Capillary Forces in Partially Saturated Thin Fibrous Media

Capillarity is often exploited in self-cleaning, drag reducing and fluid absorption/storage (sanitary products) purposes just to name a few. Formulating the underlying physics of capillarity helps future design and development of optimized structures. This work reports on developing computational models to quantify the capillary pressure and capillary forces on the fibrous surfaces. To this end, the current study utilizes a novel mass-spring-damper approach to incorporate the mechanical properties of the fibers in generating virtual fibrous structures that can best represent fibrous membranes. Such virtual fibrous structures are then subjected to a pressure estimation model, developed for the first time in this work, to estimate the liquid entry pressure (LEP) for a hydrophobic fibrous membrane. As for accurate prediction (and not just estimation) of the capillary pressure, this work also presents an energy minimization method, implemented in the Surface Evolver code, for tracking the air–water interface intrusion in a hydrophobic fibrous membrane comprised of orthogonally oriented fibers. This novel interface tracking algorithm is used to investigate the effects of the membrane’s microstructure and wetting properties on its resistance to water intrusion (i.e., LEP). The simulation method developed in this work is computationally affordable and it is accurate in its predictions of the air–water interface shape and position inside the membrane as a function of pressure. Application of the simulation method in studying effects of fiber diameter or contact angle heterogeneity on water intrusion pressure is reported for demonstration purposes. Capillary forces between fibrous surfaces are also studied experimentally and numerically via the liquid bridge between two parallel plates coated with electrospun fibers. In the experiment, a droplet was placed on one of the polystyrene- or polyurethane-coated plates and then compressed, stretched, or sheared using the other plate and the force was measured using a sensitive scale. In the simulation, the liquid bridge was mathematically defined for the Surface Evolver finite element code to predict its 3-D shape and resistance to normal and shearing forces, respectively, in presence of the contact angle hysteresis effect. Despite the inherent non-uniformity of the fibrous surfaces used in the experiments and the simplifying assumptions considered for the simulations, reasonable agreement was observed between the experiments and simulations. Results reveal that both normal and shear force on the plates increase by increasing the liquid volume, or decreasing the spacing between the plates

A Mathematical Simulation of the Ureter: Effects of the Model Parameters on Ureteral Pressure/Flow Relations

Ureteral peristaltic mechanism facilitates urine transport from the kidney to the bladder. Numerical analysis of the peristaltic flow in the ureter aims to further our understanding of the reflux phenomenon and other ureteral abnormalities. Fluid-structure interaction (FSI) plays an important role in accuracy of this approach and the arbitrary Lagrangian–Eulerian (ALE) formulation is a strong method to analyze the coupled fluid-structure interaction between the compliant wall and the surrounding fluid. This formulation, however, was not used in previous studies of peristalsis in living organisms. In the present investigation, a numerical simulation is introduced and solved through ALE formulation to perform the ureteral flow and stress analysis. The incompressible Navier–Stokes equations are used as the governing equations for the fluid, and a linear elastic model is utilized for the compliant wall. The wall stimulation is modeled by nonlinear contact analysis using a rigid contact surface since an appropriate model for simulation of ureteral peristalsis needs to contain cell-to-cell wall stimulation. In contrast to previous studies, the wall displacements are not predetermined in the presented model of this finite-length compliant tube, neither the peristalsis needs to be periodic. Moreover, the temporal changes of ureteral wall intraluminal shear stress during peristalsis are included in our study. Iterative computing of two-way coupling is used to solve the governing equations. Two phases of nonperistaltic and peristaltic transport of urine in the ureter are discussed. Results are obtained following an analysis of the effects of the ureteral wall compliance, the pressure difference between the ureteral inlet and outlet, the maximum height of the contraction wave, the contraction wave velocity, and the number of contraction waves on the ureteral outlet flow. The results indicate that the proximal part of the ureter is prone to a higher shear stress during peristalsis compared with its middle and distal parts. It is also shown that the peristalsis is more efficient as the maximum height of the contraction wave increases. Finally, it is concluded that improper function of ureteropelvic junction results in the passage of part of urine back flow even in the case of slow start-up of the peristaltic contraction wave

Cutaneous Metastatic Undifferentiated Carcinoma to the Mandibular Gingiva: A Rare Case Report

Objectives Metastasis to the oral cavity is a rare phenomenon. Basal cell carcinoma (BCC) is the most common skin malignancy, followed by squamous cell carcinoma (SCC) and melanoma. Nevertheless, BCC rarely metastasizes, and most cases of cutaneous metastasis to the oral cavity include melanoma and SCC. Oral metastatic lesions are not typical differential diagnoses and may cause diagnostic challenges. Case In this paper, we present the case of a 36-year-old female patient with a rapidly growing gingival mass. She had a history of undifferentiated skin carcinoma almost 18 months ago. An incisional biopsy was performed, and according to microscopic findings and medical history, a diagnosis of undifferentiated metastatic carcinoma was made. Conclusion Oral metastasis needs to be considered in the differential diagnosis of lesions in patients with a history of malignancy

