Observation of the Stimulated Quantum Cherenkov Effect

As charged particles surpass the speed of light in an optical medium they produce radiation - analogously to the way jet planes surpass the speed of sound and produce a sonic boom. This radiation emission, known as the Cherenkov effect, is among the most fundamental processes in electrodynamics. As such, it is used in numerous applications of particle detectors, particle accelerators, light sources, and medical imaging. Surprisingly, all Cherenkov-based applications and experiments thus far were fully described by classical electrodynamics even though theoretical work predicts new Cherenkov phenomena coming from quantum electrodynamics. The quantum description could provide new possibilities for the design of highly controllable light sources and more efficient accelerators and detectors. Here, we provide a direct evidence of the quantum nature of the Cherenkov effect and reveal its intrinsic quantum features. By satisfying the Cherenkov condition for relativistic electron wavefunctions and maintaining it over hundreds of microns, each electron simultaneously accelerates and decelerates by absorbing and emitting hundreds of photons in a coherent manner. We observe this strong interaction in an ultrafast transmission electron microscope, achieving for the first time a phase-matching between a relativistic electron wavefunction and a propagating light wave. Consequently, the quantum wavefunction of each electron evolves into a coherent plateau, analogous to a frequency comb in ultrashort laser pulses, containing hundreds of quantized energy peaks. Our findings prove that the delocalized wave nature of electrons can become dominant in stimulated interactions. In addition to prospects for known applications of the Cherenkov effect, our work provides a platform for utilizing quantum electrodynamics for applications in electron microscopy and in free-electron pump-probe spectroscopy.Comment: 15 pages, 4 figure

Spatiotemporal imaging of 2D polariton wave packet dynamics using free electrons

Peer ReviewedPostprint (author's final draft

Dynamics of optical vortices in van der Waals materials

peer reviewedQuantized vortices are topological defects found in different two-dimensional geometries, from liquid crystals to ferromagnets, famously involved in spontaneous symmetry breaking and phase transitions. Their optical counterparts appear in planar geometries as a universal wave phenomenon, possessing topologically protected orbital angular momentum (OAM). So far, the spatiotemporal dynamics of optical vortices, including vortex-pair creation and annihilation, has been observed only in Bose–Einstein condensates. Here we observe optical vortices in van der Waals materials and measure their dynamics, including events of pair creation and annihilation. Vortices of opposite OAM are involved in pair creation/annihilation events, and their relative signs determine the surrounding field profile throughout their motion. The vortices are made of phonon polaritons in hexagonal boron nitride, which we directly probe using free electrons in an ultrafast transmission electron microscope. Our findings promote future investigations of vortex phenomena in van der Waals platforms, toward their use for chiral plasmonics, quantum simulators, and control over selection rules in light–matter interactions

Novel Diagnosis of Lyme Disease: Potential for CAM Intervention

Lyme disease (LD) is the most common tick-borne disease in the northern hemisphere, producing a wide range of disabling effects on multiple human targets, including the skin, the nervous system, the joints and the heart. Insufficient clinical diagnostic methods, the necessity for prompt antibiotic treatment along with the pervasive nature of infection impel the development and establishment of new clinical diagnostic tools with increased accuracy, sensitivity and specificity. The goal of this article is 4-fold: (i) to detail LD infection and pathology, (ii) to review prevalent diagnostic methods, emphasizing inherent problems, (iii) to introduce the usage of in vivo induced antigen technology (IVIAT) in clinical diagnostics and (iv) to underscore the relevance of a novel comprehensive LD diagnostic approach to practitioners of Complementary and Alternative Medicine (CAM). Utilization of this analytical method will increase the accuracy of the diagnostic process and abridge the time to treatment, with antibiotics, herbal medicines and nutritional supplements, resulting in improved quality of care and disease prognosis

Segmentation of Pancreatic Subregions in Computed Tomography Images

The accurate segmentation of pancreatic subregions (head, body, and tail) in CT images provides an opportunity to examine the local morphological and textural changes in the pancreas. Quantifying such changes aids in understanding the spatial heterogeneity of the pancreas and assists in the diagnosis and treatment planning of pancreatic cancer. Manual outlining of pancreatic subregions is tedious, time-consuming, and prone to subjective inconsistency. This paper presents a multistage anatomy-guided framework for accurate and automatic 3D segmentation of pancreatic subregions in CT images. Using the delineated pancreas, two soft-label maps were estimated for subregional segmentation—one by training a fully supervised naïve Bayes model that considers the length and volumetric proportions of each subregional structure based on their anatomical arrangement, and the other by using the conventional deep learning U-Net architecture for 3D segmentation. The U-Net model then estimates the joint probability of the two maps and performs optimal segmentation of subregions. Model performance was assessed using three datasets of contrast-enhanced abdominal CT scans: one public NIH dataset of the healthy pancreas, and two datasets D1 and D2 (one for each of pre-cancerous and cancerous pancreas). The model demonstrated excellent performance during the multifold cross-validation using the NIH dataset, and external validation using D1 and D2. To the best of our knowledge, this is the first automated model for the segmentation of pancreatic subregions in CT images. A dataset consisting of reference anatomical labels for subregions in all images of the NIH dataset is also established

Observation of 2D Cherenkov Radiation

For over 80 years of research, the conventional description of free-electron radiation phenomena, such as Cherenkov radiation, has remained unchanged: classical three-dimensional electromagnetic waves. Interestingly, in reduced dimensionality, the properties of free-electron radiation are predicted to fundamentally change. Here, we present the first observation of Cherenkov surface waves, wherein free electrons emit narrow-bandwidth photonic quasiparticles propagating in two dimensions. The low dimensionality and narrow bandwidth of the effect enable us to identify quantized emission events through electron energy loss spectroscopy. Our results support the recent theoretical prediction that free electrons do not always emit classical light and can instead become entangled with the photons they emit. The two-dimensional Cherenkov interaction achieves quantum coupling strengths over 2 orders of magnitude larger than ever reported, reaching the single-electron–single-photon interaction regime for the first time with free electrons. Our findings pave the way to previously unexplored phenomena in free-electron quantum optics, facilitating bright, free-electron-based quantum emitters of heralded Fock states

Reassembly and co-crystallization of a family 9 processive endoglucanase from its component parts: structural and functional significance of the intermodular linker

Non-cellulosomal processive endoglucanase 9I (Cel9I) from Clostridium thermocellum is a modular protein, consisting of a family-9 glycoside hydrolase (GH9) catalytic module and two family-3 carbohydrate-binding modules (CBM3c and CBM3b), separated by linker regions. GH9 does not show cellulase activity when expressed without CBM3c and CBM3b and the presence of the CBM3c was previously shown to be essential for endoglucanase activity. Physical reassociation of independently expressed GH9 and CBM3c modules (containing linker sequences) restored 60–70% of the intact Cel9I endocellulase activity. However, the mechanism responsible for recovery of activity remained unclear. In this work we independently expressed recombinant GH9 and CBM3c with and without their interconnecting linker in Escherichia coli. We crystallized and determined the molecular structure of the GH9/linker-CBM3c heterodimer at a resolution of 1.68 Å to understand the functional and structural importance of the mutual spatial orientation of the modules and the role of the interconnecting linker during their re-association. Enzyme activity assays and isothermal titration calorimetry were performed to study and compare the effect of the linker on the re-association. The results indicated that reassembly of the modules could also occur without the linker, albeit with only very low recovery of endoglucanase activity. We propose that the linker regions in the GH9/CBM3c endoglucanases are important for spatial organization and fixation of the modules into functional enzymes