An additional dimension has been added to our long-standing studies in high silica zeolite synthesis via a guest/host synergism. We have created and studied the impact of making symmetric diquaternary ammonium compounds, by varying the chain length between nitrogen charge centers, and the heterocycle size and geometry containing the nitrogen. This allows the introduction of a second spatial parameter in the use of the charged organo-cation guest in the zeolite synthesis. The series of 15 diquaternary ammonium compounds (5 heterocycles synthesized onto chain lengths of C4-C6) were tested in a total of 135 zeolite syntheses reactions. Nine screening reactions were employed for each guest molecule, and the conditions built upon past successes in finding novel high silica zeolites via introduction of boron, aluminum, or germanium as substituting tetrahedral framework atoms for silicon. Eighteen different zeolite structures emerged from the studies. The use of specific chain lengths for derivatives of the pyrrolidine ring system produced novel zeolite materials SSZ-74 and 75.

Background : Despite the ubiquity of hand trauma, there remains insufficient published data to reliably inform these patients of surgical site infection (SSI) risk. We describe the risk of SSI in a single-centre cohort of hand trauma patients, with an analysis of the impact of the COVID-19 pandemic. Methods : Retrospective data collection of consecutive patients who underwent surgery for hand and wrist trauma in a single plastic surgery centre over two, three-month periods. Demographic, injury and operative details, alongside prophylactic antibiotic use, were recorded. Burn injuries and wounds infected at presentation were excluded. Presence of SSI at 30 days (90 days if a surgical implant was used) was assessed. Results : Overall, 556 patients - ‘Pre-COVID-19’ (n=310); ‘During COVID-19’ (n=246) - were included. Risk of SSI was 3.6% in the aggregated cohort. Female patients were more likely to develop an SSI, even when adjusted for their greater prevalence of bite aetiologies (adjOR 2.5; 95% CI, 1.00-6.37; p<0.05). The absolute risk of SSI in the ‘Pre-COVID-19’ group was 2.3% and 5.3% in the ‘During COVID-19’ group. The relative risk of developing an SSI in the ‘During COVID-19’ group, was 2.34 (95% CI, 0.95-5.78; p=0.06). Baseline characteristics were equivalent between the two groups. Conclusion : The risk of SSI in hand trauma is the same as the nationally estimated risk for all surgery; 3-5%. Changes in presentation and practice associated with the first wave of the COVID-19 pandemic did not appear to alter the risk of SSI in patients undergoing surgery for hand trauma.

An unusual case of a diquaternary ammonium dication, with large bulky end groups built from the tropane moiety and connected by a C4 methylene chain, is found to reside in zeolite . The structure of the guest/host product is such that the tropane bicylic entities reside in the shallow cavities of the cages of the STF structure and the C4 methylene chain runs through the 10-ring (∼5.5 Å) window that connects the cages. This is a most unusual (and energy-intensive) templating of a zeolite structure with the guest molecule spanning two unit cells. The unusual result was found by single crystal studies with the addition of the use of the SQUEEZE program to show a consistent fit for the guest molecule following from measured electron densities in the crystal structure work. These analyses were followed with MAS NMR studies to confirm the integrity of the diquaternary guest molecule in the host sieve. A few comparative diquaternary guest molecules in MFI zeolite are also studied.