Identifying the major variables controlling transport of water and analytes from an alluvial aquifer to streams

Reliable information on groundwater (GW) lateral flow characteristics is required for estimation of GW extraction, environmental flow requirements, contaminant loading from GW to surface water bodies (SWB), and aquifer remediation purposes. Lateral flow from a shallow alluvial aquifer was investigated applying parametric and non-parametric statistics to flux-theory based outputs obtained using time series hydraulic head (HH) and analyte concentration data. The emphasis of the investigation was to identify the major variables that control the export of contaminants from GW to SWB. Point measurements from 4 shallow wells (10-12 m deep) installed along a 1.1 km transect perpendicularly crossing a creek were undertaken at 7 - 12 day intervals from January through June (wet season) over 3 years in a wet tropical catchment in north-eastern Australia. The HH during two wet seasons at north upslope varied from 4.84 m to 12.37 m with mean, median, and coefficient of variation (CV) of 8.86 m, 8.73 m, and 17% respectively. At the downslope the corresponding values were 3.59-6.21 m, 4.81 m, 4.58 m, and 13%, respectively. Similar temporal trends were observed at the south upslope and downslopes. Nitrate-N concentrations at the north upslope varied from 23 to 1340 µg L-1 with mean, median, and CV of 691 µg L-1, 609 µg L-1 and 23%, respectively. Similar trends were observed at north downslope and at up- and down-slopes of southern transect. The lateral hydraulic gradient (LHG) from north upslope to downslope varied from 4.12 x 10-3 to 9.92 x 10-3 m m-1 and the corresponding flow velocity (Vx) from 3.63 x 10-3 to 3.48 x 10-2 m d-1. Nitrate-N flux from north upslope to downslope varied from 1.0 x 10-4 to 4.4 x10-3 g m-2 d-1, similar trends were observed for EC and Cl and also along southern transect. These suggest that analyte fluxes followed the LHG indicating conservative transport of the former from upslopes to downslopes. The conservative transport was reconfirmed by significant associations between HH and analyte fluxes; R2 18-70% for EC, 24-52% for Cl, and 52-76% for nitrate. Travel time for 650 m, computed using mean Vx varied from 5.8 to 69 yrs and the variations depended on the values of saturated soil hydraulic conductivity (Ks) used. The results indicate contaminant export extrapolations from point measurements to landscape scales depended on our ability to incorporate spatial and temporal variabilities in Vx and analyte fluxes, reliable information in Ks, and macropore bypass flow. We believe this is one of the few studies that have coupled flux-theory and statistics to identify and assess the major variables that control contaminant export from GW to SWB

δ13C provides a robust indicator of the sources of suspended sediment in a tropical river traversing forested and agricultural land

Degradation of freshwater and marine ecosystems by sediment and associated pollutants is widespread, We set out to determine the sources of suspended sediment, using composite fingerprinting, in the Tully River, which discharges into the Great Barrier Reef lagoon. Samples of suspended sediment combined over a whole wet season were taken from the Tully River and two of its main tributaries, Samples of potential source material were taken from 102 sites covering several land use and geological categories. When all 23 measured properties (mostly total elemental contents) were included in the fingerprint, 50% of the suspended sediment in the Tully River was attributed to sugarcane surface soil, 15% to other land uses, and 35% to channels, which are all in sugarcane growing areas on Quaternary alluvium and colluvium. However, mean relative errors were quite high. When mineral properties were excluded from the fingerprint, land use sources could be discriminated with reduced mean relative errors, δ13C separated forest versus sugarcane, and 613C in combination with C:N ratio separated surface soil versus channels. Fingerprints based on organic properties attributed >60% of suspended sediment to channel erosion. The results show that caution is needed when applying and interpreting the composite fingerprinting approach in some environments

Approximation of excitonic absorption in disordered systems using a compositional component weighted CPA

Employing a recently developed technique of component weighted two particle Green's functions in the CPA of a binary substitutional alloy $A_cB_{1-c}$ we extend the existing theory of excitons in such media using a contact potential model for the interaction between electrons and holes to an approximation which interpolates correctly between the limits of weak and strong disorder. With our approach we are also able to treat the case where the contact interaction between carriers varies between sites of different types, thus introducing further disorder into the system. Based on this approach we study numerically how the formation of exciton bound states changes as the strengths of the contact potentials associated with either of the two site types are varied through a large range of parameter values.Comment: 27 pages RevTeX (preprint format), 13 Postscript figure file

Simulation Studies on Arrival Time Distributions of Cherenkov Photons in Extensive Air Showers

