129 research outputs found
AI3SD Video: Accelerating design of organic materials with machine learning and AI
No full textDeep learning is revolutionizing many areas of science and technology, particularly in natural language processing, speech recognition, and computer vision. In this talk, we will provide an overview of the latest developments of machine learning and AI methods and application to the problem of drug discovery and development at Isayev’s Lab at CMU. We identify several areas where existing methods have the potential to accelerate materials research and disrupt more traditional approaches. First we will present a deep learning model that approximates the solution of Schrodinger equation. We introduce the AIMNet-NSE (Neural Spin Equilibration) architecture, which can predict molecular energies for an arbitrary combination of molecular charge and spin multiplicity. The AIMNet-NSE model allows to fully bypass QM calculations and derive the ionization potential, electron affinity, and conceptual Density Functional Theory quantities like electronegativity, hardness, and condensed Fukui functions. We show that these descriptors, along with learned atomic representations, could be used to model chemical reactivity through an example of regioselectivity in electrophilic aromatic substitution reactions. Second, we proposed a novel ML-guided materials discovery platform that combines synergistic innovations in automated flow synthesis and automated machine learning (AutoML) method development. A software-controlled, continuous polymer synthesis platform enables rapid iterative experimental–computational cycles that resulted in the synthesis of hundreds of unique copolymer compositions within a multi-variable compositional space. The non-intuitive design criteria identified by ML, which was accomplished by exploring less than 0.9% of overall compositional space, upended conventional wisdom in the design of 19F MRI agents and led to the identification of >10 copolymer compositions that outperformed state-of-the-art materials
Italy before the Romans
No full textThis is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordItaly, before Rome took leadership of the peninsula, hosted multiple cultures, languages, community forms, and powerful hubs. These linked into different sectors of the network that stretched across the Mediterranean and to the north. This chapter explores what this diversity entailed and traces the transformations that led to the eventual demise of a multi-polar Italy. In so doing it questions the model of regional cohesion for the early history of the peninsula, which breaks down once sites are considered individually and as part of wider networks than the territorial perspective allows. Material culture is essential to gain an understanding of what was distinctive and shared between groups that developed city-states and others that preferred a more diffuse settlement pattern. It also makes visible the agency of sectors of society that are under-represented, such as women. A key underlying theme is the extent to which the changes were triggered by internal and external forces. This chapter will consider what fueled growth and centralization; the role played by supra-community structures and by institutions such as mercenaries, the system of guest friendship, and large rural sanctuary sites. Through such an exploration it looks at how competing models succumbed to the forces of cohesion, of which Rome was as much a product as a contributor
Actual problems of studying of history of Kursk fight
No full textIn article the author addresses to debatable problems of a domestic and foreign historiography of fight near Kursk, pushes together opinions of military historians with memoirs certificates and estimates of battles of World War II of commanders confronting on fields, refers to new documents, defending the judgments. In the author's description of events near Kursk the specified panorama of all military 1943 and its place in the Great Victory of the 1945th open
Сверхтекучие состояния с конечным импульсом куперовских пар в ядерной материи
No full textSuperfluid states of symmetric nuclear matter with finite total momentum of Cooper pairs (nuclear LOFF phase) are studied with the use of Fermi–liquid theory in the model with Skyrme effective forces. It is considered the case of four–fold splitting of the excitation spectrum due to finite superfluid momentum and coupling of T = 0 and T = 1 pairing channels. It has been shown that at zero temperature the energy gap in triplet–singlet (TS) pairing channel (in spin and isospin spaces) for the SkM∗ force demonstrates double–valued behavior as a function of superfluid momentum. As a consequence, the phase transition at the critical superfluid momentum from the LOFF phase to the normal state will be of a first order. Behavior of the energy gap as a function of density for TS pairing channel under increase of superfluid momentum changes from one–valued to universal two–valued. It is shown that two–gap solutions, describing superposition of states with singlet–triplet (ST) and TS pairing of nucleons appear as a result of branching from one–gap ST solution. Comparison of the free energies shows that the state with TS pairing of nucleons is thermodynamically most preferable.The author is grateful for discussions a nd useful comments to S. Peletminsky, G. Roepke, H.-J. Schulze and A. Yatsenko. The financial support of STCU (grant No. 1480) is acknowledged
