ALBERT

Description: Porous shape memory alloys are a new class of advanced materials with combined advantages of both shape memory alloys and porous materials. In order to manufacture a porous shape memory alloy with the desired mechanical properties, it is important to predict its mechanical properties before fabrication. In this paper, a new unit cell model is proposed to simulate the mechanical stress-strain response of porous shape memory alloys. Microplane theory is used to attribute mechanical constitutive relations of shape memory alloys to the bulk material, and the finite element method is employed for numerical simulations. The results show a good agreement with the experimental stress-strain behavior reported in the literature. The effect of pore volume fraction on the stress-strain response is also studied using the proposed approach. Random microstructures are generated in the FE model, and the effects of randomness on the mechanical behavior of porous shape memory alloys are also investigated for different values of pore volume fraction.

Description: In the present work, Ni-WC powder was deposited on mild steel substrate to develop clads through microwave hybrid heating technique. The cladding trials were carried out in an industrial microwave applicator at 1.1 kW for 540 s. The Ni-WC composite clads were characterized for microstructure and abrasive wear performance through combination of x-ray diffraction, electron and optical microscopy, microhardness, and wear tests. Phase analysis of the Ni-WC clad indicated the presence of stable carbides such as WC, W 2 C, Ni 2 W 4 C, and Fe 6 W 6 C. The microstructure study of the clad layer revealed the presence of a uniformly distributed interlocked WC-based reinforcement embedded in the Ni-based matrix. The average Vicker’s microhardness in the clad layer was observed to be 1028 ± 90 HV, which was approximately three times the microhardness of the substrate. Abrasive wear resistance of the microwave clads was superior to the MS substrate. Abrasion was the main wear mechanism in the Ni-WC clads and the substrate samples. However, the presence of WC-based reinforcement in the composite clads reduced microcutting, resulting in enhanced wear resistance.

Description: Background and aims Soil amendments are often added to polluted soils to increase phytoremediation efficiency. Here we investigated the potential of a range of organic amendments for phytoextraction of heavy metals in a contaminated sediment. Methods Two experiments compared adsorption and phytoextraction of heavy metals by a Cd-hyperaccumulator Carpobrotus rossii grown in the contaminated sediment amended with six organic amendments. Results The adsorption capacity as measured by Langmuir adsorption maximum followed the order of Cr 〉 Zn 〉 Cu 〉 Cd, and the effect of organic amendments followed the order of chicken manure 〉 cow manure 〉 brown coal 〉 golden wattle biochar 〉 blue gum biochar 〉 radiata pine biochar. The addition of amendments increased the adsorption of heavy metals, with brown coal resulting in the lowest concentrations of water-extractable Cd, Cu and Zn. Two manures resulted in the highest concentrations of these water-extractable heavy metals in the rhizosphere soil of C. rossii. Furthermore, brown coal resulted in higher shoot accumulation of these heavy metals than three wood-derived biochars, whilst the manures generally had the lowest accumulation of Cd and Cu although they increased shoot biomass. Conclusions The addition of brown coal decreased whereas manure addition increased the mobility (water-extractable fraction) of heavy metals in rhizosphere soil. Phytoextraction of Cd and Cu was greater with brown coal than with biochars or manures. Brown coal is suitable for enhancing phytoextraction of these heavy metals because it could increase their accumulation in shoots of C. rossii and decrease the risk of leaching of these heavy metals into groundwater.

Description: Background and aims Cicer canariense has been shown to be a promiscuous legume. The symbiotic characteristics of several C. canariense mesorhizobial genospecies harbouring similar symbiotic genes are studied. Methods Comparative analysis of nodA and nifH gene phylogenies, and characterization of the symbiotic phenotypes on the basis of nodulation and nitrogen fixation was performed. Results Phylogenetic analyses of the nodulation gene nodA was in complete agreement with those previously done on nodC in grouping these mesorhizobia within symbiovar loti. In the nifH phylogeny, however, these strains were resolved into two subgroups named nifH-1 and nifH-2 . Subgroup nifH -1 contained strains from two genospecies and correlates with symbiovar loti, as it clustered with Mesorhizobium reference strains nodulating Lotus corniculatus . In contrast, subgroup nifH -2 contained strains of the other seven genospecies without reference strains and formed a distant branch on its own. Strains combining symbiovar loti genes in any chromosomal background effectively nodulated C. canariense , although with significant differences in nitrogen fixation capabilities. Conclusions Symbiovar loti genes are the most widely spread in the mesorhizobia that nodulate C. canariense in its natural habitat. They included two variants of the nifH gene and were found to be associated with nine chromosomal backgrounds (genospecies), resulting in strains showing different symbiotic effectiveness. Mesorhizobium tamadayense symbiovar loti strains were the most effective in this legume.

Description: Corrosion behavior of wrought Stellite 6B and Stellite 6K, which have similar chemical composition but contain different carbon content, in 3.5 wt.% NaCl solution and in Green Death solution is investigated using various electrochemical methods, including potentiodynamic polarization, cyclic polarization, and electrochemical impedance spectroscopy (EIS). The obtained potentiodynamic polarization curves, cyclic polarization curves, and EIS spectra for these alloys are in good agreement, showing that Stellite 6K with higher carbon content is easier corroded due to its larger volume fraction of carbides but the Cr 2 O 3 film formed on this alloy is stronger and more stable than that on Stellite 6B. Further immersion tests on these alloys show that Stellite 6K has less resistance to pitting corrosion.

Description: Background and Aims Competition between intercropped species is important for yield advantage, but little attention has been given to interspecific competitive dynamics in intercropping. Methods A field experiment with five cropping systems (wheat/maize, barley/maize intercropping, wheat, maize and barley sole cropping), two N levels (0 and 225 kg N ha −1 ) and two maize mulching treatments (with and without) were performed. Sequential harvest of subplots was performed between 7 and 10 times, and the data were fitted to a logistic growth model. Results Intercropping significantly increased the maximum biomass and maximum growth rates of wheat and barley, but suppressed the early and maximum growth rate of intercropped maize. Maize growth recovered after the wheat or barley was harvested. In the presence of film mulch and/or fertilization, maximum biomass of intercropped maize was close to or significantly higher than that of maize alone. Fertilization and film mulching had much stronger effects on growth of maize than on wheat and barley. Conclusions Interspecific competitive dynamics regulated by fertilization and film mulching can be quantified by the logistic model, which is helpful to understand the yield advantage of intercropping. This has important implications for managing interspecific competition through agronomic practices at field.

Description: Background and aims Take-all, caused by the soilborne pathogen Gaeumannomyces graminis var. tritici , ( Ggt ), is an important root disease of wheat. Continuous wheat cropping has been shown to induce take-all decline (TAD). This research investigated the mechanisms of TAD in 13 New Zealand soils in two experiments and identified the associated microorganisms using denaturing gradient gel electrophoresis (DGGE). Methods In Experiment 1, a sterile sand/maize-meal mixture inoculated or not inoculated with Ggt , was added at 4 % ( w / w ) to sterilised and non-sterilised soils to determine their ability to suppress take-all, and to help identify the nature of suppression. Experiment 2 investigated the transferability of suppressive properties in five of the soils from Experiment 1. The microbial communities of these five soils were analysed using PCR-DGGE. Results Ten of the soils were able to suppress take-all but the suppression was biological in nature in only four of these soils. The suppressive properties of two of the soils were transferred to a γ-irradiated base soil amended with Ggt , indicating that suppression could be specific in nature (i.e., attributed to a specific microorganism or group of microorganisms). The suppressive properties in one soil were not transferrable, suggesting a general form of suppression, most probably because the conditions in the soil were suitable for other microorganisms to compete with Ggt . DGGE analyses of the microbial communities for five of the soils showed similar banding patterns for those with similar forms of suppression (specific, general and non-suppressive) and identified the potential microorganisms that distinguished them. Conclusion These distinguishing microorganisms are likely to independently or interactively have a function in suppressing take-all.

Description: A solution to improve the formability of aluminum alloy sheets can consist in investigating warm forming processes. The optimization of forming process parameters needs a precise evaluation of material properties and sheet metal formability for actual operating environment. Based on the analytical M-K theory, a finite element (FE) M-K model was proposed to predict forming limit curves (FLCs) at different temperatures and strain rates. The influences of initial imperfection value ( f 0 ) and material thermos-viscoplastic model on the FLCs are discussed in this work. The flow stresses of AA5086 were characterized by uniaxial tensile tests at different temperatures (20, 150, and 200 °C) and equivalent strain rates (0.0125, 0.125, and 1.25 s −1 ). Three types of hardening models (power law model, saturation model, and mixed model) were proposed and adapted to correlate the experimental flow stresses. The three hardening models were implemented into the FE M-K model in order to predict FLCs for different forming conditions. The predicted limit strains are very sensitive to the thermo-viscoplastic modeling of AA5086 and to the calibration of the initial geometrical imperfection which controls the onset of necking.

Description: The present work is based on the study of the electrochemical response of mild steel as a function of machining configurations. The variable parameters were rake angle and turning speed, while feed rate and depth of cut remained fixed. Dynamic polarization tests and electrochemical impedance spectroscopy in 3.5% NaCl solution were done to analyze the electrochemical behavior of mild steels with the variation of rake angle and turning speed. The electrochemical response showed that the steel machined at higher speed and positive rake angle had higher resistance to charge transfer. Similarly, steel machined at lower speed and negative rake angle showed lower resistance to charge transfer. The results obtained in this study suggest that machining on mild steel should be carried out at positive rake angle and at higher speed to have smoother surface finish, strain-relieved surface grains, and subsequently better corrosion resistance, which was measured from corrosion current as determined by the Tafel extrapolation from the polarization plots.

Description: The effects of different nitrogen contents on the passivity of nickel-free stainless steels in 0.5 M sulfuric acid + 0.5 M sodium chloride solution were investigated by electrochemical impedance spectroscopy in the potential ranges of active dissolution and active-passive transition. A simplified reaction model containing adsorbed intermediates involved dissolution process, and passivation process was proposed to explain the impedance characteristics. Based on both equivalent circuit and mathematical model analysis, the effects of nitrogen on the passivity of stainless steels are discussed.

Description: The influence of heat treatment from 500 to 1100 °C on the 5 wt.% H 2 SO 4 solution-induced corrosion resistance of high-velocity oxygen-fuel sprayed WC-17Co coatings on 42CrMo steel was investigated, by using x-ray diffractometer (XRD), scanning electron microscopy (SEM)-energy-dispersive spectrometer (EDS), and polarization curve methods. XRD analysis showed decrease in W 2 C phase intensity with recrystallization of amorphous Co and generation of new Co 3 W 3 C and Co 6 W 6 C phases with heat treatment. Porosity distribution did not follow a particular pattern; it initially increased and then decreased with increasing temperature. Corrosion resistance sequence of the as-sprayed and heat-treated coatings in 5 wt.% H 2 SO 4 solution was C-5 〉 C-9 〉 C-A 〉 C-7 〉 C-11. Furthermore, microstructure and phase structure of heat-treated coatings revealed the formation of different discontinuous plate-like oxide films on the surface of the heat-treated coatings which indicated the vital effect of binder structure on the corrosion resistance.

