Salt Leaching Research Articles

The Effect of Pore Size Distribution and l-Lysine Modified Apatite Whiskers (HAP) on Osteoblasts Response in PLLA/HAP Foam Scaffolds Obtained in the Thermally Induced Phase Separation Process.

In this research, we prepared foam scaffolds based on poly(l-lactide) (PLLA) and apatite whiskers (HAP) using thermally induced phase separation technique supported by the salt leaching process (TIPS-SL). Using sodium chloride having a size of (a) 150–315 μm, (b) 315–400 μm, and (c) 500–600 μm, three types of foams with different pore sizes have been obtained. Internal structure of the obtained materials has been investigated using SEM as well as μCT. The materials have been studied by means of porosity, density, and compression tests. As the most promising, the composite prepared with salt size of 500–600 μm was prepared also with the l-lysine modified apatite. The osteoblast hFOB 1.19 cell response for the scaffolds was also investigated by means of cell viability, proliferation, adhesion/penetration, and biomineralization. Direct contact cytotoxicity assay showed the cytocompatibility of the scaffolds. All types of foam scaffolds containing HAP whiskers, regardless the pore size or l-lysine modification induced significant stimulatory effect on the cal-cium deposits formation in osteoblasts. The PLLA/HAP scaffolds modified with l-lysine stimulated hFOB 1.19 osteoblasts proliferation. Compared to the scaffolds with smaller pores (150–315 µm and 315–400 µm), the PLLA/HAP foams with large pores (500–600 µm) promoted more effective ad-hesion of osteoblasts to the surface of the biomaterial.

Poly(ε-caprolactone)/Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Blend from Fused Deposition Modeling as Potential Cartilage Scaffolds

The scaffolds of poly(ε-caprolactone)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PCL/PHBV) blends were fabricated from fused deposition modeling. From indirect cytotoxicity testing based on mouse fibroblasts, all scaffolds with various blend ratios were nontoxic to cells. The surface-treated scaffold with a blend ratio of 25/75 PCL/PHBV exhibited the highest proliferation of porcine chondrocytes and total glycosaminoglycans (GAGs) after 21 days of culture. The scaffolds with a blend ratio of 25/75 with local pores (LP) were prepared from FDM along with a salt leaching technique using NaCl as porogens. The effect of NaOH in surface treatment on the biological property of scaffolds was investigated. The scaffolds with LP and with 1 M NaOH surface treatment exhibited the highest proliferation of cells and total GAGs after 28 days of culture. The degradation behaviors of the scaffolds were studied. The nonsurface treated, surface treated without LP, and surface treated with LP scaffolds were degraded in phosphate buffer (pH 7.4) for 30 days at 37°C and 50°C for nonenzymatic condition and at 37°C for enzymatic condition. The surface treated with LP scaffold showed the highest amount of weight loss, followed by the surface treated without LP, and the nonsurface-treated scaffolds without LP, respectively. The results from Fourier-transform infrared spectroscopy indicated degradation of PCL and PHBV through hydrolysis of the ester functional group. The compressive strengths of all scaffolds were sufficiently high. The results suggested that the scaffolds with the existence of LP and with surface treatment showed the highest potential for use as cartilage scaffolds.

Development of a 3D polyetheretherketone structure that mimics the cranial bone morphology for use in cranioplasty

Cranioencephalic traumatism (TBI) is a common situation in trauma hospitals and has become responsible for high rates of mortality worldwide. When the victim of TBI is affected by injuries to the skullcap with a need for grafting, problems regarding the availability of suitable and affordable materials eventually happen. In this study, a 3D structure of Polyetheretherketone (PEEK) that mimics the cranial bone morphology for use in cranioplasty was developed. Samples of different formulations, in the form of round bars, were obtained through uniaxial compression, and porosity was controlled by the salt leaching technique. Then, the specimens were characterized in terms of pore morphology and distribution, surface roughness, compression resistance and cytotoxicity. Results exhibited high levels of similarity of the 3D strutures of PEEK to the natural human bone, which indicates the effectiveness of the proposed method in mimicking the morphology of the compact/porous/compact system of the skullcap (diploe).

