Agricultural soils are a significant source of nitrous oxide (N2O). Since mitigation of greenhouse gas emissions is needed in all sectors of society, it is important to identify the processes producing N2O and the factors affecting the production rates in agricultural soils. This study aimed to elucidate the N2O production in peat, clay and loamy sand at four different soil moisture conditions (40, 60, 80 and 100% Water Filled Pore Space). The acetylene inhibition technique was used to evaluate the contribution of nitrification to N2O production. Nitrous oxide production responded markedly to soil moisture in all three soils. The highest N2O production, measured at the wettest soils (100% WFPS), was up to four orders of magnitude higher than that at the dry soils (40% WFPS). In dry conditions N2O production decreased in the order of peat > clay > loamy sand, while in wet conditions the highest N2O production was measured in loamy sand, then in peat, and the lowest in clay soils. Nitrification was the dominant N2O producing process in all the soils at 60% WFPS. In the sandy soil 70% of the total N2O production originated from nitrification, while in the peat soil most of the total N2O production originated from denitrification. Data on processes producing N2O in agricultural soils are needed to develop process-based models that could reduce the uncertainty of the emission estimates in greenhouse gas inventories. 相似文献
Long-term studies of greenhouse gas fluxes from agricultural soils in different climate regions are needed to improve the existing calculation models used in greenhouse gas inventories. The aim of this study was to obtain more information on nitrous oxide (N2O) emissions from agricultural mineral soils in the boreal region. N2O emissions were studied during 2000–2002 on two soil types in Finland, a loamy sand and a clay with plots of grass, barley and fallow. N2O fluxes were measured with static chambers throughout the year. Other parameters measured were water filled pore space (WFPS), soil mineral nitrogen concentration, soil porosity, soil temperature and depth of soil frost. The annual fluxes from the clay soil ranged from 3.7 to 7.8 kg N ha–1 and those from sandy loam from 1.5 to 7.5 kg N ha–1. On average 60% of the annual fluxes occurred outside the growing season, from October to April. Increasing the number of freeze-thaw events was found to increase the fluxes during winter and during the thawing period in spring. The results suggest that N2O fluxes from these boreal mineral soils do not vary much as a function of applied fertiliser N and could probably be better estimated from soil physical properties, including soil porosity. 相似文献
Preparation of novel nanocomposite hydrogels opens up new avenues to next generation of biocompatible materials to be used in bioengineering and drug delivery. Toward this goal, chitosan nanocomposite hydrogels using click chemistry inspired cross‐linking are prepared. To enable this, Diels–Alder reaction of furan‐containing chitosan and maleimide‐coated gold nanoparticles is employed. The viscoelastic properties of the obtained nanocomposites as well as the effect of the nanoparticles as cross‐linkers are studied, indicating that they play significant role in hydrogel formation and stability. Nanoparticle‐enriched hydrogels are also found to demonstrate pH‐sensitivity therefore showing their potential for future biosensing applications.
