Modelling of selective catalytic denox reactors – strategy for replacing deactivated catalyst elements

A simulation model for denox reactors (high dust) containing honeycomb catalysts and operating at temperatures between 300 and 400 °C has been developed. The model predicts the NO_x reduction as a function of process variables (temperature, gas velocity, NO_x concentration, NH₃/NO_x ratio) as well as a function of reactor and catalyst geometry (pitch diameter, length of catalyst layer, number of layers). Model parameters such as the rate constant and the adsorption equilibrium constant of NH₃ on the catalyst surface were determined by curve fitting of experimental data obtained in a pilot test unit. Based on model calculations, it is shown that the effect of catalyst poisoning (deactivation) on NO_x reduction is not the same for every catalyst layer. The lifetimes of catalyst elements located at the inlet to the reactor appear shorter than those of the elements positioned at the outlet from the reactor. Experimental verification of this theoretical finding is required.     

Primary coexistent adenocarcinoma and choriocarcinoma of the stomach. A case report and review of the literature

We report a case of primary gastric choriocarcinoma with liver metastasis. The mixed histologic patterns included adenocarcinoma, undifferentiated carcinoma, and choriocarcinoma. Immunohistologic staining for the beta-subunit of human chorionic gonadotrophin (beta-HCG) showed positive results in the choriocarcinoma, adenocarcinoma, and normal mucosal gland. However, positive HCG cells were present at different intensities in the choriocarcinoma, adenocarcinoma, and normal mucosal gland. The level of HCG was significantly increased in serum. This unusual tumor probably resulted from dedifferentiation of a primary adenocarcinoma or developed directly from the mucosal glands.     

Damping of Vibration by Actively Controlled Initial Distortions

A concept for the artificial damping of free vibration by means of actively controlled initial distortions imposed on the structure is presented. Two formulations for active control are presented: The first simulates the natural damping properties of structures, while the second uses a more sophisticated modal strategy of control (but with a faster damping process). The general idea of damping by actively forced distortions is explained and followed by a simple example for a one‐degree‐of‐freedom system. Then, the simulation of natural damping (which is a particular case of active control) and the possibility of accelerating the damping process by the modal optimal strategy are discussed and demonstrated with some examples for a two‐degree‐of‐freedom system. Finally, the vibration control of a four‐degree‐of‐freedom system is presented to demonstrate the efficiency of the proposed method. The method of active damping is described for truss structures, but it can be easily generalized to include frame structures as well.     

Regulation of IRK3 inward rectifier K+ channel by m1 acetylcholine receptor and intracellular magnesium

Inward rectifier K+ channels control the cell's membrane potential and neuronal excitability. We report that the IRK3 but not the IRK1 inward rectifier K+ channel activity is inhibited by m1 muscarinic acetylcholine receptor. This m1 modulation cannot be accounted for by protein kinase C, Ca2+, or channel phosphorylation, but can be mimicked by Mg2+. Based on quantitative analyses of IRK3 and two different IRK1 mutant channels bestowed with sensitivity to m1 modulation, we suggest that the resting Mg2+ level causes chronic inhibition of IRK3 channels, and m1 receptor stimulation may lead to an increase of cytoplasmic Mg2+ concentration and further channel inhibition, due to the ability of Mg2+ to lead these channels into a prolonged inactivated state.     

The influence of tempering on cleavage fracture stress and transition behaviour of bainitic 2.25Cr1Mo steel

The effect of tempering on the mechanical properties and on the cleavage fracture stress of bainitic 2.25Cr1Mo steel was studied in a variety of structures with the Hollomon-Jaffe parameter M ranging between 18.23 × 10³ and 21.70 × 10³. The rapid decrease in yield stress and UTS was observed up to value M = 20 × 10³. For values M > 20 × 10³ the reduction of yield stress and UTS slows down. The cleavage fracture stress continuously decreases with increasing value of M. Concurrently, the changes in dislocation density and in carbide size, morphology and distribution were observed. Various theories of cleavage origin of tempered bainitic microstructures are discussed. The transition temperatures, determined from impact Charpy test, reach minimum at M = 20 × 10³. Using Orowan's theory of initiation of the brittle fracture in steels, the minimum of transition temperatures may be explained by the different reduction rates of cleavage fracture stress and yield stress with value of M.     