Description: Isothermal die forging is one of near net-shape metal-forming technologies. Strict control of billet temperature during isothermal die forging is a guarantee for the excellent properties of final product. In this study, a new method is proposed to accurately control the billet temperature of complex superalloy casing, based on the finite element simulation and response surface methodology (RSM). The proposed method is accomplished by the following two steps. Firstly, the thermal compensation process is designed and optimized to overcome the inevitable heat loss of dies during hot forging. i.e., the layout and opening time of heaters assembled on die sleeves are optimized. Then, the effects of forging speed (the pressing velocity of hydraulic machine) and its changing time on the maximum billet temperature are discussed. Furthermore, the optimized forging speed and its changing time are obtained by RSM. Comparisons between the optimized and conventional die forging processes indicate that the proposed method can effectively control the billet temperature within the optimal forming temperature range. So, the optimized die forging processes can guarantee the high volume fraction of dynamic recrystallization, and restrict the rapid growth of grains in the forged superalloy casing.

Description: The hydriding-dehydriding process was used to recycle AZ40 magnesium (Mg) alloy scraps, and the microstructure nanocrystallization was realized. X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy were carried out to characterize the microstructure. After mechanically milling in hydrogen for 72 h, matrix Mg was completely turned into nanocrystalline MgH 2 , with an average crystallite size of about 10 nm. And then, the MgH 2 phase was completely transformed into Mg again through vacuum dehydriding treatment at 300 °C for 192 min, with an average crystallite size of about 20 nm. In addition, the nanocrystalline alloy powders were hot-pressed and extruded into bars. The average grain size of the bars was about 500 nm, which had reached the size of ultrafine-grain. Meanwhile, the yield strength and ultimate tensile strength of the as-extruded bars reached about 312 and 497 MPa, respectively. The results indicate that hydriding-dehydriding process is a feasible method for recycling of Mg alloy scraps, and it is expected to have a good application prospect in preparing ultrafine-grain Mg alloys.

Description: In this study, the effect of KOH concentration on the electrochemical properties of micro-arc oxidation (MAO) coated Mg alloy AZ31B has been investigated. Also, the surface morphology and chemical composition of the MAO coatings have been characterized by scanning electron microscopy and x-ray diffraction. In MAO process, an increase in the concentration of KOH as a result of increase in the electrolyte electrical conductivity leads to a reduction in sparking which in turn improves the quality and the behavior of anodic coatings in the concentration of 2.5 M. Moreover, it can be concluded that the MAO coating shows its best protective behavior when KOH concentration is equal 2.5 M, and if the concentration is higher or lower than this value, the protective properties of MAO coating will decrease.

Description: Aims To determine the impact of long-term rabbit and sheep grazing on Salix repens N status (green and abscised leaf N content and C:N ratio), internal N dynamics and soil N supply rate in dune slacks. Methods Herbivore exclosures were erected in dune slacks at Ainsdale Sand Dunes NNR, creating three grazing treatments: rabbit grazing; rabbits excluded for 36 years; rabbit grazing followed by sheep and rabbit grazing for 18 years. Soil N supply rate was analysed using ion exchange membranes; leaf N dynamics of S. repens were measured over one summer. Results Soil N supply rate was higher in ungrazed plots. There was no difference in green leaf N MASS or C:N ratio between treatments, but N dynamics differed. Adding sheep to existing rabbit grazing reduced S. repens N resorption efficiency (R EFF ) from 67 to 37 %; excluding rabbits had no impact. Litter N MASS was lower and C:N ratio higher in ungrazed plots. Conclusions Grazing can impact significantly on leaf N resorption, but this impact depends on the grazing regime.

Description: Titanium aluminide alloys are good candidates for structural applications thanks to their low density and good balance of properties up to relatively high temperatures. However, their application is still limited by significant oxidation. Four γ-TiAl alloys with different content of aluminum and niobium were produced by electron beam melting: Ti-45Al-2Cr-2Nb, Ti-48Al-2Cr-2Nb, Ti-45Al-2Cr-8Nb, and Ti-46Al-2Cr-8Nb. The behavior of these alloys in response to oxidation in air during constant heating up to 1000 °C and isothermal oxidation for 10 h at 850 and 950 °C were studied by thermogravimetric analysis. The mass gain due to oxidation of the low Nb-containing alloys was always at least twice that of the high Nb-containing alloys. Both low and high Nb-containing alloys exhibited on their surface oxidation products of the same nature: oxides TiO 2 and Al 2 O 3 , and nitrides TiN and Ti 2 AlN. Niobium addition up to 8 at.% did not suppress the growth of rutile and promote the formation of a protective alumina layer. However, it efficiently reduced the formation of rutile, mainly responsible for the mass gain due to oxidation of γ-TiAl alloys and with tendency to spallation.

Description: Strengthening of aluminum alloy 2219 by thermo-mechanical treatment has been compared with artificial aging. Three simple deformation modes including pre-stretching, compression, and rolling have been used in thermo-mechanical treatment. The tensile strength, elongation, fracture feature, and precipitated phase have been investigated. The results show that the strengthening effect of thermo-mechanical treatment is better than the one of artificial aging. Especially, the yield strength significantly increases with a small decrease of elongation. When the specimen is pre-stretched to 8.0%, the yield strength reaches 385.0 MPa and increases by 22.2% in comparison to the one obtained in aging condition. The maximum tensile strength of 472.4 MPa is achieved with 4.0% thickness reduction by compression. The fracture morphology reveals locally ductile and brittle failure mechanism, while the coarse second-phase particles distribute on the fracture surface. The intermediate phases θ ″ or θ ′ orthogonally precipitate in the matrix after thermo-mechanical treatment. As compared to artificial aging, the cold plastic deformation increases distribution homogeneity and the volume fraction of θ′′ or θ′ precipitates. These result in a better strengthening effect.

Description: Aims Maize ( Zea mays L.) is one of the most important crops worldwide. Despite several studies on maize roots, there is limited information on the function of different root types in extracting water from soils. Aim of this study was to investigate the location of water uptake in maize roots. Methods We used neutron radiography to image the spatial distribution of maize roots in soil and trace the transport of deuterated water (D 2 O) in soil and roots. Maize plants were grown in aluminum containers filled with a sandy soil that was kept homogeneously wet throughout the experiment. When the plants were 16 days old, we injected D 2 O into selected soil regions. The transport of D 2 O was simulated using a diffusion–convection numerical model. By fitting the observed D 2 O transport we quantified the diffusion coefficient and the water uptake of the different root segments. Results The root architecture of a 16 day-old maize consisted of a primary root, 4–5 seminal roots and many lateral roots. Laterals emerged from the proximal 15 cm of the primary and seminal roots. During both day and night measurements, D 2 O entered more quickly into lateral roots than into primary and seminal roots. The quick transport of D 2 O into laterals was caused by the small radius of lateral roots. The diffusion coefficient of lateral roots (4.68 × 10 −7  cm 2  s −1 ) was similar to that of the distal unbranched segments of seminal roots (4.72 × 10 −7  cm 2  s −1 ) and higher than that of the proximal branched segments (1.42 × 10 −7  cm 2  s −1 ). Water uptake of lateral roots (1.64 × 10 −5  cm s −1 ) was much higher than the uptake of seminal roots, which was 5.34 × 10 −10  cm s −1 in the proximal branched segments and only 1.18 × 10 −12  cm s −1 in the distal unbranched segments. Conclusions We conclude that the function of lateral roots is to absorb water from the soil, while the function of the primary and seminal roots is to axially transport water to the shoot.

Description: Nano-crystalline and amorphous Co-P coatings were deposited on plain carbon steel substrates by using direct current. Effects of electrolyte pH on morphology, current efficiency, phosphorus content, hardness, and preferred orientation of the nano-crystalline coatings were investigated. Moreover, the effects of heat treatment on microstructure and hardness of the nano-crystalline and the amorphous coatings were studied. The results showed that, phosphorus content and hardness of the nano-crystalline coatings were decreased by increasing of the pH, in spite of a current efficiency enhancement to as much as 98%. Grain size and preferred orientation were also changed from 13 to 31 nm and from mostly [002] to [100] by increasing the pH from 1 to 4, respectively. Smoother coatings and higher current efficiencies were obtained by the addition of 1 g/L sodium dodecyl sulfate (SDS) to the bath. Highest hardness of the nano-crystalline and the amorphous coatings was about 600 and 750 HV, which increased and reached 760 and 1090 HV after heat treatment, respectively.

Description: In this study, the stability and microstructural evolution, including grain size and hardness of nanocrystalline Fe 91 Ni 8 Zr 1 alloyed powders, produced by ball milling, were investigated after annealing at 900 and 1000 °C for up to 24 h. Results indicate that rapid grain growth to the micron scale occurs within the first few minutes of exposure to the elevated annealing temperatures. However, despite the loss of nanocrystallinity, an extremely stable and efficient hardening effect persists, which has been found to be equal to that predicted by Hall-Petch strengthening even at the smallest grain sizes. The mechanical properties of the samples consolidated to bulk via equal channel angular extrusion at 900 °C were evaluated by uniaxial compression at room and elevated temperatures. Results reveal high compressive yield stress as well as the appearance and disappearance of a yield drop indicating the presence of coherent (GP zone like) precipitates within the microstructure. Such a hardening mechanism has implications for developing new Fe-Ni-based alloys exhibiting a combination of high strength and ductility for high temperature applications.

Description: Aims Kin selection and resource partitioning have been proposed to explain interactions between plants growing with siblings (from the same mother). These mechanisms have been examined by measurements of fitness, phenotype or allocation traits, but have seldom been tested with N acquisition traits. Methods We determine if kin selection and resource partitioning are occurring using two annual species ( Sorghum vulgare and Glycine max ) with a short-term 15 N experiment. A mixture of ammonium, nitrate and glycine (1:1:1) was injected into soils around plants after they grew for 47 days. Only one nitrogen (N) form was 15 N labeled in each labeling solution. Results S. vulgare increased root allocation when growing with strangers (from the different mother), but not increase their N uptake. Although G. max strangers did not increase their root allocation, they significantly increased uptake of total N and the most abundant N form (nitrate) and decreased uptake of the least abundant (glycine). Conclusions G. max siblings reduced competition due to chemical resource partitioning while S. vulgare showed kin selection. We concluded that processes related to kin selection and resource partitioning can occur simultaneously, resulting in different competitive ability. These findings can improve our understanding of plants growing with siblings or strangers.

Description: Aims The aim was to devise a practical soil sampling design for oil palm plantations that takes into account tree-scale variability, thus facilitating detection of trends in soil properties over time. Methods We geometrically evaluated the ability of linear sampling transects to represent the distribution of typical management zones and radial patterns known to influence soil properties. The effect of sampling point density was tested using interpolated surfaces of soil biological, chemical and physical properties derived from values measured on a 35-point sampling grid covering the repeating tree unit in plantations with 15–25-year old palms. Results The ability of sampling transects to represent the proportion of the plantation in various zones improved with increasing transect length and sampling density. Increasing the number of sampling points from 10 to 50 (using an acceptably long transect with length 5.57 × palm spacing) decreased the maximum deviation between the overall mean and the transect-derived mean from 15.9 to 5.6 % for the most variable parameter, respiration, and 3.2 to 0.6 % for the least variable parameter, bulk density. Conclusions Transect sampling provides an efficient means of obtaining a composite soil sample that accounts for tree-scale variability in oil palm plantations. The method is readily adaptable for other tree crops.

