Carbon Grains Research Articles

Effect of Grain Size on Change in Surface Roughness of Carbon Steels Through Polishing Processes

A mirror-like reflecting surface is an important characteristic in many industrial metallic parts. Polishing is done to form a mirror surface on metals. However, the effect of the grain size of metals on surface roughness through polishing processes is not clear. Specifically, mirror surface formation of ultrafine grained materials is still unknown. Ultrafine grained steels and coarse grained steels with 0.02, 0.10, and 0.60 wt% carbon contents were prepared by warm caliber rolling and annealing. Average grain sizes were 1–2 μm and 4–40 μm. The changes in surface roughness, Sa, were measured with an atomic force microscope (AFM) via eight polishing steps, using emery papers of type #600, #1000, #1500, #2000, #2500, #4000, and free abrasive grains of 3 μm and 1 μm diamond. As the polishing process progressed, the surface unevenness was removed and the surface roughness, Sa, decreased in all steels. The differences of Sa at each polishing step were analyzed from the point of carbon content, Vickers hardness, and grain size. Carbon contents and Vickers hardness have little effect on Sa. However, grain size has a considerable effect on Sa in all steels. Ultrafine grained steels have smaller Sa in all polishing steps in all steels. This is because ultrafine grained steels have very small work hardening rate. After final polishing, Sa is 2.5–3.6 nm in coarse grained steels and 2.0–2.6 nm in ultrafine grained steels. To obtain a mirror surface with smaller Sa, grain size control is important.

Examination of SWMC applying method by spray coating method for PEFC

A popularization of Polymer Electrolyte Fuel Cell (PEFC) is necessary to realize ahydorgensociety. However, the manufacturing cost is still expensive, and it is required to reduce the manufacturing cost for further spread. In our laboratory, we have been developing 3D catalyst layers using ink-jet printers (IJP) and self-water management catalyst layers (SWMC) by adding carbon grains in order to reduce the amount of platinum catalysts used while maintaining the power generation performance. The IJP method can form a catalyst layer with a three-dimensional structure, but its disadvantage is that it cannot coat our proposed SWMC, due to the long coating time and small nozzle diameter. Therefore, in this study, we investigated the possibility of producing SWMC by the spray coating method in order to shorten the coating time and enable the application of carbon additives. As a result, Although it was confirmed that the spray coating method was able to disperse and apply the added carbon grains, the polarization resistance was worse than that of the IJP method. The polarization resistance of the catalyst layer with spherical graphite was hardly different with that of the standard catalyst layer, consequently it was confirmed its effectivness. On the other hand, graphite rubbish increased polarization resistance drastically by damaging the polymer membrane during the spray application process, inducing cross leakage.

Searching For the t=0 of Planetary System Formation

The composition of bodies in the solar system points to strong gradients in the volatile content within solid bodies hinting at the presence of gas-ice transitions across sublimation fronts in the young formative stages when the gas-rich disk was present. Terrestrial worlds are constructed out of the disk solids which are primarily silicate and water, but might also contain a significant fraction of organic material. These refractory organics are the source of carbon to Earth-like worlds, but have the potential to be destroyed if temperatures exceed 300-500 K (depending on pressure). These temperatures are most readily prevalent during the early stages of planetary system formation where the seeds of terrestrial worlds are potentially assembled. Here we present an ongoing observational search for refractory carbon grain destruction. We also discuss the implications on the overall gas phase chemistry within sublimation zones and on the ultimate composition of planetary bodies forming from available materials.

