Tracking an Untracked Space Debris After an Inelastic Collision Using Physics Informed Neural Network

With the sustained rise in satellite deployment in Low Earth Orbits, the collision risk from untracked space debris is also increasing. Often small-sized space debris (below 10 cm) are hard to track using the existing state-of-the-art methods. However, knowing such space debris' trajectory is crucial to avoid future collisions. We present a Physics Informed Neural Network (PINN) - based approach for estimation of the trajectory of space debris after a collision event between active satellite and space debris. In this work, we have simulated 8565 inelastic collision events between active satellites and space debris. Using the velocities of the colliding objects before the collision, we calculate the post-collision velocities and record the observations. The state (position and velocity), coefficient of restitution, and mass estimation of un-tracked space debris after an inelastic collision event along with the tracked active satellite can be posed as an optimization problem by observing the deviation of the active satellite from the trajectory. We have applied the classical optimization method, the Lagrange multiplier approach, for solving the above optimization problem and observed that its state estimation is not satisfactory as the system is under-determined. Subsequently, we have designed Deep Neural network-based methods and Physics Informed Neural Network (PINN )based methods for solving the above optimization problem. We have compared the performance of the models using root mean square error (RMSE) and interquartile range of the predictions. It has been observed that the PINN-based methods provide a better prediction for position, velocity, mass and coefficient of restitution of the space debris compared to other methods.Comment: 23 pages, 18 figures (consolidated into 13 figures by using sub-figures), accepted as a journal paper by Nature Scientific Repor

Surface Transitions for Confined Associating Mixtures

Thin films of binary mixtures that interact through isotropic forces and directionally specific "hydrogen bonding" are considered through Monte Carlo simulations. We show, in good agreement with experiment, that the single phase of these mixtures can be stabilized or destabilized on confinement. These results resolve a long standing controversy, since previous theories suggest that confinement only stabilizes the single phase of fluid mixtures.Comment: LaTeX document, documentstyle[aps,preprint]{revtex}, psfig.sty, bibtex, 13 pages, 4 figure

Mechanisms of Directional Polymer Crystallization

Zone annealing, a directional crystallization technique originally used for the purification of semiconductors, is applied here to crystalline polymers. Tight control over the final lamellar orientation and thickness of semicrystalline polymers can be obtained by directionally solidifying the material under optimal conditions. It has previously been postulated by Lovinger and Gryte that, at steady state, the crystal growth rate of a polymer undergoing zone annealing is equal to the velocity at which the sample is drawn through the temperature gradient. These researchers further implied that directional crystallization only occurs below a critical velocity, when crystal growth rate dominates over nucleation. Here, we perform an analysis of small-angle X-ray scattering, differential scanning calorimetry, and cross-polarized optical microscopy of zone-annealed poly(ethylene oxide) to examine these conjectures. Our long period data validate the steady-state ansatz, while an analysis of Herman's orientation function confirms the existence of a transitional region around a critical velocity, v(crit), where there is a coexistence of oriented and isotropic domains. Below v(crit), directional crystallization is achieved, while above v(crit), the mechanism more closely resembles that of conventional isotropic isothermal crystallization.This work was supported by grants DE-SC0018182, DE-SC0018135, and DE-SC0018111, funded by the U.S. Department of Energy, Office of Science. A.A.K. acknowledges funding from the Gates Millennium Scholars program under Grant No. OPP1202023 from the Bill & Melinda Gates Foundation. A.J.M. acknowledges funding from the Basque Government through grant IT1309-19. We are grateful to Dr. Andrew J. Lovinger for critically reviewing the manuscript and offering multiple comments that have helped us to significantly improve our paper. We would also like to thank Beatrice Bellini for experimental assistance

Soft matter roadmap

Soft materials are usually defined as materials made of mesoscopic entities, often self-organised, sensitive to thermal fluctuations and to weak perturbations. Archetypal examples are colloids, polymers, amphiphiles, liquid crystals, foams. The importance of soft materials in everyday commodity products, as well as in technological applications, is enormous, and controlling or improving their properties is the focus of many efforts. From a fundamental perspective, the possibility of manipulating soft material properties, by tuning interactions between constituents and by applying external perturbations, gives rise to an almost unlimited variety in physical properties. Together with the relative ease to observe and characterise them, this renders soft matter systems powerful model systems to investigate statistical physics phenomena, many of them relevant as well to hard condensed matter systems. Understanding the emerging properties from mesoscale constituents still poses enormous challenges, which have stimulated a wealth of new experimental approaches, including the synthesis of new systems with, e.g. tailored self-assembling properties, or novel experimental techniques in imaging, scattering or rheology. Theoretical and numerical methods, and coarse-grained models, have become central to predict physical properties of soft materials, while computational approaches that also use machine learning tools are playing a progressively major role in many investigations. This Roadmap intends to give a broad overview of recent and possible future activities in the field of soft materials, with experts covering various developments and challenges in material synthesis and characterisation, instrumental, simulation and theoretical methods as well as general concepts

