Total Ankle Replacement Versus Arthrodesis for End-Stage Ankle Osteoarthritis: A Randomized Controlled Trial.

BACKGROUND: End-stage ankle osteoarthritis causes severe pain and disability. There are no randomized trials comparing the 2 main surgical treatments: total ankle replacement (TAR) and ankle fusion (AF). OBJECTIVE: To determine which treatment is superior in terms of clinical scores and adverse events. DESIGN: A multicenter, parallel-group, open-label randomized trial. (ISRCTN registry number: 60672307). SETTING: 17 National Health Service trusts across the United Kingdom. PATIENTS: Patients with end-stage ankle osteoarthritis, aged 50 to 85 years, and suitable for either procedure. INTERVENTION: Patients were randomly assigned to TAR or AF surgical treatment. MEASUREMENTS: The primary outcome was change in Manchester-Oxford Foot Questionnaire walking/standing (MOXFQ-W/S) domain scores between baseline and 52 weeks after surgery. No blinding was possible. RESULTS: Between 6 March 2015 and 10 January 2019, a total of 303 patients were randomly assigned; mean age was 68 years, and 71% were men. Twenty-one patients withdrew before surgery, and 281 clinical scores were analyzed. At 52 weeks, the mean MOXFQ-W/S scores improved for both groups. The adjusted difference in the change in MOXFQ-W/S scores from baseline was -5.6 (95% CI, -12.5 to 1.4), showing that TAR improved more than AF, but the difference was not considered clinically or statistically significant. The number of adverse events was similar between groups (109 vs. 104), but there were more wound healing issues in the TAR group and more thromboembolic events and nonunion in the AF group. The symptomatic nonunion rate for AF was 7%. A post hoc analysis suggested superiority of fixed-bearing TAR over AF (-11.1 [CI, -19.3 to -2.9]). LIMITATION: Only 52-week data; pragmatic design creates heterogeneity of implants and surgical techniques. CONCLUSION: Both TAR and AF improve MOXFQ-W/S and had similar clinical scores and number of harms. Total ankle replacement had greater wound healing complications and nerve injuries, whereas AF had greater thromboembolism and nonunion, with a symptomatic nonunion rate of 7%. PRIMARY FUNDING SOURCE: National Institute for Health and Care Research Heath Technology Assessment Programme.

Electrodes Donate Electrons for Nitrate Reduction in a Soil Matrix via DNRA and Denitrification.

Microbial strains and indigenous microbiota in soil slurries have been reported to use electrons from electrodes for nitrate (NO3-) reduction. However, few studies have confirmed this in a soil matrix hitherto. This study investigated if, and how, an electric potential affected NO3- reduction in a soil matrix. The results showed that, compared to a control treatment, applying an electric potential of -0.5 V versus the standard hydrogen electrode (SHE) significantly increased the relative abundance of NO3--reducing microbes (e.g., Alcaligenaceae and Pseudomonadaceae) and the abundances of the nrfA, nirK, nirS, and nosZ genes in soil matrices. Meanwhile, the electric potential treatment doubled the NO3- reduction rate and significantly increased the rates of production of ammonium (NH4+), dinitrogen (N2), and nitrous oxide (N2O). The amount of NO3--N reduced under the electric potential treatment was comparable to the sum of the amounts of N observed in the increased N2O, N2, NH4+, and nitrite (NO2-) pools. An open-air experiment showed that the electric potential treatment promoted soil NO3- reduction with a spatial scale of at least 38 cm. These results demonstrated that an electric potential treatment could enhance NO3- reduction via both denitrification and dissimilatory NO3- reduction to ammonium (DNRA) in the soil matrix. The mechanisms revealed in this study have implications for the future development of potential techniques for enhancing NO3- reduction in the vadose zone and consequently reducing the risk of NO3- leaching.

Explaining the doubling of N2 O emissions under elevated CO2 in the Giessen FACE via in-field 15 N tracing.

