Single-well injection-withdrawal tests as a contaminant transport characterisation tool for landfilled waste.

A new single well injection withdrawal (SWIW) test was trialled at four landfills using the tracers lithium and deuterium, and by injecting clean water and measuring electrical conductivity. The aim of the research was to develop a practical test for measuring lateral contaminant transport to aid in the design of landfill flushing. Borehole dilution tests using dyes were undertaken prior to each SWIW test to determine background flow velocities. SWIW tests were performed at different scales by varying the volume of tracer injected (1 to 5,800 m3) and the test duration (2 to 266 days). Tracers were used individually, simultaneously or sequentially to examine repeatability and scaling. Mobile porosities, estimated from first arrival times in observation wells and from model fitting ranged from 0.02 to 0.14. The low mobile porosities measured rule out a purely advective-dispersive system and support a conceptual model of a highly preferential dual-porosity flow system with localised heterogeneity. A dual-porosity model was used to interpret the results. The model gave a good fit to the test data in 7 out of 11 tests (where R2 ≥ 0.98), and the parameters derived are compatible with previous experiments in MSW. Block diffusion times were estimated to range from 12 to 6,630 h, with a scaling relationship apparent between the size of the test (volume of tracer used and/or the duration) and the observed block diffusion time. This scaling relationship means affordable small-scale tests can inform larger-scale flushing operations.

Nodeless superconductivity in the cage-type superconductor Sc5Ru6Sn18 with preserved time-reversal symmetry.

We report the single-crystal synthesis and detailed investigations of the cage-type superconductor Sc5Ru6Sn18, using powder x-ray diffraction (XRD), magnetization, specific-heat and muon-spin relaxation (µSR) measurements. Sc5Ru6Sn18 crystallizes in a tetragonal structure (space group I41/acd) with lattice parameters a = 1.387(3) nm and c = 2.641(5) nm. Both DC and AC magnetization measurements prove the type-II superconductivity in Sc5Ru6Sn18 with T c ≈ 3.5(1) K, a lower critical field [Formula: see text] = 157(9) Oe and an upper critical field, [Formula: see text] = 26(1) kOe. The zero-field electronic specific-heat data are well fitted using a single-gap BCS model, with [Formula: see text] = 0.64(1) meV. The Sommerfeld constant γ varies linearly with the applied magnetic field, indicating s-wave superconductivity in Sc5Ru6Sn18. Specific-heat and transverse-field (TF) µSR measurements reveal that Sc5Ru6Sn18 is a superconductor with strong electron-phonon coupling, with TF-µSR also suggesting a single-gap s-wave character of the superconductivity. Furthermore, zero-field µSR measurements do not detect spontaneous magnetic fields below T c, hence implying that time-reversal symmetry is preserved in Sc5Ru6Sn18.

Superconducting properties and µSR study of the noncentrosymmetric superconductor Nb0.5Os0.5.

The properties of the noncentrosymmetric superconductor (α-[Formula: see text] structure) Nb0.5Os0.5 have been investigated using resistivity, magnetization, specific heat, and muon spin relaxation and rotation (µSR) measurements. These measurements suggest that Nb0.5Os0.5 is a weakly coupled ([Formula: see text]) type-II superconductor ([Formula: see text]), having a bulk superconducting transition temperature T c = 3.07 K. The specific heat data fits well with the single-gap BCS model indicating nodeless s-wave superconductivity in Nb0.5Os0.5. The µSR measurements also confirm [Formula: see text]-wave superconductivity with the preserved time-reversal symmetry.

Time-Reversal Symmetry Breaking in Re-Based Superconductors.

