Near infrared spectroscopy of W51 IRS-2

Near-infrared spectra at 2.95-3.5 μm and 3.99-10 μm have been obtained towards W51 IRS-2 and its surroundings, in order to investigate the spatial variations in intensity of the 3.28 μm unidentified feature and the 4.05 μm Brackett-α line. The Br-α and 3.28 μm features occupy a broadly similar spatial zone, which is characterised by an unresolved core responsible for most of the emission, and an extended and considerably weaker halo. Grain properties required to excite the 4.28 microns line, the nature of the 3.28 μm emission, and its relation to the source structure are discussed

Constraining fine tuning in composite Higgs models with partially composite leptons

Minimal Composite Higgs Models (MCHM) have long provided a solution to the hierarchy problem of the Standard Model, yet suffer from various sources of fine tuning that are becoming increasingly problematic with the lack of new physics observations at the LHC. We develop a new fine tuning measure that accurately counts each contribution to fine tuning (single, double, triple, etc) that can occur in a theory with np parameters, that must reproduce no observables. We then use a novel scanning procedure to perform a comprehensive study of three different two-site, 4D, SO(5) → SO(4) MCHMs with all third generation fermions included, distinguished by the choice of the lepton embeddings. These are the MCHM5 − 5 − 55 − 5 − 5, MCHM14 − 14 − 105 − 5 − 5 and MCHM14 − 1 − 105 − 5 − 5, where MCHMl − τ − νq − t − b has the lepton doublet partner in representation l, tau partner in representation τ, and so on. We find that embedding at least one massive lepton in the symmetric 14 of SO(5) moderately reduces the tuning for the case of low top partner masses (in line with previous results), but that this is balanced against the increased complexity of the model when one properly accounts for all sources of fine tuning. We study both the current relative fine-tuning of each scenario, and the future prospects. Noting that the different scenarios behave differently with respect to future improvements in collider measurements, we find that the MCHM14 − 1 − 105 − 5 − 5 enjoys a relatively low increase in fine tuning even for a future lower bound on the top partner masses of 3.4 TeV (or equivalently a maximum Higgs-fermion or Higgs-gluon coupling deviation of 2%).James Barnard, Daniel Murnane, Martin White, Anthony G. William

A field based method for pre-concentration of micro organics using solid phase extraction

British Geological Survey (BGS) have been researching micro-organic pollutants for many years in the UK (Gooddy et al 2004, Stuart et al 2012, White et al 2016) and overseas (Sorensen et al 2015). A hindrance to the research, especially overseas, has been the need to transport large volumes of water back to the laboratory and the worry of degradation during transportation prior to LCMS or GCMS analysis. The first step in the LCMS analytical procedure is the solid phase extraction of the micro-organic contaminants onto a small cartridge. This report details the field trial where by BGS, working in conjunction with NLS, carried out the pre-concentration step of sample processing in the field. NLS provided pre-conditioned sorbent Oasis® HLB cartridges supplied in sealed Corning centristar centrifuge tubes. Water samples were run through the cartridges by the field team using a small peristaltic pump prior to sending to NLS for semi-quantative broad screen LCMS analysis. To check the repeatability and the stability of this method the sorbed samples were analysed in duplicate and replicate analysis was carried out over set periods after storage for up to a month. The results from the duplicate replicates are compared to results from the original water sample analysed immediately after sampling. Laboratory and field equipment blanks were included in the trial to check for any contamination introduced by the sampling method and extraction process. Preliminary results demonstrate that for a large range of compounds, and different types of matrices, this method was able to preserve samples for up to a month. Once the procedure had been validated, it was used to investigate the occurrence of micro-pollutants in a rural groundwater, estuarine waters and a range of surface waters receiving treated sewerage outflows. The work was funded under the BGS Development Capabilities programme, and was also supported by the BGS Groundwater Science programme under the Groundwater Protection team. Analytical aspects of this work was undertaken in collaboration with Wayne Civil based at Star Cross National Science Laboratory (NLS)

Hydrologic Transport of Dissolved Inorganic Carbon and Its Control on Chemical Weathering

Chemical weathering is one of the major processes interacting with climate and tectonics to form clays, supply nutrients to soil microorganisms and plants, and sequester atmospheric CO2. Hydrology and dissolution kinetics have been emphasized as factors controlling chemical weathering rates. However, the interaction between hydrology and transport of dissolved inorganic carbon (DIC) in controlling weathering has received less attention. In this paper, we present an analytical model that couples subsurface water and chemical molar balance equations to analyze the roles of hydrology and DIC transport on chemical weathering. The balance equations form a dynamical system that fully determines the dynamics of the weathering zone chemistry as forced by the transport of DIC. The model is formulated specifically for the silicate mineral albite, but it can be extended to other minerals, and is studied as a function of percolation rate and water transit time. Three weathering regimes are elucidated. For very small or large values of transit time, the weathering is limited by reaction kinetics or transport, respectively. For intermediate values, the system is transport controlled and is sensitive to transit time. We apply the model to a series of watersheds for which we estimate transit times and identify the type of weathering regime. The results suggest that hydrologic transport of DIC may be as important as reaction kinetics and dilution in determining chemical weathering rates

