Ponto-Caspian amphipod co-location with zebra mussel beds (Dreissena polymorpha) is influenced by substrate size and population source

The global spread of non-native species is leading to an increasing frequency of multiple co-occurring non-native species. We examined the co-occurrence of Dreissena polymorpha with three Ponto-Caspian amphipods (Dikerogammarus villosus, Dikerogammarus haemobaphes, and Chelicorophium curvispinum) across England and Wales in association with in-situ substate size. For all three amphipod species, substrate grain size where amphipods co-occurred with D. polymorpha was significantly finer than when recorded in isolation. Subsequently, we confirmed this observational association via aquarium experiments. We examined the occurrence of D. villosus with D. polymorpha when present with cobbles, gravel or sand from three population sources (co-location with abundant D. polymorpha populations, co-location with low populations, and naïve). Aquarium experiments demonstrated that D. villosus actively sought shelter on or near D. polymorpha, with their co-location being significantly more prevalent in finer grained substrates (sand > gravel > cobble). The strength of this co-location was also found to differ as a function of the population source with those co-located with high D. polymorpha densities demonstrating a greater association. Our analyses and experiments indicate that D. polymorpha may enable Ponto-Caspian amphipods to expand into otherwise suboptimal locations

Size scale effect in cavitation erosion

An overview and data analyses pertaining to cavitation erosion size scale effects are presented. The exponents n in the power law relationship are found to vary from 1.7 to 4.9 for venturi and rotating disk devices supporting the values reported in the literature. Suggestions for future studies were made to arrive at further true scale effects

The Irish grey partridge conservation strategy: an update 1995-1998.

KAVANAGH, B.P., O\u27GORMAN,C.,AND BUCKLEY, C.: THE IRISH GREY PARTRIDGE (PERDIX PERDIX) CONSERVATION STRATEGY: AN UPDATE 1995-1998.In May 1996 a strategy for the conservation of the last remaining population of the Irish Grey partridge was initiated. The strategy is a multipronged approach based on a) predation reduction, b) habitat improvement and c) monitoring of the birds’ response. A full-time game keeper was employed to reduce red fox (Vulpes vulpes), mink (Mustella vison), stoat (Mustella erminea), rat (Rattus norvegicus), grey crow (Corvus corone cornix)and magpie (Pica pica) numbers in a defined study area of 1,000 hectares of cutaway bog at Boora in County Offaly. The habitatis a mozaic of cutaway bogland, conferous forestry, newly created farmland and wetland. The area contianed 6-8 pairs of breeding grey partridge in spring 1996. Bare peat areas within the study area were selected and a mix of either grasser or grains were planted in 0,2 hectare blocks to provide nesting or chick rearing cover for birds. These plots were neither sprayed or harvested and have been left to develop naturally after planting. Fifteen hectares were planted over two years, 1996-97. In spring 1997 a number of male partridges were trapped and fitted with radio collars. Their home range and habitat preferences were recorded continuously for up to ten months. Radio-tracked birds were recorded leaving the keepered area and moving to winter stubble fields on adjoining farmland. Two successful coveys were produced in 1996 which resulted in a autumn count of 27 partridges in the study area. In spring 1997 the population in the study area was again 6-8 pairs. Two successful coveys were again produced in 1997 giving an autumn population was 23 birds within the study area. Winter survival in 1997/98 was poor. In spring 1998 only 4-6 pairs of partridges were found in the study area. Partridge numbers continue to decline both within and outside the study area. The remaining population is now less than 20 breeding pairs in total

If you can't be with the one you love, love the one you're with: How individual habituation of agent interactions improves global utility

Simple distributed strategies that modify the behaviour of selfish individuals in a manner that enhances cooperation or global efficiency have proved difficult to identify. We consider a network of selfish agents who each optimise their individual utilities by coordinating (or anti-coordinating) with their neighbours, to maximise the pay-offs from randomly weighted pair-wise games. In general, agents will opt for the behaviour that is the best compromise (for them) of the many conflicting constraints created by their neighbours, but the attractors of the system as a whole will not maximise total utility. We then consider agents that act as 'creatures of habit' by increasing their preference to coordinate (anti-coordinate) with whichever neighbours they are coordinated (anti-coordinated) with at the present moment. These preferences change slowly while the system is repeatedly perturbed such that it settles to many different local attractors. We find that under these conditions, with each perturbation there is a progressively higher chance of the system settling to a configuration with high total utility. Eventually, only one attractor remains, and that attractor is very likely to maximise (or almost maximise) global utility. This counterintutitve result can be understood using theory from computational neuroscience; we show that this simple form of habituation is equivalent to Hebbian learning, and the improved optimisation of global utility that is observed results from wellknown generalisation capabilities of associative memory acting at the network scale. This causes the system of selfish agents, each acting individually but habitually, to collectively identify configurations that maximise total utility

Assessing users’ experience of shared sanitation facilities: A case study of community ablution blocks in Durban, South Africa