Effects of bottom trawling on trace metal contamination of sediments along the submarine canyons of the Gulf of Palermo (southwestern Mediterranean)

Submarine canyons are preferential pathways for transport of particulate matter and contaminants from the shelf to the deep sea. The Gulf of Palermo continental margin has a very narrow shelf (about 2–3 km wide on average) and is incised by several submarine canyons that favour shelf-slope sediment transfer. A sediment core collected on the outer shelf and six sediment cores taken at different depths along the Oreto, Eleuterio and Anerella submarine canyons were analysed to study the transfer and historical record of trace metal contamination in the Gulf of Palermo continental margin. Trace metals, major elements, organic carbon and sediment grain size were analysed in these cores, which were dated with 210Pb to assess their historical compositional evolution since the late 19th century. Hg, Pb, Cu, Zn and Cd content increased until the 1970s and 1980s, associated with the increase in urbanization and industrial activities in the Palermo area, and Hg was the contaminant that reached the highest enrichments. However, the increasing trend of these metals contamination was reversed in the 1970s and 1980s, coinciding with drastic changes in the terrigenous content and grain size of sediments in the canyon axes. These changes occurred when bottom trawling fleets expanded to deeper fishing grounds equipped with powerful trawlers around the Gulf of Palermo canyon heads and flanks and along the Oreto canyon axis. Bottom trawlers have resuspended large amounts of sediment, which have been transferred into the canyons since the 1970s and 1980s and have thus increased sediment accumulation rates. This resuspended sediment has been mixing with the sediment transferred and accumulated along the canyons, diluting and reducing its trace metal contamination levels since the expansion of the bottom trawling fleets.

The Control of Diagenesis and Mineral Assemblages on Brittleness of Mudstones

The variation in mineral composition will affect the rock brittleness, thus the change of mineral assemblages during diagenesis has a potential control on the brittleness of mudstones. In this study, thin section, X-ray diffraction (XRD), and Scanning Electron Microscope (SEM) analyses were used to investigate compositional and microscopic features of mudstones. With the enhancement of diagenesis, three mineral assemblages were divided due to the diagenetic evolution of minerals. Quartz, feldspar, dolomite, chlorite, and illite were regarded as brittle minerals and (quartz + feldspar + dolomite + illite + chlorite)/(detrital mineral + carbonate + clay mineral) was defined as the brittleness evaluation index The mudstone brittleness changed slightly during early diagenesis but increased gradually with enhancement of diagenesis in the late diagenesis stage. Quartz and feldspar were scattered above the clay matrix and the contact of grains was limited, therefore, the contribution of detrital minerals to the brittleness was affected by the properties of clay minerals. The diagenetic transformation of clay minerals resulted in the reduction of ductile components (smectite/I-Sm and kaolinite) and increase of brittle components (illite and chlorite), leading to the enhancement of integral rigidity of the mudstones. Meanwhile, the improved crystallization of carbonate in late diagenesis stage enlarged the carbonate grains which resulted in rigid contact between grains. These results highlighted the influence of diagenesis on mudstone brittleness. Therefore, for evaluation of mudstone brittleness, attention should be paid to the diagenesis process besides mineral composition.

How delaying post-silking senescence in lower leaves of maize plants increases carbon and nitrogen accumulation and grain yield

Planting maize at high densities leads to early leaf senescence, and the resulting reduction in the number of lower leaves affects the plant’s root function and lowers its grain yield. However, the nature of the process by which lower leaf senescence affects biomass accumulation and grain yield formation in maize is not clear. This study aimed to shed light on how these factors are related by investigating the effects of the plant growth regulator 6-benzyladenine (6-BA) on the senescence of lower leaves of maize plants. In two maize cultivars planted at densities of 67,500 (low density, LD) and 90,000 (high density, HD) plants ha−1, plants treated with 6-BA maintained a high green leaf area index (LAI) longer than control (CK) plants, enabling them to maintain a higher photosynthetic rate for a longer period of time and produce more biomass before reaching physiological maturity. Spraying the lower leaves of maize plants with a 6-BA solution increased the distribution of 13C-photosynthates to their roots, lower leaves and bracts, a result that can be ascribed to a decreased retention of 13C-photosynthates in the stem and grain. In both seasons of the experiment, maize plants treated with 6-BA accumulated more N in grain and maintained a higher N content in roots and leaves, especially in lower leaves, than CK. Increased C assimilation in the lower leaves may explain why N uptake in plants subjected to the 6-BA treatment exceeded that in CK plants and why both photosynthesis rate and dry matter accumulation were maintained throughout grain filling. Our results suggest that a suitable distribution of C and N in leaves post-silking may maintain plant root function, increase N use efficiency, maximize the duration of high LAI, and increase grain yield.

