Vibration of a flexible pipe conveying viscous pulsating fluid flow

The non-linear equations of motion of a flexible pipe conveying unsteadily flowing fluid are derived from the continuity and momentum equations of unsteady flow. These partial di!erential equations are fully coupled through equilibrium of contact forces, the normal compatibility of velocity at the fluid} pipe interfaces, and the conservation of mass and momentum of the transient fluid. Poisson coupling between the pipe wall and fluid is also incorporated in the model. A combination of the finite difference method and the method of characteristics is employed to extract displacements, hydrodynamic pressure and flow velocities from the equations. A numerical example of a pipeline conveying fluid with a pulsating flow is given and discussed

Analysis of the vibration of pipes conveying fluid

The dynamic equilibrium matrix equation for a discretized pipe element containing flowing fluid is derived from the Lagrange principle, the Ritz method and consideration of the coupling between the pipe and fluid. The Eulerian approach and the concept of fictitious loads for kinematic correction are adopted for the analysis of geometrically non-linear vibration. The model is then deployed to investigate the vibratory behaviour of the pipe conveying fluid. The results for a long, simply supported, fluid-conveying pipe subjected to initial axial tensions are compared with experimentally obtained results and those from a linear vibration model

Leader behavior and follower work behavior: the influence of follower characteristics

Research on leadership and subsequent follower outcomes has remained a prominent topic of study in the organizational sciences. Unfortunately, the leadership literature has neglected the role of follower characteristics as potential influences on the relationship between leader behavior and follower work behavior. In this session, we will review the literature on follower individual differences as they relate to leader effectiveness. We will also report the results of 2 studies that we conducted to further examine this issue. In the first study, we found that follower promotion focus mediated the relationship between transformational leadership and follower organizational citizenship behavior. In the second study, we found support for a moderated mediation model in which transformational leadership moderated the relationship between work ethic and work engagement, which subsequently predicted follower proactive behavior at work. We will conclude the session by discussing the implications of this area of research on the study and practice of leadership

Sparse regular subsets of the reals

This paper concerns the expansion of the real ordered additive group by a predicate for a subset of $[0,1]$ whose base-$r$ representations are recognized by a B\"uchi automaton. In the case that this predicate is closed, a dichotomy is established for when this expansion is interdefinable with the structure (\mathbb{R},1}. In the case that the closure of the predicate has Hausdorff dimension less than $1$, the dichotomy further characterizes these expansions of $(\mathbb{R},<,+,0,1)$ by when they have NIP and NTP$_2$, which is precisely when the closure of the predicate has Hausdorff dimension $0$.Comment: 25 page

Visualizing the One-Dimensional Diffusion of DNA Mismatch Repair Proteins at the Single-Molecule Level

The eukaryotic post-replicative DNA mismatch repair pathway corrects mispaired bases that escape polymerase-proofreading machinery during DNA synthesis before the errors become permanently embedded in the genome. The initial steps in this essential pathway involve a series of specific target searches along DNA by the protein complexes Msh2-Msh6 and Mlh1-Pms1 in order to locate and remove mispaired bases. The details of these critical processes remain poorly understood, largely due to a lack of experimental methods capable of probing these dynamic processes. A custom total internal reflection fluorescence microscopy assay was developed to investigate these events by visualizing the proteins as they search along DNA in real time at the single molecule level. Both Msh2-Msh6 and Mlh1-Pms1 were found to travel along DNA by means of a one-dimensional random walk driven by thermal energy; however, the results presented in this work also reveal distinct mechanisms of diffusion utilized by each complex. The observed diffusive behavior of Msh2-Msh6 is consistent with a model in which the protein forms a highly processive clamp that rotates about the DNA helical axis as it diffuses, thereby remaining in register with the phosphate backbone as it scans DNA for mispaired bases. Mlh1-Pms1 movements are more consistent with a loosely bound ring-like structure that moves along DNA by a hopping or stepping mechanism as it searches for mismatch-bound Msh2-Msh6. These assays provide critical novel insights into the initial steps of mismatch recognition, address long-debated models proposed for post-recognition events in mismatch repair and also provide a platform for studying the protein-protein interactions of Msh2-Msh6 with Mlh1-Pms1 following mismatch recognition. In addition to providing important details into the DNA repair pathway itself, the data also reveal distinct limitations different modes of diffusion may impose on DNA target searches in vivo and these results can be generalized to various other DNA-binding proteins that move along DNA by similar mechanisms. Importantly, this work also provides the first experimental evidence directly observing unbiased facilitated diffusion as a mechanism of target search and recognition by any protein. The manner by which DNA-binding proteins are able to survey a vast amount of nonspecific genomic DNA in order to recognize a small number of specific sites or structures is a fundamental issue in understanding a diverse array of protein-DNA processes such as replication, gene expression and DNA repair and the diversity of targets and necessary search mechanisms involved in the mismatch repair pathway make it an excellent model system for studying facilitated diffusion along DNA

Computational Sensitivity Investigation of Hydrogel Injection Characteristics for Myocardial Support

Biomaterial injection is a potential new therapy for augmenting ventricular mechanics after myocardial infarction (MI). Recent in vivo studies have demonstrated that hydrogel injections can mitigate the adverse remodeling due to MI. More importantly, the material properties of these injections influence the efficacy of the therapy. The goal of the current study is to explore the interrelated effects of injection stiffness and injection volume on diastolic ventricular wall stress and thickness. To achieve this, finite element models were constructed with different hydrogel injection volumes (150 µL and 300 µL), where the modulus was assessed over a range of 0.1 kPa to 100 kPa (based on experimental measurements). The results indicate that a larger injection volume and higher stiffness reduce diastolic myofiber stress the most, by maintaining the wall thickness during loading. Interestingly, the efficacy begins to taper after the hydrogel injection stiffness reaches a value of 50 kPa. This computational approach could be used in the future to evaluate the optimal properties of the hydrogel

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