The quest for extreme water repellency: Superhydrophobicity made easy

In his seminal work On Floating Bodies I Archimedes of Syracuse provided an explanation of the action of solid bodies on water. Although his thesis immediately benefitted King Heiro II² and has continued to serve mankind well, it ignores the effect of the interfacial interactions between the solid, water and air (surface tension). These interactions are negligible, or at least are considered negligible, compared to forces arising from the effect of gravity on large bodies. However, as the mass of the body decreases, the surface interactions become increasingly important leading to some unusual and potentially useful phenomena. The understanding and application of these effects is currently driving much fundamental research by physicists, chemical engineers, material scientists, and chemists into surfaces that display extreme properties, in particular extreme water repellency, or superhydrophobicitv. It is only comparatively recently that detailed mathematical expressions for the interaction between a liquid, solid and gas at these extremes have been developed, making progress that parallels that for the fabrication of these surfaces

On the importance of π–π stacking and cation–anion interactions in the construction of non-centrosymmetric networks of bromide salts of imidazolium cations bearing arene and polyfluoroarene rings

The salt 1-(2,3,5,6-tetrafluoropyridyl)-3-benzylimidazolium bromide crystallizes in the non-centrosymmetric space group Pna2₁. The structure arises from π–π stacking between the benzyl and tetrafluoropyridyl groups of the cations and cation–bromide interactions. It is the latter that gives rise to the non-centrosymmetry

Experimental evidence for radiative attachment in astrochemistry from electron attachment to NCCCCN

Electron attachment to NCCCCN, dicyanoacetylene (2-butynedinitrile), has been observed. Metastable parent anions, NCCCCN_∗, with microsecond or longer lifetimes are formed close to 0 eV electron energy with a cross section of ≥0.25 2. The stability of NCCCCN suggests that radiative attachment to NCCCCN and similar _∗ °A linear carbon chain molecules may be an important mechanism for the formation of negatively charged molecular ions in astrophysical environments. CCCN_ and CN_ fragment anions are formed at ∼3 and ∼6 eV

Infinite stacking of alternating polyfluoroaryl rings and bromide anions

The crystal structure of 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide comprises columns of parallel bromotetrafluorophenyl rings with an interplanar distance of 6.936(6) Å separated by bromide anions

Theoretical study of the structures of 4-(2,3,5,6-tetrafluoropyridyl)diphenylphosphine oxide and tris(pentafluorophenyl)phosphine oxide: Why does the crystal structure of (tetrafluoropyridyl)diphenylphosphine oxide have two different P=O bond lengths?

The crystal structure of 4-(2,3,5,6-tetrafluoropyridyl)diphenylphosphine oxide (1) contains two independent molecules in the asymmetric unit. Although the molecules are virtually identical in all other aspects, the P=O bond distances differ by ca. 0.02 Å. In contrast, although tris(pentafluorophenyl)phosphine oxide (2) has a similar crystal structure, the P=O bond distances of the two independent molecules are identical. To investigate the reason for the difference, a density functional theory study was undertaken. Both structures comprise chains of molecules. The attraction between molecules of 1, which comprises lone pair–π, weak hydrogen bonding and C–H···arene interactions, has energies of 70 and 71 kJ mol⁻¹. The attraction between molecules of 2 comprises two lone pair–π interactions, and has energies of 99 and 100 kJ mol−1. There is weak hydrogen bonding between molecules of adjacent chains involving the oxygen atom of 1. For one molecule, this interaction is with a symmetry independent molecule, whereas for the other, it also occurs with a symmetry related molecule. This provides a reason for the difference in P=O distance. This interaction is not possible for 2, and so there is no difference between the P=O distances of 2

The crystal structures of 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-3-benzyl-methylimidazolium bromides

The crystal structures of 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-2-methyl-3-benzylimidazolium bromide (8) and 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-3-benzyl-4-methylimidazolium bromide (9) have been determined by single crystal X-ray diffraction. Both crystal structures possess C(2)─H⋯Br− hydrogen bonding and C─Br⋯Br− halogen bonding. That of 8 also contains π–π stacking between bromotetrafluorophenyl and phenyl rings, and that of 9 also contains C(1)─H⋯Br− hydrogen bonding and anion–π interactions. The crystal structure of 9 is similar to that of the non-methylated salt, 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide (4), with columns of alternating parallel bromotetrafluorophenyl rings and bromide

Access to psychological support for young people following stoma surgery: Exploring patients’ and clinicians’ perspectives

Psychological problems are common among people with inflammatory bowel disease (IBD) following stoma surgery. However, the ways in which stoma-related psychological needs are identified and addressed in healthcare settings remain unexplored. In this study, we investigated the perspectives of young people with a stoma and healthcare professionals about access to psychological support. Semi-structured interviews were conducted with young people with an IBD stoma (18-29 years) (n=13) and healthcare professionals (n=15), including colorectal surgeons, gastroenterologists, specialist nurses in IBD and stoma care, and general practitioners in England. Data collection and analysis were informed by constructivist grounded theory. Three analytic categories were developed: ‘initiating support-seeking’, ‘affirming psychological needs’, and ‘mobilizing psychological support’, which capture young peoples’ trajectory to accessing psychological support. Based on the findings, we highlight the need for both patients and healthcare professionals to assign greater priority to the identification of psychological symptoms post-stoma surgery. More effective care pathways, which include responsive psychological services, would enhance access to psychological support for young people with a stoma

A classification of local Weyl invariants in D=8

Following a purely algebraic procedure, we provide an exhaustive classification of local Weyl-invariant scalar densities in dimension D=8.Comment: LaTeX, 19 pages, typos corrected, one reference adde