How do carbonate factories influence carbonate platform morphology? Exploring production−transport interactions with numerical forward modelling

AbstractUnderstanding how carbonate factories influence platform evolution is either based on qualitative conceptual models or quantitative numerical stratigraphic forward models. This study establishes new production depth profiles for four Cenozoic carbonate factories and uses two‐dimensional stratigraphic forward models to explore how interactions between sediment production and transport within carbonate systems influence carbonate platform development. Newly established production/depth profiles are used to model photozoan and heterozoan carbonate grain associations, and the associated carbonate producing factories, and results are compared with well‐studied outcrop successions. Sediment production from photozoan and heterozoan grain associations is also equalized, so that the total sediment production is the same but the depth/production profiles retain their distinctly different form. Thus, the effect of the different production profiles can be assessed. Ramps form when sediment diffusional transport rates are high relative to production rates and flat‐top steep‐margin platforms form when sediment diffusional transport rates are low relative to production rates, whether they are photozoan or heterozoan grain associations. The control exerted by sediment production and transport is expressed as a sediment transport–production ratio where transport ratio is a diffusional sediment transport in two‐dimensions and production ratio is the total sediment production rate which is the product of a production profile that varies in depth and laterally. The transport–production ratio is a key control on the evolution and geometry of carbonate platforms. This is the case with different production profiles (both euphotic and oligophotic) and in mixed grain‐size and mixed transport‐rate systems. Carbonate producing factories significantly influence the rate of sediment production, the depth distribution of sediment production (production profiles), as well as the type of grain sizes produced (influencing resistance to erosion). Thus, different types of carbonate grain associations, and the associated carbonate producing factories, can produce the critical differences between carbonate platform geometries.

The production of carbon electrodes from lignocellulosic biomass of areca midrib through a chemical activation process for supercapacitor cells application

ABSTRACT Lignocellulosic biomass can be used as a suitable basic material for producing activated carbon for use as a supercapacitor cell electrode, due to the high specific surface area, adjustable pore structure, chemical stability, electrical conductivity, and environmentally friendly. Lignocellulosic biomass of areca midrib (AM) is the first biomass to be used as a carbon electrode of a supercapacitor cell carbon without an adhesive material. AM is processed into self-adhesive carbon grains (SACG). Furthermore, SACG is chemically activated with potassium hydroxide (KOH) activator with varying concentrations 0.1 M, 0.2 M, and 0.3 M for get green monolith, before carbonization with N2 gas at 600°C and physical activation with CO2 gas at 700°C to produce carbon monolith electrodes for supercapacitor applications. X-ray diffraction and N2 isothermal methods to determine physical properties of carbon electrodes, while cyclic voltammetry method to determine electrochemical properties of supercapacitor cells. The results of the microstructure analysis showed the Areca carbon midrib electrode has a semicrystalline structure, indicated by the presence of (002) and (100) hkl planes at an angle of 2θ about 24° and 44°, while the highest heap height (Lc) value was produced at a concentration of 0.2 M (carbon electrodes AM-02). The results of isothermal gas N2 and electrochemical properties analysis show that carbon electrodes AM-02 have the highest specific surface area (SSA) and specific capacitance (Csp) of 654.729 m2/g and 142 F/g, respectively. Based on research results, it was shown that the AM-02 had a better potential as an energy storage device for supercapacitor applications than the AM-01 and AM-03 samples.

