Artificial added mass instabilities in sequential staggered coupling of nonlinear structures and incompressible viscous flows

Within this paper the so-called artificial added mass effect is investigated which is responsible for devastating instabilities within sequentially staggered Fluid-structure Interaction (FSI) simulations where incompressible fluids are considered.A discrete representation of the added mass operator M_A is given and ‘instability conditions’ are evaluated for different temporal discretisation schemes. It is proven that for every sequentially staggered scheme and given spatial discretisation of a problem, a mass ratio between fluid and structural mass density can be found at which the coupled system becomes unstable. The analysis is quite general and does not depend upon the particular spatial discretisation schemes used. However here special attention is given to stabilised finite elements employed on the fluid partition. Numerical investigations further highlight the results.     

Protein kinase C-mediated inhibition of transmembrane signalling through CCK(A) and CCK(B) receptors

1. The rat CCK(A) and CCK(B) receptors were stably expressed in Chinese hamster ovary (CHO-09) cells in order to compare modes of signal transduction and effects of protein kinase C (PKC) thereupon. 2. Spectrofluorophotometry of Fura-2-loaded cells revealed that both receptors retained their pharmacological characteristics following expression in CHO cells. Sulphated cholecystokinin-(26-33)-peptide amide (CCK-8-S) increased the cytosolic Ca2+ concentration ([Ca2+]i) in CCK(A) cells, measured as an increase in Fura-2 fluorescence emission ratio, 1000 fold more potently than its non-sulphated form (CCK-8-NS) (EC50 values of 0.19 nM and 0.18 microM, respectively). By contrast, CCK-8-S and CCK-8-NS were equally potent in CCK(B) cells (EC50 values of 0.86 nM and 1.18 nM, respectively). The CCK(A) receptor agonist JMV-180 increased [Ca2+]i only in CCK(A) cells. Likewise, pentagastrin increased [Ca2+]i only in CCK(B) cells. Finally, CCK-8-S-induced Ca2+ signalling through the CCK(A) receptor was most potently inhibited by the CCK(A) receptor antagonist L364,718, whereas the CCK(B) receptor antagonist L365,260 was more potent in CCK(B) cells. 3. Receptor-mediated activation of adenylyl cyclase was measured in the presence of the inhibitor of cyclic nucleotide phosphodiesterase activity, 3-isobutyl-1-methylxanthine. CCK-8-S and, to a lesser extent, CCK-8-NS, but not JMV-180 or pentagastrin, stimulated the accumulation of cyclicAMP in CCK(A) cells. By contrast, none of these agonists increased cyclicAMP in CCK(B) cells. 4. Short-term (3 min) pretreatment with the PKC activator 12-O-tetradecanoylphorbol 13-acetate (TPA) evoked a rightward shift of the dose-response curve for the Ca2+ mobilizing effect of CCK-8-S in both cell lines. In addition, short-term TPA pretreatment markedly reduced CCK-8-S-induced cyclicAMP accumulation in CCK(A) cells. In both cases, the inhibitory effect of TPA was abolished by the PKC inhibitors, GF-109203X and staurosporine, whereas no inhibition was observed with the inactive phorbol ester, 4-alpha-phorbol 12-myristate 13-acetate. 5. During prolonged TPA treatment, the cells gradually recovered from phorbol ester inhibition and in the case of CCK-8-S-induced Ca2+ mobilization complete recovery was achieved after 24 h of TPA treatment. Western blot analysis revealed that this recovery was paralleled by down-regulation of PKC-alpha, suggesting the involvement of this PKC isotype in the inhibitory action of TPA. 6. This study demonstrates that following expression in CHO cells (i) both CCK(A) and CCK(B) receptors are coupled to Ca2+ mobilization, (ii) only CCK(A) receptors are coupled to cyclicAMP formation and (iii) with both receptors signalling is inhibited by PKC.     

