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1.
Edith Fleischmann Corinna Marschalek Katja Schlemitz Jarrod E Dalton Thomas Gruenberger Friedrich Herbst Andrea Kurz Daniel I Sessler 《BMC anesthesiology》2009,9(1):1-9
Background
Even the best cancer surgery is usually associated with minimal residual disease. Whether these remaining malignant cells develop into clinical recurrence is at least partially determined by adequacy of host defense, especially natural killer cell function. Anesthetics impair immune defenses to varying degrees, but nitrous oxide appears to be especially problematic. We therefore tested the hypothesis that colorectal-cancer recurrence risk is augmented by nitrous oxide administration during colorectal surgery.Methods
We conducted a 4- to 8-year follow-up of 204 patients with colorectal cancer who were randomly assigned to 65% nitrous oxide (n = 97) or nitrogen (n = 107), balanced with isoflurane and remifentanil. The primary outcome was the time to cancer recurrence. Our primary analysis was a multivariable Cox-proportional-hazards regression model that included relevant baseline variables. In addition to treatment group, the model considered patient age, tumor grade, dissemination, adjacent organ invasion, vessel invasion, and the number of nodes involved. The study had 80% power to detect a 56% or greater reduction in recurrence rates (i.e., hazard ratio of 0.44 or less) at the 0.05 significance level.Results
After adjusting for significant baseline covariables, risk of recurrence did not differ significantly for nitrous oxide and nitrogen, with a hazard ratio estimate (95% CI) of 1.10 (0.66, 1.83), P = 0.72. No two-way interactions with the treatment were statistically significant.Conclusion
Colorectal-cancer recurrence risks were not greatly different in patients who were randomly assigned to 65% nitrous oxide or nitrogen during surgery. Our results may not support avoiding nitrous oxide use to prevent recurrence of colorectal cancer.Implications Statement
The risk of colorectal cancer recurrence was similar in patients who were randomly assigned to 65% nitrous oxide or nitrogen during colorectal surgery.Trial Registration
Current Controlled Clinical Trials NCT00781352 http://www.clinicaltrials.gov 相似文献2.
Background
Leiomyomas are benign tumours that originate from smooth muscles. They are often seen in the uterus, but also in the renal pelvis, bladder, spermatic cord, epididymis, prostate, scrotum or the glans penis. Leiomyomas of the tunica albuginea are extremely rare.Case presentation
A 59-year-old white male has noted an asymptomatic tumour on the right side of his scrotal sac for several years. This tumour has increased slowly and caused local scrotal pain. An inguinal incision was performed, in which the hypoplastic testis, the epididymis and the tumour could be easily mobilized. Macroscopically the tumour showed a solid round nonencapsulated whorling cut surface. Histologically the diagnosis of a leiomyoma was made.Conclusion
We report here a very interesting and rare case of a leiomyoma of the tunica albuginea. Leiomyomas can be a possible differential diagnosis in this area.Virtual Slides
http://www.diagnosticpathology.diagnomx.eu/vs/2585095378537599 相似文献3.
Karl Z Lukic Bruce Urch Michael Fila Marie E Faughnan Frances Silverman 《Biomedical engineering online》2006,5(1):1-11
Background
A detailed contrast bolus propagation model is essential for optimizing bolus-chasing Computed Tomography Angiography (CTA). Bolus characteristics were studied using bolus-timing datasets from Magnetic Resonance Angiography (MRA) for adaptive controller design and validation.Methods
MRA bolus-timing datasets of the aorta in thirty patients were analyzed by a program developed with MATLAB. Bolus characteristics, such as peak position, dispersion and bolus velocity, were studied. The bolus profile was fit to a convolution function, which would serve as a mathematical model of bolus propagation in future controller design.Results
The maximum speed of the bolus in the aorta ranged from 5–13 cm/s and the dwell time ranged from 7–13 seconds. Bolus characteristics were well described by the proposed propagation model, which included the exact functional relationships between the parameters and aortic location.Conclusion
The convolution function describes bolus dynamics reasonably well and could be used to implement the adaptive controller design. 相似文献4.
