Detection, numerical simulation and approximate inversion of optoacoustic signals generated in multi-layered PVA hydrogel based tissue phantoms

In this article we characterize optoacoustic signals generated from layered tissue phantoms via short laser pulses by experimental and numerical means. In particular, we consider the case where scattering is effectively negligible and the absorbed energy density follows Beer-Lambert's law, i.e. is characterized by an exponential decay within the layers and discontinuities at interfaces. We complement experiments on samples with multiple layers, where the material properties are known a priori, with numerical calculations for a pointlike detector, tailored to suit our experimental setup. Experimentally, we characterize the acoustic signal observed by a piezoelectric detector in the acoustic far-field in backward mode and we discuss the implication of acoustic diffraction on our measurements. We further attempt an inversion of an OA signal in the far-field approximation.Comment: 10 pages, 6 figures, supplementary code at https://github.com/omelchert/SONOS.gi

Towards multimodal detection of melanoma thickness based on optical coherence tomography and optoacoustics

Melanoma skin cancer has one of the highest mortality rates of all types of cancer if not detected at an early stage. The survival rate is highly dependent on its penetration depth, which is commonly determined by histopathology. In this work, we aim at combining optical coherence tomography and optoacoustic as a non-invasive all-optical method to measure the penetration depth of melanoma. We present our recent achievements to setup a handheld multimodal device and also results from first in vivo measurements on healthy and cancerous skin tissue, which are compared to measurements obtained by ultrasound and histopathology. © 2016 SPIE

Magnetic structure of La2O3FeMnSe2 neutron diffraction and physical property measurements

We report on the characterization of the mixed layered lanthanum iron manganese oxyselenide La2O3FeMnSe2, where Fe and Mn share the same crystallographic position. The susceptibility data show a magnetic transition temperature of 76 K and a strong difference between field cooled and zero field cooled ZFC data at low fields. While the ZFC magnetization curve exhibits negative values below about 45 K, hysteresis measurement reveals, after an initial negative magnetic moment, a hysteresis loop typical for ferromagnetic material, pointing to competing ferromagnetic and antiferromagnetic interactions. Resistivity and dielectric permittivity measurements indicate that La2O3FeMnSe2 is a semiconductor. We performed x ray diffraction at 295 K and neutron diffraction at 90 and 1.7 K. The nuclear and magnetic structure was refined in the space group I4 mmm with a 4.11031 3 angstrom and c 18.7613 2 angstrom at 295 K. We did not detect a structural distortion and the Fe and Mn atoms were randomly distributed. The magnetic order was found to be antiferromagnetic, with a propagation vector q 0, 0, 0 and magnetic moments of 3.44 5 mu B per Fe Mn atom aligned within the a b plane. This magnetic order is different with respect to the pure Fe or Mn compositions reported in other studie

Bjorn Leines competing in the X-Games

Photo of Bjorn Leines competing in the Winter X-Games at Credsted Butte, Colorad