Bulk Density Research Articles

Clays to lightweight aggregates: Thermochemical modeling and industrial validation

The creation of thermochemical models to forecast the dependent variables governing the bloatability of lightweight aggregates (LWAs) is the goal of this work. Laser particle size analysis, XRD, XRF, IR, TGA-DTA, SEM-EDX, Laser imaging system, µ-CT, hot-stage microscope and Factsage (8.3) thermodynamic software were used for clays and LWAs characterization in the temperature range 900–1250°C. It was found that the LWAs bloating zone occurs at 1050–1250°C with a minimum bulk density (BD) of (0.74 g/cm3) at 1250°C. During the LWAs pyroplastic state, the crystallization of anorthite from the silicate melt lowers its viscosity due mainly to the alkalis’ uptake into the anorthite lattice. However, the silicate melt is still viscous enough to trigger the reduction of hematite and consequently guarantees the evolution of bloating gases. The simultaneous association of higher evolved gas with less melt content of higher viscosity would promote the LWAs bloatability. The higher the gas that accompanied with low melt of lower viscosity would loosen the LWAs their consistency and sphericity upon their sudden cooling. Based on the LWAs bulk density and lab experimental observations, the production window limits of successful LWAs are ≥40 wt% silicate melt of 103-107 Pa.s viscosity that accompanied with (0.50–4.00 wt%) gas content. This production window has been verified by Liapor industrial kiln feed. The LWAs pyroplastic and post-quenching characteristics are all statistically significant variables (<0.05) for prediction modeling. The forecasting models are statistically verified by the multi-collinearity testing that shows VIF values <10 indicating the absence of any multi-collinearity among the models’ explanatory variables.

Prediction of external corrosion rate for buried oil and gas pipelines: a novel deep learning with DNN and attention mechanism method

Buried pipelines is easily subjected to external corrosion affected by complex underground environment, such as soil resistivity, pH, dissolved ion concentration, water content and coatings condition. Therefore, external corrosion rate prediction is essential to ensure pipelines intrinsic safety. Generally numerous researches focused on mathematical models and degradation analysis are limited to considering comprehensive corrosion factors. In this work, a novel proposed deep learning method involves a deep neural network (DNN) and attention mechanism which has good robust generalization ability. DNN was used to predict external corrosion rate of buried pipelines with extracting corrosion characteristics data, and attention mechanism is carried on weighting operations of corrosion factors furtherly. The results show that main controlling factors are pipeline age and soil bulk density, sulfate ion concentration and redox potential have less effect by analyzing external corrosion factors dataset, and data reduction and standardization of DNN-attention mechanism model are carried out. The external corrosion rate value predicted by the DNN-attention mechanism model is the closest prediction with the real truth, which the evaluation index root mean square error (RMSE) is 0.0064, and prediction accuracy is 91.91% compared with convolutional neural network (CNN), CNN-residual, DNN. It proves that it is reasonable to use DNN-attention mechanism to predict the pipeline corrosion rate by using publicly pipeline corrosion dataset.

Determining Eastern Red Cedar Biochar Soilless Media Supplementation Rates for Potted Ornamental Kale and Chrysanthemum Production

The increasing demand for soilless media, sustainability issues with peatmoss, and increasing cost of peatmoss have prompted studies of more environmentally friendly and less expensive substitutes. Biochar, a lightweight black carbon material produced by the pyrolysis of biomass, has gained popularity as a soilless media supplement. The objective of this study was to evaluate Eastern red cedar (ERC) biochar as a supplement to soilless media for the production of chrysanthemum and ornamental kale. Treatments included ERC biochar produced at three different temperature ranges of 300 to 350 °C, 400 to 450 °C, and 500 to 550 °C that were applied at 25%, 50%, and 75% v/v plus a control (100% v/v of standard commercial mix). Additionally, ERC bark was applied at the same rate as biochar. The 300 to 350 °C and 400 to 450 °C temperature ranges increased the bulk density of the media, whereas total porosity was greatest with just bark. Regarding the physical properties of the media, in general, the 75% v/v supplementation rate of ERC bark or biochar at any temperature increased air porosity but decreased the water holding capacity, except for the water holding capacity at 500 to 550 °C. As the biochar production temperature increased, so did the pH and electrical conductivity (EC), whereas volatile matter decreased. Plant height, width, shoot dry weight, root dry weight, number of flowers (chrysanthemum only), flower diameter, and water use efficiency were greatest with the 100% v/v soilless media for both species. In general, chrysanthemum plants grown with 25% v/v biochar supplementation or bark had similar height, width, and shoot dry weight at any temperature compared with those grown with the 100% v/v soilless media. For ornamental kale, the 25% v/v 400 to 450 °C biochar supplementation showed plant height and water use efficiency similar to those of the 100% v/v soilless media. In general, 25% ERC bark performed similar to 25% v/v and 50% v/v biochar at any temperature for plant width, shoot dry weight, root dry weight, water use efficiency, and root-to-shoot ratio. The media nutrient content and EC were greater with 100% v/v soilless media and a lower rate (25% v/v) of ERC bark and biochar than with higher rates. The higher levels of biochar were harmful and reduced the ornamental kale growth and quality. These results suggest that supplemented soilless media with lower rates (25% v/v) of ERC biochar could be recommended for chrysanthemum, but that less than 25% v/v may be necessary for ornamental kale.