Genghis Khan (Gek) as a putative effector for Drosophila Cdc42 and regulator of actin polymerization

The small GTPases Cdc42 and Rac regulate a variety of biological processes, including actin polymerization, cell proliferation, and JNK/mitogen-activated protein kinase activation, conceivably via distinct effectors. Whereas the effector for mitogen-activated protein kinase activation appears to be p65PAK, the identity of effector(s) for actin polymerization remains unclear. We have found a putative effector for Drosophila Cdc42, Genghis Khan (Gek), which binds to Dcdc42 in a GTP-dependent and effector domain-dependent manner. Gek contains a predicted serine/threonine kinase catalytic domain that is 63% identical to human myotonic dystrophy protein kinase and has protein kinase activities. It also possesses a large coiled-coil domain, a putative phorbol ester binding domain, a pleckstrin homology domain, and a Cdc42 binding consensus sequence that is required for its binding to Dcdc42. To study the in vivo function of gek, we generated mutations in the Drosophila gek locus. Egg chambers homozygous for gek mutations exhibit abnormal accumulation of F-actin and are defective in producing fertilized eggs. These phenotypes can be rescued by a wild-type gek transgene. Our results suggest that this multidomain protein kinase is an effector for the regulation of actin polymerization by Cdc42.     

Irreführende Leitbilder Zum Mythos der Individualisierung durch pharmakogenetische Behandlungskonzepte. Eine kritische Anmerkung

Zusammenfassung Die prospektive Analyse der ethischen Implikationen medizinisch-technischer Innovationen läuft immer auch Gefahr, sich in den Wunschbildern von Marketingexperten zu verfangen. Vor diesem Hintergrund könnte es durchaus nützlich sein, die Erkenntnisse der Wissenschafts- und Technikforschung zur Genese und Entwicklung neuer Techniken auszuschöpfen. Dies erscheint gerade auch für die ins Phantastische weisende Zukunft der Individualisierung medikamentöser Therapie, wie man ihr häufig in der Beschreibung pharmakogenetischer Behandlungskonzepte begegnet, angebracht. Techniken, die sich noch im Entwicklungsstadium befinden und deren breite Anwendung noch einige Jahre auf sich warten lassen wird, sollten sehr sorgfältig auf ihren Realitätsgehalt und das zu erwartende Leistungspotenzial hin analysiert werden. Dazu gehört v. a. auch eine kritische Auseinandersetzung mit den Leitbildern, Visionen und Nutzenversprechen, mit denen technische Innovationen oft sehr absichtsvoll ausgestattet werden. Wird dabei die Distanz zur Rhetorik der Protagonisten der neuen Techniken nicht gewahrt, gerät die ethische Reflexion unvermittelt in die Rolle, profane Marketingstrategien wortgewandt und ideenreich zu veredeln.     

Beyond imprisonment of meaning: Technology facilitating redefining

Defining is a natural and necessary response to an ambiguous world, but causes fixation of categories and perspectives. On the basis of two earlier studies of project groups, we came to argue that redefining, and hence constructing various ways in which one perceives and understands something, enables groups to overcome imprisonment in meaning, establishing continuous development and flexibility. In this article, we first build a rationale for facilitating a process of redefining, to be taken into account when designing technology. Departing from this rationale, we discuss features of groupware technology that permit change by being flexible, and evoke redefining by engaging the user more actively. In so doing, we argue to think along new lines in the design of communication and collaboration technology. This paper proposes a specific perspective on technology, facilitating groups to engage in a productive, creative fashion of exploiting meaning potential.