Effect of pressure on the flow behavior of polybutene

The rheology of submicron thick polymer melt is examined under high normal pressure conditions by a recently developed photobleached‐fluorescence imaging velocimetry technique. In particular, the validity and limitation of Reynold equation solution, which suggests a linear through‐thickness velocity profile, is investigated. Polybutene (PB) is sheared between two surfaces in a point contact. The results presented in this work suggest the existence of a critical pressure below which the through‐thickness velocity profile is close to linear. At higher pressures however, the profile assumes a sigmoidal shape resembling partial plug flow. The departure of the sigmoidal profile from the linear profile increases with pressure, which is indicative of a second‐order phase/glass transition. The nature of the transition is confirmed independently by examining the pressure‐dependent dynamics of PB squeeze films. The critical pressure for flow profile transition varies with molecular weight, which is consistent with the pressure‐induced glass transition of polymer melt

The magazine´s journalistic construction Caras y Caretas in the repression of the "Semana Trágica" ("Tragic Week") in 1919

La revista Caras y Caretas, como publicación semanal de actualidad, estructuró un discurso acerca de los conflictos obreros durante la época radical (1916-1930), con las cuales ofreció su postura frente a las tensiones sociales y políticas de la época. En ese sentido, se indaga la construcción periodística de la publicación ante el reclamo de los sectores obreros en los hechos de la denominada Semana Trágica de 1919. La investigación toma para el análisis los aportes teórico-metodológicos de Roger Chartier, Miguel Rodrigo Alsina, Roberto Marafioti, Héctor Borrat, entre otros. Entre las conclusiones obtenidas, se demostró la posición del semanario como actor político de cara a los conflictos obreros y en el marco de las relaciones de dominio instituidas. Construyó un discurso que presentó realidades dicotómicas o pares antagónicos entre un “ellos” y un “nosotros”, los cuales además se diferenciaban por principios de superioridad e inferioridad y de la necesidad de asimilar o proscribir a quienes no encajaban en el orden establecido. A través de diversas estrategias discursivas, la revista legitimó prácticas represivas por parte de la policía, el Ejército y del sector parapolicial Liga Patriótica Argentina.The magazine Caras y Caretas, as a current weekly, lead a speech about the workers conflicts during the radical period (1916-1930), through which it offered it position against the social and political tensions of the epoch. In that sense, the publication ́s journalistic construction is inquired due to the workers sectors claims in what is known as “Semana Trágica” (“Tragic week”) in 1919. The research takes into account the theorical-methodological approaches for the analysis, as well as Roger Chartier, Miguel Rodrigo Alsina, Roberto Marafioti, Hector Borrat, among others. It was determined that journal position as a political actor face to the worker issues and with the power relations installed. It structured a speech that showed the dichotomous facts or antagonic pairs between “them” and “us”, who were also distinguised by superiority and inferiority principles and the need of setting aside to the ones that did not fit in the status quo. Through the different discursive strategies, the magazine legitimized repressive practices of the police, the Army and the parapolicial sector Liga Patriótica Argentina (Argentine Patriotic League)

End-colostomy diverticulitis with parastomal phlegmon: A case report.

Acute colonic diverticulitis is a well-known surgical emergency, which occurs in about 10 percent of patients known for diverticulosis. The case of a 77-year-old woman is reported, with past history of abdominoperineal resection with end-colostomy for low rectal adenocarcinoma, and who developed an acute colonic diverticulitis in a subcutaneous portion of colostomy with parastomal phlegmon. Initial computed tomography imaging demonstrated a significant submucosal parietal edema with local fat tissues infiltration in regard of 3 diverticula. A two-step treatment was decided: first a nonoperative treatment was initiated with 2 weeks antibiotics administration, followed by, 6 weeks after, a segmental resection of the terminal portion of the colon with redo of a new colostomy by direct open approach. Patient was discharged on the second postoperative day without complications. Follow-up at 2 weeks revealed centimetric dehiscence of the stoma, which was managed conservatively until sixth postoperative week by stomatherapists. Treatment of acute diverticulitis with parastomal phlegmon in a patient with end-colostomy could primary be nonoperative. Delayed surgical treatment with segmental colonic resection was proposed to avoid recurrence and potential associated complications

Heat transfer and turbulent heat flux budgets in cooling films

Statistics from large-eddy-simulation (LES) of cooling films with different cooling holes are used to evaluate budgets in the transport equation of turbulent heat flux. The capability of LES has been assessed by comparing simulated results with experimental data, while the correctness of the procedure generating turbulent heat flux budgets has been examined on a turbulent boundary layer. The mechanism of heat transfer has been preliminarily studied throughout the three-dimensional flow field at different blowing ratios using a general outer scaling, to recognize specific regions with corresponding heat transfer patterns. A compressible version of budget terms in the transport equation of turbulent heat flux is then explored to show the thermal behavior of flow downstream from the cooling film holes. Characteristics of each budget term are presented in a defect scaling consistent with the scaling suitable for Reynolds stresses and Reynolds stress budgets. Furthermore, these budget terms are compared among an array of different cooling hole shapes combined with different blowing ratios to explore self-similarity. Results show that the dynamic balance of all budget terms is significantly influenced by the cooling hole shape, while each turbulent heat flux budget term may scale with the velocity defect, temperature deficit, and the normalized streamwise distance to the power of an exponent dependent on the hole shape