To trace the origin of time-reversal symmetry breaking (TRSB) in Re-based superconductors, we performed comparative muon-spin rotation and relaxation (µSR) studies of superconducting noncentrosymmetric Re_{0.82}Nb_{0.18} (T_{c}=8.8 K) and centrosymmetric Re (T_{c}=2.7 K). In Re_{0.82}Nb_{0.18}, the low-temperature superfluid density and the electronic specific heat evidence a fully gapped superconducting state, whose enhanced gap magnitude and specific-heat discontinuity suggest a moderately strong electron-phonon coupling. In both Re_{0.82}Nb_{0.18} and pure Re, the spontaneous magnetic fields revealed by zero-field µSR below T_{c} indicate time-reversal symmetry breaking and thus unconventional superconductivity. The concomitant occurrence of TRSB in centrosymmetric Re and noncentrosymmetric ReT (T=transition metal), yet its preservation in the isostructural noncentrosymmetric superconductors Mg_{10}Ir_{19}B_{16} and Nb_{0.5}Os_{0.5}, strongly suggests that the local electronic structure of Re is crucial for understanding the TRSB superconducting state in Re and ReT. We discuss the superconducting order parameter symmetries that are compatible with the experimental observations.

Doublet tracer tests to determine the contaminant flushing properties of a municipal solid waste landfill.

This paper describes a programme of research investigating horizontal fluid flow and solute transport through saturated municipal solid waste (MSW) landfill. The purpose is to inform engineering strategies for future contaminant flushing. Solute transport between injection/abstraction well pairs (doublets) is investigated using three tracers over five separate tests at well separations between 5m and 20m. Two inorganic tracers (lithium and bromide) were used, plus the fluorescent dye tracer, rhodamine-WT. There was no evidence for persistent preferential horizons or pathways at the inter-well scale. The time for tracer movement to the abstraction wells varied with well spacing as predicted for a homogeneous isotropic continuum. The time for tracer movement to remote observation wells was also as expected. Mobile porosity was estimated as ~0.02 (~4% of total porosity). Good fits to the tracer breakthrough data were achieved using a dual-porosity model, with immobile regions characterised by block diffusion timescales in the range of about one to ten years. This implies that diffusional exchanges are likely to be very significant for engineering of whole-site contaminant flushing and possibly rate-limiting.

Unconventional Superconductivity in La(7)Ir(3) Revealed by Muon Spin Relaxation: Introducing a New Family of Noncentrosymmetric Superconductor That Breaks Time-Reversal Symmetry.

The superconductivity of the noncentrosymmetric compound La(7)Ir(3) is investigated using muon spin rotation and relaxation. Zero-field measurements reveal the presence of spontaneous static or quasistatic magnetic fields below the superconducting transition temperature T(c)=2.25 K-a clear indication that the superconducting state breaks time-reversal symmetry. Furthermore, transverse-field rotation measurements suggest that the superconducting gap is isotropic and that the pairing symmetry of the superconducting electrons is predominantly s wave with an enhanced binding strength. The results indicate that the superconductivity in La(7)Ir(3) may be unconventional and paves the way for further studies of this family of materials.

Incidence, treatment and outcome of rectal stenosis following transanal endoscopic microsurgery.

BACKGROUND: As an alternative to more radical abdominal surgery, transanal endoscopic microsurgery (TEM) offers a minimally invasive solution for the excision of certain rectal polyps and early-stage rectal tumours. The patient benefits of TEM as compared to radical abdominal surgery are clear; nevertheless, some drawback is possible. The aim of our study was to determine the risk factors, treatment and outcomes of rectal stenosis following TEM. METHODS: We analysed a series of 354 consecutive patients who underwent TEM for benign or malignant rectal tumours between 1997 and 2009. We recorded the maximum histological diameter of the lesion, and whether the lesion was circumferential. Rectal stenosis was defined as a rectal narrowing not allowing passage of a 12 mm sigmoidoscope. RESULTS: Histological results with a measured specimen diameter were available in 304 of the 354 cases. There were 11 stenoses in total (3.6%), 7 stenoses due to 9 circumferential lesions (78%) and 4 due to lesions with a maximum diameter ≥ 5 cm (3.2%). Two patients presented as emergencies, and the other 9 patients reported symptoms of increased stool frequency at follow-up. Three of the stenoses were associated with recurrent disease. All stenoses were treated by a combination of endoscopic/radiological balloon dilatation or surgically with Hegar's dilators. A median of two procedures were required to treat stenoses until resolution of symptoms. CONCLUSIONS: Rectal stenosis following TEM excision is rare. It is predictable in patients with circumferential lesions but is rare in patients with non-circumferential lesions with a maximum diameter ≥ 5 cm. It is effectively treated with surgical or balloon dilatation. Most patients require repeated treatments.

