From interparticle interactions to emergent behavior of smart fluids

Functional nano or microparticles in solution can form stimuli-responsive smart fluids that exhibit drastic property changes in the presence of magnetic or electric fields that originate from the interparticle interactions. For example, the most commonly utilized type of particle-based smart fluid are magnetorheological fluids (MRF) that contain ferromagnetic microparticles that allow them to reversibly solidify when they experience a magnetic field. The tunable nature of these materials not only make them useful in a variety of industries, but also make them a versatile system in which to study the influence of interparticle interactions on emergent behaviors. In this dissertation, we explore methods for tuning interparticle interactions with applied fields, additives, and functionalized particles and develop, through both experimentation and modeling, design rules for realizing new classes of smart fluids. First, we address a common limitation on the performance of MRF, namely slip failure, through the use of a shear-thickening additive to reinforce MRF particle chains as slip begins. Through flow- and oscillation-mode rheology, we find that a shear-thickening MRF has 60% higher yield stress than a conventional shear-thinning MRF. The shear-thickening additive allows us to affect the microstructure of the fluid in order to increase bulk performance by changing its failure mode. Next, we explore the hypothesis that highly anisotropic 2D sheets can reinforce conventional MRF as an additive by supporting the particle chains. Interestingly, the 2D sheets affect the performance of the fluid minimally in a boundary-driven flow because of the alignment of the sheets in the fluid velocity profile. However, we find that the 2D sheets increase MRF performance in pressure-driven flows by up to 45%. We determine through modeling that this performance improvement stems from the anisotropic sheets physically reinforcing the particle chains. This work has consequences for the design of MRF for applications using pressure-driven flows, such as soft robotics. In addition to studying the additives as a path to strengthening MRF, we investigate whether the magnetic particles themselves can be modified to chemically adhere to one another, thus providing additional attractive forces to supplement the magnetic force between particles. Using flow- and oscillation-mode rheology, we quantify the performance using both the yield stress and chain stiffness as performance metrics. By developing two different adhesive MRF, we find that linked chains exhibit a 40% increase in yield stress and a 100% increase in stiffness. Using thymine-functionalized particles, we present a dynamic method for linking particles in an MRF for increased performance. Finally, a system of polarizable nanoparticles is investigated after it is observed to exhibit a macroscopic cellular phase with particle-poor voids and particle-rich walls in a fluid cell when applying an AC and DC field. By tuning the applied AC and DC fields, we identify the conditions necessary for the phase transition using fluorescence microscopy. We also find through Cahn-Hilliard analysis and additional experiments that the cellular phase is the result of various types of electrically-induced interactions. Specifically, electrophoresis causes the particles to accumulate on one electrode, then electroosmotic and electrohydrodynamic flows occur and exert attractive and repulsive forces on the particles. When the electrohydrodynamic flow dominates, voids nucleate at high field regions at which point spinodal decomposition into the cellular phase occurs. This understanding allows us to explore ways to tune this behavior such as using photolithography to control the location of the voids, and thus the structure of the material

Recycling manure as cow bedding: potential benefits and risks for UK dairy farms

Material obtained from physical separation of slurry (recycled manure solids; RMS) has been used as bedding for dairy cows in dry climates in the US since the 1970s. Relatively recently, the technical ability to produce drier material has led to adoption of the practice in Europe under different climatic conditions. This review collates the evidence available on benefits and risks of using RMS bedding on dairy farms, with a European context in mind. There was less evidence than expected for anecdotal claims of improved cow comfort. Among animal health risks, only udder health has received appreciable attention. There are some circumstantial reports of difficulties of maintaining udder health on RMS, but no large scale or long term studies of effects on clinical and subclinical mastitis have been published. Existing reports do not give consistent evidence of inevitable problems, nor is there any information on clinical implications for other diseases. The scientific basis for guidelines on management of RMS bedding is limited. Decisions on optimum treatment and management may present conflicts between control of different groups of organisms. There is no information on the influence that such 'recycling' of manure may have on pathogen virulence. The possibility of influence on genetic material conveying antimicrobial resistance is a concern, but little understood. Should UK or other non-US farmers adopt RMS, they are advised to do so with caution, apply the required strategies for risk mitigation, maintain strict hygiene of bed management and milking practices and closely monitor the effects on herd health