Description: Agglomerated TiB 2 particle and network-like structure-reinforced titanium matrix composite coatings were prepared by laser cladding of the Ni + TiB 2  + Ti preplaced powders on Ti-6Al-4V alloy. The network-like structure mainly consisted of NiTi and Ni 3 Ti. Through the experiment, it was found that the size of agglomerated particle gradually decreased with the increase of Ti content, but the number of the network-like structure first increased and then disappeared. In-situ reaction competition mechanism and the formation of network-like structure were discussed. The average micro-hardness gradually decreased with the increase of Ti content, but the average fracture toughness gradually increased. Meanwhile, the wear resistance of the coatings is higher than that of the substrate, but the wear loss of the coatings is gradually increased with the increase of Ti content.

Description: This paper investigates the effect of quenching and aging treatment on microstructure and abrasive wear of Ti-6Al-4V alloy. The as-received alloy was solution treated at 1339 K, then oil quenched, followed by aging at 823 K for 4 h (14,400 s). The microstructures of as-received and quench-aged specimens were characterized by using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and electron backscattered diffraction techniques. The as-received specimen consisted of very fine α grains (average grain size 2 μm) with β phase uniformly dispersed throughout. The microstructure of the quench-aged specimen showed α plates (formed by the decomposition of α′ during aging). The β phase precipitated out of α′ martensite during aging and hence was dispersed uniformly in the α matrix. Ti-6Al-4V alloy was quench-aged to achieve maximum hardness with a view that the increased hardness would lead to an improvement in abrasive wear behavior. Two-body abrasive wear tests were carried out on the as-received and quench-aged specimens using pin-on-disk apparatus with SiC as abrasive media (150-grit size). The effect of sliding distance and normal load on the abrasive wear behavior was studied. The wear resistance of the as-received specimen was greater than that of quench-aged specimen, while hardness of the as-received specimen was lower than that of quench-aged specimen. The abrasive wear behavior of Ti-6Al-4V alloy has been explained based on morphology/microstructure of the alloy and the associated wear mechanism(s).

Description: Background Botanists, ecologists and evolutionary biologists are familiar with the astonishing species richness and endemism of the fynbos of the Cape Floristic Region and the ancient and unique flora of the kwongkan of south-western Australia. These regions represent old climatically-buffered infertile landscapes (OCBILs) that are the basis of a general hypothesis to explain their richness and endemism. However, few ecologists are familiar with the campo rupestre of central and eastern Brazil, an extremely old mountaintop ecosystem that is both a museum of ancient lineages and a cradle of continuing diversification of endemic lineages. Scope Diversification of some lineages of campo rupestre pre-dates diversification of lowland cerrado , suggesting it may be the most ancient open vegetation in eastern South America. This vegetation comprises more than 5000 plant species, nearly 15 % of Brazil’s plant diversity, in an area corresponding to 0.78 % of its surface. Reviewing empirical data, we scrutinise five predictions of the OCBIL theory, and show that campo rupestre is fully comparable to and remarkably convergent with both fynbos and kwongkan , and fulfills the criteria for a classic OCBIL. Conclusions The increasing threats to campo rupestre are compromising ecosystem services and we argue for the implementation of more effective conservation and restoration strategies.

Description: In this study, in order to investigate the relationship between surface roughness and the corrosion resistance of the SS 316 LVM wires, samples have been prepared with different surface roughness by using different grits of SiC papers. In order to simulate the environment of implanted biomedical devices, a three-electrode electrochemical cell with 0.9% (by mass) NaCl solution has been used to test the corrosion resistance of the samples by potentiodynamic method and anodic polarization tests. SEM, EDS, and XPS have been performed to analyze the surfaces appearance and chemical elements on the surface before and after the corrosion. AFM was also used to get 3D images of the surface and to show the change in roughness of the samples after corrosion testing. Background-subtracted contrast-enhanced microscopy has been performed in situ to detect the pitting process happening on the surface of stainless steel samples. It was concluded that a relatively smoother surface can result in higher corrosion resistance and larger potential of stable pitting, whereas a rougher surface can easily go into stable pitting with lower pitting potentials. Rougher surfaces also showed a shorter time for the formation of stable pits. Microscopy observations illustrated more corrosion on rougher surfaces, and EDS showed more chloride ion remained on these surfaces.

Description: Aims The colonization pattern of three grapevine endophytes (families Sphingomonadaceae and Enterobacteriaceae) and their putative metabolic signature in plants were analyzed on Vitis vinifera L. cv. Pinot noir to determine the behavior of endophytic strains inside plants as well as how plants respond to such microsymbionts. Methods Strains Enterobacter ludwigii EnVs6, Pantoea vagans PaVv7 and Sphingomonas phyllosphaerae SpVs6, were root inoculated on micropropagated grapevine plantlets and colonization was determined by double labeling of oligonucleotide probes-fluorescence in situ hybridization (DOPE-FISH) coupled with confocal microscopy. After inoculation, the metabolic signature in plants colonized by Enterobacter ludwigii EnVs6 was further studied using UPLC//tandem mass spectrometry analysis. Results E. ludwigii EnVs6 and P. vagans PaVv7 colonized the plantlets and were both observed on the root surfaces and as endophytes in the cortex and inside the central cylinder up to xylem vessels, but not in the systemic plant parts. Strain SpVs6 also efficiently colonized the root surface, but not the endorhiza and was therefore not detected as an endophyte. A metabolic signature in plants inoculated with E. ludwigii EnVs6 was depicted, resulting in a significant increase in vanillic acid and a decrease in the concentration of catechin, esculin, arbutin, astringin, pallidol, ampelopsin, D-quadrangularin and isohopeaphenol. Changes in the concentration of epicatechin, procyanidin 1, taxifolin and the sum of quercetin-3-glucoside and quercetin-3-galactoside, in roots and stems were also detected, showing that the effect of colonization of plants is most prominent in the stems. Conclusions Colonization patterns in endophytes are divergent according to the strains used. A metabolic signature suggests the activation of pathways involved in plant defense but also modulation of the production of metabolites that are keys for colonization.

Description: Background We hypothesize that invasive English ivy ( Hedera helix ) harbors endophytic microbes that promote plant growth and survival. To evaluate this hypothesis, we examined endophytic bacteria in English ivy and evaluated effects on the host plant. Methods Endophytic bacteria were isolated from multiple populations of English ivy in New Brunswick, NJ. Bacteria were identified as a single species Bacillus amyloliquefaciens . One strain of B. amyloliquefaciens , strain C6c, was characterized for indoleacetic acid (IAA) production, secretion of hydrolytic enzymes, phosphate solubilization, and antibiosis against pathogens. PCR was used to amplify lipopeptide genes and their secretion into culture media was detected by MALDI-TOF mass spectrometry. Capability to promote growth of English ivy was evaluated in greenhouse experiments. The capacity of C6c to protect plants from disease was evaluated by exposing B+ (bacterium inoculated) and B− (non-inoculated) plants to the necrotrophic pathogen Alternaria tenuissima . Results B. amyloliquefaciens C6c systemically colonized leaves, petioles, and seeds of English ivy. C6c synthesized IAA and inhibited plant pathogens. MALDI-TOF mass spectrometry analysis revealed secretion of antifungal lipopeptides surfactin, iturin, bacillomycin, and fengycin. C6c promoted the growth of English ivy in low and high soil nitrogen conditions. This endophytic bacterium efficiently controlled disease caused by Alternaria tenuissima . Conclusions This study suggests that B. amyloliquefaciens plays an important role in enhancing growth and disease protection of English ivy.

Description: Background and aims Alkaline soils, characterized by high pH, are representative of degraded regions throughout the world. Studying germination in relation to alkalinity can contribute to understanding how species cope with such conditions. Although the effects of pH have been widely studied, it is unknown whether germination response to pH gradients created with buffer solutions is representative of the conditions experienced in alkaline soils. Our aims were to (1) determine if high pH gives an accurate assessment of the effects of alkaline soils on germination, and (2) identify the inhibitory factors for germination in alkaline soils. Methods Using Leymus chinensis seeds, germination was tested over a gradient of pH solutions prepared using Tris (50 mM and 100 mM) and H 2 O buffers and eight germination media prepared from non-alkaline and alkaline soils with different pH and electrical conductivities (EC). Additionally, solutions of 10–100 mM NaCl, Na 2 SO 4 , Na 2 CO 3 and NaHCO 3 were used to determine the main ions inhibiting seed germination. Results H 2 O-buffered pH had no effect on seed germination, and seed germination was much lower at all pH levels in 50 mM Tris–HCl solutions (pH 7.0–10.35) than in the H 2 O control (pH 7.05). No seeds germinated in 100 mM Tris–HCl buffers irrespective of the pH. In alkaline germination media (pH 10.04–10.61), high germination was obtained only at low EC. The rank order of the inhibitory effect of salts was Na 2 CO 3  〉 NaHCO 3  〉 NaCl 〉 Na 2 SO 4 . Conclusions Buffer solutions used to simulate alkaline environments did not provide a reliable indicator of the effects of alkaline soils on seed germination. High pH of alkaline soil had no negative effects, and results suggest that salt composition and concentration, especially CO 3 2− and HCO 3 − , are key inhibitors.

Description: Background and aims Exotic plant species experience conditions in their introduced ranges that differ from those in their native range. Exotic plants may experience genetic changes in traits related to resource use, abiotic stress tolerance, and biotic interactions in response to such novel biotic and abiotic environments. Methods We conducted a pot experiment in the native range to investigate how soil fertility, soil salinity and soil sterilization together determine the performances of native (China) and invasive (US) populations of the tree Triadica sebifera . Results Salinity decreased plant growth, and increased AMF colonization and root:shoot. Fertilization or an unsterilized soil biota reduced the negative effects of salinity on plant survival. Fertilization decreased AMFcolonization and root:shoot ratio. Biomass was positively related to AMF colonization in unfertilized soils only. Seedlings from invasive populations grew faster and had higher AMF colonization. Conclusions Our results suggest that this invasive plant is able to persist in more saline environments when soil fertility is high or suitable AMF is present. The importance of the soil biota appears to be greater on low fertility soils where AMF provides significant benefits. The greater AMF association of plants from invasive populations suggests that resources, abiotic stress, and biotic interactions all may play a role in successful plant invasions.

Description: Background and aims Niche complementarity arising from divergence in resource use is an important mechanism underlying species coexistence. We hypothesized fertilization with different N forms would generate plastic divergence among species with regard to their N form uptake and preference. Methods In the eighth year of a long-term N fertilization experiment in an alpine meadow on the Tibetan plateau, we labeled 11 common plant species with ammonium- 15 N or nitate- 15 N in subplots without fertilization (control) or fertilized with 7.5 g N m −2  yr −1 in the form of ammonium, nitrate, or ammonium nitrate to trace N form uptake. Results Depending on species, fertilization with nitrate or ammonium nitrate had positive, negative or neutral effects on NO 3 -N uptake rate, although ammonium fertilization showed little impact. By contrast, fertilization with any N form had little impact on NH 4 -N uptake rate. Consequently, effects of nitrate fertilization and ammonium nitrate fertilization on relative N form preference diverged among the species and the functional groups (grasses, sedges, legumes and forbs). Conclusions Alpine plant species can diverge in N form uptake and preference in response to long-term N fertilization, and such divergence may contribute to species coexistence after long-term fertilization.

