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Search Results: 1 - 10 of 11124 matches for " Andreas Gruber "
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Hypothermia in the operating theatre
Andreas Gruber, Wilhelm Behringer, Engelbert Knosp
Critical Care , 2012, DOI: 10.1186/cc11275
Abstract: Cerebral ischaemia results from a reduction or complete loss of cerebral blood flow (CBF) and lack of cerebral oxygenation, followed by depletion of ATP, dysfunction of ATP-dependent membrane pumps and subsequently occurrence of anoxic depolarisation. A large amount of glutamate is released from the intracellular space into the extracellular space, causing excitotoxic injury by stimulating N-methyl-D-aspartate (NMDA) receptors and triggering calcium influx. Increased intracellular calcium levels per se amplify injury by increasing calcium permeability and glutamate release via second messenger mechanisms. These acute cascades lead to necrotic neuronal death by interfering with the mitochondrial respiratory chain. Ischaemia and reperfusion further enhance excitotoxicity by providing oxygen as a substrate for several enzymatic oxidation reactions, thereby generating products of reactive oxygen species in large quantities. These free radicals enhance protein oxidation and lipid membrane disintegration and in conjunction with blood-brain barrier (BBB) disruption further contribute to ischaemic necrosis. Apoptosis also occurs in cerebral ischemia, with antiapoptotic proteins being selectively upregulated in surviving neurons and proapoptotic proteins being highly expressed in dying cells.The first controlled attempts to cool the human brain were undertaken by the neurosurgeon Temple Fay in 1938 [1]. Irrigating the brain directly with ice water and sometimes achieving solid parenchymal freezing, he claimed 'extremely gratifying results' in a paper on 'local and generalized refrigeration of the human brain'. Over time, many mechanisms have been proposed regarding the neuroprotective effect of hypothermia. First, hypothermia results in a temperature-dependent decrease of oxygen and glucose metabolism; that is, a 10°C decrease in temperature reduces ATP consumption and the cerebral metabolic rate (CMR) of oxygen, glucose, and lactate twofold to fourfold [2]. Second, intra-is
Repetitive Hops Induce Postactivation Potentiation in Triceps Surae as well as an Increase in the Jump Height of Subsequent Maximal Drop Jumps
Julian Bergmann, Andreas Kramer, Markus Gruber
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0077705
Abstract: Postactivation potentiation (PAP) has been defined as the increase in twitch torque after a conditioning contraction. The present study aimed to investigate the effectiveness of hops as conditioning contractions to induce PAP and increase performance in subsequent maximal drop jumps. In addition, we wanted to test if and how PAP can contribute to increases in drop jump rebound height. Twelve participants performed 10 maximal two-legged hops as conditioning contractions. Twitch peak torques of triceps surae muscles were recorded before and after the conditioning hops. Then, subjects performed drop jumps with and without 10 conditioning hops before each drop jump. Recordings included ground reaction forces, ankle and knee angles and electromyographic activity in five leg muscles. In addition, efferent motoneuronal output during ground contact was estimated with V-wave stimulation. The analyses showed that after the conditioning hops, twitch peak torques of triceps surae muscles were 32% higher compared to baseline values (P < 0.01). Drop jumps performed after conditioning hops were significantly higher (12%, P < 0.05), but V-waves and EMG activity remained unchanged. The amount of PAP and the change in drop jump rebound height were positively correlated (r2 = 0.26, P < 0.05). These results provide evidence for PAP in triceps surae muscles induced by a bout of hops and indicate that PAP can contribute to the observed performance enhancements in subsequent drop jumps. The lack of change in EMG activity and V-wave amplitude suggests that the underlying mechanisms are more likely intramuscular than neural in origin.
Comparing the vacuum structure of quenched and dynamical configurations
Falk Bruckmann,Florian Gruber,Andreas Sch?fer
Physics , 2009,
Abstract: We systematically compare filtering methods used to extract topological structures on SU(3) lattice configurations. We show that there is a strong correlation of the topological charge densities obtained by APE and Stout smearing. To get rid of artifacts of these methods, we analyze structures that are also seen by Laplace filtering. This combined analysis shows that the topological charge density is more fragmented in the presence of dynamical quarks.
Filtered topological structure of the QCD vacuum: Effects of dynamical quarks
Falk Bruckmann,Florian Gruber,Andreas Sch?fer
Physics , 2009, DOI: 10.1016/j.physletb.2010.02.077
Abstract: We systematically compare filtering methods used to extract topological structures on SU(3) lattice configurations. We show that there is a strong correlation of the topological charge densities obtained by APE and Stout smearing. To get rid of artifacts of these methods, we analyse structures that are also seen by Laplace filtering and indeed identify artifacts for strong smearing. The topological charge density in this combined analysis is more fragmented in the presence of dynamical quarks. A power law exponent that characterises the distribution of filtered topological clusters turns out to be not far off the values of an instanton gas model.
