Stimulation of angiogenesis through collagen gel by applying shear stress and interstitial flow

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005."June 2005."Includes bibliographical references (leaves 36-38).The induction of angiogenesis has been documented in many diseases such as cancer, arthritis, and diabetes. Angiogenesis can be stimulated by a variety of signals including a mechanical stress applied to the apical side of endothelial cells. To get a better understanding of this mechanical stimulus, a parallel plate flow chamber was designed and tested to elicit a constant laminar flow onto a monolayer of endothelial cells. The goal of this research was to develop a more physiologically similar in vitro system to study the effects of shear stress on endothelial cells. Unlike prior flow chamber apparatus, this chamber allows the cells to be seeded on collagen gel rather than a rigid substrate to more closely mimic in vivo environment. A shear stress of I Pa was applied to the endothelial cells for a duration of 36 hours. Results show that after flow was initiated for this duration, a change in shape of the endothelial cells can be seen when compared to the static condition. Elongation and alignment of cells plated on collagen gel can be seen in the direction of flow, though not at pronounced as the elongation typically seen from cells plated on rigid substrates. Nuclear and F-actin staining also revealed similar results.(cont.) The nuclear staining revealed a confluent monolayer formation occurred prior to flow and was maintained throughout the experiment. A change in organization of the F-actin fibers, from radially protruding out from the nucleus during static condition to a more ordered arrangement after the flow was implemented could also be seen. The changes in cell appearance illustrates that the mechanical stimulus of a shear stress has an effect on endothelial cell arrangement and suggests that this effect depends to some degree on the cell adhesion substrate stiffness. Furthermore, new research in this area can look at both the signaling that leads to these morphological changes as well as the factors that control angiogenesis.by Mitun P. Ranka.S.B

Experimental investigation of cut-off phenomena in non-linear photonic crystal fibers

The modal cut-off is investigated experimentally in a series of high quality non-linear photonic crystal fibers. We demonstrate a suitable measurement technique to determine the cut-off wavelength and verify it by inspecting the near field of the modes that may be excited below and above the cut-off. We observe a double peak structure in the cut-off spectra, which is attributed to a splitting of the higher order modes. The cut-off is measured for seven different fiber geometries with different pitches and relative hole size, and a very good agreement with recent theoretical work is found.Comment: 3 pages including 1 table and 4 figures. Accepted for Optics Letter

Few cycle pulse propagation

We present a comprehensive framework for treating the nonlinear interaction of few-cycle pulses using an envelope description that goes beyond the traditional SVEA method. This is applied to a range of simulations that demonstrate how the effect of a $\chi^{(2)}$ nonlinearity differs between the many-cycle and few-cycle cases. Our approach, which includes diffraction, dispersion, multiple fields, and a wide range of nonlinearities, builds upon the work of Brabec and Krausz[1] and Porras[2]. No approximations are made until the final stage when a particular problem is considered. The original version (v1) of this arXiv paper is close to the published Phys.Rev.A. version, and much smaller in size.Comment: 9 pages, 14 figure

X-wave mediated instability of plane waves in Kerr media

Plane waves in Kerr media spontaneously generate paraxial X-waves (i.e. non-dispersive and non-diffractive pulsed beams) that get amplified along propagation. This effect can be considered a form of conical emission (i.e. spatio-temporal modulational instability), and can be used as a key for the interpretation of the out of axis energy emission in the splitting process of focused pulses in normally dispersive materials. A new class of spatio-temporal localized wave patterns is identified. X-waves instability, and nonlinear X-waves, are also expected in periodical Bose condensed gases.Comment: 4 pages, 6 figure

Elastic Modulus of Polycrystalline Halide Perovskite Thin Films on Substrates

Using an innovative combination of multi beam-optical sensor (MOSS) curvature and X-ray diffraction (XRD) techniques, the Young's modulus, E, of polycrystalline MAPbI3 metal-halide perovskite (MHP) thin films attached to two different types of substrates (SiO2 and Si) is measured to be in the 6.1-6.2 GPa range. This is significantly lower than that of corresponding MAPbI3 single-crystals, which offers a new avenue of tuning E of MHP thin films via microstructural tailoring for influencing the mechanical reliability of perovskite solar cells (PSCs).Comment: 9 pages, 1 figure, supplementary information (1 figure, 1 table