Harry JGM Crijns Lori D Bash Fran?ois Chazelle Jean-Yves Le Heuzey Thorsten Lewalter Gregory YH Lip Aldo P Maggioni Alfonso Martín Piotr Ponikowski M?rten Rosenqvist Prashanthan Sanders Mauricio Scanavacca Alexandra A Bernhardt Sreevalsa Unniachan Hemant M Phatak Anselm K Gitt 《BMC cardiovascular disorders》2012,12(1):1-13
Background
Cigarette exposure increases brain oxidative stress. The literature showed that increased brain oxidative stress affects cardiovascular regulation. However, no previous study investigated the involvement of brain oxidative stress in animals exposed to cigarette and its relationship with cardiovascular regulation. We aimed to evaluate the effects of central catalase inhibition on baroreflex and cardiovascular responses in rats exposed to sidestream cigarette smoke (SSCS).Methods
We evaluated males Wistar rats (320-370 g), which were implanted with a stainless steel guide cannula into the fourth cerebral ventricle (4th V). Femoral artery and vein were cannulated for mean arterial pressure (MAP) and heart rate (HR) measurement and drug infusion, respectively. Rats were exposed to SSCS during three weeks, 180 minutes, 5 days/week (CO: 100-300 ppm). Baroreflex was tested with a pressor dose of phenylephrine (PHE, 8 ??g/kg, bolus) to induce bradycardic reflex and a depressor dose of sodium nitroprusside (SNP, 50 ??g/kg, bolus) to induce tachycardic reflex. Cardiovascular responses were evaluated before, 5, 15, 30 and 60 minutes after 3-amino-1,2,4-triazole (ATZ, catalase inhibitor, 0.001 g/100 ??L) injection into the 4th V.Results
Central catalase inhibition increased basal HR in the control group during the first 5 minutes. SSCS exposure increased basal HR and attenuated bradycardic peak during the first 15 minutes.Conclusion
We suggest that SSCS exposure affects cardiovascular regulation through its influence on catalase activity. 相似文献5.
Estimating the impact of changing fertilizer application rate, land use, and climate on nitrous oxide emissions in Irish grasslands 总被引:1,自引:0,他引:1
Dong-Gill Kim Rashad Rafique Paul Leahy Mark Cochrane Gerard Kiely 《Plant and Soil》2014,374(1-2):55-71
Aim
This study examines the impact of changing nitrogen (N) fertilizer application rates, land use and climate on N fertilizer-derived direct nitrous oxide (N2O) emissions in Irish grasslands.Methods
A set of N fertilizer application rates, land use and climate change scenarios were developed for the baseline year 2000 and then for the years 2020 and 2050. Direct N2O emissions under the different scenarios were estimated using three different types of emission factors and a newly developed Irish grassland N2O emissions empirical model.Results
There were large differences in the predicted N2O emissions between the methodologies, however, all methods predicted that the overall N2O emissions from Irish grasslands would decrease by 2050 (by 40–60 %) relative to the year 2000. Reduced N fertilizer application rate and land-use changes resulted in decreases of 19–34 % and 11–60 % in N2O emission respectively, while climate change led to an increase of 5–80 % in N2O emission by 2050.Conclusions
It was observed in the study that a reduction in N fertilizer and a reduction in the land used for agriculture could mitigate emissions of N2O, however, future changes in climate may be responsible for increases in emissions causing the positive feedback of climate on emissions of N2O. 相似文献6.
Background
The aim of this study was to provide a model-based analysis of the pharmacokinetics of remifentanil in infants and children undergoing cardiac surgery with cardiopulmonary bypass (CPB).Methods
We studied nine patients aged 0.5 to 4 years who received a continuous remifentanil infusion via a computer-controlled infusion pump during cardiac surgery with mildly hypothermic CPB were studied. Arterial blood samples taken prior to, during and after CPB were analyzed for remifentanil concentrations using a validated gas-chromatographic mass-spectrophotometric assay. We used population mixed-effects modeling to characterize remifentanil pharmacokinetics. The final model was evaluated by its predictive performance.Results
The pharmacokinetics of remifentanil was described by a 1-compartment model with adjustments for CPB. Population mean parameter estimates were 1.41 L for volume of distribution (V) and 0.244 L/min for clearance. V was increased during CPB and post-CPB to 2.41 times the pre-CPB value. The median prediction error and the median of individual median absolute prediction error were 2.44% and 21.6%, respectively.Conclusion
Remifentanil dosage adjustments are required during and after CPB due to marked changes in the V of the drug. Simulations indicate that a targeted blood concentration of 14 ng/mL is achieved and maintained in 50% of typical patients by administration of an initial dose of 18 μg remifentanil followed by an infusion of 3.7 μg/min before, during and post-CPB, supplemented with a bolus dose of 25 μg given at the start of CPB. 相似文献7.
