Enhancement of dielectrophoresis-based particle collection from high conducting fluids due to partial electrode insulation.

Dielectrophoresis (DEP) is a successful method to recover nanoparticles from different types of fluid. The DEP force acting on these particles is created by an electrode microarray that produces a nonuniform electric field. To apply DEP to a highly conducting biological fluid, a protective hydrogel coating over the metal electrodes is required to create a barrier between the electrode and the fluid. This protects the electrodes, reduces the electrolysis of water, and allows the electric field to penetrate into the fluid sample. We observed that the protective hydrogel layer can separate from the electrode and form a closed domed structure and that collection of 100 nm polystyrene beads increased when this occurred. To better understand this collection increase, we used COMSOL Multiphysics software to model the electric field in the presence of the dome filled with different materials ranging from low-conducting gas to high conducting phosphate-buffered saline fluids. The results suggest that as the electrical conductivity of the material inside the dome is reduced, the whole dome acts as an insulator which increases electric field intensity at the electrode edge. This increased intensity widens the high-intensity electric field factor zone resulting in increased collection. This informs how dome formation results in increased particle collection and provides insight into how the electric field can be intensified to the increase collection of particles. These results have important applications for increasing the recovery of biologically-derived nanoparticles from undiluted physiological fluids that have high conductance, including the collection of cancer-derived extracellular vesicles from plasma for liquid biopsy applications.

Theoretical and experimental analysis of negative dielectrophoresis-induced particle trajectories.

Many biomedical analysis applications require trapping and manipulating single cells and cell clusters within microfluidic devices. Dielectrophoresis (DEP) is a label-free technique that can achieve flexible cell trapping, without physical barriers, using electric field gradients created in the device by an electrode microarray. Little is known about how fluid flow forces created by the electrodes, such as thermally driven convection and electroosmosis, affect DEP-based cell capture under high conductance media conditions that simulate physiologically relevant fluids such as blood or plasma. Here, we compare theoretical trajectories of particles under the influence of negative DEP (nDEP) with observed trajectories of real particles in a high conductance buffer. We used 10-µm diameter polystyrene beads as model cells and tracked their trajectories in the DEP microfluidic chip. The theoretical nDEP trajectories were in close agreement with the observed particle behavior. This agreement indicates that the movement of the particles was highly dominated by the DEP force and that contributions from thermal- and electroosmotic-driven flows were negligible under these experimental conditions. The analysis protocol developed here offers a strategy that can be applied to future studies with different applied voltages, frequencies, conductivities, and polarization properties of the targeted particles and surrounding medium. These findings motivate further DEP device development to manipulate particle trajectories for trapping applications.

Three-Dimensional Cobalt Phosphide Nanowire Arrays as Negative Electrode Material for Flexible Solid-State Asymmetric Supercapacitors.

Despite the great progress that has been accomplished in supercapacitors, the imbalance of the development of positive and negative electrode materials still remains a critical issue to achieve high energy density; therefore, exploring high-performance negative electrode materials is highly desirable. In this article, three-dimensional cobalt phosphide (CoP) nanowire arrays were synthesized on a carbon cloth and were utilized as a binder-free supercapacitor negative electrode. The as-synthesized CoP nanowire arrays presented a high capacitance of 571.3 mF/cm2 at a current density of 1 mA/cm2. By using CoP nanowire arrays as the negative electrode and MnO2 nanowire arrays as the positive electrode, a flexible solid-state asymmetric supercapacitor has been fabricated and has exhibited excellent electrochemical performance, such as a high energy density of 0.69 mWh/cm3 and a high power density of 114.2 mW/cm3. In addition, the solid-state asymmetric supercapacitor shows high cycle stability with 82% capacitance retention after 5000 charge/discharge cycles. This work demonstrates that CoP is a promising negative electrode material for high-performance supercapacitor applications.

Eficiência de estudantes de Odontologia na seleção de cor com a escala Vita 3D-Master / Odontology students efficiency in color selection with Vita 3D-Master shade guide

A escala 3D-Master foi desenvolvida com a finalidade de satisfazer as maiores exigências estéticas dos pacientes, por possuir uma maior quantidade de tonalidades em relação às demais escalas. Contudo, possui uma técnica específica para a sua correta utilização, desconhecida por grande parte dos profissionais. O objetivo desse trabalho foi avaliar se, após o aprendizado da técnica correta de utilização da escala de cor VITA 3D-Master, recomendada pelo fabricante (VITA® Zahnfabrik, Alemanha), os profissionais da área de odontologia conseguem utilizá-la de forma adequada, atingindo o objetivo desejado que é a correta seleção de cor dos dentes. Para isso, foram utilizados seis elementos dentários de face vestibular hígida extraídos e doados pelos pacientes ao banco de dentes da faculdade. O terço médio da face vestibular de cada dente foi escolhido para a seleção de cor feita pelo espectrofotômetro digital VITA EasyShade programado para a escala VITA 3D-Master. Trinta e sete acadêmicos do último ano do curso de odontologia fizeram a seleção pelo método visual dos mesmos elementos dentários. Após a primeira seleção, uma palestra de 3 horas de duração foi ministrada por um técnico de prótese dental, ceramista e consultor da VITA®. Após essas orientações, os mesmos acadêmicos realizaram uma segunda seleção de cor com os mesmos elementos dentários, utilizando a técnica de seleção de cor da escala VITA 3D-Master. A técnica preconizada pela VITA® para a correta utilização da escala VITA 3D-Master impactou positivamente no resultado da segunda fase da pesquisa para a seleção de cor.

The 3D-Master shade guide was developed in order to meet higher patientsÆ aesthetic requirements as it has a greater number of shades when compared to other shade guides. However, a specific technique is needed for its correct use, which is unknown by most of professionals. The aim of this study was to evaluate if after learning the VITA 3D-Master shade guide correct technique use, recommended by the manufacturer (VITA® Zahnfabrik, Germany), dentistry professionals can use it properly, reaching the desired goal that is the correct selection of tooth color. For this, we used six extracted teeth of higid vestibular surface donated by patients to the university teeth bank. The middle third of the vestibular surface of each tooth was chosen for the color selection made by the digital spectrophotometer VITA Easyshade programmed for VITA 3D-Master shade guide. Thirty-seven students from the last year of the odontology course made the selection through the visual method in the same teeth. After the first selection, a 3 hours lecture was held by a qualified dental prosthetist, ceramist and VITA® consultant. After these guidelines, the same students performed a second color selection with the same teeth, using the VITA 3D-Master shade guide color selection technique. The technique recommended by VITA® for the correct use of VITA 3D-Master shade guide positively affected the outcome of the second phase of the research for color selection.

Rendimiento de los postulantes a la Carrera de Enfermería del Instituto "Dr. Andrés Barbero" de la Universidad Nacional de Asunción del año 2000

Estudio descriptivo-retrospectivo realizado con postulantes a la carrera de Enfermería, de las cuales se tomó como muestra 49 estudiantes que cursan el primer año. Presenta un diagnóstico de los factores causales del bajo rendimiento en los exámenes, además de una descripción del ambiente educativo y sus factores condicionantes