The effect of heat treating gel films at different temperatures on the formation of the boehmite flaky structures on AISI 316 type austenitic stainless steel is investigated. After heating at different temperatures, the reactivity of the gel films with boiling water to form boehmite flakes was different, which resulted in different morphologies and different contact angle values after coating with hydrolyzed (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane (FAS). When the gel film was heat treated from 200 to 600 °C, the resulting contact angle was above 150°, indicating superhydrophobic behavior. However, when the gel film was heat treated below 200 °C as well as at 700 and 800 °C, only some boehmite flakes were formed; when the gel film was heat treated at 900 °C, no boehmite flakes were observed. In these cases the surface roughness is insufficient for the superhydrophobicity. The formation condition of the boehmite flakes by reaction of the gel film with boiling water is also tentatively discussed. 相似文献
Ant Colony Optimization (ACO) algorithms are basically developed for discrete optimization and hence their application to
continuous optimization problems require the transformation of a continuous search space to a discrete one by discretization
of the continuous decision variables. Thus, the allowable continuous range of decision variables is usually discretized into
a discrete set of allowable values and a search is then conducted over the resulting discrete search space for the optimum
solution. Due to the discretization of the search space on the decision variable, the performance of the ACO algorithms in
continuous problems is poor. In this paper a special version of multi-colony algorithm is proposed which helps to generate
a non-homogeneous and more or less random mesh in entire search space to minimize the possibility of loosing global optimum
domain. The proposed multi-colony algorithm presents a new scheme which is quite different from those used in multi criteria
and multi objective problems and parallelization schemes. The proposed algorithm can efficiently handle the combination of
discrete and continuous decision variables. To investigate the performance of the proposed algorithm, the well-known multimodal,
continuous, nonseparable, nonlinear, and illegal (CNNI) Fletcher–Powell function and complex 10-reservoir problem operation
optimization have been considered. It is concluded that the proposed algorithm provides promising and comparable solutions
with known global optimum results. 相似文献
X-ray fluorescence analysis is a highly useful technique for determining the chemical composition of matter. The present article describes the successful development of a wavelength-dispersive x-ray fluorescence spectrometer for a fairly high-energy range, 30-60 keV, that can contribute to studying lanthanides' Kbeta spectra with high-energy resolution. By combining a new high-energy synchrotron light source and the present spectrometer, it has been demonstrated that the full width at half maximum for lanthanum's Kbeta(1) is 32 eV and that all the peaks in the spectra are fully resolved. This corresponds to an energy resolution EDeltaE of 1180, which is ten times better than a conventional system based on a Ge detector, which can detect only two peaks, Kbeta(1) and Kbeta(2), in seven peaks. The present spectrometer can open up a new field in x-ray spectrometry. 相似文献
Collagen VI-related disorders are the second most common congenital muscular dystrophies for which no treatments are presently available. They are mostly caused by dominant-negative pathogenic variants in the genes encoding α chains of collagen VI, a heteromeric network forming collagen; for example, the c.877G>A; p.Gly293Arg COL6A1 variant, which alters the proper association of the tetramers to form microfibrils. We tested the potential of CRISPR/Cas9-based genome editing to silence or correct (using a donor template) a mutant allele in the dermal fibroblasts of four individuals bearing the c.877G>A pathogenic variant. Evaluation of gene-edited cells by next-generation sequencing revealed that correction of the mutant allele by homologous-directed repair occurred at a frequency lower than 1%. However, the presence of frameshift variants and others that provoked the silencing of the mutant allele were found in >40% of reads, with no effects on the wild-type allele. This was confirmed by droplet digital PCR with allele-specific probes, which revealed a reduction in the expression of the mutant allele. Finally, immunofluorescence analyses revealed a recovery in the collagen VI extracellular matrix. In summary, we demonstrate that CRISPR/Cas9 gene-edition can specifically reverse the pathogenic effects of a dominant negative variant in COL6A1. 相似文献
This study presents an evaluation of the catalytic performances of a Fe-exchanged Al-pillared synthetic beidellite for the wet hydrogen peroxide oxidation of phenolic aqueous wastes. The catalyst was prepared by a cation doping technique, its properties being determined by DRX, BET and chemical analysis techniques. All the tests were performed on a laboratory scale set-up.Important factors affecting catalyst activity and phenol removal efficiencies were studied, i.e. the effect of pH, temperature, catalyst concentration and the stability of the catalyst. The experimental results indicate that the use of this catalyst allows a total elimination of phenol and a significant removal of chemical oxygen demand, without significant leaching of Fe ions. Thus, considering the lowest Fe concentrations in solution after oxidation, at pH=5, 50 degrees C, and 180 min. COD removal efficiency of 87.9% was obtained. It was also observed that by using this catalyst, it is possible to extend the range of pH values for which Fenton-type oxidations can occur. 相似文献