Soil Organic Matter Fractions and Enzymes Activities under No-tillage System: Effects of Organomineral and Mineral Fertilizer with Humic Substances

ABSTRACT The use of organomineral fertilizer can promote increments of organic matter and affect the enzymatic activity of the soil. The objective of this research was to evaluate the effect of organomineral and mineral fertilizer with humic substances on soil organic matter fractions and enzymes activities. The study was set up in a Xanthic Ferrasol, in the Cerrado region, Brazil. Treatments consisted of two fertilizers and four rates of P fertilizer. The following fertilizers were studied: mineral fertilizer enriched with humic substances (03% of N, 25% of P2O5, 08% of K2O, with 1% humic substance); and granulated organomineral produced from poultry litter and mineral fertilizer (MAP – mono-ammonium phosphate, with 26.6% of P2O5 and 18.2% of organic carbon). Five rates of P were also evaluated (0, 20, 40, 60, and 80 kg ha−1 of P2O5). The crop production, soil organic matter fraction and enzymes were assessed in the 2014/2015 and 2015/2016 growing seasons. Contents of the total organic carbon, particulate organic carbon, humic acid, fulvic acid, and maize and soybean grain yield were positively influenced by the fertilizer application. Fertilization treatments did not affect the enzymes activities, but they showed positive correlations with particulate organic carbon.

Effect of different nitrogen management options on nutrient uptake, biomass carbon sequestration and grain yield of maize-wheat system in reclaimed sodic soil

A field experiment was conducted to study the impact of different nitrogen (N) management options on the nutrient uptake, biomass carbon sequestration and yield of maize-wheat system in reclaimed sodic soil of the Trans-Gangetic Plains of India. Seven N management treatments – T1 [100% recommended dose of N (RDN) + 10 t ha−1 farm yard manure (FYM)]; T2 (100% RDN); T3 (75% RDN + 25% N through FYM); T4 (50% RDN + 50% N through FYM), T5 (25% N through FYM); T6 (50% N through FYM) and T7 (control; No N) were tested. Maximum nutrient uptake, biomass carbon sequestration and yield of maize-wheat system were reported in 100% RDN + FYM treatment. Total biomass carbon sequestration and yield were significantly higher by 47.8% and 30.4%, respectively in 100% RDN + FYM as compared to control treatment. However, 100% RDN + FYM was statistically at par with the 100% RDN, 75% RDN + 25% N through FYM, and 50% RDN + 50% N through FYM treatments for both these variables. Nutrient uptake, total carbon sequestration and yield in 50% N through FYM and 25% N through FYM were insignificantly higher as compared to control, but significantly lower than the 100% RDN treatment. Results indicated that the addition of FYM with RDN increased the nutrient uptake, biomass carbon sequestration and yield of maize-wheat system. Higher biomass carbon sequestration and sustainability to maize and wheat cropping system is need of the hour in the study area.

Carbohydrate Assimilation and Translocation Regulate Grain Yield Formation in Wheat Crops (Triticum aestivum L.) under Post-Flowering Waterlogging

In a two-year field study, we quantified the impact of post-flowering soil waterlogging on carbon assimilation and grain yield formation in wheat crops. At anthesis, wheat cultivars YangMai 18 (YM18) and YanNong 19 (YN19) were waterlogged for different durations, i.e., 0 (W0), 3 (W3), 6 (W6) and 9 (W9) days using artificial structures. Changes in leaf physiology, carbon assimilation and biomass production were quantified at 0, 7, 14, and 21 days after anthesis under all treatments. Short-term (W3) waterlogging had no significant effect on wheat crops but W6 and W9 significantly reduced the net photosynthetic rate (Pn), leaf SPAD value, and grain weight of the tested cultivars. Increasing waterlogging duration significantly increased dry matter accumulation in the spike-axis + glumes but reduced dry matter accumulation in grain. Further, the tested cultivars responded significantly variably to W6 and W9. Averaged across two years, YM 18 performed relatively superior to YN19 in response to long-term waterlogging. For example, at 14 days after anthesis, W9 plants of YM18 and YN19 experienced a 17.4% and 23.2% reduction in SPAD and 25.3% and 30.8% reduction in Pn, respectively, compared with their W0 plants. Consequently, YM18 suffered a relatively smaller grain yield loss (i.e., 16.0%) than YN19 (23.4%) under W9. Our study suggests that wheat cultivar YM18 could protect grain development from waterlogging injury by sustaining assimilates supplies to grain under waterlogged environments.