Valérie Collado Emmanuel Nicolas Denise Faulks Corinne Tardieu Marie-Cécile Manière Dominique Droz Peter Onody Martine Hennequin 《BMC clinical pharmacology》2008,8(1):1-7
Background
Conscious sedation is used in dentistry to improve access and quality of care in patients who have difficulty coping with treatment. The aim of this prospective study was to describe a postgraduate training course in conscious sedation for dentists, with specific evaluation of the safe and effective administration of a 50% nitrous oxide in oxygen premix.Methods
45 practitioners were trained between 2002 and 2004. They carried out 826 sessions of inhalation sedation in 662 patients. The clinical competency of this group was compared with an expert group.Results
There was no difference between trainees and experts in ability to complete the planned dental treatment under sedation (89.6% vs 93.2%). Trainees were less successful than experts for patients with intellectual disability (87.4% vs 94.2%, p < 0.01). For both groups, the degree of cooperation improved between initial induction and each perioperative step (Wilcoxon test, p < 0.01). However, for trainees, Venham behaviour scores varied with the type of patient (Kruskal Wallis test, p < 0.001). No major adverse effects were recorded. Trainees reported more minor adverse effects than experts (13% vs. 5.3% respectively, Fisher exact test, p < 0.001)Conclusion
The trainee practitioners provided effective and safe inhalation sedation. This challenges the current French restriction of the 50% nitrous oxide in oxygen premix to the hospital setting. Further emphasis is required on the teaching of behaviour management skills for patients with intellectual disability. 相似文献8.
Background
Nitrous oxide (N2O) provides sedation for procedures that result in constant low-intensity pain. How long do individuals remain sleepy after receiving N2O? We hypothesized that drug effects would be apparent for an hour or more.Methods
This was a randomized, double blind controlled study. On three separate occasions, volunteers (N = 12) received 100% oxygen or 20% or 40% N2O for 30 min. Dependent measures included the multiple sleep latency test (MSLT), a Drug Effects/Liking questionnaire, visual analogue scales, and five psychomotor tests. Repeated measures analysis of variance was performed with drug and time as factors.Results
During inhalation, drug effects were apparent based on the questionnaire, visual analogue scales, and psychomotor tests. Three hours after inhaling 100% oxygen or 20% N2O, subjects were sleepier than if they breathed 40% N2O. No other drug effects were apparent 1 hour after inhalation ceased. Patients did not demonstrate increased sleepiness after N2O inhalation.Conclusion
We found no evidence for increased sleepiness greater than 1 hour after N2O inhalation. Our study suggests that long-term effects of N2O are not significant. 相似文献9.
Xiao-feng Zhang De-yuan Li Jing-xiang Wu Qi-liang Jiang Hong-wei Zhu Mei-ying Xu 《BMC anesthesiology》2018,18(1):195
Background
Laparoscopic surgery typically requires deep neuromuscular blockade (NMB), but whether deep or moderate NMB is superior for thoracoscopic surgery remains controversial.Methods
Patients scheduled for thoracoscopic lobectomy under intravenous anesthesia were randomly assigned to receive moderate [train of four (TOF) 1–2] or deep NMB [TOF 0, post-tetanic count (PTC) 1–5]. Depth of anesthesia was controlled at a Narcotrend rating of 30?±?5 in both groups. The primary outcome was the need to use an additional muscle relaxant (cisatracurium) during surgery. Secondary outcomes included surgeon satisfaction, recovery time of each stage after drug withdrawal [time from withdrawal until TOF recovery to 20% (antagonists administration), 25, 75, 90, 100%], blood gas data, VAS pain grade after extubation, the time it takes for patients to begin walking after surgery, postoperative complications and hospitalization time. Results were analyzed on an intention-to-treat basis.Results
Thirty patients were enrolled per arm, and all but one patient in each arm was included in the final analysis. Among patients undergoing moderate NMB, surgeons applied additional cisatracurium in 8 patients because of body movement and 5 because of coughing (13/29, 44.8%). Additional cisatracurium was not applied to any of the patients undergoing deep NMB (p?<?0.001). Surgeons reported significantly higher satisfaction for patients undergoing deep NMB (p?<?0.001, Wilcoxon rank sum test). The mean difference between the two groups in the time from withdrawal until TOF recovery of 25% or 90% was 10?min (p?<?0.001). The two groups were similar in other recovery data, blood gas analysis, VAS pain grade, days for beginning to walk and mean hospitalization time.Conclusions
Deep NMB can reduce the use of additional muscle relaxant and increase surgeon satisfaction during thoracoscopic lobectomy.Trial registration
Chinese Clinical Trial Registry, ChiCTR-IOR-15007117, 22 September 2015.10.
