Background and Aims Biochar has been shown to aid soil fertility and crop production in some circumstances. We investigated effects of the addition of Jarrah (Eucalyptus marginata) biochar to a ...coarse textured soil on soil carbon and nitrogen dynamics. Methods Wheat was grown for 10 weeks, in soil treated with biochar (0, 5, or 25 t ha−1) in full factorial combination with nitrogen (N) treatments (organic N, inorganic N, or control). Samples were analysed for plant biomass, soil microbial biomass carbon (MBC) and nitrogen (MBN), N mineralisation, CO2 evolution, community level physiological profiles (CLPP) and ammonia oxidising bacterial community structure. Results MBC significantly decreased with biochar addition while MBN was unaltered. Net N mineralisation was highest in control soil and significantly decreased with increasing addition of biochar. These findings could not be attributed to sorption of inorganic N to biochar. CO2 evolution decreased with 5 t ha−1 biochar but not 25 t ha−1. Biochar addition at 25 t ha−1 changed the CLPP, while the ammonia oxidising bacterial community structure changed only when biochar was added with a N source. Conclusion We conclude that the activity of the microbial community decreased in the presence of biochar, through decreased soil organic matter decomposition and N mineralisation which may have been caused by the decreased MBC.
A majority of the global net primary production of mangroves is unaccounted for by current carbon budgets. It has been hypothesized that this “missing carbon” is exported as dissolved inorganic ...carbon (DIC) from subsurface respiration and groundwater (or pore-water) exchange driven by tidal pumping. We tested this hypothesis by measuring concentrations and δ
13C values of DIC, dissolved organic carbon (DOC), and particulate organic carbon (POC), along with radon (222Rn, a natural submarine groundwater discharge tracer), in a tidal creek in Moreton Bay, Australia. Concentrations and δ
13C values displayed consistent tidal variations, and mirrored the trend in 222Rn in summer and winter. DIC and DOC were exported from, and POC was imported to, the mangroves during all tidal cycles. The exported DOC had a similar δ13C value in summer and winter (∼ −30‰). The exported δ
13C-DIC showed no difference between summer and winter and had a δ
13C value slightly more enriched (∼ −22.5‰) than the exported DOC. The imported POC had differing values in summer (∼ −16‰) and winter (∼ −22‰), reflecting a combination of seagrass and estuarine particulate organic matter (POM) in summer and most likely a dominance of estuarine POM in winter. A coupled 222Rn and carbon model showed that 93–99% of the DIC and 89–92% of the DOC exports were driven by groundwater advection. DIC export averaged 3 g C m−2 d−1 and was an order of magnitude higher than DOC export, and similar to global estimates of the mangrove missing carbon (i.e., ∼ 1.9–2.7 g C m−2 d−1).
Nitrous oxide (N2O) emissions in semi-arid regions are often greater following summer rainfall events when the soil is fallow, than in response to N fertiliser applications during crop growth. ...Nitrogen fertiliser management strategies are therefore likely to be ineffective at mitigating N2O emissions from these cropped agricultural soils. Here we examined the influence of raising soil pH on N2O emissions, nitrification rates, and both nitrifier and denitrifier populations following simulated summer rainfall events. The soil pH was raised by applying lime to a field site 12 months before conducting the laboratory experiment, resulting in soil of contrasting pH (4.21 or 6.34). Nitrous oxide emissions ranged from 0 when the soil was dry to 0.065 μg N2O–N g dry soil−1 h−1 following soil wetting; which was attributed to both denitrification and nitrification. Increasing soil pH only decreased N2O emissions when losses were associated with nitrification, and increased amoA gene copy numbers. We propose increasing soil pH as a strategy for decreasing soil N2O emissions from acidic soils following summer rainfall in semi-arid regions when emissions result from nitrification.
► We investigated if liming decreased soil N2O emissions following summer rain. ► N2O emissions were attributed to both denitrification and nitrification. ► Raising soil pH decreased N2O emissions from nitrification. ► Raising soil pH increased ammonia oxidising bacteria (AOB) gene copy numbers. ► There was no change in AOA or denitrifier gene copy numbers with soil pH.
We report on measurements of magnetic-field induced nematic order in the bent-core liquid crystal 4-chlororesorcinol bis4-(4-n-dodecyloxybenzoyloxy) benzoate. Using the 31 T solenoid at the National ...High Magnetic Field Laboratory, we have observed, at temperatures less than 1 degrees above the clearing point, a first-order transition to the nematic phase. The critical magnetic field at which this occurs increases with temperature. We discuss these results within the context of both Maier-Saupe and Landau-de Gennes mean-field models for the nematic-isotropic transition. The implications of possible tetrahedratic order are also discussed. To our knowledge, this is the first observation of such a magnetic-field induced transition in a thermotropic liquid crystal; the reasons for which this behavior is now attainable are discussed.