Fabrication of a Porous Three-Dimensional Scaffold with Interconnected Flow Channels: Co-Cultured Liver Cells and In Vitro Hemocompatibility Assessment

The development of large-scale human liver scaffolds equipped with interconnected flow channels in three-dimensional space offers a promising strategy for the advancement of liver tissue engineering. Tissue-engineered scaffold must be blood-compatible to address the demand for clinical transplantable liver tissue. Here, we demonstrate the construction of 3-D macro scaffold with interconnected flow channels using the selective laser sintering (SLS) fabrication method. The accuracy of the printed flow channels was ensured by the incorporation of polyglycolic acid (PGA) microparticles as porogens over the conventional method of NaCl salt leaching. The fabricated scaffold was populated with Hep G2, followed by endothelization with endothelial cells (ECs) grown under perfusion of culture medium for up to 10 days. The EC covered scaffold was perfused with platelet-rich plasma for the assessment of hemocompatibility to examine its antiplatelet adhesion properties. Both Hep G2-covered scaffolds exhibited a markedly different albumin production, glucose metabolism and lactate production when compared to EC-Hep G2-covered scaffold. Most importantly, EC-Hep G2-covered scaffold retained the antiplatelet adhesion property associated with the perfusion of platelet-rich plasma through the construct. These results show the potential of fabricating a 3-D scaffold with interconnected flow channels, enabling the perfusion of whole blood and circumventing the limitation of blood compatibility for engineering transplantable liver tissue.

Dense-porous multilayer ceramics by green shaping and salt leaching

Dense Porous multilayer ceramic structures were fabricated using a simple novel ceramic dough process for the first time, where the hydrophobic ceramic dough was mixed with hydrophilic porogen like salt to form porous structure. Dense dough and porous mixture were processed in the ambient atmosphere and layered in green state before drying. Salt leaching for porogen removal was performed in warm water followed by binder burnout and sintering. Micro CT and electron microscopy revealed an intimate contact at the interface and 51–63 ​Vol% porosity in the porous layer was achieved with 44–48% open porosity. Intimacy was further supported by mechanical testing in compression mode where the crack propagated through the porous layer adjacent to the interface. The interfacial bonding between layers is independent of the individual layer thickness without cambering or warping. This simple dough processing produced bimodal pores after sintering with large macropores of diameter 250–500 μm and small macropores in the range of 1–3 μm on the pore walls, suitable for bone and vascular ingrowth. A further possibility of machining the dense body in a green state and fabricating a dental implant analogue with a porous apical portion for bone ingrowth were successfully explored.

Impact of biochar and lignite‐based amendments on microbial communities and greenhouse gas emissions from agricultural soil

AbstractUnderstanding the responses of the microbial community and greenhouse gas (GHG) emissions to the incorporation of different organic amendments is essential for their proper utilization. In this study, laboratory‐incubated microcosm experiments were conducted to investigate the short‐term effects of pine‐wood biochar and lignite‐based amendment on the microbial communities and GHG emissions from agricultural soil. Soils amended at five different application rates were incubated for 19 d under the conditions of 60% water‐filled pore space and 25 °C. Microbial biomass in the amended soil after incubation was measured by the solid colony counting method, and the soil microbial diversity was assayed using a Biolog EcoPlate. The biochar and lignite‐based amendment had distinct effects on the soil microbial communities and GHG emissions. The microbial community growth and utilization of C sources were improved by the biochar but restrained by the lignite‐based amendment in most cases. The biochar and lignite‐based amendment had a minor impact on methane emissions. Carbon dioxide emissions were promoted by the biochar and inhibited by the lignite‐based amendment during the short‐term incubation period. Nitrous oxide emissions decreased with the application rate of biochar but increased with the rate of lignite‐based amendment. The addition of biochar at a rate of 3–4% and lignite‐based amendment at a rate of <1% has the potential to improve soil quality. Salt leaching is required to avoid accumulation when the biochar and lignite‐based amendments are applied. The findings can provide a reference for the application of biochar and lignite‐based amendment in silt loam soil.