The Human Brain Maintains Contradictory and Redundant Auditory Sensory Predictions
Marika Pieszek, Andreas Widmann, Thomas Gruber, Erich Schr?ger
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0053634
Abstract: Computational and experimental research has revealed that auditory sensory predictions are derived from regularities of the current environment by using internal generative models. However, so far, what has not been addressed is how the auditory system handles situations giving rise to redundant or even contradictory predictions derived from different sources of information. To this end, we measured error signals in the event-related brain potentials (ERPs) in response to violations of auditory predictions. Sounds could be predicted on the basis of overall probability, i.e., one sound was presented frequently and another sound rarely. Furthermore, each sound was predicted by an informative visual cue. Participants’ task was to use the cue and to discriminate the two sounds as fast as possible. Violations of the probability based prediction (i.e., a rare sound) as well as violations of the visual-auditory prediction (i.e., an incongruent sound) elicited error signals in the ERPs (Mismatch Negativity [MMN] and Incongruency Response [IR]). Particular error signals were observed even in case the overall probability and the visual symbol predicted different sounds. That is, the auditory system concurrently maintains and tests contradictory predictions. Moreover, if the same sound was predicted, we observed an additive error signal (scalp potential and primary current density) equaling the sum of the specific error signals. Thus, the auditory system maintains and tolerates functionally independently represented redundant and contradictory predictions. We argue that the auditory system exploits all currently active regularities in order to optimally prepare for future events.
Analysis of damping-induced phase flips of plasmonic nanowire modes
Andreas Hohenau,Primoz Kusar,Christian Gruber,Joachim R. Krenn
Physics , 2012, DOI: 10.1364/OL.37.000746
Abstract: We launch surface plasmons from one end of a silver nanowire by asymmetric illumination with white light and use plasmon-to-light scattering at the nanowire ends to probe spectroscopically the plasmonic Fabry-Perot wire modes. The spectral positions of the maxima and minima in the scattered intensity from both nanowire ends are found to be either in phase or out-of phase, depending on the nanowire length and the spectral range. This behavior can be explained by a generalized Fabry-Perot model. The turnover-point between the two regimes is sensitive to the surface plasmon round trip losses and thus opens a new possibility for detecting changes of the optical absorption in the nanowire environment.
The Influence of Implicit Achievement Motive and Graphological Variables on Learning Variables  [PDF]
Nicole Gruber, Ludwig Kreuzpointner
Psychology (PSYCH) , 2015, DOI: 10.4236/psych.2015.612145
Abstract: There are several methods of implicit measurement. A very valid and wide spread assessment of motives by using the technique of projection is picture story exercises (PSE). Graphology, as theory of inferences on personality and motives by analyzing handwriting, is another one. The presented study examines the commons of the both measurement methods and their prediction of achievement behaviour. So, the achievement motive of 189 students was assessed using the PSE of Heckhausen (1963) and afterwards their handwriting was scored by a categorical system of Ploog (2013). Achievement related behaviour was operatively analyzed with self-reported learning time, learning behaviour and task-choice performance. It is shown that implicit motives measured by PSE are related with the criteria of task-choice performance. It is shown that both implicit motives measured by PSE and graphological variables deliver information about learning variables.
