Clock with 8×10^{-19} Systematic Uncertainty.

We report an optical lattice clock with a total systematic uncertainty of 8.1×10^{-19} in fractional frequency units, representing the lowest uncertainty of any clock to date. The clock relies on interrogating the ultranarrow ^{1}S_{0}→^{3}P_{0} transition in a dilute ensemble of fermionic strontium atoms trapped in a vertically-oriented, shallow, one-dimensional optical lattice.

Long-Lived Coherence on a μHz Scale Optical Magnetic Quadrupole Transition.

We report on the coherent excitation of the ultranarrow ^{1}S_{0}-^{3}P_{2} magnetic quadrupole transition in ^{88}Sr. By confining atoms in a state insensitive optical lattice, we achieve excitation fractions of 97(1)% and observe linewidths as narrow as 58(1) Hz. With Ramsey spectroscopy, we find coherence times of 14(1) ms, which can be extended to 266(36) ms using a spin-echo sequence.

Prospects of a thousand-ion Sn Coulomb-crystal clock with sub-10 inaccuracy.

Optical atomic clocks are the most accurate and precise measurement devices of any kind, enabling advances in international timekeeping, Earth science, fundamental physics, and more. However, there is a fundamental tradeoff between accuracy and precision, where higher precision is achieved by using more atoms, but this comes at the cost of larger interactions between the atoms that limit the accuracy. Here, we propose a many-ion optical atomic clock based on three-dimensional Coulomb crystals of order one thousand Sn ions confined in a linear RF Paul trap with the potential to overcome this limitation.

Opportunities for fundamental physics research with radioactive molecules.

Molecules containing short-lived, radioactive nuclei are uniquely positioned to enable a wide range of scientific discoveries in the areas of fundamental symmetries, astrophysics, nuclear structure, and chemistry. Recent advances in the ability to create, cool, and control complex molecules down to the quantum level, along with recent and upcoming advances in radioactive species production at several facilities around the world, create a compelling opportunity to coordinate and combine these efforts to bring precision measurement and control to molecules containing extreme nuclei. In this manuscript, we review the scientific case for studying radioactive molecules, discuss recent atomic, molecular, nuclear, astrophysical, and chemical advances which provide the foundation for their study, describe the facilities where these species are and will be produced, and provide an outlook for the future of this nascent field.

[Neurodynamic speech disorders in the acute ischemic stroke].

Objective: To identify the features of the clinical picture and evaluate the dynamics of regression of neurodynamic speech disorders in comparison with cortical aphasia in patients with ischemic stroke (IS) in the carotid system.

Material And Methods: We examined 268 patients with a median age of 59 (54; 70) years in the acute period of IS in the dominant hemisphere with the presence of cortical aphasia or neurodynamic speech disorders. The degree of speech recovery was characterized by an increase in the score on the Speech Questionnaire (ΔSQ) from 1 to 21 days after the development of IS.