Description: Aims Stomata can close to avoid cavitation under decreased soil water availability. This closure can be triggered by hydraulic (‘H’) and/or chemical signals (‘C’, ‘H + C’). By combining plant hydraulic relations with a model for stomatal conductance, including chemical signalling, our aim was to derive direct relations that link soil water availability, expressed as fraction of roots in dry soil (f dry ), to transpiration reduction. Methods We used the mechanistic soil-root water flow model R-SWMS to verify this relation. Virtual split root experiments were simulated, comparing horizontal and vertical splits with varying f dry and different strengths of stomatal regulation by chemical and hydraulic signals. Results Transpiration reduction predicted by the direct relations was in good agreement with numerical simulations. For small enough potential transpiration and large enough root hydraulic conductivity and stomatal sensitivity to chemical signalling isohydric plant behaviour originates from H + C control whereas anisohydric behaviour emerges from C control. For C control the relation between transpiration reduction and f dry becomes independent of transpiration rate whereas H + C control results in stronger reduction for higher transpiration rates. Conclusion Direct relations that link effective soil water potential and leaf water potential can describe different stomatal control resulting in contrasting behaviour.

Description: Background and Aims Interspecific differences have been clearly shown in the contribution of endogenous spatial autocorrelation (caused by dispersal) to the spatial structure of undisturbed vegetation. However, this phenomenon has not been studied in industrially polluted areas, where heavy metals’ excess is traditionally considered to be the main driver of ecosystem processes. We compare the contributions of endogenous autocorrelation and environmental parameters to the distribution of herbaceous plants in open and forested sites heavily polluted with copper smelter emissions. Methods Principal coordinates of neighbour matrices were used to create spatial predictors that were incorporated into beta regression models together with environmental predictors. Their importance for species’ spatial structure was assessed using multimodel inference and variation partitioning approach. Results Equisetum sylvaticum, Leucanthemum vulgare, Tussilago farfara, Carex rostrata, Scirpus sylvaticus and Deschampsia cespitosa responded strongly to soil toxicity, while Agrostis capillaris and Lychnis flos-cuculi , to microtopography and tree disposition. Endogenous autocorrelation was strongly pronounced in L. flos-cuculi distribution across all study sites and was substantial for A. capillaris in open areas. Conclusion Despite the extreme level of soil toxicity, the importance of other environmental parameters and endogenous autocorrelation remarkably differed among species, resulting from interspecific differences in ecological preferences and dispersal mode.

Description: Background and aims Acid leached soils developed on loessic materials in Central Belgium present homogenous edaphic characteristics and similar patterns of strontium isotopic composition ( 87 Sr/ 86 Sr), used as tracer of the origin of calcium. This was inconsistent with the large range of 87 Sr/ 86 Sr ratios measured in leaves from beech stands developed on the sites. We hypothesised that the deep carbonate-bearing horizon (〉2.5 m) with low 87 Sr/ 86 Sr ratio, could be a complementary source of Ca for tree nutrition. Methods We studied the change in foliar Sr isotopic composition and element concentrations in 12 forest sites along a soil sequence. This soil sequence was selected to include the largest range of variations in the depth at which the calcareous loess horizon occurs. In complement, root depth development was determined in six sites down to 300 cm. Results Our results reveal that Sr originating from deep carbonate influences significantly the isotopic composition of beech trees growing on loessic soils. This influence contributes from 20 to 80 % to the Ca nutrition of trees depending on their position along the soil sequence. Conclusions Despite its deep location in the soil profile, the carbonate-bearing horizon is determinant for the nutrient status of these forests.

Description: Aims Plant root traits affect soil biopore (BP) formation. Aims of this study were to measure the effects of fodder crop species with contrasting root traits and duration of cropping on BP density (BPD), and also to address the consistency of these effects over different years focusing on the effects of root decay. Methods Soil BPD was quantified after growing three perennial fodder crop species with contrasting root systems, namely, lucerne ( Medicago sativa L.), chicory ( Cichorium intybus L.) and tall fescue ( Festuca arundinacea Schreb.) for 1, 2, and 3 years with 2 years fallow in two repeated field trials from 2007 to 2014. Results Total BPD after taprooted fodder crops (421 ± 14 m −1 ) was significantly higher compared with fibrous-rooted crops (337 ± 12 m −1 ). Cropping duration did not affect soil BPD. On average, density of medium-sized BP (BP med ; 2–5 mm) increased 14 % after 2 years of fallow, whereas BPD decreased by 5 % for coarse-sized BP (BP cor ; 〉5 mm) after the fallow. Conclusions Taprooted fodder crops enhanced BP formation into subsoil. Accurate assessment of biopores (BPs) and their persistence must take account of the temporal dynamics, including effects of root decay.

Description: Background and aims Plant adaptation to waterlogged conditions requires a set of morphological and physiological/biochemical changes. The formation of aerenchyma is one of the most crucial adaptive traits for waterlogging tolerance. Enzymatic scavenging may also potentially contribute to waterlogging tolerance by providing detoxification of reactive oxygen species (ROS). Methods Changes of root porosity (as an indicator of aerenchyma formation) and activities in leaves of four major antioxidant enzymes, γ-amino butyric acid (GABA) and lactic acid contents in roots were evaluated in six barley genotypes contrasting in waterlogging tolerance. Results Soil waterlogging caused significant increases in adventitious root porosity in all genotypes. Waterlogging-tolerant genotypes showed not only significantly higher adventitious root porosity than sensitive genotypes but also much faster development of aerenchyma. The greatest difference in adventitious root porosity among genotypes was observed after 7 days of waterlogging treatment. At the same time, antioxidant enzyme activities in leaves, GABA and lactic acid contents in roots did not correlate with waterlogging tolerance. Conclusions A faster formation of aerenchyma in adventitious roots is one of the key factors for waterlogging tolerance in barley. This protocol is recommended to be applied in future studies to identify molecular markers linked to this trait using appropriate mapping populations.

Description: Superaustenitic stainless steel 654SMO was used as the experimental material to investigate the effect of heating temperatures and holding times on grain growth behavior in the temperature range of 1150-1250 °C and holding time ranging from 15 to 60 min. The contour maps of grain size and grain growth rate as a function of temperatures and times were plotted. The results of this study suggest that grains grow with parabolic trend. Grain size and its growth rate increase with increasing heating temperature, the former also increases with holding time, while the latter decreases with holding time. Both grain size and grain growth rate are more sensitive to holding time than solution temperature at temperatures below 1200 °C, which is contrary to that of at temperatures above 1200 °C. The growth behavior of grains in the tested steel is illustrated by a modified mathematical model deduced on the basis of previous empirical models, and this modified grain growth model can fit well with the experimental grain growth data obtained during solution treatment.

Description: An attempt to the modification of the microstructure and mechanical properties of affordable, Mn-containing maraging alloys is reported. These alloys have demonstrated strong age hardening but suffered with premature intergranular brittleness despite their potential applications in tooling, dies, and machinery industries. An Fe-10Ni-6Mo-3Mn-1Ti (wt.%) alloy was prepared by vacuum melting and processed by homogenization (1250 °C/48 h), cold rolling, solution annealing (950 °C/1 h), and aging treatments (500 °C/4 h). It presented tensile strength of about 2.65 GPa, a few percent of tensile elongation and a mixed ductile-brittle fracture mode. Transmission electron microscopy (TEM) revealed the precipitation of a nearly spherical phase. Crystal symmetry of the second phase precipitates was identified hexagonal close-packed corresponding reasonably to the Fe 2 Mo Laves phase having lattice parameters of a  = 0.4745 and c  = 0.7754 nm. Precipitation of a Mo-enriched second-phase particle was occasionally found at prior austenite grain boundaries but the pronounced grain boundary precipitation was never identified. Energy-filtering transmission electron microscopy using the Mo-M 4,5 post edge revealed remarkable segregation of Mo at grain boundaries.

Description: Friction stir welding was performed to join carbon steel plates at tool rotational rate of 800-1400 rpm. Microstructure and microhardness of welded specimens were evaluated across weld centerline. Torque base index, peak temperature, cooling rate, strain, strain rate, volumetric material flow rate, and width of extruded zone at weld nugget were calculated. Peak temperature at weld nugget was ~1300-1360 K. At this temperature, ferrite transformed to austenite during welding. Austenite was decomposed in to ferrite and bainite at cooling rate of ~4-7.5 K/s. The presence of bainite was endorsed by increment in microhardness with respect to base material. Ferrite grain size at weld nugget was finer in comparison to as-received alloy. With the increment in tool rotational rate strain, strain rate, total heat input, and peak temperature at weld nugget were increased. High temperature at weld nugget promoted increment in ferrite grain size and reduction in area fraction of bainite. Heat-affected zone also experienced phase transformation and exhibited enhancement in ferrite grain size in comparison to base alloy at all welding parameters with marginal drop in microhardness. Maximum joint strength was obtained at the tool rotational rate of 1000 rpm. Increment in tool rational rate reduced the joint efficiency owing to increment in ferrite grain size and reduction in pearlite area fraction at heat-affected zone.

Description: The strain-controlled low-cycle fatigue properties of gravity cast Al-Si-Cu alloys for engine cylinder heads were investigated. At strain ratios of R ε  = −2, 0, and 0.1, the cyclic stress amplitude progressively increased from initiation to the 450th cycle, and then proceeded into a steady stage until failure. At a strain ratio of R ε  = −∞, the material exhibited a continuous cyclic hardening. The hysteresis loops in this alloy for the 2nd and half-life cycle were tension/compression asymmetry, which also corresponded well to the evolution of peak/valley stress. Transmission electron microscopy analysis suggested that cyclic hardening was caused by the dislocations multiplication/tangles at strain ratios of R ε  = −∞ and 0. Besides, the presence of dislocation cross slip contributed to cyclic stabilization observed at later stage of deformation at a strain ratio of R ε  = 0. Micro-analysis of specimen fracture appearance was conducted in order to obtain the fracture characteristics and crack paths for different strain ratios. It showed that the fatigue cracks initiated basically at the internal defects in the samples. Meanwhile, at strain ratios of R   =  −∞ and 0, the fracture surface was rough with a large number of small unequiaxed dimples and some tear ridges. Moreover, the localized pores offered a preferential crack path in the samples, where they were surrounded by silicon particles. At a strain ratio of R ε  = −∞, the fatigue cracks preferentially initiated at pores rather than α-Fe phases. At a strain ratio of R ε  = 0, where fatigue crack initiation was observed at the interface between plate-like branch of α-Fe phase and aluminum matrix.

Description: Effects of liquid amine-terminated butadiene-acrylonitrile (ATBN) on the properties of bisphenol-A/aniline-based polybenzoxazine (PBA-a) composites were investigated. Liquid ATBN decreased gel time and lowered curing temperature of the benzoxazine resin (BA-a). The PBA-a/ATBN-based self-lubricating composites resulted in substantial enhancement regarding their tribological, mechanical, and thermal properties. The inclusion of the ATBN at 5% by weight was found decreasing the friction coefficient and improved wear resistance of the PBA-a/ATBN composites. Flexural modulus and glass transition temperature of the PBA-a composite samples added the ATBN was constant within the range of 1-5% by weight. A plausible wear mechanism of the composites is proposed based on their worn surface morphologies. Based on the findings in this work, it seems that the obtained PBA-a/ATBN self-lubricating composites would have high potential to be used for bearing materials where low friction coefficient, high wear resistance, and modulus with good thermal property are required.