Сверхтекучие состояния с конечным импульсом куперовских пар в ядерной материи
No full textSuperfluid states of symmetric nuclear matter with finite total momentum of Cooper pairs (nuclear LOFF phase) are studied with the use of Fermi–liquid theory in the model with Skyrme effective forces. It is considered the case of four–fold splitting of the excitation spectrum due to finite superfluid momentum and coupling of T = 0 and T = 1 pairing channels. It has been shown that at zero temperature the energy gap in triplet–singlet (TS) pairing channel (in spin and isospin spaces) for the SkM∗ force demonstrates double–valued behavior as a function of superfluid momentum. As a consequence, the phase transition at the critical superfluid momentum from the LOFF phase to the normal state will be of a first order. Behavior of the energy gap as a function of density for TS pairing channel under increase of superfluid momentum changes from one–valued to universal two–valued. It is shown that two–gap solutions, describing superposition of states with singlet–triplet (ST) and TS pairing of nucleons appear as a result of branching from one–gap ST solution. Comparison of the free energies shows that the state with TS pairing of nucleons is thermodynamically most preferable.The author is grateful for discussions a nd useful comments to S. Peletminsky, G. Roepke, H.-J. Schulze and A. Yatsenko. The financial support of STCU (grant No. 1480) is acknowledged
Сверхтекучие состояния с конечным импульсом куперовских пар в ядерной материи
No full textSuperfluid states of symmetric nuclear matter with finite total momentum of Cooper pairs (nuclear LOFF phase) are studied with the use of Fermi–liquid theory in the model with Skyrme effective forces. It is considered the case of four–fold splitting of the excitation spectrum due to finite superfluid momentum and coupling of T = 0 and T = 1 pairing channels. It has been shown that at zero temperature the energy gap in triplet–singlet (TS) pairing channel (in spin and isospin spaces) for the SkM∗ force demonstrates double–valued behavior as a function of superfluid momentum. As a consequence, the phase transition at the critical superfluid momentum from the LOFF phase to the normal state will be of a first order. Behavior of the energy gap as a function of density for TS pairing channel under increase of superfluid momentum changes from one–valued to universal two–valued. It is shown that two–gap solutions, describing superposition of states with singlet–triplet (ST) and TS pairing of nucleons appear as a result of branching from one–gap ST solution. Comparison of the free energies shows that the state with TS pairing of nucleons is thermodynamically most preferable.The author is grateful for discussions a nd useful comments to S. Peletminsky, G. Roepke, H.-J. Schulze and A. Yatsenko. The financial support of STCU (grant No. 1480) is acknowledged
FINITE TEMPERATURE EFFECTS ON SPIN POLARIZATION OF NEUTRON MATTER IN A STRONG MAGNETIC FIELD
No full textMagnetars are neutron stars possessing a magnetic field of about 1014-1015 G at the surface. Ther-modynamic properties of neutron star matter, approximated by pure neutron matter, are considered at finite temperature in strong magnetic fields up to 1018 G which could be relevant for the inner regions of magnetars. In the model with the Skyrme effective interaction, it is shown that a thermodynami-cally stable branch of solutions for the spin polarization parameter corresponds to the case when the majority of neutron spins are oriented opposite to the direction of the magnetic field (i.e. negative spin polarization). Moreover, starting from some threshold density, the self-consistent equations have also two other branches of solutions, corresponding to positive spin polarization. The influence of finite temperatures on spin polarization remains moderate in the Skyrme model up to temperatures relevant for protoneutron stars. In particular, the scenario with the metastable state characterized by positive spin polarization, considered at zero temperature in Phys. Rev. C 80, 065801 (2009), is preserved at finite temperatures as well. It is shown that, above certain density, the entropy for various branches of spin polarization in neutron matter with the Skyrme interaction in a strong magnetic field shows the unusual behavior, being larger than that of the nonpolarized state. By providing the correspondin