Atmospheric Cherenkov technique is an established methodology to study TeV energy gamma rays. Here we carry out systematic monte carlo simulation studies of the timing information of Cherenkov photons. Extensive studies have already been carried out in this regard. Most of these are carried out at higher energies with the aim of studying the elemental composition of cosmic rays. However not much attention is paid to the species dependent signatures at TeV energies. In this work, functional fits have been carried out to the spherical Cherenkov shower fronts and the radii of curvature have been found to be equal to the height of shower maximum irrespective of the species or the observation level. Functional fits have also been carried out to describe the pulse shapes at various core distances in terms of well known probability density distribution functions (PDF). Two types of PDF's have been tried viz. gamma function and lognormal function. The variation of the pulse shape parameters as a function of primary energy, observation height and incident angles have been studied. The possibility of deriving the pulse shape parameters like the rise & decay times, full width at half maximum from the easily measurable quantities like the mean and RMS variation of photon arrival times offers a very important new technique which can be easily applied in an observation.Comment: 34 pages, 14 figures, accepted for publication in Astroparticle Physic

Dynamic Image-Based Modelling of Kidney Branching Morphogenesis

Kidney branching morphogenesis has been studied extensively, but the mechanism that defines the branch points is still elusive. Here we obtained a 2D movie of kidney branching morphogenesis in culture to test different models of branching morphogenesis with physiological growth dynamics. We carried out image segmentation and calculated the displacement fields between the frames. The models were subsequently solved on the 2D domain, that was extracted from the movie. We find that Turing patterns are sensitive to the initial conditions when solved on the epithelial shapes. A previously proposed diffusion-dependent geometry effect allowed us to reproduce the growth fields reasonably well, both for an inhibitor of branching that was produced in the epithelium, and for an inducer of branching that was produced in the mesenchyme. The latter could be represented by Glial-derived neurotrophic factor (GDNF), which is expressed in the mesenchyme and induces outgrowth of ureteric branches. Considering that the Turing model represents the interaction between the GDNF and its receptor RET very well and that the model reproduces the relevant expression patterns in developing wildtype and mutant kidneys, it is well possible that a combination of the Turing mechanism and the geometry effect control branching morphogenesis

Cerenkov Photon Density Fluctuations in Extensive Air Showers

The details of Cerenkov light produced by a gamma ray or a cosmic ray incident at the top of the atmosphere is best studied through systematic simulations of the extensive air showers. Recently such studies have become all the more important in view of the various techniques resulting from such studies, to distinguish gamma ray initiated showers from those generated by much more abundant hadronic component of cosmic rays. We have carried out here such systematic simulation studies using CORSIKA package in order to understand the Cerenkov photon density fluctuations for 5 different energies at various core distances both for gamma ray and proton primaries incident vertically at the top of the atmosphere. Such a systematic comparison of shower to shower density fluctuations for gamma ray and proton primaries is carried out for the first time here. It is found that the density fluctuations are significantly non-Poissonian. Such fluctuations are much more pronounced in the proton primaries than gamma ray primaries at all energies. The processes that contribute significantly to the observed fluctuations have been identified. It has been found that significant contribution to fluctuations comes from photons emitted after shower maximum. The electron number fluctuations and correlated emission of Cerenkov photons are mainly responsible for the observed fluctuations.Comment: 31 pages, latex, 16 figures in ps files, Accepted for publication in "Astroparticle Physics

CASSETTE—clindamycin adjunctive therapy for severe Staphylococcus aureus treatment evaluation: Study protocol for a randomised controlled trial

Background Exotoxins are important virulence factors in Staphylococcus aureus. Clindamycin, a protein synthesis inhibitor antibiotic, is thought to limit exotoxin production and improve outcomes in severe S. aureus infections. However, randomised prospective data to support this are lacking. Methods An open-label, multicentre, randomised controlled trial (RCT) will compare outcome differences in severe S. aureus infection between standard treatment (flucloxacillin/cefazolin in methicillin-susceptible S. aureus; and vancomycin/daptomycin in methicillin-resistant S. aureus) and standard treatment plus an additional clindamycin given for 7 days. We will include a minimum of 60 participants (both adult and children) in the pilot study. Participants will be enrolled within 72 h of an index culture. Severe infections will include septic shock, necrotising pneumonia, or multifocal and non-contiguous skin and soft tissue/osteoarticular infections. Individuals who are immunosuppressed, moribund, with current severe diarrhoea or Clostridiodes difficile infection, pregnant, and those with anaphylaxis to β-lactams or lincosamides will be excluded. The primary outcomes measure is the number of days alive and free (1 or 0) of systemic inflammatory response syndrome (SIRS) within the first 14 days post randomisation. The secondary outcomes measure will include all-cause mortality at 14, 42, and 90 days, time to resolution of SIRS, proportion with microbiological treatment failure, and rate of change of C-reactive protein over time. Impacts of inducible clindamycin resistance, strain types, methicillin susceptibility, and presence of various exotoxins will also be analysed. Discussion This study will assess the effect of adjunctive clindamycin on patient-centred outcomes in severe, toxin-mediated S. aureus infections. The pilot study will provide feasibility for a much larger RCT. Trial registration Australian New Zealand Clinical Trials Registry, ACTRN12617001416381p. Registered on 6 October 2017

