More Flexible Damping Systems for Blades and Vanes

The blades and the vanes of aero engines are subject to very high thermo-mechanical loads. In some cases, an additional damping system is necessary to reach the lifetime goals. Commonly, damping systems based on energy dissipation due to friction are used, e.g. under platform dampers for blades and spring dampers for the vanes. These damping systems have some limitations: under platform dampers work well mostly for just one mode family, their effectiveness is limited relative to rotational speed (because of the associated contact forces) and is dependent on the excitation order. The spring dampers work well for more than one mode family but their effectiveness is limited concerning the available contact force (just one value). Additionally, the use of the spring dampers requires a significant, sometimes suboptimal design change of the vane cluster. In this paper, some alternative damping systems are introduced and analyzed. All these new systems offer additional possibilities for damping and give more design flexibility. Two of them: insert damping and rocking damping are also based on frictional energy dissipation. The third one, impulse mistuning, adopts a special kind of absorption and is based on the so called targeted energy transfer. The analytical results for the insert damping systems were presented previously in Borufka et al. (2009), while in this paper the experimental validation by shaker tests is shown. The rocking damping was not presented so far – to the knowledge of the authors. Impulse mistuning was first presented in: Hartung and Retze (2011) and Hartung et al. (2016). In this work, an overview of such damping systems and some additional information on the experimental validation of some impulse mistuning systems are presented

LAPAROSCOPIC VERSUS OPEN SURGERY FOR ACUTE ADHESIVE SMALL-BOWEL OBSTRUCTION : A PROPENSITY SCORE-MATCHED ANALYSIS

Background and Aims: The laparoscopic approach has been increasingly used to treat adhesive small-bowel obstruction. The aim of this study was to compare the outcomes of a laparoscopic versus an open approach for adhesive small-bowel obstruction. Material and Methods: Data were retrospectively collected on patients who had surgery for adhesive small-bowel obstruction at a single academic center between January 2010 and December 2012. Patients with a contraindication for the laparoscopic approach were excluded. A propensity score was used to match patients in the laparoscopic and open surgery groups based on their preoperative parameters. Results: A total of 25 patients underwent laparoscopic adhesiolysis and 67 patients open adhesiolysis. The open adhesiolysis group had more suspected bowel strangulations and more previous abdominal surgeries than the laparoscopic adhesiolysis group. Severe complication rate (Clavien-Dindo 3 or higher) was 0% in the laparoscopic adhesiolysis group versus 14% in the open adhesiolysis group (p = 0.052). Twenty-five propensity score-matched patients from the open adhesiolysis group were similar to laparoscopic adhesiolysis group patients with regard to their preoperative parameters. Length of hospital stay was shorter in the laparoscopic adhesiolysis group compared to the propensity score-matched open adhesiolysis group (6.0 vs 10.0 days, p = 0.037), but no differences were found in severe complications between the laparoscopic adhesiolysis and propensity score-matched open adhesiolysis groups (0% vs 4%, p = 0.31). Conclusion: Patients selected to be operated by the open approach had higher preoperative morbidity than the ones selected for the laparoscopic approach. After matching for this disparity, the laparoscopic approach was associated with a shorter length of hospital stay without differences in complications. The laparoscopic approach may be a preferable approach in selected patients.Peer reviewe

A Mechanism-Based Approach to Life Prediction for a Nickel-Base Alloy subjected to Cyclic and Creep-Fatigue

A large number of damage parameters have been proposed to estimate cyclic fatigue life predominantly at ambient temperatures. However, especially in aerospace and automotive industry fatigue models with a wide temperature application range are required. Here, the regimes of high temperature creep-fatigue and nonisothermal thermo-mechanical fatigue are of particular interest. Within the present work a new mechanism-based life prediction approach is proposed for a nickel-base superalloy. The ability of the model to describe fatigue at low, intermediate, and also at high temperatures is investigated. Isothermal, as well as non-isothermal loading conditions are considered. The enhanced model formulation is based on the micro crack growth parameter Z d introduced by Heitmann et al. (1984). The model incorporates a threshold concept and corrections for mean stress and creep effects. In addition the detrimental effects caused by oxygen-induced embrittlement of the near tip region are accounted for by a parabolic oxidation approach. Test data from literature is used to compare the proposed model to several other fatigue models. Basis for all life prediction approaches under investigation is the stress-strain response of the material obtained by finite element analysis. Therefore, an inelastic constitutive model is applied. The fatigue model accuracy is evaluated on a statistical basis through an evaluation of the variance in the ratio of predicted life to actual life. This is done for the entire test database as well as for subsets, like isothermal, thermo-mechanical, and dwell tests only

