representation of precipitation in global climate models and helps end users to assess the likely hydrological impacts of climate change. This paper integrates perspectives from meteorologists, climatologists, statisticians, and hydrologists to identify generic end user (in particular, impact modeler) needs and to discuss downscaling capabilities and gaps. End users need a reliable representation of precipitation intensities and temporal and spatial variability, as well as physical consistency, independent of region and season. In addition to presenting dynamical downscaling, we review perfect prognosis statistical downscaling, model output statistics, and weather generators, focusing on recent developments to improve the representation of space-time variability. Furthermore, evaluation techniques to assess downscaling skill are presented. Downscaling adds considerable value to projections from global climate models. Remaining gaps are uncertainties arising from sparse data; representation of extreme summer precipitation, subdaily precipitation, and full precipitation fields on fine scales; capturing changes in small-scale processes and their feedback on large scales; and errors inherited from the driving global climate model.

Is It Really Robust

Abstract: Empirical evidence to the robustness of the analysis of variance (ANOVA) concerning violation of the normality assumption is presented by means of Monte Carlo methods. High-quality samples underlying normally, rectangularly, and exponentially distributed basic populations are created by drawing samples which consist of random numbers from respective generators, checking their goodness of fit, and allowing only the best 10% to take part in the investigation. A one-way fixed-effect design with three groups of 25 values each is chosen. Effect-sizes are implemented in the samples and varied over a broad range. Comparing the outcomes of the ANOVA calculations for the different types of distributions, gives reason to regard the ANOVA as robust. Both, the empirical type I error α and the empirical type II error β remain constant under violation. Moreover, regression analysis identifies the factor “type of distribution” as not significant in explanation of the ANOVA results.

Current state of knowledge on aetiology, diagnosis, management, and therapy of peripartum cardiomyopathy: a position statement from the Heart Failure Association of the European Society of Cardiology Working Group on peripartum cardiomyopathy

Abstract: Peripartum cardiomyopathy (PPCM) is a cause of pregnancy-associated heart failure. It typically develops during the last month of, and up to 6 months after, pregnancy in women without known cardiovascular disease. The present position statement offers a state-of-the-art summary of what is known about risk factors for potential pathophysiological mechanisms, clinical presentation of, and diagnosis and management of PPCM. A high index of suspicion is required for the diagnosis, as shortness of breath and ankle swelling are common in the peripartum period. Peripartum cardiomyopathy is a distinct form of cardiomyopathy, associated with a high morbidity and mortality, but also with the possibility of full recovery. Oxidative stress and the generation of a cardiotoxic subfragment of prolactin may play key roles in the pathophysiology of PPCM. In this regard, pharmacological blockade of prolactin offers the possibility of a disease-specific therapy.

Nutrition and health in honey bees

Abstract: Adequate nutrition supports the development of healthy honey bee colonies. We give an overview of the nutritional demands of honey bee workers at three levels: (1) colony nutrition with the possibility of supplementation of carbohydrates and proteins; (2) adult nutrition and (3) larval nutrition. Larvae are especially dependant on protein and brood production is strongly affected by shortages of this nutrient. The number of larvae reared may be reduced to maintain the quality of remaining offspring. The quality of developing workers also suffers under conditions of larval starvation, leading to slightly affected workers. Larval starvation, alone or in combination with other stressors, can weaken colonies. The potential of different diets to meet nutritional requirements or to improve survival or brood production is outlined. We discuss nutrition-related risks to honey bee colonies such as starvation, monocultures, genetically modified crops and pesticides in pollen and nectar.