Supralevator fistula-in-ano in tuberculosis.

AIM: Perianal Mycobacterium tuberculosis is rare, but tuberculosis (TB) is now endemic in many areas of the world. It is essential to recognize TB to institute appropriate management. We report three cases of TB presenting with supralevator abscess. METHOD: We analysed the outcomes of three patients who presented to our unit, from 2004 to 2009, with supralevator abscess caused by TB. RESULTS: The patients presented as emergencies with symptoms of per-anal sepsis. All required multiple drainage procedures. Supralevator extension was confirmed clinically and radiologically (by magnetic resonance imaging in two patients and by computed tomography scanning in one patient). One patient was diagnosed by perianal biopsy, the second by culture of pus and the third by sputum culture. Following drainage, all three patients were given anti-TB medication for 6 months. In all patients, the fistulae had high communication with the anal canal. In one patient, local drainage and medical therapy led to sepsis resolution, the second patient has residual complex fistulae and the third patient has recently commenced antimicrobial therapy. CONCLUSION: As TB is endemic in many parts of Europe, TB should be suspected in patients with complex and/or recurrent perianal sepsis. Samples for histological and bacteriological analyses should be obtained from these patients. Recurrent perianal drainage procedures are likely to be required, and sepsis may persist after anti-TB therapy.

A tracer methodology for identifying ambient flows in boreholes.

Identifying flows into, out of, and across boreholes is important for characterizing aquifers, determining the depth at which water enters boreholes, and determining the locations and rates of outflow. This study demonstrates how Single Borehole Dilution Tests (SBDTs) carried out under natural head conditions provide a simple and cheap method of identifying vertical flow within boreholes and determining the location of in-flowing, out-flowing, and cross-flowing fractures. Computer simulations were used to investigate the patterns in tracer profiles that arise from different combinations of flows. Field tracer tests were carried out using emplacements of a saline tracer throughout the saturated length of boreholes and also point emplacements at specific horizons. Results demonstrated that SBDTs can be used to identify flowing fractures at the top and bottom of sections of vertical flow, where there is a change in vertical flow rate within a borehole, and also where there are consistent decreases in tracer concentration at a particular depth. The technique enables identification of fractures that might be undetected by temperature and electrical conductance logging, and is a simple field test that can be carried out without pumping the borehole.

Generalized diffusion equation for anisotropic anomalous diffusion.

Motivated by studies of comblike structures, we present a generalization of the classical diffusion equation to model anisotropic, anomalous diffusion. We assume that the diffusive flux is given by a diffusion tensor acting on the gradient of the probability density, where each component of the diffusion tensor can have its own scaling law. We also assume scaling laws that have an explicit power-law dependence on space and time. Solutions of the proposed generalized diffusion equation are consistent with previously derived asymptotic results for the probability density on comblike structures.

Redistribution of contaminants by a fluctuating water table in a micro-porous, double-porosity aquifer: field observations and model simulations.