Spatial correlation between the changes of ecosystem service supply and demand: An ecological zoning approach

Clarifying the spatial and temporal changes in the ecosystem services (ES) supply and demand helps in providing comprehensive supporting information for ecological governance decisions. However, spatial mismatches of the ES supply and demand changes are often overlooked, thereby resulting in the lack of targeted decision-making. In this study, the spatiotemporal variations of ES supply and demand in Guangdong Province during 2000-2015 were quantitatively analyzed at watershed scale. Ecological zoning was conducted on the basis of the temporal changes of ES supply and demand. Spatial correlation of ES supply and demand changes in different zones was further explored. The results showed that, the changes of ES supply and demand showed obvious spatial heterogeneity. The changes in the Pearl River Delta were significant, with ES supply decreasing and ES demand increasing. The ES supply changes were significantly affected by the ES demand changes. All of the ES supply would be significantly affected in the “high supply change–high demand change” zone; grain production, tropical cyclone mitigation, flood mitigation and habitat quality have been significantly affected in the “low supply change–middle demand change” zone; carbon sequestration, landscape recreation, grain production, flood mitigation and habitat quality have been significantly affected in the “low supply change–low demand change” zone. The increase in the land use change may promote the impact of the ES demand changes on the ES supply changes. This study helped in integrating the change of ES supply and demand and its correlation into the ecological protection and restoration system, thus providing a new perspective and approach for a regional sustainable management.

Facies analysis of the Middle Cretaceous Mishrif Formation in southern Iraq borehole image logs and core thin-sections as a tool

The Middle Cretaceous Mishrif Formation is one of the most important oil reservoirs in central and southern Iraq. The major goal of this study is to calibrate the FMI imaging log in front of the depth intervals where core data is available (thin sections), and then utilize the calibrated FMI behavior to predict the types of microfacies in the wells where core data is not available. Hence, this study focuses on distinguishing and correlating carbonate facies in four wells from the Mishrif Formation in the West Qurna and North Rumalia oilfields, southern Iraq, using borehole image logs and thin sections. Thin-section data from the cored wells were used to identify six carbonate environments based on their constituent carbonate microfacies and grain types. A succession of carbonate-environment-facies units was determined in the cores relative to already established members (mB2, mB1, CRII, mA, CRI) and used to discern how the borehole image logs respond to respective carbonate facies. These borehole image responses to changing carbonate-facies units were then used to identify similar behaviors in the wells without core and for correlation across the two oilfields. Thin-section analysis of microfacies and grain types led to the interpretation of six carbonate-environment facies in the Mishrif Formation, including mid-ramp, shoal, back-shoal, lagoonal and intertidal facies; a rudist-bioherm subfacies also occurred locally in shoal, back-shoal, and lagoonal facie units. The organization of the carbonate-environmental-facies units and their correlation across the two oilfields confirms that the Mishrif Formation in southern Iraq comprises two progradational depositional cycles, separated by a major transgressive flooding surface. Clearly, the combined analyses of thin sections from cored wells and borehole image responses from the same wells provide a powerful tool in understanding and correlating facies and sequences across nearby oilfields.