Students' expectations of, and experiences in e-learning: Their relation to learning achievements and course satisfaction

Abstract: Within only a few years, the use of e-learning has increased rapidly in Austria. In certain subjects, up to 60% of university students report using e-learning platforms at least 'sometimes' or 'frequently' (Unger & Wroblewski, 2006). Yet, which aspects of e-learning do students consider important for their learning achievements and course satisfaction? This question was addressed by surveying 2196 students from 29 universities in Austria about their expectations of, and experiences in e-learning. Multiple regression analyses using Mplus 4.21 were carried out to investigate how different facets of students' expectations and experiences are related to perceived learning achievements and course satisfaction. With regard to their expectations, i.e., aspects of a course they consider important, students' achievement goals were the best predictors for success and ranked higher than other course characteristics. With regard to their experiences, students' assessments of the instructor's expertise in e-learning, and her/his counseling and support were the best predictors for learning achievement and course satisfaction. Furthermore, self-regulated and collaborative learning were related to learning achievements. The results of the study suggest to influence students' motivation and goals by adapting instruction accordingly and emphasize the importance of continuing education and training for the instructors.

Microblogs in Higher Education - A chance to facilitate informal and process-oriented learning?

Abstract: Microblogging is one of the latest Web 2.0 technologies. The key elements are online communication using 140 characters and the fact that it involves ''following'' anyone. There has been a great deal of excitement about this in recent months. This paper reports on a research study that was carried out on the use of a microblogging platform for process-oriented learning in Higher Education. Students of the University of Applied Sciences of Upper Austria used the tool throughout their course. All postings were carefully tracked, examined and analyzed in order to explore the possibilities offered by microblogging in education. It can be concluded that microblogging should be seen as a completely new form of communication that can support informal learning beyond classrooms.

Caloric restriction and resveratrol promote longevity through the Sirtuin-1-dependent induction of autophagy

Abstract: Caloric restriction and autophagy-inducing pharmacological agents can prolong lifespan in model organisms including mice, flies, and nematodes. In this study, we show that transgenic expression of Sirtuin-1 induces autophagy in human cells in vitro and in Caenorhabditis elegans in vivo. The knockdown or knockout of Sirtuin-1 prevented the induction of autophagy by resveratrol and by nutrient deprivation in human cells as well as by dietary restriction in C. elegans. Conversely, Sirtuin-1 was not required for the induction of autophagy by rapamycin or p53 inhibition, neither in human cells nor in C. elegans. The knockdown or pharmacological inhibition of Sirtuin-1 enhanced the vulnerability of human cells to metabolic stress, unless they were stimulated to undergo autophagy by treatment with rapamycin or p53 inhibition. Along similar lines, resveratrol and dietary restriction only prolonged the lifespan of autophagy-proficient nematodes, whereas these beneficial effects on longevity were abolished by the knockdown of the essential autophagic modulator Beclin-1. We conclude that autophagy is universally required for the lifespan-prolonging effects of caloric restriction and pharmacological Sirtuin-1 activators.

Theory of Production: A Long-Period Analysis

Abstract: 1. Free competition and long-period positions 2. A one-commodity model 3. Two-commodity models 4. Models with any number of commodities 5. Choice of technique 6. Alternative descriptions of a 'technique' 7. Fixed capital models 8. Joint production 9. Models with jointly utilized machines 10. Land 11. Persistent wage and profit rate differentials 12. On limits to the long-period method 13. Production as a circular flow and the concept of surplus 14. The neoclassical theory of distribution and the problem of 'capital' 15. On some alternative theories of distribution Mathematical appendix.