Despite significant financial investment, the effective implementation and sustained use of water and sanitation (WATSAN) technologies remains a chimera, with one billion people using unimproved water facilities and two and a half billion not benefitting from adequate sanitation. The poor success rate of WATSAN interventions results from a predominance of supply-driven approaches which lack recipients’ inputs into planning and implementation to ensure that technologies are fully absorbed and adapted to users’ needs. In the academic literature, users’ feedback and experiences of technologies in the post-implementation phase have received scarce attention. The purpose of this study is to investigate users’ experience of sanitation technologies in the early post-implementation phase, when opportunities for remedial intervention are still available. Fieldwork comprising semi-structured interviews was undertaken with users and potential recipients of three community ablution blocks (CABs) in informal settlements around Durban. Results suggest that non-technical aspects such as affordability or cleanliness of the facilities can affect acceptance among the investigated communities. User training is positively associated with higher levels of facility maintenance as well as satisfaction with its functionality. A comparison between users and potential recipients of CABs shows that perceived health benefits, attitudes in case of  problems, and trust are affected by use of the facilities. Conclusions relate to how early post-implementation assessments of users’ experiencecould enhance the process of acceptance and management of the technology, thereby increasing progress towards achievement of the related Millenium Development Goals.Keywords: Ablution blocks, user acceptance, eThekwini municipality, Durban, sanitatio

Spin Discrimination in Three-Body Decays

The identification of the correct model for physics beyond the Standard Model requires the determination of the spin of new particles. We investigate to which extent the spin of a new particle $X$ can be identified in scenarios where it decays dominantly in three-body decays $X\to f\bar{f} Y$. Here we assume that $Y$ is a candidate for dark matter and escapes direct detection at a high energy collider such as the LHC. We show that in the case that all intermediate particles are heavy, one can get information on the spins of $X$ and $Y$ at the LHC by exploiting the invariant mass distribution of the two standard model fermions. We develop a model-independent strategy to determine the spins without prior knowledge of the unknown couplings and test it in a series of Monte Carlo studies.Comment: 31+1 pages, 4 figures, 8 tables, JHEP.cls include

Stream-field interactions in the magnetic accretor AO Piscium

UV spectra of the magnetic accretor AO Psc show absorption features for half the binary orbit. The absorption is unlike the wind-formed features often seen in similar stars. Instead, we attribute it to a fraction of the stream that overflows the impact with the accretion disk. Rapid velocity variations can be explained by changes in the trajectory of the stream depending on the orientation of the white-dwarf's magnetic field. Hence we are directly observing the interaction of an accretion stream with a rotating field. We compare this behavior to that seen in other intermediate polars and in SW Sex stars.Comment: Accepted for ApJ; 6 page

Development of a forced-convection gas target for improved thermal performance

Introduction The internal pressure experienced by a gas tar-get during irradiation is dependent on the beam energy deposited in the target, the beam cur-rent, and the thermal behaviour of the target. [1] The maximum beam energy deposited is a function of the cyclotron capabilities and the gas inventory within the target. The maximum beam current is limited by the pressure produced in the target and the ability of the target assembly to remain intact. This is also a function of the thermal behaviour of the target, which is difficult to predict a priori since it is dependent on such things as convection currents that occur during irradiation. We conducted bench tests with model gas targets with and without forced convection currents to observe the effect on thermal behaviour. Based on those results we constructed a prototype gas target, suitable for irradiation, with an internal fan assembly that is rotated via external magnets. Material and Methods Bench tests were conducted with cylindrical and conical target bodies of aluminum. A nickel-chromium heater wire was inserted into the gas volume through the normal beam entrance port (FIGURE 1) to heat the gas while water cooling was applied to the target body. The voltage and current of the heater coil was monitored along with the pressure inside the target and the water inlet and outlet temperature. In the case of tests with a driven fan blade either the voltage applied to the electric motor was monitored or the fan speed itself was recorded. By assuming the ideal gas law, the pressure gives the average bulk temperature and a global heat transfer coefficient can be calculated between the target gas and the cooling water. [2] A cylindrical target body was constructed that incorporated a fan blade driven by an external motor. This assembly used a simple o-ring seal on the rotating shaft. This seal was not robust enough for any tests under beam conditions. A prototype design suitable for in-beam operation employs a propeller mounted on a rotating disc housing two samarium cobalt magnets and spinning on two micro-bearings which are constructed to operate in high temperature environments. The micro-bearings are mounted on a pin projecting from a plate welded to the back of the gas target to allow assembly of the fan mechanism prior to attachment to the body (FIGURE 2)

Hydrogen Desorption Properties of Bulk and Nanoconfined LiBH4-NaAlH4

Nanoconfinement of 2LiBH4-NaAlH4 into a mesoporous carbon aerogel scaffold with a pore size, BET surface area and total pore volume of Dmax = 30 nm, SBET = 689 m2/g and Vtot = 1.21 mL/g, respectively is investigated. Nanoconfinement of 2LiBH4-NaAlH4 facilitates a reduction in the temperature of the hydrogen release by 132 °C, compared to that of bulk 2LiBH4-NaAlH4 and the onset of hydrogen release is below 100 °C. The reversible hydrogen storage capacity is also significantly improved for the nanoconfined sample, maintaining 83% of the initial hydrogen content after three cycles compared to 47% for that of the bulk sample. During nanoconfinement, LiBH4 and NaAlH4 reacts to form LiAlH4 and NaBH4 and the final dehydrogenation products, obtained at 481 °C are LiH, LiAl, AlB2 and Al. After rehydrogenation of the nanoconfined sample at T = 400 °C and p(H2) = 126 bar, amorphous NaBH4 is recovered along with unreacted LiH, AlB2 and Al and suggests that NaBH4 is the main compound that can reversibly release and uptake hydrogen