Lightweight, low compression aircraft diesel engine

The feasibility of converting a spark ignition aircraft engine to the diesel cycle was investigated. Procedures necessary for converting a single cylinder GTS10-520 are described as well as a single cylinder diesel engine test program. The modification of the engine for the hot port cooling concept is discussed. A digital computer graphics simulation of a twin engine aircraft incorporating the diesel engine and Hot Fort concept is presented showing some potential gains in aircraft performance. Sample results of the computer program used in the simulation are included

The importance of being beta: female succession in a cooperative breeder

In singular cooperative breeders few females breed successfully, but those that acquire dominant positions can achieve high levels of breeding success, leading to strong selection for traits that enable individuals to acquire and maintain dominance status. However, little is known about the process by which females acquire dominant breeding status or the traits that enable them to do so. Female meerkats, Suricata suricatta, can acquire dominance either by inheritance after the death of the previous dominant, by displacing the incumbent dominant or at the foundation of a new group. Here we investigated the possible fitness benefits associated with these different routes to dominance and the traits that affect an individual's probability of acquiring dominance via these routes. We found that all routes to dominance had similar fitness benefits and that when a dominance vacancy arose, weight was the main determinate of succession, with age still influencing within-group succession and the eldest subordinate female, the beta, often succeeding to dominance. Since the chance that subordinate females will acquire dominance is also positively correlated with the duration of their tenure in the beta position, we tested whether beta females adjusted their growth or cooperative behaviour to avoid eviction and increased their tenure length as the beta. However, there was no indication that betas employed either strategy to increase their tenure. Given that the differing routes to dominance have equivalent fitness pay-offs and are triggered stochastically, selection probably favours flexibility rather than strategies that commit individuals to a specific route.The Kalahari Meerkat Project was funded by the European Research Council (grant no. 294494), the Natural Environment Research Council (grant no. NE/G006822/1) and the Swiss National Science Foundation and supported by the Universities of Cambridge, Zurich and Pretoria

High nuclearity Ni(ii) cages from hydroxamate ligands

The synthesis, structural and magnetic characterisation of a family of Ni(ii) cages built from hydroxamate ligands is presented. Two pentanuclear 12-MCNi(ii)-4 metallacrowns [Ni5(L1) 4(MeOH)4](ClO4)2·2MeOH (1) and [Ni5(L1)4(py)5](ClO 4)2·H2O (2) (where L1H 2 = 2-(dimethylamino)phenylhydroxamic acid) share analogous, near-planar {Ni5(L1)4}2+ cores, but differ in the number and nature of the ligands located at the axial Ni(ii) sites; the addition of pyridine converting square planar Ni(ii) ions to square-based pyramidal and octahedral Ni(ii) ions, introducing extra paramagnetic metal centres which 'switch on' additional magnetic superexchange pathways. Subtle variations in the reaction scheme used to produce complexes 1 and 2 result in both a change of topology and an increase in nuclearity, through isolation of the hepta- and nonametallic complexes [Ni7(L 1H)8(L1)2(H2O) 6](SO4)·15H2O (3), [Ni 9(μ-H2O)2(L2)6(L 2H)4(H2O)2](SO4) ·29H2O (4) and [Ni9(μ-H2O) 2(L2)6(L2H)4(H 2O)2](ClO4)2·2MeOH· 18H2O (5) (where L2H2 = 2-(amino) phenylhydroxamic acid). Complementary dc magnetic susceptibility studies and DFT analysis indicate dominant antiferromagnetic exchange interactions in 1, 2, 4 and 5, but competing ferro- and antiferromagnetic exchange in 3. © the Partner Organisations 2014.EKB would like to thank the EPSRC for funding (SS). GR acknowledges financial support from the Government of India through the Department of Science and Technology (SR/S1/IC-41/2010; SR/NM/NS-1119/2011) and generous computational resources from the Indian Institute of Technology-Bombay. MKS thanks the University Grants Commission for a Junior Research Fellowship.Published versio