Responses of runoff and sediment yield to slope length and gravel content of Lou soil engineering accumulation slope in Guanzhong region, Northwest China.

With the economic development, a large number of engineering accumulation bodies with Lou soil as the main soil type were produced in Guanzhong area, Northwest China. We examined the characteristics of runoff and sediment yield of Lou soil accumulation bodies with earth (gravel content 0%) and earth-rock (gravel content 30%) under different rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1) and different slope lengths (3, 5, 6.5, 12 m) by the simulating rainfall method. The results showed that runoff rate was relatively stable when rainfall intensity was 1.0-1.5 mm·min-1, while runoff rate fluctuated obviously when rainfall intensity was 2.0-2.5 mm·min-1. The average runoff rate varied significantly across different rainfall intensities on the same slopes, and the difference of average runoff rate of the two slopes was significantly increased with rainfall intensity. Under the same rainfall intensity, the difference in runoff rate between the slope lengths of the earth-rock slope was more obvious than that of the earth slope. When the slope length was 3-6.5 m, flow velocity increased rapidly at first and then increased slowly or tended to be stable. When the slope length was 12 m, flow velocity increased significantly. In general, with the increases of rainfall intensity, inhibition effect of gravel on the average flow velocity was enhanced. When rainfall intensity was 2.5 mm·min-1, the maximum reduction in the average flow velocity of earth-rock slope was 61.5% lower than that of earth slope. When rainfall intensity was less than 2.0 mm·min-1, sediment yield rate showed a trend of gradual decline or stable change, while that under the other rainfall intensities showed a trend of rapid decline and then fluctuated sharply. The greater the rainfall intensity, the more obvious the fluctuation. There was a significant positive correlation between the average sediment yield rate and runoff parameters, with the runoff rate showing the best fitting effect. Among the factors, slope length had the highest contribution to runoff velocity and rainfall erosion, which was 51.8% and 35.5%, respectively. This study can provide scientific basis for soil and water erosion control of engineering accumulation in Lou soil areas.

Revegetation-induced changes in vegetation diversity improve soil properties of gully heads.

Revegetation is among the most efficient methods to improve gully headcut erosion. However, the influencing mechanism of revegetation on the soil properties of the gully head (GHSP) is still unclear. Thus, this study hypothesized that the variations in the GHSP were influenced by vegetation diversity during nature revegetation, and the influence pathways were mainly root traits, aboveground dry biomass (ADB), and vegetation coverage (VC). We studied six grassland communities of the gully head with different natural revegetation ages. The findings showed that the GHSP were improved during 22-year revegetation. The interaction effect of vegetation diversity, roots, aboveground dry biomass, and vegetation coverage on the GHSP was 43 %. In addition, vegetation diversity significantly explained >70.3 % of the changes in the root traits, ADB, and VC of the gully head (P < 0.05). Therefore, we combined vegetation diversity, roots, ADB, and VC to establish the path model to explain the GHSP changes, and the goodness of fit of the model was 82.3 %. The results showed that the model explained 96.1 % of the variation in the GHSP, and the vegetation diversity of the gully head affected the GHSP through roots, ADB, and VC. Therefore, during nature revegetation, vegetation diversity dominates the improvement of the GHSP, which has important significance for designing an optimal vegetation restoration strategy to control gully erosion.

Responses of biomass accumulation and nutrient utilization along a phosphorus supply gradient in Leymus chinensis.

Phosphorus (P) deficiencies are widespread in calcareous soils. The poor availability of nitrogen (N) and P in soils often restricts crop growth. However, the effects of P addition on plant growth and plant nutrient transport changes during the establishment of Leymus chinensis fields in Xinjiang are not clear. We investigated the responses of Leymus chinensis biomass and nutrient absorption and utilization to changes in soil N and P by adding P (0, 15.3, 30.6, and 45.9 kg P ha-1 year-1) with basally applied N fertilizer (150 kg N ha-1 year-1). The results showed that (a) Principal component analysis (PCA) of biomass, nutrient accumulation, soil available P, and soil available N during the different periods of Leymus chinensis growth showed that their cumulative contributions during the jointing and harvest periods reached 95.4% and 88%, respectively. (b) Phosphorus use efficiency (PUE) increased with the increase of P fertilizer gradient and then decreased and the maximum PUE was 13.14% under moderate P addition. The accumulation of biomass and nutrients in Leymus chinensis can be effectively improved by the addition of P fertilizer at 30.6 kg ha-1. Different P additions either moderately promoted or excessively inhibited Leymus chinensis growth and nutrient utilization.