Rising atmospheric CO2 concentrations are expected to increase nitrous oxide (N2 O) emissions from soils via changes in microbial nitrogen (N) transformations. Several studies have shown that N2 O emission increases under elevated atmospheric CO2 (eCO2 ), but the underlying processes are not yet fully understood. Here, we present results showing changes in soil N transformation dynamics from the Giessen Free Air CO2 Enrichment (GiFACE): a permanent grassland that has been exposed to eCO2 , +20% relative to ambient concentrations (aCO2 ), for 15 years. We applied in the field an ammonium-nitrate fertilizer solution, in which either ammonium ( NH4+ ) or nitrate ( NO3- ) was labelled with 15 N. The simultaneous gross N transformation rates were analysed with a 15 N tracing model and a solver method. The results confirmed that after 15 years of eCO2 the N2 O emissions under eCO2 were still more than twofold higher than under aCO2 . The tracing model results indicated that plant uptake of NH4+ did not differ between treatments, but uptake of NO3- was significantly reduced under eCO2 . However, the NH4+ and NO3- availability increased slightly under eCO2 . The N2 O isotopic signature indicated that under eCO2 the sources of the additional emissions, 8,407 µg N2 O-N/m2 during the first 58 days after labelling, were associated with NO3- reduction (+2.0%), NH4+ oxidation (+11.1%) and organic N oxidation (+86.9%). We presume that increased plant growth and root exudation under eCO2 provided an additional source of bioavailable supply of energy that triggered as a priming effect the stimulation of microbial soil organic matter (SOM) mineralization and fostered the activity of the bacterial nitrite reductase. The resulting increase in incomplete denitrification and therefore an increased N2 O:N2 emission ratio, explains the doubling of N2 O emissions. If this occurs over a wide area of grasslands in the future, this positive feedback reaction may significantly accelerate climate change.

Nitrous Oxide Fluxes, Soil Oxygen, and Denitrification Potential of Urine- and Non-Urine-Treated Soil under Different Irrigation Frequencies.

Despite increased use of irrigation to improve forage quality and quantity for grazing cattle ( Linnaeus), there is a lack of data that assess how irrigation practices influence nitrous oxide (NO) emissions from urine-affected soils. Irrigation effects on soil oxygen (O) availability, a primary controller of NO fluxes, is poorly understood. It was hypothesized that increased irrigation frequency would result in lower NO emissions by increasing soil moisture and decreasing soil O concentrations. This would favor more NO reduction to dinitrogen (N). We examined effects of high (3-d) versus low (6-d) irrigation frequency with and without bovine urine addition to pasture. Nitrous oxide fluxes were measured daily for 35 d. Soil O, temperature, and water content were continuously measured at multiple depths. Inorganic nitrogen, organic carbon, and soil pH were measured at 6-d intervals. Measurements of denitrification enzyme activity with and without acetylene inhibition were used to infer the NO/(NO + N) ratio. The NO/(NO + N) ratio was lower under high- compared with low-frequency irrigation, suggesting greater potential for NO reduction to N with more frequent irrigation. Although NO fluxes were increased by urine addition, they were not affected by irrigation frequency. Soil O decreased temporarily after urine deposition, but O dynamics did not explain NO dynamics. Relative soil gas diffusivity (/) was a better predictor of NO fluxes than O concentration. On a free-draining soil, increasing irrigation frequency while providing the same total water volume did not enhance NO emissions under ruminant urine patches in a grazed pasture.

Nitrous oxide and methane emissions from cryptogamic covers.

Cryptogamic covers, which comprise some of the oldest forms of terrestrial life on Earth (Lenton & Huntingford, ), have recently been found to fix large amounts of nitrogen and carbon dioxide from the atmosphere (Elbert et al., ). Here we show that they are also greenhouse gas sources with large nitrous oxide (N2 O) and small methane (CH4 ) emissions. Whilst N2 O emission rates varied with temperature, humidity, and N deposition, an almost constant ratio with respect to respiratory CO2 emissions was observed for numerous lichens and bryophytes. We employed this ratio together with respiration data to calculate global and regional N2 O emissions. If our laboratory measurements are typical for lichens and bryophytes living on ground and plant surfaces and scaled on a global basis, we estimate a N2 O source strength of 0.32-0.59 Tg year(-1) for the global N2 O emissions from cryptogamic covers. Thus, our emission estimate might account for 4-9% of the global N2 O budget from natural terrestrial sources. In a wide range of arid and forested regions, cryptogamic covers appear to be the dominant source of N2 O. We suggest that greenhouse gas emissions associated with this source might increase in the course of global change due to higher temperatures and enhanced nitrogen deposition.