Key message
NO generation is studied in the protoplast chloroplasts. NO, ONOO ? and ROS (O 2 ? and H 2 O 2 ) are generated in chloroplasts. Nitric oxide synthase-like protein appears to be involved in NO generation.Abstract
Nitric oxide stimulates chlorophyll biosynthesis and chloroplast differentiation. The present study was conducted to better understand the process of NO generation in the leaf chloroplasts and protoplasts. NO, peroxynitrite and superoxide anion were investigated in the protoplasts and isolated chloroplasts using specific dyes, confocal laser scanning and light microscopy. The level of NO was highest after protoplast isolation and subsequently decreased during culture. Suppression of NO signal in the presence of PTIO, suggests that diaminofluorescein-2 diacetate (DAF-2DA) detected NO. Detection of peroxynitrite, a reaction product of NO and superoxide anion, further suggests NO generation. Moreover, generation of NO and peroxynitrite in the chloroplasts of wild-type Arabidopsis and their absence or weak signals in the leaf-derived protoplasts of Atnoa1 mutants confirmed the reactivity of DAF-2DA and aminophenyl fluorescein to NO and peroxynitrite, respectively. Isolated chloroplasts also showed signal of NO. Suppression of NO signal in the presence of 100 μM nitric oxide synthase inhibitors [l-NNA, Nω-nitro-l-arginine and PBIT, S,S′-1,3-phenylene-bis(1,2-ethanediyl)-bis-isothiourea] revealed that nitric oxide synthase-like system is involved in NO synthesis. Suppression of NO signal in the protoplasts isolated in the presence of cycloheximide suggests de novo synthesis of NO generating protein during the process of protoplast isolation. Furthermore, the lack of inhibition of NO production by sodium tungstate (250 μM) and inhibition by l-NNA, and PBIT suggest involvement NOS-like protein, but not nitrate reductase, in NO generation in the leaf chloroplasts and protoplasts. 相似文献11.
Daniel Kretzschmar Christian Jung Sylvia Otto Stephan Utschig Michael Hartmann Thomas Lehmann Atilla Yilmaz Tudor C P?rner Hans R Figulla Markus Ferrari 《Cardiovascular ultrasound》2012,10(1):1-5
Background
Embolization of atherosclerotic debris from the rupture of a vulnerable atherosclerotic plaque occurs iatrogenically during percutaneous coronary interventions (PCI) and can induce myocardial necrosis. These microembolizations are detected as high intensity transient signals (HITS) using intracoronary Doppler technology.Presentation of the hypothesis
In the presented study we will test if abciximab (ReoPro?) infusion reduces high intensity transient signals in patients with stable angina pectoris undergoing PCI in comparison to standard therapy alone.Testing the hypothesis
The High Intensity Transient Signals ReoPro? (HITS-RP) study will enroll 60 patients. It is a prospective, single center, randomized, double-blinded, controlled trial. The study is designed to compare the efficacy of intravenous abciximab administration for reduction of microembolization during elective PCI. Patients will be randomized in a 1:1 fashion to abciximab or placebo infusion. The primary end point of the HITS-RP-Study is the number of HITS during PCI measured by intracoronary Doppler wire. Secondary endpoints are bleeding complications, elevation of cardiac biomarkers or ECG changes after percutaneous coronary interventions, changes in coronary flow velocity reserve, hs-CRP elevation, any major adverse cardio-vascular event during one month follow-up.Implications of the hypothesis
The HITS-RP-Study addresses important questions regarding the efficacy of intravenous abciximab administration in reducing microembolization and periprocedural complications in stable angina pectoris patients undergoing PCI.Trial registration
The trial is registered under http://www.drks-neu.uniklinik-freiburg.de/drks_web/:DRKS00000603. 相似文献12.