Carbon flux and alkaline volcanism: Evidence from carbonatite-like carbonate minerals in trachytes, Ulleung Island, South Korea

Abstract Carbon flux metasomatism in the subduction environment is an important process, but it remains poorly understood. The paucity of exposed lower crust and upper mantle rocks in continental arcs renders xenoliths a major target for studying the slab-derived carbon cycle. This study of the carbonate phases in volcanic rocks from three drill cores in Ulleung Island, South Korea, sheds light on the interaction of carbon flux in the upper mantle and lower crust in a back-arc setting. The volcanic rocks from Ulleung Island range in composition from trachybasalt to trachyte and contain abundant euhedral pseudomorphic carbonate grains, ulvöspinel-hosted and biotite-hosted carbonate-silicate melt inclusions, and irregular carbonate globules. Integrated petrographic and geochemical studies of a variety of phenocrysts, carbonate phases, and carbonate-silicate inclusions in biotite and ulvöspinel indicate that recharging of carbon flux affected magma evolution. Carbon and oxygen isotopes of the pseudomorphic carbonate grains overlap with mantle values, indicating a carbonatite-like origin of the carbonate phases. The (MgO, FeO, CaO)-rich silicates in ulvöspinel-hosted silicate inclusions and pseudomorphic carbonate grains likely represent a primary melt, which formed from the partial melting of carbonated eclogite of the subducted slab within the mantle wedge beneath Ulleung Island. A petrogenetic model is proposed to illustrate that the crystal mush in the magma chamber was intruded by carbonate-rich liquids and caused alteration of cumulate crystals to generate the euhedral pseudomorphic carbonate grains. The extrusive magma captured those pseudomorphic grains and erupted to form the trachybasalt-trachyte units. The observed carbonate phases and their geochemical characteristics indicate that carbon flux metasomatism played a fundamental role in this back-arc magmatism.

Assessment of Metal Pollution in the Sediments of Ras Al-Ardh and Yacht Club Marinas, Kuwait

This study aims to investigate the fate and behavior of five trace metals (Fe, Ni, Pb, Cu and V) in the surface sediments of two selected marinas, namely Ras Al-Ardh and Yacht Club, along the coastal area of Kuwait. Leached and total concentrations of Fe, Ni, Pb, Cu and V were measured along with the total organic carbon (TOC) and sediment grain size. The bioavailability of the trace metals was also determined using simple extraction techniques. The contamination factor (CF), enrichment factor (EF) and pollution load index (PLI) were used for assessing sediment quality at the marinas. The results indicated that TOC was related to the mean grain size, where higher TOC concentrations were associated with finer grain fractions. Trace metal distribution patterns were similar to the TOC in the sediments. The value of PLI showed that the Ras Al-Ardh marina had higher metal enrichment than that of the Yacht Club marina. The results of CF and EF indicated that the sediments within both marinas are "slightly polluted" to "moderately polluted". The sediments were less contaminated with Cu relative to Pb and Ni. The PLI class of metals at the Yacht Club indicated that the marina can be classified as "non-polluted" to "moderately polluted", while the Ras Al-Ardh marina can be classified as "moderately polluted" to "polluted". The study revealed that sediment grain size, TOC, and trace metal concentrations varied spatially within each marina depending on the type of development and the probable source of metals. Sediment quality has changed tremendously due to the expansion of tourism, progress in industrial activities and increase in recreational requirements near the coastal areas.

Resistive Switching Phenomenon Observed in Self-Assembled Films of Flame-Formed Carbon-TiO2 Nanoparticles.