Časopis Geološki anali balkanskoga poluostrva - trenutno stanje i perspektive

The journal Geološki Anali Balkanskoga Poluostrva was founded by geologists and enthusiasts led by Prof. Jovan Žujović in 1888, while the first issue was published a year later. The first issue had 160 pages, containing 20 figures and a geological sketch map of the Kingdom of Serbia created by .ujovi., printed in color at a scale of 1:500000. For the first six decades, the journal did not have a regular annual periodicity, but since 1949, it has been published regularly every year. From the very beginning, the journal published articles from all geological disciplines, but also from mining, which makes it the oldest scientific and professional geological journal in Serbia, as well as in the Balkans. The journal shared the fate of the state and the people, so it was not published during the First and Second World Wars, while the general periodicity of the journal before the First World War was much weaker than between the two wars (1918.1941). Since 2017, following the publishing standards of the 21st century ] the journal has been accepting only online submission of papers through the Open Journal System (OJS) platform, which also represents the Internet presentation of the journal. In addition to the OJS platform, a digital library of the journal was created. It contains metadata about all published papers from the first to the last issue, according to the Dublin core standard, while the full PDF versions of works from 2002 are downloadable free of charge in accordance with the Creative Commons Attribute 4.0 International (CC BY) license. The editorial board plans to publish two issues per year since 2018, which is a basic precondition for a journal to be included in the evaluation process for assigning impact factor and indexing in the SCIe list

On the Properties of Two Pulses Propagating Simultaneously in Different Dispersion Regimes in a Nonlinear Planar Waveguide

Properties of two pulses propagating simultaneously in different dispersion regimes, anomalous and normal, in a Kerr-type planar waveguide are studied in the framework of the nonlinear Schroedinger equation. Catastrophic self-focusing and spatio-temporal splitting of the pulses is investigated. For the limiting case when the dispersive term of the pulse propagating in the normal dispersion regime can be neglected an indication of a possibility of a stable self-trapped propagation of both pulses is obtained.Comment: 18 pages (including 15 eps figures

Ultra-precise measurement of optical frequency ratios

We developed a novel technique for frequency measurement and synthesis, based on the operation of a femtosecond comb generator as transfer oscillator. The technique can be used to measure frequency ratios of any optical signals throughout the visible and near-infrared part of the spectrum. Relative uncertainties of $10^{-18}$ for averaging times of 100 s are possible. Using a Nd:YAG laser in combination with a nonlinear crystal we measured the frequency ratio of the second harmonic $\nu_{SH}$ at 532 nm to the fundamental $\nu_0$ at 1064 nm, $\nu_{SH}/\nu_0 = 2.000 000 000 000 000 001 \times (1 \pm 7 \times 10^{-19})$.Comment: 4 pages, 4 figure

Resonant nonstationary amplification of polychromatic laser pulses and conical emission in an optically dense ensemble of neon metastable atoms

Experimental and numerical investigation of single-beam and pump-probe interaction with a resonantly absorbing dense extended medium under strong and weak field-matter coupling is presented. Significant probe beam amplification and conical emission were observed. Under relatively weak pumping and high medium density, when the condition of strong coupling between field and resonant matter is fulfilled, the probe amplification spectrum has a form of spectral doublet. Stronger pumping leads to the appearance of a single peak of the probe beam amplification at the transition frequency. The greater probe intensity results in an asymmetrical transmission spectrum with amplification at the blue wing of the absorption line and attenuation at the red one. Under high medium density, a broad band of amplification appears. Theoretical model is based on the solution of the Maxwell-Bloch equations for a two-level system. Different types of probe transmission spectra obtained are attributed to complex dynamics of a coherent medium response to broadband polychromatic radiation of a multimode dye laser.Comment: 9 pages, 13 figures, corrected, Fig.8 was changed, to be published in Phys. Rev.