Suitability of using areca nut fiber as reinforcing material in compressed stabilized earth blocks (CSEB) for low-cost housing

An economical and cost-effective replacement for conventional building materials is Compressed Stabilized Earth Block (CSEB). However, they are vulnerable to erosion and cracking, particularly in humid settings. The use of natural fibers as reinforcement is found effective in overcoming this problem. Areca nut fiber which is a complete waste material in countries like Bangladesh and India is also a sturdy, adaptable, and water-resistant natural fiber that makes it the perfect choice as fiber reinforcement material for CSEBs. In this article, the strength performance analysis of areca nut fiber as a reinforcement material for CSEBs is investigated, where 0%, 0.85%, 2%, 5%, and 8% of areca nut fiber is mixed with soil that is stabilized with 10% cement. CSEB specimens of 4″ × 4″ × 4″ size have been made and tested for compressive strength, tensile strength, bulk density, and water absorption. It is observed that there is an 83.76% increase in compressive strength and an 8.89% increase in splitting tensile strength for 0.85% of areca nut fiber content specimen cured for 90 days. The water absorption was found a minimum of 9.07% for 0.85% areca nut fiber content and the minimum density of the block was observed at 1810 kg/m3 for the optimum percentage of 0.85% mix. The study indicates that using 0.85% of areca nut fiber content in stabilized CSEB shows a significant improvement in the strength characteristics of compressed stabilized earth blocks.Graphical

Assessing the Influence of Soil Physical Properties on the Puddling Quality: A Comprehensive Review

Puddling is a crucial step in rice cultivation, extensively practiced by farmers in Asia for its role in softening soil, aiding in transplanting, and enhancing water and nutrient management. However, the alteration of soil properties by puddling raises concerns about its long-term sustainability. This comprehensive review systematically examines the impact of puddling on soil parameters such as soil texture, bulk density, penetration resistance, hydraulic conductivity, puddling index, and percolation rate. By synthesizing existing literature, the review aims to inform sustainable agricultural practices and effective soil management strategies amidst escalating global concerns. The complexities of puddling's influence on soil structure underscore the need to consider variables like soil texture and aggregate stability. Sustainable practices such as organic manure application offer potential solutions to address puddling-induced compaction, thereby enhancing soil quality and rice production efficiency. Optimizing tillage methods and improving hydraulic conductivity are essential components of effective soil management strategies for sustainable rice cultivation. Additionally, assessing puddling quality through indices like the puddling index and optimizing percolation rates are vital steps toward improving water management and overall productivity in rice farming.

Effect of Si3N4 Additive on Microstructure and Mechanical Properties of Ti(C,N)-Based Cermet Cutting Tools

Development of high-performance cutting tool materials is one of the critical parameters enhancing the surface finishing of high-speed machined products. Ti(C,N)-based cermets reinforced with and without different contents of silicon nitride were designed and evaluated to satisfy the requirements. In fact, the effect of silicon nitride addition to Ti(C,N)-based cermet remains unclear. The purpose of this study is to investigate the influence of Si3N4 additive on microstructure, mechanical properties, and thermal stability of Ti(C,N)-based cermet cutting tools. In the present work, α-Si3N4 “grade SN-E10” was utilized with various fractions up to 6 wt.% in the designed cermets. A two-step reactive sintering process under vacuum was carried out for the green compact of Ti(C,N)-based cermet samples. The samples with 4 wt.% Si3N4 have an apparent solid density of about 6.75 g/cm3 (relative density of about 98 %); however, the cermet samples with 2 wt.% Si3N4 exhibit a superior fracture toughness of 10.82 MPa.m1/2 and a traverse rupture strength of 1425.8 MPa. With an increase in the contents of Si3N4, the Vickers hardness and fracture toughness of Ti(C,N)-based cermets have an inverse behavior trend. The influence of Si3N4 addition on thermal stability is clarified to better understand the relationship between thermal stability and mechanical properties of Ti(C,N)-based cermets.