Apoptosis in yeast: triggers, pathways, subroutines

Abstract: A cell's decision to die is controlled by a sophisticated network whose deregulation contributes to the pathogenesis of multiple diseases including neoplastic and neurodegenerative disorders. The finding, more than a decade ago, that baker's yeast (Saccharomyces cerevisiae) can undergo apoptosis uncovered the possibility to investigate this mode of programmed cell death (PCD) in a model organism that combines both technical advantages and a eukaryotic 'cell room.' Since then, numerous exogenous and endogenous triggers have been found to induce yeast apoptosis and multiple yeast orthologs of crucial metazoan apoptotic regulators have been identified and characterized at the molecular level. Such apoptosis-relevant orthologs include proteases such as the yeast caspase as well as several mitochondrial and nuclear proteins that contribute to the execution of apoptosis in a caspase-independent manner. Additionally, physiological scenarios such as aging and failed mating have been discovered to trigger apoptosis in yeast, providing a teleological interpretation of PCD affecting a unicellular organism. Due to its methodological and logistic simplicity, yeast constitutes an ideal model organism that is efficiently helping to decipher the cell death regulatory network of higher organisms, including the switches between apoptotic, autophagic, and necrotic pathways of cellular catabolism. Here, we provide an overview of the current knowledge about the apoptotic subroutine of yeast PCD and its regulation.

Gastric cancer: epidemiology and risk factors.

Abstract: The incidence of gastric cancer is decreasing and lies between 10 and 15 new cases per 100,000 population per year in most Western countries. Peak age is between 60 and 80 years. While distal gastric cancers account for the overall decrease in gastric cancer, tumors in the proximal stomach (cardia and esophagogastric junction) are on the rise. Recognized risk factors for gastric cancer are infection with Helicobacter pylori, dietary factors (e.g. high intake of salt-preserved foods), smoking, pernicious anemia and a history of partial gastrectomy.

The Optimal Aspect Ratio of Gold Nanorods for Plasmonic Bio-sensing

Abstract: The plasmon resonance of metal nanoparticles shifts upon refractive index changes of the surrounding medium through the binding of analytes. The use of this principle allows one to build ultra-small plasmon sensors that can detect analytes (e.g., biomolecules) in volumes down to attoliters. We use simulations based on the boundary element method to determine the sensitivity of gold nanorods of various aspect ratios for plasmonic sensors and find values between 3 and 4 to be optimal. Experiments on single particles confirm these theoretical results. We are able to explain the optimum by showing a corresponding maximum for the quality factor of the plasmon resonance.

European Respiratory Society guidelines for the diagnosis and management of lymphangioleiomyomatosis

Abstract: Lymphangioleiomyomatosis (LAM) is a rare lung disease, which occurs sporadically or in association with the genetic disease tuberous sclerosis complex (TSC) 1, 2. Sporadic LAM affects ∼1 in 400,000 adult females; in TSC, LAM occurs in 30–40% of adult females 3, 4 and exceptionally in males and children 5, 6. Patients with LAM usually develop progressive dyspnoea and recurrent pneumothorax, chylous collections and occasional haemoptysis 1. Extra pulmonary lymphadenopathy and cystic masses of the axial lymphatics termed lymphangioleiomyomas can result in abdominal and pelvic lymphatic obstruction 7. LAM is often associated with angiomyolipoma in the kidneys 8, and an increased frequency of meningioma 9. LAM varies in clinical features and rate of progression: this together with an absence of clear prognostic factors results in patients being given conflicting information about prognosis. Diagnosis is made by tissue biopsy (generally from the lung but occasionally from lymph nodes or lymphangioleiomyomas) and/or a combination of history and high-resolution computed tomography scanning (HRCT). Pathological diagnosis relies on characteristic LAM cell morphology and positive immunoreactivity to smooth muscle actin and HMB-45 antibodies. Increasingly HRCT is used to diagnose LAM without resorting to lung biopsy; however a number of conditions with multiple pulmonary cysts can mimic LAM. As LAM is rare, there have been no controlled trials of its management. Supportive treatment includes management of airflow obstruction and hypoxaemia with bronchodilators and oxygen respectively, specific treatment for surgical or pleural complications including pneumo- and chylothorax, and interventional treatment of renal lesions 10, 11. As LAM is a disease of females and is thought to be accelerated by oestrogen, oophorectomy, tamoxifen, progesterone and gonadotropin-releasing hormone (GnRH) analogues have been used without evidence that they are effective. The recent finding of abnormalities in the TSC1/2 genes resulting …

Can autophagy promote longevity

Abstract: Organismal lifespan can be extended by genetic manipulation of cellular processes such as histone acetylation, the insulin/IGF-1 (insulin-like growth factor 1) pathway or the p53 system. Longevity-promoting regimens, including caloric restriction and inhibition of TOR with rapamycin, resveratrol or the natural polyamine spermidine, have been associated with autophagy (a cytoprotective self-digestive process) and in some cases were reported to require autophagy for their effects. We summarize recent developments that outline these links and hypothesize that clearing cellular damage by autophagy is a common denominator of many lifespan-extending manipulations.