Are albumin and total lymphocyte count significant and reliable predictors of mortality in fractured neck of femur patients?

Hip fractures are a significant cause of mortality and morbidity in the elderly. It is important to identify factors that predict an increased mortality following hip fracture. The aim of this study was to identify significant predictors of mortality at 6 and 12 months following hip fractures. Three hundred patients above the age of 65 were identified who were admitted in to the hospital with fracture neck of femur. Two hundred and seventy-four patients were operated and were included into the study. Variables collected were age, gender, significant comorbidities, admission albumin level and admission total lymphocyte count (TLC). Admission time and subsequent time to surgery were also analysed. Our study showed that albumin and TLC were found to be the only clearly significant mortality predictors at 12 months and a delay of up to 4 days to surgery does not significantly increase the mortality at 12 months.

Nitrous oxide emissions from in situ deposition of N-labeled ryegrass litter in a pasture soil.

During pasture grazing, freshly harvested herbage (litterfall) is dropped onto soils from the mouths of dairy cattle, potentially inducing nitrous oxide (NO) emissions. Although the Intergovernmental Panel on Climate Change (IPCC) recommends accounting for NO emissions from arable crop residues in national inventories, emissions from the litterfall of grazed pasture systems are not recognized. The objective of this study was to investigate the potential of litterfall to contribute to NO emissions in a field study located on a pasture site in Canterbury, New Zealand (43°38.50' S, 172°27.17' E). We applied N-labeled perennial ryegrass ( L.) to the surface of a pastoral soil (Temuka clay loam) and, for up to 139 d thereafter, quantified the contribution of herbage decomposition to NO production and soil N dynamics. Litterfall contributed to the N enrichment of soil NO-N and NO-N pools. After 49 d, N recovery as NO equated to 0.93% of the surface-applied litter N, with 38 to 75% of the cumulative NO flux occurring within 4 to 10 d of treatment application. Emissions of NO likely resulted from ammonification followed by a coupling of nitrification and denitrification during litter decomposition on the soil surface. The emission factor of the litter deposited in situ was 1.2 ± 0.2%, which is not substantially greater than the IPCC default emission factor value of 1% for crop residues. Further in situ studies using different pasture species and litterfall rates are required to understand the microbial processes responsible for litter-induced NO emissions.

Association of Periprosthetic Fibula Fracture With Knotless Suture Button (TightRope) Fixation for Ankle Syndesmosis in Elite Athletes.

Background: Suture button fixation is frequently used to stabilize the distal tibiofibular syndesmosis in athletes sustaining an isolated ligamentous syndesmosis injury. Purpose: To report on a series of periprosthetic fibula fractures adjacent to the lateral suture button after a subsequent unrelated ankle injury or progressive stress injury after initial ankle syndesmosis stabilization using the knotless TightRope (Arthrex). Study Design: Case series; Level of evidence, 4. Methods: Eight elite athletes with periprosthetic fibula fractures and stress injuries around the lateral suture buttons were evaluated. In all athletes, the knotless TightRope had been used to stabilize an isolated ligamentous ankle syndesmotic injury, after which all patients recovered and returned to professional sports at their preinjury level. The athletes subsequently developed an acute fibula fracture or a fibula stress fracture related to the 3.7-mm drill hole in the fibula adjacent to the lateral suture buttons after a mean of 14.1 months (range, 5-29 months). The management of these complications was analyzed. Results: Five athletes sustained a periprosthetic fibula fracture in the form of undisplaced spiral Weber B injuries after a subsequent, unrelated injury. Poor healing response was noted with initial nonoperative treatment for the first 2 athletes, and surgical intervention was performed with successful union of the fracture and return to sports. The subsequent 3 athletes had early surgery with uneventful recovery. Another 3 athletes developed stress injuries adjacent to the fibula suture button without a history of acute trauma. In 2 of the 3 athletes, the position of lateral suture buttons was in the anterior third of the fibula. Initial nonoperative management yielded poor healing response, and subsequent surgical intervention was required to enable healing and return to sports. Conclusion: Nonoperative management of fractures adjacent to the fibula suture button of a knotless TightRope may lead to a delay in union. Therefore, early surgical intervention should be considered in elite athletes, whose return-to-sports time is critical. Care is needed to ensure that the fibula hole for the suture button is centrally located because the eccentric placement of the fibula hole in the anterior third of the fibula may contribute to the development of a stress reaction or stress fracture. Surgical intervention for a periprosthetic fibula stress fracture leads to satisfactory resolution of symptoms.

