OIST Institutional Repository
Not a member yet
2744 research outputs found
Sort by
Pump-probe spectroscopy of Bose polarons: Dynamical formation and coherence
Get PDFWe propose and investigate a pump-probe spectroscopy scheme to unveil the time-resolved dynamics of fermionic or bosonic impurities immersed in a harmonically trapped Bose-Einstein condensate. In this scheme a pump pulse initially transfers the impurities from a noninteracting to a resonantly interacting spin state and, after a finite time in which the system evolves freely, the probe pulse reverses this transition. This directly allows us to monitor the nonequilibrium dynamics of the impurities as the dynamical formation of coherent attractive or repulsive Bose polarons and signatures of their induced interactions are imprinted in the probe spectra. We show that for interspecies repulsions exceeding the intraspecies ones a temporal orthogonality catastrophe occurs, followed by enhanced energy redistribution processes, independently of the impurity's flavor. This phenomenon takes place over the characteristic trap timescales. For much longer timescales a steady state is reached characterized by substantial losses of coherence of the impurities. This steady state is related to eigenstate thermalization and it is demonstrated to be independent of the system's characteristics.journal articl
Versatile gold-polymer nanointerfaces probed by GISAXS
Get PDFAn increasing trend toward integration of polymers in microelectronics and organic electronics has recently boosted research focusing in metal-polymer interfaces. These two materials differ vastly, with the former forming dense, crystalline, cohesive structures and the latter forming open structures bound together by weak van der Waals forces. As a result, there is dire need to assess their surface features (e.g., roughness) and correlate them with corresponding growth parameters, as metal-polymer interfaces are mainly determined by the preparation process. Here, we report a laboratory-based grazing-incidence small-angle x-ray scattering (GISAXS) study on distinct gold-polymer interfaces fabricated with different growth mechanisms, utilizing in-plane and oblique sputter geometries. GISAXS provided an improved analytic scheme for the buried surface in free-standing 2D gold-polymer nanosheets (with 19% porosity) revealing their fractal structure (Porod slope: -1.71). Two quantitative approaches (Height-Height Correlation and Power Spectral Density functions) were used to describe rough surfaces characterized by Atomic Force Microscopy (AFM) in consort with GISAXS data; different correlation length dependencies on growth time were revealed for gold rough surfaces grown on bare and polymerized Si. The results are considered pertinent to interfacial nanoscience and engineering, enabling statistical data collection from large surface areas, in a fast and nondestructive manner.journal articl
Design and Synthesize Small Molecular Self-Assembling Peptides for Biomedical Applications
Get PDFOkinawa Institute of Science and Technology Graduate UniversityDoctor of PhilosophyMolecular self-assembly is a spontaneous process of molecular association through noncovalent bond interaction. Imitating molecular self-assembly and creating novel functional molecular assemblies through synthetic chemistry are important issues in nanotechnology development. Small peptidic molecules are ideal candidates for imitating molecular selfassembly in biological system because of their biocompatibility and easy functionalization for bio-related applications including drug delivery, anti-cancer treatment and biosensors. In the first part (Chapter I), we address the essential role of nanotechnology in daily life, and a brief summarization on nanomaterial species, interaction mode, representative examples from biological system, available characterization methods, classes of artificial nanomaterials and their bio-related applications are outlined. In the second part (Chapter III), we have fabricated well-orientated nanofibrous structure through conjugation of easily deprotonated functional group to self-assembly building block. Via pH adjustment to manipulate molecular charge status, and further mechanical force guiding orientation of the nanofibrous structure. Large scale nanomaterial fabrication is achieved through evaporation casting capillary confinement. In the third part (Chapter IV), higher-order nanomaterial is approached by combination of co-assembly and self-sorting in multiple components. Stimulus such as light is applied on pre-stabilized template to obtain unconventional nanostructures. Two self-sorting components interact with each other at a nanoscale via both ALP and light regulation to reach a higher-order hierarchical assembly. Through ALP and CES - catalysed molecular self-assembly, two self-sorting components interact with each other to deliver a more robust nano-scaffold with potential in cell culture. In the fourth part (Chapter V), precisely subcellular organelle molecular self-assembly is realized by incorporation of the enzyme responsive motif with self-assembly building block. Introducing CES responsive motif to self-assembly peptide enhance cellular uptake of the self-assembly building block, intracellular recovery of the self-assembly peptide enriches on endoplasmic reticulum and thus leading to cancer cell apoptosis. Dual-subcellular-targeting anticancer therapy is reached by conjugating endoplasmic reticulum (ER)-targeted coumarin-functionalized short peptides and DNA alkylating agent (chlorambucil). After being uptaken and hydrolysis by intracellular CES, the coumarin-functionalized peptides self-assemble on ER to introduce ER stress while the chlorambucil targeting the nucleus to show synergistic effect on cancer cells.doctoral thesi
