Optical characterization of contrast agents for optical coherence tomography

The use of contrast agents in almost every imaging modality has been known to enhance the sensitivity of detection and improve diagnostic capabilities by site-specifically labeling tissues or cells of interest. The imaging capabilities of Optical Coherence Tomography (OCT) need to be improved in order to detect early neoplastic changes in medicine and tumor biology. We introduce and characterize the optical properties of several types of optical contrast agents in OCT, namely encapsulating microspheres that incorporate materials including melanin, gold, and carbon. Micron-sized microspheres have been fabricated by state-of-the-art sonicating and ultrasound technology. The optical properties of optical contrast agents have been characterized according to their scattering and absorption coefficients and lifetimes using OCT and the oblique incidence reflectometry method. Finally, we demonstrate the use of these optical contrast agents in in vitro mice liver and analyze the contrast improvement from the OCT images. These optical contrast agents have the potential to improve the detection of in vivo pathologies in the future

Eccentric Exercise Facilitates Mesenchymal Stem Cell Appearance in Skeletal Muscle

Eccentric, or lengthening, contractions result in injury and subsequently stimulate the activation and proliferation of satellite stem cells which are important for skeletal muscle regeneration. The discovery of alternative myogenic progenitors in skeletal muscle raises the question as to whether stem cells other than satellite cells accumulate in muscle in response to exercise and contribute to post-exercise repair and/or growth. In this study, stem cell antigen-1 (Sca-1) positive, non-hematopoetic (CD45-) cells were evaluated in wild type (WT) and α7 integrin transgenic (α7Tg) mouse muscle, which is resistant to injury yet liable to strain, 24 hr following a single bout of eccentric exercise. Sca-1+CD45− stem cells were increased 2-fold in WT muscle post-exercise. The α7 integrin regulated the presence of Sca-1+ cells, with expansion occurring in α7Tg muscle and minimal cells present in muscle lacking the α7 integrin. Sca-1+CD45− cells isolated from α7Tg muscle following exercise were characterized as mesenchymal-like stem cells (mMSCs), predominantly pericytes. In vitro multiaxial strain upregulated mMSC stem cells markers in the presence of laminin, but not gelatin, identifying a potential mechanistic basis for the accumulation of these cells in muscle following exercise. Transplantation of DiI-labeled mMSCs into WT muscle increased Pax7+ cells and facilitated formation of eMHC+DiI− fibers. This study provides the first demonstration that mMSCs rapidly appear in skeletal muscle in an α7 integrin dependent manner post-exercise, revealing an early event that may be necessary for effective repair and/or growth following exercise. The results from this study also support a role for the α7 integrin and/or mMSCs in molecular- and cellular-based therapeutic strategies that can effectively combat disuse muscle atrophy

Equation of state and phonon frequency calculations of diamond at high pressures

The pressure-volume relationship and the zone-center optical phonon frequency of cubic diamond at pressures up to 600 GPa have been calculated based on Density Functional Theory within the Local Density Approximation and the Generalized Gradient Approximation. Three different approaches, viz. a pseudopotential method applied in the basis of plane waves, an all-electron method relying on Augmented Plane Waves plus Local Orbitals, and an intermediate approach implemented in the basis of Projector Augmented Waves have been used. All these methods and approximations yield consistent results for the pressure derivative of the bulk modulus and the volume dependence of the mode Grueneisen parameter of diamond. The results are at variance with recent precise measurements up to 140 GPa. Possible implications for the experimental pressure determination based on the ruby luminescence method are discussed.Comment: 10 pages, 6 figure

Optical manipulation of silicon microparticles in biological environments

Manipulation of micron-scale silicon particles has been investigated with optical tweezers implemented using a two-dimensional scanning trap driven with acousto-optic modulators. Spheres of latex, Poly(methyl methacrylate) (PMMA), silica, and silver-coated PMMA have been utilized to calibrate transverse trapping forces. The goal of this work is to non-invasively manipulate 10-20μm silicon-based devices in and around cells

Optics and Quantum Electronics

Contains table of contents for Section 3, reports on twenty-one research projects and a list of publications and meeting papers.Joint Services Electronics Program Contract DAAL03-92-C-0001U.S. Air Force - Office of Scientific Research Contract F49620-91-C-0091Charles S. Draper Laboratories Contract DL-H-441692MIT Lincoln LaboratoryNational Science Foundation Grant ECS 90-12787Fujitsu LaboratoriesU.S. Navy - Office of Naval Research Grant N00014-92-J-1302National Center for Integrated Photonic TechnologyNational Science Foundation Grant ECS 85-52701U.S. Navy - Office of Naval Research (MFEL) Grant N00014-91-C-0084U.S. Navy - Office of Naval Research (MFEL) Grant N00014-91-J-1956National Institutes of Health Grant R01-GM35459-08U.S. Air Force - Office of Scientific Research Grant F49620-93-1-0301MIT Lincoln Laboratory Contract BX-5098Electric Power Research Institute Contract RP3170-2