New RM734-like fluid ferroelectrics enabled through a simplified protecting group free synthesis

We report a novel and simplified synthetic procedure for making analogues of the widely studied ferroelectric nematogen RM734. Our new procedure focuses on building materials starting from the nitro-terminus and eschewing protecting groups, in contrast to previously reported syntheses. This new synthetic approach confers two principal advantages: firstly, the synthesis of the variants described herein is expedient, being a single step as opposed to three or more via the classical route. Secondly, by forgoing the use of benzyl groups as utilised in the original synthesis we can include functionality that is incompatible with hydrogenolysis conditions (e.g. olefins, late halogens, unsaturated heterocycles). Several of the RM734-like materials we report exhibit ferroelectric nematic phases, and we rationalise the behaviour of these materials with aid of electronic structure calculations, potential energy surface scans and atomistic molecular dynamics simulations

Rapid conformational analysis of semi-flexible liquid crystals.

We present an approach for rapid conformational analysis of semi-flexible liquid crystals. We use a simple graphical user interface (GUI) tool that leverages rules-based methods for efficient generation of bend-angle distributions, offering a significant improvement over traditional single-conformer analysis. Our methods demonstrated proficiency in approximating molecular shapes comparable to those obtained from molecular dynamics (MD) simulations, albeit with notable deviations in the under sampling of hairpin conformations and oversampling of extended configurations. Re-evaluation of existing data revealed an apparent weak correlation between NTB transition temperatures and bend angles, underscoring the complexity of molecular shapes beyond mere geometry. Furthermore, we integrated this conformational analysis into a pipeline of algorithmic molecular design, utilising a fragment-based genetic algorithm to generate novel cyanobiphenyl-containing materials. This integration opens new avenues for the exploration of liquid crystalline materials, particularly in systems where systematic conformer searches are impractical, such as large oligomeric systems. Our findings highlight the potential and growing importance of computational approaches in accelerating the design and synthesis of next-generation liquid crystalline materials

A convenient one-pot synthesis, and characterisation of the ω-bromo-1-(4-cyanobiphenyl-4’-yl) alkanes (CBnBr)

A convenient synthetic route based on a sodium-mediated aromatic cross-coupling reaction is described for the multi-gram preparation of the ω-bromo-1-(4-cyanobiphenyl-4’−yl) alkanes (CBnBr, n = 2–10). These materials are not only key intermediates in the synthesis of oligomers and polymers but also exhibit fascinating liquid crystal behaviour in their own right. Nematic behaviour is observed for n⩾5, and the nematic-isotropic transition temperature, TNI, increases in essentially a linear manner on n. The properties of the ω-bromo-1-(4-cyanobiphenyl-4’−yloxy) alkanes (CBOnBr, n = 2–9) are also reported, and nematic behaviour is seen for n⩾3. The values of TNI show a weak odd-even effect on n in which the odd members show the higher values. The sense of this alternation is opposite to that seen for the 4-alkyloxy-4’-cyanobiphenyls, and this is attributed to the steric bulk of the bromine atom. The absence of smectic behaviour for both the CBnBr and CBOnBr series is attributed largely to electrostatic interactions that would arise from the concentration of the bromine atoms at the layer interfaces in an interdigitated smectic phase. A comparison of a range of cyanobiphenyl-based materials containing a chain with a terminal polar or polarisable group suggests that their phase behaviour is governed largely by their average molecular shapes

(Sub)mm Interferometry Applications in Star Formation Research

This contribution gives an overview about various applications of (sub)mm interferometry in star formation research. The topics covered are molecular outflows, accretion disks, fragmentation and chemical properties of low- and high-mass star-forming regions. A short outlook on the capabilities of ALMA is given as well.Comment: 20 pages, 7 figures, in proceedings to "2nd European School on Jets from Young Star: High Angular Resolution Observations". A high-resolution version of the paper can be found at http://www.mpia.de/homes/beuther/papers.htm

Observational diagnostics of gas in protoplanetary disks

Protoplanetary disks are composed primarily of gas (99% of the mass). Nevertheless, relatively few observational constraints exist for the gas in disks. In this review, I discuss several observational diagnostics in the UV, optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to study the gas in the disks of young stellar objects. I concentrate in diagnostics that probe the inner 20 AU of the disk, the region where planets are expected to form. I discuss the potential and limitations of each gas tracer and present prospects for future research.Comment: Review written for the proceedings of the conference "Origin and Evolution of Planets 2008", Ascona, Switzerland, June 29 - July 4, 2008. Date manuscript: October 2008. 17 Pages, 6 graphics, 134 reference

Massive Star Formation

This chapter reviews progress in the field of massive star formation. It focuses on evidence for accretion and current models that invoke high accretion rates. In particular it is noted that high accretion rates will cause the massive young stellar object to have a radius much larger than its eventual main sequence radius throughout much of the accretion phase. This results in low effective temperatures which may provide the explanation as to why luminous young stellar objects do not ionized their surroundings to form ultra-compact H II regions. The transition to the ultra-compact H II region phase would then be associated with the termination of the high accretion rate phase. Objects thought to be in a transition phase are discussed and diagnostic diagrams to distinguish between massive young stellar objects and ultra-compact H II regions in terms of line widths and radio luminosity are presented.Comment: 21 pages, 6 figures, chapter in Diffuse Matter from Star Forming Regions to Active Galaxies - A Volume Honouring John Dyson, Edited by T.W. Hartquist, J. M. Pittard, and S. A. E. G. Falle. Series: Astrophysics and Space Science Proceedings. Springer Dordrecht, 2007, p.6

The Origin, Early Evolution and Predictability of Solar Eruptions

Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt

Comprehensive Molecular Characterization of Muscle-Invasive Bladder Cancer

We report a comprehensive analysis of 412 muscle-invasive bladder cancers characterized by multiple TCGA analytical platforms. Fifty-eight genes were significantly mutated, and the overall mutational load was associated with APOBEC-signature mutagenesis. Clustering by mutation signature identified a high-mutation subset with 75% 5-year survival. mRNA expression clustering refined prior clustering analyses and identified a poor-survival “neuronal” subtype in which the majority of tumors lacked small cell or neuroendocrine histology. Clustering by mRNA, long non-coding RNA (lncRNA), and miRNA expression converged to identify subsets with differential epithelial-mesenchymal transition status, carcinoma in situ scores, histologic features, and survival. Our analyses identified 5 expression subtypes that may stratify response to different treatments. A multiplatform analysis of 412 muscle-invasive bladder cancer patients provides insights into mutational profiles with prognostic value and establishes a framework associating distinct tumor subtypes with clinical options