Facile Synthesis of 3,6‐Diaminopyridazine

An efficient two‐step synthesis of 3,6‐diaminopyridazine from 3,6‐dichloropyridazine is reported. In this synthetic procedure, 4‐methoxybenzylamine was used as a nitrogen source to substitute the chloro groups of 3,6‐dichloropyridazine to form N,N′‐bis‐(4‐methoxybenzyl)‐pyridazine‐3,6‐diamine. The 4‐methoxybenzyl groups were then removed by treatment with hydrochloric acid to provide the target 3,6‐diaminopyridazine with an overall yield of 78%.     

Studies on Pyrrolidinones. An Improved One Pot Synthesis of 1,2,3,5,10,10a-Hexahydrobenz[f]indolizine-3,10-dione

Starting from the readily available N,O-bis trimethylsilyl pyroglutamate, an easy high yield one pot synthesis of ketone 1 was described.     

Sun Exposure over a Lifetime in Australian Adults from Latitudinally Diverse Regions

Spatio‐temporal patterns in sun exposure underlie variations in skin cancer incidence and vitamin D deficiency, indicate effectiveness of sun protection programs and provide insights into future health risks. From 558 adults across four regions of Australia (Brisbane (27°S), Newcastle (33°S), Geelong and the Western Districts of Victoria (37°S) and Tasmania (43°S)), we collected: self‐report data on time‐in‐the‐sun from age 6 years; natural skin color and ethnicity; silicone skin casts (for cumulative skin damage); and serum for vitamin D status. Ambient ultraviolet radiation (UVR) at the location of residence, with time‐in‐the‐sun, was used to calculate a “UVR dose” for each year of life. Individuals maintained their ranking compared to their peers for time‐in‐the‐sun in summer compared to winter and across ages (Spearman rho 0.24–0.84, all P < 0.001). Time‐in‐the‐sun decreased with age in all birth cohorts, and over calendar time. Summer time‐in‐the‐sun increased with increasing latitude (P < 0.001). Seasonal variation in vitamin D status had greater amplitude and vitamin D deficiency increased with increasing latitude. Temporal patterns are consistent with effectiveness of sun protection programs. Higher relative time‐in‐the‐sun persists from childhood through adulthood. Lower summer time‐in‐the‐sun in the warmest location may have implications for predictions of UVR‐related health risks of climate change.     

Efficient Synthesis of New Nucleoside Analogues with a Methylenecyclobutane Unit

Synthesis of eight nucleoside analogues 4–11 with a methylenecyclobutane unit is described. Wittig reaction with 2‐hydroxymethylcyclobutanone 12 gave a mixture of Z (13) and E (14) derivatives, which was separated before functional modifications. The heterocyclic moieties were introduced via a Mitsunobu reaction either on the saturated chain or on the unsaturated chain. When adenine was used in this reaction, only the N‐9 substitution products were obtained. Removal of the protecting groups provided the target products.     

Preparation of the N-(2-Bromo-2-Nitroethenyl) Benzenamine: The First One-Pot Synthesis of a β-Halo-β-Nitroenamine

Bromonitromethane, triethyl orthoformate and aniline react together, in a one-flask procedure, to afford the title compound.     

Emulsions of Heavy Crude Oils. II. Viscous Responses and Their Influence on Emulsion Stability Measurements

The stability of 30 heavy crude oil emulsions was studied in a parallel-plate laboratory coalescer (DC field). Particularly, viscous responses and their influence on the emulsion stability measurements were investigated. In addition to highlighting previous results from the same experimental setup and discussing these based on recent experience, new results at different temperatures and volume fractions of water were presented. A new semi-empirical model for the characteristic time of the destabilization process was presented. The electrical forces were modelled with a point-dipole approximation and the hydrodynamic resistance to droplet transport was modelled with an empirical term including the logarithmic viscosity of the oil phase. The new model clearly performed much better than the previous model, particularly for very viscous crude oils. Studies of the performance of industrial electrocoalescers have showed that simple electrostatic theory can potentially explain complex separation phenomena when the resistance to the coalescence step is reduced by an efficient demulsifier. The ultimate goal is to build a model for both the laboratory setup and the industrial coalescer so that laboratory experiments can be used to predict the behavior of the industrial process.     

Atoms of multistationarity in chemical reaction networks

Chemical reaction systems are dynamical systems that arise in chemical engineering and systems biology. In this work, we consider the question of whether the minimal (in a precise sense) multistationary chemical reaction networks, which we propose to call ‘atoms of multistationarity,’ characterize the entire set of multistationary networks. Our main result states that the answer to this question is ‘yes’ in the context of fully open continuous-flow stirred-tank reactors (CFSTRs), which are networks in which all chemical species take part in the inflow and outflow. In order to prove this result, we show that if a subnetwork admits multiple steady states, then these steady states can be lifted to a larger network, provided that the two networks share the same stoichiometric subspace. We also prove an analogous result when a smaller network is obtained from a larger network by ‘removing species.’ Our results provide the mathematical foundation for a technique used by Siegal- Gaskins et al. of establishing bistability by way of ‘network ancestry.’ Additionally, our work provides sufficient conditions for establishing multistationarity by way of atoms and moreover reduces the problem of classifying multistationary CFSTRs to that of cataloging atoms of multistationarity. As an application, we enumerate and classify all 386 bimolecular and reversible two-reaction networks. Of these, exactly 35 admit multiple positive steady states. Moreover, each admits a unique minimal multistationary subnetwork, and these subnetworks form a poset (with respect to the relation of ‘removing species’) which has 11 minimal elements (the atoms of multistationarity).