Overcoming a Radical Polarity Mismatch in Strain-Release Pentafluorosulfanylation of [1.1.0]Bicyclobutanes: An Entryway to Sulfone- and Carbonyl-Containing SF5-Cyclobutanes.

The first assortment of achiral pentafluorosulfanylated cyclobutanes (SF5-CBs) are now synthetically accessible through strain-release functionalization of [1.1.0]bicyclobutanes (BCBs) using SF5Cl. Methods for both chloropentafluorosulfanylation and hydropentafluorosulfanylation of sulfone-based BCBs are detailed herein, as well as proof-of-concept that the logic extends to tetrafluoro(aryl)sulfanylation, tetrafluoro(trifluoromethyl)sulfanylation, and three-component pentafluorosulfanylation reactions. The methods presented enable isolation of both syn and anti isomers of SF5-CBs, but we also demonstrate that this innate selectivity can be overridden in chloropentafluorosulfanylation; that is, an anti-stereoselective variant of SF5Cl addition across sulfone-based BCBs can be achieved by using inexpensive copper salt additives. Considering the SF5 group and CBs have been employed individually as nonclassical bioisosteres, structural aspects of these unique SF5-CB "hybrid isosteres" were then contextualized using SC-XRD. From a mechanistic standpoint, chloropentafluorosulfanylation ostensibly proceeds through a curious polarity mismatch addition of electrophilic SF5 radicals to the electrophilic sites of the BCBs. Upon examining carbonyl-containing BCBs, we also observed rare instances whereby radical addition to the 1-position of a BCB occurs. The nature of the key C(sp3)-SF5 bond formation step - among other mechanistic features of the methods we disclose - was investigated experimentally and with DFT calculations. Lastly, we demonstrate compatibility of SF5-CBs with various downstream functionalizations.

Investigating the effect of density variation on pitch angle scattering events of runaway electrons as observed through electron cyclotron emission diagnostic at Aditya-upgrade tokamak.

Nascent observations about the influence of kinetic instabilities on electron cyclotron emission (ECE) from runaway electrons (REs) have been detected and explored at the Aditya-Upgrade (Aditya-U) tokamak. The developed broadband ECE radiometer system offers wideband measurements by integrating several radio frequency units with a fixed intermediate frequency receiver with multiple channels, which is a novel approach to meet the needs of the localized measurements at various toroidal fields and extend the system dynamic range. The low density (ne ≤ 1 × 10-19 m-3) plasma discharges at Aditya-U are consistently accompanied by a 20%-40% increase in the ECE radiometer signal amplitude within 100 µs and sporadic step-like modulations. The Pitch Angle Scattering (PAS) of REs induced by kinetic instabilities is a potential candidate for their occurrence. This steep jump in the radiometer signals was detected due to its high temporal resolution of 10 µs. A "PREDICT" code that employs the relativistic test particle model validates these experimental findings of the radiometer diagnostic for the first time for Aditya-U tokamak. Preliminary observations of the ECE radiometer signals also show that additional gas puffs can be used to vary the trigger timings of such PAS events or even lead to their complete avoidance.

A neural code for egocentric spatial maps in the human medial temporal lobe.

Spatial navigation and memory rely on neural systems that encode places, distances, and directions in relation to the external world or relative to the navigating organism. Place, grid, and head-direction cells form key units of world-referenced, allocentric cognitive maps, but the neural basis of self-centered, egocentric representations remains poorly understood. Here, we used human single-neuron recordings during virtual spatial navigation tasks to identify neurons providing a neural code for egocentric spatial maps in the human brain. Consistent with previous observations in rodents, these neurons represented egocentric bearings toward reference points positioned throughout the environment. Egocentric bearing cells were abundant in the parahippocampal cortex and supported vectorial representations of egocentric space by also encoding distances toward reference points. Beyond navigation, the observed neurons showed activity increases during spatial and episodic memory recall, suggesting that egocentric bearing cells are not only relevant for navigation but also play a role in human memory.

Theta and Alpha Oscillations Are Traveling Waves in the Human Neocortex.

Human cognition requires the coordination of neural activity across widespread brain networks. Here, we describe a new mechanism for large-scale coordination in the human brain: traveling waves of theta and alpha oscillations. Examining direct brain recordings from neurosurgical patients performing a memory task, we found contiguous clusters of cortex in individual patients with oscillations at specific frequencies within 2 to 15 Hz. These oscillatory clusters displayed spatial phase gradients, indicating that they formed traveling waves that propagated at ∼0.25-0.75 m/s. Traveling waves were relevant behaviorally because their propagation correlated with task events and was more consistent when subjects performed the task well. Human traveling theta and alpha waves can be modeled by a network of coupled oscillators because the direction of wave propagation correlated with the spatial orientation of local frequency gradients. Our findings suggest that oscillations support brain connectivity by organizing neural processes across space and time.