Effects of pelletization on biomethane production from wheat straw

ABSTRACT The high lignin content and low bulk density of wheat straw pose challenges for biogas production. To overcome these hurdles, pretreatment and biomass pelletization have emerged as viable options. Thus, this research aims to reduce the recalcitrant nature of WS by employing various thermal pretreatment techniques and identifying the optimum parameters (temperature and time). To prepare pellets, a mixture comprising wheat straw (subjected to the best pretreatment) and cow manure pellets (WCP) at varying substrate and binder (Svs/Bvs) ratios ranging from 0.5 to 2.5 were used. Parameters such as density, water absorption, and drop shattering were evaluated to evaluate the physical characteristics of produced WCP. Additionally, the biomethane yield test of WCP (exhibiting the most favourable physical characteristics) was performed with various total solids (TS) concentrations from 4 to 12%. The WS demonstrated the highest sCOD solubilisation of 9066 mg/L when subjected to a hot air oven pretreatment (90 min at 110°C). The physical qualities of WCP were found to be dependent on the Svs/Bvs ratio (with the optimal ratio being 2.0). It was also observed that a TS content of 6% yielded the highest biomethane production (253.85 mL/g-VSconsumed). In summary, this study’s conclusion waves the path of management of wheat straw and cow dung while simultaneously generating bioenergy.

Effects of soil bulk density on respiratory metabolism and medicinal quality of Rehmannia Glutinosa root

As one of the famous "four huai medicines", Rehmannia glutinosa has a longstanding usage history. This study aimed to determine how variations in soil bulk density impact the respiration metabolism of R. glutinosa root tubers and, consequently, the quality of its medicinal components. We evaluated the enzymatic activities and key metabolic compounds of R. glutinosa across a range of soil bulk densities, which included: pyruvate kinase (PK), pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), isocitrate dehydrogenase (IDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), and the content of pyruvate, ethanol, lactic acid, succinic acid, malic acid, and quality indicators. High soil bulk density increased the activities of PK, PDC, ADH, and LDH, while decreasing SDH, MDH, and IDH in the roots. This shift in enzymatic activities corresponded to elevated levels of ethanol and lactic acid, and lowered levels of succinic and malic acids. In the additionally, the growth and development of aboveground parts of R. glutinosa were seriously hindered under high bulk weight treatment, and the number of root tubers decreased, root coarser and root length shortened, and the contents of catalpa alcohol and mullein were significantly reduced. Our findings suggest an optimal soil bulk density for R. glutinosa growth to be between 1.2 g/cm3 and 1.4 g/cm3. Based on changes in respiratory metabolism and medicinal quality indicators of R. glutinosa under different soil bulk densities, our findings suggest the optimal soil bulk density for R. glutinosa growth is 1.2 g/cm3 to 1.4 g/cm3. Excessively high soil bulk density will affect the growth and quality formation of R. glutinosa by influencing its metabolism. Recognizing this optimal range is crucial for maximizing the medicinal quality of R. glutinosa, offering valuable insights for cultivation practices.

Engineering Characteristics of Curcuma Flour (Curcuma xanthorrhiza Roxb.) from Convection Drying

Curcuma is a herbs having a lot of advantages for human health. The fresh rhizome has a lot of disadvantages especially from the volume and low quality. To maintain the quality, curcuma should be processed to curcuma flour. This study was carried out to determine the engineering properties including water content, color, bulk density, water absorption, oil absorption, and angle of repose of curcuma flour ground after convection drying. The research method used in this study was CRD (completely randomized design) with 2 factors, namely drying temperature (40 °C, 50 °C, and 60 °C) and flouring or milling duration (6, 8, and 10 min). Curcuma rhizome was pre-treated with a convection drying. After milling process, the flour was sieved to have particle size of 60 mesh. Statistical analysis included ANOVA (Analysis of Variance), Duncan post-hoc test, and correlation test. The result revealed the curcuma flour has engineering properties including bulk density (0.35 – 0.38 g/ml), water content (7.97% – 11.77%), water absorption (2.78 – 3.79 ml/g), angle of repose (27.99° – 30.44°), color brightness L (67.07 – 71.78), red-green chrome a (7.67 – 8.92), yellow-blue chrome b (51.37 – 55.13), and total color change ∆E (57.42 – 62.12). Keywords: Convection dryer, Curcuma, Drying, Engineering characteristics, Flour.

