There is no finite-variable equational axiomatization of representable relation algebras over weakly representable relation algebras

We prove that any equational basis that defines RRA over wRRA must contain infinitely many variables. The proof uses a construction of arbitrarily large finite weakly representable but not representable relation algebras whose "small" subalgebras are representable.Comment: To appear in Review of Symbolic Logi

The effect of military load carriage on ground reaction forces

Load carriage is an inevitable part of military life both during training and operations. Loads carried are frequently as high as 60% bodyweight, and this increases injury risk. In the military, load is carried in a backpack (also referred to as a Bergen) and webbing, these combined form a load carriage system (LCS). A substantial body of literature exists recording the physiological effects of load carriage; less is available regarding the biomechanics. Previous biomechanical studies have generally been restricted to loads of 20% and 40% of bodyweight, usually carried in the backpack alone. The effect of rifle carriage on gait has also received little or no attention in the published literature. This is despite military personnel almost always carrying a rifle during load carriage. In this study, 15 male participants completed 8 conditions: military boot, rifle, webbing 8 and 16 kg, backpack 16 kg and LCS 24, 32 and 40 kg. Results showed that load added in 8 kg increments elicited a proportional increase in vertical and anteroposterior ground reaction force (GRF) parameters. Rifle carriage significantly increased the impact peak and mediolateral impulse compared to the boot condition. These effects may be the result of changes to the vertical and horizontal position of the body's centre of mass, caused by the restriction of natural arm swing patterns. Increased GRFs, particularly in the vertical axis, have been positively linked to overuse injuries. Therefore, the biomechanical analysis of load carriage is important in aiding our understanding of injuries associated with military load carriage

A Note on Optimal Fees for Constant Function Market Makers

We suggest a framework to determine optimal trading fees for constant function market makers (CFMMs) in order to maximize liquidity provider returns. In a setting of multiple competing liquidity pools, we show that no race to the bottom occurs, but instead pure Nash equilibria of optimal fees exist. We theoretically prove the existence of these equilibria for pools using the constant product trade function used in popular CFMMs like Uniswap. We also numerically compute the equilibria for a number of examples and discuss the effects the equilibrium fees have on capital allocation among pools. Finally, we use our framework to compute optimal fees for real world pools using past trade data.Comment: 11 pages, 5 figure

Male mating constraints affect mutual mate choice: Prudent male courting and sperm limited females

Costs of sperm production may lead to prudence in male spermallocation and also to male mate choice. Here, we develop a life history–based mutual mate choice model that takes into account the lost-opportunity costs for males from time out in sperm recovery and lets mate competition be determined by the prevailing mate choice strategies. We assume that high mating rate may potentially lead to sperm depletion in males, and that as a result, female reproduction may be limited by the availability of sperm. Increasing variation in male quality leads, in general, to increased selective mate choice by females, and vice versa. Lower-quality males may, however, gain access to more fecund higher-quality females by lowering their courting rate, thus increasing their sperm reserves. When faced with strong male competition for mates, low-quality males become less choosy, which leads to assortative mating for quality and an increased mating rate across all males. With assortative mating, the frequency of antagonistic interactions (sexual conflict) is reduced, allowing males to lower the time spent replenishing sperm reserves in order to increase mating rate. This in turn leads to lower sperm levels at mating and therefore could lead to negative effects on female fitness via sperm limitation

Lunar regolith bagging system

A design of a lunar regolith bag and bagging system is described. The bags of regolith are to be used for construction applications on the lunar surface. The machine is designed to be used in conjunction with the lunar SKITTER currently under development. The bags for this system are 1 cu ft volume and are made from a fiberglass composite weave. The machinery is constructed mostly from a boron/aluminum composite. The machine can fill 120 bags per hour and work for 8 hours a day. The man hours to machine hours ratio to operate the machine is .5/8

5th Annual Symposium of the United Kingdom & Ireland Engineering Education Research Network: Time for change