Identification of Sling Systems in High Economy and Low Economy Runners

Background and Purpose: Human locomotion requires characteristic muscle activation timing patterns that work in a defined fashion along a kinetic chain. Sling systems are chains of muscles and innervating fascia that facilitate sequential muscle activation patterns during movement. The purpose of this study was to examine four sling systems across a running gait cycle and to determine how they might differ between runners with high and low running economy. Participants: Twenty-five recreational runners (11M, 14F, height = 1.73 ± .07 m, mass = 70.3 ± 11.7 kg, age = 28.6 ± 5.1 years) completed this study. Methods: Recreational runners completed a running economy test and were classified as high economy or low economy based on published normative data. On a separate testing day, runners completed overground running trials at a 10-km race pace and slow running pace. Surface electromyography was used to measure muscle activation during run trials for four sling systems: the Posterior Oblique Sling (POS: gluteus maximus and contralateral latissimus dorsi), the Anterior Oblique Sling (AOS: external oblique and contralateral adductors), the Lateral Sling (LAT: gluteus medius, tensor fascia latae (TFL), and contralateral quadratus lumborum (QL)), and the Deep Longitudinal Sling (LONG: tibialis anterior (TA), peroneus longus, biceps femoris (BF), multifidus, and erector spinae (ES)). Mixed-Design ANOVAs were conducted to determine differences among sling systems and between groups in muscle onset time (EMGonset), muscle offset time (EMGoffset), peak amplitude (EMGamp), and time of peak amplitude (EMGpeak). Peak times and amplitudes for the muscles of the AOS could not be established as these muscles displayed nearly constant activation throughout the gait cycle. Results: Significant main effects were observed in the POS, LONG, and LAT at both the 10-km race pace and slow running pace for EMGonset, EMGoffset, EMGpeak, and EMGamp. Differences between high economy and low economy runners were observed for ES EMGonset Burst 3, ES EMGpeak Burst 3, ES EMGamp Burst 3,BF EMGonset Burst 1, BF EMGpeak Burst 1, BF EMGoffset Burst 2, BF EMGpeak Burst 2, BF EMGpeak Burst 3, BF EMGamp Burst 1, and TA EMGpeak at the slow running speed. At the 10-km race pace, differences between high economy and low economy runners were observed for TFL EMGonset Burst 2, QL EMGoffset Burst 1, QL EMGpeak Burst 2, and QL EMGonset Burst 3. Discussion and Conclusion: Muscles in the POS, LAT, and LONG work in defined sequential and synchronous patterns across the gait cycle with significant variability between high economy and low economy runners.</p

Inteligencia emocional y rendimiento académico en adolescentes entre 16 a 18 años de edad

Resumen: En la presente investigación se tuvo como objetivo principal descubrir la relación existente entre la inteligencia emocional y el rendimiento académico y las diferencias según el sexo en adolescentes de 16 a 18 años de edad. Los cuales asisten a escuelas públicas y privadas de gestión estatal en la ciudad de Paraná, Entre Ríos. La muestra estuvo integrada por 156 adolescentes de ambos sexos: 50 varones y 106 mujeres. Es una investigación que puede clasificarse como un estudio cuantitativo, con un diseño descriptivo- correlacional, de corte transversal y de campo. Para obtener información acerca de las variables se administró el Trait Meta Mood Scale (TMMS-24 de Salovey y cols, 1995) con una adaptación de Fernández, Berrocal y otros (2004), para medir la inteligencia emocional. Por otra parte, para evaluar el rendimiento académico se realizó un promedio general de las asignaturas de cada alumno, en el trimestre donde fue aplicada la escala de inteligencia emocional. De acuerdo a los resultados obtenidos, se concluyó que no se encontró una correlación significativa entre inteligencia emocional y rendimiento académico en los adolescentes de 16 a 18 años de edad de la ciudad de Paraná. En relación a la diferencia entre sexos se halló que los hombres presentan más desarrollada la comprensión emocional que las mujeres. Por otro lado, si bien no se observaron resultados estadísticamente significativos, se encontró que las mujeres presentan más desarrollada la percepción emocional que los hombres. Finalmente, pese a que las hipótesis planteadas no se corroboraron, hay que tener en cuenta la importancia de la educación emocional en las escuelas, ya que es fundamental para el pleno desarrollo de la personalidad integral del alumnado. Así mismo, se considera valioso poder poner énfasis en la formación tanto académica como emocional en los adolescentes, considerando la importancia que tienen las emociones en esta etapa del desarrollo