Vegetation restoration restricts rill development on dump slopes in coalfields.

Severe rill erosion on dump slopes poses a great threat to the ecological environment in mining areas. Vegetation restoration is an effective measure for controlling soil erosion on dump slopes. However, few studies have identified the long-term influence of vegetation restoration on rill development on dump slopes. Therefore, we investigated the rill development characteristics of dump slopes with three typical restoration models (CK: natural restoration; ED: Elymus dahuricus; and AO: Artemisia ordosica) and three recovery time (1 y, 3 y and 5 y). The results showed that vegetation adequately controlled rill erosion on dump slopes. ED and AO could effectively control the development of rills with widths >15 cm and depths of 10-20 cm. ED vegetation restoration inhibited the development rill morphology and network better than AO. The rill erosion modulus of the ED slope and AO slope decreased by 76.29%-90.77% and 46.66%-61.49%, respectively, compared with that of natural restoration slopes with recovery time of 1 y, 3 y, and 5 y. ED controlled rill erosion better than AO, but this effect gradually weakened with recovery time. Vegetation coverage contributed 34.99% of the total variation in rill morphology and was the main factor affecting the development of rills on dump slopes. Furthermore, vegetation coverage had a more important role in controlling rill development than did the root system on dump slopes. This study provides valuable information for optimizing vegetation construction for soil loss control on dump slopes.

[Characteristics of soil anti-scouribility in gully head wall of grass-covering on the gullied Loess Plateau, Northwest China]. / 黄土高塬沟壑区草地沟头立壁土壤抗冲性特征.

Vegetation restoration in the Chinese Loess Plateau has significantly changed soil erosion process of gully head wall. In order to investigate the characteristics and controlling factors of soil anti-scour properties of gully head covered by grasses, we carried out indoor undamaged soil trench scouring tests. By using barren gully head as the control, the physical and chemical properties and anti-scouring characteristics of soil in different soil layers (0-10, 10-20, 20-40, 40-60, 60-80, 80-100 cm) of the vertical wall of gully with grass cover were analyzed. The results showed that water-stable aggregate content and cohesion in barren and grass-covering gully head decreased with soil depth. Soil organic matter content and soil anti-scouribility coefficient in barren gully head decreased with soil depth, while the two indicators for gully head covered by grass increased firstly and then decreased with soil depth, with the maximum value (24.30 g·kg-1 and 58.86 L·g-1) in 10-20 cm soil layer. Meanwhile, the soil anti-scouring coefficient in each soil layer of grass-covering gully head was 1.7-9.3 times of that in soil layer of barren gully head. Soil organic matter content, water-stable aggregate content, cohesion and root length density all presented significantly positive correlation with soil anti-scouribility, among which soil organic matter content had the highest coefficient (r=0.98). Results of this study might provide basic data for the study of headcut erosion mechanism in Loess Plateau gully region, and scientific basis for effective control of soil and water loss in this region.

[Effects of gravel content on runoff and sediment yield on Lou soil engineering accumulation slopes under simulated rainfall conditions.] / æ¨¡æ‹Ÿé™é›¨æ¡ä»¶ä¸‹ç ¾çŸ³å«é‡å¯¹å¡¿åœŸå·¥ç¨‹å †ç§¯ä½“å¡é¢äº§æµäº§æ²™çš„å½±å“.