Multi-system neurological disease is common in patients with OPA1 mutations

Abstract: Additional neurological features have recently been described in seven families transmitting pathogenic mutations in OPA1, the most common cause of autosomal dominant optic atrophy. However, the frequency of these syndromal 'dominant optic atrophy plus' variants and the extent of neurological involvement have not been established. In this large multi-centre study of 104 patients from 45 independent families, including 60 new cases, we show that extra-ocular neurological complications are common in OPA1 disease, and affect up to 20% of all mutational carriers. Bilateral sensorineural deafness beginning in late childhood and early adulthood was a prominent manifestation, followed by a combination of ataxia, myopathy, peripheral neuropathy and progressive external ophthalmoplegia from the third decade of life onwards. We also identified novel clinical presentations with spastic paraparesis mimicking hereditary spastic paraplegia, and a multiple sclerosis-like illness. In contrast to initial reports, multi-system neurological disease was associated with all mutational subtypes, although there was an increased risk with missense mutations [odds ratio = 3.06, 95% confidence interval = 1.44-6.49; P = 0.0027], and mutations located within the guanosine triphosphate-ase region (odds ratio = 2.29, 95% confidence interval = 1.08-4.82; P = 0.0271). Histochemical and molecular characterization of skeletal muscle biopsies revealed the presence of cytochrome c oxidase-deficient fibres and multiple mitochondrial DNA deletions in the majority of patients harbouring OPA1 mutations, even in those with isolated optic nerve involvement. However, the cytochrome c oxidase-deficient load was over four times higher in the dominant optic atrophy + group compared to the pure optic neuropathy group, implicating a causal role for these secondary mitochondrial DNA defects in disease pathophysiology. Individuals with dominant optic atrophy plus phenotypes also had significantly worse visual outcomes, and careful surveillance is therefore mandatory to optimize the detection and management of neurological disability in a group of patients who already have significant visual impairment.

Online or Face-to-Face? Students' Experiences and Preferences in E-Learning.

Abstract: Which aspects of e-learning courses do students experience as being favorable for learning? When do students prefer online or face-to-face learning components? These questions were the subject of a research study in a sample of 2196 students from 29 Austrian universities. The students completed a questionnaire on their experiences attending an e-learning course, on their perceived achievements, and on their preferences for online or face-to-face learning components. Students appreciated online learning for its potential in providing a clear and coherent structure of the learning material, in supporting self-regulated learning, and in distributing information. They preferred face-to-face learning for communication purposes in which a shared understanding has to be derived or in which interpersonal relations are to be established. An especially important result concerns students' perceptions of their learning achievements: When conceptual knowledge in the subject matter or skills in the application of one's knowledge are to be acquired, students prefer face-to-face learning. However, when skills in self-regulated learning are to be acquired, students advocate online learning.

BCI Demographics: How Many (and What Kinds of) People Can Use an SSVEP BCI?

Abstract: Brain-computer interface (BCI) systems enable communication without movement. It is unclear why some BCI approaches or parameters are less effective with some users. This study elucidates BCI demographics by exploring correlations among BCI performance, personal preferences, and different subject factors such as age or gender. Results showed that most people, despite having no prior BCI experience, could use the Bremen SSVEP BCI system in a very noisy field setting. Performance tended to be better in both young and female subjects. Most subjects stated that they did not consider the flickering stimuli annoying and would use or recommend this BCI system. These and other demographic analyses may help identify the best BCI for each user.

