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

Étude des mécanismes de régulation de l’épissage alternatif

L’épissage alternatif est un processus finement régulé qui permet de générer une grande variété d’ARNm. Il est l’une des sources de la diversité du protéome. Il permet ainsi de produire, à partir d’un nombre limité de gènes, une multitude de protéines avec des fonctions différentes et même antagonistes. De plus, il a un rôle dans des processus cellulaires importants tels que l’apoptose, la prolifération, la différenciation, la migration et la survie dans des conditions de stress. Les conséquences de la dérégulation de l’épissage alternatif sont critiques et peuvent entraîner des défauts reliés à de nombreuses maladies comme le cancer. De plus, ces perturbations vont souvent toucher l’épissage alternatif des gènes apoptotiques. Au vu de son rôle crucial dans le processus de l’apoptose, le gène Bcl-x a été l’objet d’une grande attention depuis de nombreuses années. Ce gène donne deux variants pro- et anti-apoptotique: Bcl-xS et Bcl-xL. Dans notre laboratoire, l’étude de Bcl-x a permis d’entrevoir les mécanismes par lesquels le choix entre les deux isoformes est déterminé et de découvrir plusieurs facteurs et éléments d’épissage impliqués. Dans ce travail, nous avons poursuivi ces recherches avec trois approches pour tenter d’approfondir les connaissances sur l’épissage alternatif. Dans une première partie, l’idée a été de comprendre la mécanique combinatoire entre des facteurs d’épissage dans la régulation d’un site en partant de l’exemple de Bcl-x. Ainsi les séquences de liaison de 4 protéines (RNPS1, eIF4A3, hnRNP K et hnRNP F/H) ont été insérés autour d’un site d’épissage dans un minigène pour ensuite effectuer des essais d’épissages in vitro et in vivo. L’objectif est ainsi de pouvoir créer une base de données indiquant pour une combinaison de protéine l’impact sur l’épissage. Nous avons observé que ce système fonctionne puisque les insertions modulent l’épissage mais que les changements diffèrent selon l’essai. De plus, les résultats obtenus ne correspondent pas à ceux observés avec Bcl-x, indiquant ainsi que le modèle proposé a ses limites et qu’il reste à améliorer. Dans la deuxième partie, nous avons étudié l’impact de deux drogues (oxaliplatin et staurosporine) sur 57 événements d’épissage alternatif dans les trois lignées cellulaires HEK293, HCT116 et HIEC. Le but étant d’étudier à quels niveaux ces drogues affectent l’épissage et de voir si les effets différents observés avec les drogues entre lignée cellulaire pour Bcl-x pouvaient se retrouver pour d’autres événements et avec d’autres lignées. À la suite du traitement à la staurosporine, aucun événement en commun n’a été identifié entre les trois lignées. Avec l’oxaliplatin, nous avons isolé quatre événements d’épissage modulés, soit Bclx, AURKA, INCENP et PPP3CB. Ces derniers sont affectés de la même manière entre les lignées mais avec des amplitudes différentes. Aussi, INCENP a été le seul affecté presque partout, sauf dans les cellules HIEC traitées à la staurosporine. Finalement, dans une dernière partie, nous nous sommes penchés sur les relations entre l’épissage alternatif des 57 événements précédents et la chromatine. Nous avons testé 14 composés affectant l’état de la chromatine en traitant ou non avec l’oxaliplatin. L’hypothèse a été que ces composés pouvaient affecter les événements et modifier l’effet de l’oxaliplatin permettant ainsi d’améliorer notre connaissance sur son action. Aucun effet important n’a été observé avec les composés utilisés seuls. En revanche, avec l’oxaliplatin, certains composés augmentent son effet sur l’épissage (JQ1 et BAY-850) et d’autres le diminuent (GSK8814, BAZ2 et SGCBP30). À terme, ce projet contribue à l’ensemble de travaux ayant pour but d’améliorer les traitements anticancéreux en tentant de les rendre plus spécifiques. En effet, grâce à une meilleure connaissance des facteurs impliqués dans chaque cancer, il sera possible de mieux les cibler

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

Interactive Effects of Body Position and Perceived Exertion During Spinning Exercises

ABSTRACTRendos, NK, Musto, AA, and Signorile, JF. Interactive effects of body position and perceived exertion during Spinning exercises. J Strength Cond Res 29(3)692–699, 2015—Spinning is a popular group exercise taught in health and fitness facilities worldwide. Throughout a Spinning workout session, intensity is variable and is controlled by body position on the Spinning stationary cycle and perceived resistance. This study examined the effects of 3 body positions and 4 levels of perceived exertion (RPE) on cardiorespiratory response and vastus lateralis normalized electromyographical activity (NrmsEMGVL). Eleven participants (24.4 ± 6.3 years) with 3.2 ± 2.2 years of Spinning experience completed twelve 3-minute randomly assigned Spinning conditions across 4 separate testing days after an 8-hour fast. Conditions were determined by body position (seated, running, and standing climb [SC]) and RPE (low, low-medium, medium-high, and high). Cardiorespiratory data and NrmsEMGVL were recorded continuously during each Spinning condition. Respiratory rate and oxygen consumption were significantly higher for running and SC than seated, and minute ventilation was significantly higher for running than seated. All cardiorespiratory values were higher at medium-high and high RPE, than low or medium-low RPE, and high RPE generated higher respiratory rate and respiratory exchange ratio than medium-high RPE. Significant body position × RPE interactions were observed for heart rate (HR) and NrmsEMGVL with running and SC producing higher HRs than seated at low and high RPE, and running producing higher NrmsEMGVL than seated at low RPE. Results indicate that running and SC provide the greatest cardiorespiratory responses, and maximal efforts are not needed for these responses. Additionally, HR seems to be a poor marker of oxygen consumption, especially at high RPEs