Modelling of Soil Moisture Movement and Solute Transport in Parts of Malaprabha Command

Abstract Infiltration is one of the most important hydrological process through which water enters the soil surface and plays a significant role in controlling soil water storage, crop yields, irrigation efficiency and solute entry into the soil profile. In agriculture fields, generally, the top soils are enriched with high organic matter and clay, particularly in black soils that promotes sorption, biological degradation and transformation of contaminants. During the process some of the chemicals applied to farm land, move down with the deep percolating water from the root zone and there are likely chances to pollute the underlying ground water. Such instances are reported by locals in areas dominated by black soils of Malaprabha command area. In order to understand the extent of groundwater contamination through chemical fertilizers, insecticides and manures, two agricultural plots (sugarcane and banana plantation) have been identified in parts of Malaprabha command area covering parts of Saundatti, Ramdurg (Belagavi district) and Nargund taluks (Gadag district). Hydraulic properties such as infiltration and hydraulic conductivity were determined in the field. Soil samples were collected and analysed in the laboratory for texture and porosity. The study indicated that the soils of the region are layered in structure. Further, it is noticed that the coarse textured loamy soil is present below the fine textured soils (such as silty loam or clayey loam). Due to the presence of fine soils at the top, the irrigated water get accumulated and the evaporation takes place relatively faster and results in the accumulation of excess salt. It is also noticed that the layered soils have obvious effects on solute transport and salt accumulation in the clay rich soil layer at the interface. The average salt accumulation (Total Nitrogen) observed in the study area within soil profile is 18.7g/kg. The maximum salt accumulation (21.38 g/kg) occurred in the top layer of sugarcane plots followed by banana plantation (19.85 g/kg). It is also noticed that there are remarkable changes in the interlayered soils with reference to water infiltration characteristics and salt leaching intensities. Study revealed the fact that the properties of the soil profile with a silty loam interlayer is better than with a silty clay loam interlayer.

Development of electrically conductive porous silk fibroin/carbon nanofiber scaffolds

Tissue engineering applications typically require three-dimensional scaffolds which provide the requisite surface area for cellular functions, while allowing transport of nutrients, waste and oxygen to and from the surrounding tissues. Scaffolds need to ensure sufficient mechanical properties to provide mechanically stable frameworks under physiologically relevant stress levels. Meanwhile, electrically conductive platforms are also desirable for the regeneration of specific tissues, where electrical impulses are transmitted throughout the tissue for proper physiological functioning. Towards this goal, carbon nanofibers (CNFs) were incorporated into silk fibroin (SF) scaffolds whose pore size and porosity were controlled during a salt leaching process. In our methodology, CNFs were dispersed in SF due to the hydrogen bond-forming ability of hexafluoro-2-propanol, a fluoroalcohol used as a solvent for SF. Results showed enhanced electrical conductivity and mechanical properties upon the incorporation of CNFs into the SF scaffolds, while the metabolic activities of cells cultured on SF/CNF nanocomposite scaffolds were significantly improved by optimizing the CNF content, porosity and pore size range of the scaffolds. Specifically, SF/CNF nanocomposite scaffolds with electrical conductivities as high as 0.023 S cm−1, tangent modulus values of 260 ± 30 kPa, a porosity as high as 78% and a pore size of 376 ± 53 µm were fabricated for the first time in the literature. Furthermore, an increase of about 34% in the wettability of SF was achieved by the incorporation of 10% CNF, which provided enhanced fibroblast spreading on scaffold surfaces.

A preparation method of porous surface nitrile butadiene rubber with low friction coefficient under water lubrication condition by salt leaching

AbstractNitrile butadiene rubber is widely used in water‐lubricated bearings due to its excellent performance. Generally, the friction coefficient of water‐lubricated rubber bearings typically between 0.05 and 0.18. In this study, a new method for preparing nitrile butadiene rubber with micro‐holes surface is developed by porous leaching with salt as pore forming agent. The possibility of using porous surface to minimize friction and wear of rubber materials is researched. The influence of structural parameters, including the hole density and size (which are determined by salt mass fraction of rubber compounds and salt grain‐sized, respectively) on tribology performances are also evaluated. In a ring‐on‐block test, the optimal parameters of modified rubber achieved a low friction coefficient of 0.008, which reduced by 42% compared with untreated one (0.019) under the same operating condition. It can be expected that the developed method is beneficial to reduce the friction coefficient of rubber‐steel friction pair under water lubricated condition.

