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Biochar is widely recognized as an efficient tool for carbon sequestration and soil fertility. The understanding of its chemical and physical properties, which are strongly related to the type of the initial material used and pyrolysis conditions, is crucial to identify the most suitable application of biochar in soil. A selection of organic wastes with different characteristics (e.g., rice husk (RH), rice straw (RS), wood chips of apple tree (Malus pumila) (AB), and oak tree (Quercus serrata) (OB)) were pyrolyzed at different temperatures (400, 500, 600, 700, and 800 °C) in order to optimize the physicochemical properties of biochar as a soil amendment. Low-temperature pyrolysis produced high biochar yields; in contrast, high-temperature pyrolysis led to biochars with a high C content, large surface area, and high adsorption characteristics. Biochar obtained at 600 °C leads to a high recalcitrant character, whereas that obtained at 400 °C retains volatile and easily labile compounds. The biochar obtained from rice materials (RH and RS) showed a high yield and unique chemical properties because of the incorporation of silica elements into its chemical structure. The biochar obtained from wood materials (AB and OB) showed high carbon content and a high absorption character.

Biochar is utilized in modern society for multiple agricultural and environmental purposes in the framework of circular economy. The aims of this study were to review the leading edge of knowledge of studies where biochar was used in the agriculture sector, as an input for growing media, composting and to improve soil physical and chemical properties along with crop yield. Usage of biochar is promising as substitute for peat and in the composting as it reduces N losses, accelerates the process and improves the quality of final composts. The right selection of feedstock and optimization of pyrolysis conditions are key factors to tailor biochar thereby improving soil properties and increasing crop yield. Potential benefits and flaws for the usage of biochar technology in the agricultural domain are broadly reviewed and thoroughly discussed.

Aims We investigated the link between tree community composition and soil microbial community biomass and structure in central-eastern Spain. Methods The effects of the forest stand composition on the soil organic matter dynamics and on the structure and activity of the soil microbial community have been determined using phospholipid fatty acid profiles and soil enzymatic activities. Results The soil and litter N and C contents were higher in Pinus nigra Arn. ssp. salzmannii and Quercus ilex mixed forest stands (SBHO) and in long-term unmanaged Pinus nigra Arn. ssp. salzmannii forest stands (SBPC) than in pure Pinus nigra Arn. ssp. salzmannii forest stands (SBPA) and Pinus nigra Arn. ssp. salzmannii and Juniperus thurifera mixed forest stands (SBSJ). The bacterial biomass was significantly higher in SBSJ and SBPA than in SBPC and SBHO. The results show an uncoupling of the soil microbial biomass and its activity. pH is related to microbial biomass and its community structure under a Mediterranean humid climate. Conclusions The tree species seem to affect the biomass of the soil microbial community and its structure. The pH, but not the C/N ratio, is a factor influencing the microbial dynamics, biomass, and community structure.

Biochar application has received increasing attention as a means to trap recalcitrant carbon and enhance soil fertility. Hydrolytic enzymatic assays, such as β-glucosidase and phosphatase activities, are used for the assessment of soil quality and composting process, which are based on use of p-nitrophenol (PNP) derivatives as substrate. However, sorption capacity of biochar can interfere with colorimetric determination of the hydrolysed PNP, either by the sorption of the substrate or the reaction product of hydrolysis into biochar surface. The aim of the present work is to study the biochar sorption capacity for PNP in biochar-blended composting mixtures in order to assess its impact on the estimation of the colorimetric-based enzymatic assays. A retention test was conducted by adding a solution of known amounts of PNP in universal buffer solution (pH = 5, 6.5 and 11, corresponding to the β-glucosidase, acid and alkaline phosphatase activity assays, respectively), in samples taken at the initial stage and after maturation stage from four different composting piles (two manure composting piles; PM: poultry manure, CM: cow manure and two other similar piles containing 10% of additional biochar (PM + B, CM + B)). The results show that biochar-blended composts (PM + B, CM + B) generally exhibited low enzymatic activities, compared to manure compost without biochar (PM, CM). In terms of the difference between the initial and maturation stage of composting process, the PNP retention in biochar was shown higher at maturation stage, caused most probably by an enlarged proportion of biochar inside compost mixture after the selective degradation of easily decomposable organic matter. TThe retention of PNP on biochar was influenced by pH dependency of sorption capacity of biochar and/or PNP solubility, since PNP was more efficiently retained by biochar at low pH values (5 and 6.5) than at high pH values (11).

The ideal strengths of metals and alloys at finite temperatures have been studied using the statistical moment method. The tensile and shear strengths of the body-centered cubic (bcc) transition metals like Mo and W (refractory metals), and ordered FeAl (B2) and Fe3Al (DO3) alloys are calculated as a function of the temperature. The orthogonal tight-binding method is used for bcc transition elements, while the universal binding-energy relation (UBER)-type of pairwise potentials, derived from ab initio density-functional theory, is used for the FeAl and Fe3Al alloys. We discuss the temperature dependence of the tensile and shear strengths of the metals and alloys in conjunction with those of the second-order elastic constants.

