Creaming Layers of Nanocellulose Stabilized Water-Based Polystyrene: High-Solids Emulsions for 3D Printing

Oil-in-water emulsions stabilized using cellulose nanofibrils (CNF) form extremely stable and high-volume creaming layers which do not coalesce over extended periods of time. The stability is a result of the synergistic action of Pickering stabilization and the formation of a CNF percolation network in the continuous phase. The use of methyl cellulose (MC) as a co-emulsifier together with CNF further increases the viscosity of the system and is known to affect the droplet size distribution of the formed emulsion. Here, we utilize these highly stable creaming layer systems for in situ polymerization of styrene with the aim to prepare an emulsion-based dope for additive manufacturing. We show that the approach exploiting the creaming layer enables the effortless water removal yielding a paste-like material consisting of polystyrene beads decorated with CNF and MC. Further, we report comprehensive characterization that reveals the properties and the performance of the creaming layer. Solid-state NMR measurements confirmed the successful polymerization taking place inside the nanocellulosic network, and size exclusion chromatography revealed average molecular weight (Mw) of polystyrene as approximately 700,000 Da. Moreover, the amount of the leftover monomer was found to be less than 1% as detected by gas chromatography. The dry solids content of the paste was ∼20% which is a significant increase compared to the solids content of the original CNF dispersion (1.7 wt%). The shrinkage of the CNF, MC and polystyrene structures upon drying—an often-faced challenge—was found to be acceptable for this composite containing highly hygroscopic biobased materials. At best, the two dimensional shrinkage was no more than ca. 20% which is significantly lower than the shrinkage of pure CNF being as high as 50%. The paste, which is a composite of biobased materials and a synthetic polymer, was demonstrated in direct-ink-writing to print small objects. With further optimization of the formulation, we find the emulsion templating approach as a promising route to prepare composite materials.

Aramid Nanofibers Reinforced Cellulose Paper-Based Lithium-Ion Battery Separator with Improved Safety and Cycling Stability

Commercial polyolefin separators with poor electrolyte wettability and inferior thermal stability have hampered the development of advanced lithium-ion batteries (LIBs) due to their unsatisfied electrochemical performance and severe safety hazards. Herein, a novel paper-based composite separator composed of electrolyte-affinitive cellulose fibers (CFs) and thermally stable aramid nanofibers (ANFs) was successfully fabricated through the traditional papermaking method. It was found that the incorporation of ANFs played crucial roles in improving the defects of pure CF separator such as large-sized pores, low mechanical strength and high flammability. Specifically, the CF/ANF composite separator with 20 wt.% ANFs (CF/ANF-20) possessed narrow micropores, satisfied tensile strength (33MPa), excellent thermal resistance (without dimensional shrinkage up to 200 °C) and flame retardancy, greatly enhancing the safe operation of battery. In addition, benefiting from the highly porous structure and exceptional electrolyte affinity of CF separator, the CF/ANF-20 composite separator exhibited appropriate porosity and superior electrolyte wettability, which brought about a high electrolyte uptake (157%), thus endowing it with better ionic conductivity (0.75 mS cm−1) and lower interfacial resistance than that of commercial polypropylene (PP) separator. Accordingly, the LiFePO4/Li half cells using CF/ANF-20 separator delivered outstanding rate capability and stable cycling performance. All results indicate that the CF/ANF-20 separator with great balance between the electrochemical performance and safety is an intriguing candidate for advanced LIBs.