Preparation and characterization of new hybrid organic/inorganic systems derived from calcium (aminoalkyl)-phosphonates and -phosphonocarboxylates

We have studied the phenomenon of calcium complexation by lab synthesized amphiphilic (α-aminoalkyl)-phosphonocarboxylic or -phosphonic acids. The electrical conductivity of aqueous solutions of sodium salts of all these acids was measured versus the volume of a calcium salt solution added. It appeared that calcium complexes are formed in a Ca/P atomic ratio close to 1. Calcium phosphonocarboxylates and calcium phosphonates were also precipitated by mixing aqueous solutions of disodium salts of phosphorus amphiphiles and calcium nitrate solutions. Before chemical analysis, these complexes were calcined to remove the organic part. In the mineralized products, calcium and phosphate were assayed: the Ca/P atomic ratio was equal to 1. X-ray diffraction and IR spectroscopy showed that they are made entirely of β pyrophosphate (Ca2P2O7), a result in agreement with previous chemical analysis. The chemical formula of the starting calcium complexes could be written as CaL·2H2O (L= ligand). The SEM micrographs of these complexes show plate-like structures. XRD patterns are characteristic of layered structures. These facts suggest that calcium complexes are composed of alternating bimolecular layers of calcium alkylphosphonocarboxylates or calcium alkylphosphonates, the chains being tilted and partially interdigitated

Slopey quantizers are locally optimal for Witsenhausen's counterexample

We study the perfect Bayesian equilibria of a leader-follower game of incomplete information. The follower makes a noisy observation of the leader's action (who moves first) and chooses an action minimizing her expected deviation from the leader's action. Knowing this, leader who observes the realization of the state, chooses an action that minimizes her distance to the state of the world and the ex-ante expected deviation from the follower's action. We show the existence of what we call “near piecewise-linear equilibria” when there is strong complementarity between the leader and the follower and the precision of the prior is poor. As a major consequence of this result, we prove local optimality of a class of slopey quantization strategies which had been suspected of being the optimal solution in the past, based on numerical evidence for Witsenhausen's counterexample

Study of the role of extracurricular activities on the academic achievement of elementary students from the viewpoint of teachers in the city of Manojan

Extracurricular activities are extremely important in the school process and since the curriculum does not meet all the needs of the students, the objective of this research was to study the impact of extracurricular activities on the academic performance of elementary students from the points of view of the teachers in the city of Manojan. The study was carried out with the help of a hundred teachers who have taught in the city during the 2012-2013 school year in public and non-governmental schools. The simple random sampling method was used. The results were obtained from a questionnaire that was analyzed with the SPSS software and the use of inferential statistics techniques and descriptive statistics (diagrams and tables). The results showed that extracurricular activities have a positive influence on the student's academic performance; its impact is positive on students' sustainable learning and have a positive impact on the quality of education.Las actividades extracurriculares son sumamente importantes en el proceso escolar y dado que el currículo no responde todas las necesidades de los estudiantes, el objetivo de esta investigación fue estudiar el impacto de las actividades extracurriculares en el rendimiento académico de los estudiantes de primaria a partir de los puntos de vista de los maestros en la ciudad de Manojan. El estudio se llevó a cabo con la ayuda de un centenar de docentes y maestras que han enseñado en la ciudad durante el año escolar 2012-2013 en escuelas públicas y no gubernamentales. Se hizo uso del método de muestreo aleatorio simple. Los resultados se obtuvieron a partir de un cuestionario que fue analizado con el software SPSS y el uso de técnicas de estadística inferencial y estadísticas descriptivas (diagramas y tablas). Los resultados evidenciaron que las actividades extracurriculares influyen positivamente en el rendimiento académico del alumno; su impacto es positive en el aprendizaje sostenible de los estudiantes y tienen un impacto positivo en la calidad de la educación.Atividades extracurriculares são extremamente importantes no processo escolar e porque o currículo não responde a todas as necessidades dos alunos, o objetivo desta pesquisa foi estudar o impacto das actividades extracurriculares sobre o desempenho acadêmico dos alunos do ensino fundamental da pontos de vista dos professores da cidade de Manojan. O estudo foi realizado com a ajuda de uma centena de professores que lecionaram na cidade durante o ano letivo de 2012-2013 em escolas públicas e não- governamentais. O método de amostragem aleatória simples foi utilizado. Os resultados foram obtidos a partir de um questionário que foi analisado com o software SPSS e o uso de técnicas de estatística inferencial e estatística descritiva (diagramas e tabelas). Os resultados mostraram que as atividades extracurriculares influenciam positivamente o desempenho acadêmico do aluno; o seu impacto é positivo na aprendizagem sustentável dos alunos e tem um impacto positivo na qualidade da educação