A two-lobe Journal Bearing with adjustable Gap Geometry for Vibration Reduction of flexible Rotors

Flexible rotors in journal bearings can exhibit large vibration amplitudes during the passage of bending critical speeds.  To reduce these vibrations, a two-lobe journal bearing with adjustable gap geometry is presented. By an adjustment of  the gap height, stiffness and damping properties of the bearing and as a consequence the damping ratio of the rotor  system can be varied during the operation. When the system passes a critical speed in a run-up process, a large gap is  adjusted for higher damping. After the resonance pass through, the gap height is reduced to increase the load  carrying  capacity and to enlarge the stability margin. Investigating the Jeffcott rotor in adjustable journal bearings demonstrates the basic effects. For a validation, a test rig is set up and a related mathematical model is created.  Various experiments are made and compared with numerical results

Resonance production from jet fragmentation

Short lived resonances are sensitive to the medium properties in heavy-ion collisions. Heavy hadrons have larger probability to be produced within the quark gluon plasma phase due to their short formation times. Therefore heavy mass resonances are more likely to be affected by the medium, and the identification of early produced resonances from jet fragmentation might be a viable option to study chirality. The high momentum resonances on the away-side of a triggered di-jet are likely to be the most modified by the partonic or early hadronic medium. We will discuss first results of triggered hadron-resonance correlations in Cu+Cu heavy ion collisions.Comment: Hot Quarks Colorado 2008 Proceedings, 4 pages 5 figure

The oxygen-independent metabolism of cyclic monoterpenes in Castellaniella defragrans 65Phen

BACKGROUND: The facultatively anaerobic betaproteobacterium Castellaniella defragrans 65Phen utilizes acyclic, monocyclic and bicyclic monoterpenes as sole carbon source under oxic as well as anoxic conditions. A biotransformation pathway of the acyclic β-myrcene required linalool dehydratase-isomerase as initial enzyme acting on the hydrocarbon. An in-frame deletion mutant did not use myrcene, but was able to grow on monocyclic monoterpenes. The genome sequence and a comparative proteome analysis together with a random transposon mutagenesis were conducted to identify genes involved in the monocyclic monoterpene metabolism. Metabolites accumulating in cultures of transposon and in-frame deletion mutants disclosed the degradation pathway. RESULTS: Castellaniella defragrans 65Phen oxidizes the monocyclic monoterpene limonene at the primary methyl group forming perillyl alcohol. The genome of 3.95 Mb contained a 70 kb genome island coding for over 50 proteins involved in the monoterpene metabolism. This island showed higher homology to genes of another monoterpene-mineralizing betaproteobacterium, Thauera terpenica 58Eu(T), than to genomes of the family Alcaligenaceae, which harbors the genus Castellaniella. A collection of 72 transposon mutants unable to grow on limonene contained 17 inactivated genes, with 46 mutants located in the two genes ctmAB (cyclic terpene metabolism). CtmA and ctmB were annotated as FAD-dependent oxidoreductases and clustered together with ctmE, a 2Fe-2S ferredoxin gene, and ctmF, coding for a NADH:ferredoxin oxidoreductase. Transposon mutants of ctmA, B or E did not grow aerobically or anaerobically on limonene, but on perillyl alcohol. The next steps in the pathway are catalyzed by the geraniol dehydrogenase GeoA and the geranial dehydrogenase GeoB, yielding perillic acid. Two transposon mutants had inactivated genes of the monoterpene ring cleavage (mrc) pathway. 2-Methylcitrate synthase and 2-methylcitrate dehydratase were also essential for the monoterpene metabolism but not for growth on acetate. CONCLUSIONS: The genome of Castellaniella defragrans 65Phen is related to other genomes of Alcaligenaceae, but contains a genomic island with genes of the monoterpene metabolism. Castellaniella defragrans 65Phen degrades limonene via a limonene dehydrogenase and the oxidation of perillyl alcohol. The initial oxidation at the primary methyl group is independent of molecular oxygen

