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Bridging Single-Particle Characterisation Gaps of Optical Microscopy in the Nano-Submicron Regime
Get PDFAs the practical importance of particles in the nano-submicron size regime continues to increase in both biomedical applications and industrial processes, so does the need for accurate and versatile characterisation methods. Optical scattering microscopy methods are commonly used for single-particle characterisation as they provide quick measurements at physiologically relevant conditions with detection limits reaching down to individual biomolecules. However, quantitative particle characterisation using optical microscopy often rely on assumptions about the surrounding media and theparticle, including solution viscosity, boundary conditions, as well as particle shape and material. Since these assumptions are difficult to evaluate, particle characterisation beyond hydrodynamic radius and/or mass remains challenging.The aim of this thesis is to contribute to bridging the gaps that limit quantitative optical microscopy-based characterisation of individual particles in the nano-submicron regime by both developing new and improving existing microscopy methods. Specifically, in Paper I a method was developed to evaluate the relation between diffusivity and particle size to enable measurements of the hydrodynamic boundary condition. Papers II-V are based around the development of holographic nanoparticle tracking (H-NTA) and extensions thereof, with the intent of using the complex-valued optical field for material sensitive particle characterisation with minimal dependence on the surrounding media. In Paper II, H-NTA by itself was used to characterise suspensions containing nanobubbles and molecular aggregates. In Paper III, the combination of H-NTA with deep learning was used to achieve simultaneous quantification of size and refractive index directly from single microscopy images, which allowed detection of reversible fluctuations in nanoparticle aggregates. In Paper IV, H-NTA augmented with a low frequency attenuation filter, coined twilight holography, was used to investigate the interaction between herpes viruses and functionalised gold nanoparticles in terms of size, bound gold mass, and virus refractive index. In Paper V, the combination of twilight holography and interferometric scattering microscopy (iSCAT) was used to quantify both size and polarizability of individual nanoparticles without the need of detailed knowledge about the surrounding media. Taken together, the presented results in this thesis provide both new insights into heterogenous nanoparticle systems and contributes to narrowing the gap for detailed optical particle characterisation
Reconstructing the shock history in the CMZ of NGC 253 with ALCHEMI
Get PDFContext. HNCO and SiO are well-known shock tracers and have been observed in nearby galaxies, including the nearby (D = 3.5 Mpc) starburst galaxy NGC 253. The simultaneous detection of these two species in regions where the star-formation rate is high may be used to study the shock history of the gas. Aims. We perform a multi-line molecular study of NGC 253 using the shock tracers SiO and HNCO and aim to characterize its gas properties. We also explore the possibility of reconstructing the shock history in the central molecular zone (CMZ) of the galaxy. Methods. Six SiO transitions and eleven HNCO transitions were imaged at high resolution 1.\ub76 (28 pc) with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the ALCHEMI Large Programme. Both non local thermaldynamic equilibrium (non-LTE) radiative transfer analysis and chemical modeling were performed in order to characterize the gas properties and investigate the chemical origin of the emission. Results. The nonLTE radiative transfer analysis coupled with Bayesian inference shows clear evidence that the gas traced by SiO has different densities and temperatures than that traced by HNCO, with an indication that shocks are needed to produce both species. Chemical modeling further confirms such a scenario and suggests that fast and slow shocks are responsible for SiO and HNCO production, respectively, in most GMCs. We are also able to infer the physical characteristics of the shocks traced by SiO and HNCO for each GMC. Conclusions. Radiative transfer and chemical analysis of the SiO and HNCO in the CMZ of NGC 253 reveal a complex picture whereby most of the GMCs are subjected to shocks. We speculate on the possible shock scenarios responsible for the observed emission and provide potential history and timescales for each shock scenario. Observations of higher spatial resolution for these two species are required in order to quantitatively differentiate between the possible scenarios
Novel catalyst configuration to boost the yield of longer hydrocarbons from methanol-mediated CO2 hydrogenation
Get PDFVarious C1 feedstocks and lower hydrocarbons (C2-C4) can be produced from CO2 hydrogenation, which is an important way to utilize excess CO2 and provide alternative fuel options for dwindling fossil fuels. Herein, a novel two-bed catalytic system was developed to increase the yield of liquid range hydrocarbons, where the first catalytic bed was composed of In2O3-ZrO2 (13 wt. In %)/HZSM-5 and the second bed was a desilicated HZSM-5 placed downstream from the first bed. A maximum hydrocarbon selectivity was found to be about 86% with 7.2% CO2 conversion at 533 K, while conversion increased up to 19.3% with 71.2% hydrocarbon selectivity at 623 K while keeping the pressure at 4.0 MPa. The selectivity of longer liquid range hydrocarbons (C8-C12) was increased from 29.2% to 42.4% using the oligomerization process in which the produced lower olefins from the first bed were oligomerized to enhance the liquid range hydrocarbon over desilicated HZSM-5. Additionally, a comparative study was carried out to examine the effect of desilication over HZSM-5 having different silica-to-alumina ratios of 24 and 59. Moreover, detailed characterizations were carried out before and after the desilication of the HZSM-5 to correlate catalytic activities with physical and chemical properties of the catalysts. The results suggest that a two-bed catalytic system is a promising option to increase the yield of liquid range hydrocarbons from methanol-mediated CO2 hydrogenation while there was a negligible effect on CO2 conversion due to the second bed
Active Balancing of Reconfigurable Batteries Using Reinforcement Learning Algorithms