To investigate the effects of gravel content on runoff and sediment yield on Lou soil accumulation slopes, we conducted indoor simulation rainfall experiments and examined the characteristics of runoff and sediment yield on accumulation slopes with five gravel contents (10%, 20%, 30%, 40%, 50%) under four rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1), with a no gravels slope as control. The average runoff rate under different test conditions ranged from 2.18 to 13.07 L·min-1. The average runoff rate was the maximum under the gravel content of 10% (or 20%) and the minimum under the 50% gravel content. The average flow velocity ranged from 0.06 to 0.22 m·s-1. The variation of flow velocity was complex. The smaller the gravel content, the larger the range of variation and the coefficient of variation. The average flow velocity reached the maximum when the gravel content was 10%. The presence of gravel effectively inhibited the sediment yield, and the sediment reduction benefit reached 84.2%. The rainfall intensity had more influence on the average sediment yield rate than gravel content. Results of partial correlation analysis showed that gravel content was significantly negatively correlated with the ave-rage runoff rate, the average flow velocity, and the average sediment yield rate. The relationships between the ave-rage sediment yield and the average runoff rate, the average flow velocity, and their interaction were all extremely significant linear functions, with the strongest relationship between the average sediment yield and the average runoff rate. This study could provide references for the control of soil erosion and the establishment of erosion models for engineering accumulations in Lou soil areas.

Smart assembly behaviors of hydroxypropylcellulose-graft-poly(4-vinyl pyridine) copolymers in aqueous solution by thermo and pH stimuli.

Thermo- and pH-sensitive graft copolymers, hydroxypropylcellulose-graft-poly(4-vinyl pyridine) (HPC-g-P4VP), were synthesized via atom transfer radical polymerization (ATRP) and characterized. The thermo- and pH-induced micellization and stimuli-responsive properties of HPC-g-P4VP graft copolymers in aqueous solution were investigated by transmittance, (1)H NMR, dynamic light scattering (DLS), and so on. For the pH-induced micellization, the P4VP side chains collapse to form the core of the micelles, and the HPC backbones stay in the shell to stabilize the micelles. In the case of thermoinduced micellization, the HPC backbones collapse to form the core of the micelles that was stabilized by the P4VP side chains in the shell upon heating. What's more, the cloud point of the HPC-g-P4VP copolymers in the aqueous solution could be finely tuned by changing the length of P4VP side chains or the pH values. In acidic water, the longer the side chains, the higher the cloud point. For those HPC-g-P4VP copolymers with short side chains, for example, HPC0.05-g-P4VP(3), the lower pH correlates a higher cloud point. The thermo- or pH-induced micelles also have the pH- or thermosensitivity due to their P4VP or HPC shells.

Self-assembly and dual-stimuli sensitivities of hydroxypropylcellulose-graft-poly(N,N-dimethyl aminoethyl methacrylate) copolymers in aqueous solution.

The self-assembly and pH- and thermo-sensitivities properties of hydroxypropyl cellulose-graft-poly(N,N-dimethyl aminoethyl methacrylate) (HPC-g-PDMAEMA) copolymers in aqueous solutions were investigated by transmittance, dynamic light scattering (DLS), and (1)H NMR spectroscopy. Micelles with different structure can be formed by varying either pH value or temperature. At low pH, e.g., 3.0, the HPC backbone of the copolymer collapse to form the core of micelles stabilized with protonated PDMAEMA side chains on the surface of the micelles upon heating. At the medium pH, e.g., 8.1, both HPC backbone and PDMAEMA side chains collapse upon heating to form unstable aggregates. At high pH, e.g., 12.3, PDMAEMA side chains collapse first to form the core of micelles stabilized with HPC chains upon heating. Further heating the copolymer solution at this pH leads to the aggregation of the micelles due to the collapse of the shell HPC chains. The thermal sensitivity of the HPC-g-PDMAEMA copolymers is reversible.

[Runoff-sediment relationship and erosion dynamic characteristics for two types of engineering deposits under rainfall condition]. / é™é›¨æ¡ä»¶ä¸‹ä¸¤ç§åœŸå£¤ç±»åž‹å·¥ç¨‹å †ç§¯ä½“å¡é¢æ°´æ²™å ³ç³»ä¸Žä¾µèš€åŠ¨åŠ›ç‰¹å¾.