Most studies on plant nutrition tend to focus on the topsoil (plough layer) and frequently neglect subsoil processes. However, cereal roots can potentially acquire nutrients including organic and ...inorganic nitrogen (N) from deep in the soil profile. Greater knowledge on the interaction of plants and microbes in subsoil environments is required to evaluate whether deep rooting traits in cereals will achieve greater nutrient use efficiency and greater soil carbon (C) storage in cropping systems. This study aimed to evaluate the relationship between root distribution, organic and inorganic N availability and potential N supply at the critical growth period during the wheat cropping cycle in a sand textured Eutric Cambisol. Our results provide evidence of significant microbial capacity in the subsoil. The rate of plant residue turnover and the mineralization of organic C and N substrates (glucose, amino acids, peptides, protein) declined slightly with increasing soil depth; however, these rates were not correlated with basal soil respiration, microbial biomass or community structure. This suggests that the microbial population in subsoil is more C limited but that its activity can be readily stimulated upon C substrate addition. A significant potential for organic and inorganic N turnover was also demonstrated at depth with a similar abundance of ammonifiers and ammonia oxidizing bacteria (AOB) and archaea (AOA) throughout the soil profile. Again, N mineralization in subsoils appears to be substrate limited. Root density declined rapidly down the soil profile with few roots present past 50 cm; suggesting that this is the major factor limiting C recharge of soil organic matter and microbial activity in subsoils. Greater root proliferation at depth could allow greater capture of water and the recapture of N lost by leaching; however, our results suggest that plant-microbial competition for C and N is as intense in the subsoil as in the topsoil. We conclude that while deeper rooting may improve nutrient and water use efficiency it may not lead to much greater C sequestration in subsoils, at least in the short term.
•Microbial community composition changes with soil depth.•Subsoil microbial activity increases rapidly on DOC and DON substrate addition.•Microbial activity in subsoils is not nitrogen limited.•Nitrogen mineralization in subsoils is substrate limited.•Greater root proliferation at depth may not lead to greater C sequestration.
Alumina Scale Formation: A New Perspective Heuer, Arthur H.; Hovis, David B.; Smialek, James L. ...
Journal of the American Ceramic Society,
June 2011, Letnik:
94, Številka:
s1
Journal Article
Recenzirano
Oxidation of Al2O3 scale‐forming alloys is of immense technological significance and has been a subject of much scientific inquiry for decades. The oxidation reaction is remarkably complex, involving ...issues of alloy composition, kinetics, thermodynamics, microstructure, mechanics and mechanical properties, crystallography, etc. A brief overview of the formation of passivating, thermally grown oxide Al2O3 scales will be given in the light of recent findings on the defect structure and associated transport behavior of α‐Al2O3. It is inferred that the electronic structure of Al2O3 is of direct relevance to understand the Al2O3 scale growth. We also discuss the effect of the so‐called “reactive” elements (REs)—Y, Zr, and Hf—on reducing the rate of Al2O3 scale thickening by reducing the outward flux of aluminum. An important aspect of the “new perspective” is the suggestion that the REs change the electronic structure of Al2O3—the relevant near‐band‐edge defect (grain boundary) states that are crucial to vacancy creation both at the scale/gas and scale/metal interfaces.
Background EUS can provide access to the main pancreatic duct (MPD) for therapeutic intervention. The long-term clinical success of EUS-guided MPD interventions is unknown. Objective To determine ...technical and clinical success rates, predictors of success, and long-term outcomes of EUS-guided MPD intervention. Design Retrospective, single-center study. Setting Tertiary-care referral center. Patients Forty-five patients. Intervention EUS-guided MPD stent retrieval or placement. Main Outcome Measurements Technical and clinical success rates, adverse events, and long-term clinical outcomes. Results Among the 45 patients, 37 had undergone failed ERCP, and 29 had surgically altered anatomy. Median follow-up after initial EUS-guided intervention was 23 months. Two patients underwent EUS for stent removal, and EUS-guided MPD stent placement was attempted in 43 patients. Technical success was achieved in 32 of 43 patients (74%) with antegrade (n = 18) or retrograde (n = 14) stent insertion. Serious adverse events occurred in 3 patients (6%). Patients underwent a median of 2 (range 1-6) follow-up procedures for revision or removal of stents, without adverse events. Complete symptom resolution occurred in 24 of 29 patients (83%) while stents were in place, including all 6 with nondilated ducts. Stents were removed in 23 patients, who were then followed for an additional median of 32 months; 4 patients had recurrent symptoms. Among the 11 failed cases, most had persistent symptoms or required surgery. Limitations Retrospective study design, individualized patient management. Conclusion EUS-guided MPD intervention is feasible and safe, with long-term clinical success in the majority of patients. EUS provides important treatment options, particularly in patients who would otherwise undergo surgery.