Nitrate as an alternative electron acceptor destabilizes the mineral associated organic carbon in moisturized deep soil depths.

Numerous studies have investigated the effects of nitrogen (N) addition on soil organic carbon (SOC) decomposition. However, most studies have focused on the shallow top soils <0.2 m (surface soil), with a few studies also examining the deeper soil depths of 0.5-1.0 m (subsoil). Studies investigating the effects of N addition on SOC decomposition in soil >1.0 m deep (deep soil) are rare. Here, we investigated the effects and the underlying mechanisms of nitrate addition on SOC stability in soil depths deeper than 1.0 m. The results showed that nitrate addition promoted deep soil respiration if the stoichiometric mole ratio of nitrate to O2 exceeded the threshold of 6:1, at which nitrate can be used as an alternative acceptor to O2 for microbial respiration. In addition, the mole ratio of the produced CO2 to N2O was 2.57:1, which is close to the theoretical ratio of 2:1 expected when nitrate is used as an electron acceptor for microbial respiration. These results demonstrated that nitrate, as an alternative acceptor to O2, promoted microbial carbon decomposition in deep soil. Furthermore, our results showed that nitrate addition increased the abundance of SOC decomposers and the expressions of their functional genes, and concurrently decreased MAOC, and the ratio of MAOC/SOC decreased from 20% before incubation to 4% at the end of incubation. Thus, nitrate can destabilize the MAOC in deep soils by stimulating microbial utilization of MAOC. Our results imply a new mechanism on how above-ground anthropogenic N inputs affect MAOC stability in deep soil. Mitigation of nitrate leaching is expected to benefit the conservation of MAOC in deep soil depths.

Two to Five-Year Outcomes of Total Ankle Arthroplasty with the Infinity Fixed-Bearing Implant: A Concise Follow-up of a Previous Report.

LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Intensive cattle grazing affects pasture litter-fall: an unrecognized nitrous oxide source.

The rationale for this study came from observing grazing dairy cattle dropping freshly harvested plant material onto the soil surface, hereafter called litter-fall. The Intergovernmental Panel on Climate Change (IPCC) guidelines include NO emissions during pasture renewal but do not consider NO emissions that may result from litter-fall. The objectives of this study were to determine litter-fall rates and to assess indicative NO emission factors (EFs) for the dominant pasture species (perennial ryegrass [ L.] and white clover [ L.]). Herbage was vacuumed from intensively managed dairy pastures before and after 30 different grazing events when cows (84 cows ha) grazed for 24 h according to a rotational system; the interval between grazing events ranged from 21 to 30 d. A laboratory incubation study was performed to assess potential EF values for the pasture species at two soil moisture contents. Finely ground pasture material was incubated under controlled laboratory conditions with soil, and the NO emissions were measured until rates returned to control levels. On average, pre- and postgrazing dry matter yields per grazing event were 2516 ± 636 and 1167 ± 265 kg DM ha (±SD), respectively. Pregrazing litter was absent, whereas postgrazing fresh and senesced litter-fall rates were 53 ± 24 and 19 ± 18 kg DM ha, respectively. Annually, the rotational grazing system resulted in 12 grazing events where fresh litter-fall equaed to 16 kg N ha yr to the soil. Emission factors in the laboratory experiment indicated that the EF for perennial ryegrass and white clover ranged from 0.7 to 3.1%. If such EF values should also occur under field conditions, then we estimate that litter-fall induces an NO emission rate of 0.3 kg NO ha yr. Litter-fall as a source of NO in grazed pastures requires further assessment.