Fast solvers and efficient numerical cfd techniques for dynamic porous media problems

We present a fully implicit, monolithic finite element solution scheme to efficiently solve the governing set of differential algebraic equations of incompressible poroelastodynamics. Thereby, we proceed from a two-dimensional, biphasic, saturated porous medium model with intrinsically coupled and incompressible solid and fluid constituents. Our approach, motivated by well-accepted CFD techniques and originally developed for the efficient simulation of incompressible flow problems, is characterized by the following aspects: (1) a special treatment of the algebraically coupled volume balance equation leading to a reduced form of the boundary conditions; (2) usage of a higher-order accurate mixed LBB-stable finite element pair with piecewise discontinuous pressure for the spatial discretization; (3) application of the fully implicit 2nd-order Crank-Nicolson scheme for the time discretization; (4) use of a special fast multigrid solver for the resulting discrete linear equation system. For the purpose of validation and to expose the merits and benefits of our new solution strategy in comparison to other established approaches, canonical one- and two-dimensional wave propagation problems are solved. Finally, a large-scale, dynamic soil-structure interaction problem serves to reveal the efficiency of the special multigrid solver in combination with the chosen finite element discretization

Effect of Hydrostatic Pressure on the Superconductivity in NaxCoO2.yH2O

The effect of hydrostatic pressure on the superconducting transition temperature of Na{0.35}CoO{2}.yH{2}O was investigated by ac susceptibility measurements up to 1.6 GPa. The pressure coefficient of T{c} is negative and the dependence T{c}(p) is nonlinear over the pressure range investigated. The magnitude of the average dlnT{c}/dp=-0.07 GPa^{-1} is comparable to the pressure coefficient of electron-doped high-T{c} copper oxide superconductors with a similar value of T{c}. Our results provide support to the assumption of two-dimensional superconductivity in Na{0.35}CoO{2}.yH{2}O, which is similar to the cuprate systems, and suggest that intercalation of larger molecules may lead to an enhancement of T{c}.Comment: Revised Manuscrip

Influence of geometric and physical nonlinearities on the internal resonances of a finite continuous rod with a microstructure

In this work, nonlinear longitudinal vibrations of a finite composite rod are studied including geometric and physical nonlinearities. An original boundary value problem for a heterogeneous rod yielded by the macroscopic approximation obtained earlier by the higher-order asymptotic homogenization method is used. The effects of internal resonances and modes coupling are predicted, validated and analyzed. The defined novel continuous problem governed by PDEs is solved using space-discretization and the method of multiple time scales. We are aimed at understanding and analyzing how the presence of the microstructure influences the processes of mode interaction. It is shown that, depending on a scaling relation between the amplitude of the vibrations and the size of the unit cell, different scenarios of the modes coupling can be realized. Additionally to the asymptotic solution, numerical simulation of the modes coupling is performed by means of the Runge-Kutta fourth-order method. The obtained numerical and analytical results demonstrate good qualitative agreement

Possible glueball production in relativistic heavy-ion collisions

Within a thermal model we estimate possible multiplicities of scalar glueballs in central Au+Au collisions at AGS, SPS, RHIC and LHC energies. For the glueball mass in the region 1.5-1.7 GeV, the model predicts on average (per event) 0.5-1.5 glueballs at RHIC and 1.5-4 glueballs at LHC energies. Possible enhancement mechanisms are discussed.Comment: 8 pages, 2 figure

Explainable Artificial Intelligence for Mechanics: Physics-Explaining Neural Networks for Constitutive Models