Large seasonal fluctuations of the water table are characteristic of aquifers with a low specific yield, including those fractured, double-porosity aquifers that have significant matrix porosity containing virtually immobile porewater, such as the Chalk of northern Europe. Where these aquifers are contaminated, a strong relationship between water table elevation and contaminant concentration in groundwater is commonly observed, of significance to the assessment, monitoring, and remediation of contaminated groundwater. To examine the processes governing contaminant redistribution by a fluctuating water table within the 'seasonally unsaturated zone', or SUZ, profiles of porewater solute concentrations have been established at a contaminated site in southern England. These profiles document the contaminant distribution in porewater of the Chalk matrix over the SUZ at a greater level of detail than recorded previously. A novel double-porosity solute transport code has been developed to simulate the evolution of the SUZ matrix porewater contaminant profiles, given a fluctuating water table, when the groundwater is initially contaminated and the SUZ is initially free of contamination. The model is simply characterised by: the matrix-fracture porosity ratio, the matrix block geometry, and a characteristic diffusion time. De-saturation and re-saturation of fractures is handled by a new approximation method. Contaminant accumulates in the upper levels of the SUZ, where it is less accessible to mobile groundwater, and acts as a persistent secondary source of contamination once the original source of contamination has been removed or has become depleted. The 'SUZ process' first attenuates the progress of contaminants in groundwater, and subsequently controls the slow release of contamination back to the mobile groundwater, thus prolonging the duration of groundwater contamination by many years. The SUZ process should operate in any fractured, micro-porous lithology e.g. fractured clays and mudstones, making this approach widely applicable.

Life-threatening upper airway edema caused by a distal rattlesnake bite.

A 36-year-old man captured a timber rattlesnake and was accidentally envenomated in the thumb by the severed head. At a local emergency department, hypotension and confusion developed. Facial and glossal edema were also observed. Oxygen was delivered by face mask, and crystalloids and dopamine were administered. Respiratory distress developed with progressive hypoxemia. Intubation was unsuccessful because of massive glossal and epiglottic (laryngeal) edema, and an emergency cricothyrotomy was performed. High-dose antivenom therapy was administered, and mechanical ventilation was started. Recovery was rapid, and the patient was discharged from the hospital a week later. This is the first report of life-threatening upper airway edema caused by snake envenomation not in the vicinity of the head or neck.

Inverted electron-hole alignment in InAs-GaAs self-assembled quantum dots.

New information on the electron-hole wave functions in InAs-GaAs self-assembled quantum dots is deduced from Stark effect spectroscopy. Most unexpectedly it is shown that the hole is localized towards the top of the dot, above the electron, an alignment that is inverted relative to the predictions of all recent calculations. We are able to obtain new information on the structure and composition of buried quantum dots from modeling of the data. We also demonstrate that the excited state transitions arise from lateral quantization and that tuning through the inhomogeneous distribution of dot energies can be achieved by variation of electric field.

Cytogenetics and the biological basis of sarcomas.

Recently, much research has been directed toward gaining a better understanding of sarcoma biology. To accomplish this goal, researchers have focused on characterizing the cytogenetic abnormalities that are detectable by routine karyotyping. With the use of widely-available molecular biologic tools, new information on the genetic abnormalities of sarcomas is rapidly emerging. In addition, physicians are beginning to successfully apply cytogenetic and molecular biologic findings to clinical settings in the form of molecular diagnostic and prognostic tests. Moreover, detailed study of these genetic abnormalities is leading to a better understanding of the molecular pathology of sarcomas, which may eventually lead to better therapy. In this paper, we will review the important new findings on genetic abnormalities in sarcomas, clinical applications of cytogenetic studies, and insight into the biology of sarcomas.

Microcytic anemia with iron malabsorption: an inherited disorder of iron metabolism.

Two siblings were identified with severe hypoproliferative microcytic anemia and iron malabsorption, in the absence of any gastrointestinal disorder or blood loss. These children had severe microcytosis (MCV 48 fl, hemoglobin 7.5 g/dl) with decreased serum iron, elevated serum TIBC, and decreased serum ferritin, despite prolonged treatment with oral iron. An iron challenge study with an oral dose of 2 mg/kg elemental iron as ferrous sulfate documented iron malabsorption. After treatment with intravenous iron dextran, there was an absence of the expected reticulocytosis and only a partial correction of the hemoglobin, hematocrit, and microcytosis. The bone marrow was hypocellular with abnormal iron incorporation into erythroid precursor cells. This appears to be a rare form of inherited anemia characterized by iron malabsorption and disordered iron metabolism that only partially corrects after the administration of parenteral iron. These features resemble those found in the microcytic mouse (mk/mk), which also has severe microcytic anemia and iron malabsorption that partially responds to parenteral iron.