Chemical and hydrological controls on salt accumulation in irrigated soils of southwestern U.S

Soil salinization is a global problem affecting approximately 10% of agricultural soils, particularly in irrigated aridlands. This study quantified salt-loading by flood irrigation and soil fertilizers/amendments versus atmospheric deposition, studied controls of solute transport and salt buildup, and evaluated the effectiveness of gypsum application in improving soil sodicity in the arid southwestern United States. Study sites include one natural site and two agricultural sites in fields of dominant crops of the region, a pecan orchard and an alfalfa field near El Paso, Texas. The salt-loading rate in agricultural soils was dominated by the quantity and quality of irrigation waters rather than by dust. Salt loadings by irrigation waters were estimated ~ 306 g Na+ m−2 yr−1, 129 g Ca2+ m−2 yr−1, 361 g Cl− m−2 yr−1, 419 g SO42− m−2 yr−1, and 284 g HCO3− m−2 yr−1, followed by soil amendments. Whereas dust and fertilizer loadings were negligible in agricultural soils. Soil texture variability physically governs water movement and solute transport; coarser soils retained significantly less water than finer soils upon irrigation (p < 0.005) facilitating salt leaching. More salts accumulated around low-permeability layers. Some soils have approached salinity thresholds after only 90 years of cultivation. The Rio Grande river flow is projected to decrease due to reduced snowfall in Colorado, leading to more groundwater of higher salinity, to be used. If ground water were to be the sole water source, the salt loading rate would almost double. Soil amendments temporarily reduce soil sodicity induced by high Na+ concentrations in irrigation water. Their application is needed annually to prevent soil dispersion, to improve infiltration, and to stop even faster salt accumulation. This study highlighted the challenges that the Rio Grande valley in southwestern United States and other irrigated drylands are facing.

ВЛИЯНИЕ ФЕРТИГАЦИИ НА ЗАСОЛЕНИЕ ПОЧВЫ

The salt state has a noticeable effect on the physical and water properties of the soil. That is why the distribution of its water-physical properties along the profile and in space in territories with different soil-climatic, hydrological and hydrochemical conditions should be individual. This is due, on the one hand, to the fact that water is directly involved in the processes of transfer and distribution of salts. On the other hand, the main parameters of the processes of moisture and salt transfer directly depend on the physical properties of the soil, which change under the influence of soluble salts. We have assessed the effect of fertigation on the physicochemical properties of the soil. Four fertigations with different salinity levels were tested. The influence of precipitation on soil desalinization through salt leaching was controlled by comparing changes in soil electrical conductivity during and after the growing season. To measure the studied characteristics, sensors of the 5TE type were used, which independently determine three indicators - the volumetric water content (VWC) by measuring the dielectric constant of the medium based on capacitive / frequency technology, temperature and EC. The stability of soil aggregates was also measured as an indicator of soil degradation. The electrical conductivity of the soil during pre-sowing (or after sowing) treatment was higher than at the end of the growing season. Experimental studies were carried out in the western part of the city of Prague on the campus of the Czech University of Life Sciences with geographic coordinates 50 ° 8'N and 14 ° 23'E. The altitude is 286 m, the average annual air temperature is 9.1 ° C, the amount of precipitation is 495 mm. The soil is loamy chernozem with a content of 22.0 ... 32.5% sand, 39.5 ... 54.0% silt and 22.0 ... 28.0% clay. The limiting field moisture capacity of the soil and the moisture content of stable wilting are 34 and 21%, respectively. It was found that fertigation in the short term is not harmful to the soil in the presence of sufficient precipitation

Evolution of soil salinity and the critical ratio of drainage to irrigation (CRDI) in the Weigan Oasis in the Tarim Basin

Soil salt accumulation and salt leaching are very important issues for a long-term irrigation-dominated oasis with shallow groundwater in arid land. The critical ratio of drainage to irrigation (CRDI) was defined and determined to help the guide drainage and irrigation practices and maintain sustainable oasis agricultural development. This study aimed to identify the soil salinity evolution under long-term irrigation and to determine the threshold of irrigation to drainage with land-use change and groundwater depth by regression, water and salt balance, and geostatistical analysis. The results showed that the soil salinity in 0–20 cm soil depth has decreased greatly in the Weigan Oasis over the past 60 years, with an annual average decrease of 0.68 g·kg−1 in the Weigan Oasis. The soil salt content generally increases from inside to outside of the region and varies from the upperstream to downstream. In the past 30 years, land-use change has caused a sharp reduction in the salinity in the region, and the process of irrigation and drainage has made a decrease in the total salt of the irrigated district of 207.38 × 105 t. Meanwhile, shallow groundwater depth and salinity are the main factors influencing soil salinization in this fluvial oasis. A CRDI is determined to be 8.20% in the Weigan Oasis. In conclusion, our study provides scientific support for the prevention and control of regional soil salinization, as well as a managerial basis for the rational allocation of water resources in long-term irrigation-dominated oasis.