A comparison of different modes of pneumatic compression on muscle tissue oxygenation: an intraparticipant, randomised, controlled volunteer study

Intermittent pneumatic compression (IPC) to the lower limbs is widely used as a mechanical means to prevent deep vein thrombosis in hospitalised patients. Due to a theoretical concern about impairing blood flow, thromboembolic-deterrent stockings and IPC are considered contraindicated for patients with peripheral vascular diseases by some clinicians. This study assessed whether IPC would alter peripheral limb muscle tissue oxygenation (StO ), and whether such changes were different during 10 minutes of sequential and single-compartment compressions. Twenty volunteers were randomised to have their left or right arm treated with a sequential or single-compartment IPC for 10 minutes, using the contralateral arm without compression as an intraparticipant control. After a five-minute wash-out period, the procedure was repeated on the same arm using the alternative mode of IPC. Both hands’ thenar muscles StO was monitored every two\ua0minutes for 10\ua0minutes using the same near-infrared spectroscopy StO monitor. Both sequential (3.5%, 95% confidence intervals (CI) 2.7–4.2; p < 0.001) and single-compartment IPC (1.6%, 95% CI 0.4–2.8; p = 0.039) significantly increased muscle StO within 10 minutes compared to no compression; and the increments were higher during sequential compressions compared to during single-compartment compressions (2.1%, 95% CI 0.7–3.5; p = 0.023). This mechanistic study showed that both modes of IPC increased upper limb muscle StO compared to no compression, but the StO increments were higher with the multiple-chamber sequential compressions mode. Contrary to the theoretical concern that IPC may impair peripheral limb tissue oxygenation, our results showed that IPC actually increases oxygenation of the peripheral limb muscles, especially during the sequential compressions mode

http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-76543 Modeling of Molecular Interaction between Apoptin, BCR-Abl and CrkL- An Alternative Approach to Conventional Rational Drug Design

In this study we have calculated a 3D structure of apoptin and through modeling and docking approaches, we show its interaction with Bcr-Abl oncoprotein and its downstream signaling components, following which we confirm some of the newly-found interactions by biochemical methods. Bcr-Abl oncoprotein is aberrantly expressed in chronic myelogenous leukaemia (CML). It has several distinct functional domains in addition to the Abl kinase domain. The SH3 and SH2 domains cooperatively play important roles in autoinhibiting its kinase activity. Adapter molecules such as Grb2 and CrkL interact with proline-rich region and activate multiple Bcr-Abl downstream signaling pathways that contribute to growth an

Aerosol radiative forcing during clear, hazy, and foggy conditions over a continental polluted location in north India

From the simultaneous measurements of aerosol optical, physical, and chemical characteristics over Hisar, a semiurban location in northern India, aerosol radiative (shortwave (SW), longwave (LW), and net) forcings are estimated using a radiative transfer model. The submicron aerosol mass concentrations are found to be similar, while the supermicron mass concentrations on hazy and foggy days are found to be higher than those found during clear days. Aerosol optical depths are found to be high on foggy days, and they decrease on hazy and clear days. Black carbon (BC) aerosol mass concentration is found to be low during clear and hazy periods and increases by about a factor of 5 during foggy days. Single-scattering albedo (&#969;) values at 0.5 &#181;m are found to be 0.88, 0.86, and 0.76 for clear, hazy, and foggy conditions, quite in agreement with varying BC amounts. The &#969; values over Hisar are found to exhibit close correspondence with &#969; derived from other locations in India in winter. SW atmospheric (ATM) forcing is found to increase from 16 W m-2 during clear periods to 49 W m-2 for foggy days. LW cooling of the ATM increases from about -2 W m-2 for clear conditions to about -3 W m-2 during foggy periods. LW ATM forcings are found to contribute 11-14% to the net ATM forcing. As the LW ATM forcings are negative, they partially cancel the large SW ATM warmings. Sensitivity study shows that LW ATM cooling becomes more prominent with an increase in the amount of absorbing aerosols and decrease in water vapor, while LW forcings are found to vary only by 1% for differing ozone amounts