Modelling trade offs between public and private conservation policies

To reduce global biodiversity loss, there is an urgent need to determine the most efficient allocation of conservation resources. Recently, there has been a growing trend for many governments to supplement public ownership and management of reserves with incentive programs for conservation on private land. At the same time, policies to promote conservation on private land are rarely evaluated in terms of their ecological consequences. This raises important questions, such as the extent to which private land conservation can improve conservation outcomes, and how it should be mixed with more traditional public land conservation. We address these questions, using a general framework for modelling environmental policies and a case study examining the conservation of endangered native grasslands to the west of Melbourne, Australia. Specifically, we examine three policies that involve: i) spending all resources on creating public conservation areas; ii) spending all resources on an ongoing incentive program where private landholders are paid to manage vegetation on their property with 5-year contracts; and iii) splitting resources between these two approaches. The performance of each strategy is quantified with a vegetation condition change model that predicts future changes in grassland quality. Of the policies tested, no one policy was always best and policy performance depended on the objectives of those enacting the policy. This work demonstrates a general method for evaluating environmental policies and highlights the utility of a model which combines ecological and socioeconomic processes.Comment: 20 pages, 5 figure

Diversity of thermal responses of lipid composition in the membranes of the dominant culturable members of an Antarctic fellfield soil bacterial community

The eight dominant culturable members of an Antarctic fellfield soil bacterial community were four Arthrobacter species, Sanguibacter suarezii, Aureobacterium testaceum, a Bacillus sp., and a Pseudomonas sp.. All of the isolates grew at 2°C, but two of the Arthrobacter spp. were psychrophilic, while the other six bacterial species were psychrotolerant. However, the fastest growing organisms at low temperatures were not the psychrophiles, and the psychrotolerant Bacillus sp. grew fastest at temperatures up to 25°C. When the growth temperature of cultures was altered, the phospholipid content of the two psychrophilic Arthrobacter spp. decreased, whereas the phospholipid contents of the psychrotolerant spp. either increased or did not change. Only one psychrophilic and one psychrotolerant Arthrobacter sp. modified its polar lipid head-group composition in response to a lowering of growth temperature. The change in Arthrobacter sp. CL2-1 was particularly marked and novel in that at low temperatures phosphatidylethanolamine was replaced completely by a phosphoglycolipid and phosphatidylserine, neither of which was present at higher growth temperatures. All eight isolates altered the fatty acyl compositions of their membrane lipids in a manner that was only partially dependent on taxonomic status. In Bacillus sp. C2-1 the changes were opposite to that predicted on the basis of membrane fluidity considerations. The isolates used different combinations of changes in fatty acid branching, unsaturation and chain length. There was no single strategy of thermal adaptation that was employed and the variety of strategies used did not follow phylogenetic boundaries

Large-Scale QSO-Galaxy Correlations and Weak Lensing

Several recent studies show that bright, intermediate and high redshift optically and radio selected QSOs are positively correlated with nearby galaxies on a range of angular scales up to a degree. Obscuration by unevenly distributed Galactic dust can be ruled out as the cause, leaving weak statistical lensing as the physical process responsible. However the amplitude of correlations on < 1 degree scales is at least a factor of a few larger than lensing model predictions. A possible way to reconcile the observations and theory is to revise the weak lensing formalism. We extend the standard lensing formulation to include the next higher order term (second order) in the geodesic equation of motion for photons. We derive relevant equations applicable in the weak lensing regime, and discuss qualitative properties of the updated formulation. We then perform numerical integrations of the revised equation and study the effect of the extra term using two different types of cosmic mass density fluctuations. We find that nearby large-scale coherent structures increase the amplitude of the predicted lensing-induced correlations between QSOs and foreground galaxies by ~ 10% (not a factor of several required by observations), while the redshift of the optimal, i.e. `most correlated' structures is moved closer to the observer compared to what is predicted using the standard lensing equation.Comment: extended Section 2; 20 pages, including 4 figures, accepted to Ap

High resolution CO J = 3-2 observations of L 1551: fragmentary structure in the outflowing shell

We present high-resolution observations of the 12CO J = 3-2 emission associated with HH102 in the L1551 molecular outflow. At low and intermediate blue-shifted velocities the emission is found in a shell which coincides with the optical reflection nebulosity from HH102. In places, the shell appears to be unresolved, implying a width of less than ~ 0.01 pc. Within the shell several bright clumps can be identified. By combining the J = 3-2 data with previous J = 1-0 maps, we derive excitation temperatures and beam-filling factors for these clumps. The gas is found to be hot (up to ~ 40 K) and often has low filling factor (~ 0.2). We compare the distribution of the CO emission with those of the optical reflection nebulosity and the Hα shocked emission. The data are consistent with a fast wind from IRS5 being shocked immediately in front of the boundary between the wind-eroded cavity and the swept-up molecular gas. We suggest that the particularly energetic activity in the vicinity of HH102 is a result of the direct impact of material in a fast, collimated jet such as those traced by the radio jets emanating from IRS5. If so, previous interpretations of the presence of both red- and blue-shifted CO around HH102 may be incorrect. In particular, the data need not be explained as solely due to the presence of a slow rotation of the outflow about its axis

Simple phosphinate ligands access zinc clusters identified in the synthesis of zinc oxide nanoparticles

The bottom-up synthesis of ligand-stabilized functional nanoparticles from molecular precursors is widely applied but is difficult to study mechanistically. Here we use 31P NMR spectroscopy to follow the trajectory of phosphinate ligands during the synthesis of a range of ligated zinc oxo clusters, containing 4, 6 and 11 zinc atoms. Using an organometallic route, the clusters interconvert rapidly and self-assemble in solution based on thermodynamic equilibria rather than nucleation kinetics. These clusters are also identified in situ during the synthesis of phosphinate-capped zinc oxide nanoparticles. Unexpectedly, the ligand is sequestered to a stable Zn11 cluster during the majority of the synthesis and only becomes coordinated to the nanoparticle surface, in the final step. In addition to a versatile and accessible route to (optionally doped) zinc clusters, the findings provide an understanding of the role of well-defined molecular precursors during the synthesis of small (2–4 nm) nanoparticles