Migration, mobility and place in ancient Italy
No full textThis is the author accepted manuscript. The final version is available from Cambridge University Press via the DOI in this recordIdeas of mass migration are crucial to the understanding of our globally-linked 21st century world. But the phenomenon is far from being uniquely modern. The ancient world too was born from patterns of extensive movements of people, some of them en masse. This book, focusing on ancient Italy, will challenge prevailing conceptions of a natural tie to the land and a demographically settled world. Drawing on research in literary and political texts, demographic studies, epigraphy and archaeological findings, it will argue that the combined evidence suggests that much human mobility in the last millennium BC was ongoing and cyclical: places acted as pauses for those on the move, rather than being chosen as permanent abodes. In Italy, it was not until the 1st century BC that the Roman Imperium began to fix identity and a sense of belonging to the site of Rome, giving a special significance to physical presence and the soil itself. Yet even these changes did not lead to a territorialising outlook either in terms of belonging, or imperial ambitions. Permeable boundaries and multiple fluid identities continued to be accommodated within the new state mechanisms. In developing the argument the study takes issue with some contemporary concepts in migration and post-colonial discourse and employs the ideas of modern theorists of place and identity, such as Massey, Harvey, and De Certeau. One of the claims of this work is that, in the ancient Italian context, xenophobia is difficult to identify, and outside of the military context ‘the foreigner in our midst’ was not regarded as a problem. Boundaries of status rather than of geopolitics were the ones that were difficult to cross. The material covered in this study includes the stories of individuals and migrant groups, itinerant soldiers, traders, wives, hostages, settlements, expulsions, the founding and demolition of sites, and the political processes that could both encourage and discourage the transfer of peoples from one place to another. This is the story of people as well as states
Data and codes behind "Crowdsourced mapping of unexplored target space of kinase inhibitors"
No full textThis repository contains the data underlying the figures in the journal publication describing the IDG-DREAM Drug Kinase Binding Prediction Challenge [1] as well as archives of the two following GitHub repositories:
IDG-DREAM-Challenge-Analysis-ncomms.zip (https://github.com/Sage-Bionetworks/IDG-DREAM-Challenge-Analysis): codes for reproducing the analyses described in [1]; licence Apache 2.0.
IDG-DREAM-Drug-Kinase-Challenge-ncomms.zip (https://github.com/Sage-Bionetworks/IDG-DREAM-Drug-Kinase-Challenge): codes used for the Challenge scoring; licence Apache 2.0.
References
[1] Cichońska A, Ravikumar B, Allaway RJ, Wan F, Park S, Isayev O, Li S, Mason M, Lamb A, Tanoli Z, Jeon M, Kim S, Popova M, Capuzzi S, Zeng J, Dang K, Koytiger G, Kang J, Wells CI, Willson TM, The IDG-DREAM Drug-Kinase Binding Prediction Challenge Consortium, Oprea TI, Schlessinger A, Drewry DH, Stolovitzky G, Wennerberg K, Guinney J, Aittokallio T. Crowdsourced mapping of unexplored target space of kinase inhibitors. Nature Communications 2021
Ultrasound devulcanization of unfilled natural rubber networks, studied via component molecular mobility
No full text13C NMR solids spectroscopy and transverse relaxation, and 1H relaxation and pulsed-gradient spin-echo self-diffusion measurements at 70 °C were used to study molecular and segmental mobilities in natural rubber before and after sulfur crosslinking, and after subsequent devulcanization using intense ultrasound. NMR relaxation does not clearly distinguish between entangled and crosslinked network mobility, but unentangled sol and oligomeric species are separable within the longer T2 decay components. Ultrasound reactor settings affect the amount of extractable sol generated. Some two-thirds of the sol is entangled, with number-average molecular weights (Mn) above 10 000 g mol−1. Samples also contain near 2 wt% of inert light species (Mn \u3c 400 g mol−1); ultrasound is relatively ineffective in producing additional oligomeric material. All proton mobilities increase as more sol is produced, but 13C relaxation, reflecting intramolecular effects, indicates a slight decrease in backbone mobility. In contrast with other rubbers, in natural rubber, neither the glass transition nor the sol diffusion rate is greatly affected by the extent of ultrasound exposure. Comparisons with previous similar work of this laboratory, particularly styrene-butadiene rubber, are useful in confirming the molecular mechanisms involved
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