PilT mutations lead to simultaneous defects in competence for natural transformation and twitching motility in piliated Neisseria gonorrhoeae

Neisseria gonorrhoeae, the Gram-negative aetiological agent of gonorrhoeae, is one of many mucosal pathogens of man that expresses competence for natural transformation. Expression of this phenotype by gonococci appears to rely on the expression of type IV pili (Tfp), but the mechanistic basis for this relationship remains unknown. During studies of gonococcal pilus biogenesis, a homologue of the PilT family of proteins, required for Tfp-dependent twitching motility in Pseudomonas aeruginosa and social gliding motility in Myxococcus xanthus, was discovered. Like the findings in these other species, we show here that gonococcal PilT mutants constructed in vitro no longer display twitching motility. In addition, we demonstrate that they have concurrently lost the ability to undergo natural transformation, despite the expression of structurally and morphologically normal Tpf. These results were confirmed by the findings that two classes of spontaneous mutants that failed to express twitching motility and transformability carried mutations in PilT. Piliated PilT mutants and a panel of pilus assembly mutants were found to be deficient in sequence-specific DNA uptake into the cell, the earliest demonstrable step in neisserial competence. The PilT-deficient strains represent the first genetically defined mutants that are defective in DNA uptake but retain Tfp expression.     

Robust pole assignment for incomplete nonlinear decoupling applied to robots

A robustness analysis and synthesis for incomplete nonlinear decoupling for a class of nonlinear systems is discussed. Rigid and elastic-joint robot models belong to this class. For the elastic case, a transformation facilitates the robustness analysis under a weak assumption. Charts with H ₁- and H - norms of closed-loop disturbance transfer functions of the nonlinear-decoupled system are presented for a robust pole assignment.     

From perception to action using observed actions to learn gestures

User Modeling and User-Adapted Interaction - Pervasive computing environments deliver a multitude of possibilities for human–computer interactions. Modern technologies, such as gesture...     

State-of-the-art of long-term preservation in product lifecycle management

Providing access to digital information for the indefinite future is the intention of long-term digital preservation systems. One application domain that certainly needs to implement such long-term digital preservation processes is the design and engineering industry. In this industry, products are designed, manufactured, and operated with the help of sophisticated software tools provided by product lifecycle management (PLM) systems. During all PLM phases, including geographically distributed cross-domain and cross-company collaboration, a huge amount of heterogeneous digital product data and metadata is created. Legal and economic requirements demand that this product data has to be archived and preserved for a long-time period. Unfortunately, the software that is able to interpret the data will become obsolete earlier than the data since the software and hardware lifecycle is relatively short-lived compared to a product lifecycle. Companies in the engineering industry begin to realize that their data is in danger of becoming unusable while the products are in operation for several decades. To address this issue, different academic and industrial initiatives have been initiated that try to solve this problem. This article provides an overview of these projects including their motivations, identified problems, and proposed solutions. The studied projects are also verified against a classification of important aspects regarding scope and functionality of digital preservation in the engineering industry. Finally, future research topics are identified.     

Ionic conductivity of synthetic analcime,sodalite and offretite

The ionic conductivity of pressed pellets of dehydrated synthetic analcime, sodalite and offretite was determined by a.c. measurements within the range 10 Hz to 10 MHz. The ionic conductivity values of those zeolites exchanged with various monovalent cations were determined by the complex impedance plane method. The conduction activation energies range between 63 and 101 kJ mol^–1. Sodium analcime shows the best ionic conductivity, namely 1.8×10^–4–1 cm^–1 at 400° C. A comparison with the conductivity of other ion-conducting solids was made.     

Photodegradation of the carbamate insecticide propoxur

Summary In order to examine the photostability of the insecticide propoxur (2-isopropoxyphenyl-N-methylcarbamate) in the field model experiments with organic solvents were performed. Photodegradation (>280 nm) of propoxur was found to be more efficient in isopropanol solution than in the presence of cyclohexane or cyclohexene. Photolysis in isopropanol and cyclohexane mainly resulted in formation of isopropylphenyl ether. As a trace component 2-isopropoxyphenol was detected. In the presence of cyclohexene on the other hand photomineralisation was found to be the main degradation pathway.

---

Photoabbau des Carbamat-Insecticides Propoxur

Zusammenfassung Zur Voruntersuchung der Photostabilität des Insecticides Propoxur (2-Isopropoxyphenyl-N-methylcarbamat) im Freiland wurden Modellexperimente in organischen Lösungsmitteln durchgeführt. Der Photoabbau (>280 nm) von Propoxur verlief in Isopropanol deutlich schneller als in Cyclohexan oder Cyclohexen. Bei Bestrahlung in Isopropanol und Cyclohexan entstand als Hauptprodukt Isopropylphenylether, daneben Spuren von 2-Isopropoxyphenol. Dagegen erfolgte in Cyclohexen der Abbau hauptsächlich über eine Photomineralisierung.

---

---

Dedicated to Professor Dr. H. Niebergall on the occasion of his 65th birthday