Controlling light Propagation in complex media for Imaging, focusing and Brillouin measurements

Imaging and focusing light through turbid media are two fundamental challenges of optical sciences that have attracted significant attention in recent years. Traditional optical systems such as confocal microscopy, optical coherence tomography and multi-photon microscopy utilize ballistic photons traveling in straight trajectories to generate an image; however, with increasing depth, the signal to noise ratio (SNR) decreases as the number of ballistic photons decays exponentially. In the first part of this thesis I present two novel techniques for imaging through scattering medium by decoding seemingly random scattered light patterns and demonstrate the highest resolution and acquisition speed to date. For point scanning applications I also study methods to focus light through scattering materials and report on a fundamental trade-off between the focal point intensity and the focal plane in which it is generated. In the second part of the thesis I investigate how the ability to control light propagation within turbid media can be used to enhance point scanning measurements such as Brillouin scattering spectroscopy, a technology recently developed in our lab to characterize material stiffness without contact. To do this, I first present a novel optical system (“spectral coronagraph”) which yields an improved extinction ratio when inserted into Brillouin spectrometers to enable the spectral separation in the presence of scattering or close to interfaces. Additionally, to enhance the Brillouin signal, I apply adaptive optics techniques, first developed for astronomy applications, where the incident wave front is shaped to circumvent for optical phase aberrations. Using adaptive optics, I show signal enhancement in artificial and biological samples, an important feature in the context of Brillouin microscopy to promote high SNR imaging in practical scenarios

A novel flexible fixation technique for Lisfranc injuries: clinical outcomes and radiographic follow-up

Objectives: The purpose of this investigation is to present the follow-up results and patient-reported outcome measures (PROMs) of a continuous series of surgically managed Lisfranc injuries whose constructs included a novel technique. Methods: Our billing database was retrospectively queried by Current Procedural Terminology (CPT) codes to identify all Lisfranc injuries managed operatively between 2018 and 2021. Basic demographic data were collected. Clinical notes and radiographs were reviewed. Patients were contacted prospectively to complete the Foot and Ankle Ability Measurement – Activities of Daily Living (FAAM-ADL), Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Intensity, PROMIS Pain Interference, and PROMIS Depression surveys. Descriptive statistics were calculated. Results: Sixteen patients were included. While all patients underwent flexible fixation (FF), nine of them underwent concomitant open reduction internal fixation (ORIF) and seven, concomitant primary arthrodesis. Median radiographic and PROMs follow-up time was 7.3 months (IQR 4.4–11.6) and 25.8 (IQR 9.5–32.4), respectively. All fusion patients had evidence of joint fusion, and 8/9 of ORIF patients maintained articular congruity without evidence of arthritis at final follow-up. Median PROMs were 85 (64.75–93.5), 53.1 (49.7–57.75), 45.7 (37.7–51.3), and 46 (43.3–52.28) for the FAAM-ADL, PROMIS Pain Interference, PROMIS Pain Intensity, and PROMIS Depression scores, respectively. Conclusion: The novel FF technique proposed for residual tarsometatarsal subluxation in Lisfranc injuries appears to be safe and effective, with good PROMs at two-year follow-up and low complication rates, obviating the need for hardware removal. Level of Evidence IV; Therapeutics Studies; Cases Series

Singular Cucker-Smale Dynamics

The existing state of the art for singular models of flocking is overviewed, starting from microscopic model of Cucker and Smale with singular communication weight, through its mesoscopic mean-filed limit, up to the corresponding macroscopic regime. For the microscopic Cucker-Smale (CS) model, the collision-avoidance phenomenon is discussed, also in the presence of bonding forces and the decentralized control. For the kinetic mean-field model, the existence of global-in-time measure-valued solutions, with a special emphasis on a weak atomic uniqueness of solutions is sketched. Ultimately, for the macroscopic singular model, the summary of the existence results for the Euler-type alignment system is provided, including existence of strong solutions on one-dimensional torus, and the extension of this result to higher dimensions upon restriction on the smallness of initial data. Additionally, the pressureless Navier-Stokes-type system corresponding to particular choice of alignment kernel is presented, and compared - analytically and numerically - to the porous medium equation

Mapping of functionalized regions on carbon nanotubes by scanning tunneling microscopy

Scanning tunneling microscopy (STM) gives us the opportunity to map the surface of functionalized carbon nanotubes in an energy resolved manner and with atomic precision. But this potential is largely untapped, mainly due to sample stability issues which inhibit reliable measurements. Here we present a simple and straightforward solution that makes away with this difficulty, by incorporating the functionalized multiwalled carbon nanotubes (MWCNT) into a few layer graphene - nanotube composite. This enabled us to measure energy resolved tunneling conductance maps on the nanotubes, which shed light on the level of doping, charge transfer between tube and functional groups and the dependence of defect creation or functionalization on crystallographic orientation.Comment: Keywords: functionalization, carbon nanotubes, few layer graphene, STM, CITS, ST

Large bowel obstruction due to sesame seed bezoar: a case report

peer-reviewedWe report a case of a 79 year old man with a known benign anastomotic stricture presenting with large bowel obstruction. At laparotomy the obstruction was found to be caused by a large sesame seed bezoar. Seed bezoars are well known to cause impaction in the rectum but have never been previously reported to cause large bowel obstruction. We recommend that patients with known large bowel strictures should be advised not to eat seeds as this could ultimately lead to obstruction, ischaemia or perforationPUBLISHEDpeer-reviewe