Microwave and THz Metamaterial-Based Devices for Potential Applications in NDE, Chem-Bio Detection and Dielectric Characterization of Complex Oxide Thin Films

The purpose of this chapter is to convey a message that the variety of applications of the classical (and the novel ones, such as Mie resonance based) metamaterials are going far beyond the originally proposed applications such as geometrical optics and antennas. In addition, it is important to mention that most of these applications are just an idea or a first proof of principle. Hence, an additional message of this chapter is that a lot of further research is required to implement these scientifically sound ideas. It is also a hope that this chapter will trigger the reader\u27s curiosity and interest to pursue this exciting field, which will yield additional applications that have never been imagined

Microwave Nondestructive Evaluation of Dielectric Materials with a Metamaterial Lens

A novel microwave Nondestructive Evaluation (NDE) sensor was developed in an attempt to increase the sensitivity of the microwave NDE method for detection of defects small relative to a wavelength. The sensor was designed on the basis of a negative index material (NIM) lens. Characterization of the lens was performed to determine its resonant frequency, index of refraction, focus spot size, and optimal focusing length (for proper sample location). A sub-wavelength spot size (3 dB) of 0.48 lambda was obtained. The proof of concept for the sensor was achieved when a fiberglass sample with a 3 mm diameter through hole (perpendicular to the propagation direction of the wave) was tested. The hole was successfully detected with an 8.2 cm wavelength electromagnetic wave. This method is able to detect a defect that is 0.037 lambda. This method has certain advantages over other far field and near field microwave NDE methods currently in use

An in vitro assay of collagen fiber alignment by acupuncture needle rotation

BACKGROUND: During traditional acupuncture therapy, soft tissues attach to and wind around the acupuncture needle. To study this phenomenon in a controlled and quantitative setting, we performed acupuncture needling in vitro. METHODS: Acupuncture was simulated in vitro in three-dimensional, type I collagen gels prepared at 1.5 mg/ml, 2.0 mg/ml, and 2.5 mg/ml collagen, and either crosslinked with formalin or left untreated. Acupuncture needles were inserted into the gels and rotated via a computer-controlled motor at 0.3 rev/sec for up to 10 revolutions while capturing the evolution of birefringence under cross-polarization. RESULTS: Simulated acupuncture produced circumferential alignment of collagen fibers close to the needle that evolved into radial alignment as the distance from the needle increased, which generally matched observations from published tissue explant studies. All gels failed prior to 10 revolutions, and the location of failure was near the transition between circumferential and radial alignment. Crosslinked collagen failed at a significantly lower number of revolutions than untreated collagen, whereas collagen concentration had no effect on gel failure. The strength of the alignment field increased with increasing collagen concentration and decreased with crosslinking. Separate studies were performed in which the gel thickness and depth of needle insertion were varied. As gel thickness increased, gels failed at fewer needle revolutions. For the same depth of insertion, alignment was greater in thinner gels. Alignment increased as the depth of insertion increased. CONCLUSION: These results indicate that the mechanostructural properties of soft connective tissues may affect their response to acupuncture therapy. The in vitro model provides a platform to study mechanotransduction during acupuncture in a highly controlled and quantitative setting

O caminhar acadêmico e profissional de duas professoras em educação estatística

Este artigo apresenta a trajetória e as experiências de duas professoras, primeiras autoras do mesmo, que se encontraram no doutorado, sob orientação da terceira, narrando a partir do espaço tridimensional da pesquisa, o encontro das docentes com as temáticas estudadas na pós-graduação, bem como sobre os fazeres, idas e vindas que as levaram ao campo da educação. A partir da autobiografia das docentes, espera-se analisar as experiências que as constituíram como sujeitos, professoras e pesquisadoras no campo da Educação Estatística. As narrativas apresentam tanto os sentimentos, memórias e experiências das docentes que as levaram ao campo da educação, desde a infância, quanto aos lugares e pessoas que marcaram essas experiências. Em suma, percebeu-se que o sujeito professor se constitui não somente a partir da conclusão de um curso de graduação, mas, sim, ao longo de toda a sua história de vida, das suas experiências com os outros desde a infância, com seus professores e colegas, na interação com seus pares, envolvendo aspectos afetivos que vão direcionando os sujeitos para esta ou aquela área, que, nesse caso, culminou na pesquisa científica no campo da Educação Estatística

