Defect-free one-handed contracted helical tubular ladder polymers with a π-electron-rich cylindrical cavity were synthesized by alkyne benzannulations of the random-coil precursor containing 6,6′-linked-1,1′-spirobiindane-7,7′-diol-based chiral monomer units. The resulting tightly-twisted showed remarkably high enantioseparation abilities toward variety hydrophobic aromatics point, axial, and p...

In positron and proton storage rings, electrons produced by photoemission, ionization, and secondary emission accumulate in the vacuum chamber during multibunch operation with close spacing. A positron or proton bunch passing through this "electron cloud" experiences a force similar to a short-range wake field. This effective wake field can cause a transverse-mode-coupling instability, if the e...

We compare experimental results with simulations of the electron cloud effect induced by a positron beam at the APS synchrotron light source at ANL, where the electron cloud effect has been observed and measured with dedicated probes. We find good agreement between simulations and measurements for reasonable values of certain secondary electron yield (SEY) parameters, most of which were extract...

Electrons generated and accumulated inside the beam pipe form an ‘electron cloud’ that interacts with a charged particle beam. If the number of electrons is sizable, this beam-cloud interaction can give rise to a two-stream instability, resulting in beam loss or emittance growth. The instability can occur within a single bunch, e.g., passing through the cloud on successive turns in a storage ri...

Clouds of low energy electrons frequently build up within the beam chambers of particle accelerators. In many cases, electron cloud effects (ECEs) cause beam instabilities and degradation of performance. This is of particular concern for high intensity positron rings, in which ECEs can lead to emittance blow-up. Understanding and mitigating electron cloud build up is thus of particular importan...

Over the past decade anion-π interaction has emerged as a new paradigm of supramolecular chemistry of anions. Taking advantage of the electronic nature of anion-π interaction, we have expanded its boundaries to charge-transfer (CT) and formal electron transfer (ET) events by adjusting the electron-donating and accepting abilities of anions and π-acids, respectively. To establish that ET, CT, an...

DFT B3LYP/6-31G(d) calculations were performed to examine the feasibility of graphene-like C42H18 and starbenzene C6(BeH)6 (SBz) polymers as ligands of 3D-extensible sandwich compounds (3D-ESCs) with uninterrupted sandwich arrays. The results revealed that sandwich compounds with three or more C42H18 ligands were not feasible. The possible reason may be the localization of π electrons on certai...