The long-term outcome of silastic implant arthroplasty of the first metatarsophalangeal joint: a retrospective analysis of one hundred and eight feet.

PURPOSE: The short-term results of silastic implant of the first metatarsophalangeal joint (MTPJ) have been successful. However, reservations exist regarding long-term results. The aim of this study was to evaluate long-term outcome of silastic implant prosthesis in treatment of hallus rigidus. METHODS: This was a retrospective study, with 108 feet in 83 patients, operated upon between 1988 and 2003. Mean age at operation was 55 years (SD 8.1) with a follow-up period of 8.5 years. Outcome measures included the American Orthopaedic Foot and Ankle Scoring system(AOFAS), passive and active arc of motion. Patients' satisfaction was assessed using the visual analogue scale. All the patients had anteroposterior and oblique views and were assessed for loosening and osteolysis. Pedobarographic studies were performed using the Musgrave Footprint. Complications and revisions were recorded. RESULTS: The mean total AOFAS score was 77.5 (SD 13.4). Mean active and passive arc of motions were 36.8 degrees (SD 19.13) and 46.82 degrees (SD 17.19), respectively. Patient satisfaction showed mean VAS of 7.73 (SD 2.41). Prostheses were removed in three feet at three, five and seven years respectively because of persistent pain. Radiologically 25 feet (23 %) had osteolysis but were non progressive and didn't correlate with the functional outcome. CONCLUSION: We can conclude that silastic implant arthroplasty is an effective procedure in hallux rigidus management with satisfactory functional outcome and high patient satisfaction.

Biochar incorporation into pasture soil suppresses in situ nitrous oxide emissions from ruminant urine patches.

Nitrous oxide (N2O) emissions from grazing animal excreta are estimated to be responsible for 1.5 Tg of the total 6.7 Tg of anthropogenic N2O emissions. This study was conducted to determine the in situ effect of incorporating biochar, into soil, on N2O emissions from bovine urine patches and associated pasture uptake of N. The effects of biochar rate (0-30 t ha(-1)), following soil incorporation, were investigated on ruminant urine-derived N2O fluxes, N uptake by pasture, and pasture yield. During an 86-d spring-summer period, where irrigation and rainfall occurred, the N2O fluxes from 15N labeled ruminant urine patches were reduced by >50%, after incorporating 30 t ha(-1) of biochar. Taking into account the N2O emissions from the control plots, 30 t ha(-1) ofbiochar reduced the N2O emission factor from urine by 70%. The atom% 15N enrichment of the N2O emitted was lower in the 30 t ha(-1) biochar treatment, indicating less urine-N contributed to the N2O flux. Soil NO3- -N concentrations were lower with increasing biochar rate during the first 30 d following urine deposition. No differences occurred, due to biochar addition, with respect to dry matter yields, herbage N content, or recovery of 15N applied in herbage. Incorporating biochar into the soil can significantly diminish ruminant urine-derived N2O emissions. Further work is required to determine the persistence of the observed effect and to fully understand the mechanism(s) of the observed reduction in N2O fluxes.

Biochar and the nitrogen cycle: introduction.

Nitrogen (N) is an essential nutrient, and research to date shows that biochar potentially has the ability to manipulate the rates of N cycling in soil systems by influencing nitrification rates and adsorption of ammonia and increasing NH4+ storage by enhancing cation exchange capacity in soils. Its influence on these processes may have further implications in terms of reducing gaseous N losses such as N2O and nitrate leaching. However, further detailed research is required to fully understand the transformation mechanisms and fate of N when associated with biochar treated soils. The three research papers that comprise this special collection of papers on biochar and the nitrogen cycle focus on biochar's diverse ability to influence N cycling processes. These papers show for the first time (i) how microbial nitrification communities and function differ with exposure to biochar, (ii) how the length of time the soil has been in contact with biochar influences N transformation and how this can vary with soil type, and (iii) how composting of organic materials with biochar can reduce N losses and enhance the nutrient status of the composted product. Considerable knowledge gaps still exist in terms of understanding the precise mechanisms through which biochar influences soil N transformations, and how biochar affects both plant and microbial N supply. The general direction that research on biochar should focus on with respect to the N cycle is the effect(s) that biochar has on N transformation in soils, both chemical and biological mechanisms, and the fate of N applied to biochar treated soils. This research needs to be performed at both field plot and microbial scales.