Nanostructured films of carbon and TiO2 nanoparticles have been produced by means of a simple two-step procedure based on flame synthesis and thermophoretic deposition. At first, a granular carbon film is produced on silicon substrates by the self-assembling of thermophoretically sampled carbon nanoparticles (CNPs) with diameters of the order of 15 nm. Then, the composite film is obtained by the subsequent thermophoretic deposition of smaller TiO2 nanoparticles (diameters of the order of 2.5 nm), which deposit on the surface and intercalate between the carbon grains by diffusion within the pores. A bipolar resistive switching behavior is observed in the composite film of CNP-TiO2. A pinched hysteresis loop is measured with SET and RESET between low resistance and high resistance states occurring for the electric field of 1.35 × 104 V/cm and 1.5 × 104 V/cm, respectively. CNP-TiO2 film produced by flame synthesis is initially in the low resistive state and it does not require an electroforming step. The resistance switching phenomenon is attributed to the formation/rupture of conductive filaments through space charge mechanism in the TiO2 nanoparticles, which facilitate/hinder the electrical conduction between carbon grains. Our findings demonstrate that films made of flame-formed CNP-TiO2 nanoparticles are promising candidates for resistive switching components.

Gothic-Arch Calcite from Speleothems of the Bohemian Karst (Czech Republic): Its Occurrence, Microscopic Ultrastructure and Possible Mechanism of Growth

Gothic arch calcite, a specific crystallographic variety of calcite known from some hot springs and tufa streams, has been newly recognized in the Koněprusy Caves. The gothic-arch calcite occurs on the exteriors of exotic coralloid speleothems where it coexists with scalenohedral (dogtooth) spar crystals. The crystals exhibit microscopic ultrastructural features including deeply eroded topography, etch pits, and spiky and ribbon calcite crystallites, pointing to its extensive natural etching. Many gothic-arch calcites originated as late-stage, secondary overgrowths on older, etched dogtooth calcite crystals. Its characteristic outward curvature resulted from the recrystallization of etching-liberated fine carbonate grains and newly formed needle-fiber calcite laths, which were accumulated and bound on the faces and at the bases of corroded crystals. These intimately coexisting destructive and constructive processes of carbonate crystal corrosion and growth were probably mediated by bacteria, fungi, or other microorganisms. Fluid inclusions embedded in calcite crystals point to a vadose setting and temperatures below ~50 °C. This, combined with the wider geological context, indicates that the gothic arch calcite crystals originated only during the late Pleistocene to Holocene epochs, when the cave, initially eroded by hypogene fluids in the deeper subsurface, was uplifted to the subaerial setting and exposed to the meteoric waters seeping from the topographic surface. The radiocarbon analysis shows that gothic-arch calcite crystals are generally older than ~55,000 years, but the surface layers of some crystals still reveal a weak 14C activity, suggesting that microbiologically mediated alterations of the speleothems may have been occurring locally until now.

First MATISSE L-band observations of HD 179218

Context. Carbon is one of the most abundant components in the Universe. While silicates have been the main focus of solid phase studies in protoplanetary discs (PPDs), little is known about the solid carbon content especially in the planet-forming regions (~0.1–10 au). Fortunately, several refractory carbonaceous species present C-H bonds (such as hydrogenated nano-diamond and amorphous carbon as well as polycyclic aromatic hydrocarbons), which generate infrared (IR) features that can be used to trace the solid carbon reservoirs. The new mid-IR instrument MATISSE, installed at the Very Large Telescope Interferometer (VLTI), can spatially resolve the inner regions (~1–10 au) of PPDs and locate, down to the au-scale, the emission coming from carbon grains. Aims. Our aim is to provide a consistent view on the radial structure, down to the au-scale, as well as basic physical properties and the nature of the material responsible for the IR continuum emission in the inner disk region around HD 179218. Methods. We implemented a temperature-gradient model to interpret the disk IR continuum emission, based on a multiwavelength dataset comprising a broadband spectral energy distribution and VLTI H-, L-, and N-bands interferometric data obtained in low spectral resolution. Then, we added a ring-like component, representing the carbonaceous L-band features-emitting region, to assess its detectability in future higher spectral resolution observations employing mid-IR interferometry. Results. Our temperature-gradient model can consistently reproduce our dataset. We confirmed a spatially extended inner 10 au emission in H- and L-bands, with a homogeneously high temperature (~1700 K), which we associate with the presence of stochastically heated nano-grains. On the other hand, the N-band emitting region presents a ring-like geometry that starts at about 10 au with a temperature of 400 K. Moreover, the existing low resolution MATISSE data exclude the presence of aromatic carbon grains (i.e., producing the 3.3 μm feature) in close proximity tothe star (≲1 au). Future medium spectral resolution MATISSE data will confirm their presence at larger distances. Conclusions. Our best-fit model demonstrates the presence of two separated dust populations: nano-grains that dominate the near- to mid-IR emission in the inner 10 au region and larger grains that dominate the emission outward. The presence of such nano-grains in the highly irradiated inner 10 au region of HD 179218 requires a replenishment process. Considering the expected lifetime of carbon nano-grains from The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS model), the estimated disk accretion inflow of HD 179218 could significantly contribute to feed the inner 10 au region in nano-grains.Moreover, we also expect a local regeneration of those nano-grains by the photo-fragmentation of larger aggregates.