Effect of magnetic water irrigation on the improvement of salinized soil and cotton growth in Xinjiang

To study the effect of magnetic water irrigation on the improvement of different salinized soils and the growth of cotton in Xinjiang, field experiments were conducted in three salinity soils (slight, medium, and heavy salinity soils), with five intensities of magnetized irrigation water (0 GS (CK,G0), 1000 GS (G1), 3000 GS (G3), 4000 GS (G4), and 5000 GS (G5)). Magnetized irrigation water can change the distribution of water and salt in all salinized soils, increase the water holding capacity and salt leaching of soil, and reduce the soil salt contents in the soil profile. It is better for the improvement on slight saline soil was better than on medium and heavy saline soils; the G3 treatment had the strongest effect by increasing soil water content by 33.2%−56.2% and improving the desalination rate by 29.2%−50.4%, compared to the control. Magnetic water irrigation significantly increased cotton growth. A negative relationship was found between soil salt content and plant growth characteristics (plant height, stem diameter, leaf number, leaf area index, and chlorophyll SPAD). Under the different intensities of magnetic water treatment, cotton growth indexes showed the same trends: CK < G1 < G5 < G4 < G3 in all three salinized soils. (3) Compared with the control treatment, magnetic water treatment can increase cotton yield and water use efficiently. Maximum water use efficiency and yields were obtained when the magnetization was 3000GS, in which the water use efficiency was increased by 27.4–42.8%, and the yield was increased by 28.8–31.69% compared with control. In this region, irrigating with magnetized water with 3000GS could improve saline soil quality and cotton growth, especially in slight salinity soil.

Groundwater pollution index (GPI) and GIS-based appraisal of groundwater quality for drinking and irrigation in coastal aquifers of Tiruchendur, South India.

We assessed groundwater pollution index (GPI) and groundwater quality of coastal aquifers from Tiruchendur in South India for drinking and irrigation by evaluating the physico-chemical parameters of 35 samples of mainly Na-Cl type in an area of 470 km2 with respect to the World Health Organization (WHO) standard as well as by estimating different indices such as total hardness (TH), sodium percentage (Na%), magnesium ratio (MR), Kelley's ratio index (KR), potential salinity (PS), Langelier saturation index (LSI), residual sodium carbonate (RSC), sodium adsorption rate (SAR), permeability index (PI), and the irrigation water quality index (IWQI). Minimal influence of aquifer lithology and the dominant influence of evaporation on groundwater chemistry reflected the semi-arid climate of the study area. Electrical conductivity (EC) of about 89% of the samples across 418 km2 exceeded the permissible limit and Ca values of 74% of samples, however, remained within the allowable limit for drinking. More chloride was caused by influx of seawater and salt leaching and higher K was due to excessive fertilizer usage for agriculture. The spatial distribution map created using inverse distance weighting (IDW) method shows that the suitable groundwater is present close to the river basin. GPI values between 0.40 and 4.7, with an average of 1.5, classify insignificant pollution in43% of the study region and the groundwater suitable for drinking purposes. In addition, 17% of the groundwater samples are alsomarginally suitable for drinking. The irrigation water quality indices provided contradictory assessments. Indices of TH, Na%, MR, PS, and LSI suggested 32-95% of the samples as unsuitable for irrigation, whereas the indices of RSC, SAR, and PI grouped 72-100% samples as permissible for irrigation. The IWQI map, however, indicated that the groundwater from more than half of the study area are not apt for irrigation and the groundwater of about one-third of the area could only be applied to salt-resistant plants.