Application methods of tracers for N2O source determination lead to inhomogeneous distribution in field plots.

Source determination of N2O has often been performed using stable isotope incubation experiments. In situ experiments with isotopic tracers are an important next step. However, the challenge is to distribute the tracers in the field as homogeneously as possible. To examine this, a bromide solution was applied as a stand-in tracer using either a watering can, a sprayer, or syringes to a relatively dry (25% gravimetric moisture content) or wet (30%) silt loam. After 1 h, samples were taken from three soil depths (0-10 cm), and analyzed for their water content and bromide concentration. The application with syringes was unsuccessful due to blocked cannulas. Therefore, further laboratory experiments were conducted with side-port cannulas. Despite a larger calculated gravimetric soil moisture difference with watering can application, more Br- tracer was recovered in the sprayer treatment, probably due to faster transport of Br- through macropore flow in the wetter conditions caused by the watering can treatment. The losses of Br- (33% for the watering can, 28% for the sprayer treatment) are equivalent to potential losses of isotopic tracer solutions. For application of 60 at% 15NH4 +, this resulted in theoretical enrichments of 44-53 at% in the upper 2.5 cm and 7-48 at% in 5-10 cm. As there was hardly any NO3 - in the soil, extrapolations for 15NO3 - calculated enrichments were 57-59 at% in the upper 2.5 cm and 26-57 at% in 5-10 cm. Overall, no method, including the side-port cannulas, was able to achieve a homogeneous distribution of the tracer. Future search for optimal tracer application should therefore investigate methods that utilize capillary forces and avoid overhead pressure. We recommend working on rather dry soil when applying tracers, as tracer recovery was larger here. Furthermore, larger amounts of tracer lead to more uniform distributions. Further studies should also investigate the importance of plant surfaces.

Global Research Alliance N2 O chamber methodology guidelines: Introduction, with health and safety considerations.

Non-steady-state (NSS) chamber techniques have been used for decades to measure nitrous oxide (N2 O) fluxes from agricultural soils. These techniques are widely used because they are relatively inexpensive, easy to adopt, versatile, and adaptable to varying conditions. Much of our current understanding of the drivers of N2 O emissions is based on studies using NSS chambers. These chamber techniques require decisions regarding multiple methodological aspects (e.g., chamber materials and geometry, deployment, sample analysis, and data and statistical analysis), each of which may significantly affect the results. Variation in methodological details can lead to challenges in comparing results between studies and assessment of reliability and uncertainty. Therefore, the New Zealand Government, in support of the objectives of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases (GRA), funded two international projects to, first, develop standardized guidelines on the use of NSS chamber techniques and, second, refine them based on the most up to date knowledge and methods. This introductory paper summarizes a collection of papers that represent the revised guidelines. Each article summarizes existing knowledge and provides guidance and minimum requirements on chamber design, deployment, sample collection, storage and analysis, automated chambers, flux calculations, statistical analysis, emission factor estimation and data reporting, modeling, and "gap-filling" approaches. The minimum requirements are not meant to be highly prescriptive but instead provide researchers with clear direction on best practices and factors that need to be considered. Health and safety considerations of NSS chamber techniques are also provided with this introductory paper.

Dissolved organic nitrogen: an overlooked pathway of nitrogen loss from agricultural systems?