Dimensional stability of alginate molds scanned at different storage times

The aim of this study was to evaluate the precision and accuracy of molds made with four commercial brands of alginate scanned at different times using digital model analysis. Eighty molds of a standard Typodont were made using 4 types of alginate (CCC: Cavex Color Change; IA: Identic Alginate; HY5: Hydrogum 5 and JP: Jeltrate Plus). The molds were scanned at four times: immediately (T1), 24h (T2), 72h (T3) and 120h (T4) after molding. Measurements were taken in three dimensions: anteroposterior, transverse and vertical. Significant differences in dimensional changes were noted between the materials over time (p<0.05). Anteroposterior dimensional variation was noted between times, especially for IA and JP. For transverse and vertical variables, a difference was found between the groups, especially at 24 h, 72 h and 120 h. CCC presented significant dimensional shrinkage only at T120 (transverse). IA and JP presented larger dimensional distortions in the vertical measurements. The molding materials used were not dimensionally stable when evaluated after 120 hours of molding. However, such evidence suggests that alginates with longer storage time, such as Cavex Color Change, are more accurate than conventional alginates.

Diffusional analysis and textural properties of coated strawberries during osmotic dehydration treatment

BACKGROUND: The use of polysaccharide based edible coatings as a barrier against the solute entry of high caloric constituents, such as sucrose, is a suitable strategy to develop pro-healthy osmo-dehydrated products. OBJECTIVE: This work aims to study the effect of a calcium alginate film over the drying kinetics of strawberries during an osmotic dehydration (OD) treatment at 60°Brix, 4 h, 40°C (sucrose). Also, textural parameters were evaluated. METHODS: It was determined the changes in some selected physical properties, such as: moisture, total solid contents, one-dimensional shrinkage and texture, at 30 min steps during OD treatment. Besides, water and solid diffusion coefficients ( D e W and D e TS , respectively) were calculated by using the analytical solution of Fick’s equation. RESULTS: Diffusion coefficients for water and solids showed significant differences due to coating presence as an evidence of the barrier effect. Coated strawberry samples presented several changes after 2 h of OD treatment at the assayed conditions for most of the parameters evaluated. CONCLUSIONS: Alginate coating at the tested conditions acts as a barrier to sucrose influx and to water outflux until 2 and 3 h of OD treatment, respectively. Besides, a good textural quality for osmotically-dehydrated strawberries was obtained.

Glaciers in Xinjiang, China: Past Changes and Current Status

The Xinjiang Uyghur Autonomous Region of China is the largest arid region in Central Asia, and is heavily dependent on glacier melt in high mountains for water supplies. In this paper, glacier and climate changes in Xinjiang during the past decades were comprehensively discussed based on glacier inventory data, individual monitored glacier observations, recent publications, as well as meteorological records. The results show that glaciers have been in continuous mass loss and dimensional shrinkage since the 1960s, although there are spatial differences between mountains and sub-regions, and the significant temperature increase is the dominant controlling factor of glacier change. The mass loss of monitored glaciers in the Tien Shan has accelerated since the late 1990s, but has a slight slowing after 2010. Remote sensing results also show a more negative mass balance in the 2000s and mass loss slowing in the latest decade (2010s) in most regions. This needs further investigation on whether the slowing is general and continuing. In addition, glacier surging occurs more frequently in the Karakoram and Kunlun Mountains.

Is there a correlation between vestibular depth and shrinkage of free gingival graft: A descriptive-correlational study