Salt weathering and ultrasonic pulse velocity: condition assessment of salt damaged porous limestone

Salt weathering is one of the crucial causes of building stone decay. For assessing the durability of stones against salt weathering, a standardised test procedure (EN 12370:2020 Determination of resistance to salt crystallisation) is used: the mass loss of the stone is measured during sodium sulphate crystallisation cycles. Porous, Miocene limestone test specimens collected from the Sóskút quarry (Hungary) were subjected to salt crystallisation cycles in laboratory conditions. The limestone with open porosities of up to 32 V% is composed of ooids, various types of bioclasts and other carbonate grains. Besides the classical measurements of mass changes, the ultrasonic pulse velocity was also recorded after each crystallisation cycle. The ultrasonic pulse velocity values of quarry stones and salt-laden porous limestone specimens were compared. The results indicate that when salt crystal clogs the pores, an increase in ultrasonic pulse velocity is observed. Additional salt crystallisation cycles reduce the pulse velocity. This negative shift in pulse velocities is linked to the opening of micro-cracks, indicating the damage of the studied limestone. Our tests have proved that ultrasonic pulse velocity testing device can detect salt crystallisation damage in a non-destructive way. Its application is recommended in the condition assessment of salt damaged stone heritage structures.

Strategic tillage achieves lower carbon footprints with higher carbon accumulation and grain yield in a wheat-maize cropping system

Continuous single tillage has the potential to increase greenhouse gas (GHG) emissions and decrease the accumulation of soil organic carbon (SOC), thus increasing carbon footprints (CFs). However, in a wheat-maize cropping system, limited information was available about the effects of strategic tillage on CFs. Thus, a four-year field experiment was conducted, including continuous rotary tillage (RT), continuous no-till (NT), RT + subsoiling (RS), and NT + subsoiling (NS), to investigate the effects of NS (strategic tillage) on the unit area and unit yield. The results showed that CO2 emission was the highest contributor to CFs (73.92%) in a winter wheat-summer maize cropping system, following the order of NS < NT < RS < RT. The direct N2O emissions from fertilizers and residues were 4.43–4.51 t CO2-eq ha−1 yr−1 during the wheat and maize seasons, and indirect N2O emissions from irrigation and fertilizer inputs had a proportion of >80% from total agricultural inputs. The differences in SOC storage significantly affected the CFs. Although the NS treatment increased the amount of GHG emissions from the residues returned and consumption of diesel, the enhancement of SOC storage by deeper SOC increased. Thus, lower area-scaled CFs were observed in the NS treatment. Furthermore, a higher grain yield and an annual change of SOC storage compared with other treatments were observed under the NS system, which helped to reduce the CFs. The yield-scaled CFs followed the order of RT > RS > NT > NS when considering the changes in SOC storage. Therefore, the NS treatment resulted in a higher grain yield and SOC sequestration with lower CFs, and thus, it could be recommended as the best tillage method to achieve sustainable production and environmental balance in a wheat-maize cropping system.