Shin-nosuke Hashida Masahumi Johkan Kazuyoshi Kitazaki Kazuhiro Shoji Fumiyuki Goto Toshihiro Yoshihara 《Plant and Soil》2014,374(1-2):715-725
Aims
Nitrous oxide (N2O) is a strong greenhouse effective gas (GHG); the primary human source of N2O is agricultural activities. Excessive nitrogen (N) fertilization of agricultural land is now widely recognized as a major contributor. In soil, the microbial processes of nitrification and denitrification are the principal sources of N2O. However, it remains poorly understood how conventional hydroponics influences GHG emission. Here, we compared GHG fluxes from soil and rockwool used for hydroponics under identical nutrient conditions.Methods
Tomato plants (Solanum lycopersicum, momotaro) were grown in soil or by hydroponics using rockwool. In situ emissions of CH4, CO2, and N2O, and the abundance of genes involved in nitrification and denitrification were measured during cultivation.Results
Hydroponics with rockwool mitigated CO2 emission by decreasing the microbial quantity in the rhizosphere. Dilution of the nutrient solution significantly decreased N2O emission from rockwool. Although proliferation of nitrifiers or denitrifiers in the rhizosphere did not induce N2O emission, reuse or long-term use of rockwool induced a 3.8-fold increase in N2O emission.Conclusions
Our data suggest that hydroponics has a lower environmental impact and that adequate fertilizer application, rather than bacterial control, governs N2O fluxes in hydroponic cultivation using rockwool. 相似文献13.
Peter JD Andrews Helen Louise Sinclair Claire G Battison Kees H Polderman Giuseppe Citerio Luciana Mascia Bridget A Harris Gordon D Murray Nino Stocchetti David K Menon Haleema Shakur Daniel De Backer 《Trials》2011,12(1):1-13
Background
Severe malaria remains a major cause of global morbidity and mortality. Despite the use of potent anti-parasitic agents, the mortality rate in severe malaria remains high. Adjunctive therapies that target the underlying pathophysiology of severe malaria may further reduce morbidity and mortality. Endothelial activation plays a central role in the pathogenesis of severe malaria, of which angiopoietin-2 (Ang-2) has recently been shown to function as a key regulator. Nitric oxide (NO) is a major inhibitor of Ang-2 release from endothelium and has been shown to decrease endothelial inflammation and reduce the adhesion of parasitized erythrocytes. Low-flow inhaled nitric oxide (iNO) gas is a US FDA-approved treatment for hypoxic respiratory failure in neonates.Methods/Design
This prospective, parallel arm, randomized, placebo-controlled, blinded clinical trial compares adjunctive continuous inhaled nitric oxide at 80 ppm to placebo (both arms receiving standard anti-malarial therapy), among Ugandan children aged 1-10 years of age with severe malaria. The primary endpoint is the longitudinal change in Ang-2, an objective and quantitative biomarker of malaria severity, which will be analysed using a mixed-effects linear model. Secondary endpoints include mortality, recovery time, parasite clearance and neurocognitive sequelae.Discussion
Noteworthy aspects of this trial design include its efficient sample size supported by a computer simulation study to evaluate statistical power, meticulous attention to complex ethical issues in a cross-cultural setting, and innovative strategies for safety monitoring and blinding to treatment allocation in a resource-constrained setting in sub-Saharan Africa.Trial Registration
ClinicalTrials.gov Identifier: NCT01255215 相似文献14.
Background
Nitrous oxide (N2O), a long-standing anesthetic, is also neurotoxic by interfering with the bioavailability of vitamin B12 if abused. A few case studies have reported the neurological and psychiatric complications of N2O.Case presentation
Here, we reported a patient of N2O induced subacute combined degeneration (SCD) with longitudinally extensive myelopathy with inverted V-sign exhibiting progressive limb paresthesia and unsteady gait.Conclusions
This case raises the awareness of an important mechanism of neural toxicity of N2O, and clinical physicians should be well recognized this in the field of substance-related disorders.15.
Key Message
Efficient induction of unreduced gamete in different crops and its genetic consequences will open new avenues for plant breeding.Abstract
Unreduced gamete formation derived via abnormal meiotic cell division is an important approach to polyploidy breeding. This process is considered the main driving force in spontaneous polyploids formation in nature, but the potential application of these gametes to plant breeding has not been fully exploited. An effective mechanism for their artificial induction is needed to attain greater genetic variation and enable efficient use of unreduced gametes in breeding programs. Different approaches have been employed for 2n-pollen production including interspecific hybridization, manipulation of environmental factors and treatment with nitrous oxide, trifluralin, colchicine, oryzalin and other chemicals. These chemicals can act as a stimulus to produce viable 2n pollen; however, their exact mode of action, optimum concentration and developmental stages are still not known. Identification of efficient methods of inducing 2n-gamete formation will help increase pollen germination of sterile interspecific hybrids for inter-genomic recombination and introgression breeding to develop new polyploid cultivars and increase heterozygosity among plant populations. Additionally, the application of genomic tools and identification and isolation of genes and mechanisms involved in the induction of 2n-gamete will enable increased exploitation in different plant species, which will open new avenues for plant breeding. 相似文献16.