Description: Aims Wildfires are important disturbances that help to shape the structure and function of forest ecosystems, and arbuscular mycorrhizal fungi (AMF) are key players in the post-fire recovery of soils and understory vegetation. We aimed to investigate the response of AMF communities to wildfire over different timescales. Methods Primer set AMV4.5NF/AMDGR was used to amplify soil 18S rRNA gene fragments for the 454 GS-FLX pyrosequencing platform to examine belowground AMF communities 1 and 11 years following low- and high-intensity wildfires in the Greater Khingan Mountains of China. Results The majority of AMF sequences detected were annotated as Glomeraceae , Claroideoglomeraceae , Diversisporaceae and Acaulosporaceae . Both AMF community composition and alpha-diversity were correlated with herbaceous and shrubby biomass, available phosphorus (AP) and NH 4 + , which were in turn altered by wildfire. AMF community composition, alpha-diversity, and phylogenetic structure were significantly altered 1-year-post-fire. However, AMF communities were indistinguishable from unburned forest soils 11-year-post-fire. Conclusions Our results indicated that AMF communities are resilient to wildfire on decadal timescales. This resilience appears to depend on the post-fire regrowth of understory vegetation and the subsequent recovery of soil chemical properties.

Description: Aims We investigated N 2 O emissions from stems of Fraxinus angustifolia and Fagus sylvatica , hypothesizing that trees emit N 2 O through the stem via diffusion out of the transpiration stream. Methods We used static chambers fixed at different heights of the stem to estimate N 2 O stem effluxes. Chambers were also used for monitoring soil N 2 O emissions. To stimulate soil N 2 O production and stem N 2 O emissions we fertilized the soil. Results Before soil fertilization, stem N 2 O emissions were at most 2 μg N 2 O-N m −2 bark h −1 . After fertilization, stem and soil emissions were linearly correlated; stem emissions decreased linearly with increasing height. Stems of Fagus sylvatica emitted up to 80 μg N 2 O-N m −2 bark h −1 at 20 cm above soil level; at 200 cm, stem N 2 O emissions were below detection limit. Fraxinus angustifolia stem N 2 O emissions reached 35 μg N 2 O-N m −2 bark h −1 after soil fertilization. Conclusions Stem N 2 O emissions in upland trees occur even without aerenchyma, associated with xylem water transport. However, stem N 2 O emissions represented only 1–3 % of total (soil + stem) N 2 O emissions at the forest level. If this holds for other forest ecosystems, stem N 2 O emissions would be a minor pathway of N 2 O loss from terrestrial ecosystems into the atmosphere.

Description: Background and Aims Epichloë endophytes inhabit aerial grass tissues but they can modify belowground processes that might affect host nutrient balance. We aimed to determine the effects of endophyte status (E+=endophyte-infected; E−=non-infected) and three Epichloë morphotypes (M1,M2,M3) on growth and nutrient content of a heterogeneous set of naturally infected asymptomatic plants of Lolium perenne . In addition, plant parameters were compared between asymptomatic E+ and plants with choke disease. Methods A field experiment was conducted with 194 plants obtained from six natural populations (97E+, 97E−). For each E+ plant, the endophyte morphotype it hosted was known. Results Endophyte-infected plants had significantly lower P, Ca, S, B, neutral detergent fiber and lignin contents, and higher Mn and digestibility than E−, independently of plant origin. Biomass production was affected by plant origin but not by endophytes. No effect of Epichloë morphotypes in any parameter was found. However, asymptomatic E+ and choke diseased plants differed in nutrients, fibers, and digestibility. Conclusions An endophyte effect was detected in nutrient and fiber content, in spite of the heterogeneous constitution of the plant and fungal material used. The results obtained indicate that Epichloë may affect above and possibly underground processes involved in nutrient absorption, as well as plant quality, what may potentially affect litter decomposition processes.

Description: Background and aims There is evidence that plant facilitation occurs in heavy metal wastelands, but the extent and mechanisms of facilitation are not known. The copper (Cu) tolerant Elsholtzia splendens is a dominant pioneer species during the secondary succession on copper mine spoils in eastern China. Species appearing later are often associated with patches of E. splendens . We hypothesize that E. splendens facilitates neighbors by modifying local soil properties. Methods We conducted a field study on a heavy metal wasteland with local variation in soil Cu level to investigate the performance of a target species, Commelina communis , growing in open gaps vs. growing with E. splendens . Soil physicochemical and biological properties, biomass, plant interaction intensity as well as heavy metal concentration in C. communis were measured to study the effects of the presence of E. splendens . Results Effects of the presence of E. splendens on C. communis were generally positive, but negative effects were sometimes observed. Positive effects of E. splendens increased with increasing soil Cu level. Soil microbial activity was higher in the presence of E. splendens . Our results are consistent with the hypothesis that facilitation occurred through enrichment of the microbial properties of the soil, especially soil respiration rate and enzyme activity. Conclusions Our study highlights the importance of soil-mediated plant-plant interactions for the establishment of C. communis on heavy metal-contaminated sites. These interactions are important for the restoration of heavy metal wastelands.

Description: The structural properties of lightweight constructions can be adapted to specific local requirements using multi-material designs. Aluminum alloys and carbon fiber-reinforced plastics (CFRP) are materials of great interest requiring suitable joining techniques in order to transfer the advantages of combining the materials to structural benefits. Thus, the research group “Schwarz-Silber” investigates novel concepts to enable frontal aluminum-CFRP joints using transition structures. In the foil concept titanium foils are used as transition elements. Specimens have been produced using three-layer titanium laminates. In tensile tests, three failure locations have been observed: (1) Al-Ti seam, (2) Ti-CFRP hybrid laminate, and (3) CFRP laminate. In this paper, the fracture mechanisms of these failure modes are investigated by analyzing metallographic micrographs and fracture surfaces as well as by correlating load-displacement curves to video imaging of tensile tests. The results show that the cracking of the CFRP layers can be traced back to an assembly error. The laminate character of the titanium part tends to reduce the Al-Ti seam strength. However, two sub-joint tests demonstrate that the Al-Ti seam can endure loads up to 9.5 kN. The ductile failure behavior of the Ti-CFRP hybrid laminates is caused by plastic deformations of the titanium laminate liners.

Description: SnO 2 nanosheets with sizes around 1 μm and thickness around 30 nm have been synthesized by a template-free hydrothermal method. With the addition of urea, SnO 2 hollow microspheres with diameters of about 1 μm and shell thickness of about 200 nm were also prepared. The structures, morphologies, and optical properties of the as-prepared samples were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy and selected area electron diffraction, Raman spectroscopy, and ultraviolet-visible absorption spectrophotometry. The possible mechanisms for the growth of these SnO 2 nanostructures were tentatively proposed based on controlled experiments. Moreover, photocatalytic investigations revealed that the as-prepared SnO 2 samples possessed good photocatalytic activity in the degradation of rhodamine B.

Description: In order to improve the understanding of the hot deformation and dynamic recrystallization (DRX) behaviors of large-scaled AZ80 magnesium alloy fabricated by semi-continuous casting, compression tests were carried out in the temperature range from 250 to 400 °C and strain rate range from 0.001 to 0.1 s −1 on a Gleeble 1500 thermo-mechanical machine. The effects of the temperature and strain rate on the hot deformation behavior have been expressed by means of the conventional hyperbolic sine equation, and the influence of the strain has been incorporated in the equation by considering its effect on different material constants for large-scaled AZ80 magnesium alloy. In addition, the DRX behavior has been discussed. The result shows that the deformation temperature and strain rate exerted remarkable influences on the flow stress. The constitutive equation of large-scaled AZ80 magnesium alloy for hot deformation at steady-state stage (ɛ = 0.5) was \( \dot{\upvarepsilon } = 1.394 \times 10^{12} [\sinh (0.018\upsigma )]^{5.043} \exp ( - 169.610/RT). \) The true stress-true strain curves predicted by the extracted model were in good agreement with the experimental results, thereby confirming the validity of the developed constitutive relation. The DRX kinetic model of large-scaled AZ80 magnesium alloy was established as X d  = 1 − exp[−0.95((ɛ − ɛ c )/ɛ*) 2.4904 ]. The rate of DRX increases with increasing deformation temperature, and high temperature is beneficial for achieving complete DRX in the large-scaled AZ80 magnesium alloy.

Description: For a better understanding of the thermal fatigue behavior in compacted graphite cast iron (CGI), the cyclic thermal shock test is carried out through alternating induction heating and water quenching. The optical and scanning electron microscopy observations are used to examine the cracks and oxidation behavior on the cross section and heating surface of the material specimen, respectively. The results show that the thermal cracks in CGI initiate at the graphite phases mostly, and the multi-sourced thermal cracks would result in stable cracks morphology finally through crack shielding effect. In the oxidation analysis, it is found that the oxidation of graphite is selective, and the graphite is the potential channels for oxygen diffusion from the outside into the matrix, resulting in local oxidation of matrix around graphite and continuous oxygen diffusion paths in the microstructure. Thermal cracks nucleate from the oxidation holes at graphite caused by decarburization, and they prefer to propagate and coalesce by penetrating the oxide bridges.

Description: Air plasma-sprayed Ni-20Cr coating on stainless steel (AISI-304) substrate was re-melted using CO 2 laser to remove the inherent defects, i.e., porosity, splat boundaries, and oxides of air plasma-sprayed coating. The (1) uncoated, (2) air plasma-sprayed, and (3) laser-re-melted specimens were exposed to cyclic oxidation at 900 °C for a hundred cycles run. The oxidation products were characterized using XRD and SEM. Weight changes were determined after every 4th cycle; Uncoated samples showed severe oxidation indicated by substantial weight loss, whereas air plasma-coated samples demonstrated noticeable weight gain. However, oxidation resistance of laser-cladded samples was found to be significantly improved as the samples showed negligible weight change; porosity within the coating was minimized with an improvement in interface quality causing reduction in delamination damage.

Description: In the present study, corrosion inhibition influence of novel cationic surfactant (CS) with imidazole structure (1-methyl-3-octadecane imidazolium hydrogen sulfate) on low carbon steel in 1 M HCl was investigated by implementing weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. Increasing the amount of surfactant adequately leads to an increment of the inhibition efficiency of novel CS. According to the obtained results from EIS measurements, inhibition efficiency was about 34% in the presence of 1 ppm surfactant, increasing to about 96.8% at the 25 ppm (near critical micelle concentration) surfactant concentration. Also the effects of temperature and the synergistic effect between surfactant and NaHSO 4 salt were studied. The inhibition efficiency increased with the increase of NaHSO 4 concentration and reached the maximum value near 0.1 M and experienced a plummet in the temperature range of 30-50 °C. Potentiodynamic polarization measurements revealed that the surfactant acts as mixed-type inhibitors. Results obtained from weight loss, polarization, and impedance measurements are in proper agreement and confirmed the fact that this surfactant is an excellent inhibitor for low carbon steel in 1 M HCl environment. The surface morphology of inhibited and uninhibited metal samples was investigated by atomic force microscope (AFM) and field emission scanning electron microscope (FE-SEM).