WordCluster: detecting clusters of DNA words and genomic elements

<p>Abstract</p> <p>Background</p> <p>Many <it>k-</it>mers (or DNA words) and genomic elements are known to be spatially clustered in the genome. Well established examples are the genes, TFBSs, CpG dinucleotides, microRNA genes and ultra-conserved non-coding regions. Currently, no algorithm exists to find these clusters in a statistically comprehensible way. The detection of clustering often relies on densities and sliding-window approaches or arbitrarily chosen distance thresholds.</p> <p>Results</p> <p>We introduce here an algorithm to detect clusters of DNA words (<it>k-</it>mers), or any other genomic element, based on the distance between consecutive copies and an assigned statistical significance. We implemented the method into a web server connected to a MySQL backend, which also determines the co-localization with gene annotations. We demonstrate the usefulness of this approach by detecting the clusters of CAG/CTG (cytosine contexts that can be methylated in undifferentiated cells), showing that the degree of methylation vary drastically between inside and outside of the clusters. As another example, we used <it>WordCluster </it>to search for statistically significant clusters of olfactory receptor (OR) genes in the human genome.</p> <p>Conclusions</p> <p><it>WordCluster </it>seems to predict biological meaningful clusters of DNA words (<it>k-</it>mers) and genomic entities. The implementation of the method into a web server is available at <url>http://bioinfo2.ugr.es/wordCluster/wordCluster.php</url> including additional features like the detection of co-localization with gene regions or the annotation enrichment tool for functional analysis of overlapped genes.</p

Characterization of phosphorus-regulated miR399 and miR827 and their isomirs in barley under phosphorus-sufficient and phosphorus-deficient conditions

17 p.BACKGROUND: miR399 and miR827 are both involved in conserved phosphorus (P) deficiency signalling pathways. miR399 targets the PHO2 gene encoding E2 enzyme that negatively regulates phosphate uptake and root-to-shoot allocation, while miR827 targets SPX-domain-containing genes that negatively regulate other P-responsive genes. However, the response of miR399 and miR827 to P conditions in barley has not been investigated. RESULTS: In this study, we investigated the expression profiles of miR399 and miR827 in barley (Hordeum vulagre L.) under P-deficient and P-sufficient conditions. We identified 10 members of the miR399 family and one miR827 gene in barley, all of which were significantly up-regulated under deficient P. In addition, we found many isomirs of the miR399 family and miR827, most of which were also significantly up-regulated under deficient P. Several isomirs of miR399 members were found to be able to cleave their predicted targets in vivo. Surprisingly, a few small RNAs (sRNAs) derived from the single-stranded loops of the hairpin structures of MIR399b and MIR399e-1 were also found to be able to cleave their predicted targets in vivo. Many antisense sRNAs of miR399 and a few for miR827 were also detected, but they did not seem to be regulated by P. Intriguingly, the lowest expressed member, hvu-miR399k, had four-fold more antisense sRNAs than sense sRNAs, and furthermore under P sufficiency, the antisense sRNAs are more frequent than the sense sRNAs. We identified a potential regulatory network among miR399, its target HvPHO2 and target mimics HvIPS1 and HvIPS2 in barley under P-deficient and P-sufficient conditions. CONCLUSIONS: Our data provide an important insight into the mechanistic regulation and function of miR399, miR827 and their isomirs in barley under different P conditions.Michael Hackenberg, Bu-Jun Shi, Perry Gustafson and Peter Langridg

On insertion-deletion systems over relational words

We introduce a new notion of a relational word as a finite totally ordered set of positions endowed with three binary relations that describe which positions are labeled by equal data, by unequal data and those having an undefined relation between their labels. We define the operations of insertion and deletion on relational words generalizing corresponding operations on strings. We prove that the transitive and reflexive closure of these operations has a decidable membership problem for the case of short insertion-deletion rules (of size two/three and three/two). At the same time, we show that in the general case such systems can produce a coding of any recursively enumerable language leading to undecidabilty of reachability questions.Comment: 24 pages, 8 figure