Uncertainty resulting from constant bulk density assumption when interpreting soil nutrient concentrations

Uncertainty resulting from constant bulk density assumption when interpreting soil nutrient concentrations

Assessment of Physico-chemical Properties of Soil from Various Regions of Different Taluk of Pathanamthitta District in the State of Kerala, India

The assessment of Physico-Chemical Properties of Soil from Various Regions of Different Taluk of Pathanamthitta District of Kerala in 2023-24 was a valuable endeavour. A total of 27 samples were collected at profile depths of 0-15, 15-30, and 30-45. It is interesting to note the variations in soil colour between dry and wet conditions, ranging from light brown to dark reddish brown.The soil textural class was identified as Sandy clay Loam, and the sand, silt and clay percentage varied from 45.18% to 50.64%, 17.21% to 20.70%, 30.91% to 34.61%. Bulk Density was varied from 1.08 Mg m-3 to 1.28 Mg m-3. The Particle Density varied from 2.02 Mg m-3 to 2.55 Mg m-3. The Pore Space (%) ranged from 40.18% to 50.62%. The Water Retaining Capacity (%) ranged from 39.19 to 48.98%. The pH value ranged from 4.9 to 6.9. The Electrical Conductivity ranged from 0.03 to 0.30 dS m-1. The value of total Organic Carbon (%) varied from 0.16 to 1.68 %. The available Nitrogen content of soil ranged from 119.45 to 286.07 kg ha-1. The available Phosphorus content of soil ranged from 13.23 to 64.20 kg ha-1. Available Potassium content of soil ranged from 100.80 to 382.40 kg ha-1. Exchangeable Calcium content of soil ranged from 1.7(meq 100g-1) to 9.1(meq 100g-1). Exchangeable Magnesium content of soil ranged from 0.23 (meq 100g-1) to 0.74(meq 100g-1). The Sulphur content of soil ranged from 0.03 to 0.44 kg ha-1. The findings revealed minor increases in bulk and particle density with depth, yet the overall physical condition of the soil seems favourable for plant growth. It is evident that the soils are slightly acidic but meet the acceptable EC limit. The high levels of Organic Carbon are promising, while Nitrogen is lower and Phosphorus and Potassium levels are moderate to high. However, secondary nutrients like Calcium, Magnesium, and Sulphur are relatively low. Nutrient levels appear to be influenced by soil depth, with leaching due to higher precipitation levels in the area contributing to nutrient deficiencies. The results suggest that improvements can be made by implementing strategies such as cover crops, green manure, legume cultivation, mulching, and specific cropping systems to address leaching concerns.

Effect of Bambara Groundnut Flour (Vigna subterranea) Inclusion on the Functional, Pasting, Physical and Proximate Properties of Composite Cassava-bambara Flour