Background: The purpose of the present study was to evaluate the correlation of vestibular depth (VD) with Free Gingival Graft (FGG) dimensional shrinkage.Methods: This study was a descriptive-correlational study which was performed on twenty patients with insufficient attached gingiva width (AGW). Under local anesthesia, a partial thickness bed with sub-marginal incision was created. An FGG was prepared from the palate and sutured to the prepared bed. Clinical parameters including VD, probing depth (PD), keratinized gingiva width (KGW), AGW, vertical graft dimension (VGD), horizontal graft dimension (HGD) and graft area (GA) were evaluated preoperatively and after one, three, and six months postoperatively. The distribution of data was normal. Repeated measures ANOVA, Repeated measures with covariance, Pearson correlation coefficient and linear regression were performed to analyze the data.Results: One patient was excluded from the study, therefore, the obtained data of 19 remaining patients were analyzed. Six months after FGG surgery, AGW and KGW raised to 6.15±1.01 mm and 7.55±1.1 mm, which were statistically significant (p <0.001). The shrinkage rate of HGD, VGD, and GA were 13%, 34%, 42% respectively after 6 months. The VD was increased 2.05 mm compared to baseline which was statistically significant (p<0.01). Pearson correlation coefficient showed that there was a statistically significant correlation between VGD shrinkage (r=-0.614, p=0.005) and GA shrinkage (r=-0.476, p=0.039) with VD. The correlation of Horizontal shrinkage with VD was not statistically significant (r=0.065, p=0.792).Conclusions: It was concluded that the shrinkage of FGG was influenced by VD and a negative moderate correlation was existed between VD and shrinkage of VGD and GA. Trial registration: This study was retrospectively registered by Iranian Registry of Clinical Trials (IRCT) with the number: IRCT20101204005305N18. Registered 22 September 2019. https://irct.ir/trial/41736

Predicting Leaf Trait Variability as a Functional Descriptor of the Effect of Climate Change in Three Perennial Grasses

Aims of the study: The most important trends of the current climate variability is the scarcity of rains that affects arid ecosystems. The aim of this study was to explore the variability of leaf functional traits by which grassland species survive and resist drought and to investigate the potential link between resource use efficiency and water scarcity resistance strategies of species. Methods: Three grasses (Cenchrus ciliaris (C4), Stipa parviflora and Stipa lagascae (C3)) were established in a randomized block consisting of eleven replications. The seedlings were kept under increasing levels of water stress. In addition to their functional leaf traits, the rate of water loss and dimensional shrinkage were also measured. Key Results: Thicker and denser leaves, with higher dry matter contents, low specific leaf area and great capacity of water retention are considered among the grasses’ strategies of dehydration avoidance. Significant differences between the means of the functional traits were obtained. Furthermore, strong correlations among leaf traits were also detected (Spearman’s r exceeding 0.8). Conclusions: The results provide evidence that the studied grasses respond differently to drought by exhibiting a range of interspecific functional strategies that may ameliorate the resilience of grassland species communities under extreme drought events.

Relationship between circulating levels of cortisol at slaughter and changes of some parameters of the camel meat during ageing

Relationship between serum levels of cortisol at slaughter and changes of some parameters of meat was investigated in 50 male camels, during ageing for 10 days at 4±1°C. Blood was sampled at slaughter to determine serum levels of cortisol and oblique abdominal external muscle was collected after slaughter to analyze pH, electrical conductivity (EC), drip loss (DL), cooked loss (CL), moisture, solids, ashes, protein total, calcium (Ca), phosphorus (Pi), magnesium (Mg), sodium (Na), potassium (K), catalase activiry (CATa), malondialdehyde (MDA), shrinkage, R-value and total haem pigment (THP) at days 0 (four hours postmortem), 5 and 10 of refrigerated storage. The camels were divided into 3 groups (Gr) with different serum levels of cortisol at slaughter (low, high and very high levels): Gr1 (13.07-67.9 ng/mL, n= 24), Gr2 (80.29-107.21 ng/mL, n= 7) and Gr3 (133.7-198.04 ng/mL, n= 19). Compared to Gr1, Gr2 and Gr3 had a significant (P<0.05) increase of pH, EC, DL, CL, THP, dimensional shrinkage and MDA, and a significant (P<0.05) decrease of CATa at the 5th and 10th postmortem days. However, the bleeding efficiency, moisture, ashes, R-value and levels of Ca, Pi, Na, K and total protein showed no significant differences between twoo cortisol groups. The antemortem circulating levels of cortisol were positively correlated with postmortem pH, EC, DL, CL, THP, dimensional shrinkage and MDA, and negatively correlated with CATa. The analysis of circulating cortisol at slaughtering may predict the quality and oxidant stress status of camel meat during postmortem cold storage.