Porous Silk Scaffold Derived from Formic Acid: Characterization and Biocompatibility

Silk porous scaffold possesses 3D space structure for cell adhesion and tissue growth and demonstrates promising applications in biomedical engineering. In this study, a porous silk scaffold was prepared from formic acid, and its morphology, structure, mechanical properties, and biocompatibility were characterized. The preparation process involved silk dissolution in formic acid and salt leaching in water, avoiding widely used organic solvent‐induced crystallization including methanol or ethanol. The resulting porous silk scaffolds showed good pore structure, stable silk II crystalline structure, good mechanical properties, and enhanced cell biocompatibility. Therefore, these findings demonstrate that porous silk scaffold derived from formic acid has great potential applications as 3D scaffold for cell culture and tissue repair.

Soil health changes following transition from an annual cropping to perennial management‐intensive grazing agroecosystem

AbstractManagement‐intensive grazing (MiG) on irrigated, perennial pastures has steadily increased in the western United States due to pressure for reducing public lands grazing, overall declining land available for pasture, and decreasing commodity prices. However, there are still many unknowns regarding MiG and its environmental impact, especially with regards to soil health. Over a 2‐yr period, a study evaluating the change in soil health under a full‐scale, 82‐ha pivot‐irrigated perennial pasture system grazed with ∼230 animal units (AUs) using MiG. Soil analysis included 11 soil characteristics aggregated into the Soil Management Assessment Framework (SMAF), which outputs results for soil biological, physical, nutrient, chemical, and overall soil health indices (SHIs). Over time, positive impacts were observed in the chemical and biological SHI due to decreases in salt content and increases in microbial and enzymatic activities. Soil organic C (SOC) remained unchanged, yet positive biological SHI changes are potential precursors to future SOC increases. The chemical and nutrient SHI increased in the soil surface due to reductions in salt content in conjunction with increased plant‐available soil P, as a result of salt leaching via irrigation and pre‐study inorganic P fertilizer application in conjunction with manure deposition due to MiG, respectively. Finally, a negative impact was also observed in the physical SHI, driven primarily by increasing bulk density due to hoof pressure from cattle grazing. If managed correctly, compaction issues can be avoided, with MiG systems having potential success in supporting grazing while promoting soil health for environmental and economic sustainability.

EFFECTS OF LEACHING ON THE RECLAMATION OF SALINE SOILS AS AFFECTED BY DIFFERENT ORGANIC AND INORGANIC AMENDMENTS

Soil salinity, which poses one of the greatest threats to sustainable crop production worldwide, can be ameliorated through various approaches, such as leaching, mulching, and amendment application. The effects of leaching and amendments on saline soil reclamation have been studied separately, but their interaction is poorly elucidated. Therefore, a column experiment was designed with soils that were subjected to leaching with 2 and 4 pore volume (PV) of water and compared with non-leached soils (NLS) to observe the effects of leaching on saline soil and leachate characteristics under different organic (vermicompost [VC] and wood ash [WA]) and inorganic (zeolite) amendments at two different rates (1 and 2 g 100 g−1) and their combinations. Results revealed that the electrical conductivity (EC) of the soil decreased, whereas the EC of the leachate increased as the PV of water increased. Regardless of the treatments, the concentrations of sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) in the leachate increased. By contrast, their concentrations in the leached soils decreased as the PV of water increased. WA contributed to a significant increase (p < 0.01) in the EC and the concentrations of cations, especially K+ and Ca2+, in the soils and leachates. The higher the rates of the amendment, the greater the increment in the EC and cation concentrations. Incorporating amendments could be important sources of cations, thereby limiting the entry of Na+ into the exchange complex and facilitating leaching with percolating water. The response of spinach (Spinacia oleracea) in terms of yield parameters to 2 PV of leached soils was significantly better than that of NLS, suggesting that soil leaching could significantly influence plant functioning in highly saline soils. This study suggested that the irrigation of saline soils under different organic and inorganic amendments before cultivation might affect salt leaching and soil nutrient dynamics, thereby influencing plant growth and yield.

A study on interannual change features of soil salinity of cotton field with drip irrigation under mulch in Southern Xinjiang.

