This study uses over 2 years of 16 Hz density measurements, 50 Hz magnetic field data and ROTI data from the Swarm mission to perform long term statistics of plasma structuring in the polar ionosphere. The timeframe covers more than 2 years near the 24th solar cycle peak. We additionally use 3 years of data obtained from a timeframe close to solar minimum for discussion. We present power spectral ...

Herein, we report the direct carboxylation of unactivated secondary alkyl bromides enabled by the merger of photoredox and nickel catalysis, a previously inaccessible endeavor in the carboxylation arena. Site-selectivity is dictated by a kinetically controlled insertion of CO₂ at the initial C(sp³ )−Br site by the rapid formation of Ni(I)−alkyl species, thus avoiding undesired ...

This review covers the latest developments in the synthesis of cryptophane host molecules since the publication of the last extensive review by Brotin and Dutasta in 2009. The literature has been categorized according to the synthetic method for generating the cryptophane core and we also emphasize emerging late-stage functionalization approaches. The synthetic strategies towards cryptophanes ...

Questions - Analysing how multiple facets of biodiversity vary across space and time can help to predict the vulnerability of mountaintop floras to future environmental changes. Here we addressed the following questions: (a) Are elevational patterns of mountaintop plant diversity consistent across taxonomy, function and phylogeny? (b) How have the taxonomic, functional and phylogenetic dimensions ...

Multiple ice age cycles spanning the last three million years have fundamentally transformed the Arctic landscape. The cadence, intensity and pattern of this glacial modification underpin the stability of Arctic geosystems over geologic time scales, including its hydrology, circulation patterns, slope stability, hydrocarbon fluid flow, geochemical/sediment cycling and nutrient supply. The Barents ...

Wavelets and multiwavelets have lately been adopted in quantum chemistry to overcome challenges presented by the two main families of basis sets: Gaussian atomic orbitals and plane waves. In addition to their numerical advantages (high precision, locality, fast algorithms for operator application, linear scaling with respect to system size, to mention a few), they provide a framework that narrows ...

The boracarboxylation reaction has potential for the production of natural products and drug candidates, but the development of an asymmetric version of this transformation is challenging. We report an enantioselective boracarboxylation of styrenes, enabled by a copper catalyst containing chiral phosphines. Our experimental conditions provide yields between 31–76% and enantiomeric ratios from ...

High latitude ionospheric density structures such as polar cap patches and arcs are capable of deflecting high frequency (HF) radio waves to off‐great circle paths, and are likely detrimental to technologies dependent on HF radio propagation. In this study, nearly 2.5 years of 4.6–14.4 MHz data from a multi‐frequency HF radio link between Qaanaaq, Greenland and Alert, Canada are used to investigate ...

We study the problem of how many different sum of squares decompositions a general polynomial <i>f</i> with SOS-rank <i>k</i> admits. We show that there is a link between the variety SOS_<i>k</i>(<i>f</i>) of all SOS-decompositions of <i>f</i> and the orthogonal group O(<i>k</i>). We exploit this connection to obtain the dimension of SOS_<i>k</i>(<i>f</i>) and show that its degree ...