(Artificial) neural networks have become increasingly popular in mechanics and materials sciences to accelerate computations with model order reduction techniques and as universal models for a wide variety of materials. However, the major disadvantage of neural networks remains: their numerous parameters are challenging to interpret and explain. Thus, neural networks are often labeled as black boxes, and their results often elude human interpretation. The new and active field of physics-informed neural networks attempts to mitigate this disadvantage by designing deep neural networks on the basis of mechanical knowledge. By using this a priori knowledge, deeper and more complex neural networks became feasible, since the mechanical assumptions can be explained. However, the internal reasoning and explanation of neural network parameters remain mysterious. Complementary to the physics-informed approach, we propose a first step towards a physics-explaining approach, which interprets neural networks trained on mechanical data a posteriori. This proof-of-concept explainable artificial intelligence approach aims at elucidating the black box of neural networks and their high-dimensional representations. Therein, the principal component analysis decorrelates the distributed representations in cell states of RNNs and allows the comparison to known and fundamental functions. The novel approach is supported by a systematic hyperparameter search strategy that identifies the best neural network architectures and training parameters. The findings of three case studies on fundamental constitutive models (hyperelasticity, elastoplasticity, and viscoelasticity) imply that the proposed strategy can help identify numerical and analytical closed-form solutions to characterize new materials

Linalool isomerase, a membrane-anchored enzyme in the anaerobic monoterpene degradation in Thauera linaloolentis 47Lol

Background: Thauera linaloolentis 47Lol uses the tertiary monoterpene alcohol (R,S)-linalool as sole carbon and energy source under denitrifying conditions. The conversion of linalool to geraniol had been observed in carbon-excess cultures, suggesting the presence of a 3,1-hydroxyl-Delta(1)-Delta(2)-mutase (linalool isomerase) as responsible enzyme. To date, only a single enzyme catalyzing such a reaction is described: the linalool dehydratase/isomerase (Ldi) from Castellaniella defragrans 65Phen acting only on (S)-linalool. Results: The linalool isomerase activity was located in the inner membrane. It was enriched by subcellular fractionation and sucrose gradient centrifugation. MALDI-ToF MS analysis of the enriched protein identified the corresponding gene named lis that codes for the protein in the strain with the highest similarity to the Ldi. Linalool isomerase is predicted to have four transmembrane helices at the N-terminal domain and a cytosolic domain. Enzyme activity required a reductant for activation. A specific activity of 3.42 +/- 0.28 nkat mg * protein(-1) and a k(M) value of 455 +/- 124 mu M were determined for the thermodynamically favored isomerization of geraniol to both linalool isomers at optimal conditions of pH 8 and 35 degrees C. Conclusion: The linalool isomerase from T. linaloolentis 47Lol represents a second member of the enzyme class 5.4.4.4, next to the linalool dehydratase/isomerase from C. defragrans 65Phen. Besides considerable amino acid sequence similarity both enzymes share common characteristics with respect to substrate affinity, pH and temperature optima, but differ in the dehydratase activity and the turnover of linalool isomers

Quantification of total T-cell receptor diversity by flow cytometry and spectratyping

BACKGROUND: T-cell receptor diversity correlates with immune competency and is of particular interest in patients undergoing immune reconstitution. Spectratyping generates data about T-cell receptor CDR3 length distribution for each BV gene but is technically complex. Flow cytometry can also be used to generate data about T-cell receptor BV gene usage, but its utility has not been compared to or tested in combination with spectratyping. RESULTS: Using flow cytometry and spectratype data, we have defined a divergence metric that quantifies the deviation from normal of T-cell receptor repertoire. We have shown that the sample size is a sensitive parameter in the predicted flow divergence values, but not in the spectratype divergence values. We have derived two ways to correct for the measurement bias using mathematical and statistical approaches and have predicted a lower bound in the number of lymphocytes needed when using the divergence as a substitute for diversity. CONCLUSIONS: Using both flow cytometry and spectratyping of T-cells, we have defined the divergence measure as an indirect measure of T-cell receptor diversity. We have shown the dependence of the divergence measure on the sample size before it can be used to make predictions regarding the diversity of the T-cell receptor repertoire