Space-Time Distribution of G-Band and Ca II H-Line Intensity Oscillations in Hinode/SOT-FG Observations

We study the space-time distributions of intensity fluctuations in 2 - 3 hour sequences of multi-spectral, high-resolution, high-cadence broad-band filtergram images (BFI) made by the SOT-FG system aboard the Hinode spacecraft. In the frequency range 5.5 < f < 8.0 mHz both G-band and Ca II H-line oscillations are suppressed in the presence of magnetic fields, but the suppression disappears for f > 10 mHz. By looking at G-band frequencies above 10 mHz we find that the oscillatory power, both at these frequencies and at lower frequencies too, lies in a mesh pattern with cell scale 2 - 3 Mm, clearly larger than normal granulation, and with correlation times on the order of hours. The mesh pattern lies in the dark lanes between stable cells found in time-integrated G-band intensity images. It also underlies part of the bright pattern in time-integrated H-line emission. This discovery may reflect dynamical constraints on the sizes of rising granular convection cells together with the turbulence created in strong intercellular downflows.Comment: 24 pages, 15 figure

Phase Transitions of Hard Disks in External Periodic Potentials: A Monte Carlo Study

The nature of freezing and melting transitions for a system of hard disks in a spatially periodic external potential is studied using extensive Monte Carlo simulations. Detailed finite size scaling analysis of various thermodynamic quantities like the order parameter, its cumulants etc. are used to map the phase diagram of the system for various values of the density and the amplitude of the external potential. We find clear indication of a re-entrant liquid phase over a significant region of the parameter space. Our simulations therefore show that the system of hard disks behaves in a fashion similar to charge stabilized colloids which are known to undergo an initial freezing, followed by a re-melting transition as the amplitude of the imposed, modulating field produced by crossed laser beams is steadily increased. Detailed analysis of our data shows several features consistent with a recent dislocation unbinding theory of laser induced melting.Comment: 36 pages, 16 figure

Clindamycin adjunctive therapy for severe Staphylococcus aureus treatment evaluation (CASSETTE)—an open-labelled pilot randomized controlled trial

Background Combination antibiotic therapy with an antitoxin agent, such as clindamycin, is included in some guidelines for severe, toxin-mediated Staphylococcus aureus infections. The evidence to support this practice is currently limited to in vitro, animal and observational human case-series data, with no previous randomized controlled trials (RCTs). Objectives This pilot RCT aimed to determine the feasibility of conducting a clinical trial to examine if adjunctive clindamycin with standard therapy has greater efficacy than standard therapy alone for S. aureus infections. Methods We performed an investigator-initiated, open-label, multicentre, pilot RCT (ACTRN12617001416381p) in adults and children with severe S. aureus infections, randomized to standard antibiotic therapy with or without clindamycin for 7 days. Results Over 28 months, across nine sites, 127 individuals were screened and 34 randomized, including 11 children (32%). The primary outcome—number of days alive and free of systemic inflammatory response syndrome ≤14 days—was similar between groups: clindamycin (3 days [IQR 1–6]) versus standard therapy (4 days [IQR 0–8]). The 90 day mortality was 0% (0/17) in the clindamycin group versus 24% (4/17) in the standard therapy group. Secondary outcomes—microbiological relapse, treatment failure or diarrhoea—were similar between groups. Conclusions As the first clinical trial assessing adjunctive clindamycin for S. aureus infections, this study indicates feasibility and that adults and children can be incorporated into one trial using harmonized endpoints, and there were no safety concerns. The CASSETTE trial will inform the definitive S. aureus Network Adaptive Platform (SNAP) trial, which includes an adjunctive clindamycin domain and participants with non-severe disease