Description: The phase transformation temperature of nickel titanium (NiTi) shape memory alloy (SMA), which is commonly used in biomaterial fields, is strongly influenced by aging heat treatments. In this study, we apply a new aging heat treatment under loading conditions to near-equiatomic NiTi SMA wires to investigate its effect on phase transformation temperatures. We determine changes in the phase transformation temperatures via differential scanning calorimetry measurements. We analyze transformation temperatures, hysteresis properties, and enthalpy changes and discuss significant results with the help of micrographs. Moreover, we evaluate our results using two-way analysis of variance, axiomatic design methods, and customary analysis in order to make reliable inferences. We observe a significant difference between first and second heating-cooling cycle results for NiTi SMA samples on the basis of austenitic transformation temperatures. Consequently, we are able to theorize correlations between design parameters and functional requirements.

Description: Background and aims Within the last decades, considerable knowledge has been gained on the impacts of carbonaceous soil additives such as hydrochar (or HTC) and biochar (or pyrochar) on plant growth and various soil properties. However, still little is known about the effects of hydrochar and biochar on soil microorganisms, especially from field studies. Microorganisms are closely linked to nutrient dynamics in soil and therefore are tightly linked to soil fertility. As a consequence, possible changes in the microbial community structure due to HTC/biochar soil application may lead to considerable changes in soil nutrient dynamics. Methods To gain insights into HTC/biochar associated long-term effects on microorganisms, soil samples were taken from a grassland field study 2.6 years (31 months) after its initiation (April 2011), where Miscanthus × giganteus feedstock, HTC and biochar, each mixed with pig slurry had been applied as top-dressing in a randomized block design, next to a slurry-only control ( n  = 4, 16 plots). The samples were analyzed for microbial activity and biomass by substrate induced respiration (SIR). Bacterial and fungal fractions in soil microbial biomass (SMB) were determined using the inhibitors streptomycin and cycloheximide respectively. Results Total SMB in biochar-amended soils was significantly higher compared to all other treatments; fungal biomass was significantly higher compared to feedstock and control treatments. The percentage of bacterial biomass was higher in the feedstock and HTC amended soil, as compared to the control. Additionally, HTC exhibited a significantly higher percentage of fungal biomass compared to the feedstock treatment, indicating a microbial community shift. Conclusion While the uncarbonized feedstock material depleted both total SMB and especially fungi, HTC and biochar did not trigger any adverse long-term effects on SMB. Rather, the observed biochar-induced stimulation of SMB may improve soil aggregation and increase the soil organic carbon content in the long term.

Description: Micromechanical response of silicon carbide particle dispersed Al/Mg/Ti/Cu composite, synthesized by powder metallurgy technique was investigated. A correlation between their microhardness and nanomechanical properties at submicron length scale was established. Hardening effect of SiC particles on the hardness, elastic modulus, recovery index, and plastic energy of the matrices was prominent and may be due to the interactions between geometrically necessary and statistically stored dislocations along with their impediment with dispersoids-matrix interface. The elastic recovery obtained from nanoscratch measurement was also correlated with the recovery parameter, which was derived from the nanoindentation of the composite compacts.

Description: Aims Root angles are widely recognized to play an important role in determining rooting depth and drought tolerance in crop plants. But there has been no report revealing any association between root angle and yield performance under drought conditions in maize. There is also no simple method available to screen root angles. The objectives of this study were to evaluate genetic variation in seminal and nodal root angles in maize in greenhouse condition and their association with drought tolerance in field condition. Methods Eighteen hybrids, of which nine were higher-yielding and nine were lower-yielding under water-stressed condition in field, were evaluated for root angle variation. Root angle was estimated as the distance between the horizontal soil surface line and slope of the root at 2 cm position from root base using a protractor. Results Significant phenotypic variation was observed among hybrids for seminal and nodal root angles and primary root diameter. These root traits showed strong positive correlations with grain yield under drought condition. All the higher-yielding hybrids had steeper root growth angle than the lower-yielding hybrids. A strong correlation between seminal and nodal root angles was observed. A strong correlation was also observed between 5th and 4th node nodal root angles. Conclusion Either seminal or nodal root angle could be used for selection for the improvement drought tolerance. The current screening system for root angle is simple and inexpensive, and could be used for screening a large number of genotypes.

Description: Residual stresses introduced by manufacturing processes such as casting, forming, machining, and welding have harmful effects on the mechanical behavior of the structures. In addition to the residual stresses, weld toe stress concentration can play a determining effect. There are several methods to improve the mechanical properties such as fatigue behavior of the welded structures. In this paper, the effects of ultrasonic peening on the fatigue life of the high-temperature seamless steel pipes, used in the petrochemical environment, have been investigated. These welded pipes are fatigued due to thermal and mechanical loads caused by the cycle of cooling, heating, and internal pressure fluctuations. Residual stress measurements, weld geometry estimation, electrochemical evaluations, and metallography investigations were done as supplementary examinations. Results showed that application of ultrasonic impact treatment has led to increased fatigue life, fatigue strength, and corrosion resistance of A106-B welded steel pipes in petrochemical corrosive environment.

Description: Background and aims We investigated the effects of silicon (Si) on chlorophyll concentration, photosynthesis, leaf chloroplast ultrastructure, and expression of genes involved in photosynthesis to elucidate the mechanisms through which Si mediated alleviation of manganese (Mn) toxicity in rice ( Oryza sativa L.). Methods Rice seedlings were grown hydroponically with normal Mn (6.7 μM) or high Mn (2 mM) concentrations, both with (1.5 mM) and without Si supplementation. Leaf chloroplast ultrastructure was observed by scanning and transmission electron microscopy. Differentially expressed genes relating to photosynthesis were identified by high-throughput sequencing, and their relative expression levels were evaluated by real-time quantitative PCR. Results Chlorophyll and carotenoid concentrations and net photosynthesis decreased with chloroplast degradation under high Mn stress. High Mn concentrations may have inhibited photosynthesis through several mechanisms, including suppressing chlorophyll and ATP synthesis, decreasing light-harvesting processes, impairing photosystem I (PSI) stability and structure, and slowing activity of phosphoribulokinase. Si enhanced Mn tolerance efficiently by increasing chlorophyll concentration, light-use efficiency, and ATP concentration as well as by stabilizing the structure of PSI and promoting CO 2 assimilation. Conclusions Our findings suggest active involvement of Si in Mn detoxification, ranging from physiological responses to gene expression.

Description: Background and aims The importance of the uptake of nitrogen in organic form by plants and mycorrhizal fungi has been demonstrated in various ecosystems including temperate forests. However, in previous experiments, isotopically labeled amino acids were often added to soils in concentrations that may be higher than those normally available to roots and mycorrhizal hyphae in situ, and these high concentrations could contribute to exaggerated uptake. Methods We used an experimental approach in which we added 13 C-labeled and 15 N-labeled whole cells to root-ingrowth cores, allowing proteolytic enzymes to release labeled organic nitrogen at a natural rate, as roots and their associated mycorrhizal fungi grew into the cores. We employed this method in four forest types representing a gradient of soil pH, nitrogen mineralization rate, and mycorrhizal type. Results Intact uptake of organic nitrogen was detected in mycorrhizal roots, and accounted for at least of 1–14 % of labeled nitrogen uptake. Forest types did not differ significantly in the importance of organic uptake. Conclusions The estimates of organic N uptake made here using 13 C-labeled and 15 N-labeled whole cells are less than those reported in other temperate forest studies using isotopically labelled amino acids, and likely represent a minimum estimate of organic N-use. The two approaches each have different assumptions, and when used in tandem should complement one another and provide upper and lower bounds of organic N use by plants.

Description: Aim To investigate how the chemical composition of native organic matter of two contrasting soils varies with inputs of biochar and fresh material (including plant roots) and how these underlying changes influence microbial community structure. Methods Corn stover (CS) and CS-derived biochars produced at 350 °C and 550 °C were applied at a dose of 7.2 t C ha −1 to two contrasting soils—an Alfisol and an Andisol. After 295 days of incubation, two undisturbed subsamples from each pot were taken: (i) in one, lucerne ( Medicago sativa L.) was seeded (plant study, P) and (ii) in the other, the incubation was continued without the plants (respiration study, R); all subsamples were incubated for an additional 215 days. Soils without amendments were used as controls. At the end of the incubation (510 days), their bacterial community profiles were characterised using ARISA and the molecular composition of soil organic matter (SOM) was investigated by pyrolysis-GC/MS. Results There were significant interactions between soil type, study type (P or R) and organic amendment. Organic amendments influenced overall SOM composition with microbial community response being mainly influenced by soil type but also strongly affected by the presence or absence of plants. For a specific soil type, ≥ 40 % of total variation in bacterial community ordination could be explained by the molecular composition of SOM. Conclusions The molecular composition of SOM is proposed as an important factor influencing the microbial response to organic amendments, including biochar.

Description: The present study deals with the static and dynamic microstructural evolution of a high-Mn twinning-induced plasticity steel. Static recrystallization (SRX) is considered through cold rolling followed by annealing with different holding times. Dynamic recrystallization (DRX) was explored by hot compression tests at different temperatures and strain rates. The microstructural observations demonstrated that new grains nucleate at the prior grain boundaries and grain size decreased when cold rolling was followed by annealing. Additionally to the grain size reduction due to the SRX, nucleation sites for DRX increased. It is shown that flow stress level increased as a result of grain refinement caused by static and DRX.

Description: Phase transformation during heating in homogenized Ti-22Al-(27- x )Nb- x Zr ( x  = 0, 1, 6) alloys is monitored by dilatometry, differential scanning calorimetry (DSC), and detailed metallographic examination. Moreover, the dissolution of α 2 into the B 2 /β matrix is investigated and discussed. In Ti-22Al-27Nb alloy, the sequence of phase transformation during heating can be concluded as follows: B 2 /β → O, B 2 /β + α 2  → O, B 2 /β + O→ B 2 /β + O + α 2 , B 2 /β + O + α 2  →  B 2 /β + α 2 , and B 2 /β + α 2  →  B 2 /β. For Ti-22Al-21Nb-6Zr alloy, it is B 2 /β → α 2  + O, O + α 2  +  B 2 /β →  B 2 /β + α2, and then α 2 dissolves into B 2 matrix. There are considerable shifts in the maxima of the transformation rates in B 2 /β + O+α 2  →  B 2 /β + α 2 and B 2 /β + α 2  →  B 2 /β transformed region to the higher temperatures with increasing x value. In the stage of B 2 /β + α 2  →  B 2 /β, there is a deceleration of reduction in α 2 phase with increasing temperature for Ti-22Al-(27- x )Nb- x Zr ( x  = 0, 1, 6) alloys. And for Ti-22Al-21Nb-6Zr, the dissolution rate of α 2 phase is accelerated.

Description: Background and aims The Karoo biomes of South Africa are major feed resources for livestock farming, yet soil nutrient depletion and degradation is a major problem. The objective of this study was to assess impacts of long-term (〉75 years) grazing during spring (SPG), summer (SUG), winter (WG) and exclosure (non-grazed control) treatments on soil nutrients, penetration resistance and infiltration tests. Methods A soil sampling campaign was carried out to collect soil to a depth of 60 cm to analyse bulk density, soil physical and chemical parameters as well as soil compaction and infiltration. Results Generally, grazing treatments reduced soil organic C (SOC) stocks and C:N ratios, and modified soil properties. There was higher SOC stock (0.128 Mg ha −1  yr −1 ) in the exclosure than in the SPG (0.096 Mg ha −1  yr −1 ), SUG (0.099 Mg ha −1  yr −1 ) and WG (0.105 Mg ha −1  yr −1 ). The C:N ratios exhibited similar pattern to that of C. From the grazing treatments, the WG demonstrated 7 to 10 % additional SOC stock over the SPG and SUG, respectively. Conclusions Short period animal exclusion could be an option to be considered to improve plant nutrients in sandy soils of South Africa. However, this may require a policy environment which supports stock exclusion from such areas vulnerable to land degradation, nutrient and C losses by grazing-induced vegetation and landscape changes.