Root-knot nematode (RKN) is a serious threat to crops worldwide due to the difficulty in controlling it and the limited eco-friendly alternatives to deal with the biotic stress it causes. In the present work, water-extractable fractions obtained from vermicompost (WSFv), vermicompost enriched with Trichoderma asperellum (WSFta) and T. virens (WSFtv) were tested as biotechnological tools to reduce the impacts of RKN on gas exchange, water use efficiency (WUE) and nutrient concentration in tomato and bell pepper plants. The plants were infected with 5000 eggs and eventual J2 of RKN and then treated with the water-extractable fractions for seven weeks. It was observed that the addition of WSFta, WSFtv and WSFv increased the CO2 assimilation, stomatal conductance and WUE in the tomato plants. In the bell pepper plants, WSFta, WSFtv, WSFv increased the stomatal conductance, while WUE was higher in the treatment with WSFtv. In fact, the parameters associated with the gas exchange were usually higher in the bell pepper than in the tomato plants. Overall, higher contents of N, Mg, B and Mn were detected when the extracts were applied in both bell pepper and tomato plants. The application of the water-extractable fractions, inoculated or not with Trichoderma, attenuates the RKN damage on the gas exchange parameters and successfully enhanced the nutrient concentration in the infected tomato and bell pepper plants, showing that it could be an important and promising tool for reducing the damage caused by this pathogen. We suggest that both the tomato and pepper plants can cope with the dilemma between growth and stress response via stomata regulation that are modulated by the WSF and Trichoderma.

The crack nucleation and propagation processes in nanoscale materials are studied using the ab initio constraint molecular dynamics method and the lattice Green's function method. We investigate the strength and fracture behaviors of carbon related nanoscale materials, especially the graphen sheets in comparison with those of carbon nanotubes. The linear elastic parameters, non-linear elastic instabilities, thermal lattice expansion and fracture behaviors are studied in detail. We will show that the thermodynamic and strength properties of the nanoscale materials exhibit characteristic features and they are different from those of the corresponding bulk materials.

The thermodynamic quantities of metals and alloys are studied using the moment method in the quantum statistical mechanics, going beyond the quasi-harmonic (QH) approximations. Including the power moments of the atomic displacements up to the fourth order, the free energies and the related thermodynamic quantities are derived explicitly in closed analytic forms. The configurational entropy term is taken into account by coupling the moment expansion scheme with the cluster variation method (CVM). The energetics of the binary (TaW) alloys are treated within the framework of the first principles tight-binding linear muffin-tin orbital (TB-LMTO) method coupled to the coherent potential approximation (CPA) and generalized perturbation method (GPM). The equilibrium phase diagrams are calculated for the refractory Ta-W bcc alloys.

The pressure dependence of the melting temperatures of tetrahedrally coordinated semiconductors are studied using the equation of states derived from the statistical moment method, in comparison with those of the normal metals. Using the general expressions of the limiting temperatures Tm, we calculate the melting temperatures of the semiconductor crystals and normal metals as a function of the hydrostatic pressure. The physical origins for the inverse pressure dependence of Tm observed for tetrahedrally coordinated semiconductors are also discussed.

The evaluation of residual organic materials as a source of enzymatic activities immobilized in the humus matrix is a little explored research area, particularly in the case of organic materials derived from municipal wastes. Enzymes catalyze most soil reactions essential for soil functionality. The advantage of humus enzyme-complexes (immobilized enzymes) with regards to free enzymes is that the former are protected in the humic colloid, being more resistant to denaturing agents and other adverse soil conditions. This explains the interest in use of organic wastes (which are produced in an increasingly amount and consequently are economical) as a source of immobilized enzymes, which could be concentrated and used to improve the quality of degraded or contaminated soils. The goal of this study was (i) to assess the potential of sewage sludge (SS) and the organic fraction of municipal solid waste (MSW), as well as their respective composts (CSS and CMSW) as sources of enzymes, (ii) to determine the proportion of such enzymes which are immobilized in the humic matrix of these organic materials, and (iii) to determine the effect of the composting process on the total and the immobilized enzymatic activities of the organic materials. Dehydrogenase (DHA), urease, protease-BAA, alkaline phosphatase (ALP), β-glucosidase (GLA) and o-diphenol oxidase (DPO) activities were determined both in the organic materials and in their humic extracts (except DHA). Sewage sludge had the highest total values of urease, protease-BAA, ALP and DHA activity (12.7 μol NH 4 + -N g −1 h −1 , 40.6 μmol NH 4 + -N g −1 h −1 , 75.7 μmol PNP g −1 h −1 and 0.3 μmol INTF g −1 h −1 , respectively), which decreased with composting, but MSW had the highest total value of DPO activity. For both organic materials, a low percentage of total enzymatic activities were linked to humus (0.6-22%), except in the case of DPO activity. The SS and MSW composting process had a positive effect on the urease, protease-BAA, DPO and ALP immobilization in the humic matrix, as reflected by the higher immobilized activity/total activity ratios in the compost than in the fresh materials.