This study evaluated the effect of Bambara groundnut flour inclusion on the functional, pasting, physical properties and proximate compositions of composite flour (CF) from cassava and Bambara groundnut. Cassava variety (IITA-TMS-IBA011368) and Bambara groundnut were processed into flour and blended together based on D-Optimal mixture design with an outcome of eight experimental samples using Design Expert Software (Version 12.0). The flour blends were analyzed for functional, pasting, physical properties (color), baking strength and proximate composition. Data obtained were analyzed using analysis of variance and means were separated using Ducan’s Multiple Range Test. Range of results for bulk density, water absorption capacity, swelling index, solubility index and oil absorption capacity of the composite flour are 0.64-0.80g/mL, 0.38-1.37%, 0.77-0.91%, 6.00-8.65, 1.58-2.97, respectively. The peak viscosity, trough, breakdown viscosity, final viscosity, setback viscosity, peak time and pasting temperature ranged from 162.84±2.09 to 426.50±1.83 RVU, 77.96±2.71 to 195.59±8.91 RVU, 84.88±0.63 to 234.75±5.58 RVU, 158.92±4.34 to 293.17±1.34 RVU, 76.88±18.04 to 101.42±5.08 RVU, 4.10±0.03 to 5.93±0.00 min and 75.05±0.05 to 94.78±0.38 oC, respectively. The baking strength characteristics of the flour blends such as moisture, ash, color, wet gluten, zenleny dry protein and wet protein ranged from 11.55 to 12.55%, 0.50 to 1.25%, 88.65 to 90.55, 8.35 to 13.80, -2.35 to 41.25, 4.92 to 13.85% and 4.53 to 11.99 %, respectively. Moisture, ash, fibre, fat, protein and carbohydrate of the composite flour ranged from 7.57 to 11.87%, 0.42 to 2.40 %, 1.78 to 3.00%, 2.81 to 5.62%, 8.42 to 12.68% and 67.61 to75.99%, respectively. Flour lightness, redness and yellowness ranged from 33.22 to 54.10, -2.89 to-1.14, 5.94 to 9.35, respectively. The inclusion of Bambara groundnut flour had a significant effect on the functional (swelling index, water and oil absorption capacity), pasting (peak, trough and final viscosity) and proximate (ash, fat and carbohydrate) properties of the flour blends.

Soil Degradation due to Long-term Citrus Cultivation in the Upper Vietnamese Mekong Delta

This study investigated the impact of tree age on soil properties in citrus orchards in the upper Vietnamese Mekong Delta province, examining orchards of four age groups (&lt;10, 10–20, 21–30, and over 30 years) at two soil depths (0–20 cm and 20–50 cm). Findings indicate notable variations in soil physicochemical properties with age and depth. In older orchards (over 20 years), bulk density increased and soil pH decreased, with overall low pH values (3.5–5.0) observed. Electrical conductivity remained consistent across all ages. Key nutrients such as nitrogen (N), phosphorus (P), potassium (K), soil organic carbon (SOC), and cation exchange capacity (CEC) generally decreased with the age of the orchards. These trends were consistent across both soil layers. The study highlights the influence of prolonged cultivation on soil health and provides insights for developing strategies to enhance productivity and sustain agricultural practices in citrus orchards.

Effect of Different Level of Chitosan and Beeswax Edible Coating on Storage Life and Physio-Chemical Properties of Strawberry (Fragaria × ananassa) cv Winter Dawn

The present investigation was done to understand the effect of different edible coating on increasing the shelf-life of strawberry at room temperature. Postharvest losses in fruits are a serious problem due to rapid deterioration during storage. Use of edible coatings over fruits is used to improve their quality and enhance the shelf life. The main purpose of this study was to assess the effect of Chitosan and beeswax coating in extending the shelf-life of strawberry including physio -chemical changes at room temperature. The experiment was laid out in completely randomized design (CRD) with 10 treatments and 3 replications. The treatment consisted of coating material with Chitosan (1.5g%), Chitosan +TPP (1.5g+0.5g%), Chitosan +TPP (1.5g+1%), beeswax (5g), beeswax + TPP (5G+1.5%), Chitosan+ beeswax (0.75g+ 2.5g), Chitosan+ beeswax +TPP(0.75g+2.5g+0.5%), Chitosan+ beeswax +TPP (0.75g+2.5g+1%). Statistical analysis revealed that the treatment chitosan 1.5g+ TPP 1% had the minimum Weight loss 0.08g, while having the maximum amount of Vitamin C 38.45mg/100g, Hardness 8.07 kg/inch2, Bulk Density 1.9g/cm3 and TSS 5.13°Bx. However, Chitosan 1.5g+TPP 0.5% showed maximum Reducing sugar 3.73% and non-reducing sugar 0.92%. While chitosan 0.75g+ beeswax 2.5g+TPP 0.5g have the maximum Total sugar 5.23%.

