Two different views on collision detection

In this article, we present two algorithms for precise collision detection between two potentially colliding objects. The first one uses axis-aligned bounding boxes (AABB) and is a typical representative of a computational geometry algorithm. The second one uses spherical distance fields originating in image processing. Both approaches addresses the following challenges of collision detection algorithms: just in time, little resources, inclusive etc. Thus both approaches are scalable in the information they give in collision determination and the analysis up to a fixed refinement level, the collision time depends on the granularity of the bounding volumes and it is also possible to estimate the time bounds for the collision test tightly     

GTPase activity of Rab5 acts as a timer for endocytic membrane fusion

The GTPase cycle is a versatile regulatory mechanism directing many cell functions, and Rab family members use it to regulate intracellular transport. Current models propose that GTP hydrolysis by Rab proteins is either required for membrane fusion or occurs afterwards to allow recycling of the protein. To measure the GTPase activity of Rab5 in endocytic membrane fusion, we engineered a mutant that preferentially binds xanthosine 5'-triphosphate (XTP),Rab5(D136N) and monitored the kinetics of [alpha(32)P]-XTP hydrolysis in situ during endosome fusion in vitro. Surprisingly, nucleotide hydrolysis occurred even in the absence of membrane fusion, indicating that membrane-bound Rab5 undergoes futile cycles of GTP(XTP) binding and hydrolysis. Nucleotide triphosphate hydrolysis by Rab5 is not conditional on membrane fusion and is reduced by its effector Rabaptin-5. Our data reveal that the GTP cycle of Rab proteins differs from that of other GTPases (for example, EF-Tu) and indicate that GTP hydrolysis acts as a timer that determines the frequency of membrane docking/fusion events.     

The TTA's Approach to Resilience after Transient Upsets

The Time-Triggered Architecture, as architecture for safety-critical real-time applications, incorporates fault-tolerance mechanisms to ensure correct system operation despite failures. The primary fault hypothesis of the TTA claims to tolerate either the arbitrary failure of any one of its nodes or the passively arbitrary failure of any one of its communication channels. To cover these failure modes, active redundancy techniques are used, which basically means that nodes and channels are physically replicated. The primary fault hypothesis, is, however, not strong enough for certain applications that have to tolerate transient upsets of multiple, possibly all, components in the system. Such a transient upset of the system may break up the synchrony of the nodes and leave disjoined sets of nodes synchronized to each other while the overall synchronization is lost. Although the TTA provides a clique avoidance algorithm that is able to correct a wide class of such multiple transient failures, a stronger algorithm is needed for full coverage. In this paper we discuss a secondary fault hypothesis for the TTA that addresses the transient upset of multiple components and present a new clique resolving algorithm based on the TTA's integrated diagnosis and startup service. This paper is a revised version of Steiner et al. (2003). This work has been funded by the European Project DECOS (Project number: IST-511764). Michael Paulitsch is currently affiliated with Honeywell International.     

In vitro import of pre-ferredoxin-NADP+-oxidoreductase from Cyanophora paradoxa into cyanelles and into pea chloroplasts

Using a novel cyanelle isolation procedure we showed that pre-ferredoxin-NADP+-oxidoreductase (pre-FNR) from C. paradoxa is translocated in vitro across the peptidoglycan-containing cyanelle envelope. Efficient import was also observed in a heterologous system with pea chloroplasts as the recipient organelles. These results support the conclusion derived from comparative analysis of plastid genome organization, that all plastids originate from a common semi-autonomous endosymbiotic ancestor.     

Radiologic interventions in anastomosis complications after lung transplantation

Over a period of one year the iodine content of the milk of 28 bavarian dairies was determined monthly by a gaschromatographical method. The annual mean value was 115 micrograms/l. In March, April and November, December, respectively a distinct increase of the concentration was observed. In the southern part of Bavaria the iodine contents were below 100 micrograms/l in contrast to the region Oberpfalz and Franken where contents up to 150 micrograms/l could be determined. Compared with concentrations in different tables the iodine content in bavarian milk could increase the iodine uptake up to 6%.     

In vitro development and preservation of specific features of collecting duct epithelial cells from embryonic rabbit kidney are regulated by the electrolyte environment

During kidney development the embryonic collecting duct (CD) epithelium changes its function. The capability for nephron induction is lost and the epithelium develops into functional principal (P) and intercalated (IC) cells. Aldosterone is able to modulate this differentiation. Consequently we investigated whether increased concentrations of extracellular NaCl or Na gluconate may also have an influence on the development of individual CD cell features. Embryonic CD epithelia were isolated from neonatal rabbit kidneys, placed on tissue carriers and cultured in gradient containers, which were constantly perfused with medium for 13 days. Isotonic culture conditions could be mimicked, when on both the luminal and basal side standard Iscove's Modified Dulbecco's Medium (IMDM) was used. In another set of experiments, gradient culture was performed. Standard IMDM was applied on the basal side and IMDM supplemented with 12 mM NaCl and 17 mM Na gluconate on the luminal side. This adaptation of IMDM led to the same Na concentrations as found in the serum of neonatal rabbits. The development of CD cell features was monitored by cellular markers such as the monoclonal antibodies (Mabs) 703 and 503 recognizing P and IC cell features respectively. Epithelia cultured under isotonic conditions showed less than 5% Mab 703- and 503-immunopositive cells. In contrast, epithelia cultured in a luminal-basal medium gradient revealed more than 80% positive cells. Immunoreactivity started to develop after a long lag period of 4 days, then increased continuously during the following 5 days and reached a maximum at day 14. When the medium gradient was then changed to an isotonic environment for another 5 days immunoreactivity for Mab 703 remained stable, while the number of Mab 503-positive cells was found to be decreased to 10%. Thus, the extra-cellular electrolyte environment not only induces but also preserves individual cell features.