Describing the Flow Curve of Shear-Banding Fluids Through a Structural Minimal Model

Main characteristics of colloidal systems that develop fluid phases with different mechanical properties, namely shear-banding fluids, are briefly reviewed both from experimental and theoretical (modelling) point of view. A non-monotonic shear stress vs. shear rate constitutive relation is presented. This relation derives from a phenomenological model of a shear ratedependent viscosity describing structural changes and involves the possibility of multivalued shear rates under a given shear stress. In the case of a stress-dependent viscosity, the same model allows one to predict vorticity banding. Predictions of this model under controlled stress are discussed, namely occurrence of a kind of top- and bottom-jumping of the shear rate in response to stress increasing-decreasing. Applying this model to evaluation of the flow curve of such colloidal systems is performed. Particular emphasis is placed on the adequate computation of the shear rate function in cylindrical Couette cells in order to handle the corresponding flow curve which exhibits the well-known shear stress plateau. Indeed, as different fluid phases coexist in the flow domain, measured (torque vs. angular velocity) data cannot be directly converted into rheometric (shear stress vs. shear rate) functions. As the lacking non-local terms in the model prevents the direct determination of the stress-plateau, this value is included as an adjustable parameter. Thus model predictions satisfactorily match up experimental data of wormlike micellar solutions from the literature.Comment: 22 pages, 9 fi

On the Flow Curve of Colloids Presenting Shear-Induced Phase Transitions

This work deals with the evaluation of the flow curve of colloidal systems that develop fluid phases with different mechanical properties, namely shear-banding fluids. The problem involved is that, as different fluid phases coexist in the flow domain of the rheometric cell, measured data cannot be directly converted into rheometric functions. In order to handle this problem, a shear stress vs. shear rate constitutive relation is introduced to interpret the steady state flow curves. The relation derives from a phenomenological description of structural changes, and involves the possibility of multivalued shear rates under a given shear stress. Numerical predictions satisfactorily match up to experimental data of wormlike micellar solutions. A crucial aspect is the adequate computation of the shear rate function from raw data measured in the rheometric cell.Comment: 12 page

From Team Huddle to Team Cuddle: Rekindling Caring, Self-Compassion, and Joy in Work!

Problem: The healthcare industry suffers from a high level of burnout and unhealthy work environments, which has been heightened by the COVID-19 pandemic. The consequences of burnout may be expressed in both individuals and teams as a lack of caring, disengagement, incivility, and staff turnover. Context: One department in an integrated healthcare organization displayed a pattern of annual low employee engagement scores and alleged workplace bullying. Team members also observed that employees failed to speak up when experiencing incivility. The Clinical Nurse Leader (CNL) student determined that an improvement initiative was needed to create a culture of caring to improve team cohesion and resilience and potentially reduce burnout and prevent incivility. As described by Watson (2012) and Perlo et al. (2017), healthy work environments include intentional change behaviors that promote mutual caring, positive values, trustworthiness, loving-kindness, and self-reflection. Intervention: To improve the team dynamics and vitality, a new 13-week program (From Team Huddle to Team Cuddle, a.k.a. Team Cuddles) was created and implemented. The Team Cuddles program was guided by evidence-based practices to cultivate a positive work environment and culture of caring to support individuals and the team. Each weekly session included Caring Science practices and HeartMath exercises. Measures: Quantitative and qualitative measures were assessed. The primary outcome measures included overall employee attendance and engagement. The process measures evaluated participation, engagement, and improvement in several multi-dimensional surveys. Qualitative themes were captured through direct observation and open-ended survey questions during implementation. Results: The improvement project recruited 18 volunteer team members to participate. The pre-intervention survey response rate was low (16%); however, there was a significant increase to 50% in the post-intervention surveys. The final survey results showed a high degree of improvement in caring, team cohesion, and to connect with others; in alignment with some of the common themes observed. A majority of responders wanted the program to continue. Conclusions: Leadership must pay close attention to the signs and symptoms of burnout at all levels of the organization to foster healthy work environments. Creating and sustaining a culture of caring is multifaceted and requires leadership support. Team interventions that are intentionally implemented and based on evidence from Caring Science are vital. When team huddles are transformed into team cuddles, they should improve employee resilience, self-compassion, and joy in work

Food safety and GM crops implications for developing-country research

"In the developing world the approval and cultivation of genetically modified (GM) crops is largely limited to the commercial production of insect-resistant cotton in Argentina, China, India, Mexico, and South Africa.... Approvals of GM crops used for food or feed lag far behind cotton... This gap in approvals is unfortunate, because crop biotechnology, appropriately applied, has the potential to address key production constraints affecting resource-poor farmers. Currently, important public- and private-sector research is underway to help meet the productivity needs of these farmers." from TextFood safety ,food security ,Public health ,

On the Viscosity of Concentrated Suspensions of Charged Colloids

This work is concerned with the theoretical estimation of the low-shear viscosity of concentrated suspensions of charged-stabilized latex particles. Calculations are based on the assumption that particles interacting through purely repulsive potentials behave as equivalent hard-spheres (HS), and suspension viscosity may be analyzed in the framework of HS systems. In order to predict numerically the HS radius, the pair potential due to double-layer interaction, as a function of particle concentration, was investigated by using Poisson-Boltzmann theory and the cell model. Calculations explain appropriately experimental data for a wide range of particle sizes, volume fractions and salt concentrations. The problem concerning the effective surface charge of latex particles is also discussed.Fil: Berli, Claudio Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Deiber, Julio Alcides. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Quemada, Daniel. Universite Paris VII; Franci

La influencia de los chaebols en la economía coreana

Estudio de la realidad económica de Corea del Sur desde la finalización de la colonización japonesa hasta nuestros días. Entrando, de esta manera, en el análisis del concepto chaebol, sus orígenes y características principales, destacando su particular modelo de gestión y su principal estrategia de expansión y hablando de los chaebols más representativos.Grado en Comerci

Cinquanta-dos anys després

La lluita pel control del càncer des de la perspectiva actual i futura de la medicin