Measuring vessel length in vascular plants: can we divine the truth? History,theory, methods,and contrasting models 总被引:1,自引:0,他引:1
Key message
The Cohen method of measuring vessel-length distributions is much more accurate than the DD algorithm on integer values, which should be abandoned. More research is needed to get the real distribution of vessel length.Abstract
Scientists have been measuring the vessel length of plants for more than 50 years. The method involves infusing stem or segments with a visible substance that completely fills vessels cut open at the infusion surface. The number of infused vessels is then quantified versus distance from the infusion surface. A theoretical model is then used to convert the counts of infused vessels to a vessel length distribution. Over the years the methods and theory have changed greatly. The purpose of this review is to give the reader an understanding of why vessel length is important and to provide a theoretical basis for selection of the best method and theory to arrive at vessel length data. 相似文献17.
Purpose
to determine diagnosis and prognosis value of MRI in Peyronie’s disease.Material and Methods
thirty one penile MR examinations have been performed in 28 patients aged between 21 and 73. (1 tesla; surface coil; sagittal SET1, axial SET2 weighted, T1 before and after Gadolinium)Results
Conclusion
MRI can be helpfull in the pretreatment assessment and int he follow-up of Peyronie’s disease. 相似文献18.
Effects of nitrate concentration on the denitrification potential of a calcic cambisol and its fractions of N2, N2O and NO 总被引:1,自引:0,他引:1
Rui Wang Qi Feng Tingting Liao Xunhua Zheng Klaus Butterbach-Bahl Wei Zhang Chunyi Jin 《Plant and Soil》2013,363(1-2):175-189
Background and aims
The direct measurement of denitrification dynamics and its product fractions is important for parameterizing process-oriented model(s) for nitrogen cycling in various soils. The aims of this study are to a) directly measure the denitrification potential and the fractions of nitrogenous gases as products of the process in laboratory, b) investigate the effects of the nitrate (NO 3 ? ) concentration on emissions of denitrification gases, and c) test the hypothesis that denitrification can be a major pathway of nitrous oxide (N2O) and nitric oxide (NO) production in calcic cambisols under conditions of simultaneously sufficient supplies of carbon and nitrogen substrates and anaerobiosis as to be found to occur commonly in agricultural lands.Methods
Using the helium atmosphere (with or without oxygen) gas-flow-soil-core technique in laboratory, we directly measured the denitrification potential of a silt clay calcic cambisol and the production of nitrogen gas (N2), N2O and NO during denitrification under the conditions of seven levels of NO 3 ? concentrations (ranging from 10 to 250 mg N kg?1 dry soil) and an almost constant initial dissolved organic carbon concentration (300 mg C kg?1 dry soil).Results
Almost all the soil NO 3 ? was consumed during anaerobic incubation, with 80–88 % of the consumed NO 3 ? recovered by measuring nitrogenous gases. The results showed that the increases in initial NO 3 ? concentrations significantly enhanced the denitrification potential and the emissions of N2 and N2O as products of this process. Despite the wide range of initial NO 3 ? concentrations, the ratios of N2, N2O and NO products to denitrification potential showed much narrower ranges of 51–78 % for N2, 14–36 % for N2O and 5–22 % for NO.Conclusions
These results well support the above hypothesis and provide some parameters for simulating effects of variable soil NO 3 ? concentrations on denitrification process as needed for biogeochemical models. 相似文献19.
Aim
This study aimed at better characterising background nitrous oxide (N2O) emissions (BNE) in agricultural and natural lands.Methods
We compiled and analysed field-measured data for annual background N2O emission in agricultural (BNEA) and natural (BNEN) lands from 600 and 307 independent experimental studies, respectively.Results
There were no significant differences between BNEA (median: 0.70 & mean: 1.52 kg N2O???N ha?1 yr?1) and BNEN (median:0.31 & mean:1.75 kg N2O???N ha?1 yr?1) (P?>?0.05). A simultaneous comparison across all BNEA and BNEN indicated that BNEs from riparian, vegetable crop fields and intentional fallow areas were significantly higher than from boreal forests (P?<?0.05). Correlation and regression analyses supported the underlying associations of soil organic carbon (C), nitrogen (N), pH, bulk density (BD),and/or air temperature (AT) with BNEs to a varying degree as a function of land-use or ecosystem type (Ps?<?0.05).Conclusions
Although overall BNEN tended to be lower than BNEA on median basis, results in general suggest that land-use shifts between natural and managed production systems would not result in consistent changes in BNE. 相似文献20.