Can even-membered liquid crystal dimers exhibit the twist-bend nematic phase? The preparation and properties of disulphide and thioether linked dimers

Publisher Copyright: © 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.Peer reviewedPublisher PD

Tailoring amide N-substitution to direct liquid crystallinity in benzanilide-based dimers

Publisher Copyright: © 2023 The AuthorsPeer reviewedPublisher PD

Photo-driven effects in twist-bend nematic phases : dynamic and memory response of liquid crystalline dimers

AMF would like to acknowledge the Scottish Government and the Royal Society of Edinburgh, for the award of one SAPHIRE project, the Carnegie Trust for the Universities of Scotland, for the award of the RIG008586 project, the Royal Society, for the Research Grant RGS\R1\201397, and the Royal Society of Chemistry, for the award of the mobility grant M19-0000. AMF and AK would also like to acknowledge the Carnegie Trust for the Universities of Scotland, for the award of one Carnegie Trust Vacation Scholarships. All authors would like to thank the School of Engineering and the Department of Chemistry of the University of Aberdeen, for financial support.Peer reviewedPostprin

Helical phases assembled from achiral molecules : Twist-bend nematic and helical filamentary B4 phases formed by mesogenic dimers

Funding Information: National Science Centre (Poland) under the grant no. 2016/22/A/ST5/00319. Special acknowledgement and thanks to professor Dong Ki Yoon's group for providing the AAO membranes.Peer reviewedPublisher PD

Liquid crystal dimers and the twist-bend nematic phase: on the role of spacers and terminal alkyl chains.

The synthesis and characterisation of four series of liquid crystal dimers based on benzylideneaniline mesogenic units, and in which the lengths of terminal alkyloxy chains are varied are reported. The series differ in terms of their flexible spacers, namely, heptamethylene, nonamethylene, hexyloxy, and oxypentyloxy chains. The heptamethylene- and nonamethylene-linked dimers both show conventional nematic, N, and twist-bend nematic, NTB, phases with short terminal chains, and smectic behaviour emerges on increasing terminal chain length. This is attributed to increased molecular inhomogeneity driving microphase separation. The dimers containing the shorter heptamethylene spacer show a smectic A phase whereas those with the longer nonamethylene spacer exhibit an anticlinic smectic C phase. Smectic behaviour is not observed for the dimers containing either a hexyloxy spacer which exhibit nematic and twist-bend nematic phases, or with an oxypentyloxy spacer which show only a conventional nematic phase. A general observation is that TNTBN and TNI alternate in the same sense in a homologous series on varying the length of the terminal alkyl chains suggesting that the spatial uniformity of the molecular curvature is an important factor in stabilising the NTB phase. The transitional properties of the four corresponding dimers possessing nitrile terminal substituents are also described. These show enantiotropic nematic phases, and in addition, for those containing either polymethylene or hexyloxy spacers, a twist-bend nematic phase is observed. Differences in the thermal behaviour of the dimers may be attributed largely to changes in molecular shape arising from the nature of the link between the spacer and mesogenic units

Flexoelectric Polarization in a Nematic Liquid Crystal Enhanced by Dopants with Different Molecular Shape Polarities

Funding Information: We would like to acknowledge the great support which we received from Prof. I. Muševič, JSI, Ljubljana, Slovenia, Dr M. Klasen-Memmer, Merck, Germany, Dr Santanu Kumar Pal and Dr Golam Mohiuddin, Indian Institute of Science Education and Research (IISER) Mohali, India, and Prof. P. Kula and K. Garbat, MUT, Warsaw, Poland. This work has been partially supported by SeeReal Technologies and MUT Research Grants 13-843/WAT/2022.Peer reviewedPublisher PD

Sulfur-linked cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase

Acknowledgements EG and DP acknowledge the support of the National Science Centre (Poland): (Grant Number 2016/22/A/ST5/00319). We acknowledge the use of Beamline 5.3.1 and 11.0.1.2 of the Advanced Light Source supported by the Director of the Office of Science, Office of Basic Energy Science, of The U.S. Department of Energy under contract no. DE-AC02-05CH11231. We thank Alex Liebman-Pelaez for designing the heating stage used for TReXS measurement.Peer reviewedPostprin

Search For Trapped Antihydrogen

We present the results of an experiment to search for trapped antihydrogen atoms with the ALPHA antihydrogen trap at the CERN Antiproton Decelerator. Sensitive diagnostics of the temperatures, sizes, and densities of the trapped antiproton and positron plasmas have been developed, which in turn permitted development of techniques to precisely and reproducibly control the initial experimental parameters. The use of a position-sensitive annihilation vertex detector, together with the capability of controllably quenching the superconducting magnetic minimum trap, enabled us to carry out a high-sensitivity and low-background search for trapped synthesised antihydrogen atoms. We aim to identify the annihilations of antihydrogen atoms held for at least 130 ms in the trap before being released over ~30 ms. After a three-week experimental run in 2009 involving mixing of 10^7 antiprotons with 1.3 10^9 positrons to produce 6 10^5 antihydrogen atoms, we have identified six antiproton annihilation events that are consistent with the release of trapped antihydrogen. The cosmic ray background, estimated to contribute 0.14 counts, is incompatible with this observation at a significance of 5.6 sigma. Extensive simulations predict that an alternative source of annihilations, the escape of mirror-trapped antiprotons, is highly unlikely, though this possibility has not yet been ruled out experimentally.Comment: 12 pages, 7 figure

Eureka and beyond: mining's impact on African urbanisation

This collection brings separate literatures on mining and urbanisation together at a time when both artisanal and large-scale mining are expanding in many African economies. While much has been written about contestation over land and mineral rights, the impact of mining on settlement, notably its catalytic and fluctuating effects on migration and urban growth, has been largely ignored. African nation-states’ urbanisation trends have shown considerable variation over the past half century. The current surge in ‘new’ mining countries and the slow-down in ‘old’ mining countries are generating some remarkable settlement patterns and welfare outcomes. Presently, the African continent is a laboratory of national mining experiences. This special issue on African mining and urbanisation encompasses a wide cross-section of country case studies: beginning with the historical experiences of mining in Southern Africa (South Africa, Zambia, Zimbabwe), followed by more recent mineralizing trends in comparatively new mineral-producing countries (Tanzania) and an established West African gold producer (Ghana), before turning to the influence of conflict minerals (Angola, the Democratic Republic of Congo and Sierra Leone)

Interpretation of quantum jump and diffusion-processes illustrated on the Bloch sphere

It is shown that the evolution of an open quantum system whose density operator obeys a Markovian master equation can in some cases be meaningfully described in terms of stochastic Schrödinger equations (SSE’s) for its state vector. A necessary condition for this is that the information carried away from the system by the bath (source of the irreversibility) be recoverable. The primary field of application is quantum optics, where the bath consists of the continuum of electromagnetic modes. The information lost from the system can be recovered using a perfect photodetector. The state of the system conditioned on the photodetections undergoes stochastic quantum jumps. Alternative measurement schemes on the outgoing light (homodyne and heterodyne detection) are shown to give rise to SSE’s with diffusive terms. These three detection schemes are illustrated on a simple quantum system, the two-level atom, giving new perspectives on the interpretation of measurement results. The reality of these and other stochastic processes for state vectors is discussed