Search results for "interference"

Spectral analog of the Gouy phase shift

2013

We demonstrate the existence of the spectral phase shift a pulse experiences when it is subjected to spectral focusing. This $\frac{\ensuremath{\pi}}{2}$ phase shift is the spectral analog of the Gouy phase shift a 2D beam experiences when it crosses its focal plane. This spectral Gouy phase shift is measured using spectral interference between a reference pulse and a negatively chirped parabolic pulse experiencing spectral focusing in a nonlinear photonic crystal fiber. To avoid inherent phase instability in the measurement, both reference and parabolic pulses are generated with a $4\mathrm{\text{\ensuremath{-}}}f$ pulse shaper and copropagate in the same fiber. We measure a spectral phase…

Using Partial Coherence and Digital Holography for 3D Imaging and Profile Extraction

2008

Two approaches for 3D imaging are presented. At first we use partial coherence of the light source and in the second we compute the unwrapped phase by illuminating the object from several slightly different angles.

Resolution improvement by single-exposure superresolved interferometric microscopy with a monochrome sensor

2011

Single-exposure superresolved interferometric microscopy (SESRIM) by RGB multiplexing has recently been proposed as a way to achieve one-dimensional superresolved imaging in digital holographic microscopy by a single-color CCD snapshot [Opt. Lett. 36, 885 (2011)]. Here we provide the mathematical basis for the operating principle of SESRIM, while we also present a different experimental configuration where the color CCD camera is replaced by a monochrome (B&W) CCD camera. To maintain the single-exposure working principle, the object field of view (FOV) is restricted and the holographic recording is based on image-plane wavelength-dispersion spatial multiplexing to separately record the thre…

Gaussian pulse propagation in dispersion-managed systems using chirped fiber gratings with group delay ripples

2005

We study the propagation of Gaussian-shaped pulses in grating-compensated dispersion-managed systems with group delay ripples (GDR). We show that the intersymbol interference caused by the GDR in gratings can be substantially reduced by nonlinear optical loop mirrors and the 40-Gb/s system performance can achieve transoceanic transmission in the presence of amplifier noise and random variations in ripple period of the gratings along the transmission line.

Axial resonance of periodic patterns by using a Fresnel biprism.

2013

This paper proposes a method for the generation of high-contrast localized sinusoidal fringes with spatially noncoherent illumination and relatively high light throughput. The method, somehow similar to the classical Lau effect, is based on the use of a Fresnel biprism. It has some advantages over previous methods for the noncoherent production of interference fringes. One is the flexibility of the method, which allows the control of the fringe period by means of a simple axial shift of the biprism. Second is the rapid axial fall-off in visibility around the high-contrast fringe planes. And third is the possibility of creating fringes with increasing or with constant period as the light bea…

‘Nonlocal’ dispersion cancelation with classical light

2009

We show a classical analog of the original nonlocal dispersion cancelation effect in intensity interferometry with stationary light obeying Gaussian statistics. The dispersion compensation is due to the uncorrelation of the spectral components of the radiation. Although this classical counterpart phenomenon is not nonlocal in a strict quantum mechanical sense, it suggests that some second-order interference devices relying on temporal entanglement do not require a quantum light source.

Gata4 Blocks Somatic Cell Reprogramming By Directly Repressing Nanog

2012

Abstract Somatic cells can be reprogrammed to induced pluripotent stem (iPS) cells by ectopic expression of the four factors Oct4, Klf4, Sox2, and Myc. Here, we investigated the role of Gata4 in the reprogramming process and present evidence for a negative role of this family of transcription factors in the induction of pluripotency. Coexpression of Gata4 with Oct4, Klf4, and Sox2 with or without Myc in mouse embryonic fibroblasts greatly impaired reprogramming and endogenous Nanog expression. The lack of Nanog upregulation was associated with a blockade in the transition from the initiation phase of reprogramming to the full pluripotent state characteristic of iPS cells. Addition of Nanog …

α-Mannosyl-Functionalized Cationic Nanohydrogel Particles for Targeted Gene Knockdown in Immunosuppressive Macrophages

2019

Immunosuppressive M2 macrophages govern the immunophathogenic micromilieu in many severe diseases including cancer or fibrosis, thus, their re-polarization through RNA interference is a promising concept to support combinatorial therapies. For targeted siRNA delivery, however, safe and stable carriers are required that manage cell specific transport to M2 macrophages. Here, siRNA-loaded cationic nanogels are reported with α-mannosyl decorated surfaces that target and modify M2 macrophages selectively. Via amphiphilic precursor block copolymers bearing one single α-mannosyl moiety at their chain end mannosylated cationic nanohydrogel particles (ManNP) were obtained of 20 nm diameter determin…

From Polymers to Functional Biomaterials.

2017

SiRNA-mediated in vivo gene knockdown by acid-degradable cationic nanohydrogel particles

2017

Cationic nanohydrogel particles have become an attractive tool for systemic siRNA delivery, but improvement of their in vivo tolerance is desirable, especially to prevent potential long term side effects by tissue and cellular accumulation. Here, we designed novel ketal cross-linked cationic nanohydrogel particles that were assessed for reduced tissue accumulation and robust siRNA delivery in vitro and in vivo. An oligo-amine cross-linker equipped with a ketal moiety in its core was synthesized and applied to nanohydrogel cross-linking of self-assembled reactive ester block copolymers in DMSO. The resulting acid-sensitive cationic nanoparticles spontaneously disassembled over time in acidic…