The drip irrigation under mulch has become one of significant supporting technologies for cotton industry development in Xinjiang, and has shown the good economic and ecological benefits. With the rapid development of society and economy in Southern Xinjiang, the conventional mode of large-quota winter and spring irrigation, salt leaching and alkali decreasing is difficult to support sustainable development of land and water resources in Southern Xinjiang. This study tries to adjust soil moisture and salt content regulation mode of massive water salt leaching and drip irrigation under mulch in the non-growing period of cotton field in Southern Xinjiang, explores interannual soil salinity change features of drip irrigation cotton field without winter and spring irrigation, and provides experimental basis for drip irrigation technology under mulch which can reduce and exempt cotton irrigation in winter and spring. According to ET0, the dual-factor complete combination experiment involving 3 irrigating water quotas (I1, I2, I3) and 2 irrigation times (T12, T16) was designed, and 6 treatments were involved in total(I1T12,I2T12,I3T12,I1T16,I2T16 and I3T16). The investigation results of four-year (2012–2015) field positioning experiment showed that, under the condition of “germination under drip irrigation” without winter and spring irrigation, increasing irrigation quota and irrigation times could lower 0-100cm soil salinity accumulation, but the soil salinity accumulation degree was 40-100cm, and less than 0-30cm. In the seedling stage, bud stage, blossom and boll-forming stage, and boll opening stage, the average salinity of 0-100cm soil increased by 39.81%, 31.91%, 26.85% and 29.47%, respectively. Increasing irrigation quota and irrigation times could ease interannual soil salinity accumulation degree of cotton field with drip irrigation under mulch, without winter and spring irrigation. 0-100cm soil salinity before sowing was related to the irrigation quota of cotton in the growing stage of the last year. The larger the irrigation quota was, the smaller the soil salinity before sowing would be. The accumulation amount of soil salinity at the end of growing stage under different treatments was lower than that before sowing. The drip irrigation of cotton under mulch in the growing stage could effectively regulate soil salinity distribution and space-time migration process in the growing stage of cotton. Compared with the beginning of 2012, 0-100cm average soil salinity under 3 irrigation quotas (I1, I2, I3) was 33.66%, 5.60% and 1.24%, respectively. Salt accumulating rates under 12 irrigations and 16 irrigations were 20.66% and 6.33%, respectively. The soil had the risk of salinization when the “germination under drip irrigation” without winter and spring irrigation was used. Such results can provide the reference for prevention and treatment of soil moisture and salt content of cotton field with drip irrigation under mulch in the arid region.

Temperature effect on the porosity of hydroxyapatite scaffolds and its use in tissue engineering

The search for a suitable bone replacement is of great importance due to the difficulty to use autologous transplants. Hence, the objective of this work is to compare the temperature effect on the porosity and average pore diameter of hydroxyapatite porous scaffolds fabricated by the salt leaching method. Hydroxyapatite porous scaffolds fabricated by the salt leaching technique were sintered from ~150 to 1000 °C. Synthesized hydroxyapatite was assessed by X-ray diffraction (XRD). Zeta potential at different temperatures was evaluated. Specimens were characterized using scanning electron microscopy (SEM) and Raman analysis. The results showed that significant porosity (57%) and pore size (49 µm) occurred with a thermal treatment above ~ 850 °C for scaffolds that were pre-sintered at 1050 °C.

Mechanical properties of porous photo-crosslinked poly(trimethylene carbonate) network films

Tissue engineering scaffolds require high porosity and optimized pore sizes to allow cell seeding, -adhesion and –proliferation, and tissue ingrowth. However, porosity affects the mechanical properties of the scaffolds to a large extent. Usually, these properties are only assessed in compression experiments. Here we investigate the effect of the pore characteristics on the tensile properties of photo-crosslinked poly(trimethylene carbonate) network films that were prepared by a method involving salt leaching and by stereolithography. Particulate leaching is a conventional method to obtain porous structures, while stereolithography is an additive manufacturing method that provides the benefit of control over pore architecture and allows for complex geometries to be prepared.The tensile properties of the porous network films were indeed much affected by porosity. The elasticity modulus of porous network films decreased with increasing porosity. This decrease appears to be independent of pore size. For a given porosity, the values of the elasticity moduli, maximum tensile strengths and toughness of porous poly(trimethylene carbonate) network films prepared by stereolithography were slightly higher than those of porous network films prepared by the salt leaching method. This may be due to different amounts of diluent used while preparing the networks by the different methods. In addition, the presence of salt in the material during crosslinking appears to result in a less efficient crosslinking process.