A Route for Bioenergy in the Sahara Region: Date Palm Waste Valorization through Updraft Gasification

The Adrar region (Algeria) has a total of 397,800 date palm trees (Phoenix dactylifera L.). Due to annual palm cleaning, large quantities of lignocellulosic biomass are produced. Depending on the variety, an average of 65 kg of biowaste is obtained per palm tree. Since the value of this biowaste is underrated, most of the palms are burned outdoors, causing air and visual pollution. This work explores the gasification potential of lignocellulosic waste from date palms (Phoenix dactylifera L. Takarbouche variety) into useful energy. The technology investigated is air updraft fixed-bed gasification, thanks to an originally designed and built reactor, with the capability to process 1 kg of feedstock. Four types of palm waste—namely, palms, petioles, bunch, and bunch peduncles—are first characterized (bulk density, proximate analysis, fixed carbon, elemental composition, and calorific value) and then used as feedstock for two gasification tests each. The syngas produced for the four date palm wastes is combustible, with an outlet temperature between 200 and 400 °C. The operating temperature inside the gasifier varies according to the feature of the biomass cuts (from 174 °C for the peduncles to 557 °C for palms). The experimental setup is also equipped with a cyclone, allowing for the recovery of some of the tar produced during the tests. Finally, the results show that the residence time has a positive effect on the conversion rate of date palm waste, which can significantly increase it to values of around 95%.

Static Compaction on Coupled Precursors and Optimizing Molarity for Enhanced Strength and Durability of Geopolymer

The static compaction technique emphasizes the reduced activator dosage required to develop geopolymers. Therefore, it is crucial to comprehend the optimal alkaline activator concentration for blending low-calcium precursor (fly ash) with high-calcium precursor (GGBS) to produce geopolymer blocks. This work was designed to optimize structural blocks’ compressive strength and durability. In experimentation, fly ash (FA) and slag (GGBS) proportions were initially investigated under NaOH solution with varying molarity (8–12) and curing conditions to develop a load-bearing structural block. Subsequently, the durability of the optimized block was evaluated over 56 days through subjection to sulfate and acidic solutions, with efflorescence monitored over the same period. The results reveal that the structural block comprised of 100% FA exhibits the highest compressive strength and lowest bulk density. Conversely, the block incorporating 25% slag that underwent hot curing demonstrates a remarkable 305% strength increase compared to ambient curing. Considering the physico-mechanical performance, the 100% FA block was chosen for durability investigation. The findings indicate a substantial strength loss exceeding 40% after exposure to sulfate and acidic environments over 56 days, coupled with pronounced efflorescence. Catastrophic failure occurs in all cases due to significant strength deterioration. The FTIR spectrum revealed the shifting of the wavenumber to a higher value and verified the depolymerization and leaching of alumina under acidic exposure. However, the developed geopolymer blocks demonstrate superior sustainability and feasibility compared to conventional fired clay bricks and cement-based FA bricks. Despite slightly higher costs, these blocks exhibit greater strength than their counterparts after enduring severe exposures.

Properties of different graded coir pith by Keen-Raczkowski box and Brunauer-Emmett-Teller analysis

Aim: To evaluate the physical and hydrological properties of different graded coir pith and composted coir pith (CPOM) following the Keen-Raczkowski box and Brunauer-Emmett-Teller (BET) analysis. Methodology: The coir pith was collected and composted by PITH PLUS (Pleurotus-sajor-caju). Thereafter, the coir pith and composted coir pith were segregated into different groups based on the size of the particles as 1.0 mm (1000 microns), 0.5 mm (500 microns), and 0.25 mm (250 microns). Based on particle size, the hydrological properties of coir pith and composted coir pith were determined. The physical and hydrological properties were estimated by the Keen-Raczkowski box method and Brunauer-Emmett-Teller analysis. Results: Different graded coir pith and composted coir pith of size 0.25 mm showed the highest bulk density (0.60 and 0.48 g cm-3), followed by 0.5 mm size coir pith and composted coir pith, respectively. The highest particle density (0.18 and 0.19 g cm-3) was registered in 1.0 mm coir pith and composted coir pith whereas the lowest particle density was observed in 0.25 mm size coir pith (0.15 g cm-3). The water-holding capacity (817.93 % and 806.97 %) and water in air-dry substrate (25.03 % and 36.094 %) was high in 0.25 mm coir pith and composted coir pith. Interpretation: A 0.25 mm grade of coir pith and composted coir pith showed highest water holding and retaining capacity due to a greater number of small particles being compactly arranged and holding more surface area, and innumerable micropores than other graded particles. Key words: BET analysis, Coir pith, Composted coir pith, Water holding capacity

The TESS-Keck Survey. VII. A Superdense Sub-Neptune Orbiting TOI-1824* *Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c)3 nonprofit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of