The proceedings of the 5th symposium of the UK & IE Engineering Education Network set about challenging the status quo in all areas of engineering education. Over two days colleagues discussed and debated a number of issues ranging from engineering in schools and attracting young people into engineering, to innovative engineering pedagogies. The highly contentious question of whether ‘maths’ is, or is not, a vital prerequisite to studying engineering at university was debated whilst an expert panel asked the question “Are engineering educators fit for purpose?”.Needless to say the Symposium proved to be a lively event. In an attempt to provide the engineering education community with a taste of the debates the short Symposium Papers presented here represent ‘the tip of the iceberg’ with regards to the wide range of problems and solutions discussed and proposed. Divided into three main sections this publication shows that the Symposium did indeed achieve its objective of ‘challenging the status quo’. The papers presented in the first section argue the case for change in engineering education. Whilst the second section turns to look at engineering education practice and pedagogy, with an additional section included to assure non-expert researchers are given a voice. The final section brings the document to a close with a number of papers that look at how colleagues across the UK are beginning to innovate change in the engineering classroom and beyond

The Trichoptera of Panama XIII. Further new country records for caddisflies (Insecta: Trichoptera) from the Republic of Panama

The Republic of Panama currently includes 414 recorded species of Trichoptera. Herein we add two new genera (Hydroptilidae: Angrisanoia Ozdikmen, 2008 and Mayatrichia Mosely, 1937) and 17 new country records (Philopotamidae: Chimarra (C.) tapanti Blahnik, Wormaldia bolivari Muñoz-Quesada and Holzenthal, and Wormaldia zunigae Muñoz-Quesada and Holzenthal; Hydropsychidae: Centromacronema pygmaeum Botosaneanu; Hydroptilidae: Brysopteryx esparta Harris and Holzenthal, Byrsopteryx solisi Harris and Holzenthal, Costatrichia falsa Santos, Takiya, and Nessimian, Mayatrichia illobia Harris and Holzenthal, Metrichia amplitudinis Bueno-Soria and Holzenthal, Ochrotrichia boquillas Moulton and Harris, O. conformalis Bueno-Soria and Holzenthal, O. quinealensis Bueno-Soria and Holzenthal, and O. unica Bueno-Soria and Santiago; Leptoceridae: Triaenodes morai Holzenthal and Andersen; Odontoceridae: Marilia kingsolveri Bueno-Soria and Rojas-Ascencio; and, Helicopsychidae: Helicopsyche alajuela Johanson and Holzenthal and Helicopsyche breviterga Flint) to Panama’s caddisfly fauna. The newly recorded taxa increase Panama’s total known caddisfly fauna to 431 species, distributed among 15 families and 55 genera. These results are part of an ongoing effort to characterize the caddisfly fauna of Panama, and to evaluate the aquatic insect diversity of the country’s major watersheds (cuencas). La República de Panamá actualmente incluye 414 especies registradas de Trichoptera. Aquí agregamos dos nuevos géneros (Hydroptilidae: Angrisanoia Ozdikmen, 2008 y Mayatrichia Mosely, 1937) y 17 nuevos registros para el país (Philopotamidae: Chimarra (C.) tapanti Blahnik, Wormaldia bolivari Muñoz-Quesada y Holzenthal, y Wormaldia zunigae Muñoz-Quesada y Holzenthal; Hydropsychidae: Centromacronema pygmaeum Botosaneanu; Hydroptilidae: Brysopteryx esparta Harris y Holzenthal, Byrsopteryx solisi Harris y Holzenthal, Costatrichia falsa Santos, Takiya, y Nessimian, Mayatrichia illobia Harris y Holzenthal, Metrichia amplitudinis Bueno-Soria y Holzenthal, Ochrotrichia boquillas Moulton y Harris, Ochrotrichia conformalis Bueno-Soria y Holzenthal, Ochrotrichia quinealensis Bueno-Soria y Holzenthal, y Ochrotrichia unica Bueno-Soria y Santiago; Leptoceridae: Triaenodes morai Holzenthal y Andersen; Odontoceridae: Marilia kingsolveri Bueno-Soria y Rojas- Ascencio; y, Helicopsychidae: Helicopsyche alajuela Johanson y Holzenthal y Helicopsyche breviterga Flint) a la fauna de Trichoptera de Panamá. Los taxones recien reportados aumentan el total de la fauna de Trichoptera de Panamá a 431 especies, distribuidas en 15 familias y 55 géneros. Estos resultados son parte de un esfuerzo continuo para caracterizar la fauna de Trichoptera y para evaluar la diversidad de insectos acuáticos de las principales cuencas hidrográficas (cuencas) de Panamá