Antisymmetric linear magnetoresistance and the planar Hall effect
Get PDFThe phenomena of antisymmetric magnetoresistance and the planar Hall effect are deeply entwined with ferromagnetism. The intrinsic magnetization of the ordered state permits these unusual and rarely observed manifestations of Onsager’s theorem when time reversal symmetry is broken at zero applied field. Here we study two classes of ferromagnetic materials, rare-earth magnets with high intrinsic coercivity and antiferromagnetic pyrochlores with strongly-pinned ferromagnetic domain walls, which both exhibit antisymmetric magnetoresistive behavior. By mapping out the peculiar angular variation of the antisymmetric galvanomagnetic response with respect to the relative alignments of the magnetization, magnetic field, and electrical current, we experimentally distinguish two distinct underlying microscopic mechanisms: namely, spin-dependent scattering of a Zeeman-shifted Fermi surface and anomalous electron velocities. Our work demonstrates that the anomalous electron velocity physics typically associated with the anomalous Hall effect is prevalent beyond the ρxy(Hz) channel, and should be understood as a part of the general galvanomagnetic behavior.journal articl
Modified celestial amplitude in Einstein gravity
Get PDFIn this paper we evaluate the modified celestial amplitude for gravitons and gluons, as defined in [4]. We find that the modified (tree) amplitude is finite for gravitons in Einstein gravity. The modified amplitude behaves like correlation function of operators inserted at various points of null-infinity in the Minkowski space-time. Therefore, unlike the standard celestial amplitudes, these are three dimensional objects. We also show that this amplitude admits conformal soft factorization recently studied in the literature.journal articl
Species-specific molecular responses of wild coral reef fishes during a marine heatwave
Get PDFThe marine heatwave of 2016 was one of the longest and hottest thermal anomalies recorded on the Great Barrier Reef, influencing multiple species of marine ectotherms, including coral reef fishes. There is a gap in our understanding of what the physiological consequences of heatwaves in wild fish populations are. Thus, in this study, we used liver transcriptomes to understand the molecular response of five species to the 2016 heatwave conditions. Gene expression was species specific, yet we detected overlap in functional responses associated with thermal stress previously reported in experimental setups. The molecular response was also influenced by the duration of exposure to elevated temperatures. This study highlights the importance of considering the effects of extreme warming events when evaluating the consequences of climate change on fish communities.journal articl
Enhanced Directional Coupling of Light with a Whispering Gallery Microcavity
Get PDFDirectional coupling of light in nanophotonic circuits has recently attracted increasing interest, with numerous experimental realizations based on broken rotational or mirror symmetries of the light–matter system. The most prominent underlying effect is the spin–orbit interaction of light in subwavelength structures. Unfortunately, coupling of light to such structures is, in general, very inefficient. In this work, we experimentally demonstrate an order of magnitude enhancement of the directional coupling between two nanowaveguides by means of a whispering gallery microcavity. We also show that both transverse magnetic and transverse electric modes can be used for the enhancement.journal articl
Organic additive engineering toward efficient perovskite light‐emitting diodes
Get PDFPerovskite materials with excellent optical and electrical properties are promising for light‐emitting diodes. In the field of perovskite light‐emitting diodes (PeLEDs), organic materials additive engineering has been proved to be an effective scheme for enhancing efficiency and stability in PeLEDs. Most impressively, the reported external quantum efficiency of PeLEDs based on perovskite‐organic composite has reached over 20%. Herein, we will review the important progress of the organic materials' additive‐modified PeLEDs and discuss the remaining problems and challenges and the key research direction in the near future.journal articl
Closed-form expression for cross-channel conformal blocks near the lightcone
Get PDFIn the study of conformal field theories, conformal blocks in the lightcone limit are fundamental to the analytic conformal bootstrap method. Here we consider the lightcone limit of 4-point functions of generic scalar primaries. Based on the nonperturbative pole structure in spin of Lorentzian inversion, we propose the natural basis functions for cross-channel conformal blocks. In this new basis, we find a closed-form expression for crossed conformal blocks in terms of the Kampe de Feriet function, which applies to intermediate operators of arbitrary spin in general dimensions. We derive the general Lorentzian inversion for the case of identical external scaling dimensions. Our results for the lightcone limit also shed light on the complete analytic structure of conformal blocks in the lightcone expansion.journal articl