Generating high-efficiency swimming kinematics using hydrodynamic eigenmode decomposition

This paper explores the use of hydrodynamic eigenmode decomposition as a means of generating optimal swimming kinematics of slender three-dimensional bodies. The eigenvectors of the unsteady hydrodynamic system are used as basis functions for the response to external forcing, such as perturbations generated by the deformation of the body. Exploiting the orthogonality of the modes, we show that swimming according to a single appropriately selected hydrodynamic eigenmode results in high-efficiency swimming. To demonstrate this result, we use an inviscid three-dimensional vortex lattice model to investigate the hydrodynamic eigenmodes of a selection of geometries. We find that for all of the body geometries tested, hydrodynamic efficiency far exceeding that of pure heaving or pitching can be achieved. All eigenmodes tested produce high-efficiency motion, as long as the beat frequency is higher than the mode's “cut-in” frequency for thrust generation. The eigenmodes show qualitative similarity to swimming patterns observed in nature and also correspond well to the existing classifications of undulatory and oscillatory swimming. This study demonstrates that the hydrodynamic eigenmode analysis can generate high-efficiency swimming kinematics based only on information about the body and wake geometry, and as such, this method has significant potential for further development and application to autonomous underwater vehicle design

The complete 1/N expansion of colored tensor models in arbitrary dimension

In this paper we generalize the results of [1,2] and derive the full 1/N expansion of colored tensor models in arbitrary dimensions. We detail the expansion for the independent identically distributed model and the topological Boulatov Ooguri model

Structure of Amphiphilic Terpolymer Raspberry Vesicles

Terpolymer raspberry vesicles contain domains of different chemical affinities. They are potential candidates as multi-compartment cargo carriers. Their efficacy depends on their stability and load capacity. Using a model star terpolymer system in an aqueous solution, a dissipative particle dynamic (DPD) simulation is employed to investigate how equilibrium aggregate structures are affected by polymer concentration and pairwise interaction energy in a solution. It is shown that a critical mass of polymer is necessary for vesicle formation. The free energy of the equilibrium aggregates are calculated and the results show that the transition from micelles to vesicles is governed by the interactions between the longest solvophobic block and the solvent. In addition, the ability of vesicles to encapsulate solvent is assessed. It is found that reducing the interaction energy favours solvent encapsulation, although solvent molecules can permeate through the vesicle’s shell when repulsive interactions among monomers are low. Thus, one can optimize the loading capacity and the release rate of the vesicles by turning pairwise interaction energies of the polymer and the solvent. The ability to predict and control these aspects of the vesicles is an essential step towards designing vesicles for specific purposes

Small bowel obstruction caused by a fast-growing desmoid tumor.

Desmoid tumors are rare tumors which can cause intestinal obstructions. Surgical wide excision is currently the treatment of choice, with the goal of achieving free resection margins

Encoding simplicial quantum geometry in group field theories

We show that a new symmetry requirement on the GFT field, in the context of an extended GFT formalism, involving both Lie algebra and group elements, leads, in 3d, to Feynman amplitudes with a simplicial path integral form based on the Regge action, to a proper relation between the discrete connection and the triad vectors appearing in it, and to a much more satisfactory and transparent encoding of simplicial geometry already at the level of the GFT action.Comment: 15 pages, 2 figures, RevTeX, references adde

Radical guide vane design and optimization

Turbofan engines are connected to the airframe by a pylon that crosses the bypass duct downstream of the fan. The presence of the pylon generates a potential field that influences the upstream flowfield. Distortion generated by the pylon can be detrimental to the fan stability and integrity, and as such it must be controlled. This work presents a new method for the two-dimensional design of fan outlet guide vane cascades in the presence of the potential flow distortion caused by the pylon. The method, based on surface singularities, is capable of mitigating the distortion while preserving the performance of the nominal cascade. Design targets are achieved by manipulating both airfoil geometry and position within the cascade. Because the distortions caused by the pylon obey essentially inviscid fluid mechanics, the variation in load and loss parameters across the cascade can be approximated surprisingly well with a singularity method. The design rationale of controlling the incompressible load distribution leads to cascades with uniform load and loss even when viscous and compressible effects are considered using high-fidelity computational fluid dynamics. The new approach provides a significant speed-up over methods based on computational fluid dynamics and is valuable as an initial design tool