Click chemistry under non-classical reaction conditions

Abstract: First described almost a decade ago, “click” reactions such as the Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) are widely used today in organic and medicinal chemistry, in the polymer and material science field, and in chemical biology. While most click reactions can be performed at room temperature there are instances where some form of process intensification is required. In this tutorial review, aimed at the synthetic chemistry community, examples of click chemistry carried out under non-classical reaction conditions, such as for example applying microwave heating or continuous flow processing will be highlighted.

Exhumation, crustal deformation, and thermal structure of the Nepal Himalaya derived from the inversion of thermochronological and thermobarometric data and modeling of the topography

Abstract: duplex initiated at 9.8 ± 1.7 Ma, leading to an increase of uplift rate at front of the High Himalaya from 0.9 ± 0.31 to 3.05 ± 0.9 mm yr −1 . We also run 3‐D models by coupling PECUBE with a landscape evolution model (CASCADE). This modeling shows that the effectoftheevolvingtopographycanexplainafractionofthescatterobservedinthedatabut not all of it, suggesting that lateral variations of the kinematics of crustal deformation and exhumationarelikely.Ithasbeenarguedthatthesteepphysiographictransitionatthefootof the Greater Himalayan Sequence indicates OOS thrusting, but our results demonstrate that the best fit duplex model derived from the thermochronological and thermobarometric data reproduces the present morphology of the Nepal Himalaya equally well.

Conjugative DNA metabolism in Gram-negative bacteria.

Abstract: Bacterial conjugation in Gram-negative bacteria is triggered by a signal that connects the relaxosome to the coupling protein (T4CP) and transferosome, a type IV secretion system. The relaxosome, a nucleoprotein complex formed at the origin of transfer (oriT), consists of a relaxase, directed to the nic site by auxiliary DNA-binding proteins. The nic site undergoes cleavage and religation during vegetative growth, but this is converted to a cleavage and unwinding reaction when a competent mating pair has formed. Here, we review the biochemistry of relaxosomes and ponder some of the remaining questions about the nature of the signal that begins the process.

Toward a hybrid brain-computer interface based on imagined movement and visual attention.

Abstract: Brain-computer interface (BCI) systems do not work for all users. This article introduces a novel combination of tasks that could inspire BCI systems that are more accurate than conventional BCIs, especially for users who cannot attain accuracy adequate for effective communication. Subjects performed tasks typically used in two BCI approaches, namely event-related desynchronization (ERD) and steady state visual evoked potential (SSVEP), both individually and in a 'hybrid' condition that combines both tasks. Electroencephalographic (EEG) data were recorded across three conditions. Subjects imagined moving the left or right hand (ERD), focused on one of the two oscillating visual stimuli (SSVEP), and then simultaneously performed both tasks. Accuracy and subjective measures were assessed. Offline analyses suggested that half of the subjects did not produce brain patterns that could be accurately discriminated in response to at least one of the two tasks. If these subjects produced comparable EEG patterns when trying to use a BCI, these subjects would not be able to communicate effectively because the BCI would make too many errors. Results also showed that switching to a different task used in BCIs could improve accuracy in some of these users. Switching to a hybrid approach eliminated this problem completely, and subjects generally did not consider the hybrid condition more difficult. Results validate this hybrid approach and suggest that subjects who cannot use a BCI should consider switching to a different BCI approach, especially a hybrid BCI. Subjects proficient with both approaches might combine them to increase information throughput by improving accuracy, reducing selection time, and/or increasing the number of possible commands.