The engineering deposits produced by the increasing frequency of production and construction activities are the main source of man-made soil erosion. In this study, we examined the change of runoff-sediment relationship and erosion hydrodynamic characteristics with the engineering deposits of aeolian sandy soil and red soil, based on simulated rainfall experiments with different gravel contents (0, 10%, 20%, 30%) and rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1). The results showed that the sediment yield rate of the aeolian sandy soil deposits gradually increased with the duration of rainfall. The sediment yield rate of red soil deposits under 1.0 mm·min-1 rainfall intensity increased first and then gradually stabilized. Under other rainfall densities, there was a trend of fluctuation after rapid decline, the greater the rainfall intensity and the smaller the gravel content, the more intense the fluctuation. When the gravel content was 0 and 10%, there were rills erosion on the slope surface of aeolian sandy soil accumulation, and the sediment yield rate of rill development stage was 6.74-57.40 times of that of the sheet erosion stage. The erosion process of red soil deposits could be divided into two stages: the loose particle erosion and the soil-rock erosion stage. The sediment yield rate of the loose particle erosion stage was 1.05-3.49 times that of the soil-rock erosion stage. In general, the sediment yield rate of two soil deposits increased with increasing rainfall intensity. The sediment yield rate fluctuated with the increases of gravel content at 1.0 and 1.5 mm·min-1, with a decreasing trend under >1.5 mm·min-1. The sediment yield rate of aeolian sandy soil deposits was 1.45-4.14 times of that of red soil deposits under the same rainfall and gravel content conditions. During the erosion process of aeolian sandy soil deposits, the runoff-sediment relationship changed from low sediment concentration to high sediment concentration, while there was a reverse relationship for red soil deposits. During the high sediment concentration period, the increasing rate of the sediment yield rate of aeolian sandy soil deposits was 1.94-37.60 times of that of red soil deposits. For low sediment concentration period, the decreasing rate of the sediment yield rate of red soil deposits was 1.40-21.30 times of that of aeolian sandy soil deposits. In general, the runoff power was better than the runoff shear force in describing the erosion dyna-mics of these two types of deposits. The critical runoff power increased with increasing gravel content. The critical runoff power of aeolian sandy soil deposits during the rill erosion stage (0.02-0.04 W·m-2) was two times of that of the sheet erosion stage, while the critical stream power was lower than that of the red soil deposits. These results provide a scientific reference for modelling soil erosion processes for engineering deposits.

[Erosion morphology and the characteristics of runoff and sediment yielding in platform-slope system of opencast coal mine]. / 露天矿排土场平台-边坡系统侵蚀形态及径流产沙特征.

In the open pit, runoff from the platform is large discharge and rapid afflux, which often results in serious gully erosion of dump slope. The study of erosion process under catchment conditions of the platform-slope system is still backward. In this study, field scouring experiments were conducted to investigate runoff characteristics and sediment yield processes of the platform-slope system under different flow discharges (48, 60, 72 and 84 L·min-1). Our results showed that rill erosion dominated the platform-slope system under the flow discharge of 48 L·min-1, and gully was formed under 60-84 L·min-1. The flow velocity of the platform and the slope showed an abrupting-fluctuating-stable trend with the duration of discharge. The flow velocity of the platform was smaller than that of the slope, with the magnitude of reduction at 8.3%-67.1%. The highest flow velocity appeared on the up-slop/down-slope, being 18.5%-44.6% higher than that of the middle-slope. In general, the sediment yield rate of the platform and the slope varied with the duration of discharge, with the sediment yield rate of the slope being 17.4 times as that of the platform. The ratio of gully width to depth showed substantial difference between the platform and slope. The platform generally had the largest ratio than the slope. For the slope, the largest ratio appeared on the middle-slop/down-slope, being 1.36-1.93 times as that of the up-slope. The morphology of rill and gully along the platform to down-slope presented in the form of "wide and shallow-narrow and deep-wide and shallow". Rill erosion mainly concentrated in the platform and the middle slope under the flow discharge of 48 L·min-1, contributed 29.9% and 26.8% of the total erosion volume, respectively. When the flow discharge increased to 60-84 L·min-1, the largest average across-section areas (1083.25-1737.86 cm2) formed on the up-slope accounted for 36.1%-44.7% of the total erosion volume. Our results provided evidence for modelling soil and water erosion of the platform-slope system in opencast coal mine.