Conventional wisdom postulates that leaching losses of N from agriculture systems are dominated by NO(3)(-). Although the export of dissolved organic nitrogen (DON) into the groundwater has been recognized for more than 100 yr, it is often ignored when total N budgets are constructed. Leaching of DON into stream and drinking water reservoirs leads to eutrophication and acidification, and can pose a potential risk to human health. The main objective of this review was to determine whether DON losses from agricultural systems are significant, and to what extent they pose a risk to human health and the environment. Dissolved organic N losses across agricultural systems varied widely with minimum losses of 0.3 kg DON ha(-1)yr(-1) in a pasture to a maximum loss of 127 kg DON ha(-1)yr(-1) in a grassland following the application of urine. The mean and median values for DON leaching losses were found to be 12.7 and 4.0 kg N ha(-1)yr(-1), respectively. On average, DON losses accounted for 26% of the total soluble N (NO(3)(-) plus DON) losses, with a median value of 19%. With a few exceptions, DON concentrations exceeded the criteria recommendations for drinking water quality. The extent of DON losses increased with increasing precipitation/irrigation, higher total inputs of N, and increasing sand content. It is concluded that DON leaching can be an important N loss pathway from agricultural systems. Models used to simulate and predict N losses from agricultural systems should include DON losses.

Effects of denitrification and transport on the isotopic composition of nitrate (δ18O, δ15N) in freshwater systems.

Nitrate isotopes (δ15N-NO3- and δ18O-NO3-) are a potentially powerful tool for tracking the biological removal of reactive nitrogen (N) as it is transported from land to sea. However, uncertainties about, 1) the variability of the strength of biological isotopic fractionation during anaerobic benthic NO3- reduction (the kinetic enrichment factor: εdenit), and, 2) how accurately these εdenit values are expressed in overlying aerobic surface waters (the effective enrichment factor: εeff), currently limit their use in freshwater systems. Here we used a combination of incubation experiments and numerical modelling to construct a simple framework for defining freshwater εdenit based on interactions between benthic denitrification and diffusive transport to surface waters. Under non-limited, anaerobic conditions the εdenit values produced in submerged soils (n = 3) and sediments (n = 4) with denitrification rates between 10 and 600 mg N m-2 d-1 ranged from -3‰ to -28‰. Critically, model results indicated that diffusive transport would homogenise this to an effective fractionation range of -6 ±â€¯4‰. Evidence for biological and hydrological variability of NO3- isotope fractionation means that values measured in aerobic surface water environments are most appropriately evaluated by a range of fractionation values, rather than commonly used single 'site specific' εdenit values.

Turf Toe Injury - Current Concepts and an Updated Review of Literature.

Turf toe injuries can be a disabling if not recognized and treated early. A high index of suspicion, based on the mechanism of injury and appropriate imaging, helps in the timely diagnosis. These injuries are frequently known to occur on artificial playing surfaces, because of the increased traction at the shoe-surface interface. Stress and instability testing are key components to assess the need for surgical intervention. Accurate timely diagnosis and treatment can allow full return to physical activities for most athletes, back to their pre-injury level.

Influence of copper on expression of nirS, norB and nosZ and the transcription and activity of NIR, NOR and N2 OR in the denitrifying soil bacteria Pseudomonas stutzeri.

Reduction of the potent greenhouse gas nitrous oxide (N(2)O) occurs in soil environments by the action of denitrifying bacteria possessing nitrous oxide reductase (N(2)OR), a dimeric copper (Cu)-dependent enzyme producing environmentally benign dinitrogen (N(2)). We examined the effects of increasing Cu concentrations on the transcription and activity of nitrite reductase (NIR), nitric oxide reductase (NOR) and N2 OR in Pseudomonas stutzeri grown anaerobically in solution over a 10-day period. Gas samples were taken on a daily basis and after 6 days, bacterial RNA was recovered to determine the expression of nirS, norB and nosZ encoding NIR, NOR and N(2)OR respectively. Results revealed that 0.05 mM Cu caused maximum conversion of N(2)O to N(2) via bacterial reduction of N(2)O. As soluble Cu generally makes up less than 0.001% of total soil Cu, extrapolation of 0.05 mg l(-l) soluble Cu would require soils to have a total concentration of Cu in the range of, 150-200 µg g(-1) to maximize the proportion of N(2)O reduced to N(2). Given that many intensively farmed agricultural soils are deficient in Cu in terms of plant nutrition, providing a sufficient concentration of biologically accessible Cu could provide a potentially useful microbial-based strategy of reducing agricultural N(2)O emissions.