RNAalifold: improved consensus structure prediction for RNA alignments
Stephan H Bernhart, Ivo L Hofacker, Sebastian Will, Andreas R Gruber, Peter F Stadler
BMC Bioinformatics , 2008, DOI: 10.1186/1471-2105-9-474
Abstract: We show that the accuracy of RNAalifold predictions can be improved substantially by introducing a different, more rational handling of alignment gaps, and by replacing the rather simplistic model of covariance scoring with more sophisticated RIBOSUM-like scoring matrices. These improvements are achieved without compromising the computational efficiency of the algorithm. We show here that the new version of RNAalifold not only outperforms the old one, but also several other tools recently developed, on different datasets.The new version of RNAalifold not only can replace the old one for almost any application but it is also competitive with other approaches including those based on SCFGs, maximum expected accuracy, or hierarchical nearest neighbor classifiers.Unbiased surveys of the transcriptomes of higher eukaryotes by multiple techniques ranging from tiling arrays and short-read sequencing to large-scale sequencing of full-length cDNAs have dramatically changed our perception of genome organization: At least 90% of the mammalian genomes are transcribed, the vast majority of this transcription is non-protein-coding, and there is mounting evidence that a significant fraction of the non-coding transcripts are functional [1,2]. The investigation of non-coding RNAs has thus developed into a focal topic in molecular biology and bioinformatics alike. Most of the ancient house-keeping RNAs (tRNAs, rRNAs, snRNAs, snoRNAs) and many of the newly discovered regulatory RNAs, including microRNA precursors, form evolutionarily well-conserved secondary structures, reviewed e.g. in [3]. These structures are tightly linked to the molecules' functions. It is therefore a core task in RNA bioinformatics to compute in particular the consensus structures of evolutionarily conserved RNAs.It has long been known that the accuracy of thermodynamic structure predictions for individual sequences is rather limited. On the other hand, computing the consensus structure common to several related
Strategies for measuring evolutionary conservation of RNA secondary structures
Andreas R Gruber, Stephan H Bernhart, Ivo L Hofacker, Stefan Washietl
BMC Bioinformatics , 2008, DOI: 10.1186/1471-2105-9-122
Abstract: We systematically assessed the ability of various measures to detect conserved RNA structures in multiple sequence alignments. We tested three existing and eight novel strategies that are based on metrics of folding energies, metrics of single optimal structure predictions, and metrics of structure ensembles. We find that the folding energy based SCI score used in the RNAz program and a simple base-pair distance metric are by far the most accurate. The use of more complex metrics like for example tree editing does not improve performance. A variant of the SCI performed particularly well on highly conserved alignments and is thus a viable alternative when only little evolutionary information is available. Surprisingly, ensemble based methods that, in principle, could benefit from the additional information contained in sub-optimal structures, perform particularly poorly. As a general trend, we observed that methods that include a consensus structure prediction outperformed equivalent methods that only consider pairwise comparisons.Structural conservation can be measured accurately with relatively simple and intuitive metrics. They have the potential to form the basis of future RNA gene finders, that face new challenges like finding lineage specific structures or detecting mis-aligned sequences.RNA secondary structures serve important functions in many non-coding RNAs and cis-acting regulatory elements of mRNAs [1,2]. They mediate RNA-protein/RNA-RNA interactions in many different biological pathways and some even show enzymatic activity themselves. Functional constraints lead to evolutionary conservation of the RNA structure that in many cases can exceed the level of sequence conservation. Therefore, conserved structures are characteristic evolutionarily signatures of functional RNAs. Most programs developed for the detection of novel functional RNAs rely on these signatures.QRNA [3] was the first program that detects conserved RNAs. It models RNA structure in a pair
Dose-response relationship for breast cancer induction at radiotherapy dose
Uwe Schneider, Marcin Sumila, Judith Robotka, Günther Gruber, Andreas Mack, Jürgen Besserer
Radiation Oncology , 2011, DOI: 10.1186/1748-717x-6-67
Abstract: In this work a dose-response relationship for breast cancer is derived based on(i) the analysis of breast cancer induction after Hodgkin's disease,(ii) a cancer risk model developed for high doses including fractionation based on the linear quadratic model, and(iii) the reconstruction of treatment plans for Hodgkin's patients treated with radiotherapy,(iv) the breast cancer induction of the A-bomb survivor data.The fitted model parameters for an α/β = 3 Gy were α = 0.067Gy-1 and R = 0.62. The risk for breast cancer is according to this model for small doses consistent with the finding of the A-bomb survivors, has a maximum at doses of around 20 Gy and drops off only slightly at larger doses. The predicted EAR for breast cancer after radiotherapy of Hodgkin's disease is 11.7/10000PY which can be compared to the findings of several epidemiological studies where EAR for breast cancer varies between 10.5 and 29.4/10000PY. The model was used to predict the impact of the reduction of radiation volume on breast cancer risk. It was estimated that mantle field irradiation is associated with a 3.2-fold increased risk compared with mediastinal irradiation alone, which is in agreement with a published value of 2.7. It was also shown that the modelled age dependency of breast cancer risk is in satisfying agreement with published data.The dose-response relationship obtained in this report can be used for the prediction of radiation induced secondary breast cancer of radiotherapy patients.Cancer induction after radiation therapy is known as a severe side effect. It is therefore of interest to predict the probability of second cancer appearance for the patient to be treated. For this purpose it is not sufficient to apply the results from epidemiological studies on cancer induction from more than 20 years ago to the patient treated today, since radiation therapy changed significantly in the last decades, for instance radiation type, treatment technique, application of treatment, tre
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