No full textIn reconfigurable batteries, series or parallel connections among cells/modules are able to be actively changed during operations. One big advantage of reconfiguration is to achieve active balancing among cells/modules. Rule-based and greedy algorithms of reconfigurable battery control have problems of being sensitive to battery characteristic variation and requiring a lot of computing resources. Therefore, deep reinforcement learning (DRL) algorithms are used to overcome these difficulties. Very few studies related to this idea have been done previously, and the studied battery reconfiguration topologies are either too simple or too complex. Thus, in this paper, a module-level reconfigurable battery with moderate flexibilities is controlled by DRL algorithms. Two neighboring modules are connected in either parallel or series by following a well-trained optimal policy. Two battery discharging cases, constant power and variable power, are simulated. The final results prove the feasibility and great potential of utilizing DRL algorithms in reconfigurable battery control
The innermost jet in the hidden ultra-luminous X-ray source Cygnus X-3
Get PDFCygnus X-3 is a high-mass X-ray binary with a compact object accreting matter from a Wolf-Rayet donor star. Recently, it has been revealed by the Imaging X-ray Polarimetry Explorer (IXPE) as a hidden Galactic ultra-luminous X-ray (ULX) source with a luminosity above the Eddington limit, along the direction of a narrow (opening angle) funnel. In between the IXPE observations, we observed Cyg X-3 with the European very long baseline interferometry (VLBI) Network at 22 GHz and the NICER X-ray instrument. To probe possible relations between the X-ray funnel and the potential radio jet from the ULX, we analysed the simultaneous multiwavelength data. Our high-resolution VLBI image reveals an elongated structure with a position angle of -3.2 \ub1 0.4 \ub0, accurately perpendicular to the direction of the linear X-ray polarization. Because Cyg X-3 was in the radio quiescent state on 2022 November 10, we identify the mas-scale structure as the innermost radio jet. The finding indicates that the radio jet propagates along and within the funnel. Moreover, the jet is marginally resolved in the transverse direction. This possibly results from the strong stellar winds and the rapid orbital motion of the binary system
Link-INVENT: generative linker design with reinforcement learning
Get PDFIn this work, we present Link-INVENT as an extension to the existing de novo molecular design platform REINVENT. We provide illustrative examples on how Link-INVENT can be applied to fragment linking, scaffold hopping, and PROTAC design case studies where the desirable molecules should satisfy a combination of different criteria. With the help of reinforcement learning, the agent used by Link-INVENT learns to generate favourable linkers connecting molecular subunits that satisfy diverse objectives, facilitating practical application of the model for real-world drug discovery projects. We also introduce a range of linker-specific objectives in the Scoring Function of REINVENT. The code is freely available at https://github.com/MolecularAI/Reinvent
Discovery of a radio jet in the Cloverleaf quasar at z = 2.56
No full textThe fast growth of supermassive black holes and their feedback to the host galaxies play an important role in regulating the evolution of galaxies, especially in the early Universe. However, due to cosmological dimming and the limited angular resolution of most observations, it is difficult to resolve the feedback from the active galactic nuclei (AGNs) to their host galaxies. Gravitational lensing, for its magnification, provides a powerful tool to spatially differentiate emission originating from AGN and host galaxy at high-redshifts. Here, we report a discovery of a jet-like radio structure in a strongly lensed starburst quasar, H1413+117 or Cloverleaf at redshift z = 2.56, based on observational data at optical, submillimetre, and radio wavelengths. With both parametric and non-parametric lens models and with reconstructed images in the source plane, we find a well-separated, kpc-scaled, single-sided radio jet located at projected to the north-west of the host galaxy in the source plane. This could indicate the co-existence of feedback from the AGN by both wind and jet in the Cloverleaf quasar
X-Ray Polarization Observations of BL Lacertae
No full textBlazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus that the synchrotron emission is responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae (BL Lac) performed with the Imaging X-ray Polarimetry Explorer, from which an upper limit to the polarization degree Π X < 12.6% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton-synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac
Approx-RM: Reducing Energy on Heterogeneous Multicore processors under Accuracy and Timing Constraints
Get PDFReducing energy consumption while providing performance and quality guarantees is crucial for computing systems ranging from battery-powered embedded systems to data centers. This paper considers approximate iterative applications executing on heterogeneous multi-core platforms under user-specified performance and quality targets. We note that allowing a slight yet bounded relaxation in solution quality can considerably reduce the required iteration count and thereby can save significant amounts of energy. To this end, this paper proposes Approx-RM, a resource management scheme that reduces energy expenditure while guaranteeing a specified performance as well as accuracy target. Approx-RMpredicts the number of iterations required to meet the relaxed accuracy target at run-time. The time saved generates execution-time slack, which allows Approx-RM to allocate fewer resources on a heterogeneous multi-core platform in terms of DVFS, core type, and core count to save energy while meeting the performance target. Approx-RMcontributes with lightweight methods for predicting the iteration count needed to meet the accuracy target and the resources needed to meet the performance target. Approx-RM uses the aforementioned predictions to allocate just enoughresources to comply with quality of service constraints to save energy. Our evaluation shows energy savings of 31.6%, on average, compared to Race-to-idle when the accuracy is only relaxed by 1%. Approx-RM incurs timing and energy overheads of less than 0.1%