PHASE-SPECIFIC FORCE AND TIME METRICS OF VERTICAL HOPPING IN CHRONIC ANKLE INSTABILITY

Nicole K. Rendos1, Jeffrey D. Simpson2, Hoon Kim3, John R. Harry4. 1Emory University, Atlanta, GA. 2University of West Florida, Pensacola, FL. 3University of North Carolina at Chapel Hill, Chapel Hill, NC. 4Texas Tech University, Lubbock, TX. BACKGROUND: Single limb hopping tests are used to identify motor-behavioral impairments of the lower limb that are associated with chronic ankle instability (CAI) but are often limited by performance-based metrics. This study compared phase-specific force and time metrics during single limb vertical hopping in participants with and without CAI. METHODS: Twenty-five participants with self-reported CAI (13M, 12F; age: 24±3y; height: 168.3±12.9cm; mass: 72.2±15.2kg) and 25 controls (13M, 12F; age: 25±4y; height: 172.5±6.1cm; mass: 70.8±9.7kg) completed the study. A total of 3 trials consisting of 5 consecutive single limb vertical hops were completed on a force platform. Individuals with CAI performed the hopping task on their affected limb while controls used their preferred limb. Eccentric and concentric phases were identified for each vertical hop from vertical ground reaction force data and the middle 3 hops were analyzed. Peak vertical force, time to peak vertical force, vertical impulse, and phase time were obtained for eccentric and concentric phases and compared between groups with an unpaired t-test (p \u3c 0.05) and Cohen’s D effect sizes (d). RESULTS: Concentric phase time (p=0.041; CAI: 0.23±0.09s vs. Control: 0.19±0.0s; d=0.53) and time to peak concentric vertical force (p=0.020; CAI: 0.08±0.19s vs. Control: 0.03±0.02; d=0.71) were significantly longer in the CAI group with moderate-magnitude differences. While not significant (p=0.066), a moderate-magnitude difference (d=0.45) was observed for concentric vertical impulse between CAI (3.04± 0.56 Ns/kg) and controls (3.40± 0.91 Ns/kg). CONCLUSION: Individuals with CAI demonstrated difficulty transitioning from eccentric to concentric phases, which could reveal a less efficient transfer of lower limb mechanical output from the affected limb during repetitive vertical hopping

SINGLE-SUBJECT ANALYSIS OF PHASE-SPECIFIC FORCE AND TIME VARIABLES DURING VERTICAL HOPPING IN CHRONIC ANKLE INSTABILITY

Jeffrey Simpson1, Nicole Rendos2, Hoon Kim3, John Harry4. 1University of West Florida, Pensacola, FL. 2Emory University, Atlanta, GA. 3University of North Carolina-Chapel Hill, Chapel Hill, NC. 4Texas Tech University, Lubbock, TX. BACKGROUND: Altered lower limb movement dynamics are associated with chronic ankle instability (CAI), but are often presumed by the homogeneity of CAI cohorts with aggregate group comparisons. Single-subject analyses could reveal unique patient-specific movement adaptations within a heterogeneous cohort of CAI in which aggregate group analyses might identify null findings. This study compared phase-specific force and time variables during single limb vertical hopping in participants with and without CAI using a single-subject analysis approach. METHODS: Individuals with CAI (n=25; 13M, 12F; age: 24±3y; height: 168.3±12.9cm; mass: 72.2±15.2kg) and matched controls (n=25; 13M, 12F; age: 25±4y; height: 172.5±6.1cm; mass: 70.8±9.7kg) completed 3 trials of 5 consecutive single limb vertical hops on a force platform. Participants with CAI completed the hopping task on the affected limb and matched controls used their preferred limb. Vertical ground reaction force data was used to identify eccentric and propulsion phases for the middle 3 hops of each trial (e.g. 9 total hops analyzed). Peak force, time to peak force, and phase time were computed for eccentric and propulsion phases. The Model Statistic procedure (α=0.05) and Cohen’s D effect sizes (d) was used to test for significant differences between each participant with CAI to an aggregate group mean of the control group. RESULTS: A total of 10 CAI participants exhibited less peak propulsive force (CAIrange: 15.16-21.07 N/kg; mean difference: 4.38±1.99 N/kg; d=0.80-3.39), 8 CAI participants displayed longer time to peak propulsive force (CAIrange: 0.06-0.43 s; mean difference: 0.11±0.05 s; d=1.58-8.03) and longer propulsion phase time (CAIrange: 0.22-0.56 s; mean difference: 0.15±0.12 s; d=0.82-4.21) compared to controls. Additionally, 10 CAI participants displayed less time to peak eccentric force (CAIrange: 0.07-0.11 s; mean difference: 0.04±0.02 s; d=1.00-2.91) than controls. CONCLUSION: Individuals with CAI displayed differences during the propulsion phase of repetitive hopping on the affected limb. This single-subject analysis approach could help further understand patient-specific impairments associated with CAI during dynamic tasks