Description: Aims Theoretical and observational studies have suggested that environmental variations would change compositional similarity between plant communities. However, this topic has rarely been examined via experiments involving direct manipulation of resources utilized by plant communities. Methods A 9-year field manipulation experiment was conducted to examine the effects of nitrogen addition and increased water on community similarity between a steppe and an old field in the semiarid region of northern China. Results Over the experimental period, nitrogen addition reduced community similarity between the steppe and the old field, whereas water addition enhanced community similarity. These treatment effects were closely related to changes in diversity characteristics as well as abundance of functional groups and dominant species of plant communities. Conclusions These results highlight the importance of resource availability in regulating the trajectory of ecosystem succession, and suggest that the increase in atmospheric nitrogen deposition in northern China will contribute to divergence between the steppe and the old field, whereas the increase in growing-season precipitation may encourage convergence between the two grasslands with respect to species composition during succession. Thus the decrease in community similarity caused by nitrogen enrichment may be counteracted, at least partially, by precipitation increase under changing atmosphere and climate.

Description: Background and Aims The Canterbury Plains of the South Island, New Zealand are being converted to intensive dairy farming; native vegetation now occupies 〈 0.5 % of the area. Reintroducing native species into nutrient-rich systems could provide economic, environmental and ecological benefits. However, native species are adapted to low nitrogen (N) environments. We aimed to determine the growth and N-uptake response of selected native species to elevated soil N loadings and elucidate the effect of these plants on the N speciation in soil. Methods Plant growth, N-uptake, and N speciation in rhizosphere soil of selected native species and Lolium perenne (ryegrass, as reference) were measured in greenhouse and field trials. Results At restoration sites, several native species had similar foliar N concentrations to ryegrass. Deciduous (and N-fixing) species had highest concentrations. There was significant inter-species variation in soil mineral N concentrations in native plant rhizospheres, differing substantially to the ryegrass root-zone. Pot trials revealed that native species tolerated high N-loadings, although there was a negligible growth response. Among the native plants, monocot species assimilated most N. However, total N assimilation by ryegrass would exceed native species at field productivity rates. Conclusions Selected native plant species could contribute to the sustainable management of N in intensive agricultural landscapes.

Description: Aims Belowground plant biomass accumulation is facilitated by the photosynthetic capacity of the canopy. We investigated the hypothesis that a precise monitoring of leaf area development provides the potential to extrapolate to belowground biomass development and to assess the timing and the degree of an inhibition of the belowground biomass generation. Sugar beet seedlings and the retarding effect of beet cyst nematodes (BCN) were used as a model system. Methods Thirty BCN infested plants and 30 non-infested plants were grown in three litre pots under greenhouse conditions. Top-view images of the plant leaf canopy were taken every two or three days. Leaf and beet biomass were measured at three different dates (32, 41 and 70 days after sowing (das)) by harvesting the plants. Results Leaf dry weight and beet fresh weight were strongly correlated 32 and 41 das. The canopy area calculated was highly correlated with both leaf and beet biomass at 32 and 41 das, and was significantly reduced in the nematode infested plants from 22 to 60 das. Conclusions Our results show the ability of canopy-imaging based approaches to evaluate plant biomass during the early developmental stages and to detect a delay in plant development caused by a below-ground stress such as nematodes.

Description: The scanning vibrating electrode technique (SVET) has been used to study the in-situ corrosion phenomena on AA2024T3 aluminum alloy. Three distinct sequential stages of corrosion attack, with time, on the alloy have been revealed (0-75, 75-180 min, and after 180 min). The increase and decrease in the intensity of the anodic activities at the surface of the alloy, which give a corresponding increase and decrease in the net current density values, with time, are responsible for the stepwise changes in the corrosion stages. The work also revealed mild etch-like attack regions on the surface of the alloy after the immersion test.

Description: The injection-molded metallic glass soft magnet is prepared from the powder of melt-spun ribbon of Fe 36 Co 36 B 20 Si 4 Nb 4 glassy alloy and Nylon 6,6 of wt.% from 5 to 20 via the polymer injection molding technology. The product is characterized by the SEM, mechanical, and magnetic test. The results indicate that this type of materials has comparable mechanical properties and morphological feature with the conventional injection-molded NdFeB magnet and exhibits excellent soft magnetic behaviors. The magnetic properties of the injected magnets are compared with the raw metallic glass, solvent-casted resin bonding magnets, and thermal-treated magnets to confirm that the processing temperature of Nylon injection does not affect the magnetism. The injection technology is a practical processing method to be applied on the metallic glass for potential usage.

Description: Static recrystallization (SRX) behavior of a nitrogen-alloyed ultralow carbon austenitic stainless steel was studied on a Gleeble-1500D thermal-simulator by two-step hot compression tests. Deformation temperatures of 1173-1473 K, deformation strains of 0.051-0.105, strain rates of 0.01-1 s −1 , and inter-step times of 1-100 s were selected as the deformation conditions to investigate the effects of deformation parameters on SRX behavior. Besides, the influences of initial grain size on SRX behavior were studied. The results show that deformation temperature and strain have greater influences on SRX behavior than strain rate and initial grain size. Based on true stress-true strain data obtained from the experiments, SRX kinetics equation was determined. In addition, the established SRX kinetics equation was introduced into finite element simulation software DEFORM-3D to perform the two-step compression deformation. Furthermore, SRX kinetics equation was modified for improving the accuracy of finite element simulation, and the modified SRX kinetics equation was verified.

Description: In this work, effects of pH value on the electrochemical and stress corrosion cracking (SCC) behavior of X70 pipeline steel in the dilute bicarbonate solutions were investigated using electrochemical measurements, slow strain rate tensile tests and surface analysis techniques. Decrease of the solution pH from 6.8 to 6.0 promotes the anodic dissolution and cathodic reduction simultaneously. Further decrease of the pH value mainly accelerates the cathodic reduction of X70 pipeline steel. As a result, when the solution pH decreases form 6.8 to 5.5, SCC susceptibility decreases because of the enhancement of the anodic dissolution. When the solution pH decreases from 5.5 to 4.0, SCC susceptibility increases gradually because of the acceleration of cathodic reactions.

Description: On the basis of hot rolling practice, the effects of thermomechanical control process parameters on the evolution of austenite grain size before the deformation at non-recrystallization zone were investigated in detail. The inflections in the strain hardening rate versus true stress curves show that the dynamic recrystallization (DRX) has initiated for different deformation conditions studied in the present work. But the volume fractions of the equiaxed grains in the specimens which were immediately water quenched to room temperature after deformation are different from each other. Moreover, the main refinement mechanisms for different deformation conditions have been differentiated. It is interesting to note that the austenite grain size can be refined significantly with increasing the strain from 0.0 to 0.5 for different deformation temperatures. However, when the strain increases to 0.8, the austenite grain size cannot be further refined for the higher deformation temperature range, while the austenite grain size can be further refined for the lower deformation temperature range. In addition, the effect of strain rate on the austenite grain refinement is vigorous for the higher deformation temperatures. Moreover, the empirical equation to estimate the austenite grain size for different deformation parameters was established.

Description: Nanosized In 2 O 3 powders with different particle sizes were prepared by the microemulsion synthetic method. The effects of particle size on the gas-sensing and catalytic properties of the as-prepared In 2 O 3 were investigated. Reductions in particle size to nanometer levels improved the sensitivity and catalytic activity of In 2 O 3 to i -C 4 H 10 and C 2 H 5 OH. The sensitivity of nanosized In 2 O 3 (〈42 nm) sensors to i -C 4 H 10 , H 2 and C 2 H 5 OH was 2-4 times higher than that of chemically precipitated In 2 O 3 (130 nm) sensor. A nearly linear relationship was observed between the catalytic activity and specific surface area of In 2 O 3 for the oxidation of i -C 4 H 10 and C 2 H 5 OH at 275 °C. The relationship between gas sensitivity and catalytic activity was further discussed. The results of this work reveal that catalytic activity plays a key role in enhancing the sensitivity of gas-sensing materials.

Description: Backgrounds and aims Scotch broom is an N-fixing invasive species that has high potential to alter soil properties. We compared soil from areas of Scotch broom invasion with nearby areas that had no evidence of invasion to assess the influence of broom on soil P fractions and other chemical properties. Methods The study was conducted at two contrasting Douglas-fir sites in Oregon (OR) and Washington (WA), USA with broom invasion for 10 years. We used the Hedley sequential fractionation procedure to assess effects of Scotch broom invasion on P pools of varying bioavailability, and also measured total C, N and extractable nutrient cations. Results Total soil C and N were significantly higher with broom present at the fine-textured OR site, but there was no effect at the coarse-textured WA site. There was no difference in labile-P measures between the presence and absence of Scotch broom at either site, but there were notable reductions (25–30 %) in the intermediately-available P fraction when broom was present. Extractable nutrient cations (notably K) were lower in the presence of broom at both sites, with the effects most pronounced at the fine-textured OR site. Conclusions Lasting effects of Scotch broom invasion are likely to be associated with variable changes in soil C, N, and decreases in extractable nutrients and available P. These changes, and other documented effects of Scotch broom on soil, are likely to have lasting effects on Douglas-fir growth after Scotch broom removal that will vary depending soil nutrient status at a given site.

Description: Aims Sorghum ( Sorghum bicolor ) roots release biological nitrification inhibitors (BNIs) to suppress soil nitrification. Presence of NH 4 + in the rhizosphere stimulates BNIs release and it is hypothesized to be functionally associated with plasma membrane (PM) H + -ATPase activity. However, whether the H + -ATPase is regulated at the transcriptional level, and if so, which isoforms of the H + -ATPases are involved in BNIs release are not known. Also, it is not clear whether the stimulation on BNIs release from roots is due to NH 4 + uptake or its assimilation, which are addressed in this study. Methods Root exudates from intact sorghum plants were collected using aerated solutions of NH 4 + or methyl-ammonium (MeA); and the BNI-activity release was determined. PM vesicles were isolated from fresh roots using a two-phase partitioning system; and the hydrolytic H + -ATPase activity was determined. All genes encoding PM H + -ATPases were searched in sorghum genome, and their expression in response to NH 4 + or MeA were analyzed by quantitative RT-PCR in sorghum roots. Results BNIs release and PM H + -ATPase activity increased with NH 4 + concentration (≤1.0 mM) in the root-exudate collection solutions, but at higher concentrations, it did not respond further or declined in case of the PM H + -ATPase activity. Twelve PM H + -ATPase genes were identified in sorghum genome; and these isoforms were designated SbA1 to SbA12 . Five H + -ATPase genes were stimulated by NH 4 + in the rhizosphere, and have similar expression pattern, which is consistent with the variation in H + -ATPase activity. MeA, a non-metabolizable analogue of NH 4 + , had no significant effects on BNIs release, H + -ATPase activity, or expression of the H + -ATPase genes. Conclusions Our results suggest that the functional link between PM H + -ATPase activity and BNIs release is evident only at NH 4 + levels of ≤1.0 mM in the rhizosphere. The variation in PM H + -ATPase activity by NH 4 + is due to transcriptional regulation of five isoforms of the H + -ATPases. The stimulatory effect of NH 4 + on BNIs release is functionally associated with NH 4 + assimilation and not just with NH 4 + uptake alone.