Forage characteristics, steer performance, and water quality from bermudagrass pastures fertilized with two levels of nitrogen from swine lagoon effluent.

Four .8-ha pastures of bermudagrass (Cynodon dactylon [L.] Pers.) were fertilized with either 456 or 873 kg/ha of nitrogen (N) from swine lagoon effluent (two replicates per treatment) and grazed by steers over two summers. Within each pasture, steers received forage only, an energy source (corn), a mixture of corn and soybean meal, or a mixture of corn and blood meal via electronic Calan feeders. All supplements were offered at a level of 1.36 kg/d, and the soybean meal and blood meal supplements provided similar among quantities of protein. Weight gains were similar among supplemented steers, but supplemented steers gained faster (P < .05) than controls. Nitrogen fertilization level had no effect on steer gains, steer grazing days per hectare, or in vitro dry matter disappearance, NDF, and ADF of clipped forage samples. Plant protein and nitrate ion concentrations were greater (P < .06) in clipped forage samples receiving the higher N application rate. Nitrate ion concentrations were greater in available forage samples from the pastures with the high N application rate. Mean total N and nitrate N concentrations were similar in water samples obtained from monitoring wells for the two N treatments over the 2 yr and there were no year x N interactions. Chloride concentrations were greater (P < .05) and pH and specific conductance were less in water samples collected from the 873 kg than from the 456 kg/ha N treatment. Long-term studies are needed to examine the possible cumulative effects of applying various levels of swine waste to the same land area.

Genotoxic activity of 1-chloromethylpyrene in stomach epithelium in vivo: insensitivity of the stomach scintillation UDS assay.

An acknowledged weakness of current testing programmes for genotoxic hazard has been the potential insensitivity of the established mouse bone marrow micronucleus test and rat liver unscheduled DNA synthesis (UDS) assays to direct-acting or short-lived mutagens, which may be consumed at the site of initial contact. In such cases, in vivo test systems sampling tissues such as the skin or the stomach would provide valuable data. To test these principles a stomach UDS assay was evaluated using the potent locally active mutagen 1-chloromethylpyrene (1-CMP). Contrary to expectations, no UDS response was observed 16 h following 1-CMP dosage by oral gavage. To confirm the integrity of the 1-CMP used for the stomach UDS assay, a sample of the stored chemical was re-evaluated in vitro and shown to be still strongly positive in the Ames assay and to have alkylating activity at least 15 min after incubation at stomach acid pH. No UDS response was observed when test dose levels were reduced or when earlier sampling times were used. Other genotoxic endpoints were examined in stomach. 32P-Postlabelling analysis revealed high levels of adduct formation in gastric DNA. An assay utilizing electrophoresis of DNA (the comet assay) showed the occurrence of DNA damage following dosing with 1-CMP in vivo. These positive results confirmed that 1-CMP should be regarded as a potential in vivo genotoxin. The failure to detect a UDS response to 1-CMP in stomach was investigated; a strong UDS response was observed in an in vitro hepatocyte UDS assay of 1-CMP indicating that the rat was capable of repairing 1-CMP-derived DNA adducts. Pretreatment of rats with hydroxyurea depressed the level of incorporation of thymidine into DNA both in negative and positive [methyl-N-nitrosoguanidine (MNNG)] controls. The results of these studies indicated that the protease digestion method employed did not selectively or efficiently sample those cells with any UDS response to 1-CMP or MNNG, and the activity seen for the latter was most likely due to the presence of S phase cells within the digests. As a result of the finding that UDS responses were not demonstrated for the potent direct-acting mutagens 1-CMP and MNNG, the protease digestion/scintillation method for stomach UDS does not appear to have general value in a screening programme for locally active genotoxic agents.