Background Pancreaticoduodenectomy needs simple, validated risk models to better identify 30-day mortality. The goal of this study is to develop a simple risk score to predict 30-day mortality after ...pancreaticoduodenectomy. Methods We reviewed cases of pancreaticoduodenectomy from 2005–2012 in the American College of Surgeons-National Surgical Quality Improvement Program databases. Logistic regression was used to identify preoperative risk factors for morbidity and mortality from a development cohort. Scores were created using weighted beta coefficients, and predictive accuracy was assessed on the validation cohort using receiver operator characteristic curves and measuring area under the curve. Results The 30-day mortality rate was 2.7% for patients who underwent pancreaticoduodenectomy ( n = 14,993). We identified 8 independent risk factors. The score created from weighted beta coefficients had an area under the curve of 0.71 (95% confidence interval, 0.66–0.77) on the validation cohort. Using the score WH ipple- ABACUS (hypertension W ith medication + H istory of cardiac surgery + A ge >62 + 2 × B leeding disorder + A lbumin <3.5 g/dL + 2 × disseminated C ancer + 2 × U se of steroids + 2 × S ystemic inflammatory response syndrome), mortality rates increase with increasing score ( P < .001). Conclusion While other risk scores exist for 30-day mortality after pancreaticoduodenectomy, we present a simple, validated score developed using exclusively preoperative predictors surgeons could use to identify patients at risk for this procedure.
Background and Aims Among the greatest hurdles to pancreatic cancer (PC) therapy is the limited tissue penetration of systemic chemotherapy because of tumor desmoplasia. The primary study aim was to ...determine the toxicity profile of EUS-guided fine-needle injection (EUS-FNI) with gemcitabine. Secondary endpoints included the ability to disease downstage leading to an R0 resection and overall survival (OS) at 6 months, 12 months, and 5 years after therapy. Methods In a prospective study from a tertiary referral center, gemcitabine (38 mg/mL) EUS-FNI was performed in patients with PC before conventional therapy. Initial and delayed adverse events (AEs) were assessed within 72 hours and 4 to 14 days after EUS-FNI, respectively. Patients were followed for ≥5 years or until death. Results Thirty-six patients with stage II (n = 3), stage III (n = 20), or stage IV (n = 13) disease underwent gemcitabine EUS-FNI with 2.5 mL (.7-7.0 mg) total volume of injectate per patient. There were no initial or delayed AEs reported. Thirty-five patients (97.2%) were deceased at the time of analysis with a median 10.3 months of follow-up (range, 3.1-63.9). OS at 6 months and 12 months was 78% and 44%, respectively. The median OS was 10.4 months (range, 2.7-68). Among patients with stage III unresectable disease, 4 (20%) were downstaged and underwent an R0 resection. Conclusions Our study suggests the feasibility, safety, and potential efficacy of gemcitabine EUS-FNI for PC. Additional data are needed to verify these observations and to determine the potential role relative to conventional multimodality therapy.
The effects of exercise on the immune system has been shown to be dependent on the level of fitness of the subjects, the degree of intensity, and the duration of the exercise. A reduction in salivary ...IgA levels occurs after individual sessions of exercise.
The purpose of this study was to assess the relationship between changes in salivary IgA and training volume, psychological stress, and infection rates in a cohort of 26 elite swimmers over a 7-month training period and to compare the changes with a group of 12 moderately exercising controls.
Salivary IgA concentrations were measured by an electroimmunodiffusion. Exercise gradings were assessed by a standardized aerobic-anaerobic rating system. Psychological stress/anxiety was evaluated by the Spielberger State-Trait Anxiety Inventory. Infections were physician-verified.
Salivary IgA levels showed an inverse correlation with the number of infections in both elite swimmers and moderately exercising control subjects. The pretraining salivary IgA levels in swimmers were 4.1% lower for each additional month of training and 5.8% lower for each additional infection. The posttraining salivary IgA levels in swimmers were not significantly correlated with infection rates but were 8.5% lower for each additional 1 km swum in a training session and 7.0% lower for each additional month of training. The number of infections observed in the elite swimmers was predicted from regression models by the preseason (P = 0.05) and the mean pretraining salivary IgA levels (P = 0.006). The trends in pretraining salivary IgA levels over the 7-month season, calculated as individual slopes of pretraining IgA levels over time, were also predictive of the number of infections (P = 0.03) in the swimmers.
These results indicate that measurement of salivary IgA levels over a training season may be predictive for athletes at risk of infection.
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