Description: Aims We compared elemental sulphur (ES) and sulphate fertilisers in terms of yield and S uptake. Methods Two consecutive canola crops were grown on 35 S-labelled soil amended with ammonium sulphate, ES-bentonite pastilles (90 % ES), or S-fortified ammonium phosphate (NP) fertilisers containing both sulphate-S and ES (5–8 % ES). The shoot yield, S concentration and specific activity of S in the shoot were determined. Results In the first crop, the yield was significantly lower in the control (without added ES) and ES pastille treatments than in the other treatments. Sulphur uptake was highly correlated with the added sulphate rate. In the second crop, the yield and S uptake was highest for the S-fortified NP fertilizers. The contribution of ES to the S uptake was circa 20 % in the first crop and 43 % in the second crop for the S-fortified NP fertilisers, but was negligible for the ES pastilles. Modelling indicated an oxidation rate of 0.6 − 0.7 % per day for the S-fortified NP fertilisers and 0.03 % per day for the ES pastilles. Conclusions The contribution of ES pastilles to S uptake was negligible in both crops. In contrast, S-fortified NP fertilisers showed a significant contribution of ES and higher S availability than sulphate-only fertiliser in the second crop.

Description: Aim Desert herbs, a crucial component of desert ecosystems, are sensitive to water and nutrient availability and therefore to environmental change. We aimed to determine element concentrations in desert herbs and their relationships with life form, taxonomy, climate, and soil environment. Methods We measured concentrations of 11 elements in shoots and roots of 26 dominant desert herb species from 45 sites in a temperate desert. Results Shoots of desert herbs had greater concentrations of elements related to photosynthesis and water use efficiency (N, P, Mg, K) than roots. Concentrations of these elements (except N and P) were also greater in annual herbs than in perennial herbs. Greater Mg, K, and Na concentrations were observed in shoots of Chenopodiaceae (mostly C 4 species) than in Poaceae (mostly C 3 species). Soil properties and taxonomy explained 3.6–26 % and 2.8–24 % of the variation in shoot element concentrations, respectively, whereas climate factors explained only 0.05–6.5 % of the variation. Conclusions Water and nutrient availability, which are affected by environmental change, influence concentrations of mineral elements in desert plants and their biogeochemical cycles in desert ecosystems.

Description: The evolution of micro-texture below the machined surface is computationally modeled and experimentally verified. The orientation distribution functions of the grains below the surface were represented in spectral form. The microstructure descriptor coefficients were derived, and their change with respect to the change in the cutting feed rate was computationally calculated and monitored. Micro-texture experimental observations conducted by electron back-scatter diffraction technique verify the modeling outputs. Continuation of changing the process parameter was done by finite element method, and the evolution in texture was investigated by computational modeling. The process path function which correlates micro-texture evolution and cutting feed rate, was obtained by applying the principle of orientation conservation in the Euler space. As a result of the major finding of this work, i.e., derivation of process path functions, the evolution of texture as a function of the material feed rate is numerically determined without any need to texture modeling or finite element analyses.

Description: The life cycle requirements for advanced Ni alloys are very demanding and can be on the order of several hundreds of thousands of hours. Results are presented on a wrought Ni-based superalloy designed within the nominal chemistry range of Haynes 282 with a fixed amount of γ′ strengthening phase, and either low Al or Ti (within the alloy specification) to give different ratios of Ti/Al, and thus, different γ′ misfit with the γ matrix. The effect that these changes have on the γ′ misfit and its relevance to long-term microstructural stability is being explored both experimentally as well as with computational modeling with results through almost 10,000 h. The basics of the modeling approach are presented as are the procedures for evaluating the γ′ volume fractions from transmission electron microscopy (TEM) micrographs and correcting these volume fractions for truncation error due to TEM foil thickness. Results on each alloy formulation are compared and discussed with respect to possible γ′ coarsening due to the different Ti/Al ratio and what this might mean for the long-term stability of the alloy.

Description: Background and aims In order to analyse root system architectures (RSAs) from captured images, a variety of manual (e.g. Data Analysis of Root Tracings, DART), semi-automated and fully automated software packages have been developed. These tools offer complementary approaches to study RSAs and the use of the Root System Markup Language (RSML) to store RSA data makes the comparison of measurements obtained with different (semi-) automated root imaging platforms easier. The throughput of the data analysis process using exported RSA data, however, should benefit greatly from batch analysis in a generic data analysis environment (R software). Methods We developed an R package (archiDART) with five functions. It computes global RSA traits, root growth rates, root growth directions and trajectories, and lateral root distribution from DART-generated and/or RSML files. It also has specific plotting functions designed to visualise the dynamics of root system growth. Results The results demonstrated the ability of the package’s functions to compute relevant traits for three contrasted RSAs ( Brachypodium distachyon [L.] P. Beauv., Hevea brasiliensis Müll. Arg. and Solanum lycopersicum L.). Conclusions This work extends the DART software package and other image analysis tools supporting the RSML format, enabling users to easily calculate a number of RSA traits in a generic data analysis environment.

Description: Aims Little is known about why Dicranopteris dichotoma can succeed in a nutrient-limited environment. This study investigated the stoichiometric mechanisms of D. dichotoma growth and resistance to nutrient limitation in the red soil hilly region of China. Methods We examined D. dichotoma growth, soil nutrients, and stoichiometric variables in the early ecological restoration stage and across the ecological restoration chronosequence. Results Most of the D. dichotoma growth factors rapidly increased with the arbor-bush-herb mixed plantation and maintained a high level. Soil P was a main factor influencing D. dichotoma growth across the ecological restoration chronosequence, whereas its role is unclear in the early ecological restoration stage. D. dichotoma demanded low C and P and possessed high N and P utilization rates, and N and P distribution was ranked as leaf 〉 root and rhizome 〉 stem. The stoichiometry of D. dichotoma is a relatively weak stoichiometric homeostasis across the whole ecological restoration chronosequence with relatively strong stoichiometric homeostasis in the early ecological restoration stage. Conclusions Stoichiometry can be used to explore the underlying mechanisms that allow D. dichotoma to succeed to a great extent. D. dichotoma can play an important role in ecological restoration, and microtopography, especially valleys, should be created to trigger the succession of D. dichotoma in the red soil hilly region of China.

Description: Background Bacterivores, mostly represented by protists and nematodes, are a key component of soil biodiversity involved in soil fertility and plant productivity. In the current context of global change and soil biodiversity erosion, it becomes urgent to suitably recognize and quantify their ecological importance in ecosystem functioning. Scope Using meta-analysis tools, we aimed at providing a quantitative synthesis of the ecological importance of soil bacterivores on ecosystem functions. We also intended to produce an overview of the ecological factors that are expected to drive the magnitude of bacterivore effects on ecosystem functions. Conclusions Bacterivores in soil contributed significantly to numerous key ecosystem functions. We propose a new theoretical framework based on ecological stoichiometry stressing the role of C:N:P ratios in soil, microbial and plant biomass as important parameters driving bacterivore-effects on soil N and P availability for plants, immobilization of N and P in the bacterial biomass, and plant responses in nutrition and growth.

Description: Aims This study evaluated a framework for modelling the continuous exchange of carbon (C) between the atmosphere, plants, humus, and microorganisms, proposing a plant C model coupled to MOMOS, an existing microbial C model. Methods C data were collected on low fertility cereal-legume cropping systems. Plant C and microbial C were modelled simultaneously and the growth parameters of plants and nitrogen-fixing microorganisms were fitted to the data. Results All C exchanges were successfully predicted using the same weather correction for plant and microbial processes. Most of the photosynthetic production was allocated to the roots, reducing yields. The C losses were found modelled mainly by root respiration for cereals, probably as an energy source for nutrient explorings, and by root mortality for legumes as a growth source for decomposers and symbiotic nodules. The effect of root-nodule activity on shoot growth was found non-linear. The system was modelled as a sink of 4.2 Mg C ha -1 year −1 in the soil’s labile C reserve. Conclusions This paper coordinates theoretical bases for modelling the processes regulating plant productivity associated with plant C losses. The tool appears to be robust and is now available for calculating the essential parameters of agro-ecology and climate change.

Description: The numerical simulation of tensile fracture behavior on Al-Cu alloy friction stir-welded joint was performed with the Gurson-Tvergaard-Needleman (GTN) damage model. The parameters of the GTN model were studied in each region of the friction stir-welded joint by means of inverse identification. Based on the obtained parameters, the finite element model of the welded joint was built to predict the fracture behavior and tension properties. Good agreement can be found between the numerical and experimental results in the location of the tensile fracture and the mechanical properties.

Description: Aims Both aluminum (Al) toxicity and phosphorus (P) deficiency are limiting factors of crop production on acid soils. Although Al-P interaction has been extensively studied, the results are controversial. The aim of this study is to investigate the effect of in planta P on Al-induced inhibition of root elongation in wheat ( Triticum aestivum L .). Methods Roots of wheat (cv. Atlas 66) with different internal P concentrations were prepared by two methods; split-root and re-rooting in a hydroponic solution using three different P levels (0, 25 and 250 μM) to avoid direct precipitation of Al-P in the solution. Al toxicity was evaluated by root elongation inhibition and callose induction. The Al and P concentrations in the root tips were also compared among different treatments. Results Both split-root and re-rooting methods generated roots with different P concentrations in the tips when exposed to different P levels. Lower P in the root tips resulted in less Al-induced inhibition of the root elongation, less callose content and less Al accumulation, while higher root P caused a higher Al-induced inhibition of the root elongation, increased callose content and Al accumulation in the root tips. Furthermore, Al in the root cell sap was not altered by different P concentrations, but Al in the root cell wall was increased with increasing in planta P concentrations. Conclusions Al toxicity in wheat is associated with P in the root cell wall; lower root P enhanced Al tolerance, while higher root P aggravated Al toxicity in wheat.

Description: Background and aims Biochar additions may have positive impacts on phosphorus (P) availability to plants and cause down-regulation of genes associated with P starvation. Various alkaline-extracted humic substances products (HSP) also induce partial relief in plants from P starvation and, moreover, cause an increase in total cell phosphate, ATP and glucose-6-phosphate levels. As many biochars contain substances similar in structure and functioning to HSP, our goal was to examine if such products extracted from biochar (B-HSP) could affect plant responses to initial P concentration (Pi) under Pi sufficient and starvation conditions. Methods We examined the impact of B-HSP in the growing media of Arabidopsis seedlings on root hair development (length and density) in sterile systems, and evaluated whether nutrient complexation with B-HSP could account for observed differences. Results Root hair length was significantly lower in B-HSP amended Pi-sufficient growing media, and root hair density was significantly lower in both B-HSP amended Pi sufficient and starvation regimes as compared with non-amended treatments. The differences did not result from either primary (P source) or secondary (increased P availability) nutritional effects. Conclusions B-HSP appears to cause a change in plant perception of P nutrition. This may be another means by which biochar impacts growing plants.