[Differences in hydraulic erosion processes of the earth and earth-rock Lou soil engineering accumulation in the Loess Region]. / é»„åœŸåŒºåœŸè´¨ä¸ŽåœŸçŸ³è´¨å¡¿åœŸå †ç§¯ä½“æ°´åŠ›ä¾µèš€è¿‡ç¨‹å·®å¼‚.

An indoor rainfall simulation experiment was conducted to examine the hydrodynamic characteristics, erosion characteristics, and erosion dynamics mechanisms of earth (excluding gra-vel) and earth-rock (gravel mass fraction 30%) Lou soil engineering accumulation in the Loess area across different rainfall intensities and slope gradients. Results showed that the presence of gravel changed the hydrodynamic characteristics of the engineering accumulation slope. The flow velocity, froude number, unit stream power, and unit energy of water-carrying section of the earth-rock slope were 1.7%-49.7%, 6.7%-60.6%, 2.0%-44.6% and 1.0%-26.7% lower than those of the earth slope, while the Manning roughness coefficient and runoff shear stress of the earth-rock slope were 6.2%-169.4% and 5.7%-79.3% higher than those of the earth slope respectively. Under the intensity of 2.0 and 2.5 mm·min-1, erosion rate of the earth-rock slope was 26.2%-89.9% lower than that of earth slope. The gravel significantly reduced slope erosion of the Lou soil engineering accumulation. Erosion rate and hydrodynamic parameters of the two accumulations were linearly related. The erodibility parameters of earth-rock slope were 56.1%-73.3% lower than that of earth slope. In the critical hydrodynamic parameters, runoff shear stress of earth-rock slope was 11.1% higher, while the stream power, unit stream power and unit energy of water-carrying section were 25.4%, 64.0% and 5.0% lower than those of the earth slope, respectively. The existence of gravel controlled rainfall erosion process on the slope of the engineering accumulation to some extent.

Comparison of aerobic atrazine degradation with zero valent aluminum and zero valent iron.

This study systematically compared the degradation of atrazine (ATR) with aerobic zero-valent aluminum (ZVAl/Air) and zero-valent iron (ZVI/Air) systems. By comparing the ATR degradation curves and rate in the ZVAl/Air and the ZVI/Air systems, a significant induction period was observed in the ZVAl/Air system, and the pseudo-first-order rate constant of ATR degradation in the second stage by ZVAl was 6.4 times faster than that by ZVI. The differences in ATR degradation patterns of the two systems stemmed from the different redox nature and electrical conductivity of aluminum (oxide) and iron (oxide). Reactive oxygen species measurement and electron spin spectra analysis indicated that more hydroxyl radical was generated through molecular oxygen activation in the ZVAl/Air system, leading to enhanced ATR degradation in the ZVAl/Air process. By analyzing the intermediates of atrazine degradation, we found that ATR underwent an oxidative dealkylation and hydroxyl-dechlorination degradation pathway, and the low toxicity cyanuric acid was the final product in both systems. However, aluminum ions released in the ZVAl/Air system exceeded the regulated standard value, which might cause environmental pollution. Finally, the pros and cons of potential environmental remediation of the ZVAl/Air and ZVI/Air processes were evaluated.

Gelation of Na-alginate aqueous solution: A study of sodium ion dynamics via NMR relaxometry.

Sodium alginate (SA) hydrogels have a wide range of applications including tissue engineering, drug delivery and formulations for preventing gastric reflux. The dynamics of sodium ions during the gelation process of SA solution is critical for clarification of the gelation procedure. In this work, nuclear magnetic resonance (NMR) relaxometry and pulsed-field-gradient (PFG) NMR diffusometry were used to investigate the dynamics of the sodium ions during the gelation of SA alginate. We find that sodium ions are in two different states with the addition of divalent calcium ions, corresponding to Ca2+ crosslinked and un-crosslinked regions in the hydrogels. The sodium ions within the un-crosslinked regions are those released from the alginate chains without Ca2+ crosslinking. The relative content of sodium ions within the Ca2+ crosslinked regions decreased with the increase in the content of calcium ions in the system. The relaxation time T2 of sodium ions within the Ca2+ crosslinked and un-crosslinked regions shift to shorter and longer relaxation time with the increase in concentration of calcium ion, which indicates the closer package of SA chains and the larger space for the diffusion of free sodium ions. This work clarifies the dynamics of 23Na+ in a calcium alginate gel at the equilibrium state.