We confirm a massive sub-Neptune-sized planet on a P = 22.8 days orbit around the star TOI-1824 (T eff = 5200 K, V = 9.7 mag). TESS first identified TOI-1824 b (formerly TOI-1824.01) as an object of interest in 2020 April after two transits in Sector 22 were matched with a single transit in Sector 21. TOI-1824 was subsequently targeted for ground-based Doppler monitoring with Keck-HIRES and APF-Levy. Using a joint model of the TESS photometry, radial velocities, and Ca ii H and K emission measurements as an activity indicator, we find that TOI-1824 b is an unusually dense sub-Neptune. The planet has a radius R p = 2.63 ± 0.15 R ⊕ and mass M p = 18.5 ± 3.2 M ⊕, implying a bulk density of 5.6 ± 1.4 g cm−3. TOI-1824 b's mass and radius situate it near a small group of “superdense sub-Neptunes” (R p ≲ 3 R ⊕ and M p ≳ 20 M ⊕). While the formation mechanism of superdense sub-Neptunes is a mystery, one possible explanation is the constructive collision of primordial icy cores; such giant impacts would drive atmospheric escape and could help explain these planets' apparent lack of massive envelopes. We discuss TOI-1824 b in the context of these overdense planets, whose unique location in the exoplanet mass–radius plane make them a potentially valuable tracer of planet formation.

Ultralow shrinkage polyimide hybrid aerogel composite enhanced with organic fibers for thermal protection

AbstractPolyimide PI aerogels possess a rather potential in thermal protection material for aircraft, owing to their low thermal conductivity, high thermal stability, and low bulk density. However, the large shrinkage of pure PI aerogels is still a challenge in the complete preparation process. Herein, a kind of PI hybrid aerogel composite was prepared successfully by introducing polyurethane fiber as the reinforcing agent. The aerogel composite could realize the enhancement for the pure PI aerogels from a micro/macroscopic perspective, ultimately ensuring the ultralow shrinkage rate of 3.52%. Due to the inhibition of the shrinkage characteristic, the aerogel composite obtained achieved excellent thermal insulation, especially retaining a low temperature of 40.7°C despite the hot surface temperature reached up to 150°C. Besides, the lightweight low‐density, exceptional flame resistance, and self‐extinguishing properties were reflected from PI hybrid aerogel composite constructed, including the outstanding hydrophobic feature (water contact angle of 120°). The PI hybrid aerogel composite as prepared may be used for the thermal management of aircraft in a great measure, illustrating the feasible strategy of fabricating PI‐based aerogel composites.

Response of soil quality degradation to cultivation and soil erosion: A case study in a Mollisol region of Northeast China

Soil degradation is endangering agricultural and ecological sustainability in the Mollisol region of Northeast China. Cultivation and soil erosion are the primary drivers degrading soil quality. However, few studies have comprehensively quantified the effects of cultivation and soil erosion on soil quality degradation in Mollisols. Therefore, three sampling sites with similar landscapes, erosion environments and agricultural management practices were selected. The cultivation chronosequence was determined using a space-for-time substitution approach, including 1) forestland without cultivation (0 yr, stage I), 2) farmland with few cultivation years (< 20 yr, stage II), and 3) farmland with many cultivation years (> 80 yr, stage III). Soil erosion was quantified using the caesium-137 (137Cs) and black soil thickness. Sixteen soil physicochemical indicators were analyzed, and soil quality and its degradation were evaluated using an integrated soil quality index (SQI) and a soil degradation index (SDI), respectively. The results showed that soil erosion was profoundly accelerated by cultivation. Soil organic carbon (SOC), bulk density (BD), mean weight diameter (MWD) and soil erodibility (K) factor were selected to develop the SQI. The SQI was higher in stage I (0.61±0.05) than in stages II (0.49±0.06) and III (0.52±0.03) and decreased with increasing soil erosion rate, implying that cultivation and soil erosion exacerbated the degradation of soil quality. Furthermore, cultivation and soil erosion contributed 16.0–51.1% and 2.0–18.4% to the changes in soil quality, respectively, and their combination further amplified the impacts (8.4–61.5%). Cultivation and accelerated soil erosion driven by cultivation led to the degradation of soil quality; the former controlled the degradation processes mainly by decreasing the MWD, and the latter induced soil quality degradation by reducing the SOC and increasing the K factor. These findings are important for advancing our understanding of the driving forces and mechanisms of soil degradation in the Mollisol region.