Kiyohara, S., Miyata, T. & Mizoguchi, T. Prediction of grain boundary structure and energy by machine learning arXiv:1512.03502 (2015). Tschopp, M. A. & McDowell, D. L. Structural unit and faceting description of Sigma 3 asymmetric tilt grain boundaries. J. Mater. Sci. 42, 7806–7811 (2007). Srivastava, N.; Mansimov, E.; Salakhutdinov, R. Unsupervised learning of video representations using LSTMs. In Proceedings of the 32nd International Conference on International Conference on Machine Learning—Volume 37; JMLR.org: Lille, France, 2015; pp. 843–852. [ Google Scholar] So, if an "up quark" can become a "down quark" by emitting an electron and an antineutrino, thereby changing its charge and mass, it sure looks like there is something more "fundamental" than quarks, which would also includes the makings of the leptons. See https://en.wikipedia.org/wiki/Preon . Preons, also called "partons" do not seem to currently be in-favor with theorists. The Higgs boson seems to be their answer to why partons are unnecessary. But, the models are still "incomplete" (as in don't explain everything).

The atoms of the elements found in the human body have from one to five electron shells, and all electron shells hold eight electrons except the first shell, which can only hold two. This configuration of electron shells is the same for all atoms. The precise number of shells depends on the number of electrons in the atom. Hydrogen and helium have just one and two electrons, respectively. If you take a look at the periodic table of the elements, you will notice that hydrogen and helium are placed alone on either sides of the top row; they are the only elements that have just one electron shell ( Figure 2.7). A second shell is necessary to hold the electrons in all elements larger than hydrogen and helium. When an atom does not contain equal numbers of protons and electrons, it is called an ion. Because the number of electrons does not equal the number of protons, each ion has a net charge. Positive ions are formed by losing electrons and are called cations. Negative ions are formed by gaining electrons and are called anions.The conditions under which two atoms will bond together depend on the atoms’ electron configurations, which completely determine their chemical reactivity. The more stable the electron configuration, the less reactive the atom; the extremes of stability are the ‘inert gases’, such as argon, helium and neon, which are almost totally non-reactive. Their near-inertness is caused by their having complete outermost electron orbitals, with no opportunity for more electrons to ‘join’ the atom, and no ‘spare’ or ‘loose’ electrons to leave the atom. Given that hydrogen is by far the most common element (or molecule) in the universe, and since hydrogen nuclei are just single protons, then suffice it to say the science of protons can teach us much about the distribution of matter and the violent mechanisms that drive some of the most energetic phenomena in the cosmos.

Photograph of Ernest Rutherford and Hans Geiger with their alpha particle counting apparatus. (Image credit: Science & Society Picture Library via Getty Images) Nicolaou, C.A.; Kannas, C.; Loizidou, E. Multi-Objective Optimization Methods in De Novo Drug Design. Mini-Rev. Med. Chem. 2012, 12, 979–987. [ Google Scholar] [ CrossRef] [ PubMed] Wang, Y.; Zhao, H.; Brewer, J.T.; Li, H.; Lao, Y.; Amberg, W.; Behl, B.; Akritopoulou-Zanze, I.; Dietrich, J.; Lange, U.E.W.; et al. De Novo Design, Synthesis, and Biological Evaluation of 3,4-Disubstituted Pyrrolidine Sulfonamides as Potent and Selective Glycine Transporter 1 Competitive Inhibitors. J. Med. Chem. 2018, 61, 7486–7502. [ Google Scholar] [ CrossRef] Thus, in these first two cases, we see that the LER approach discovers well-known, and physically important structures or defects that are commonly identified in metallic structures. Perhaps even more interesting is the second LAE in Fig. 5b, which has the highest relative importance of all (≈9%). The centro-symmetry parameter (CSP) for the atom at the center of the LAE is 0.125, or close to a perfectly structured FCC lattice, as visual inspection of the LAE would suggest. However, the CSP cannot be directly compared with the LAE because CSP examines only nearest neighbors while the LAE encompasses a larger environment, including the defect at the edge of the LAE. 47 Most importantly, this structure may not be immediately identified with any known metallic defect, but we know that it is highly correlated with thermally activated mobility across all the GBs in the data set.Bartók, A. P., Payne, M. C., Kondor, R. & Csányi, G. Gaussian approximation potentials: the accuracy of quantum mechanics, without the electrons. Phys. Rev. Lett. 104, 136403 (2010). Protons are also vital in the core of the sun where the energy that manifests as the light and heat of the sun is generated via a mechanism known as the proton-proton chain. (Image credit: cokada via Getty Images) Cahn, J. W., Mishin, Y. & Suzuki, A. Coupling grain boundary motion to shear deformation. Acta Mater. 54, 4953–4975 (2006).

Chan, H.C.S.; Shan, H.; Dahoun, T.; Vogel, H.; Yuan, S. Advancing Drug Discovery via Artificial Intelligence. Trends Pharmacol. Sci. 2019, 40, 592–604. [ Google Scholar] [ CrossRef]An atom is the smallest quantity of an element that retains the unique properties of that element. In other words, an atom of hydrogen is a unit of hydrogen—the smallest amount of hydrogen that can exist. As you might guess, atoms are almost unfathomably small. The period at the end of this sentence is millions of atoms wide. Atomic Structure and Energy