Thermal sensitivity and protein anti-adsorption of hydroxypropyl cellulose-g- poly(2-(methacryloyloxy) ethyl phosphorylcholine).

Zwitterionic graft copolymers, hydroxypropyl cellulose graft poly(2-(methacryloyloxy) ethyl phosphorylcholine) (HPC-g-PMPC) with well-defined architecture were synthesized by atom transfer radical polymerization (ATRP). The self-assembly behaviors and thermal sensitivity of HPC-g-PMPC copolymers and their correlations with graft density and side chain length were investigated in details. HPC-g-PMPC copolymers can self-assemble into spherical aggregate structure above the critical aggregation concentration (CAC) at room temperature. Meanwhile, the size of the aggregates mainly depended on the graft density. The obtained aggregates were thermal sensitive and their low critical solution temperature (LCST) was efficiently regulated by varying the graft density. Above the LCST, the aggregates were transferred into aggregates with core-shell structure, in which the HPC rich core was stabilized by the PMPC rich shell. The interaction between the HPC-g-PMPC aggregates and BSA was investigated. The results indicated that the anti-adsorption of BSA on the aggregates surface depended on the length and graft density of the PMPC zwitterionic side chains.

Reversible redox activity of ferrocene functionalized hydroxypropyl cellulose and its application to detect H2O2.

Novel ferrocene functionalized hydroxypropyl cellulose (HPC-Fc) were prepared by azide-alkyne cycloaddition and characterized. HPC-Fc exhibits an excellent reversible redox activity and could establish amazing electron transfer ability between enzyme and electrode. HPC-Fc and horseradish peroxidase (HRP) were coated on a platinized carbon electrode to prepare an amperometric biosensor for hydrogen peroxide (H2O2) detection. The amperometric response was measured as a function of H2O2 concentration at a fixed potential of 0.35V in 100mM phosphate buffer solution (pH 7.0). The novel biosensor exhibits a fast linear response toward H2O2 in the range of 0.1-8µM with sensitivity of 4.21nA/µM. Moreover, the enzyme assays measured by the spectrophotometer method confirm that abundant hydroxyl groups of HPC backbones are conductive for HRP to maintaining or even enhancing their activity. The redox active HPC-Fc with the unique properties of both ferrocene and cellulose is a good candidate for biosensor applications.

Bacterial Cellulose Supported Gold Nanoparticles with Excellent Catalytic Properties.

Amidoxime surface functionalized bacterial cellulose (AOBC) has been successfully prepared by a simple two-step method without obviously changing the morphology of bacterial cellulose. AOBC has been used as the reducing agent and carrier for the synthesis of gold nanoparticles (AuNPs) that distributed homogeneously on bacterial cellulose surface. Higher content in amidoxime groups in AOBC is beneficial for the synthesis of AuNPs with smaller and more uniform size. The AuNPs/AOBC nanohybrids have excellent catalytic activity for reduction of 4-nitrophenol (4-NP) by using NaBH4. It was found that catalytic activity of AuNPs/AOBC first increases with increasing NaBH4 concentration and temperature, and then leveled off at NaBH4 concentration above 238 mM and temperature above 50 °C. Moreover, AuNPs with smaller size have higher catalytic activity. The highest apparent turnover frequency of AuNPs/AOBC is 1190 h(-1). The high catalytic activity is due to the high affinity of 4-NP with AuNPs/AOBC and the reduced product 4-aminophenol has good solubility in water in the presence of AuNPs/AOBC. The catalytic stability of the AuNPs/AOBC was estimated by filling a fluid column contained AuNPs/AOBC and used for continuously catalysis of the reduction of 4-NP by using NaBH4. The column works well without detection of 4-NP in the eluent after running for more than two months, and it is still running. This work provides an excellent catalyst based on bacterial cellulose stabilized AuNPs and has promising applications in industry.

Dissolution mechanism of cellulose in N,N-dimethylacetamide/lithium chloride: revisiting through molecular interactions.