Could Anyone Use a BCI

Abstract: Brain-computer interface (BCI) systems can provide communication and control for many users, but not all users. This problem exists across different BCI approaches; a “universal” BCI that works for everyone has never been developed. Instead, about 20% of subjects are not proficient with a typical BCI system. Some groups have called this phenomenon “BCI illiteracy”. Some possible solutions have been explored, such as improved signal processing, training, and new tasks or instructions. These approaches have not resulted in a BCI that works for all users, probably because a small minority of users cannot produce detectable patterns of brain activity necessary to a particular BCI approach. We also discuss an underappreciated solution: switching to a different BCI approach. While the term “BCI illiteracy” elicits interesting comparisons between BCIs and natural languages, many issues are unclear. For example, comparisons across different studies have been problematic since different groups use different performance thresholds, and do not account for key factors such as the number of trials or size of the BCI’s alphabet. We also discuss challenges inherent in establishing widely used terms, definitions, and measurement approaches to facilitate discussions and comparisons among different groups.

On the Use of Neurophysiological Tools in IS Research: Developing a Research Agenda for NeuroIS

Abstract: This article aims to discuss the use of common neurophysiological tools, such as psychophysiological tools (e.g., EKG, eye tracking) and neuroimaging tools (e.g., fMRI, EEG) in Information Systems (IS) research. There is much interest in the social sciences in capturing objective data directly from the human body, and this interest has also been gaining momentum in IS research (termed NeuroIS). This article first introduces several commonly-used neurophysiological tools, and it then discusses several application areas and research questions where IS researchers can benefit from neurophysiological data toward developing a research agenda for NeuroIS. The proposed research areas are presented within four fundamental levels of analysis - individuals, groups, organizations, and markets - that are typically used to examine the use of IT.The article concludes with a set of recommendations on how to use neurophysiological tools in IS research along with practical suggestions for establishing NeuroIS as a viable sub-field in the IS literature.

Variants at APOE Influence Risk of Deep and Lobar Intracerebral Hemorrhage

Abstract: Objective: Prior studies investigating the association between APOE alleles epsilon 2/epsilon 4 and risk of intracerebral hemorrhage (ICH) have been inconsistent and limited to small sample sizes, and did not account for confounding by population stratification or determine which genetic risk model was best applied. Methods: We performed a large-scale genetic association study of 2189 ICH cases and 4041 controls from 7 cohorts, which were analyzed using additive models for epsilon 2 and epsilon 4. Results were subsequently meta-analyzed using a random effects model. A proportion of the individuals (322 cases, 357 controls) had available genome-wide data to adjust for population stratification. Results: Alleles epsilon 2 and epsilon 4 were associated with lobar ICH at genome-wide significance levels (odds ratio [OR] = 1.82, 95% confidence interval [CI] = 1.50-2.23, p = 6.6 x 10(-10); and OR = 2.20, 95%CI = 1.85-2.63, p = 2.4 x 10(-11), respectively). Restriction of analysis to definite/probable cerebral amyloid angiopathy ICH uncovered a stronger effect. Allele epsilon 4 was also associated with increased risk for deep ICH (OR = 1.21, 95% CI = 1.08-1.36, p = 2.6 x 10(-4)). Risk prediction evaluation identified the additive model as best for describing the effect of APOE genotypes. Interpretation: APOE epsilon 2 and epsilon 4 are independent risk factors for lobar ICH, consistent with their known associations with amyloid biology. In addition, we present preliminary findings on a novel association between APOE epsilon 4 and deep ICH. Finally, we demonstrate that an additive model for these APOE variants is superior to other forms of genetic risk modeling previously applied. ANN NEUROL 2010;68:934-943

Continuous Flow Organic Synthesis under High‐Temperature/Pressure Conditions

Abstract: Microreactor technology and continuous flow processing in general are key features in making organic synthesis both more economical and environmentally friendly. When preformed under a high-temperature/pressure process intensification regime many transformations originally not considered suitable for flow synthesis owing to long reaction times can be converted into high-speed flow chemistry protocols that can operate at production-scale quantities. This Focus Review summarizes the state of the art in high-temperature/pressure microreactor technology and provides a survey of successful applications of this technique from the recent synthetic organic chemistry literature.