A mechanochemical model of striae distensae

Striae distensae, otherwise known as stretch marks, are common skin lesions found in a variety of clinical settings. They occur frequently during adolescence or pregnancy where there is rapid tissue expansion and in clinical situations associated with corticosteroid excess. Heralding their onset is the appearance of parallel inflammatory streaks aligned perpendicular to the direction of skin tension. Despite a considerable amount of investigative research, the pathogenesis of striae remains obscure. The interpretation of histologic samples – the major investigative tool – demonstrates an association between dermal lymphocytic inflammation, elastolysis, and a scarring response. Yet the primary causal factor in their aetiology is mechanical; either skin stretching due to underlying tissue expansion or, less frequently, a compromised dermis affected by normal loads. In this paper, we investigate the pathogenesis of striae by addressing the coupling between mechanical forces and dermal pathology. We develop a mathematical model that incorporates the mechanical properties of cutaneous fibroblasts and dermal extracellular matrix. By using linear stability analysis and numerical simulations of our governing nonlinear equations, we show that this quantitative approach may provide a realistic framework that may account for the initiating events

Nanoporous membrane-sealed microfluidic devices for improved cell viability

Abstract Cell-laden microfluidic devices have broad potential in various biomedical applications, including tissue engineering and drug discovery. However, multiple difficulties encountered while culturing cells within devices affecting cell viability, proliferation, and behavior has complicated their use. While active perfusion systems have been used to overcome the diffusive limitations associated with nutrient delivery into microchannels to support longer culture times, these systems can result in non-uniform oxygen and nutrient delivery and subject cells to shear stresses, which can affect cell behavior. Additionally, histological analysis of cell cultures within devices is generally laborious and yields inconsistent results due to difficulties in delivering labeling agents in microchannels. Herein, we describe a simple, cost-effective approach to preserve cell viability and simplify labeling within microfluidic networks without the need for active perfusion. Instead of bonding a microfluidic network to glass, PDMS, or other solid substrate, the network is bonded to a semipermeable nanoporous membrane. The membrane-sealed devices allow free exchange of proteins, nutrients, buffers, and labeling reagents between the microfluidic channels and culture media in static culture plates under sterile conditions. The use of the semi-permeable membrane dramatically simplifies microniche cell culturing while avoiding many of the complications which arise from perfusion systems

ARTICLE Neurite Growth in 3D Collagen Gels With Gradients of Mechanical Properties

ABSTRACT: We have designed and developed a microfluidic system to study the response of cells to controlled gradients of mechanical stiffness in 3D collagen gels. An 'H'-shaped, source-sink network was filled with a type I collagen solution, which self-assembled into a fibrillar gel. A 1D gradient of genipin-a natural crosslinker that also causes collagen to fluoresce upon crosslinking-was generated in the cross-channel through the 3D collagen gel to create a gradient of crosslinks and stiffness. The gradient of stiffness was observed via fluorescence. A separate, underlying channel in the microfluidic construct allowed the introduction of cells into the gradient. Neurites from chick dorsal root ganglia explants grew significantly longer down the gradient of stiffness than up the gradient and than in control gels not treated with genipin. No changes in cell adhesion, collagen fiber size, or density were observed following crosslinking with genipin, indicating that the primary effect of genipin was on the mechanical properties of the gel. These results demonstrate that (1) the microfluidic system can be used to study durotactic behavior of cells and (2) neurite growth can be directed and enhanced by a gradient of mechanical properties, with the goal of incorporating mechanical gradients into nerve and spinal cord regenerative therapies