Understanding the interactions between solvent molecules and cellulose at a molecular level is still not fully achieved in cellulose/N,N-dimethylacetamide (DMAc)/LiCl system. In this paper, cellobiose was used as the model compound of cellulose to investigate the interactions in cellulose/DMAc/LiCl solution by using Fourier transform infrared spectroscopy (FTIR), (13)C, (35)Cl, and (7)Li nuclear magnetic resonance (NMR) spectroscopy and conductivity measurements. It was found that when cellulose is dissolved in DMAc/LiCl cosolvent system, the hydroxyl protons of cellulose form strong hydrogen bonds with the Cl(-), during which the intermolecular hydrogen bonding networks of cellulose is broken with simultaneous splitting of the Li(+)-Cl(-) ion pairs. Simultaneously, the Li(+) cations are further solvated by free DMAc molecules, which accompany the hydrogen-bonded Cl(-) to meet electric balance. Thereafter, the cellulose chains are dispersed in molecular level in the solvent system to form homogeneous solution. This work clarifies the interactions in the cellulose/DMAc/LiCl solution at molecular level and the dissolution mechanism of cellulose in DMAc/LiCl, which is important for understanding the principle for selecting and designing new cellulose solvent systems.

An effect of alginate on the stability of LDH nanosheets in aqueous solution and preparation of alginate/LDH nanocomposites.

Nanosheets under 10nm in thickness are obtained by exfoliating layered double hydroxide (LDH) in formamide. The LDH nanosheets are dispersed and stabilized in an alginate aqueous solution after removing formamide by water washing and ultracentrifugation. During the water washing stage LDH nanosheets can be prevented from restacking by electrostatic stabilization of the surface of LDH sheets through the adsorption of alginate. Alginate/LDH nanocomposites can be prepared by drying the dispersion, and sandwich-like structures in the nanocomposites are formed with two alginate layers contained between two LDH sheets. LDH nanosheets in the dried alginate/LDH nanocomposites can be re-dispersed in water. The thermal stability of alginate in the nanocomposite is increased by LDH. Alginate membranes containing this layered nanocomposite can be prepared. The addition of LDH into the alginate matrix leads to an increase in the mechanical properties of the nanocomposite.

Controlled release of liposome-encapsulated Naproxen from core-sheath electrospun nanofibers.

Naproxen (NAP) loaded nanofibers of different structures have been successfully prepared by electrospinning. The structures of the nanofibers are NAP and cellulose acetate (CA) mixed nanofibers (NF-1), nanofibers with NAP/CA mixed core and CA sheath (NF-2), and NAP loaded liposomes and sodium hyaluronate (HA-Na) mixed core with CA sheath (NF-3). The structure and morphology of the nanofibers were characterized and the drug release behaviors were investigated. It was found that NAP can disperse in the HA-Na or CA matrix in molecular level without formation of NAP crystals and dimers. The drug release behaviors of NF-1 and NF-2 show a non-Fickian diffusion mechanism, while the NF-3 shows a specific drug release behavior with a burst release within 8h followed by a sustained drug release for 12 days. The particular two-stage drug release behavior of NF-3 nanofibers offers the materials promising applications as wound dressing materials.

Ultrathin core-sheath fibers for liposome stabilization.

Ultrathin core-sheath fibers with small unilamellar vesicles (SUVs) in the core were prepared by coaxial electrospinning. SUVs/sodium hyaluranate (HA-Na)/water and polyvinylpyrrolidone (PVP)/ethanol solutions were used as core and sheath fluid in electrospinning, respectively. The ultrathin fibers were characterized by scanning and transmission electron microscopy (SEM and TEM) and laser scanning confocal microscopy (LSCM). The SUVs were successfully encapsulated in the core HA-Na matrix of the ultrathin fibers and are in the elliptic shape. The SUVs encapsulated in the core matrix of the ultrathin fibers have an excellent stability. The SUVs embedded in the ultrathin fibers are stable. When the ultrathin fibers were re-dissolved in water after one-month storage at room temperature, the rehydrated SUVs have the similar size and size distribution as the as-prepared SUVs. The liposome-loaded ultrathin fiber mats have the promising applications in wound healing materials.