Stability Estimates and Structural Spectral Properties of Saddle Point Problems

For a general class of saddle point problems sharp estimates for Babu\v{s}ka's inf-sup stability constants are derived in terms of the constants in Brezzi's theory. In the finite-dimensional Hermitian case more detailed spectral properties of preconditioned saddle point matrices are presented, which are helpful for the convergence analysis of common Krylov subspace methods. The theoretical results are applied to two model problems from optimal control with time-periodic state equations. Numerical experiments with the preconditioned minimal residual method are reported

Losing the error related negativity (ERN): an indicator for willed action

When people make errors in a discrimination task, a negative-going waveform can be observed in scalp-recorded EEG that has been coined the error-related negativity (ERN). We hypothesized that the ERN only occurs with slips, that is unwilled action errors, but not if an error is committed willingly and intentionally. We investigated the occurrence of the ERN in a choice reaction time task that has been shown to produce an ERN and in an error simulation task where subjects had to fake errors while the EEG was recorded. We observed a loss of the ERN when errors were committed in willed actions but not in unwilled actions thus supporting the idea that the production of the ERN is tied to slips in unwilled actions but not mistakes in willed actions

Arterial anatomy and arteriographic diagnosis of arteriogenic impotence

One hundred twenty-six bilateral selective arteriographic examinations of the iliopudendal vascular tree were performed after comprehensive multidisciplinary evaluation in patients with chronic erectile dysfunction. Best imaging results were obtained by performing the arteriography under epidural anesthesia after intracavernous injection of a vasoactive drug combination. The arteriography is mandatory prior to revascularization procedures. It is further indicated in primary erectile dysfunction and posttraumatic erectile failure. The importance of cavernosography and selective arteriography in primary erectile dysfunction is stressed. Increasing knowledge about the influence of vasoactive drugs on penile hemodynamics has led to its application in diagnosis and therapy of erectile dysfunction. Pharmacocovernosography, Doppler-ultrasound of penile arteries after intracavernous injection of a vasoactive drug combination, and pharmacoarteriography are refined techniques to prove a vascular etiology of erectile dysfunction. The results of the morphologic studies of the vascular system are correlated with functional testing of erectile capacity by intracavernous application of a papaverinephentolamine drug combination

Vegetation change of mountainous hay meadows to intensified management regime in organic farming

The whole vegetation assemblage of 60 relevés (4 m²) in a block design was examined at two mountainous hay meadow stands over a two-year period. All sites were situated at a certified organic farm, managed according to the guidelines of organic farming since 1995. According to the traditional management acreages are mowed two times per year followed by grazing and solid manure fertilisation in autumn. The effect of management intensity (two, three, four cuts per year and adapted fertilisation) was tested for coverage of most frequent species: Trisetum flavescens, Dactylis glomerata, Poa pratensis, Poa trivialis, Festuca pratensis, Lolium perenne, Trifolium repens, Taraxacum officinale agg., Carum carvi and Achillea millefolium. Our main interest was to detect how fast cover changes of different species occur. During the investigation period of two years, almost all taxa showed a significant alteration when mown more than 2 times a year. Stolon and rosette forming plants profited from increased management whereas tall tuft grasses lost coverage

Synthesis of ATM switch controller modules with the protocol compiler from Synopsis

In order to manage the higher complexity of VLSI chips and to reach shorter design cycles, the design effort becomes increasingly focused on higher levels of abstraction. We describe the modeling of some modules of an high speed telecommunication circuit, an ATM Switch Controller (ASC) using the Protocol Compiler or Dali (TM) from Synopsys (TM). Dali (TM) supports a fast and compact graphical entry of a protocol controller hardware description with graphical signs similarly to formula symbols. The output of the synthesis with Dali (TM) is simulated. Advantages of this design method are discussed and the results of the synthesis are presented

Zur Kenntnis der Rädertierfauna des Kinda-Stausees in Zentral-Burma (Aschelminthes: Rotatoria) : mit 1 Tabelle

Erstmals wird die Rädertierfauna des 1985 neu entstandenen Kinda-Stausees im Einzugsgebiet des Panlaung-Flusses in Burma (Myanmar) beschrieben und im verbreitungsgeschichtlichen Zusammenhang diskutiert. Die Arbeit ist zugleich die bislang umfassendste Untersuchung von Rotatorien aus dieser tiergeographisch interessanten asiatischen Region. Die Plankton- und Aufwuchsproben wurden auf mehreren Exkursionen 1987-89 gesammelt. Insgesamt konnten 94 monogononte und 5 bdelloide Rädertier-Arten nachgewiesen werden; davon ist Wulfertia kindensis neu für die Wissenschaft. Die überwiegende Zahl der Spezies sind Kosmopoliten.The fauna of rotifers (Rotatoria) from the newly built Kinda-Reservoir (1985) is described. The man-made lake is located in central Myanmar (formerly Burma) on the Panlaung Chaung, the left hand tributary to the Irrawaddy River. The impoundment serves the power generation and irrigation purposes. Since 1987 to 1989 plankton and periphyton sampies were collected which yielded 94 monogonont and 5 bdelloid species; only 7 belong to the tropical and subtropical fauna the remaining have cosmopolitan distribution. The communication provides the first comprehensive record of the rotifer fauna of Burma, one species Wulfertia kiruiensis was first described

Direct Current Auditory Evoked Potentials During Wakefulness, Anesthesia, and Emergence from Anesthesia

Direct current auditory evoked potentials (DC-AEPs) are a sensitive indicator of depth of anesthesia in ani-mals. However, they have never been investigated in humans. To assess the potential usefulness of DC-AEPs as an indicator of anesthesia in humans, we performed an explorative study in which DC-AEPs were recorded during propofol and methohexital anesthesia in hu-mans. DC-AEPs were recorded via 22 scalp electrodes in 19 volunteers randomly assigned to receive either propofol or methohexital. DC-AEPs were evoked by binaurally presented 2-s, 60-dB, 800-Hz tones; meas-urements were taken during awake baseline, anesthesia, and emergence. Statistical analysis included analy-sis of variance and discriminant analysis of data acquired during these three conditions. About 500 ms after stimulus presentation, DC-AEPs could be ob-served. These potentials were present only during base-line and emergence—not during anesthesia. Statistically significant differences were found between baseline and anesthesia and between anesthesia and emergence. In conclusion, similar effects, as reported in animal studies of anesthetics on the DC-AEPs, could be observed in anesthetized humans. These results dem-onstrate that DC-AEPs are potentially useful in the assessment of cortical function during anesthesia and might qualify the method for monitoring anesthesia in humans

On The Number of Times where a Simple Random Walk reaches a Nonnegative Height

The purpose of this note is to generalize the distribution of the local time of a purely binomial random walk for simple random walks allowing for three directions with different probabilities. (author's abstract)Series: Forschungsberichte / Institut für Statisti